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   33170篇
  免费   53篇
  国内免费   91篇
系统科学   197篇
丛书文集   718篇
教育与普及   89篇
理论与方法论   234篇
现状及发展   13721篇
研究方法   1504篇
综合类   16405篇
自然研究   446篇
  2013年   214篇
  2012年   537篇
  2011年   1060篇
  2010年   232篇
  2008年   700篇
  2007年   702篇
  2006年   743篇
  2005年   775篇
  2004年   712篇
  2003年   717篇
  2002年   749篇
  2001年   982篇
  2000年   909篇
  1999年   606篇
  1992年   574篇
  1991年   465篇
  1990年   487篇
  1989年   494篇
  1988年   490篇
  1987年   499篇
  1986年   492篇
  1985年   600篇
  1984年   498篇
  1983年   411篇
  1982年   355篇
  1981年   349篇
  1980年   451篇
  1979年   970篇
  1978年   862篇
  1977年   852篇
  1976年   580篇
  1975年   631篇
  1974年   932篇
  1973年   790篇
  1972年   806篇
  1971年   1022篇
  1970年   1345篇
  1969年   1005篇
  1968年   947篇
  1967年   990篇
  1966年   830篇
  1965年   611篇
  1964年   148篇
  1959年   360篇
  1958年   522篇
  1957年   443篇
  1956年   366篇
  1955年   316篇
  1954年   363篇
  1948年   193篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Archive for History of Exact Sciences - We show that Dedekind, in his proof of the principle of definition by mathematical recursion, used implicitly both the concept of an inductive cone from an...  相似文献   
3.
4.
G protein-coupled receptor (GPCR) signalling is mediated through transactivation-independent signalling pathways or the transactivation of protein tyrosine kinase receptors and the recently reported activation of the serine/threonine kinase receptors, most notably the transforming growth factor-β receptor family. Since the original observation of GPCR transactivation of protein tyrosine kinase receptors, there has been considerable work on the mechanism of transactivation and several pathways are prominent. These pathways include the “triple membrane bypass” pathway and the generation of reactive oxygen species. The recent recognition of GPCR transactivation of serine/threonine kinase receptors enormously broadens the GPCR signalling paradigm. It may be predicted that the transactivation of serine/threonine kinase receptors would have mechanistic similarities with transactivation of tyrosine kinase pathways; however, initial studies suggest that these two transactivation pathways are mechanistically distinct. Important questions are the relative importance of tyrosine and serine/threonine transactivation pathways, the contribution of transactivation to overall GPCR signalling, mechanisms of transactivation and the range of cell types in which this phenomenon occurs. The ultimate significance of transactivation-dependent signalling remains to be defined but it appears to be prominent and if so will represent a new cell signalling frontier.  相似文献   
5.
6.
国际空间站和欧洲核子中心的大型强子对撞机 (LHC)计划目前都面临资金上的窘境 ;……除了对项目 (尤其是耗资巨大的项目 )预算的科学化 ,管理的科学化在其中尤显重要  相似文献   
7.
8.
9.
I offer a reply to criticisms of the Strong Programme presented by Stephen Kemp who develops some new lines of argument that focus on the ‘monism’ of the programme. He says the programme should be rejected for three reasons. First, because it embodies ‘weak idealism’, that is, its supporters effectively sever the link between language and the world. Second, it challenges the reasons that scientists offer in explanation of their own beliefs. Third, it destroys the distinction between successful and unsuccessful instrumental action. Kemp is careful to produce quotations from the supporters of the programme as evidence to support his case. All three points deserve and are given a detailed response and the interpretation of the quoted material plays a significant role in the discussion. My hope is that careful exegesis will offset the numerous misinterpretations that are current in the philosophical literature. Particular attention is paid to what is said about the normative standards involved in the application of empirical concepts. The operation of these standards in the face of the negotiability of all concepts is explored and misapprehensions on the topic are corrected. The work of Wittgenstein, Popper, Kuhn and Hesse is used to illustrate these themes.  相似文献   
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