全文获取类型
收费全文 | 77913篇 |
免费 | 5599篇 |
国内免费 | 9287篇 |
专业分类
化学 | 63962篇 |
晶体学 | 823篇 |
力学 | 1186篇 |
综合类 | 918篇 |
数学 | 9097篇 |
物理学 | 16813篇 |
出版年
2024年 | 157篇 |
2023年 | 907篇 |
2022年 | 3624篇 |
2021年 | 3094篇 |
2020年 | 2479篇 |
2019年 | 2210篇 |
2018年 | 1810篇 |
2017年 | 1971篇 |
2016年 | 2549篇 |
2015年 | 2378篇 |
2014年 | 2727篇 |
2013年 | 5336篇 |
2012年 | 3796篇 |
2011年 | 3747篇 |
2010年 | 3232篇 |
2009年 | 4180篇 |
2008年 | 4304篇 |
2007年 | 4627篇 |
2006年 | 3766篇 |
2005年 | 3083篇 |
2004年 | 3108篇 |
2003年 | 2839篇 |
2002年 | 5074篇 |
2001年 | 2422篇 |
2000年 | 1979篇 |
1999年 | 1728篇 |
1998年 | 1614篇 |
1997年 | 1255篇 |
1996年 | 1271篇 |
1995年 | 1185篇 |
1994年 | 1145篇 |
1993年 | 1018篇 |
1992年 | 969篇 |
1991年 | 650篇 |
1990年 | 542篇 |
1989年 | 514篇 |
1988年 | 463篇 |
1987年 | 333篇 |
1986年 | 327篇 |
1985年 | 409篇 |
1984年 | 323篇 |
1983年 | 181篇 |
1982年 | 361篇 |
1981年 | 541篇 |
1980年 | 483篇 |
1979年 | 517篇 |
1978年 | 411篇 |
1977年 | 300篇 |
1976年 | 269篇 |
1973年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Here we prove that every compact differential manifold has a smooth algebraic model defined over Q. In dimension 2 we find an algebraic model (may be singular) defined over Q and birational over Q to the projective plane. 相似文献
162.
We consider a two-dimensional Coulomb gas of positive and negative pointlike unit charges interacting via a logarithmic potential. The density (rather than the charge) correlation functions are studied. In the bulk, the form-factor theory of an equivalent sine-Gordon model is used to determine the density correlation length. At the surface of a rectilinear plain wall, the universality of the asymptotic behavior of the density correlations is suggested. A scaling analysis implies a local form of the compressibility sum rule near a hard wall. A symmetry of the Coulomb system with respect to the Möbius conformal transformation, which induces a gravitational source acting on the particle density, is established. Among the consequences, a universal term of the finite-size expansion of the grand potential is derived exactly for a disk geometry of the confining domain. 相似文献
163.
Robert J. Daverman 《Topology and its Applications》2007,155(2):105-111
This paper sets forth three mismatch properties, strictly ordered in strength, about sewings of crumpled n-cubes. The strongest is a sufficient but not a necessary condition for a sewing to yield Sn, and the weakest, a necessary but not sufficient one. We show that when both crumpled cubes satisfies the Disjoint Disks Property, then the weakest property implies the sewing yields Sn, and we also show that the intermediate property leads to the same conclusion when just one of the crumpled cubes possesses the Disjoint Disks Property. In addition, we develop examples that confirm sharpness of the relevant Disjoint Disks conditions. 相似文献
164.
Dmitry Yu. Murzin 《Reaction Kinetics and Catalysis Letters》2007,90(2):225-232
Reaction route analysis is applied to visualize reaction networks in several heterogeneous catalytic reactions. Combination
of the theory of complex reactions with the notion of catalytic cycles results in a topological representation of complex
mechanisms with the nodes comprising all possible surface species including free sites and branches indicating interconnections
between reactions. 相似文献
165.
Ronald Ortner 《Operations Research Letters》2007,35(5):619-626
In ergodic MDPs we consider stationary distributions of policies that coincide in all but n states, in which one of two possible actions is chosen. We give conditions and formulas for linear dependence of the stationary distributions of n+2 such policies, and show some results about combinations and mixtures of policies. 相似文献
166.
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
167.
Dielectric relaxation study of the binary mixtures of poly(vinyl pyrrolidone) (PVP) (Mw=24000, 40000 and 360000 g mol−1) with ethyl alcohol (EA) and poly(ethylene glycol)s (PEGs) (Mw=200 and 400 g mol−1) in dilute solutions of dioxane were carried out at 10.1 GHz and 35°C. The relaxation time of PVP-EA mixtures was interpreted
by the consideration of a wait-and-switch model in the local structure of self-associated ethyl alcohol molecules and also
the PVP chain length as a geometric constraint for the reorientational motion of ethyl alcohol molecules. The formation of
complexes and effect of PVP chain length on the molecular dynamics, chain flexibility and stretching of PEG molecules in PVP-PEG
mixtures were explored from the comparative values of dielectric relaxation time. Further, relaxation time values in dioxane
and benzene solvent confirm the viscosity independent molecular dynamics in PVP-EA mixtures but the values vary significantly
with the non-polar solvent environment. 相似文献
168.
Michael J. Puls 《Archiv der Mathematik》2007,88(6):500-506
Let p be a real number greater than one. In this paper we study the vanishing and nonvanishing of the first L
p
-cohomology space of some groups that have one end. We also make a connection between the first L
p
-cohomolgy space and the Floyd boundary of the Cayley graph of a group. We apply the result about Floyd boundaries to show
that there exists a real number p such that the first L
p
-cohomology space of a nonelementary hyperbolic group does not vanish.
Received: 4 August 2006 Revised: 2 November 2006 相似文献
169.
Solubility of carbon dioxide in aqueous solutions of sodium chloride: Experimental results and correlation 总被引:2,自引:0,他引:2
The solubility of carbon dioxide in aqueous solutions of sodium chloride was measured in the temperature range from 40 to 160°C, up to 6 mol-kg salt solutions and total pressures up to 10 MPa. Pitzer's(1) equations as well as the Chen and Evans(2) model were used to correlate the new data. Results are reported and compared to literature data and correlations. 相似文献
170.
Jean-Marie Lehn 《Journal of Chemical Sciences》1994,106(5):915-922
The article discusses molecular recognition and overviews the key concepts -storage and retrieval of chemical information
by molecular structures, supramolecular reagents and catalysts, molecular transport, semiochemistry and self assembly. The
prospects of controlling supramolecular architecture through engineered molecular recognition and design of ‘programmed systems’
controlled by molecular information are also discussed. 相似文献