全文获取类型
收费全文 | 2430篇 |
免费 | 21篇 |
国内免费 | 13篇 |
专业分类
化学 | 1311篇 |
晶体学 | 21篇 |
力学 | 97篇 |
数学 | 529篇 |
物理学 | 506篇 |
出版年
2020年 | 18篇 |
2019年 | 18篇 |
2016年 | 25篇 |
2015年 | 21篇 |
2014年 | 31篇 |
2013年 | 124篇 |
2012年 | 62篇 |
2011年 | 75篇 |
2010年 | 54篇 |
2009年 | 60篇 |
2008年 | 82篇 |
2007年 | 70篇 |
2006年 | 116篇 |
2005年 | 94篇 |
2004年 | 72篇 |
2003年 | 80篇 |
2002年 | 58篇 |
2001年 | 50篇 |
2000年 | 55篇 |
1999年 | 36篇 |
1998年 | 49篇 |
1997年 | 42篇 |
1996年 | 58篇 |
1995年 | 37篇 |
1994年 | 46篇 |
1993年 | 39篇 |
1992年 | 36篇 |
1991年 | 40篇 |
1990年 | 35篇 |
1989年 | 29篇 |
1988年 | 26篇 |
1987年 | 32篇 |
1986年 | 21篇 |
1985年 | 51篇 |
1984年 | 40篇 |
1983年 | 36篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 50篇 |
1979年 | 28篇 |
1978年 | 40篇 |
1977年 | 54篇 |
1976年 | 38篇 |
1975年 | 27篇 |
1974年 | 43篇 |
1973年 | 37篇 |
1972年 | 27篇 |
1971年 | 23篇 |
1969年 | 30篇 |
1968年 | 15篇 |
排序方式: 共有2464条查询结果,搜索用时 46 毫秒
121.
122.
Norman Biggs 《BSHM Bulletin: Journal of the British Society for the History of Mathematics》2018,33(3):166-178
In the twentieth century the theory of games was transformed. It began as an amusing pastime, and ended as a major branch of mathematical research and a key paradigm of economic theory. Here it will be argued that the transformation was the result of the work of mathematicians, such as Ernst Zermelo, John von Neumann and Dénes K?nig, who also contributed to two other areas of mathematics that were emerging at the same time: the theory of sets and the theory of graphs. 相似文献
123.
JETP Letters - It is shown that a sharp increase in viscosity, a change in the decay rate of correlations, and the appearance of nonequilibrium and transverse sound in a thin film of aluminum melt... 相似文献
124.
125.
126.
Emily F. Evans Norman J. Lewis Isabelle Kapfer Gregor Macdonald Richard J. K. Taylor 《合成通讯》2013,43(11):1819-1825
A mild and efficient procedure is described for the removal of the tert-butoxycarbonyl (BOC) group using boron trifluoride etherate and molecular sieves in dichloromethane at room temperature. The scope of this procedure is explored for the deprotection of a variety of amines including amino acid derivatives. 相似文献
127.
Abstract Novel synthetic routes directed toward the preparation of (+/?)-cis -4-amino-2-cyclopentene-1-methanol are described. The routes investigated involve azide openings of chiral and non-chiral cyclopentyl epoxides. 相似文献
128.
Ren Y Acuña UM Jiménez F García R Mejía M Chai H Gallucci JC Farnsworth NR Soejarto DD Carcache de Blanco EJ Kinghorn AD 《Tetrahedron》2012,68(12):2671-2678
Six new (1-6) and eight known germacranolide-type sesquiterpene lactones, along with several known phenylpropanol coumarates and methylated flavonoids, were isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. The new compounds were identified by analysis of their spectroscopic data, with the molecular structure of 3 being established by single-crystal X-ray diffraction. The absolute configurations of the sesquiterpene lactones isolated were determined from their CD and NOESY NMR spectra, together with the analysis of Mosher ester reactions. Bioassay screening results showed the majority of the sesquiterpene lactones isolated (1-13) to be highly cytotoxic toward the HT-29 human colon cancer cell line, with the most potent compound being 15-deoxygoyazensolide (10, IC(50), 0.26 μM). In addition, several of the sesquiterpene lactones exhibited NF-κB (p65) inhibitory activity. 相似文献
129.
130.
Mark D. Noirot Elizabeth G. Bent Arlan D. Norman 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):177-180
Abstract Reaction of the 1,3,2,4-diazadiphosphetidine, trans-[C6H5N(H)P(S)NC6H5]2 with LiR (R = Me, n-Bu) followed by treatment of the resulting dianions with Me3SiCl and Me3GeBr produced trans-[C6H5N(R)P(S)NC6H5]2(R = Me3Si, 2; Me3Ge, 3). Substitution occurs without cis-trans isomerization or significant cleavage of the 1,3,2,4-diazadiphosphetidine ring. 2 and 3 have been characterized by spectral (1H and 31P NMR, IR, and MS) and elemental analytical data. Analogous reactions involving Me3SnCl yield mixtures containing [C6H5N(SnMe3)P(S)NC6H5]2 which could not be isolated or completely characterized. 相似文献