全文获取类型
收费全文 | 681篇 |
免费 | 14篇 |
国内免费 | 10篇 |
专业分类
化学 | 498篇 |
力学 | 8篇 |
数学 | 60篇 |
物理学 | 139篇 |
出版年
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 6篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 10篇 |
2013年 | 19篇 |
2012年 | 29篇 |
2011年 | 36篇 |
2010年 | 14篇 |
2009年 | 18篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 24篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 16篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 16篇 |
1978年 | 24篇 |
1977年 | 20篇 |
1976年 | 13篇 |
1975年 | 17篇 |
1974年 | 6篇 |
1973年 | 13篇 |
1971年 | 4篇 |
1968年 | 4篇 |
1943年 | 4篇 |
排序方式: 共有705条查询结果,搜索用时 46 毫秒
81.
Jon M. Conrad 《Natural Resource Modeling》1990,4(4):555-561
MATHEMATICAL BIOECONOMICS: THE OPTIMAL MANAGEMENT OF RENEWABLE RESOURCES, Colin W. Clark, Second Edition, John Wiley & Sons, Inc., New York, 1990 相似文献
82.
OFHC copper specimens of 39 μm grain size were deformed to small strains (up to 8%) in tension, torsion and combined tension-torsion at 300 K and the resulting dislocation structures, distributions and densities were determined using transmission electron microscopy. Employing the von Mises yield criterion and the plastic-work hypothesis good agreement was obtained for the three testing conditions for (i) equivalent stress gs vs equivalent strain g3p curves, (ii) the dislocation structure, distribution and density ρ as a function of g3p, and (iii) gs as a function of . Furthermore, upon comparing the gs vs curve for polycrystalline copper with the τRSS vs curve for single crystals, an average Taylor factor M= (σ/τRSS) of approximately 3.2 was obtained, which is in good accord with that predicted theoretically for FCC metals. Almost equally good correlations for the stressstrain curves and for the dislocation density were obtained on the basis of maximum shear stress τmax and maximum shear strain γpmax as on the basis of gs and g3P. Therefore, the present results do not permit a positive decision on the question whether the dislocation density correlates better with gs and g3P or with τmax and γPmax.A single test in which the direction of straining in torsion was reversed yielded a density and distribution of dislocations (and a corresponding value of gs) equivalent to those that developed at a smaller strain in unidirectional straining. 相似文献
83.
84.
Received: 22 November 1998 相似文献
85.
86.
William K. Hagmann Laura A. O'Grady Conrad P. Dorn James P. Springer 《Journal of heterocyclic chemistry》1986,23(3):673-677
A one-pot synthesis of the 11H-dibenzo[b,e]1,4]dioxepin ring system from catechol and an o-chlorobenzyl chloride is described. Friedel-Crafts acylation occurs at the 7-position as shown by X-ray analysis. 相似文献
87.
88.
89.
90.
This report details an approach to improve the accuracy of free energy difference estimates using thermodynamic integration data (slope of the free energy with respect to the switching variable λ) and its application to calculating solvation free energy. The central idea is to utilize polynomial fitting schemes to approximate the thermodynamic integration data to improve the accuracy of the free energy difference estimates. Previously, we introduced the use of polynomial regression technique to fit thermodynamic integration data (Shyu and Ytreberg, J Comput Chem, 2009, 30, 2297). In this report we introduce polynomial and spline interpolation techniques. Two systems with analytically solvable relative free energies are used to test the accuracy of the interpolation approach. We also use both interpolation and regression methods to determine a small molecule solvation free energy. Our simulations show that, using such polynomial techniques and nonequidistant λ values, the solvation free energy can be estimated with high accuracy without using soft‐core scaling and separate simulations for Lennard‐Jones and partial charges. The results from our study suggest that these polynomial techniques, especially with use of nonequidistant λ values, improve the accuracy for ΔF estimates without demanding additional simulations. We also provide general guidelines for use of polynomial fitting to estimate free energy. To allow researchers to immediately utilize these methods, free software and documentation is provided via http://www.phys.uidaho.edu/ytreberg/software . © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献