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   19486篇
  免费   801篇
  国内免费   4篇
  2021年   129篇
  2020年   243篇
  2019年   289篇
  2018年   385篇
  2017年   436篇
  2016年   428篇
  2015年   353篇
  2014年   433篇
  2013年   2265篇
  2012年   720篇
  2011年   769篇
  2010年   474篇
  2009年   522篇
  2008年   767篇
  2007年   715篇
  2006年   675篇
  2005年   684篇
  2004年   674篇
  2003年   634篇
  2002年   664篇
  2001年   324篇
  2000年   279篇
  1999年   308篇
  1998年   331篇
  1997年   284篇
  1996年   244篇
  1995年   263篇
  1994年   235篇
  1993年   247篇
  1992年   234篇
  1991年   206篇
  1990年   195篇
  1989年   184篇
  1988年   178篇
  1987年   181篇
  1986年   170篇
  1985年   219篇
  1984年   254篇
  1983年   253篇
  1982年   246篇
  1981年   232篇
  1980年   200篇
  1979年   173篇
  1978年   237篇
  1977年   208篇
  1976年   219篇
  1975年   196篇
  1974年   208篇
  1973年   147篇
  1972年   110篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
Genetic counselors have participated in the Michigan Newborn Screening Program on a contractual basis since 1988. Their role includes newborn screening education and training, newborn nursery site visits, and monitoring newborn screening in hospitals. Their impact has been to improve the quality of newborn screening services by reducing errors and increasing completion of data fields on newborn screening cards, improving hospital nursery cooperation and problem solving, and enhancing health department response to specific problems.  相似文献   
122.
Retrospective and prospective reports of the onset of disruptive child behaviors were analyzed in a sample of clinic-referred boys. The younger boys (ages 7–9 years), compared with the older boys (ages 10–12 years), showed the highest level of disruptive behavior and, judging from mothers' reports, had the fastest progression of onsets from less serious to more serious problem behaviors. Despite some overlap, developmental sequences in problem behavior within the domains of hyperactivity/inattention, oppositional behavior, and conduct problems were similar across the two age groups. This was also the case for developmental sequences of overt or confrontive problem behaviors and covert or concealing conduct problems. Sequences of the onset of oppositional behavior and conduct problems were validated through prospective data, based on the information from mothers, teachers, and boys themselves. The implications of the findings are discussed for the formulation of developmental pathways of behavior and the analysis of causal factors.  相似文献   
123.
124.
The negative-tilt preparation that has been reported since the late seventies is a specific form of Pavlovian conditioning that is of scientific interest and has potential applications. In this paper I reflect on the usefulness, to the development of this preparation, of two approaches to Pavlovian conditioning. One approach is the older S-R learning, stimulus-substitution paradigm exemplified by learning texts of the sixties. The other is the modern, Tolman-like view, according to which the phenomenon of Pavlovian conditioning is “now described as the learning of relations among events so as to allow the organism to represent its environment.” The three assumptions encapsulated by this approach are: (a) that only CS-US contingency relations are learned; (b) that teleological modes of explanations are adequate; (c) that the representational theory of knowledge is sound. Concerning Pavlovian conditioning in general, questions been raised in the literature for all three assumptions; they have not been adequately answered. Regarding the specific problem of developing the human Pavlovian heart-ratedecelerative conditioning with negative tilt as the US, I suggest that the cognitive approach has been much less helpful than the older, S-R, stimulus-substitution paradigm. Nevertheless, other literature clearly indicates that the cognitive, S-S approach has generated considerable interest and research, especially in preparations like the conditioned emotional response (CER), which are CS-IR ones in the sense that the effects on the CR are assessed indirectly through measuring an indicator or instrumental response (IR). Finally, even in CS-CR preparations like human GSR conditioning, it is important to study the cognitive, S-S learning process through using such dependent variables as continuously assessed subjective CS-US contingency.  相似文献   
125.
Working in the fragment of Martin-Löfs extensional type theory [12] which has products (but not sums) of dependent types, we consider two additional assumptions: firstly, that there are (strong) equality types; and secondly, that there is a type which is universal in the sense that terms of that type name all types, up to isomorphism. For such a type theory, we give a version of Russell's paradox showing that each type possesses a closed term and (hence) that all terms of each type are provably equal. We consider the kind of category theoretic structure which corresponds to this kind of type theory and obtain a categorical version of the paradox. A special case of this result is the degeneracy of a locally cartesian closed category with a morphism which is generic in the sense that every other morphism in the category can be obtained from it via pullback.The financial support of the Royal Society in London is gratefully acknowledged.  相似文献   
126.
Two experiments were conducted to examine the hypothesized differential effectiveness of two attentional focusing strategies in pain perception. In the first experiment, subjects (72 male college students) rated their levels of pain after being exposed to either low- or high-intensity pressure stimulation for 75 s. Subjects were instructed to use either an external or internal focus of attention during the pain induction. Results revealed that external focusing was more effective for coping than internal focusing across both levels of stimulus intensity. The second experiment was a replication of the first, and featured bolstered internal focusing and stimulus intensity manipulations. Results showed that high-intensity stimulation produced higher pain ratings than did low-intensity stimulation for subjects in the internal focusing conditions, but not for those in the external focusing conditions. The findings support the power of distraction strategies for dealing with short-term pain with a rapid onset. Theoretical implications are discussed.The authors thank Darwyn E. Linder and Daniel M. Landers for their help in development of this research. The authors are also indebted to Sarah Colley, Jona Davis, Nanci Neuberger, and Rebecca Roberts for their assistance in data collection.  相似文献   
127.
Established results on latent variable models are applied to the study of the validity of a psychological test. When the test predicts a criterion by measuring a unidimensional latent construct, not only must the total score predict the criterion, but the joint distribution of criterion scores and item responses must exhibit a certain pattern. The presence of this population pattern may be tested with sample data using the stratified Wilcoxon rank sum test. Often, criterion information is available only for selected examinees, for instance, those who are admitted or hired. Three cases are discussed: (i) selection at random, (ii) selection based on the current test, and (iii) selection based on other measures of the latent construct. Discriminant validity is also discussed.This work was supported in part by Grant SES-87-01890 from the Measurement Methods and Data Improvement Program of the U.S. National Science Foundation.  相似文献   
128.
129.
130.
Three experiments were designed to investigate the influence of initial recall on memory by assessing delayed recall after different immediate cued-recall tests. In all experiments, subjects performed semantic and phonemic encoding tasks on a word list. The subjects then received a cued-recall test that cued the target using the same word as the context word in the encoding task, a test that cued the target with a word from the same level at which the target was encoded, a test that cued the target with a cue from a different level at which the target was encoded, or no immediate-recall test. One day later, the subjects performed a final cued-recall test in which the type of cue (semantic or phonemic) was varied. Consistently, delayed recall was facilitated primarily when the cue on the immediate test was from the same level as the cue on the delayed test. This pattern of facilitation suggests that immediate cued-recall produces an elaboration of an existing memory representation that is closely tied to the type of cue used on the immediate test.  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