全文获取类型
收费全文 | 38460篇 |
免费 | 2403篇 |
国内免费 | 3137篇 |
专业分类
化学 | 7580篇 |
晶体学 | 132篇 |
力学 | 1542篇 |
综合类 | 374篇 |
数学 | 14381篇 |
物理学 | 5159篇 |
综合类 | 14832篇 |
出版年
2024年 | 66篇 |
2023年 | 370篇 |
2022年 | 651篇 |
2021年 | 744篇 |
2020年 | 912篇 |
2019年 | 882篇 |
2018年 | 860篇 |
2017年 | 1012篇 |
2016年 | 1024篇 |
2015年 | 977篇 |
2014年 | 2143篇 |
2013年 | 3020篇 |
2012年 | 2370篇 |
2011年 | 2534篇 |
2010年 | 2151篇 |
2009年 | 2478篇 |
2008年 | 2545篇 |
2007年 | 2120篇 |
2006年 | 1895篇 |
2005年 | 1777篇 |
2004年 | 1512篇 |
2003年 | 1388篇 |
2002年 | 1223篇 |
2001年 | 933篇 |
2000年 | 1016篇 |
1999年 | 912篇 |
1998年 | 760篇 |
1997年 | 774篇 |
1996年 | 970篇 |
1995年 | 747篇 |
1994年 | 623篇 |
1993年 | 385篇 |
1992年 | 362篇 |
1991年 | 324篇 |
1990年 | 281篇 |
1989年 | 238篇 |
1988年 | 210篇 |
1987年 | 137篇 |
1986年 | 96篇 |
1985年 | 98篇 |
1984年 | 98篇 |
1983年 | 41篇 |
1982年 | 69篇 |
1981年 | 66篇 |
1980年 | 48篇 |
1979年 | 35篇 |
1978年 | 34篇 |
1977年 | 20篇 |
1976年 | 26篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Rogério S. Mol 《Bulletin of the Brazilian Mathematical Society》2006,37(1):29-48
Résumé. Nous définissons des classes polaires associées à une distribution holomorphe singulière de sous-espaces tangents d’une variété
projective lisse. Nous prouvons que ces classes polaires peuvent être calculées en fonction des classes de Chern-Mather du
faisceau tangent de la distribution et réciproquement. Nous utilisons leurs degrés pour borner les degrés de certaines classes
polaires associés à une variété invariante.
*Ce travail a été soutenu par l’Accord de Coopération France-Brésil (CNRS/CNPq) et par la Fondation CAPES-Brésil. 相似文献
92.
The mass spectrum ofcb meson is investigated with an effective quark-antiquark potential of the form -αc/r +Ar
νwith ν varying from 0.5 to 2.0. TheS andP-wave masses, pseudoscalar decay constant, weak decay partial widths in spectator model and the lifetime ofB
cmeson are computed. The properties calculated here are found to be in good agreement with other theoretical and experimental
values at potential index,ν = 1 相似文献
93.
We prove that for any given c, 1 < c < 17/11, almost all natural numbers are representable in the form [x
c] + [p
c], where x is a natural number and p is a prime. 相似文献
94.
R. Jayakumar Y.‐S. Lee S. Nanjundan 《Journal of polymer science. Part A, Polymer chemistry》2003,41(18):2865-2878
The calcium salt of mono(hydroxyethoxyethyl)phthalate [Ca(HEEP)2] was synthesized by the reaction of diethylene glycol, phthalic anhydride, and calcium acetate. Calcium‐containing poly(urethane ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI) with a mixture of Ca(HEEP)2 and poly(ethylene glycol) (PEG300 or PEG400) with di‐n‐butyltin dilaurate as a catalyst. A series of calcium‐containing PUEs of different compositions were synthesized with Ca(HEEP)2/PEG300 (or PEG400)/diisocyanate (HMDI or TDI) molar ratios of 2:2:4, 3:1:4, and 1:3:4 so that the coating properties of the PUEs could be studied. Blank PUEs without calcium‐containing ionic diols were also prepared by the reaction of PEG300 or PEG400 with HMDI or TDI. The PUEs were well characterized by Fourier transform infrared, 1H and 13C NMR, solid‐state cross‐polarity/magic‐angle‐spinning 13C NMR, viscosity, solubility, and X‐ray diffraction studies. The thermal properties of the polymers were also studied with thermogravimetric analysis and differential scanning calorimetry. The PUEs were applied as top coats on acrylic‐coated leather, and their physicomechanical properties were also studied. The coating properties of PUEs, such as the tensile strength, elongation at break, tear strength, water vapor permeability, flexing endurance, cold crack resistance, abrasion resistance, color fastness, and adhesive strength, were better than the standard values. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2865–2878, 2003 相似文献
95.
96.
Cao H. P. Chen G. Grechkoseeva M. A. Mazurov V. D. Shi W. J. Vasil'ev A. V. 《Siberian Mathematical Journal》2004,45(6):1031-1035
The spectrum of a finite group is the set of its element orders. A finite group G is said to be recognizable by spectrum, if every finite group with the same spectrum as G is isomorphic to G. The purpose of the paper is to prove that for every natural m the finite simple Chevalley group F
4(2
m
) is recognizable by spectrum. 相似文献
97.
Pearson-χ~2距离的若干性质 总被引:18,自引:0,他引:18
李开灿 《数学的实践与认识》2003,33(1):49-53
本文对数理统计中常用的 Pearson- χ2距离的分析特性进行了讨论 ,得到了这一距离的一些解析性质 ,最后我们还给出了几个常用距离的关系 . 相似文献
98.
Juan Gonzá lez-Meneses Luis Paris 《Transactions of the American Mathematical Society》2004,356(1):219-243
We show that Vassiliev invariants separate braids on a closed oriented surface, and we exhibit a universal Vassiliev invariant for these braids in terms of chord diagrams labeled by elements of the fundamental group of the surface.
99.
Bing-sheng He Zhen-hua Yang Xiao-ming Yuan 《Journal of Mathematical Analysis and Applications》2004,300(2):139-374
Proximal point algorithms (PPA) are attractive methods for monotone variational inequalities. The approximate versions of PPA are more applicable in practice. A modified approximate proximal point algorithm (APPA) presented by Solodov and Svaiter [Math. Programming, Ser. B 88 (2000) 371–389] relaxes the inexactness criterion significantly. This paper presents an extended version of Solodov–Svaiter's APPA. Building the direction from current iterate to the new iterate obtained by Solodov–Svaiter's APPA, the proposed method improves the profit at each iteration by choosing the optimal step length along this direction. In addition, the inexactness restriction is relaxed further. Numerical example indicates the improvement of the proposed method. 相似文献
100.
TieYong YangGuangjun 《分析论及其应用》2004,20(1):58-68
In this paper, we construct some continuous but non-differentiable functions defined by quinary decimal, that are Kiesswetter-like functions. We discuss their properties, then investigate the Hausdorff dimensions of graphs of these functions and give a detailed proof. 相似文献