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   44485篇
  免费   1103篇
  国内免费   15篇
  2020年   318篇
  2019年   343篇
  2018年   3871篇
  2017年   3188篇
  2016年   2675篇
  2015年   541篇
  2014年   546篇
  2013年   2016篇
  2012年   1392篇
  2011年   3156篇
  2010年   2888篇
  2009年   1989篇
  2008年   2415篇
  2007年   2853篇
  2006年   720篇
  2005年   817篇
  2004年   758篇
  2003年   695篇
  2002年   588篇
  2001年   865篇
  2000年   883篇
  1999年   641篇
  1998年   302篇
  1997年   275篇
  1996年   230篇
  1995年   217篇
  1993年   215篇
  1992年   494篇
  1991年   431篇
  1990年   500篇
  1989年   417篇
  1988年   390篇
  1987年   375篇
  1986年   392篇
  1985年   449篇
  1984年   346篇
  1983年   292篇
  1982年   225篇
  1979年   327篇
  1978年   260篇
  1975年   299篇
  1974年   347篇
  1973年   350篇
  1972年   274篇
  1971年   242篇
  1970年   208篇
  1969年   229篇
  1968年   288篇
  1967年   252篇
  1966年   273篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
An injection olfactometer for human psychophysical experiments is described. The olfactometer is capable of presenting, either mono- or birhinally, single odorants and binary mixtures. The pulse form of the olfactory stimulus at the exit of the olfactometer approaches a rectangular form, which makes the olfactometer well suited for olfactory reaction time measurements. Since stimulation periods are independent of the subject’s inhalation, time-intensity measurements over prolonged periods of time are possible as well. In the second part of this paper, a new technique is described for the measurement of the stimulus pulse form at the exit of the olfactometer.  相似文献   
992.
Congenital bilateral absence of the vas deferens (CBAVD) occurs in approximately 1.3% of infertile males and is thought to be, in most cases, a primarily genital form of cystic fibrosis (CF). Fourteen males with CBAVD considering microsurgical sperm aspiration from the epididymis (MESA) and in vitro fertilization were seen for genetic counseling and screening for CF. To retrospectively evaluate these patients' perceptions of the counseling and screening information, we conducted structured telephone interviews to assess their recall of information about CF and its impact on their health concerns and reproductive plans. We found that, as the health implications of CF are abstract and not as important to patients as the diagnosis of CBAVD itself, patients tend to view their CF status primarily in terms of their reproductive potential. Retrospective analysis afforded us an opportunity to identify the psychosocial issues of most concern to this unique patient population.  相似文献   
993.
We investigated the ability of subjects to discriminate sugars with a whole-mouth forced-choice paradigm, in which a standard solution was compared with a test solution of varied concentration. Discrimination probabilities were U-shaped functions of test concentration: for 6 subjects and pairwise combinations of fructose, glucose, and sucrose, discriminability always declined to chance over a narrow range of test concentrations. At concentrations ≦ 100 mM, maltose was indiscriminable from fructose but discriminable at higher concentrations for 4 subjects. By analogy with themonochromacy of night vision, whereby any two lights are indiscriminable when their relative intensities are suitably adjusted, we call the gustatory indiscriminability of these sugarsmonogeusia. The simplest account of monogeusia is that all information about the indiscriminable sugars is represented by a single neural signal that varies only in magnitude. The discriminability of maltose from the other sugars at higher concentrations is consistent with the hypothesis that maltose also activates a second gustatory code.  相似文献   
994.
During linear translation through a stationary environment, the pattern of optical flow generated on each retina is symmetrical when the head is aligned with the heading, but during lateral gaze the optical flow is asymmetric. We assessed whether human subjects could use the magnitude of this asymmetry to determine the direction of heading during passive translation through a 3-D environment. When allowed to move their heads in order to look in the direction of self-motion, subjects indicated their heading precisely and accurately. When the head was locked in alignment with the misaligned body, and gaze adjustments were not allowed, responses were quite precise, but showed a large bias which increased with increasing heading angle.  相似文献   
995.
