首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2522篇
  免费   194篇
  国内免费   286篇
  3002篇
  2024年   10篇
  2023年   58篇
  2022年   48篇
  2021年   82篇
  2020年   147篇
  2019年   141篇
  2018年   146篇
  2017年   145篇
  2016年   139篇
  2015年   99篇
  2014年   114篇
  2013年   361篇
  2012年   72篇
  2011年   113篇
  2010年   65篇
  2009年   106篇
  2008年   90篇
  2007年   102篇
  2006年   90篇
  2005年   102篇
  2004年   102篇
  2003年   88篇
  2002年   67篇
  2001年   62篇
  2000年   62篇
  1999年   36篇
  1998年   37篇
  1997年   31篇
  1996年   25篇
  1995年   36篇
  1994年   24篇
  1993年   6篇
  1992年   9篇
  1991年   14篇
  1990年   9篇
  1989年   12篇
  1988年   9篇
  1987年   12篇
  1986年   7篇
  1985年   11篇
  1984年   17篇
  1983年   9篇
  1982年   16篇
  1981年   13篇
  1980年   11篇
  1979年   14篇
  1977年   7篇
  1976年   6篇
  1975年   9篇
  1974年   5篇
排序方式: 共有3002条查询结果,搜索用时 15 毫秒
91.
Electrical stimulation of the region of the lateral hypothalamus produced a consistent form of quiet-biting attack behavior in cats. In one series of experiments, cats, implanted with electrodes from which attack had been elicited, were anesthetized and then were injected with a bolus of 14C-2-deoxyglucose at the same time as electrical stimulation was delivered through the attack electrodes. Brains prepared for X-ray autoradiography revealed that lateral hypothalamic stimulation activated the classical medial forebrain bundle pathway supplying the septal region, diagonal band, lateral preoptic area, and ventral tegmental region. Stimulation of quiet-attack sites in perifornical hypothalamus resulted in the activation of a much more extensive projection system which included the central and lateral tegmental fields of the midbrain and pons, and central gray region, as well as the structures described above. In a second series of experiments, 3H-leucine was placed into the region of the electrode tip from which attack was elicited in order to identify more precisely the pathways arising from that site. In general, tritiated amino acid radioautography replicated the 14C-2-deoxyglucose findings. In addition, the amino acid radioautographic data revealed the presence of extensive projections from perifornical hypothalamus to such pontine structures as the nucleus locus coeruleus, motor nucleus of NV , and the lateral pontine tegmental field. The functional connections between the lateral hypothalamic “attack region” and lateral preoptic zone were also confirmed by electrophysiological methods.  相似文献   
92.
A new multiobjective linear programming (MOLP) algorithm is presented. The algorithm uses a variant of Karmarkar's interior-point algorithm known as the affine-scaling primal algorithm. Using this single-objective algorithm, interior search directions are generated and used to provide an approximation to the gradient of the (implicitly known) utility function. The approximation is guided by assessing locally relevant preference information for the various interior directions through interaction with a decision maker (DM). The resulting algorithm is an interactive approach that makes its progress towards the solution through the interior of the constraints polytope.  相似文献   
93.
The automatic skeletal motor responses of 20 male and 20 female student subjects (aged 20–36) receiving a painful stimulation (electric shock) were studied by examining voluntary concomitant extensions and flexions of the arm. These movements were either of long duration, allowing for an on-line control of their execution or, of short duration, requiring extensive pre-programming. Subjects were instructed either to push or to pull a lever upon receipt of an acoustic signal, which was paired or unpaired with an electric shock. Latencies for long duration movements (regardless of direction) were reduced by reception of painful stimulation. Latencies of short duration extensions and flexions were respectively reduced and increased by painful stimulation. Latencies of short duration movements were larger for females than males, regardless of movement direction. These data suggest that painful stimulation elicits automatic movements which affect programming of the termination of simultaneous voluntary movements. Implications of these findings for the study of aggressive behavior are discussed. © 1994 Wiley-Liss, Inc.  相似文献   
94.
Abstract

Optic flow (OF) has been utilized to investigate the sensory integration of visual stimuli during postural control. It is little known how the OF speed affects the aging brain during the sensory integration process of postural control. This study was to examine the effect of OF speeds on the brain activation using functional near-infrared spectroscopy (fNIRS) and postural sway between younger and older adults. Eleven healthy younger adults (5M/6F, age 22?±?1-year-old) and ten healthy older adults (4M/6F, age 71?±?5-year-old) participated in this study. A virtual reality headset was used to provide the OF stimulus at different speeds. A forceplate was used to record the center-of-pressure to compute the amplitude of postural sway (peak-to-peak). Compared with younger adults, older adults showed significantly increased activation in the OF speed of 10?m/s and decreased activation in the OF speed of 20?m/s in the left dorsolateral prefrontal cortex. Older adults also showed decreased activation in the left temporoparietal region (VEST) in the OF speed of 20?m/s. A significant difference in peak-to-peak was found between groups. Our results indicated that age might be associated with the ability to process fast OF stimulation.  相似文献   
95.
