全文获取类型
收费全文 | 21387篇 |
免费 | 42篇 |
国内免费 | 74篇 |
专业分类
系统科学 | 73篇 |
丛书文集 | 279篇 |
教育与普及 | 68篇 |
理论与方法论 | 87篇 |
现状及发展 | 9775篇 |
研究方法 | 914篇 |
综合类 | 10032篇 |
自然研究 | 275篇 |
出版年
2013年 | 172篇 |
2012年 | 313篇 |
2011年 | 575篇 |
2010年 | 140篇 |
2008年 | 343篇 |
2007年 | 398篇 |
2006年 | 366篇 |
2005年 | 400篇 |
2004年 | 363篇 |
2003年 | 360篇 |
2002年 | 356篇 |
2001年 | 592篇 |
2000年 | 583篇 |
1999年 | 406篇 |
1992年 | 379篇 |
1991年 | 303篇 |
1990年 | 334篇 |
1989年 | 327篇 |
1988年 | 335篇 |
1987年 | 327篇 |
1986年 | 306篇 |
1985年 | 434篇 |
1984年 | 292篇 |
1983年 | 264篇 |
1982年 | 252篇 |
1981年 | 239篇 |
1980年 | 307篇 |
1979年 | 715篇 |
1978年 | 548篇 |
1977年 | 560篇 |
1976年 | 435篇 |
1975年 | 477篇 |
1974年 | 615篇 |
1973年 | 549篇 |
1972年 | 609篇 |
1971年 | 618篇 |
1970年 | 807篇 |
1969年 | 691篇 |
1968年 | 709篇 |
1967年 | 646篇 |
1966年 | 585篇 |
1965年 | 400篇 |
1964年 | 115篇 |
1959年 | 217篇 |
1958年 | 389篇 |
1957年 | 300篇 |
1956年 | 271篇 |
1955年 | 222篇 |
1954年 | 202篇 |
1948年 | 178篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
21.
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
22.
1 Results The development of the concepts of nanotechnology has given an important impact on the design of new polymer based materials which are in most cases characterized by a multiphase morphology. When at least one phase has nanometric dimension(s) the system can be considered as a nanocomposite where the interface is not only determining for the adhesion but also may play a role in some bulk properties. Indeed in nanostructured multiphase solids the interface is significant as a bulk component. The... 相似文献
23.
1 Results Pyrimidinones (PMs) are a class of important heterocycles which have been well documented throughout the literature due to their biological importance. They exhibit a wide range of pharmaceutical and therapeutic properties[1].A rapid and efficient one-pot method for the synthesis of 4,6-diarylpyrimidin-2(1H)- ones and related heterocycles is described.The condensation of acetophenone derivatives,aldehydes and urea in the presence of sulfamic acid was employed to synthesize a variety of pyrimid... 相似文献
24.
Summary The application of diphenylilacetic acid has shown favorable effects on the growth of tobacco plants. Solutions containing 10 p.p.m. and 20 p.p.m. produce, in weight, an almost double growth in treated plants in comparison with the controls. Diphenylilacetic acid can be considered as a growth-promoting substance. The data are not definite. 相似文献
25.
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
26.
27.
A. F. McDonagh Y. -M. Pu D. A. Lightner 《Cellular and molecular life sciences : CMLS》1992,48(3):246-248
The characteristic circular dichroism of bilirubin bound to human serum albumin undergoes a remarkable sign inversion on addition of halothane, chloroform and other volatile anesthetics. This sign inversion, which is completely reversed by removal of the anesthetic, reflects a pronounced conformational change of the bound ligand; probably a complete inversion of chirality. The observation suggests that association of volatile anesthetics with proteins can markedly alter the internal topography of receptor sites and potentially influence the stereoselectivity of ligand binding. 相似文献
28.
29.
DNA fingerprinting transforms the art of cell authentication. 总被引:4,自引:0,他引:4
The increasing diversity of new cell cultures is seriously stretching the capabilities of traditional methods of identification. DNA fingerprinting is set to play an important role in increasing confidence in the authenticity of cultures in research and industry. 相似文献
30.
Thyroid cancer after Chernobyl. 总被引:17,自引:0,他引:17