Koss  Mary P.  Leonard  Kenneth E.  Beezley  Dana A.  Oros  Cheryl J. 《Sex roles》1985,12(9-10):981-992
Sex Roles - Rape is an underreported and underconvicted crime. Therefore, many highly sexually aggressive men are missed by research employing judicial identification for sample selection. The...  相似文献   
996.
The purpose of this paper is to review the necessary components of a comprehensive group therapy program. The balancing between the didactic and the experiential portions, and an analysis of the selection criteria, along with the rationale for a particular sequencing of elements in the curriculum, are discussed. A line between supervision and personal therapy is drawn. The author describes the milieu necessary for a successful training program to evolve and makes suggestions for improvements. The various experiential aspects of training are presented and critically evaluated. The training situation is examined from the point of view of the faculty, the trainee and the patients involved. The author marshalls evidence indicating that personal group psychotherapy in a patient group is the preferred form for most trainees for the experiential part of the program. The paper concludes that the sharing and cohesiveness of training philosophies and methods by the faculty is a prerequisite to the success of any training program.  相似文献   
997.
The current investigation examined the degree to which judges' ratings of skill, anxiety, and attractiveness are influenced by the responsivity of the confederate. High-, medium-, and low-skilled subject-pool groupings, as well as self-referred clinical groups, were exposed to either a moderately or a minimally responsive confederate. Results indicated that subjects were rated as more skillful when interacting with a moderately responsive confederate than when interacting with a minimally responsive confederate. Further, there was a groups × condition interaction for anxiety ratings such that both the high- and the medium-skilled groups appeared more anxious under the minimal condition, whereas the low-skilled and self-referred groups did not. Self-referred subjects received significantly lower attractiveness ratings than did the high- or medium-skilled groups. Implications of these results and future directions for research are discussed.This research is based on a M.S. thesis carried out by the first author under direction of the second author.  相似文献   
998.
The present study investigated the validity of an inpatient pain behavior rating scale modified for outpatient use. A series of 43 consecutive outpatients referred for evaluation of chronic pain was examined using the Pain Behavior Scale (PBS) and other psychometric instruments. Analyses revealed significantly higher Pain Behavior Scale scores for low back and multiple pain-site groups. The results also indicated a high degree of internal consistency of the scale. A multiple regression analysis, predicting observed pain behavior from reported pain behavior, indicated that decreased activity accounted for 32% of the variance in the PBS score. A similar regression for pain experience found that the pain level and the sensory scale score on the McGill Pain Questionnaire accounted for 39% of the PBS variance. Psychological characteristics including disease conviction, self-control, depression, and anxiety explained 45% of the variability in the PBS score. Thus, the scale is related to pain intensity, interference with activities, and a variety of psychological characteristics. The scale provides a measure of observable pain behavior that is also relatively independent of these clinical data sources. The Pain Behavior Scale as modified for outpatient use provides a brief index of pain behavior with potential use in the comprehensive evaluation of the pain patient.  相似文献   
999.
1000.
Cornell University Medical College, Westchester Division, The New York Hospital, White Plains, New York It is well established that there is a complex timekeeping mechanism in the human brain. This mechanism is associated with a variety of physiological and psychological rhythms having a period of about a day, and thus referred to as circadian rhythms. The circadian system has recently been modeled in terms of two underlying oscillators, one much more resistant to changes in routine than the other. These oscillators are considered to be endogenous, that is, internal to the organism, and not reliant for their existence upon changes in the person’s environment or general behavior. They thus continue to run even when the sleep/wake cycle is suspended, as in sustained operations. Thus, by their very nature, sustained operations require the individual to override the inputs that are coming from his or her circadian system (especially the indication that sleep is required). The aim of this paper is to provide a background to the area of circadian rhythms research, including a section on the methodology, so that the impact of the circadian system on sustained operations can be better understood.  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