Abstract

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) has been demonstrated to modulate the motor performance of both healthy individuals and patients with neuromuscular disorders. However, the effect of tDCS on motor control of multiple muscles, which is a prerequisite to change in motor performance, is currently unknown. Using dimensionality reduction analysis, we investigated whether bilateral tDCS over M1 modulates the coordinated activity of 12 muscles. Fifteen healthy men participated in this randomized, double-blind crossover study. Each participant received a 20-min sham and 2-mA stimulation bilaterally over M1 (anode on the right M1 and cathode on the left M1), with a minimum washout period of 4?days. Muscle activation and end-point kinematics were evaluated during a task where participants reached out to a marked target with non-dominant hand as fast as possible, before and immediately after tDCS application. We found decreased similarity in motor modularity and significant changes in muscle activation in a specific motor module, particularly when reaching out to a target placed within arm’s length and improved smoothness index of movement only following 2-mA stimulation. These findings indicate that clinicians and researchers need to consider the simultaneous effect of bilateral tDCS over M1 on multiple muscles when they establish tDCS protocol to change in motor performance of patients with neuromuscular deficits.  相似文献   
96.
The Borg centiMax Scale, is a psychophysically composed general intensity ratio scale, which could enable more precise inter- and intraindividual comparisons of the intensity of depressive symptoms. In the present study, the properties of the centiMax scale were examined in 38 patients with clinical depression and 109 students. Additionally, preliminary centiMax cut-off scores for mild, moderate and severe depression were estimated. The psychometric properties of the centiMax were found to be satisfactory regarding internal consistency, convergent, discriminative and predictive validity. Moreover, the centiMax was demonstrated to provide meaningful comparisons of symptom intensity, which makes it possible to evaluate the relative importance of individual symptoms in a profile and make more precise comparisons within and between individuals. With regard to intraindividual comparisons, patients rated , for example, the intensity of feeling “guilt” twice as strong as feelings of “being punished,” and the intensity of “loss of pleasure” almost three times as strong as “being punished.” With regard to interindividual comparisons, patients rated e.g., the intensity of “being punished” as 12 times stronger than controls, and the intensity of “worthlessness” about nine times stronger. In conclusion, the centiMax was shown to be reliable and valid for assessing depressive symptoms. The centiMax with level anchored ratio data, appears to be highly advantageous as it permits rather precise values of symptom intensity for intra- and interindividual comparisons that could be useful in the diagnostic process and in treatment planning.  相似文献   
97.
A child's emotional and social development depends on the parents’ provision of optimal support. Many parents with perinatal distress experience difficulties in mastering parenthood and seek help from professionals within primary healthcare. A clinical project was launched in Stockholm, where psychodynamic psychotherapists provided short-term consultations at Child Health Centers. This study qualitatively explored parents’ experiences of perinatal distress and of receiving help by nurses and therapists in the project. Thirteen parents were interviewed, and their responses were analyzed with a hermeneutical method. Three main themes crystallized; accessibility of psychological help and detection of emotional problems; experiences of therapy at the Child Health Center; and the therapists’ technique. Parents were also clustered into three so-called ideal types: the insecure; parents in crisis; and parents with lifelong psychological problems. Parents experienced obstacles in accessing psychological care within primary healthcare. Psychotherapists with a holistic family perspective and who managed to oscillate between insight-promoting and supportive interventions were especially appreciated. Patient categories who benefitted from insight promotion and support, respectively, were identified.  相似文献   
98.
Attention-Deficit/Hyperactivity Disorder (ADHD) is related to suboptimal decision making in experimental tasks and to real-life risk-taking behavior (RTB) such as substance abuse and unsafe traffic conduct. In this preregistered study, we tested whether these associations are mediated by need for cognition—the extent to which one tends towards, and enjoys, analytical thought. In a large sample of young adults (N = 463, Mage = 19.7 years), we tested whether need for cognition mediated the association between self-reported ADHD symptoms on the one hand and decision-making strategy complexity on an experimental gambling task and self-reported real-life RTB on the other hand. Preregistered confirmatory analyses indicated first that ADHD symptoms were positively associated with real-life RTB, but the association was not mediated by need for cognition. Second, ADHD symptoms were not related to decision-making strategy complexity, and need for cognition was not a significant mediator. Explorative analyses revealed that (a) need for cognition was associated with higher decision-making accuracy and slower reaction time; (b) need for cognition was related to inattentive but not to hyperactive/impulsive ADHD symptoms; (c) need for cognition was associated with health-related RTB but not interpersonal RTB; and (4) only the association between inattention and health-related RTB was mediated by need for cognition. We conclude that need for cognition is not a mediator in the association between ADHD symptoms and RTB. Additionally, we conclude that neither ADHD symptoms nor need for cognition predict decision-making strategy complexity. Implications for both future research and clinical practice are discussed.  相似文献   
99.
《Médecine & Droit》2020,2020(160):6-9
Announcing a death is always a delicate moment for close familial members but also for caregivers. Law gives some precisions about how this information must be delivered. Recently the state council judged that the lack of empathy from caregivers and the late of the death announcement can create a damage. This judgement gives more precisions about how a death announcement must be in a hospital. This topic is pretty similar with the information which must be given to close familial members about organ donation. This latter is definitely more exceptional and the procedure is a way more regulated. There are much rules which explain how this information must be delivered.  相似文献   
100.
《Médecine & Droit》2020,2020(164):129-133
Due to the progress of science and the stakes of inquiry and sentence, the DNA analysis is subject of a substantial development within the area of criminal procedure. However, the DNA is by no means a perfect evidence and it faces scientific, ethic and legal limits which result in reconsidering the balance between the stakes of punishment and the protection of Fundamental Freedoms.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号