全文获取类型
收费全文 | 128554篇 |
免费 | 21171篇 |
国内免费 | 14068篇 |
专业分类
化学 | 88142篇 |
晶体学 | 1715篇 |
力学 | 8202篇 |
综合类 | 902篇 |
数学 | 14569篇 |
物理学 | 50263篇 |
出版年
2024年 | 420篇 |
2023年 | 2430篇 |
2022年 | 4238篇 |
2021年 | 4690篇 |
2020年 | 5024篇 |
2019年 | 4990篇 |
2018年 | 4286篇 |
2017年 | 4043篇 |
2016年 | 6124篇 |
2015年 | 6042篇 |
2014年 | 7246篇 |
2013年 | 9446篇 |
2012年 | 11487篇 |
2011年 | 11721篇 |
2010年 | 7974篇 |
2009年 | 7730篇 |
2008年 | 8265篇 |
2007年 | 7463篇 |
2006年 | 6989篇 |
2005年 | 5982篇 |
2004年 | 4565篇 |
2003年 | 3606篇 |
2002年 | 3469篇 |
2001年 | 2839篇 |
2000年 | 2419篇 |
1999年 | 2573篇 |
1998年 | 2180篇 |
1997年 | 1935篇 |
1996年 | 2103篇 |
1995年 | 1696篇 |
1994年 | 1650篇 |
1993年 | 1327篇 |
1992年 | 1203篇 |
1991年 | 1107篇 |
1990年 | 874篇 |
1989年 | 627篇 |
1988年 | 520篇 |
1987年 | 421篇 |
1986年 | 419篇 |
1985年 | 362篇 |
1984年 | 267篇 |
1983年 | 180篇 |
1982年 | 157篇 |
1981年 | 126篇 |
1980年 | 86篇 |
1979年 | 57篇 |
1978年 | 41篇 |
1976年 | 38篇 |
1975年 | 36篇 |
1974年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Note on Bernstein polynomials and Kantorovich polynomials 总被引:2,自引:0,他引:2
Wang Xiaochun 《分析论及其应用》1991,7(2):99-105
We obtain two asymptotic representations of remainder of approximation of derivable functions by Bernstein polynomials and
Kantorovich polynomials separately. 相似文献
22.
Ronggang Wang 《Communications in Mathematical Physics》1991,137(3):587-597
A new type of vortices called Chern-Simons vortices is considered and the existence is established. 相似文献
23.
Bingxin LiuYoshio Tatamitani Jun ShimadaTeruhiko Ogata 《Journal of Molecular Spectroscopy》2002,211(1):99-106
The microwave spectrum of the 35Cl and 37Cl isotopic species of 1-chloro-1,1,2-trifluoroethane (HCFC-133b) has been investigated in the frequency region 10 to 50 GHz using a Stark modulation microwave spectrometer. A pulsed jet Fourier transform microwave spectrometer was also used for the measurement of hyperfine splittings. A least-squares analysis of the observed b-type Q- and R-branch transition frequencies gave rotational and centrifugal distortion constants and components of the chlorine nuclear quadrupole coupling constant tensors in the principal axes system as follows: A=4625.161 (3) MHz, B=2004.127 (2) MHz, C=1875.813 (2) MHz, ΔJ=0.144 (9) kHz, ΔJK=1.0748 (8) kHz, ΔK=1.57 (1) kHz, δJ=0.01376 (4) kHz, δK=−0.146 (4) kHz, χaa=−57.958 (10) MHz, χbb=21.231 (11) MHz, and χcc=36.727 (11) MHz for 35ClCF2CH2F species, and A=4607.684 (6) MHz, B=1960.565 (2) MHz, C=1834.823 (2) MHz, ΔJ=0.106 (7) kHz, ΔJK=1.022 (3) kHz, ΔK=1.48 (1) kHz, δJ=0.0142 (2) kHz, δK=−0.18 (2) kHz, χaa=−46.268 (11) MHz, χbb=17.319 (13) MHz, and χcc=28.950 (13) MHz for 37ClCF2CH2F species. The structural parameters are calculated from the observed six rotational constants by assuming the partial structure of ab initio calculation. The electronic properties of the C-Cl bond are evaluated from the observed nuclear quadrupole constants of chlorine. These molecular properties are compared with those of other related molecules. 相似文献
24.
The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar+ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate. 相似文献
25.
26.
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
27.
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
28.
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
29.
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
30.
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