全文获取类型
收费全文 | 6404篇 |
免费 | 321篇 |
国内免费 | 41篇 |
专业分类
化学 | 4942篇 |
晶体学 | 69篇 |
力学 | 219篇 |
综合类 | 1篇 |
数学 | 553篇 |
物理学 | 982篇 |
出版年
2023年 | 39篇 |
2022年 | 102篇 |
2021年 | 109篇 |
2020年 | 117篇 |
2019年 | 140篇 |
2018年 | 70篇 |
2017年 | 73篇 |
2016年 | 223篇 |
2015年 | 191篇 |
2014年 | 254篇 |
2013年 | 385篇 |
2012年 | 496篇 |
2011年 | 593篇 |
2010年 | 397篇 |
2009年 | 304篇 |
2008年 | 481篇 |
2007年 | 367篇 |
2006年 | 355篇 |
2005年 | 373篇 |
2004年 | 294篇 |
2003年 | 224篇 |
2002年 | 240篇 |
2001年 | 122篇 |
2000年 | 113篇 |
1999年 | 68篇 |
1998年 | 63篇 |
1997年 | 34篇 |
1996年 | 58篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 33篇 |
1992年 | 27篇 |
1991年 | 31篇 |
1990年 | 31篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 23篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 21篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 18篇 |
1976年 | 13篇 |
1974年 | 13篇 |
1972年 | 7篇 |
排序方式: 共有6766条查询结果,搜索用时 15 毫秒
1.
2.
Jong Uhn Kim 《Transactions of the American Mathematical Society》2002,354(3):1117-1135
In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.
3.
4.
5.
The fuzzification of convex sets in median algebras is considered, and some of their properties are investigated. A characterization of finite valued fuzzy convex set is given. 相似文献
6.
Jong Chan Lee Jin Young Park So Young Yoon Yong Hun Bae Seung Jun Lee 《Tetrahedron letters》2004,45(1):191-193
A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described. 相似文献
7.
This paper considers a receiver set partitioning and sequencing problem in a wavelength division multiplexing single-hop lightwave network for multicasting traffic. The problem is analysed in the approach of uncapacitated single batch-processing machine scheduling. In the analysis, several solution properties are characterized with respect to a mean flow time measure, based upon which two heuristic algorithms are developed, along with a dynamic programming algorithm. Several numerical experiments show that the heuristic algorithms generate good schedules. The problem is extended to consider two measures simultaneously including the mean flow time and the number of transmissions, for which the proposed algorithms also perform well. 相似文献
8.
In this paper, by extending Kucera's idea to the function field case, we obtain several determinant formulas involving the real class number and the relative class number of any subfield of cyclotomic function fields. We also provide several examples using these determinant formulas.
9.
A least‐squares meshfree method based on the first‐order velocity–pressure–vorticity formulation for two‐dimensional incompressible Navier–Stokes problem is presented. The convective term is linearized by successive substitution or Newton's method. The discretization of all governing equations is implemented by the least‐squares method. Equal‐order moving least‐squares approximation is employed with Gauss quadrature in the background cells. The boundary conditions are enforced by the penalty method. The matrix‐free element‐by‐element Jacobi preconditioned conjugate method is applied to solve the discretized linear systems. Cavity flow for steady Navier–Stokes problem and the flow over a square obstacle for time‐dependent Navier–Stokes problem are investigated for the presented least‐squares meshfree method. The effects of inaccurate integration on the accuracy of the solution are investigated. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
10.
Do W. Lee Eun Y. Seo Sung I. Cho Chae S. Yi 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2747-2755
Pyridine‐2‐carboximidates [methyl ( 1a ), ethyl ( 1b ), isopropyl ( 1c ), cyclopentyl ( 1d ), cyclohexyl ( 1e ), n‐octyl ( 1f ), and benzyl ( 1g )] were prepared from the reaction of 2‐cyanopyridine with the corresponding alcohols. Cyclopentyl‐substituted 1d was found to be a highly effective ligand for copper‐catalyzed atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). For example, the observed rate constant for a CuBr/ 1d catalytic system was found to be nearly twice as high as the cyclohexyl‐substituted CuBr/ 1e catalytic system [kobs = (1.19 vs 0.56) × 10?4 s?1). The effects of the solvents, temperature, catalyst/initiator, and solvent/monomer ratio on the ATRP of MMA were studied systematically for the CuBr/ 1d catalytic system. The optimum condition for the ATRP of MMA was found to be a 1:2:1:400 [CuBr]o/[ 1d ]o/[ethyl 2‐bromoisobutyrate]o/[MMA]o ratio at 60 °C in veratrole solution, which yielded well‐defined poly(MMA) with a narrow molecular weight distribution of 1.14. The catalytically active copper complex 2d was isolated from the reaction of CuBr with 1d . Narrow molecular weight distributions as low as 1.06 were achieved for the CuBr/ 1d catalytic system by employing 10% of the deactivator CuBr2. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2747–2755, 2004 相似文献