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   38413篇
  免费   1420篇
  国内免费   11篇
  2018年   603篇
  2017年   557篇
  2016年   644篇
  2015年   465篇
  2014年   542篇
  2013年   3650篇
  2012年   963篇
  2011年   987篇
  2010年   635篇
  2009年   607篇
  2008年   938篇
  2007年   840篇
  2006年   794篇
  2005年   663篇
  2004年   643篇
  2003年   674篇
  2002年   641篇
  2001年   1212篇
  2000年   1189篇
  1999年   891篇
  1998年   416篇
  1996年   507篇
  1995年   478篇
  1994年   477篇
  1993年   452篇
  1992年   925篇
  1991年   835篇
  1990年   818篇
  1989年   731篇
  1988年   730篇
  1987年   717篇
  1986年   704篇
  1985年   704篇
  1984年   617篇
  1983年   514篇
  1982年   416篇
  1981年   438篇
  1980年   408篇
  1979年   595篇
  1978年   448篇
  1975年   555篇
  1974年   545篇
  1973年   605篇
  1972年   574篇
  1971年   511篇
  1970年   444篇
  1969年   434篇
  1968年   548篇
  1967年   468篇
  1966年   450篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
182.
183.
Context and structure in conceptual combination   总被引:8,自引:0,他引:8  
  相似文献   
184.
Two modes of learning for interactive tasks   总被引:5,自引:0,他引:5  
N A Hayes  D E Broadbent 《Cognition》1988,28(3):249-276
  相似文献   
185.
The care of the patient with cancer requires the development not only of a medical plan, but an ethical plan as well. This plan should integrate the physician's and the patient's perceptions of medical and ethical propriety. Jewish biomedical ethical principles are based on the teaching of the Old Testament and its various interpretations. In this paper, I discuss how these principles can be used to help guide the physician caring for the patient with cancer. Other ethical systems could be applied in a similar fashion.  相似文献   
186.
187.
The precaution adoption process   总被引:47,自引:0,他引:47  
This article presents a critique of current models of preventive behavior. It discusses a variety of factors that are usually overlooked-including the appearance of costs and benefits over time, the role of cues to action, the problem of competing life demands, and the ways that actual decision behavior differs from the rational ideal implicit in expectancy-value and utility theories. Such considerations suggest that the adoption of new precautions should be viewed as a dynamic process with many determinants. The framework of a model that is able to accommodate these additional factors is described. This alternative model portrays the precaution adoption process as an orderly sequence of qualitatively different cognitive stages. Data illustrating a few of the suggestions made in the article are presented, and implications for prevention programs are discussed.  相似文献   
188.
Twenty-six suicide attempters, 9 to 18 years of age, were compared with 725 nonattempters on measures of school achievement, educational goals, socioeconomic status, and depression. As has been found in studies using clinical samples, suicide attempters in our communitybased sample had significantly lower school achievement than nonattempters. The relationship between attempted suicide and low school achievement seemed to be explained by the effects of depression. Lower-SES youth tended to be more likely to attempt suicide than higher-SES youths. However, SES appeared to have little effect on the relationship between attempted suicide and school achievement. Results also suggest that children of mothers with low educational goals for them may be more at risk for attempted suicide than youths whose mothers have higher educational goals for their children.This research was supported by the National Institute of Mental Health, Grant No. MH36971.  相似文献   
189.
The finding that there are maturational differences between the ability to learn and to perform a task requiring young Wistar rats to inhibit a response was examined. Using an operant task, different from that employed in the previous studies, it was established that the finding was not task specific. The relative contribution of different periods in the early training stage to later savings in learning was also examined. It was confirmed that there is an early performance deficit by weanling rats on tasks requiring them to inhibit a previously learned response in the presence of a discriminative cue. Rats given early training on the task during this period of performance deficit nevertheless showed significant savings in later learning of the task, indicating that they had learned as much in that stage as they would have if given the same training at an age when performance is at the adult level. It was revealed that despite age-related differences in performance it was not so much the age at which early training took place as the amount of training given that affected later savings. The results are discussed in light of evidence of similar differences between the learning and performance of discrimination tasks exhibited by young children.  相似文献   
190.
The modulation of attacks, genital sniffs, and mounts in male SJL/J mice by ovarian-dependent urogenital substances in the urine voided by estrous females was examined. Urogenital substances were applied onto the external urogenital areas of ovariectomized mice. When compared with urine voided by estrous females, which stimulated genital sniffing, mounting, and reduced aggression, bladder urine was ineffective. Genital sniffing and mounting was stimulated by estradiol-17 beta, vaginal fluids, and preputial extract. Aggression was reduced by estradiol-17 beta, urethral catheterized urine, and vaginal fluids. Preputialectomy reduced, but did not eliminate, urinary stimulation of genital sniffing and mounting. Preputial extract stimulated aggression. Urogenital substances from ovariectomized females were ineffective in reducing attacks and stimulating genital sniffs and mounts. It was concluded that the ovarian-dependent chemosignals in the urine voided by estrous females are contributed by the urethra, vagina, and preputial gland, perhaps in part through the excretion of unconjugated estrogens.  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