全文获取类型
收费全文 | 489025篇 |
免费 | 3840篇 |
国内免费 | 1660篇 |
专业分类
化学 | 234609篇 |
晶体学 | 7406篇 |
力学 | 26559篇 |
综合类 | 20篇 |
数学 | 78763篇 |
物理学 | 147168篇 |
出版年
2021年 | 3504篇 |
2020年 | 3762篇 |
2019年 | 4370篇 |
2018年 | 15846篇 |
2017年 | 15558篇 |
2016年 | 14082篇 |
2015年 | 5536篇 |
2014年 | 8208篇 |
2013年 | 18238篇 |
2012年 | 17612篇 |
2011年 | 26730篇 |
2010年 | 17764篇 |
2009年 | 18275篇 |
2008年 | 21870篇 |
2007年 | 23789篇 |
2006年 | 14526篇 |
2005年 | 14421篇 |
2004年 | 14079篇 |
2003年 | 12939篇 |
2002年 | 11610篇 |
2001年 | 12088篇 |
2000年 | 9389篇 |
1999年 | 7112篇 |
1998年 | 6067篇 |
1997年 | 6047篇 |
1996年 | 5808篇 |
1995年 | 5183篇 |
1994年 | 5162篇 |
1993年 | 5165篇 |
1992年 | 5530篇 |
1991年 | 5697篇 |
1990年 | 5353篇 |
1989年 | 5373篇 |
1988年 | 5308篇 |
1987年 | 5179篇 |
1986年 | 4969篇 |
1985年 | 6497篇 |
1984年 | 6746篇 |
1983年 | 5482篇 |
1982年 | 5700篇 |
1981年 | 5568篇 |
1980年 | 5331篇 |
1979年 | 5694篇 |
1978年 | 5755篇 |
1977年 | 5764篇 |
1976年 | 5864篇 |
1975年 | 5382篇 |
1974年 | 5360篇 |
1973年 | 5501篇 |
1972年 | 3990篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献
152.
Calculations are performed, using a basis of two-center functions described previously, for excited states of the following three-and four-electron compounds: H2
–, He2
+, He2, Li2
+2. High efficiency is demonstrated for the frozen ionic core approximation and the nonorthogonal orbital method in such calculations. For four-electron systems the practical feasibility of the frozen hybrid core approximation is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 53–56, August, 1987. 相似文献
153.
K. C. Kumara Swamy E. Balaraman M. Phani Pavan N. N. Bhuvan Kumar K. Praveen Kumar N. Satish Kumar 《Journal of Chemical Sciences》2006,118(6):495-501
The diversity of products in the reaction of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) and activated
acetylenes with PIII compounds bearing oxygen or nitrogen substituents is discussed. New findings that are useful in understanding the nature
of intermediates involved in the Mitsunobu reaction are highlighted. X-ray structures of two new compounds (2-t-Bu-4-MeC6H3O)P (μ-N-t-Bu)2P+[(NH-t-Bu)N[(CO2]-i-Pr)(HNCO2-i-Pr)]](Cl-)(2-t-Bu-4-MeC6H3OH)(23)and [CH2(6-t-Bu-4-Me-C6H2O)2P(O)C(CO2Me)C-(CO2Me)CClNC(O)Cl] (33) are also reported. The structure of23 is close to one of the intermediates proposed in the Mitsunobu reaction. 相似文献
154.
155.
M. Lashkarizadeh Bami 《Semigroup Forum》2004,69(2):219-229
In the present paper it is shown that if S1 and S2 are two
Clifford topological semigroups satisfying certain conditions
and T is an isometric isomorphism of LUC(S1*) onto LUC(S2*), then T
maps S1 topologically isomorphically onto S2. Furthermore, T
maps M
l
n(S1) (M(S1), respectively) isometrically
isomorphically onto M
l
n(S2) (M(S2), respectively). Indeed,
we have obtained a generalization of a well-known result of
Ghahramani, Lau and Losert for locally compact groups to a more
general setting of Clifford topological semigroups. 相似文献
156.
The European Physical Journal C - The design constraints and the target physics performance of the ATLAS Electromagnetic Calorimeter are reviewed, and the construction status is summarized.... 相似文献
157.
S. Szegedi P. Raics M. Fayez-Hassan 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):429-433
Considering the importance of the X-ray production cross sections for the determination of the element concentrations in a
given material, we have measured them experimentally for Al Si, Sc, Ti, V, Fe, Co, Ni and Cu bombarded by protons with energies
ranging from 40 to 180 keV.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
158.
Affine Arithmetic: Concepts and Applications 总被引:2,自引:0,他引:2
Affine arithmetic is a model for self-validated numerical computation that keeps track of first-order correlations between computed and input quantities. We explain the main concepts in affine arithmetic and how it handles the dependency problem in standard interval arithmetic. We also describe some of its applications. 相似文献
159.
N. A. Lockerbie 《General Relativity and Gravitation》2004,36(3):593-600
By using a novel free-flying, rotating, optical bench aboard the International Space Station (ISS) as the basis for a measurement of differential acceleration between two gravitating bodies, in principle the Newtonian inverse-square law and the constant of gravitation, G, can be determined at the parts in 106 level. 相似文献
160.
We consider the optimal service control of a multiclass M/G/1 queueing system in which customers are served nonpreemptively and the system cost rate is additive across classes and increasing convex in the numbers present in each class. Following Whittle's approach to a class of restless bandit problems, we develop a Langrangian relaxation of the service control problem which serves to motivate the development of a class of index heuristics. The index for a particular customer class is characterised as a fair charge for service of that class. The paper develops these indices and reports an extensive numerical investigation which exhibits strong performance of the index heuristics for both discounted and average costs. 相似文献