全文获取类型
收费全文 | 34482篇 |
免费 | 636篇 |
国内免费 | 512篇 |
专业分类
化学 | 14624篇 |
晶体学 | 318篇 |
力学 | 1547篇 |
综合类 | 20篇 |
数学 | 9755篇 |
物理学 | 9366篇 |
出版年
2023年 | 61篇 |
2022年 | 130篇 |
2021年 | 182篇 |
2020年 | 173篇 |
2019年 | 185篇 |
2018年 | 1305篇 |
2017年 | 1568篇 |
2016年 | 929篇 |
2015年 | 771篇 |
2014年 | 738篇 |
2013年 | 1053篇 |
2012年 | 3564篇 |
2011年 | 2802篇 |
2010年 | 2082篇 |
2009年 | 1818篇 |
2008年 | 944篇 |
2007年 | 974篇 |
2006年 | 885篇 |
2005年 | 4705篇 |
2004年 | 4141篇 |
2003年 | 2506篇 |
2002年 | 661篇 |
2001年 | 404篇 |
2000年 | 204篇 |
1999年 | 247篇 |
1998年 | 183篇 |
1997年 | 134篇 |
1996年 | 121篇 |
1995年 | 84篇 |
1994年 | 104篇 |
1993年 | 83篇 |
1992年 | 203篇 |
1991年 | 189篇 |
1990年 | 150篇 |
1989年 | 137篇 |
1988年 | 118篇 |
1987年 | 73篇 |
1986年 | 68篇 |
1985年 | 65篇 |
1984年 | 52篇 |
1979年 | 40篇 |
1976年 | 84篇 |
1975年 | 45篇 |
1974年 | 44篇 |
1973年 | 55篇 |
1972年 | 43篇 |
1970年 | 37篇 |
1969年 | 40篇 |
1968年 | 39篇 |
1966年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Micha? Chmielewski 《Tetrahedron letters》2004,45(31):6007-6010
Comparison of the anion binding properties of a series of uncharged macrocyclic tetraamides reveal significant effects of the receptor's size on the strength of its anion complexes. This study allowed for estimation of the optimal size of a macroring for complexation of common anions. 相似文献
22.
Sándor G?r?g 《Analytical sciences》2004,20(5):767-782
The development during the last 15 years and the state-of-the-art in the analysis of bulk steroid hormone drugs and hormone-like structures and pharmaceutical formulations made thereof are summarized. Other steroids (sterols, bile acids, cardiac glycosides, vitamins D) as well as biological-clinical aspects and pharmacokinetic and metabolic studies are excluded from this review. The state-of-the-art is summarized based on comparisons of monographs in the latest editions of the European Pharmacopoeia, United States Pharmacopoeia and the Japanese Pharmacopoeia. This is followed by sections dealing with new developments in the methodology for the fields of spectroscopic and spectrophotometric, chromatographic, electrophoretic and hyphenated techniques as well electroanalytical methods. The review is terminated by two problem-oriented sections: examples on impurity and degradation profiling as well as enantiomeric analysis. 相似文献
23.
The electrochemical reduction of 1-([(4-halophenyl)imino]methyl)-2-naphthols on graphite electrodes was studied using cyclic voltammetry, chronoamperometry, constant-potential coulometry and preparative constant-potential electrolysis techniques. The data revealed that the reduction on graphite was irreversible and followed an EC mechanism. The diffusion coefficients and the number of electrons transferred were determined using the chronoamperometric Cottrell slope and the ultramicro disc Pt-electrode steady-state current. The number of electrons was also determined by bulk electrolysis. The compounds were subjected to constant-potential preparative electrolysis and the electrolysis products were purified and identified by spectroscopic methods. Based on these findings, a mechanism for the electro-reduction process is proposed. 相似文献
24.
JingXiaWANG ChengYouKAN DeShanLIU 《中国化学快报》2004,15(10):1161-1163
Two novel polymerizable dyes with anthraquinone residue have been prepared, and their structures were characterized by FTIR, ^1HNMR and EA. 相似文献
25.
26.
27.
Paramagnetic pyrroline and 1,2,3,6-tetrahydropyridine derivatives of BODIPY and their diamagnetic analogs have been synthesized and characterized as novel redox double sensor and cation sensitive reagents. 相似文献
28.
29.
Let f be a smooth map between unit spheres of possibly different dimensions. We prove the global existence and convergence of the mean curvature flow of the graph of f under various conditions. A corollary is that any area‐decreasing map between unit spheres (of possibly different dimensions) is isotopic to a constant map. © 2004 Wiley Periodicals, Inc. 相似文献
30.
Francesc Carreras M. Dolors Llongueras Antonio Magaña 《Annals of Operations Research》2005,137(1):67-89
A partnership in a cooperative game is a coalition that possesses an internal structure and, simultaneously, behaves as an
individual member. Forming partnerships leads to a modification of the original game which differs from the quotient game
that arises when one or more coalitions are actually formed.
In this paper, the Shapley value is used to discuss the convenience to form either coalitions or partnerships. To this end,
the difference between the additive Shapley value of the partnership in the partnership game and the Shapley alliance value
of the coalition, and also between the corresponding value of the internal and external players, are analysed. Simple games
are especially considered.
Research partially supported by Grant BFM 2003-01314 of the Science and Technology Spanish Ministry and the European Regional
Development Fund. 相似文献