全文获取类型
收费全文 | 16727篇 |
免费 | 588篇 |
国内免费 | 1664篇 |
专业分类
化学 | 3978篇 |
晶体学 | 98篇 |
力学 | 2158篇 |
综合类 | 55篇 |
数学 | 8466篇 |
物理学 | 4224篇 |
出版年
2020年 | 118篇 |
2017年 | 182篇 |
2016年 | 214篇 |
2015年 | 241篇 |
2014年 | 423篇 |
2013年 | 896篇 |
2012年 | 697篇 |
2011年 | 822篇 |
2010年 | 702篇 |
2009年 | 551篇 |
2008年 | 378篇 |
2007年 | 614篇 |
2006年 | 701篇 |
2005年 | 617篇 |
2004年 | 543篇 |
2003年 | 518篇 |
2002年 | 503篇 |
2001年 | 643篇 |
2000年 | 670篇 |
1999年 | 664篇 |
1998年 | 394篇 |
1997年 | 376篇 |
1996年 | 357篇 |
1995年 | 383篇 |
1994年 | 363篇 |
1993年 | 373篇 |
1992年 | 343篇 |
1991年 | 348篇 |
1990年 | 305篇 |
1989年 | 272篇 |
1988年 | 260篇 |
1987年 | 182篇 |
1986年 | 161篇 |
1985年 | 195篇 |
1984年 | 228篇 |
1983年 | 176篇 |
1982年 | 190篇 |
1981年 | 242篇 |
1980年 | 193篇 |
1979年 | 172篇 |
1978年 | 197篇 |
1977年 | 215篇 |
1976年 | 237篇 |
1975年 | 218篇 |
1974年 | 187篇 |
1973年 | 187篇 |
1972年 | 141篇 |
1971年 | 127篇 |
1970年 | 135篇 |
1969年 | 111篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Fu Xianlong Zhou Lei Cao Yueju 《Annals of Differential Equations》2005,21(3):275-278
In this paper, we establish a criterion of unformly asymptotic stability for finite delay difference systems in terms of two measures by employing Lyapunov functionals method. 相似文献
992.
E Mincsovics Gy Kátay P G Ott Zs Király-Véghely Á M Móricz E Tyihák 《Chromatographia》2005,62(13):s51-s56
The first results of the combination of BioArena and OPLC with flowing eluent wall technique (FEW) show an especially attractive solution of the detection of antimicrobial activity and compound isolation based on peak collection. Because of the different separation mechanisms applied for on-line FEW–OPLC isolation of red wine constituents and for further off-line OPLC investigation of fractions, the combined system yields high selectivity. 相似文献
993.
Zhou Mingru 《Annals of Differential Equations》2005,21(4):639-647
This paper is concerned with boundary and corner layer behavior of the singularly perturbed Robin boundary value problem(RP) for the second-order nonlinear differential equations. The existence and asymptotic estimate of solutions of (RP) is discussed by appropriately constructing the bounding functions and using the theory of differential inequality. 相似文献
994.
Guo Yanfeng Liu Anping Yang Xianghui Wang Xiaomei 《Annals of Differential Equations》2005,21(3):286-289
In this paper, oscillatory properties for solutions of certain nonlinear impulsive parabolic equation are investigated and a series of new sufficient conditions is established. 相似文献
995.
一类局部定向完备集及其范畴的性质 总被引:4,自引:0,他引:4
本文给出了局部定向完备集的概念及其在此结构下的一种新的双小于关系,从而进一步给出了一种新的连续性概念,接着讨论了局部定向完备集,连续的局部定向完备集等对象的一些性质,最后考察了三种范畴的笛卡儿闭性,并证明了范畴LDCPO是范畴ALG的反射满子范畴. 相似文献
996.
《Journal of Complexity》2005,21(4):593-608
Recently we developed a diagonal homotopy method to compute a numerical representation of all positive dimensional components in the intersection of two irreducible algebraic sets. In this paper, we rewrite this diagonal homotopy in intrinsic coordinates, which reduces the number of variables, typically in half. This has the potential to save a significant amount of computation, especially in the iterative solving portion of the homotopy path tracker. Three numerical experiments all show a speedup of about a factor two. 相似文献
997.
We study the possibility of splitting any bounded analytic function ƒ with singularities in a closed set E ⋃ F as a sum of two bounded analytic functions with singularities in E and F respectively. We obtain some results under geometric restrictions on the sets E and F and we provide some examples showing the sharpness of the positive results.
The first author is partially supported by RFBR grant #06-01-00313 and by the grant for Leading Scientific Schools #NSH-2266-2003.1.
The last author is supported by DGICYT grant MTM2005-08984-C02-02 and the CIRIT grant 2005SGR00611. 相似文献
998.
《Journal of membrane science》2005,246(2):203-215
Nitrogen-based plasma systems such as N2, NH3, Ar/NH3, and O2/NH3 were used to modify microporous polyethersulfone membranes. Treatments were designed to alter the surface chemistry of the membranes to create permanently hydrophilic surfaces. Contact angle measurements taken initially, as well as 1 year post-treatment confirmed that treatments using O2/NH3 plasmas (with a 5:3 gas flow ratio) were successful in achieving our designed goals. Analyses by FT-IR and XPS established the incorporation of NHx and OH species in the PES membranes. Moreover, the plasma penetrates the thickness of the membrane, thereby modifying the entire membrane cross-section. Optical emission spectroscopy studies of excited state species present in the modifying gases revealed the presence of OH*, which was not present in a 100% ammonia plasma, suggesting OH* must play a critical role in the membrane modification process. Investigations using bubble point analysis, differential scanning calorimetry, and scanning electron microscopy demonstrate there is no damage occurring under these specific treatment conditions. The usefulness of this treatment is revealed by increased water flux, reduced protein fouling, and greater flux recovery after gentle cleaning when compared to an untreated membrane. 相似文献
999.
J.C. Califano A. Uribe J.L. Chang C.L. Becker J.J. Napier V. Kishore D. Zhou G. Love K. Gernhardt J.C. Tolle 《Tetrahedron》2005,61(37):8821-8829
Oligomers of arginine, such as octa-d-arginine amide, are excellent transporters for active drugs through cell membranes and tissue. The synthesis of octa-d-arginine amide, as the nonahydrochloride salt, was approached via a solution phase synthetic route involving the preparation of an octa-d-ornithine intermediate, which was then converted into the desired octa-d-arginine compound through a guanidinylation step. The multi-step synthesis was carried out at pilot scale, resulting in the preparation of 700 g of the target molecule. No chromatographic purification was needed at any step of the process. 相似文献
1000.
H. Shin E. Yoon K.-S. Hong W. Lee Y.-H. Yoo 《Applied Physics A: Materials Science & Processing》2005,81(4):715-719
The shifts of emission energy from InAs quantum dots (QDs) in the GaAs matrix due to change in the QD stacking period have been numerically analyzed by investigating the strain modified shifts of band edges. Narrower stacking results in a blueshift of emission energy from direct band gap transition provided the QD spacing is wide enough to avoid electronic coupling. Through a comparison with existing experimental results in the literature, processing methods and variables that have benefits in achieving a blueshift have been inferred. A blueshift through decreased QD spacing has been proposed as a token of the integrity of a processed QD nanostructure . PACS 68.65.+g; 78.66.Fd 相似文献