全文获取类型
收费全文 | 16550篇 |
免费 | 1556篇 |
国内免费 | 1259篇 |
专业分类
化学 | 9498篇 |
晶体学 | 88篇 |
力学 | 59篇 |
综合类 | 60篇 |
数学 | 4890篇 |
物理学 | 1415篇 |
综合类 | 3355篇 |
出版年
2024年 | 20篇 |
2023年 | 295篇 |
2022年 | 197篇 |
2021年 | 251篇 |
2020年 | 471篇 |
2019年 | 483篇 |
2018年 | 472篇 |
2017年 | 355篇 |
2016年 | 554篇 |
2015年 | 673篇 |
2014年 | 969篇 |
2013年 | 1333篇 |
2012年 | 977篇 |
2011年 | 1133篇 |
2010年 | 1032篇 |
2009年 | 1118篇 |
2008年 | 1172篇 |
2007年 | 1145篇 |
2006年 | 888篇 |
2005年 | 669篇 |
2004年 | 637篇 |
2003年 | 637篇 |
2002年 | 577篇 |
2001年 | 390篇 |
2000年 | 381篇 |
1999年 | 322篇 |
1998年 | 298篇 |
1997年 | 206篇 |
1996年 | 211篇 |
1995年 | 232篇 |
1994年 | 192篇 |
1993年 | 139篇 |
1992年 | 145篇 |
1991年 | 84篇 |
1990年 | 74篇 |
1989年 | 66篇 |
1988年 | 65篇 |
1987年 | 39篇 |
1986年 | 36篇 |
1985年 | 59篇 |
1984年 | 46篇 |
1982年 | 53篇 |
1981年 | 40篇 |
1980年 | 30篇 |
1979年 | 36篇 |
1978年 | 34篇 |
1977年 | 25篇 |
1976年 | 29篇 |
1975年 | 19篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
111.
Common fixed-point results are established for a new class of noncommuting selfmaps. We apply them to obtain several invariant approximation results which unify, extend, and complement well-known results. 相似文献
112.
Under some general continuous and compact conditions, the existence problems of fiked points andd coupled fixed points for increasing operators are studied. an application, we utilize the results obtained to study the existence of solutions for differential inclusions in Banach spaces. 相似文献
113.
Raiko P. Zaikov 《Letters in Mathematical Physics》1994,32(4):283-297
Higher spin extensions of the non-Abelian gauge symmetries for the classical WZNW model are considered. Both linear and nonlinear realizations of the extended affine Kac-Moody algebra are obtained. It is a characteristic property of the WZNW model that it admits a higher spin linear realization of the extended affine Kac-Moody algebra which is equivalent to the corresponding higher spin nonlinear realization of the same algebra. However, in both cases, the higher spin Noether currents do not span an invariant space with respect to their generating transformations. Here, the current space is extended to an invariant space which allows us to gauge the symmetry.Supported by Bulgarian Foundation on Fundamental Research under contract Ph-318/93-95. 相似文献
114.
Ryuhei Wakita Masanori Miyakoshi Yohji Nakatsuji Mitsuo Okahara 《Journal of inclusion phenomena and macrocyclic chemistry》1991,10(1):127-139
A series of noncyclic neutral ionophores has been synthesized by the reaction of oligoethylene glycol dihalides with 8-quinolinol. Complexation properties for alkali metal picrates were evaluated from solvent extraction and bulk liquid membrane transport experiments. Complexation profiles of the newly synthesized ionophores with a hexyl chain were similar to those of their homologues without the hexyl chain in the extraction experiments. Among them, the pentaethylene glycol derivatives showed the highest extraction efficiency and selectivity towards potassium ion. From the1H NMR spectra (400 MHz), the change in chemical shifts of the aromatic protons upon the addition of alkali metal thiocyanates suggested the existence of a stabilization effect which is caused by intramolecular stacking conformations between the quinoline rings during complexation. Aryl stacking interactions depend on the size of the cations and on the chain length of the oligoethylene glycol. The relationship between transport ability towards alkali metal cations and lipophilicity of these ionophores is also discussed. 相似文献
115.
Michel Leblond 《Numerical Linear Algebra with Applications》2002,9(2):181-193
In computer graphics, in the radiosity context, a linear system Φx=b must be solved and there exists a diagonal positive matrix H such that H Φ is symmetric. In this article, we extend this property to complex matrices: we are interested in matrices which lead to Hermitian matrices under premultiplication by a Hermitian positive‐definite matrix H. We shall prove that these matrices are self‐adjoint with respect to a particular innerproduct defined on ?n. As a result, like Hermitian matrices, they have real eigenvalues and they are diagonalizable. We shall also show how to extend the Courant–Fisher theorem to this class of matrices. Finally, we shall give a new preconditioning matrix which really improves the convergence speed of the conjugate gradient method used for solving the radiosity problem. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
116.
The He1 photoelectron (PE) spectra of both 2(5H) furanone and itstrans-chair-dimeric-compound (t-c-DFN) are reported. The assignment of the PES bands is made on the basis of band shapes, the PES results of the molecules
which have the similar atomic groups, and the restricted Hartree-Fock (RHF) calculations for the molecules studied. From the
results of both PES experimental and theoretical calculations, it is proved that the ionization potential (IPS) of the HOMO
for the dimeric-compound is lower than that of the HOMO for the monomer. And the total energy computed for thet-c-DFN is the lowest in the four possible configurations of dimeric-compounds of 2(5H) furanone. Therefore the synthesis oft-c-DFN is also the easiest.
Project supported by the National Natural Science Foundation of China. 相似文献
117.
Hiroshi Sugita 《Probability Theory and Related Fields》1994,100(1):117-130
Summary We show that each holomorphic Wiener function has a skeleton which is intrinsic from several viewpoints. In particular, we study the topological aspects of the skeletons by using the local Taylor expansion for holomorphic Wiener functions.Supported in part by the Grant-in-Aid for Science Research 03740120 Min. Education 相似文献
118.
Alexander O. Smirnov 《Letters in Mathematical Physics》2006,76(2-3):297-316
We find a new class of Fuchsian equations, with algebro-geometric solutions associated to a hyperelliptic curve. A method for calculating its arithmetic genus and branching points is suggested. Numerous examples are given. 相似文献
119.
In this paper we study random orderings of the integers with a certain invariance property. We describe all such orders in a simple way. We define and represent random shuffles of a countable set of labels and then give an interpretation of these orders in terms of a class of generalized riffle shuffles. 相似文献
120.