全文获取类型
收费全文 | 34882篇 |
免费 | 1269篇 |
国内免费 | 265篇 |
专业分类
化学 | 24677篇 |
晶体学 | 280篇 |
力学 | 685篇 |
综合类 | 1篇 |
数学 | 5967篇 |
物理学 | 4806篇 |
出版年
2023年 | 167篇 |
2022年 | 325篇 |
2021年 | 431篇 |
2020年 | 611篇 |
2019年 | 599篇 |
2018年 | 417篇 |
2017年 | 390篇 |
2016年 | 943篇 |
2015年 | 831篇 |
2014年 | 1005篇 |
2013年 | 1707篇 |
2012年 | 2181篇 |
2011年 | 2464篇 |
2010年 | 1334篇 |
2009年 | 1183篇 |
2008年 | 2276篇 |
2007年 | 2094篇 |
2006年 | 2118篇 |
2005年 | 1971篇 |
2004年 | 1691篇 |
2003年 | 1382篇 |
2002年 | 1336篇 |
2001年 | 487篇 |
2000年 | 471篇 |
1999年 | 410篇 |
1998年 | 399篇 |
1997年 | 418篇 |
1996年 | 449篇 |
1995年 | 314篇 |
1994年 | 368篇 |
1993年 | 335篇 |
1992年 | 303篇 |
1991年 | 278篇 |
1990年 | 244篇 |
1989年 | 210篇 |
1988年 | 210篇 |
1987年 | 221篇 |
1986年 | 181篇 |
1985年 | 377篇 |
1984年 | 331篇 |
1983年 | 281篇 |
1982年 | 342篇 |
1981年 | 278篇 |
1980年 | 288篇 |
1979年 | 240篇 |
1978年 | 227篇 |
1977年 | 217篇 |
1976年 | 209篇 |
1975年 | 186篇 |
1974年 | 160篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Capacity Constrained Transit Assignment with Common Lines 总被引:1,自引:0,他引:1
Fumitaka Kurauchi Michael G. H. Bell Jan-Dirk Schmöcker 《Journal of Mathematical Modelling and Algorithms》2003,2(4):309-327
This paper proposes the use of absorbing Markov chains to solve the capacity constrained transit network loading problem taking
common lines into account. The approach handles congested transit networks, where some passengers will not be able to board
because of the absence of sufficient space. The model also handles the common lines problem, where choice of route depends
on frequency of arrivals. The mathematical formulation of the problem is presented together with a numerical example.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
92.
Maria G. Semenova Larisa E. Belyakova Anna S. Antipova Yu. N. Polikarpov Lida Klouda Anna Markovic Michael M. Il'in 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):47-54
We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na+), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed. 相似文献
93.
94.
95.
96.
97.
98.
Stefan Pitsch Sebastian Wendeborn Ramanarayanan Krishnamurthy Armin Holzner Mark Minton Martin Bolli Christian Miculca Norbert Windhab Ronald Micura Michael Stanek Bernhard Jaun Albert Eschenmoser 《Helvetica chimica acta》2003,86(12):4270-4363
Pyranosyl‐RNA (‘p‐RNA’ ) is an oligonucleotide system isomeric to natural RNA and composed of the very same building blocks as RNA. Its generational, chemical, and informational properties are deemed to be those of an alternative nucleic acid system that could have been a candidate in Nature's evolutionary choice of the molecular basis of genetic function. We consider the study of the chemistry of p‐RNA as etiologically relevant in the sense that knowledge of its structural, chemical, and informational properties on the chemical level offers both a perspective and reference points for the recognition of specific structural assets of the RNA structure that made it the (supposedly) superior system among possible alternatives and, therefore, the system that became part of biology as we know it today. The paper describes the chemical synthesis of β‐d‐ (and L )‐ribopyranosyl‐(4′→2′)‐oligonucleotide sequences, presents a resume of their structural and chemical properties, and cautiously discusses what we may and may not have learned from the pyranosyl isomer of RNA with respect to the conundrum of RNA's origin. 相似文献
99.
100.
Michael B. Mensky 《General Relativity and Gravitation》2003,35(9):1729-1732