全文获取类型
收费全文 | 60880篇 |
免费 | 1585篇 |
国内免费 | 148篇 |
专业分类
化学 | 36773篇 |
晶体学 | 286篇 |
力学 | 1335篇 |
数学 | 10352篇 |
物理学 | 13867篇 |
出版年
2022年 | 333篇 |
2021年 | 526篇 |
2020年 | 748篇 |
2019年 | 615篇 |
2018年 | 644篇 |
2017年 | 590篇 |
2016年 | 1398篇 |
2015年 | 1229篇 |
2014年 | 1377篇 |
2013年 | 3280篇 |
2012年 | 2621篇 |
2011年 | 3236篇 |
2010年 | 1639篇 |
2009年 | 1474篇 |
2008年 | 3009篇 |
2007年 | 3019篇 |
2006年 | 2779篇 |
2005年 | 2546篇 |
2004年 | 2118篇 |
2003年 | 1821篇 |
2002年 | 1685篇 |
2001年 | 1075篇 |
2000年 | 933篇 |
1999年 | 693篇 |
1998年 | 676篇 |
1997年 | 706篇 |
1996年 | 857篇 |
1995年 | 686篇 |
1994年 | 750篇 |
1993年 | 810篇 |
1992年 | 682篇 |
1991年 | 584篇 |
1990年 | 573篇 |
1989年 | 538篇 |
1988年 | 560篇 |
1987年 | 529篇 |
1986年 | 495篇 |
1985年 | 756篇 |
1984年 | 784篇 |
1983年 | 646篇 |
1982年 | 795篇 |
1981年 | 772篇 |
1980年 | 715篇 |
1979年 | 674篇 |
1978年 | 726篇 |
1977年 | 676篇 |
1976年 | 613篇 |
1975年 | 568篇 |
1974年 | 555篇 |
1973年 | 550篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Hua Zhang Nabil A. Amro Robert Elghanian Joseph Fragala 《Applied Surface Science》2006,253(4):1960-1963
A method, combining micro-contact printing (μCP), wet chemical etching and reactive ion etching (RIE), is reported to fabricate microstructures on Si and SiOx. Positive and negative structures were generated based on different stamps used for μCP. The reproducibility of the obtained microstructures shows the methodology reported herein could be useful in Micro-Electro-Mechanical Systems (MEMS), optical and biological sensing applications. 相似文献
82.
Robert S. Maier 《Random Structures and Algorithms》1991,2(4):379-420
We analyze the performance of a prototypical scheme for shared storage allocation: two initially empty stacks evolving in a contiguous block of memory of size m. We treat the case in which the stacks are more likely to shrink than grow, but with the probabilities of insertion and deletion allowed to depend arbitrarily on stack height as a fraction of m. New results are obtained on the m → ∞ asymptotics of the stack collision time, and of the final stack heights. The results of Wentzell and Freidlin on the large deviations of Markov chains are used, and the relation of their formalism to the Hamiltonian formulation of classical mechanics is emphasized. Certain results on higher-order asymptotics follow from WKB expansions. 相似文献
83.
Summary The optimality question for blockp-cyclic SOR iterations discussed in Young and Varga is answered under natural conditions on the spectrum of the block Jacobi matrix. In particular, it is shown that repartitioning a blockp-cyclic matrix into a blockq-cyclic form,q
, results in asymptotically faster SOR convergence for the same amount of work per iteration. As a consequence block 2-cyclic SOR is optimal under these conditions.Research supported in part by the US Air Force under Grant no. AFOSR-88-0285 and the National Science Foundation under grant no. DMS-85-21154 Present address: Boeing Computer Services, P.O. Box 24346, MS 7L-21, Seattle, WA 98124-0346, USA 相似文献
84.
85.
86.
J. Fülöp 《Mathematical Methods of Operations Research》1991,35(1):1-13
This paper shows that any linear disjunctive program with a finite number of constraints can be transformed into an equivalent facial program. Based upon linear programming technique, a new, finite cutting plane method is presented for the facial programs.
Zusammenfassung Die Arbeit zeigt, daß jedes lineare disjunktive Optimierungsproblem mit endlich vielen Restriktionen in ein äquivalentes Fazetten-Problem transformiert werden kann. Auf der Grundlage von linearer Optimierungstechnik wird für das Fazetten-Problem ein neues, endliches Schnittebenenverfahren vorgestellt.相似文献
87.
György Gát 《Analysis Mathematica》2006,32(1):25-48
Summary It is known that the Fejér means - with respect to the character system of the Walsh, and bounded Vilenkin groups - of an
integrable function converge to the function a.e. In this work we discuss analogous problems on the complete product of finite,
not necessarily Abelian groups with respect to the character system for functions that are constant on the conjugacy classes.
We find that the nonabelian case differs from the commutative case. We prove the a.e. convergence of the (C,1) means of the Fourier series of square integrable functions. We also prove the existence of a function f∊Lq for some q >1 such that sup |σn f | = + ∞ a.e. This is a sharp contrast between the Abelian and the nonabelian cases. 相似文献
88.
Near-infrared calibrations for water, reducing sugar, glycerin, propylene glycol, nicotine, and menthol in tobacco blends were first obtained with a monochromator instrument. Transfer of calibrations to a tilting-filter instrument for factory trials is shown to be facilitated greatly by the computer-assisted scheme MTRAN. By means of this software, calibration equations were established for a Neotec 51A instrument that is sufficiently rugged for factory use. The predictive capabilities of the transferred calibrations are similar to those of the research monochromator. 相似文献
89.
90.
The qualitative behavior of buckled states of two different models of elastic beams is studied. It is assumed that random imperfections affect the governing nonlinear equations. It is shown that near the first critical value of the buckling load the stochastic bifurcation is described asymptotically by an algebraic equation whose coeffficients are Gaussian random variables. The corresponding asymptotic expansion for the displacement is to lowest order a Gaussian stochastic process.Work supported by NSF Grant No. DCR81-14726.Work supported by NSF Grant No. DMS87-01895. 相似文献