全文获取类型
收费全文 | 40592篇 |
免费 | 2319篇 |
国内免费 | 1718篇 |
专业分类
化学 | 18612篇 |
晶体学 | 427篇 |
力学 | 2205篇 |
综合类 | 119篇 |
数学 | 10206篇 |
物理学 | 13060篇 |
出版年
2024年 | 40篇 |
2023年 | 296篇 |
2022年 | 511篇 |
2021年 | 570篇 |
2020年 | 553篇 |
2019年 | 542篇 |
2018年 | 1619篇 |
2017年 | 1846篇 |
2016年 | 1344篇 |
2015年 | 1166篇 |
2014年 | 1188篇 |
2013年 | 1506篇 |
2012年 | 4211篇 |
2011年 | 3353篇 |
2010年 | 2610篇 |
2009年 | 2276篇 |
2008年 | 1269篇 |
2007年 | 1242篇 |
2006年 | 1242篇 |
2005年 | 4992篇 |
2004年 | 4263篇 |
2003年 | 2583篇 |
2002年 | 779篇 |
2001年 | 513篇 |
2000年 | 299篇 |
1999年 | 381篇 |
1998年 | 286篇 |
1997年 | 272篇 |
1996年 | 232篇 |
1995年 | 202篇 |
1994年 | 181篇 |
1993年 | 122篇 |
1992年 | 256篇 |
1991年 | 231篇 |
1990年 | 214篇 |
1989年 | 177篇 |
1988年 | 151篇 |
1987年 | 86篇 |
1986年 | 86篇 |
1985年 | 68篇 |
1984年 | 46篇 |
1983年 | 41篇 |
1976年 | 80篇 |
1975年 | 44篇 |
1974年 | 42篇 |
1973年 | 52篇 |
1972年 | 46篇 |
1970年 | 36篇 |
1969年 | 38篇 |
1966年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
S?awomir Solecki 《Topology and its Applications》2007,154(12):2462-2464
Let I0 be the σ-ideal of subsets of a Polish group generated by Borel sets which have perfectly many pairwise disjoint translates. We prove that a Fubini-type theorem holds between I0 and the σ-ideals of Haar measure zero sets and of meager sets. We use this result to give a simple proof of a generalization of a theorem of Balcerzak-Ros?anowski-Shelah stating that I0 on N2 strongly violates the countable chain condition. 相似文献
62.
63.
R. Knizikevi?ius 《Applied Surface Science》2006,253(3):1581-1583
The ion-beam-assisted etching of silicon in Cl2 environment is considered. The theoretically calculated dependences of silicon etching rate on the flux of Cl2 molecules at different ion current densities are compared with experimentally measured. The composition of the adsorbed layer is determined. It is found that SiCl2 molecules prevail in the adsorbed layer. The reciprocal of relative concentration of SiCl2 molecules in the adsorbed layer linearly depends on the ion-to-neutral flux ratio. 相似文献
64.
65.
Nanometer scale Al/AlN multilayers have been prepared by dc magnetron sputtering technique with a columnar target. A set of Al/AlN multilayers with the Al layer thickness of 2.9 nm and the AlN layer thickness variation from 1.13 to 6.81 nm were determined. Low angle X-ray diffraction (LAXRD) was used to analyze the layered structure of multilayers. The phase structure of the coatings was investigated with grazing angle XRD (GAXRD). Mechanical properties of these multilayers were thoroughly studied using a nanoindentation and ball-on-disk micro-tribometer. It was found that the multilayer hardness and reduced modulus showed no strong dependence on the AlN layer thickness. Al2.9 nm/AlN1.13 nm multilayer had more excellent tribological properties than single layers and other proportion multilayers with a lowest friction coefficient of 0.15. And the tribological properties of all the multilayers are superior to the AlN single layer. 相似文献
66.
M. A. Rizzutto N. Added M. H. Tabacniks F. R. Espinoza-Qui?ones S. M. Palacio R. M. Galante R. M. Galante N. Rossi R. A. Welter A. N. Módenes 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(3):727-731
Summary Kulcsszavak (angolul, ha nem azonos az elozovel) 相似文献
67.
Peptidosulfonamides are an emerging group of peptidomimetics with a variety of applications in medicinal chemistry. We present a novel approach to the synthesis of peptidosulfonamides, and apply it to a series of new potential inhibitors of the bacterial peptidoglycan biosynthesis enzymes MurD and MurE. The synthesis was conducted via N-phthalimido β-aminoethanesulfonyl chlorides, which are new building blocks for the synthesis of peptidosulfonamides. In the most crucial step, sulfonic acids or their sodium salts were converted into the corresponding sulfonyl chlorides using an excess of either SOCl2 or SOCl2/DMF, and then coupled to the C-protected amino acid. None of the compounds significantly inhibited MurD, however, some inhibited MurE; one had an IC50 below 200 μM, which constitutes a promising starting point for further development. Molecular modelling simulations were performed on two analogues to investigate the absence of inhibitory activity of the sulfonamide compounds on MurD. 相似文献
68.
69.
文章介绍2001年度国家自然科学奖二等奖获奖成果,在北京正负电子对撞机上采集了Ψ(2S)粒子大数据样本,开展了粲偶素物理的广泛研究:完成了6个粲偶素涉及质量,宽度和衰变化支比等大批重要参数的首次测量或高精度测量;通过对Ψ(2S)和J/Ψ强衰变性质的比较研究,观察到一系列反常现象,挑战现有理论图像。该项研究成果对量子色动力学的检验与发展具有重要意义,为我国粲偶素物理实验研究的继续发展并保持先进水平奠定坚实基础。 相似文献
70.
Jinyan Fan 《Computational Optimization and Applications》2006,34(2):215-227
In this paper, we present the new trust region method for nonlinear equations with the trust region converging to zero. The
new method preserves the global convergence of the traditional trust region methods in which the trust region radius will
be larger than a positive constant. We study the convergence rate of the new method under the local error bound condition
which is weaker than the nonsingularity. An example given by Y.X. Yuan shows that the convergence rate can not be quadratic.
Finally, some numerical results are given.
This work is supported by Chinese NSFC grants 10401023 and 10371076, Research Grants for Young Teachers of Shanghai Jiao Tong
University, and E-Institute of Computational Sciences of Shanghai Universities.
An erratum to this article is available at . 相似文献