全文获取类型
收费全文 | 6714篇 |
免费 | 659篇 |
国内免费 | 632篇 |
专业分类
化学 | 3864篇 |
晶体学 | 36篇 |
力学 | 231篇 |
综合类 | 73篇 |
数学 | 2724篇 |
物理学 | 1077篇 |
出版年
2024年 | 7篇 |
2023年 | 54篇 |
2022年 | 71篇 |
2021年 | 95篇 |
2020年 | 173篇 |
2019年 | 175篇 |
2018年 | 178篇 |
2017年 | 229篇 |
2016年 | 180篇 |
2015年 | 209篇 |
2014年 | 289篇 |
2013年 | 1034篇 |
2012年 | 285篇 |
2011年 | 320篇 |
2010年 | 279篇 |
2009年 | 368篇 |
2008年 | 372篇 |
2007年 | 407篇 |
2006年 | 379篇 |
2005年 | 313篇 |
2004年 | 296篇 |
2003年 | 258篇 |
2002年 | 868篇 |
2001年 | 185篇 |
2000年 | 191篇 |
1999年 | 127篇 |
1998年 | 148篇 |
1997年 | 78篇 |
1996年 | 96篇 |
1995年 | 81篇 |
1994年 | 63篇 |
1993年 | 39篇 |
1992年 | 31篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1973年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有8005条查询结果,搜索用时 31 毫秒
71.
72.
Multiple-zero multiple-pole optical filter transfer functions may be implemented more efficiently in an integrated optics architecture if higher order N × M optical couplers are utilized. For example, a coherent ring resonator made from two 3×3 couplers offers some advantages over the three mirror Fabry-Perot etalon, which is its analog. To this end we develop the formalism for obtaining the transfer functions and scattering matrices of ring resonators made from two N × M couplers. We then present a methodology for analyzing serial and parallel systems of N × M optical coupler ring resonators. 相似文献
73.
JINJIANG YUAN 《运筹学学报》1998,(3)
1.IntroductionGraphsconsideredinthispaperarefiniteandsimple.FOragraphG,V(G)andE(G)denoteitssetofvenicesandedges,respectively.AbijectionwillbecalledalabellingofG.Letpbeapositiverealnumber.ForagivenlabellingTofagraphG,definethegndiscrepencya.(G,ac)ofTasTheobjectiveoftheminimum-p--sumproblemistofindalabelling7ofagraphGsuchthatac(G,T)isassmallaspossible.ThelabellingTminimizinga.(G,7)iscalledanoptimalHsumlabellingofG.Theminimumvalueiscalledtheminimum-psumofG.ItisshowninI31thattheminimum-… 相似文献
74.
C. Scheidenberger K. Beckert P. Beller F. Bosch C. Brandau D. Boutin L. Chen B. Franzke H. Geissel R. Knöbel C. Kozhuharov J. Kurcewicz S. A. Litvinov Yu. A. Litvinov M. Mazzocco G. Münzenberg F. Nolden W. R. Plaß M. Steck B. Sun H. Weick M. Winkler 《Hyperfine Interactions》2006,173(1-3):61-66
One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams
stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for
high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented.
P. Beller, deceased. 相似文献
75.
设$(A,B,V,W,\psi,\phi)$是一个Morita Context,具有一对零态射$\psi=0$, $\phi=0$, $C =\left ( \begin{array} {cc}A & V \\W & B \end{array}\right)$是对应的Morita Context环.本文给出了$C$与$A,B,V,W$之间关于环的$\pi$-正则性、semiclean性、Mophic性和环的Exchgange性、Potent性、GM性的关系. 相似文献
76.
牛顿环实验中的误差分析 总被引:2,自引:0,他引:2
本文对牛顿环测透镜曲率半径实验中引起误差的各种原因进行分析讨论,指出了误差的主要来源及比较完善可行的处理方法。 相似文献
77.
讨论带有对合反自同构*有单位元的结合环R上矩阵的广义Moore-Penrose 逆,给出了环R上矩阵的广义Moore-Penrose逆存在的几个充要条件.特别,得到了环 R上矩阵A的关于M和N的广义Moore-Penrose逆存在的充要条件是A有分解A= GDH,其中D2=D,(MD)*=MD,(GD)*MGD+M(I-D)和DHN-1(DH)*+ (I-D)M-1均可逆. 相似文献
78.
Let R be a ring. R is called right AP-injective if, for any a ∈ R, there exists a left ideal of R such that lr(a) = Ra (?) Xa. We extend this notion to modules. A right .R-module M with 5 = End(MR) is called quasi AP-injective if, for any s ∈ S, there exists a left ideal Xs of S such that ls(Ker(s)) = Ss (?) Xs. In this paper, we give some characterizations and properties of quasi AP-injective modules which generalize results of Page and Zhou. 相似文献
79.
80.
Anette Munch Elmr Patric Jannasch 《Journal of polymer science. Part A, Polymer chemistry》2006,44(7):2195-2205
Methacrylate‐functionalized poly(ethylene oxide‐co‐ethylene carbonate) macromonomers were prepared in two steps by the anionic ring‐opening polymerization of ethylene carbonate at 180 °C, with potassium methoxide as the initiator, followed by the reaction of the terminal hydroxyl groups of the polymers with methacryloyl chloride. The molecular weight of the polymer went through a maximum after approximately 45 min of polymerization, and the content of ethylene carbonate units in the polymer decreased with the reaction time. A polymer having a number‐average molecular weight of 2650 g mol?1 and an ethylene carbonate content of 28 mol % was selected and used to prepare a macromonomer, which was subsequently polymerized by UV irradiation in the presence of different concentrations of lithium bis(trifluoromethanesulfonyl)imide salt. The resulting self‐supportive crosslinked polymer electrolyte membranes reached ionic conductivities of 6.3 × 10?6 S cm?1 at 20 °C. The coordination of the lithium ions by both the ether and carbonate oxygens in the polymer structure was indicated by Fourier transform infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2195–2205, 2006 相似文献