全文获取类型
收费全文 | 11491篇 |
免费 | 931篇 |
国内免费 | 754篇 |
专业分类
化学 | 3169篇 |
晶体学 | 62篇 |
力学 | 1147篇 |
综合类 | 199篇 |
数学 | 6869篇 |
物理学 | 1730篇 |
出版年
2024年 | 11篇 |
2023年 | 92篇 |
2022年 | 201篇 |
2021年 | 292篇 |
2020年 | 288篇 |
2019年 | 288篇 |
2018年 | 232篇 |
2017年 | 351篇 |
2016年 | 414篇 |
2015年 | 310篇 |
2014年 | 549篇 |
2013年 | 884篇 |
2012年 | 561篇 |
2011年 | 704篇 |
2010年 | 587篇 |
2009年 | 760篇 |
2008年 | 753篇 |
2007年 | 841篇 |
2006年 | 662篇 |
2005年 | 564篇 |
2004年 | 541篇 |
2003年 | 479篇 |
2002年 | 432篇 |
2001年 | 336篇 |
2000年 | 328篇 |
1999年 | 279篇 |
1998年 | 257篇 |
1997年 | 221篇 |
1996年 | 173篇 |
1995年 | 117篇 |
1994年 | 106篇 |
1993年 | 75篇 |
1992年 | 63篇 |
1991年 | 60篇 |
1990年 | 54篇 |
1989年 | 27篇 |
1988年 | 37篇 |
1987年 | 27篇 |
1986年 | 13篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 32篇 |
1982年 | 23篇 |
1981年 | 26篇 |
1980年 | 23篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 5篇 |
1974年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The paper summarizes recent advances in the theory of geometric stable (GS) distributions. The results presented include parametrizations, characterizations, mixture representations, properties, asymptotic and convergent series expansions of densities and distribution functions, moments and tail behavior, simulation, and estimation. 相似文献
992.
A modification of the material law associated with the well‐known Biot system as suggested by Murad and Cushman (Int. J. Eng. Sci. 1996; 34(3):313–338) and first investigated by Showalter (J. Math. Anal. Appl. 2000; 251(1):310–340) is reconsidered, generalized and analysed in the light of a new approach to a comprehensive class of evolutionary problems. The framework allows a uniform approach to problems involving general anisotropic, inhomogeneous, non‐smooth media thus covering, for example, transmission problems in layered materials. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
993.
M. Mehdizadeh Khalsaraei 《Journal of Computational and Applied Mathematics》2010,235(1):137-143
In this paper, we investigate the positivity property for a class of 2-stage explicit Runge-Kutta (RK2) methods of order two when applied to the numerical solution of special nonlinear initial value problems (IVPs) for ordinary differential equations (ODEs). We also pay particular attention to monotonicity property. We obtain new results for positivity which are important in practical applications. We provide some numerical examples to illustrate our results. 相似文献
994.
995.
Jennifer M. O'Donnell Eric W. Kaler 《Journal of polymer science. Part A, Polymer chemistry》2010,48(3):604-613
A simplified kinetic model for RAFT microemulsion polymerization has been developed to facilitate the investigation of the effects of slow fragmentation of the intermediate macro‐RAFT radical, termination reactions, and diffusion rate of the chain transfer agent to the locus of polymerization on the control of the polymerization and the rate of monomer conversion. This simplified model captures the experimentally observed decrease in the rate of polymerization, and the shift of the rate maximum to conversions less than the 39% conversion predicted by the Morgan model for uncontrolled microemulsion polymerizations. The model shows that the short, but finite, lifetime of the intermediate macro‐RAFT radical (1.3 × 10?4–1.3 × 10?2 s) causes the observed rate retardation in RAFT microemulsion polymerizations of butyl acrylate with the chain transfer agent methyl‐2‐(O‐ethylxanthyl)propionate. The calculated magnitude of the fragmentation rate constant (kf = 4.0 × 101–4.0 × 103 s?1) is greater than the literature values for bulk RAFT polymerizations that only consider slow fragmentation of the macro‐RAFT radical and not termination (kf = 10?2 s?1). This is consistent with the finding that slow fragmentation promotes biradical termination in RAFT microemulsion polymerizations. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 604–613, 2010 相似文献
996.
In this paper the concept of lower and upper solutions combined with the fixed point theorem of Bohnnenblust–Karlin is used to investigate the existence of solutions for a class of the initial value problem for impulsive differential inclusions involving the Caputo fractional derivative. 相似文献
997.
南城县学龄儿童发锌水平的研究 总被引:1,自引:1,他引:0
采用原子吸收光谱法测定了南城县城关小学540名6-14岁学龄儿童头发中锌的水平。将所得数据在计算机上进行统计分析。结果表明,本资料属非正态性资料,样本中位数为108.3×10-6,其中男性为103.85×10-6,女性为111.5×10-6。男女间有显著差别。年龄与发锌值之间呈正相关。 相似文献
998.
Received May 28, 1996 / Revised version received May 1, 1998 Published online October 9, 1998 相似文献
999.
1000.
Núñez-Regueira L. Rodríguez-Añón J. Proupín-Castiñeiras J. Romero-García A. 《Journal of Thermal Analysis and Calorimetry》2001,66(1):281-292
Calorific values and flammability changes during a year for forest waste originating from silviculture task in Galicia (NW
Spain) are reported. These waste materials are becoming to be used as alternative fuels.
The present study was made on several hardwood forest species. These forest species occupy nowadays approximately 30% of the
total forest surface of Galicia.
Calorific values were measured by static bomb calorimeter in an oxygen atmosphere. Flammability was determined using a standard
epiradiator. Simultaneously, some other parameters such as elementary chemical composition, heavy metal contents, moisture,
density, ash percentage after combustion in the bomb, and main bioclimatic characteristics, were also determined.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献