全文获取类型
收费全文 | 21556篇 |
免费 | 3365篇 |
国内免费 | 3972篇 |
专业分类
化学 | 17735篇 |
晶体学 | 389篇 |
力学 | 965篇 |
综合类 | 284篇 |
数学 | 2197篇 |
物理学 | 7323篇 |
出版年
2024年 | 56篇 |
2023年 | 388篇 |
2022年 | 678篇 |
2021年 | 806篇 |
2020年 | 910篇 |
2019年 | 965篇 |
2018年 | 749篇 |
2017年 | 813篇 |
2016年 | 1015篇 |
2015年 | 1099篇 |
2014年 | 1326篇 |
2013年 | 1803篇 |
2012年 | 1915篇 |
2011年 | 2092篇 |
2010年 | 1553篇 |
2009年 | 1406篇 |
2008年 | 1638篇 |
2007年 | 1431篇 |
2006年 | 1272篇 |
2005年 | 1051篇 |
2004年 | 858篇 |
2003年 | 713篇 |
2002年 | 735篇 |
2001年 | 602篇 |
2000年 | 498篇 |
1999年 | 401篇 |
1998年 | 295篇 |
1997年 | 233篇 |
1996年 | 234篇 |
1995年 | 222篇 |
1994年 | 205篇 |
1993年 | 160篇 |
1992年 | 116篇 |
1991年 | 107篇 |
1990年 | 108篇 |
1989年 | 76篇 |
1988年 | 67篇 |
1987年 | 43篇 |
1986年 | 53篇 |
1985年 | 59篇 |
1984年 | 39篇 |
1983年 | 31篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
LI Shufeng LI Qian YANG Xinlin HUANG Wenqiang** State Key Laboratory of Functional Polymer Materials for Adsorption Separation Institute of Polymer Chemistry Nankai University Tianjin China 《Chinese Journal of Reactive Polymers》2004,(Z1)
1. INTRODUCTION The development of efficient polymer-supported catalysts has attracted much attention [1]. For obtaining polymeric catalysts, catalytically active groups were introduced onto polymers mostly by copolymerization of the appropriate monomers bearing the desired catalyticfunctionalities (e.g. imidazole, OH, and COOH) or by modification of preformed polymers.Another possibility involves the attachment of side chains, containing the desired arrangement of functional groups, o… 相似文献
54.
Qing An WU Zhen Yuan XU Mei ZHENG Dan Qian XU Jun XU Yin Chu SHENCollege of Chemical Engineering Materials Zhejiang University of Technology Hangzhou 《中国化学快报》2004,(7)
Six new 13-O-acylavermectin Bl aglycones(3-8) were synthesized from avermectin B1 aglycone and their bioactivities were evaluated against Spodoptera exigua, Spodoptera eridania, Tetranychus urticae and Aphis fabae. 相似文献
55.
The adsorption of asymmetrical triblock copolymers from a non-selective solvent on solid surface has been studied by using Scheutjens-Fleer mean-field theory and Monte Carlo simulation method on lattice model. The main aim of this paper is to provide detailed computer simulation data, taking A8-kB20Ak as a key example, to study the influence of the structure of copolymer on adsorption behavior and make a comparison between MC and SF results. The simulated results show that the size distribution of various configurations and density-profile are dependent on molecular structure and adsorption energy. The molecular structure will lead to diversity of adsorption behavior. This discrepancy between different structures would be enlarged for the surface coverage and adsorption amount with increasing of the adsorption energy. The surface coverage and the adsorption amount as well as the bound fraction will become larger as symmetry of the molecular structure becomes gradually worse. The adsorption layer becomes thicker with increasing of symmetry of the molecule when adsorption energy is smaller but it becomes thinner when adsorption energy is higher. It is shown that SF theory can reproduce the adsorption behavior of asymmetrical triblock copolymers. However, systematic discrepancy between the theory and simulation still exists.The approximations inherited in the mean-filed theory such as random mixing and the allowance of direct back folding may be responsible for those deviations. 相似文献
56.
The compression behaviour of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state is determined by fitting the experimental data according to the Birch-Murnaghan equation. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa. Within the pressure range from zero to the experimental one, the pressure-induced structural relaxation is reversible. 相似文献
57.
本文报道在四氢吠喃中通过金属锡促进Q_澳代酷与二硒醚反应生成a一硒代酷,反应条件温和,产率良好. 相似文献
58.
The equivalent geometrical configurations of linear ordered orthogonal arrays are determined when their strengths are 3 and 4. Existence of such geometrical configurations is investigated. They are also useful in the study of (T, M, S)-nets. 相似文献
59.
60.