全文获取类型
收费全文 | 4970篇 |
免费 | 474篇 |
国内免费 | 476篇 |
专业分类
化学 | 419篇 |
晶体学 | 8篇 |
力学 | 387篇 |
综合类 | 104篇 |
数学 | 4170篇 |
物理学 | 832篇 |
出版年
2024年 | 7篇 |
2023年 | 64篇 |
2022年 | 50篇 |
2021年 | 103篇 |
2020年 | 142篇 |
2019年 | 155篇 |
2018年 | 151篇 |
2017年 | 186篇 |
2016年 | 170篇 |
2015年 | 127篇 |
2014年 | 210篇 |
2013年 | 506篇 |
2012年 | 210篇 |
2011年 | 231篇 |
2010年 | 199篇 |
2009年 | 279篇 |
2008年 | 344篇 |
2007年 | 310篇 |
2006年 | 269篇 |
2005年 | 278篇 |
2004年 | 221篇 |
2003年 | 224篇 |
2002年 | 231篇 |
2001年 | 156篇 |
2000年 | 168篇 |
1999年 | 142篇 |
1998年 | 137篇 |
1997年 | 133篇 |
1996年 | 95篇 |
1995年 | 79篇 |
1994年 | 64篇 |
1993年 | 54篇 |
1992年 | 27篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 23篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 4篇 |
1936年 | 3篇 |
排序方式: 共有5920条查询结果,搜索用时 31 毫秒
121.
122.
Let (X, d, μ) be a metric measure space with non-negative Ricci curvature. This paper is concerned with the boundary behavior of harmonic function on the (open) upper half-space . We derive that a function f of bounded mean oscillation (BMO) is the trace of harmonic function on , whenever u satisfies the following Carleson measure condition where denotes the total gradient and denotes the (open) ball centered at with radius . Conversely, the above condition characterizes all the harmonic functions whose traces are in BMO space. 相似文献
123.
Inverse gas chromatography (IGC) was used to determine the dispersive component of the free energy as well as the acid-base properties of cellulose fibre surfaces, before and after modification by corona treatment. It was found that the corona treatment increases both the dispersive contribution to surface energy and its acidic character, whereas only a slight increase in its basicity was observed. It was also found that some chemical degradation of the surface occurs at high corona currents. The extent of modification of the surface properties, as revealed by IGC, was correlated to the surface chemical composition deduced from XPS analysis as well as with the electrical conductance and the pH of the water suspensions of the cellulose fibres. 相似文献
124.
CHAOS FOR MIXING TRANSFORMATIONS 总被引:3,自引:0,他引:3
Liao Gongfu 《数学年刊B辑(英文版)》1994,15(4):501-506
CHAOSFORMIXINGTRANSFORMATIONS¥LIAOGONGFU(DepartmentofMathematics,JilinUniversity,Changchun130023,China.)Abstract:Foraclassofm... 相似文献
125.
D. H. Fremlin R. A. Johnson E. Wajch 《Proceedings of the American Mathematical Society》1996,124(9):2897-2903
A space Borel multiplies with a space if each Borel set of is a member of the -algebra in generated by Borel rectangles. We show that a regular space Borel multiplies with every regular space if and only if has a countable network. We give an example of a Hausdorff space with a countable network which fails to Borel multiply with any non-separable metric space. In passing, we obtain a characterization of those spaces which Borel multiply with the space of countable ordinals, and an internal necessary and sufficient condition for to Borel multiply with every metric space.
126.
Christian Remling 《Proceedings of the American Mathematical Society》1996,124(7):2097-2100
In 1949, Hartman and Wintner showed that if the eigenvalue equations of a one-dimensional Schrödinger operator possess square integrable solutions, then the essential spectrum is nowhere dense. Furthermore, they conjectured that this statement could be improved and that under this condition the essential spectrum might always be void. This is shown to be false. It is proved that, on the contrary, every closed, nowhere dense set does occur as the essential spectrum of Schrödinger operators which satisfy the condition of existence of -solutions. The proof of this theorem is based on inverse spectral theory.
127.
Bolis Basit Hans Gü nzler 《Transactions of the American Mathematical Society》1996,348(11):4489-4500
Let be a semigroup and a topological space. Let be an Abelian topological group. The right differences of a function are defined by for . Let be continuous at the identity of for all in a neighbourhood of . We give conditions on or range under which is continuous for any topological space . We also seek conditions on under which we conclude that is continuous at for arbitrary . This led us to introduce new classes of semigroups containing all complete metric and locally countably compact quasitopological groups. In this paper we study these classes and explore their relation with Namioka spaces.
128.
An estimation of the mass difference of
system with heavy quark symmetry formalism is presented. The effective Hamiltonian describing the transition
(whereh=b forB
d
0
-system) is considered in a manifest left right symmetric (MLRS) model along with contribution from neutral Higgs boson. We
use the spin and flavor symmetry for heavy quarks to obtain the transition matrix element 〈B
d
0
|ℋeff(x)|
d
0
〉 in terms of Isgur-Wise function. Assuming thatB
d
0
and
states are at rest, we find that Isgur-Wise function turns out to be unity. However using the experimental values of ΔM
K and
as input, we find thatM
R=835 GeV andM
H⩾2·9 TeV. 相似文献
129.
Takashi Koda 《Annals of Global Analysis and Geometry》1993,11(4):323-329
Bérard-Bergery has constructed a non-Kähler Einstein Hermitian metricg with positive scalar curvature on
. We prove thatg is a weakly *-Einstein metric with nonconstant positive *-scalar curvature.This research is partially supported by the Grand-in-Aid for Scientific Research (No. 03740022), the Ministry of Education, Science and Culture. 相似文献
130.
A model, based on inverse gas chromatography experiments, has been developed for intermolecular interaction and its temperature dependence. The model ascribes to each substance a four-component solubility parameter; the four components reflect the van der Waals, polar, electron donor, and electron acceptor interactive properties. Their values depend on temperature in the same manner as does the cohesive energy. The latter was found to depend only on the critical temperature, the acentric factor, and the reduced temperature. The model was used for evaluation of the solubility parameters from polymer-solvent interaction coefficients and their temperature dependence with high accuracy. For binary solventsolvent mixtures, the free energy of mixing and its temperature dependence, as well as enthalpy of mixing can be derived from this model with a good accuracy. 相似文献