全文获取类型
收费全文 | 6044篇 |
免费 | 200篇 |
国内免费 | 16篇 |
专业分类
化学 | 4503篇 |
晶体学 | 52篇 |
力学 | 73篇 |
数学 | 901篇 |
物理学 | 731篇 |
出版年
2021年 | 69篇 |
2020年 | 70篇 |
2019年 | 70篇 |
2018年 | 44篇 |
2017年 | 50篇 |
2016年 | 139篇 |
2015年 | 124篇 |
2014年 | 137篇 |
2013年 | 226篇 |
2012年 | 293篇 |
2011年 | 322篇 |
2010年 | 221篇 |
2009年 | 217篇 |
2008年 | 308篇 |
2007年 | 249篇 |
2006年 | 283篇 |
2005年 | 234篇 |
2004年 | 247篇 |
2003年 | 190篇 |
2002年 | 177篇 |
2001年 | 106篇 |
2000年 | 84篇 |
1999年 | 82篇 |
1998年 | 81篇 |
1997年 | 85篇 |
1996年 | 89篇 |
1995年 | 82篇 |
1994年 | 79篇 |
1993年 | 67篇 |
1992年 | 69篇 |
1991年 | 76篇 |
1990年 | 59篇 |
1989年 | 60篇 |
1988年 | 64篇 |
1987年 | 56篇 |
1986年 | 67篇 |
1985年 | 89篇 |
1984年 | 97篇 |
1983年 | 59篇 |
1982年 | 76篇 |
1981年 | 96篇 |
1980年 | 75篇 |
1979年 | 68篇 |
1978年 | 84篇 |
1977年 | 48篇 |
1976年 | 75篇 |
1975年 | 57篇 |
1973年 | 58篇 |
1971年 | 42篇 |
1962年 | 36篇 |
排序方式: 共有6260条查询结果,搜索用时 78 毫秒
41.
Stefanie M. Walz Thomas E. Malner Ulrich Mueller Rolf Muelhaupt 《Journal of Polymer Science.Polymer Physics》2003,41(4):360-367
We explored phase separation and self‐assembly of perfluoroalkyl segments at the surface of polymer films obtained from latices of semifluorinated acrylate copolymers and the corresponding latex blends of nonfluorinated and semifluorinated polyacrylates. With laser‐induced secondary mass spectrometry the fluorine distribution was measured after annealing above the minimum film‐forming temperature of the polymers up to a depth of several micrometers. Depth profiles of a semifluorinated acrylate homopolymer and latex blends thereof with fluorine‐free alkylacrylates with 25, 50, and 75 mol % semifluorinated acrylate as well as a copolymer comprised of alkyl acrylate and semifluorinated acrylate (50/50 mol %) were investigated. In the case of latex blends containing both semifluorinated polyacrylates and fluorine‐free or low‐fluorine polymers, self‐assembly accounted for enrichment of the perfluoroalkyl segments at the surface. Coatings exhibiting low surface energy and having a substantially reduced total fluorine content were obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 360–367, 2003 相似文献
42.
43.
In this paper a new sheaf for topological algebras, called the sheaf of extendible ideals, is introduced. It is shown that
the sheaf space of this sheaf is uniformizable but not complete in general.
The research of both of the authors was supported by Estonian Science Foundation grant 6205. 相似文献
44.
The complete asymptotic expansion of power means in terms of Bell polynomials is obtained. Some results recently obtained by M. Bjelica are generalized. 相似文献
45.
46.
Christel Laberty Jerzy Pielaszek Pierre Alphonse Abel Rousset 《Solid State Ionics》1998,110(3-4):293-302
Cation deficient spinels NixMn3−x□3δ/4O4+δ (0≤x≤1) have been prepared by thermal decomposition of mixed oxalates Nix/3Mn(3−x)/3(C2O4)·nH2O in air at 623 K. They have been characterised by temperature programmed reduction (TPR) under H2, the reaction being followed by gravimetric and powder X-ray diffraction measurements. It has been shown that TPR proceeds in several steps. The first steps correspond to the loss of nonstoichiometric oxygen leading to the formation of a stoichiometric oxide. During the following stages the manganese cations are reduced, causing the spinel structure to be destroyed, and the formation of solid solution of NiO in a cubic MnO. Subsequently, Ni2+ cations undergo a reduction to metallic nickel, and, finally, a mixture of nonstoichiometric MnO1−δ and metallic nickel is formed. These oxides contain a high level of vacancies which vary with the nickel content with a maximum of δ≈1 near x=0.6. This nonstoichiometry is ascribed both to the presence of Ni3+ and excess of Mn4+. 相似文献
47.
Ulrich Brehm 《Geometriae Dedicata》1990,33(1):59-76
We define a fourth basic invariant, which, besides the lengths of the three sides of a triangle, determines a triangle in the complex and quaternion projective spaces P
n
and P
n
(n2) uniquely up to isometry. We give inequalities describing the exact range of the four basic invariants. We express the angular invariants of a triangle with our basic invariants, giving a new completely elementary proof of the laws of trigonometry. As a corollary we derive a large number of congruence theorems. Finally we get, in exactly the same way, the corresponding results for triangles in the complex and quaternion hyperbolic spaces H
n
and H
n
(n2). 相似文献
48.
Ulrich Koschorke 《manuscripta mathematica》1988,61(4):383-415
The geometry of two types of link homotopy invariants of a link map f:SpSqSm is discussed. The first one is the -invariant which greatly generalizes the classical notion of linking number. The second one, the -invariant, is closely related to the linking behaviour of f|sp with only the double point set of f|Sq, and therefore measures (to some extend) the obstruction to embedding Sq. These invariants are related by a Hopf invariant homomorphism. In many cases link maps are classified up to link homotopy here, and a setting is provided e.g. for future injectivity results for . Also the image of is studied, yielding an interesting double filtration of stable homotopy groups of spheres. 相似文献
49.
50.
Automated separation and measurement of radioxenon for the Comprehensive Test Ban Treaty 总被引:2,自引:0,他引:2
T. W. Bowyer K. H. Abel C. W. Hubbard A. D. McKinnon M. E. Panisko R. W. Perkins P. L. Reeder R. C. Thompson R. A. Warner 《Journal of Radioanalytical and Nuclear Chemistry》1998,235(1-2):77-82
A fully automatic radioxenon sampler/analyzer (ARSA) has been developed and demonstrated for the collection and quantitative
measurement of the four xenon radionuclides,131mXe(11.9 d),133mXe(2.2 d),133Xe(5.2 d), and135Xe(9.1 hr), in the atmosphere. These radionuclides are important signatures in monitoring for compliance to a Comprehensive
Test Ban Treaty (CTBT). Activity ratios of these radionuclides permit source attribution. Xenon, continuously and automatically
separated from the atmosphere, is automatically analyzed by electron-photon coincidence spectrometry providing a lower limit
of detection of about 100 μBq/m3. The demonstrated detection limit is about 100 times better than achievable with reported laboratory-based procedures for
the short-time collection intervals of interest. 相似文献