全文获取类型
收费全文 | 51455篇 |
免费 | 185篇 |
国内免费 | 173篇 |
专业分类
系统科学 | 337篇 |
丛书文集 | 905篇 |
教育与普及 | 145篇 |
理论与方法论 | 294篇 |
现状及发展 | 22894篇 |
研究方法 | 1760篇 |
综合类 | 24839篇 |
自然研究 | 639篇 |
出版年
2013年 | 327篇 |
2012年 | 722篇 |
2011年 | 1373篇 |
2008年 | 789篇 |
2007年 | 827篇 |
2006年 | 838篇 |
2005年 | 1062篇 |
2004年 | 1324篇 |
2003年 | 1290篇 |
2002年 | 953篇 |
2001年 | 1411篇 |
2000年 | 1404篇 |
1999年 | 941篇 |
1994年 | 400篇 |
1992年 | 840篇 |
1991年 | 688篇 |
1990年 | 758篇 |
1989年 | 723篇 |
1988年 | 739篇 |
1987年 | 766篇 |
1986年 | 772篇 |
1985年 | 947篇 |
1984年 | 724篇 |
1983年 | 652篇 |
1982年 | 582篇 |
1981年 | 565篇 |
1980年 | 722篇 |
1979年 | 1540篇 |
1978年 | 1307篇 |
1977年 | 1261篇 |
1976年 | 977篇 |
1975年 | 1072篇 |
1974年 | 1437篇 |
1973年 | 1295篇 |
1972年 | 1376篇 |
1971年 | 1662篇 |
1970年 | 2051篇 |
1969年 | 1632篇 |
1968年 | 1577篇 |
1967年 | 1555篇 |
1966年 | 1354篇 |
1965年 | 968篇 |
1964年 | 294篇 |
1959年 | 552篇 |
1958年 | 917篇 |
1957年 | 690篇 |
1956年 | 600篇 |
1955年 | 552篇 |
1954年 | 562篇 |
1948年 | 389篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Shiga toxin and some other protein toxins that act on targets in the cytosol have previously been shown to enter the trans-Golgi network. Transport by this route may be necessary for translocation of the toxin to the cytosol and for intoxication, but it is not known whether the enzymatically active part of the toxins actually enters the cytosol from the trans-Golgi network. It has been suggested that such toxins are transported in a retrograde manner to the endoplasmic reticulum and that translocation occurs in this organelle, but retrograde transport of endocytosed material beyond the trans-Golgi network has never been demonstrated. Here we show that in butyric acid-treated A431 cells endocytosed Shiga toxin is not only transported to the trans-Golgi network, but also to all Golgi stacks, to the endoplasmic reticulum and to the nuclear envelope. Furthermore, butyric acid sensitizes the cells to Shiga toxin, which is consistent with the possibility that retrograde transport is required for translocation of the toxin to the cytosol. 相似文献
42.
43.
44.
45.
H R Brenner 《Nature》1985,317(6038):572-573
46.
47.
48.
David H. Hubel 《自然科学进展(英文版)》2007,17(13):1-3
The visual field is topographically mapped onto the primary visual cortex (V1), forming a retinotopic map which is far more detailed for the foveal regions than for the periphery. We found that receptive field (RF) size in monkey V1 increases with eccentricity, and that a 1—2 m2 V1 region contains roughly a complete set of machinery necessary to analyze a visual-field area whose size is about that of the RFs of the cells. This allows V1 to be anatomically uniform, and is in sharp contrast with the retina. 相似文献
49.
1 Results This paper presents the development of platinum nanocomposites structures based on organically modified c.a.2 nm core platinum nanoparticles.The chemical modification of the 4-mercaptoaniline functionalized particles by various in coming molecules is evidenced and precisely quantified.The particles can be dissolved like molecules in various solvents depending on the features of the new crown and X-rays shows that the interparticle distance is affected by the crown modification.These platinum n... 相似文献
50.
Kang J.Y. Xu F.C. 《中国科学基金(英文版)》2004,(2):57-58,64
1 Introduction
Nanoscale science and technology have attracted greatattention since the novel properties become dominant for well-known materials as their sizes reduced to some critical dimension. These properties frequently originate in lattice distortions, structure transformations etc[1]. The variations of size and structure ofnanocrystals lead to the change of their electronic structures. Very recently, nanoscale materials with different electronic structures were utilized in fabricating nanoscale junctions[2].
…… 相似文献