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   33227篇
  免费   1370篇
  国内免费   8篇
  34605篇
  2020年   311篇
  2019年   439篇
  2018年   572篇
  2017年   598篇
  2016年   613篇
  2015年   432篇
  2014年   549篇
  2013年   2429篇
  2012年   992篇
  2011年   1046篇
  2010年   616篇
  2009年   627篇
  2008年   921篇
  2007年   894篇
  2006年   847篇
  2005年   758篇
  2004年   743篇
  2003年   676篇
  2002年   703篇
  2001年   1028篇
  2000年   935篇
  1999年   718篇
  1998年   394篇
  1997年   317篇
  1992年   556篇
  1991年   553篇
  1990年   532篇
  1989年   545篇
  1988年   536篇
  1987年   497篇
  1986年   527篇
  1985年   577篇
  1984年   460篇
  1983年   438篇
  1982年   360篇
  1981年   340篇
  1979年   532篇
  1978年   384篇
  1977年   319篇
  1976年   369篇
  1975年   441篇
  1974年   495篇
  1973年   509篇
  1972年   408篇
  1971年   383篇
  1970年   381篇
  1969年   409篇
  1968年   489篇
  1967年   421篇
  1966年   427篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
221.
Honeybees (Apis mellifera) were classically conditioned with odor as conditioned stimulus (CS), sucrose as unconditioned stimulus (US), and proboscis extension as response. The purpose of Experiment 1 (Ns = 26 and 27) was to look for facilitation of forward conditioning by CS-US overlap, but rapid conditioning without overlap left little room for improvement. In 2 further experiments, CS and US were simultaneous, and response to odor alone was measured in subsequent tests. In Experiment 2, a Simultaneous group (N = 25) responded more to the training odor than did an Unpaired control group (N = 25). In Experiment 3, a differentially conditioned Simultaneous group (N = 29) responded more to an odor paired with sucrose in training (S+) than to an odor presented alone (S-). The implications of the results for the problem of the role of amount of reward in honeybee learning are considered.  相似文献   
222.
223.
Adult age differences were explored on 3 short tests of the ability to generate and manipulate mental images. Age-related decrements were found in all 3 tests and were especially marked on the Clock Test. The tests are all reliable, as shown by test-retest reliability coefficients. Correlations also revealed that the Brooks Letter Test and the East-West Test appear to tap one common underlying ability, whereas the Clock Test measured a somewhat different ability. The East-West and Clock tests, in particular, may provide rapid and easily administered assessments of age-related changes in aspects of mental imagery.  相似文献   
224.
The authors used a correlated motion paradigm to investigate the effects of aging and gender on motion sensitivity. In 2 experiments with a total of 50 elderly and 50 young subjects, motion thresholds were significantly higher for elderly women. The correlated motion signal, which was embedded in random motion, may have been coherent to subjects in much the same way a form is in Witkin's Embedded Figures Test (EFT). In Experiment 2, EFT scores were obtained. A significant positive relationship between motion thresholds and EFT performance was found within each age group. Although gender-related perceptual style differences may contribute to motion perception effects, the authors argue that a common neural factor contributes to performance on both the EFT and the correlated motion task.  相似文献   
225.
The construct accessibility model (CAM) holds that constructs are most likely to influence behavior when they are accessible in memory. While the theory of reasoned action sees intention as an important determinant of behavior, the CAM predicts that the intention to act upon a given health behavior is not likely to be acted upon unless the intention is in an accessible state. Therefore, people who frequently talk about or think about using condoms are likely to have condom related constructs available and use them when needed. This paper reports findings from the pilot phase of a project to identify beliefs which influence condom use in Hispanic and African-American youth living in Detroit. 15 male and 15 female Hispanics and 17 male and 17 female African-Americans aged 15-21 years of mean and median age 18.5, were interviewed face-to-face in 1989 with the goal of identifying condom beliefs which may influence their condom use. 80-82% of male participants, 53% of Hispanic females, and 100% of Black females had experienced sexual intercourse, with age at first intercourse ranging between 13.1 and 16.5 years. 88% of Black women and 7% of Hispanic women were pregnant at the interview. Regarding participants' level of preventive knowledge, all but 1 recently immigrated Hispanic female knew HIV was transmitted by needles and sexual intercourse. 87% of Hispanics and 94% of African-Americans responded that condoms protect against AIDS, but only 13% of Hispanics and 47% of African-Americans knew that nonlatex condoms do not. Some participants expressed concern that condoms reduce sensitivity and/or break during intercourse. Controlling for sexual activity, 25% of Hispanic females, 83% of Hispanic males, 71% of African-American females, and 80% of African-American males had ever used a condom; no Hispanic and 14% of Blacks reported using them consistently in the 12 month period preceding the interview. With 100% of African-American males and 97% of Black females reporting thinking about using condoms compared to 80% of Hispanics, the study findings suggest that condom intentions are more accessible in African-Americans than among Hispanics.  相似文献   
226.
227.
Helms (1984) presented a model to explain the influence of Black and White racial identity development on counseling interactions. The purpose of this study was to examine her hypothesis that specific combinations of racial identity attitudes contribute to qualitatively different counseling process and outcome or relationship types.  相似文献   
228.
Catharine MacKinnon's investigation of the role of sexuality in the subordination of women is a logical culmination of radical feminist thought. If this is correct, the position of her work relative to radical feminism is analogous to the place Parmenides's work occupied in ancient Greek philosophy. Critics of MacKinnon's work have missed their target completely and must engage her work in a different way if feminist theory is to progress past its current stalemated malaise.  相似文献   
229.
230.
Neural networks can be used as a tool in the explanation of neuropsychological data. Using the Hebbian Learning Rule and other such principles as competition and modifiable interlevel feedback, researchers have successfully modeled a widely used neuropsychological test, the Wisconsin Card Sorting Test. One of these models is reviewed here and extended to a qualitative analysis of how verbal fluency might be modeled, which demonstrates the importance of accounting for the attentional components of both tests. Difficulties remain in programming sequential cognitive processes within a parallel distributed processing (PDP) framework and integrating exceedingly complex neuropsychological tests such as Proverbs. PDP neural network methodology offers neuropsychologists co-validation procedures within narrowly defined areas of reliability and validity.  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