全文获取类型
收费全文 | 183850篇 |
免费 | 38100篇 |
国内免费 | 31255篇 |
专业分类
化学 | 123709篇 |
晶体学 | 2573篇 |
力学 | 11444篇 |
综合类 | 1194篇 |
数学 | 23537篇 |
物理学 | 90748篇 |
出版年
2024年 | 721篇 |
2023年 | 2710篇 |
2022年 | 4659篇 |
2021年 | 4750篇 |
2020年 | 5212篇 |
2019年 | 5439篇 |
2018年 | 5151篇 |
2017年 | 5543篇 |
2016年 | 7136篇 |
2015年 | 7446篇 |
2014年 | 8530篇 |
2013年 | 12037篇 |
2012年 | 13688篇 |
2011年 | 15336篇 |
2010年 | 16041篇 |
2009年 | 16078篇 |
2008年 | 10580篇 |
2007年 | 9371篇 |
2006年 | 8742篇 |
2005年 | 7942篇 |
2004年 | 7550篇 |
2003年 | 6021篇 |
2002年 | 5601篇 |
2001年 | 5627篇 |
2000年 | 4645篇 |
1999年 | 4731篇 |
1998年 | 3817篇 |
1997年 | 3449篇 |
1996年 | 3758篇 |
1995年 | 3991篇 |
1994年 | 3947篇 |
1993年 | 3762篇 |
1992年 | 3327篇 |
1991年 | 2827篇 |
1990年 | 2385篇 |
1989年 | 2355篇 |
1988年 | 2201篇 |
1987年 | 1479篇 |
1986年 | 1535篇 |
1985年 | 1111篇 |
1984年 | 1177篇 |
1983年 | 524篇 |
1982年 | 1016篇 |
1981年 | 822篇 |
1980年 | 833篇 |
1979年 | 567篇 |
1978年 | 554篇 |
1977年 | 653篇 |
1976年 | 1065篇 |
1972年 | 537篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
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
132.
Ming Zhao WANG Guan Liang CAI Ling XIA Jun Jian YAO Hong Yan CHEN Zhao Xing MENG Bo Li LIUDepartment of Chemistry Beijing Normal University Beijing Chemical Defense Institute PLA Beijing 《中国化学快报》2004,15(4):495-497
The crystal structures of two potential tumor imaging agents and therapeutic agents -copper(Ⅱ) complexes with salicylidene-tyrosinato Schiff base and nitrogen-donor chelating Lewis base, [Cu(sal-tyr)(bipy)] 1 and [Cu(sal-tyr)(phen)]2CH3OH 2 are presented. Our work is helpful to get deep understanding of novel 64Cu tumor imaging agents and therapeutic agents. 相似文献
133.
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
134.
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
135.
136.
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
137.
We prove here that the surface of the regular icosahedron can be triangulated with 8
non-obtuse and with 12 acute triangles. We also show these numbers to be smallest
possible. 相似文献
138.
Robert Krauthgamer Nathan Linial Avner Magen 《Discrete and Computational Geometry》2004,31(3):339-356
The extensive study of metric spaces and their embeddings
has so far focused on embeddings that preserve pairwise distances.
A very intriguing concept introduced by Feige
allows us to quantify the extent to which larger
structures are preserved by a given embedding.
We investigate this concept, focusing on several major graph families
such as paths, trees, cubes, and expanders.
We find some similarities to the regular (pairwise) distortion,
as well as some striking differences. 相似文献
139.
S. Aravinda N. Shamala Rituparna S. Roy P Balaram 《Journal of Chemical Sciences》2003,115(5-6):373-400
An overview of the use of non-protein amino acids in the design of conformationally well-defined peptides, based on work from
the author’s laboratory, is discussed. The crystal structures of several designed oligopeptides illustrate the useα-aminoisobutyric acid (Aib) in the construction of helices, D-amino acids in the design of helix termination segments andDPro-Xxx segments for nucleating ofβ-hairpin structures.β- andγ-amino acid residues have been used to expand the range of designed polypeptide structures.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献
140.
In this paper, we study the stability conditions of the MMAP[K]/G[K]/1/LCFS preemptive repeat queue. We introduce an embedded Markov chain of matrix M/G/1 type with a tree structure and identify conditions for the Markov chain to be ergodic. First, we present three conventional methods for the stability problem of the queueing system of interest. These methods are either computationally demanding or do not provide accurate information for system stability. Then we introduce a novel approach that develops two linear programs whose solutions provide sufficient conditions for stability or instability of the queueing system. The new approach is numerically efficient. The advantages and disadvantages of the methods introduced in this paper are analyzed both theoretically and numerically. 相似文献