全文获取类型
收费全文 | 519828篇 |
免费 | 3549篇 |
国内免费 | 817篇 |
专业分类
化学 | 244311篇 |
晶体学 | 8028篇 |
力学 | 28548篇 |
综合类 | 14篇 |
数学 | 77079篇 |
物理学 | 166214篇 |
出版年
2021年 | 4113篇 |
2020年 | 4641篇 |
2019年 | 5507篇 |
2018年 | 12679篇 |
2017年 | 13156篇 |
2016年 | 12826篇 |
2015年 | 5618篇 |
2014年 | 9538篇 |
2013年 | 19584篇 |
2012年 | 17993篇 |
2011年 | 25873篇 |
2010年 | 18527篇 |
2009年 | 18849篇 |
2008年 | 23508篇 |
2007年 | 25563篇 |
2006年 | 15373篇 |
2005年 | 16771篇 |
2004年 | 14367篇 |
2003年 | 13890篇 |
2002年 | 12833篇 |
2001年 | 12878篇 |
2000年 | 10167篇 |
1999年 | 7492篇 |
1998年 | 6542篇 |
1997年 | 6379篇 |
1996年 | 6069篇 |
1995年 | 5466篇 |
1994年 | 5427篇 |
1993年 | 5294篇 |
1992年 | 5907篇 |
1991年 | 6155篇 |
1990年 | 6082篇 |
1989年 | 6090篇 |
1988年 | 5849篇 |
1987年 | 5917篇 |
1986年 | 5519篇 |
1985年 | 6686篇 |
1984年 | 6965篇 |
1983年 | 5732篇 |
1982年 | 5984篇 |
1981年 | 5744篇 |
1980年 | 5364篇 |
1979年 | 6154篇 |
1978年 | 6197篇 |
1977年 | 6355篇 |
1976年 | 6284篇 |
1975年 | 5773篇 |
1974年 | 5683篇 |
1973年 | 5768篇 |
1972年 | 4580篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
911.
Baumgarten N. Jung H. Mehlhorn K. 《Journal of Algorithms in Cognition, Informatics and Logic》1994,17(3)
The dynamic planar point location problem is the task of maintaining a dynamic set S of n nonintersecting (except possibly at endpoints) line segments in the plane under the following operations:
- • Locate (: point): Report the segment immediately above , i.e., the first segment intersected by an upward vertical ray starting at ;
- • Insert (: segment): Add segment to the collection of segments;
- • Delete (: segment): Remove segment from the collection of segments.
912.
Cheriyan and Hagerup developed a randomized algorithm to compute the maximum flow in a graph with n nodes and m edges in O(mn + n2 log2n) expected time. The randomization is used to efficiently play a certain combinatorial game that arises during the computation. We give a version of their algorithm where a general version of their game arises. Then we give a strategy for the game that yields a deterministic algorithm for computing the maximum flow in a directed graph with n nodes and m edges that runs in time O(mn(logm/n log nn)). Our algorithm gives an O(mn) deterministic algorithm for all m/n = Ω(nε) for any positive constant ε, and is currently the fastest deterministic algorithm for computing maximum flow as long as m/n = ω(log n). 相似文献
913.
914.
A. R. Kuznetsov S. G. Lunter S. I. Nikitina A. G. Plyukhin Yu. K. Fedorov 《Journal of Applied Spectroscopy》1992,56(1):68-72
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 56, No. 1, pp. 90–95, January, 1992. 相似文献
915.
G. V. Plyatsko V. N. Maksimovich L. V. Khomlyak 《Journal of Mathematical Sciences》1992,62(1):2518-2523
We solve the thermoplastic problem for a semi-infinite plate under local nonstationary heating by heat sources. The physical equations are taken to be the relations of the nonisothermic theory of plastic flow associated with the Mises fluidity condition. The solution of the problem is constructed by the method of integral equations and the self-correcting method of sequential loading, where time is taken as the loading parameter. We carry out numerical computations of the stresses in the case of heating a plate with heat output by normal-circular heat sources. We study the problem of optimization of heating regimes in order to introduce favorable residual compressive stresses (from the point of view of hardness) in a given region of a half-plane. Two figures.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 27, 1988, pp. 29–34. 相似文献
916.
M.-K. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):13-18
We examine the influence of relativistic and QED effects on the existence of the 1,3P
o
H- resonances between n
= 2 and 3 hydrogen thresholds, the relativistic and QED corrections and the coupling effects between the high singlet and triplet
states are considered as first-order perturbations. We firstly obtain accurate non-relativistic resonant energies and widths
of fifteen 1P
o
resonances, and fifteen 3P
o
resonances. The fifteen 1P
o
resonances are classified to be
3
(2, 0)
-
n
( 4 ?
n
? 12) and
3
(1, 1)
+
n
( 3 ?
n
? 8). The fifteen 3P
o
resonances are classified to be
3
(2, 0)
+
n
( 3 ?
n
? 12) and
3
(1, 1)
-
n
( 4 ?
n
? 8). We found there exist six Feshbach resonances for
3
(2, 0)
-
n
(1P
o
) series, four Feshbach resonances for
3
(1, 1)
+
n
(1P
o
) series, seven Feshbach resonances for
3
(2, 0)
+
n
(3P
o
) series, and three Feshbach resonances for
3
(1, 1)
-
n
(1P
o
) series.
Received 22 February 2002 Published online 24 September 2002 相似文献
917.
918.
919.
920.
As a leading defence equipment company, the Dynamics Divisionof British Aerospace Defence Company (BAeDef(DD)) has experiencedthe worst effects of post-Coldwar defence cuts, a global recession,and a determination by the U.K. Government to achieve greatervalue for money in defence procurement. The major tenet of thisnew approach to defence prwurement was 'eyes on, hands off',promoting a shift of the management of project risks from theMinistry of Defence (MOD) to industry. Initial industry reactionwas sceptical but bxame increasingly compliant as tenderingrequirements included visibility of contractors' risk assessment.This paper describes the risk-assessment methodology createdby BAeDef(DD) to meet these changed conditions. The human and organizational aspects of these developments onrisk have helped create a pro-active risk-management cultureat BAeDef(DD). Continuous assessment of project risks providesthe impetus for wider thinking beyond risk-taking or risk-aversionpreferences, leading to greater realism in planning. Decisionsto implement risk resolution measures require competence incost-benefit analysis. The conditions to foster this new behaviourare better-informed senior management, with the rejection ofbad news eliminated at all levels, and the laying of a pathto becoming a learning company. 相似文献