全文获取类型
收费全文 | 29767篇 |
免费 | 204篇 |
国内免费 | 359篇 |
专业分类
化学 | 11211篇 |
晶体学 | 272篇 |
力学 | 1408篇 |
综合类 | 15篇 |
数学 | 9095篇 |
物理学 | 8329篇 |
出版年
2022年 | 39篇 |
2021年 | 58篇 |
2020年 | 53篇 |
2019年 | 58篇 |
2018年 | 1224篇 |
2017年 | 1471篇 |
2016年 | 747篇 |
2015年 | 595篇 |
2014年 | 504篇 |
2013年 | 692篇 |
2012年 | 3191篇 |
2011年 | 2351篇 |
2010年 | 1845篇 |
2009年 | 1574篇 |
2008年 | 605篇 |
2007年 | 644篇 |
2006年 | 640篇 |
2005年 | 4482篇 |
2004年 | 3934篇 |
2003年 | 2318篇 |
2002年 | 530篇 |
2001年 | 343篇 |
2000年 | 130篇 |
1999年 | 205篇 |
1998年 | 125篇 |
1997年 | 88篇 |
1996年 | 70篇 |
1995年 | 61篇 |
1994年 | 54篇 |
1992年 | 183篇 |
1991年 | 167篇 |
1990年 | 144篇 |
1989年 | 114篇 |
1988年 | 108篇 |
1987年 | 57篇 |
1986年 | 46篇 |
1985年 | 42篇 |
1984年 | 30篇 |
1983年 | 30篇 |
1979年 | 30篇 |
1976年 | 79篇 |
1975年 | 37篇 |
1974年 | 41篇 |
1973年 | 49篇 |
1972年 | 41篇 |
1970年 | 36篇 |
1969年 | 39篇 |
1968年 | 35篇 |
1967年 | 33篇 |
1966年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
Some equivalent characterizations for a skew group ring to be a Dubrovin valuation ring are given. Among them all the prime
ideals of a Dubrovin valuation skew group ring are characterised.
Received June 8, 1999, Revised June 4, 2001, Accepted July 20, 2001 相似文献
982.
Predrag?S.?Stanimirovi?Email author Milan?B.?Tasi? 《Journal of Applied Mathematics and Computing》2002,9(2):349-359
We investigate implementation of the determinantal representation of generalized inverses for complex and rational matrices in the symbolic package MATHEMATICA. We also introduce an implementation which is applicable to sparse matrices. 相似文献
983.
It is well known that the-Walsh-Fourier expansion of a function from the block space ([0, 1 ) ), 1 <q≤∞, converges pointwise a.e. We prove that the same result is true for the expansion of a function from in certain periodixed smooth periodic non-stationary wavelet packets bases based on the Haar filters. We also consider wavelet packets based on the Shannon filters and show that the expansion of Lp-functions, 1<p<∞, converges in norm and pointwise almost everywhere. 相似文献
984.
In the fifties, Calderón established a formal relation between symbol and kernel distribution, but it is difficult to establish an intrinsic relation. The Calderón-Zygmund (C-Z) school studied the C-Z operators, and Hörmander, Kohn and Nirenberg, et al. studied the symbolic operators. Here we apply a refinement of the Littlewood-Paley (L-P) decomposition, analyse under new wavelet bases, to characterize both symbolic operators spaces \({\text{OP}}S^{m}_{{1,\delta }} \) and kernel distributions spaces with other spaces composed of some almost diagonal matrices, then get an isometric between \({\text{OP}}S^{m}_{{1,\delta }} \) and kernel distribution spaces 相似文献
985.
In this paper, we prove that the set of all factorization indices of a completely positive graph has no gaps. In other words,
we give an affirmative answer to a question raised by N. Kogan and A. Berman [8] in the case of completely positive graphs.
Received December 9, 1997, Accepted May 16, 2002 相似文献
986.
In this paper, the similarity-invariant subspaces of B(H), which is the Banach algebra of all bounded linear operators on a separable infinite-dimensional Hilbert space H, are completely characterized and the representations of bounded linear maps on B(H) which preserve similarity in both directions are given.
Received November 3, 1999, Revised September 20, 2000, Accepted February 5, 2001 相似文献
987.
In this paper the transcendence of values of certain trigonometric series with algebraic coefficients and its derivatives
at algebraic points is proved under a general condition dependent only on the coefficients. The proof of the theorem is based
on a criterion for linear independence over a number field.
Received November 9, 1999, Accepted February 5, 2001 相似文献
988.
We describe a global approach to the study of duality transformations between antisymmetric fields with transitions and argue that the natural geometrical setting for the approach is that of gerbes; these objects are mathematical constructions generalizing U(1) bundles and are similarly classified by quantized charges. We address the duality maps in terms of the potentials rather than on their field strengths and show the quantum equivalence between dual theories which in turn allows a rigorous proof of a generalized Dirac quantization condition on the couplings. Our approach needs the introduction of an auxiliary form satisfying a global constraint which in the case of 1-form potentials coincides with the quantization of the magnetic flux. We apply our global approach to refine the proof of the duality equivalence between the d=11 supermembrane and d=10 IIA Dirichlet supermembrane. 相似文献
989.
990.
Florence Geneste Alec Moradpour Georges Dive Daniel Peeters Jacques Malthête Jean-Fran?ois Sadoc 《The Journal of organic chemistry》2002,67(2):605-607
The total number of possible retrosynthetic bisections of C(60) leads to nine different isometric C(30) fragments. These molecules include five chiral units, four of which derive from partitions corresponding to four distinct "Coupes du Roi". The energies, curvatures, and homodesmotic stabilization energies of the C(30) fragments are evaluated at the ab initio 6-31G level. 相似文献