全文获取类型
收费全文 | 40769篇 |
免费 | 9726篇 |
国内免费 | 1441篇 |
专业分类
化学 | 44847篇 |
晶体学 | 384篇 |
力学 | 666篇 |
数学 | 2406篇 |
物理学 | 3633篇 |
出版年
2023年 | 39篇 |
2022年 | 108篇 |
2021年 | 309篇 |
2020年 | 1351篇 |
2019年 | 2668篇 |
2018年 | 1096篇 |
2017年 | 722篇 |
2016年 | 3512篇 |
2015年 | 3647篇 |
2014年 | 3611篇 |
2013年 | 4383篇 |
2012年 | 3457篇 |
2011年 | 2679篇 |
2010年 | 3120篇 |
2009年 | 3055篇 |
2008年 | 2765篇 |
2007年 | 2093篇 |
2006年 | 1774篇 |
2005年 | 1916篇 |
2004年 | 1669篇 |
2003年 | 1520篇 |
2002年 | 2163篇 |
2001年 | 1483篇 |
2000年 | 1381篇 |
1999年 | 451篇 |
1998年 | 124篇 |
1997年 | 89篇 |
1996年 | 94篇 |
1995年 | 73篇 |
1994年 | 74篇 |
1993年 | 70篇 |
1992年 | 46篇 |
1991年 | 37篇 |
1990年 | 43篇 |
1989年 | 34篇 |
1988年 | 18篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 23篇 |
1984年 | 11篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1974年 | 18篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
141.
142.
Jian‐guo Tang 《Mathematical Methods in the Applied Sciences》2006,29(11):1327-1338
An implicit iterative method is applied to solving linear ill‐posed problems with perturbed operators. It is proved that the optimal convergence rate can be obtained after choosing suitable number of iterations. A generalized Morozov's discrepancy principle is proposed for the problems, and then the optimal convergence rate can also be obtained by an a posteriori strategy. The convergence results show that the algorithm is a robust regularization method. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
143.
This paper is devoted to the proof of almost global existence results for Klein‐Gordon equations on Zoll manifolds (e.g., spheres of arbitrary dimension) with Hamiltonian nonlinearities, when the Cauchy data are smooth and small. The proof relies on Birkhoff normal form methods and on the specific distribution of eigenvalues of the Laplacian perturbed by a potential on Zoll manifolds. © 2007 Wiley Periodicals, Inc. 相似文献
144.
145.
The single-phase diluted magnetic Fe-ion (5%) doped ZnO powders were prepared by solid-state reaction method. The powders were annealed in Ar or Ar/H2(5%) atmosphere at 1200 °C. The crystal structure, electric and magnetic properties for the Zn0.95Fe0.05O powders have been studied with X-ray diffraction (XRD) vibrating sample magnetometer, resistance and Hall measurement. All the peaks for the XRD pattern of samples belong to the hexagonal (P63mc) lattice of ZnO, and no indication of a secondary phase. The lattice parameters for the Zn0.95Fe0.05O with an annealing in Ar/H2(5%) atmosphere were a0=3.256 Å and c0=5.206 Å at room temperature. The hysteresis curve for the Zn0.95Fe0.05O at room temperature was enhanced ferromagnetic behaviour with an annealing in Ar/H2(5%) atmosphere. We give an explanation for enhanced ferromagnetic behaviour with H2 treatment by electric properties. 相似文献
146.
147.
This paper presents a new scheduling method for manufacturing system based on the Timed Petri Net model and a reactive fast graph search algorithm. The following two typical problems are addressed in this paper. (1) Minimization of the maximum completion time. (2) Minimization of the total tardiness. As for the problem (1), a new search algorithm which combines the RTA∗ and a rule-based supervisor is proposed. As for problem (2), the original Petri Net model is converted to its reverse model and the algorithm developed for the problem (1) is applied, regarding the due date as the starting time in the reverse model. Some numerical experiments are carried out to demonstrate usefulness of our algorithm. 相似文献
148.
149.
150.
In this paper, we analyze the manufacturing lead time in a production system with BMAP (Batch Markovian Arrival process) input and post-operation operated under the N-policy. We use the factorization principle to derive the waiting time distribution (hence the manufacturing lead time) and the mean performance measures. A numerical example is provided. 相似文献