全文获取类型
收费全文 | 39696篇 |
免费 | 1218篇 |
国内免费 | 334篇 |
专业分类
化学 | 26921篇 |
晶体学 | 302篇 |
力学 | 917篇 |
数学 | 7110篇 |
物理学 | 5998篇 |
出版年
2022年 | 331篇 |
2021年 | 458篇 |
2020年 | 579篇 |
2019年 | 541篇 |
2018年 | 449篇 |
2017年 | 417篇 |
2016年 | 959篇 |
2015年 | 836篇 |
2014年 | 916篇 |
2013年 | 2107篇 |
2012年 | 2161篇 |
2011年 | 2687篇 |
2010年 | 1364篇 |
2009年 | 1199篇 |
2008年 | 2313篇 |
2007年 | 2325篇 |
2006年 | 2358篇 |
2005年 | 2217篇 |
2004年 | 1890篇 |
2003年 | 1647篇 |
2002年 | 1556篇 |
2001年 | 494篇 |
2000年 | 466篇 |
1999年 | 443篇 |
1998年 | 434篇 |
1997年 | 453篇 |
1996年 | 627篇 |
1995年 | 429篇 |
1994年 | 384篇 |
1993年 | 350篇 |
1992年 | 357篇 |
1991年 | 310篇 |
1990年 | 270篇 |
1989年 | 263篇 |
1988年 | 287篇 |
1987年 | 270篇 |
1986年 | 238篇 |
1985年 | 443篇 |
1984年 | 457篇 |
1983年 | 325篇 |
1982年 | 403篇 |
1981年 | 439篇 |
1980年 | 429篇 |
1979年 | 373篇 |
1978年 | 361篇 |
1977年 | 307篇 |
1976年 | 297篇 |
1975年 | 303篇 |
1974年 | 302篇 |
1973年 | 299篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
Asymptotics in the random assignment problem 总被引:1,自引:0,他引:1
David Aldous 《Probability Theory and Related Fields》1992,93(4):507-534
Summary We show that, in the usual probabilistic model for the random assignment problem, the optimal cost tends to a limit constant in probability and in expectation. The method involves construction of an infinite limit structure, in terms of which the limit constant is defined. But we cannot improve on the known numerical bounds for the limit.Research supported by NSF Grant MCS90-01710 相似文献
83.
Eschweiler-Clarke methylations of both acyclic and cyclic polyamines can lead to methylation products of fragments of the original polyamine; thus 1,5,9,13-tetra-azatridecane yields 1,1,3,3-tetramethylpropanediamine exclusively and 1,5,9-triazacyclododecane gives 45% 1,5,9-trimethyl-1,5,9-triazacyclodecane and 45% 2,6,10-trimethyl-2,6,10-triazaundecane. 相似文献
84.
85.
86.
Charles Blair 《Mathematical Programming》1995,71(2):127-136
We identify a class of formulas computable in polynomial time such that the functions defined by these formulas are precisely the value functions of mixed-integer programs with rational constraint coefficients. 相似文献
87.
88.
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
89.
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
90.
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