全文获取类型
收费全文 | 33628篇 |
免费 | 1105篇 |
国内免费 | 254篇 |
专业分类
化学 | 23365篇 |
晶体学 | 237篇 |
力学 | 778篇 |
数学 | 5494篇 |
物理学 | 5113篇 |
出版年
2022年 | 287篇 |
2021年 | 427篇 |
2020年 | 520篇 |
2019年 | 495篇 |
2018年 | 382篇 |
2017年 | 376篇 |
2016年 | 849篇 |
2015年 | 746篇 |
2014年 | 820篇 |
2013年 | 1768篇 |
2012年 | 1894篇 |
2011年 | 2398篇 |
2010年 | 1163篇 |
2009年 | 1036篇 |
2008年 | 2050篇 |
2007年 | 2077篇 |
2006年 | 2070篇 |
2005年 | 1929篇 |
2004年 | 1622篇 |
2003年 | 1425篇 |
2002年 | 1319篇 |
2001年 | 427篇 |
2000年 | 412篇 |
1999年 | 377篇 |
1998年 | 346篇 |
1997年 | 367篇 |
1996年 | 502篇 |
1995年 | 363篇 |
1994年 | 309篇 |
1993年 | 279篇 |
1992年 | 291篇 |
1991年 | 246篇 |
1990年 | 221篇 |
1989年 | 216篇 |
1988年 | 249篇 |
1987年 | 213篇 |
1986年 | 191篇 |
1985年 | 357篇 |
1984年 | 355篇 |
1983年 | 244篇 |
1982年 | 327篇 |
1981年 | 329篇 |
1980年 | 301篇 |
1979年 | 295篇 |
1978年 | 276篇 |
1977年 | 245篇 |
1976年 | 212篇 |
1975年 | 213篇 |
1974年 | 218篇 |
1973年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
David Ruelle 《Communications in Mathematical Physics》2007,270(1):233-265
We analyze the dynamics of a simple but nontrivial classical Hamiltonian system of infinitely many coupled rotators. We assume
that this infinite system is driven out of thermal equilibrium either because energy is injected by an external force (Case
I), or because heat flows between two thermostats at different temperatures (Case II). We discuss several possible definitions
of the entropy production associated with a finite or infinite region, or with a partition of the system into a finite number
of pieces. We show that these definitions satisfy the expected bounds in terms of thermostat temperatures and energy flow. 相似文献
103.
Huayang Zhu Robert J. Kee Jeffrey R. Engel David T. Wickham 《Proceedings of the Combustion Institute》2007,31(2):1965-1972
This paper reports the results of experimental and modeling efforts to characterize partial oxidation of methane to produce synthesis gas (H2 and CO) using metal-substituted hexaaluminate catalysts in short-contact-time reactors. Hexaaluminate catalysts offer excellent high-temperature stability compared to the equivalent metal-based catalysts. The hexaaluminates are synthesized by a metal-exchange process using alumoxane precursors that enable a wide range of metal substitutions. Of all the combinations tested, RhSr-substituted hexaaluminates yielded the best performance. The catalysts are supported on alumina porous-foam structures, which are positioned within a tube furnace to control the operating temperature. Two-stage combinations of RhSr- and Ni-substituted hexaaluminates are shown to improve conversion activity and selectivity compared to a single-catalyst system. 相似文献
104.
François Loiseau Jean-Mary Simone David Carcache Pavel Bobal Reinhard Neier 《Monatshefte für Chemie / Chemical Monthly》2007,138(2):121-129
Summary. Free radical couplings from furan, as cheap starting material, were studied in view of developing a rapid strategy en route to the synthesis of derivatives of nonactin. The chain containing the alcohol function was introduced in one or two steps
in 86% yield. For the introduction of the second chain with the ester function two different coupling methods were tested.
Starting from the advanced intermediates obtained nonactin derivatives can be prepared by catalytic hydrogenation of the furan
ring. 相似文献
105.
David Worthington 《The Journal of the Operational Research Society》1991,42(10):833-843
This paper describes work carried out with hospital consultants in Lancaster District Health Authority to develop and use computerized waiting list management models. The ‘what if?’ models produced have been found to be a very useful tool in the constructive debate about problems faced by consultants and managers, and of the options available to them. 相似文献
106.
107.
It is shown that if in a simple graph G of order n the sum of degrees of any three pairwise non-adjacent vertices is at least n, then there are two cycles (or one cycle and an edge or a vertex) of GF that contain all the vertices. © 1995 John Wiley & Sons, Inc. 相似文献
108.
We analyze an infinite horizon, single product, continuous review model in which pricing and inventory decisions are made simultaneously and ordering cost includes a fixed cost. We show that there exists a stationary (s,S) inventory policy maximizing the expected discounted or expected average profit under general conditions. 相似文献
109.
David L. Applegate 《Operations Research Letters》2007,35(6):693-699
The use of floating-point calculations limits the accuracy of solutions obtained by standard LP software. We present a simplex-based algorithm that returns exact rational solutions, taking advantage of the speed of floating-point calculations and attempting to minimize the operations performed in rational arithmetic. Extensive computational results are presented. 相似文献
110.
We give a new independent self-dual 3-basis for the trivial variety with two binary operations.
Received October 24, 2006; accepted in final form January 25, 2007. 相似文献