全文获取类型
收费全文 | 9717篇 |
免费 | 311篇 |
国内免费 | 80篇 |
专业分类
化学 | 6803篇 |
晶体学 | 46篇 |
力学 | 255篇 |
数学 | 1536篇 |
物理学 | 1468篇 |
出版年
2022年 | 42篇 |
2021年 | 112篇 |
2020年 | 149篇 |
2019年 | 142篇 |
2018年 | 105篇 |
2017年 | 78篇 |
2016年 | 230篇 |
2015年 | 196篇 |
2014年 | 231篇 |
2013年 | 542篇 |
2012年 | 560篇 |
2011年 | 710篇 |
2010年 | 324篇 |
2009年 | 243篇 |
2008年 | 535篇 |
2007年 | 616篇 |
2006年 | 640篇 |
2005年 | 518篇 |
2004年 | 470篇 |
2003年 | 403篇 |
2002年 | 371篇 |
2001年 | 148篇 |
2000年 | 96篇 |
1999年 | 91篇 |
1998年 | 87篇 |
1997年 | 111篇 |
1996年 | 119篇 |
1995年 | 95篇 |
1994年 | 84篇 |
1993年 | 105篇 |
1992年 | 88篇 |
1991年 | 66篇 |
1990年 | 97篇 |
1989年 | 55篇 |
1988年 | 71篇 |
1987年 | 70篇 |
1986年 | 85篇 |
1985年 | 123篇 |
1984年 | 120篇 |
1983年 | 78篇 |
1982年 | 109篇 |
1981年 | 104篇 |
1980年 | 102篇 |
1979年 | 79篇 |
1978年 | 101篇 |
1977年 | 78篇 |
1976年 | 79篇 |
1975年 | 64篇 |
1974年 | 47篇 |
1973年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Erica L. Plambeck Bor-Ruey Fu Stephen M. Robinson Rajan Suri 《Mathematical Programming》1996,75(2):137-176
In this paper we propose a method for optimizing convex performance functions in stochastic systems. These functions can include
expected performance in static systems and steady-state performance in discrete-event dynamic systems; they may be nonsmooth.
The method is closely related to retrospective simulation optimization; it appears to overcome some limitations of stochastic
approximation, which is often applied to such problems. We explain the method and give computational results for two classes
of problems: tandem production lines with up to 50 machines, and stochastic PERT (Program Evaluation and Review Technique)
problems with up to 70 nodes and 110 arcs.
Sponsored by the National Science Foundation under grant number CCR-9109345, by the Air Force Systems Command, USAF, under
grant numbers F49620-93-1-0068 and F49620-95-1-0222, by the U.S. Army Research Office under grant number DAAL03-92-G-0408,
and by the U.S. Army Space and Strategic Defense Command under contract number DASG60-91-C-0144. The U.S. Government has certain
rights in this material, and is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding
any copyright notation thereon.
Sponsored by a Wisconsin/Hilldale Research Award, by the U.S. Army Space and Strategic Defense Command under contract number
DASG60-91-C-0144, and the Air Force Systems Command, USAF, under grant number F49620-93-1-0068.
Sponsored by the National Science Foundation under grant number DDM-9201813. 相似文献
63.
64.
Stephen D. Cohen 《Monatshefte für Mathematik》1989,107(4):291-301
Chambers andSmeets [3] have designed a windmill arrangement of linear feedback shift registers (LFSRs) to generate pn-sequences overGF(2) with high speed. When the windmill hasv vanes, the associated minimal feedback polynomial (having degreen, relatively prime tov) can be taken to have the shapef
1(x
v
)+x
n
f
2(x
–v
), where the polynomialsf
1 andf
2 have degree [n/v]. Their numerical evidence, whenv is divisible by 4, suggests that, surprisingly, there areno such windmill polynomials which are irreducible ifn±3 (mod 8), while about twice as many irreducible and primitive windmill polynomials as they expected occur ifn±1 (mod 8). A discussion of this behaviour is presented here with proofs. The brief explanation is that the Galois group of the underlying generic windmill polynomial overGF (4) is equal to the alternating groupA
n
. 相似文献
65.
Stephen D. Smith 《Geometriae Dedicata》1988,25(1-3):355-373
A discussion of results and conjectures, focussed around the extension of the modular representation theory for finite Lie-type groups to more general groups that act on building-like geometries.Based on a lecture given at the conference Groups and Geometries-Finite and Algebraic, on 26 March 1986 at Noordwijkerhout, Netherlands (a NATO Advanced Research Workshop).Partially supported by NSF Grant MCS 83-00855. 相似文献
66.
67.
68.
69.
Compound 1, 2-(4-phenoxyphenylsulfonylmethyl)thiirane, is a potent and selective inhibitor for human gelatinases (J. Am. Chem. Soc. 2000, 122, 6799-6800), enzymes implicated in a number of diseases, including cancer. This compound is showing excellent promise in animal trials in a number of disease models. Large quantities of this compound were necessary for these studies. A convenient four-step synthetic route for compound 1 is described herein. The synthesis is amenable to scale-up to tens of grams and gives an overall yield of 57% for this important compound. 相似文献
70.
Copolymerization of vinyl acetate with allyl carbonates that contain isopropyl groups yields highly branched poly(vinyl acetates). 相似文献