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   41546篇
  免费   79篇
  国内免费   106篇
系统科学   211篇
丛书文集   801篇
教育与普及   102篇
理论与方法论   245篇
现状及发展   17504篇
研究方法   1665篇
综合类   20575篇
自然研究   628篇
  2013年   318篇
  2012年   573篇
  2011年   1232篇
  2010年   255篇
  2008年   699篇
  2007年   764篇
  2006年   802篇
  2005年   770篇
  2004年   712篇
  2003年   738篇
  2002年   748篇
  2001年   1348篇
  2000年   1256篇
  1999年   793篇
  1992年   745篇
  1991年   615篇
  1990年   629篇
  1989年   661篇
  1988年   638篇
  1987年   651篇
  1986年   663篇
  1985年   767篇
  1984年   650篇
  1983年   544篇
  1982年   474篇
  1981年   457篇
  1980年   581篇
  1979年   1281篇
  1978年   1108篇
  1977年   1062篇
  1976年   777篇
  1975年   854篇
  1974年   1248篇
  1973年   1048篇
  1972年   1073篇
  1971年   1342篇
  1970年   1734篇
  1969年   1274篇
  1968年   1255篇
  1967年   1241篇
  1966年   1107篇
  1965年   790篇
  1964年   180篇
  1959年   450篇
  1958年   693篇
  1957年   554篇
  1956年   449篇
  1955年   386篇
  1954年   445篇
  1948年   260篇
排序方式: 共有10000条查询结果,搜索用时 109 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.
The career of John Jackson (1686-1763), Arian theologian and controversialist, provides a key to unlocking the early reception and quick collapse of a Newtonian natural apologetic originally developed by Samuel Clarke. The importance of friendship and discipleship in eighteenth-century intellectual enquiry is emphasised, and the links between Newton and his followers are traced alongside those of a group of Cambridge Lockeans, led by Jackson’s direct contemporary Daniel Waterland, who proved instrumental in the initial dismantling of Clarke’s brand of Newtonian apologetic. The controversial context of this engagement is shown to have been largely provided by the religiously compromising rise of freethinking, and Tindal’s Christianity as old as the creation (1731) signalled the dangers to proponents of natural religion as an adjunct of Christian apologetic in such a heated atmosphere. Religious division of the sort that resulted paradoxically played into the hands of the freethinkers in the anticlerical atmosphere of the 1730s, and accusations were exchanged between Newtonians and Lockeans accordingly. The dynamic of England’s Enlightenment experience is, then, a complicated one, and, as the career and writings of Jackson and William Whiston demonstrate, it was one which absorbed as well as repudiated ‘enthusiasm’.  相似文献   
6.
7.
8.
以具体工程为例,介绍了建筑物地基处理的设计、施工中遵循的原则,施工中遇到特殊情况时采取的处理方法和必要的检测方法,对几种桩基的设计要求、施工工艺及过程、质量控制等情况进行了简单阐述。  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