全文获取类型
收费全文 | 42810篇 |
免费 | 2766篇 |
国内免费 | 2052篇 |
专业分类
化学 | 22384篇 |
晶体学 | 240篇 |
力学 | 4182篇 |
综合类 | 578篇 |
数学 | 10166篇 |
物理学 | 10078篇 |
出版年
2024年 | 69篇 |
2023年 | 399篇 |
2022年 | 1120篇 |
2021年 | 1118篇 |
2020年 | 1065篇 |
2019年 | 1037篇 |
2018年 | 932篇 |
2017年 | 1184篇 |
2016年 | 1585篇 |
2015年 | 1184篇 |
2014年 | 1754篇 |
2013年 | 2971篇 |
2012年 | 2382篇 |
2011年 | 2246篇 |
2010年 | 1945篇 |
2009年 | 2425篇 |
2008年 | 2415篇 |
2007年 | 2763篇 |
2006年 | 2272篇 |
2005年 | 2039篇 |
2004年 | 1994篇 |
2003年 | 1664篇 |
2002年 | 1276篇 |
2001年 | 1046篇 |
2000年 | 1019篇 |
1999年 | 929篇 |
1998年 | 852篇 |
1997年 | 775篇 |
1996年 | 689篇 |
1995年 | 678篇 |
1994年 | 582篇 |
1993年 | 481篇 |
1992年 | 453篇 |
1991年 | 389篇 |
1990年 | 344篇 |
1989年 | 234篇 |
1988年 | 236篇 |
1987年 | 151篇 |
1986年 | 126篇 |
1985年 | 159篇 |
1984年 | 126篇 |
1983年 | 69篇 |
1982年 | 101篇 |
1981年 | 63篇 |
1980年 | 53篇 |
1979年 | 83篇 |
1978年 | 39篇 |
1977年 | 21篇 |
1976年 | 27篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 26 毫秒
211.
Bernard Bialecki 《Numerical Algorithms》1994,8(2):167-184
Cyclic reduction and Fourier analysis-cyclic reduction (FACR) methods are presented for the solution of the linear systems which arise when orthogonal spline collocation with piecewise Hermite bicubics is applied to boundary value problems for certain separable partial differential equations on a rectangle. On anN×N uniform partition, the cyclic reduction and Fourier analysis-cyclic reduction methods requireO(N
2log2
N) andO(N
2log2log2
N) arithmetic operations, respectively. 相似文献
212.
Hiroshi Ito Masaki Okazaki Dolores C. Miller 《Journal of polymer science. Part A, Polymer chemistry》2004,42(6):1478-1505
Radical copolymerizations of electron‐deficient 2‐trifluoromethylacrylic (TFMA) monomers, such as 2‐trifluoromethylacrylic acid and t‐butyl 2‐trifluoromethylacrylate (TBTFMA), with electron‐rich norbornene derivatives and vinyl ethers with 2,2′‐azobisisobutyronitrile as the initiator were investigated in detail through the analysis of the kinetics in situ with 1H NMR and through the determination of the monomer reactivity ratios. The norbornene derivatives used in this study included bicyclo[2.2.1]hept‐2‐ene (norbornene) and 5‐(2‐trifluoromethyl‐1,1,1‐trifluoro‐2‐hydroxylpropyl)‐2‐norbornene. The vinyl ether monomers were ethyl vinyl ether, t‐butyl vinyl ether, and 3,4‐dihydro‐2‐H‐pyran. Vinylene carbonate was found to copolymerize with TBTFMA. Although none of the monomers underwent radical homopolymerization under normal conditions, they copolymerized readily, producing a copolymer containing 60–70 mol % TFMA. The copolymerization of the TFMA monomer with norbornenes and vinyl ethers deviated from the terminal model and could be described by the penultimate model. The copolymers of TFMA reported in this article were evaluated as chemical amplification resist polymers for the emerging field of 157‐nm lithography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1478–1505, 2004 相似文献
213.
C. D. Bisbos 《Optimization Letters》2007,1(1):101-109
Limit and shakedown analysis problems of Computational Mechanics lead to convex optimization problems, characterized by linear objective functions, linear equality constraints and constraints expressing the restrictions imposed by the material strength. It is shown that two important strength criteria, the Mohr–Coulomb and the Tresca criterion, can be represented as systems of semidefinite constraints, leading this way to semidefinite programming problems. 相似文献
214.
215.
Closed series solution of electromagnetic scattering by an eccentric coated cylinder is achieved in matrix form. Diffracted field patterns are examined for an incident plane transverse magnetic (TM) wave. The solution is found by the classical separation of variables technique and the translational addition theorems. Wave transformation and orthogonality of the complex exponentials are employed to produce an infinite series. Numerical results are then shown by shortening the infinite series to a limited number of terms. Solutions are discussed for a dielectric or a metamaterial coating. 相似文献
216.
A new consistency measure, the harmonic consistency index, is obtained for any positive reciprocal matrix in the analytic hierarchy process. We show how this index varies with changes in any matrix element. A tight upper bound is provided for this new consistency measure when the entries of matrix are at most 9, as is often recommended. Using simulation, the harmonic consistency index is shown to give numerical values similar to the standard consistency index but it is easier to compute and interpret. In addition, new properties of the column sums of reciprocal matrices are obtained. 相似文献
217.
为了研究排球比赛中的二传最优过程 ,本文基于决策论的理论和方法建立了排球二传最优过程的数学模型 .通过对模型的分析研究分别给出了最大概率准则和最大期望准则下的最优传球方式 .本文所得到的结果对排球队的训练和比赛有一定的指导意义 . 相似文献
218.
219.
Genetic algorithms are stochastic search algorithms that have been applied to optimization problems. In this paper we analyze the run-time complexity of a genetic algorithm when we are interested in one of a set of distinguished solutions. One such case occurs when multiple optima exist. We define the worst case scenario and derive a probabilistic worst case bound on the number of iterations required to find one of these multiple solutions of interest. 相似文献
220.