全文获取类型
收费全文 | 123808篇 |
免费 | 20176篇 |
国内免费 | 12848篇 |
专业分类
化学 | 84467篇 |
晶体学 | 1390篇 |
力学 | 8176篇 |
综合类 | 777篇 |
数学 | 14406篇 |
物理学 | 47616篇 |
出版年
2024年 | 412篇 |
2023年 | 2414篇 |
2022年 | 4123篇 |
2021年 | 4619篇 |
2020年 | 4885篇 |
2019年 | 4826篇 |
2018年 | 4099篇 |
2017年 | 3818篇 |
2016年 | 6020篇 |
2015年 | 5746篇 |
2014年 | 7005篇 |
2013年 | 8992篇 |
2012年 | 10916篇 |
2011年 | 11175篇 |
2010年 | 7567篇 |
2009年 | 7154篇 |
2008年 | 7677篇 |
2007年 | 6975篇 |
2006年 | 6407篇 |
2005年 | 5487篇 |
2004年 | 4199篇 |
2003年 | 3444篇 |
2002年 | 3364篇 |
2001年 | 2856篇 |
2000年 | 2329篇 |
1999年 | 2576篇 |
1998年 | 2160篇 |
1997年 | 1999篇 |
1996年 | 2140篇 |
1995年 | 1722篇 |
1994年 | 1632篇 |
1993年 | 1310篇 |
1992年 | 1208篇 |
1991年 | 1122篇 |
1990年 | 898篇 |
1989年 | 621篇 |
1988年 | 525篇 |
1987年 | 412篇 |
1986年 | 418篇 |
1985年 | 355篇 |
1984年 | 262篇 |
1983年 | 172篇 |
1982年 | 152篇 |
1981年 | 115篇 |
1980年 | 80篇 |
1979年 | 46篇 |
1978年 | 34篇 |
1976年 | 36篇 |
1975年 | 33篇 |
1974年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
王巨平 《中国科学A辑(英文版)》2002,45(7):827-835
This paper verifies the singularity conjecture for Jacobi forms with higher degree in some typical cases, and gives constructions
for the Jacobi cusp forms whose Fourier coefficients can be expressed by some kind of Rankin-typeL-series. 相似文献
22.
Mingxin Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):424-436
This paper deals with positive solutions of degenerate and quasilinear parabolic systems not in divergence form: ut=up(Δu+av), vt=vq(Δv+bu), with null Dirichlet boundary conditions and positive initial conditions, where p, q, a and b are all positive constants. The local existence and uniqueness of classical solution are proved. Moreover, it will be proved that all solutions exist globally if and only if ab?λ12, where λ1 is the first eigenvalue of −Δ in Ω with homogeneous Dirichlet boundary condition. 相似文献
23.
By further generalizing the skew-symmetric triangular splitting iteration method studied by Krukier, Chikina and Belokon (Applied Numerical Mathematics, 41 (2002), pp. 89–105), in this paper, we present a new iteration scheme, called the modified skew-Hermitian triangular splitting iteration method, for solving the strongly non-Hermitian systems of linear equations with positive definite coefficient matrices. We discuss the convergence property and the optimal parameters of this new method in depth. Moreover, when it is applied to precondition the Krylov subspace methods like GMRES, the preconditioning property of the modified skew-Hermitian triangular splitting iteration is analyzed in detail. Numerical results show that, as both solver and preconditioner, the modified skew-Hermitian triangular splitting iteration method is very effective for solving large sparse positive definite systems of linear equations of strong skew-Hermitian parts. 相似文献
24.
Inspired by the recent work [HHM03], we prove two stability results for compact Riemannian manifolds with nonzero parallel spinors. Our first result says that Ricci flat metrics which also admit nonzero parallel spinors are stable (in the direction of changes in conformal structures) as the critical points of the total scalar curvature functional. Our second result, which is a local version of the first one, shows that any metric of positive scalar curvature cannot lie too close to a metric with nonzero parallel spinor. We also prove a rigidity result for special holonomy metrics. In the case of SU(m) holonomy, the rigidity result implies that scalar flat deformations of Calabi-Yau metric must be Calabi-Yau. Finally we explore the connection with a positive mass theorem of [D03], which presents another approach to proving these stability and rigidity results. Dedicated to Jeff Cheeger for his sixtieth birthday 相似文献
25.
The Iyengar Type Inequalities with Exact Estimations and the Chebyshev Central Algorithms of Integrals 总被引:3,自引:0,他引:3
Xing Hua WANG Shi Jun YANG 《数学学报(英文版)》2005,21(6):1361-1376
In this paper, both low order and high order extensions of the Iyengar type inequality are obtained. Such extensions are the best possible in the same sense as that of the Iyengar inequality. hzrthermore, the Chebyshev central algorithms of integrals for some function classes and some related problems are also considered and investigated. 相似文献
26.
In this paper, the transformation processes of two types of bis(8-hydroxyquinoline)zinc: Znq2 dihydrate and anhydrous (Znq2)4 were investigated by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG). The effects of crystal structure on optical properties of bis(8-hydroxyquinoiline)zinc were analyzed. Znq2 dihydrate can be transformed into anhydrous (Znq2)4 during heating under vacuum. Reversal transformation occurs by the interaction between chloroform and (Znq2)4. But (Znq2)4 was partially transformed into Znq2 dihydrate by the interaction between ethanol and (Znq2)4. The different molecular structure results in different crystal stacking and electronic structure, thereby affect its optical properties. 相似文献
27.
Geng Sheng WANG 《数学学报(英文版)》2005,21(5):1005-1014
This work is concerned with Pontryagin's maximum principle of optimal control problems governed by some non-well-posed semilinear heat equations. A type of approach to the non-well-posed optimal control problem is given. 相似文献
28.
Yan WANG Rong Quan FENG 《数学学报(英文版)》2005,21(4):773-778
A Cayley map is a Cayley graph embedded in an orientable surface such that. the local rotations at every vertex are identical. In this paper, balanced regular Cayley maps for cyclic groups, dihedral groups, and generalized quaternion groups are classified. 相似文献
29.
Mo2Ni3Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo2Ni3Si primary dendrites and the interdendritic Mo2Ni3Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo2Ni3Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance. 相似文献
30.