全文获取类型
收费全文 | 409783篇 |
免费 | 4879篇 |
国内免费 | 1666篇 |
专业分类
化学 | 207750篇 |
晶体学 | 6796篇 |
力学 | 19228篇 |
综合类 | 65篇 |
数学 | 54600篇 |
物理学 | 127889篇 |
出版年
2019年 | 2777篇 |
2018年 | 11413篇 |
2017年 | 12217篇 |
2016年 | 8878篇 |
2015年 | 4259篇 |
2014年 | 5254篇 |
2013年 | 14024篇 |
2012年 | 14307篇 |
2011年 | 24402篇 |
2010年 | 15314篇 |
2009年 | 15194篇 |
2008年 | 21026篇 |
2007年 | 24399篇 |
2006年 | 10663篇 |
2005年 | 16355篇 |
2004年 | 11990篇 |
2003年 | 11101篇 |
2002年 | 8961篇 |
2001年 | 9271篇 |
2000年 | 7247篇 |
1999年 | 5555篇 |
1998年 | 4507篇 |
1997年 | 4379篇 |
1996年 | 4401篇 |
1995年 | 4163篇 |
1994年 | 3817篇 |
1993年 | 3626篇 |
1992年 | 4441篇 |
1991年 | 4329篇 |
1990年 | 4196篇 |
1989年 | 4208篇 |
1988年 | 4235篇 |
1987年 | 4255篇 |
1986年 | 4041篇 |
1985年 | 5271篇 |
1984年 | 5332篇 |
1983年 | 4304篇 |
1982年 | 4673篇 |
1981年 | 4583篇 |
1980年 | 4393篇 |
1979年 | 4738篇 |
1978年 | 4848篇 |
1977年 | 4801篇 |
1976年 | 4707篇 |
1975年 | 4387篇 |
1974年 | 4210篇 |
1973年 | 4419篇 |
1972年 | 2892篇 |
1968年 | 2738篇 |
1967年 | 2628篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
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
942.
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
943.
944.
945.
谐振子薛定谔方程的简单解法 总被引:2,自引:0,他引:2
物质的许多物理与化学性质都可以用线性谐振子模型解释,本文用简单的数学运算求解线性谐振子的薛定谔方程,避免了特殊函数等复杂的数学运算,得出了量子力学教材完全相同的结果。 相似文献
946.
Maria Marques Zhengtian Yu Marvin D. Rausch James C. W. Chien 《Journal of polymer science. Part A, Polymer chemistry》1995,33(16):2787-2793
4-Vinylcyclohexene (VCH) and cyclooctadiene (COD) were investigated as termonomers in EPDM (ethylene/propylene/diene) synthesis by using rac-ethylenebis (1-η5-indenyl) zir-conium dichloride ( 1 ) as a catalyst precursor. Homopolymerizations of VCH, vinylcycloh-exane and cyclohexene were compared. The parameter Kπκp, which is the apparent rate constant for Ziegler-Natta polymerization, is about the same for VCH and vinylcyclohexanebut is 10 times smaller for cyclohexene. Therefore, the linear olefinic double bond is more active than the cyclic internal double bond. VCH reduces ethylene polymerization rate but not propylene polymerization rate in copolymerizations. In terpolymerizations, VCH tends to suppress ethylene incorporation especially at elevated polymerization temperature and Lowers the polymer MW by about two-fold. COD has very low activity as a termonomer. © 1995 John Wiley & Sons, Inc. 相似文献
947.
The equilibrium and rate of solvent extraction of zinc chloride complexes from HCl solutions into benzene solutions of tributyl phosphate (TBP) have been studied. The extracted species are discussed in the light of the results. The extraction was found to be first order with respect to both Zn(II) and TBP, and zero order for HCl. The rate-controlling steps are discussed and the rate constants for these reactions are calculated. 相似文献
948.
949.
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
950.