全文获取类型
收费全文 | 11410篇 |
免费 | 283篇 |
国内免费 | 47篇 |
专业分类
化学 | 7409篇 |
晶体学 | 132篇 |
力学 | 334篇 |
数学 | 1300篇 |
物理学 | 2565篇 |
出版年
2021年 | 109篇 |
2020年 | 183篇 |
2019年 | 171篇 |
2018年 | 104篇 |
2017年 | 82篇 |
2016年 | 190篇 |
2015年 | 161篇 |
2014年 | 202篇 |
2013年 | 520篇 |
2012年 | 521篇 |
2011年 | 644篇 |
2010年 | 300篇 |
2009年 | 296篇 |
2008年 | 536篇 |
2007年 | 539篇 |
2006年 | 553篇 |
2005年 | 458篇 |
2004年 | 418篇 |
2003年 | 369篇 |
2002年 | 337篇 |
2001年 | 209篇 |
2000年 | 233篇 |
1999年 | 116篇 |
1998年 | 114篇 |
1997年 | 108篇 |
1996年 | 152篇 |
1995年 | 120篇 |
1994年 | 173篇 |
1993年 | 197篇 |
1992年 | 180篇 |
1991年 | 132篇 |
1990年 | 132篇 |
1989年 | 141篇 |
1988年 | 112篇 |
1987年 | 134篇 |
1986年 | 126篇 |
1985年 | 205篇 |
1984年 | 168篇 |
1983年 | 111篇 |
1982年 | 138篇 |
1981年 | 128篇 |
1980年 | 144篇 |
1979年 | 139篇 |
1978年 | 137篇 |
1977年 | 119篇 |
1976年 | 137篇 |
1975年 | 124篇 |
1974年 | 136篇 |
1973年 | 137篇 |
1971年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
1.
2.
3.
Science China Chemistry - 相似文献
4.
Roberto Aravire Ahmed Laghribi Manuel ORyan 《Journal of Pure and Applied Algebra》2019,223(1):439-457
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism induced by scalar extension, where is a purely inseparable extension (of any degree), is the cokernel of the Artin–Schreier operator given by: , where is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included. 相似文献
5.
Peter T. Smith Younghoon Kim Dr. Bahiru Punja Benke Prof. Kimoon Kim Prof. Christopher J. Chang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4932-4937
We report a supramolecular strategy for promoting the selective reduction of O2 for direct electrosynthesis of H2O2. We utilized cobalt tetraphenylporphyrin (Co-TPP), an oxygen reduction reaction (ORR) catalyst with highly variable product selectivity, as a building block to assemble the permanently porous supramolecular cage Co-PB-1(6) bearing six Co-TPP subunits connected through twenty-four imine bonds. Reduction of these imine linkers to amines yields the more flexible cage Co-rPB-1(6). Both Co-PB-1(6) and Co-rPB-1(6) cages produce 90–100 % H2O2 from electrochemical ORR catalysis in neutral pH water, whereas the Co-TPP monomer gives a 50 % mixture of H2O2 and H2O. Bimolecular pathways have been implicated in facilitating H2O formation, therefore, we attribute this high H2O2 selectivity to site isolation of the discrete molecular units in each supramolecule. The ability to control reaction selectivity in supramolecular structures beyond traditional host–guest interactions offers new opportunities for designing such architectures for a broader range of catalytic applications. 相似文献
6.
7.
Graham Smith 《The Journal of the Operational Research Society》1989,40(9):761-770
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation. 相似文献
8.
A two-dimensional, nonlinear, compressible, diabatic, nonhydrostatic photochemical-dynamical gravity wave model has been advanced. The model includes diabetic process produced by photochemistry and the effect of gravity wave on atmospheric chemical species. In the horizontal direction, the pseudospectral method is used. The finite difference approximations are used in vertical direction z and time t. The FICE method is used to solve the model. The model results on small amplitude fluctuation are very close to those of linear theory, which demonstrates the correctness of the model.
相似文献9.
For a ? R\alpha \in \mathbf{R}, the class of a-\alpha -order spherical harmonic functions in an open set W í\Omega \subseteq Sn-1\mathbf{S}^{n-1}, Ha(W)H^{\alpha }(\Omega ) is defined as the C2-C^{2}-solutions of Dau=0\Delta _{\alpha }u=0; where Da=Ds+a(n+a-2)\Delta _{\alpha }=\Delta _{s}+\alpha (n+\alpha -2) is the spherical Laplace--Beltrami operator of order a\alpha and Ds\Delta _{s} is the radially independent part of the Laplace operator. We obtain a Green's integral formula for the functions in Ha(W)H^{\alpha }(\Omega ) with kernel expressed as a Gegenbauer function. As generalizations, higher order spherical iterated Dirac operators are defined in a polynomial form. Integral representations of the null solutions to these operators and an intertwining formula relating these operators on the sphere and their analogues in Euclidean space are presented. 相似文献
10.
A nonlinear, compressible, non-isothermal gravity wave model that involves photochemistry is used to study the effects of gravity wave on atmospheric chemical species distributions in this paper. The changes in the distributions of oxygen compound and hydrogen compound density induced by gravity wave propagation are simulated. The results indicate that when a gravity wave propagates through a mesopause region, even if it does not break, it can influence the background distributions of chemical species. The effect of gravity wave on chemical species at night is larger than in daytime. 相似文献