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   6275篇
  免费   269篇
  国内免费   2篇
  2020年   73篇
  2019年   97篇
  2018年   122篇
  2017年   123篇
  2016年   125篇
  2015年   109篇
  2014年   118篇
  2013年   575篇
  2012年   226篇
  2011年   231篇
  2010年   146篇
  2009年   133篇
  2008年   161篇
  2007年   153篇
  2006年   149篇
  2005年   116篇
  2004年   116篇
  2003年   116篇
  2002年   120篇
  2001年   204篇
  2000年   194篇
  1999年   156篇
  1998年   56篇
  1993年   53篇
  1992年   114篇
  1991年   112篇
  1990年   109篇
  1989年   94篇
  1988年   90篇
  1987年   93篇
  1986年   102篇
  1985年   104篇
  1984年   92篇
  1983年   71篇
  1981年   55篇
  1980年   56篇
  1979年   109篇
  1978年   57篇
  1977年   50篇
  1976年   62篇
  1975年   77篇
  1974年   102篇
  1973年   91篇
  1972年   75篇
  1971年   79篇
  1970年   76篇
  1969年   82篇
  1968年   75篇
  1967年   89篇
  1966年   51篇
排序方式: 共有6546条查询结果,搜索用时 31 毫秒
991.
High-resolution electron microscopy (HREM) at the atomic scale has been applied to study the edge dislocation redistribution between interfaces in Ge/Ge0.5Si0.5/Si(0?0?1) heterostructures. Our results provide a direct explanation that plastic relaxation of the GeSi buffer layer proceeds owing to motion of Lomer-type dislocation complexes consisting of a pair of complementary 60° dislocations with the ends of the {1?1?1} extra planes being located at a distance of ~2–12 interplanar spacings from each other. It is demonstrated that edge dislocations belonging to the upper and lower interfaces become arranged one under the other and dislocation walls are formed. The distributions of tension and compression in the [0?0?1] direction between two edge dislocations, obtained by processing the HREM image, testify to superposition of strain fields.  相似文献   
992.
It seems uncontroversial that Dalton wrongly believed that atoms are indivisible. However, the correct analysis of Dalton’s belief and the way it relates to contemporary beliefs about atoms is, on closer inspection, far from straightforward. In this paper, I introduce four features that any candidate analysis is plausibly bound to respect. I argue that theories that individuate concepts at the level of understanding are doomed to fail in this endeavor. I formally sketch an alternative and suggest that cases such as the one presented provide support for the claim that the genuine source for concept individuation is public sharable thought.  相似文献   
993.
994.
995.
Research on eye witness memory in older children and adults revealed that verbally describing unfamiliar faces impairs later recognition of these faces, known as the “verbal overshadowing effect”. The aim of this study was to investigate whether a verbal overshadowing effect occurs in 4- to 6-year olds, too, and whether visualization (i.e., drawing the seen face) might elicit a visual overshadowing effect. Instead of a verbal overshadowing effect, a verbal facilitation effect was revealed with verbal intelligence being a significant predictor for recognition accuracy in the verbalization group but not in the control group. No effect of visualization was observed on recognition accuracy. Potential explanations for the results are discussed.  相似文献   
996.
997.
998.
We analysed, under laboratory test conditions, how German cockroach larvae oriented their outgoing foraging trip from their shelter. Our results stressed the importance of external factors, like availability and spatial distribution of food sources, in the choice of a foraging strategy within their home range. When food sources were randomly distributed, larvae adopted a random food search strategy. When food distribution was spatially predictable and reliable, cockroaches were able to relate the presence of food with a landmark during a 3-day training period and to develop an oriented search strategy. Cockroaches were able to associate learned spatial information about their home range to the presence of food resources and then to improve their foraging efficiency. However, conflict experiments revealed that detection of food odour overrode learned landmark cues. Received: 16 October 1999 / Accepted after revision: 18 July 2000  相似文献   
999.
Grant  John  Subrahmanian  V. S. 《Synthese》2000,125(1-2):121-132
The study of paraconsistent logic as a branch of mathematics and logic has been pioneered by Newton da Costa. With the growing advent of distributed and often inconsistent databases over the last ten years, there has been growing interest in paraconsistency amongst researchers in databases and knowledge bases. In this paper, we provide a brief survey of work in paraconsistent databases and knowledge bases affected by Newton da Costa's important and lasting contributions to the field.  相似文献   
1000.
The current study examined the relationship between childhood anxiety and threat perception abnormalities. Children (N = 105) were exposed to stories reflecting three types of anxiety: social anxiety, separation anxiety, and generalized anxiety. From children's reactions to the stories, a number of threat perception indices were derived. Children's level of anxiety was assessed by means of questionnaires and a structured diagnostic interview. Results indicated that high levels of anxiety, as measured by questionnaires and interview, were accompanied by a high frequency of threat perception, high ratings of threat, a high frequency of threatening interpretations, high levels of negative feelings and cognitions, and an early detection of threat. Furthermore, results seemed to suggest that threat perception abnormalities were mediated by children's general level of anxiety rather than by levels of specific anxiety symptoms.  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