全文获取类型
收费全文 | 183337篇 |
免费 | 37570篇 |
国内免费 | 26263篇 |
专业分类
化学 | 120743篇 |
晶体学 | 2149篇 |
力学 | 12261篇 |
综合类 | 629篇 |
数学 | 21953篇 |
物理学 | 89435篇 |
出版年
2024年 | 748篇 |
2023年 | 2861篇 |
2022年 | 4454篇 |
2021年 | 4760篇 |
2020年 | 5263篇 |
2019年 | 5584篇 |
2018年 | 4964篇 |
2017年 | 5176篇 |
2016年 | 7353篇 |
2015年 | 7331篇 |
2014年 | 8303篇 |
2013年 | 11904篇 |
2012年 | 13678篇 |
2011年 | 15342篇 |
2010年 | 15333篇 |
2009年 | 15194篇 |
2008年 | 9748篇 |
2007年 | 8784篇 |
2006年 | 7978篇 |
2005年 | 7424篇 |
2004年 | 6919篇 |
2003年 | 5536篇 |
2002年 | 5071篇 |
2001年 | 5034篇 |
2000年 | 4031篇 |
1999年 | 4623篇 |
1998年 | 3938篇 |
1997年 | 3644篇 |
1996年 | 4115篇 |
1995年 | 4148篇 |
1994年 | 4120篇 |
1993年 | 3899篇 |
1992年 | 3407篇 |
1991年 | 2975篇 |
1990年 | 2501篇 |
1989年 | 2378篇 |
1988年 | 2257篇 |
1987年 | 1496篇 |
1986年 | 1550篇 |
1985年 | 1166篇 |
1984年 | 1209篇 |
1983年 | 501篇 |
1982年 | 1020篇 |
1981年 | 837篇 |
1980年 | 845篇 |
1979年 | 570篇 |
1978年 | 564篇 |
1977年 | 660篇 |
1976年 | 1077篇 |
1972年 | 549篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
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
132.
5,6-Dihydro-OSW-1 (1) was synthesized following our previous procedure for the total synthesis of OSW-1. This compound demonstrated slightly stronger potency than that of OSW-1 against the growth of cancer cells. 相似文献
133.
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
134.
XiangGuoSHI DaFangZHONG YuMingSUN YuFengZHANG 《中国化学快报》2004,15(4):431-434
A sensitive analytical method to identify active metabolites of bitespiramycin in rat urine and bile was developed by liquid chromatography-electrospray ionization tandem mass spectrometry(LC/ESI-MS^n).Bitespiramycin and its major active metabolites in rat urine and bile were isolated and identified as M1 serial(spiramycin Ⅰ,Ⅱ,Ⅲ),M2 serial(platenomycin A1,josamycin and leucomycin A1) and M3 serial(deisovalerylplatenomycin A1,deisovaleryljosamycin,deisovalerylleucomycin A1). 相似文献
135.
DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
136.
G. Z. Ruan S. Y. Wang Y. Yamamoto S. S. Zhu 《Journal of Optimization Theory and Applications》2004,123(2):409-429
In this paper, a model of a linear multilevel programming problem with dominated objective functions (LMPPD(l)) is proposed, where multiple reactions of the lower levels do not lead to any uncertainty in the upper-level decision making. Under the assumption that the constrained set is nonempty and bounded, a necessary optimality condition is obtained. Two types of geometric properties of the solution sets are studied. It is demonstrated that the feasible set of LMPPD(l) is neither necessarily composed of faces of the constrained set nor necessarily connected. These properties are different from the existing theoretical results for linear multilevel programming problems. 相似文献
137.
The notion of Kuratowski convergence is applied to describe a kind of convergence in the context of holomorphic functions. We associate it to a convenient topology, explore its relation with the compact-open topology, thus providing a new set theoretic point of view of this classic topology, and present it in the framework of set-valued mappings. 相似文献
138.
We consider a spinning charge coupled to the Maxwell field. Through the appropriate symmetry in the initial conditions the charge remains at rest. We establish that any time-dependent finite energy solution converges to a sum of a soliton wave and an outgoing free wave. The convergence holds in global energy norm. Under a small constant external magnetic field the soliton manifold is stable in local energy seminorms and the evolution of the angular velocity is guided by an effective finite-dimensional dynamics. The proof uses a non-autonomous integral inequality method. 相似文献
139.
140.
We give a Gray code and constant average time generating algorithm for derangements, i.e., permutations with no fixed points. In our Gray code, each derangement is transformed into its successor either via one or two transpositions or a rotation of three elements. We generalize these results to permutations with number of fixed points bounded between two constants. 相似文献