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   17645篇
  免费   38篇
  国内免费   75篇
系统科学   66篇
丛书文集   173篇
教育与普及   69篇
理论与方法论   66篇
现状及发展   7982篇
研究方法   752篇
综合类   8486篇
自然研究   164篇
  2012年   232篇
  2011年   389篇
  2009年   105篇
  2008年   295篇
  2007年   327篇
  2006年   311篇
  2005年   324篇
  2004年   346篇
  2003年   313篇
  2002年   306篇
  2001年   489篇
  2000年   513篇
  1999年   358篇
  1994年   305篇
  1992年   285篇
  1991年   231篇
  1990年   282篇
  1989年   258篇
  1988年   271篇
  1987年   295篇
  1986年   303篇
  1985年   361篇
  1984年   245篇
  1983年   263篇
  1982年   216篇
  1981年   211篇
  1980年   251篇
  1979年   521篇
  1978年   446篇
  1977年   400篇
  1976年   324篇
  1975年   391篇
  1974年   479篇
  1973年   433篇
  1972年   446篇
  1971年   576篇
  1970年   616篇
  1969年   545篇
  1968年   542篇
  1967年   469篇
  1966年   415篇
  1965年   302篇
  1964年   140篇
  1959年   168篇
  1958年   324篇
  1957年   256篇
  1956年   205篇
  1955年   201篇
  1954年   193篇
  1948年   169篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
String theorists are certain that they are practicing physicists. Yet, some of their recent critics deny this. This paper argues that this conflict is really about who holds authority in making rational judgment in theoretical physics. At bottom, the conflict centers on the question: who is a proper physicist? To illustrate and understand the differing opinions about proper practice and identity, we discuss different appreciations of epistemic virtues and explanation among string theorists and their critics, and how these have been sourced in accounts of Einstein's biography. Just as Einstein is claimed by both sides, historiography offers examples of both successful and unsuccessful non-empirical science. History of science also teaches that times of conflict are often times of innovation, in which novel scholarly identities may come into being. At the same time, since the contributions of Thomas Kuhn historians have developed a critical attitude towards formal attempts and methodological recipes for epistemic demarcation and justification of scientific practice. These are now, however, being considered in the debate on non-empirical physics.  相似文献   
2.
3.
If the general arguments concerning theinvolvement of variation and selection inexplanations of ``fit'' are valid, then variationand selection explanations should beappropriate, or at least potentiallyappropriate, outside the paradigm historisticdomains of biology and knowledge. In thisdiscussion, I wish to indicate some potentialroles for variation and selection infoundational physics – specifically inquantum field theory. I will not be attemptingany full coherent ontology for quantum fieldtheory – none currently exists, and none islikely for at least the short term future. Instead, I wish to engage in some partiallyspeculative interpretations of some interestingresults in this area with the aim ofdemonstrating that variation and selectionnotions might play a role even here. Ifvariation and selection can survive in even asinhospitable and non-paradigmatic a terrain asfoundational physics, then it can surviveanywhere.  相似文献   
4.
B S Qiu  C H Cho  C W Ogle 《Experientia》1992,48(4):389-391
Ten-day treatment with nicotine (5, 25 or 50 micrograms/ml drinking water) dose-dependently intensified gastric ulceration induced by cold-restraint, and emptying rate. Stomach contractions produced by graded doses of bethanechol i.v. were elevated further by nicotine treatment. It is suggested that chronic nicotine administration produces hypersensitivity of the gastric muscarinic receptors; stomach hypermotility contributes to the ulcer-worsening action of the alkaloid.  相似文献   
5.
6.
7.
8.
Summary The authors show the antibiotic activity of water-insoluble salts of hydrosoluble antibiotics in the case of penicillin G (salts of iron, copper, silver, gold, and uranium) and streptomycin (oleate).  相似文献   
9.
10.
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