全文获取类型
收费全文 | 6457篇 |
免费 | 505篇 |
国内免费 | 252篇 |
专业分类
化学 | 367篇 |
晶体学 | 13篇 |
力学 | 1107篇 |
综合类 | 27篇 |
数学 | 3299篇 |
物理学 | 2401篇 |
出版年
2024年 | 11篇 |
2023年 | 31篇 |
2022年 | 77篇 |
2021年 | 98篇 |
2020年 | 178篇 |
2019年 | 163篇 |
2018年 | 142篇 |
2017年 | 148篇 |
2016年 | 130篇 |
2015年 | 150篇 |
2014年 | 354篇 |
2013年 | 761篇 |
2012年 | 303篇 |
2011年 | 410篇 |
2010年 | 364篇 |
2009年 | 413篇 |
2008年 | 438篇 |
2007年 | 429篇 |
2006年 | 356篇 |
2005年 | 217篇 |
2004年 | 243篇 |
2003年 | 201篇 |
2002年 | 177篇 |
2001年 | 176篇 |
2000年 | 164篇 |
1999年 | 114篇 |
1998年 | 125篇 |
1997年 | 95篇 |
1996年 | 103篇 |
1995年 | 91篇 |
1994年 | 66篇 |
1993年 | 72篇 |
1992年 | 54篇 |
1991年 | 57篇 |
1990年 | 48篇 |
1989年 | 39篇 |
1988年 | 27篇 |
1987年 | 31篇 |
1986年 | 20篇 |
1985年 | 13篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1975年 | 3篇 |
排序方式: 共有7214条查询结果,搜索用时 15 毫秒
71.
Micelles of different amphiphiles adopt different shapes and internal packing arrangements in water, depending on their chemical
structures and the conditions of the medium. Two microenvironmental features, namely the polarity and the microviscosity that
the aggregate offers to a solubilized molecule, have been monitored using extrinsic fluorescence probes. While the differences
between micelles of spherical and rod-like shapes are not always distinct, stacked micelles and peptide micelles offer distinctly
lower polarity and higher microviscosity to solubilizates than the others. 相似文献
72.
73.
Hiroshi Ueyama 《Journal of statistical physics》1980,22(1):1-26
Based on the assumption of a kinetic equation in space, a stochastic differential equation of the one-particle distribution is derived without the use of the linear approximation. It is just the Boltzmann equation with a Langevin-fluctuating force term. The result is the general form of the linearized Boltzmann equation with fluctuations found by Bixon and Zwanzig and by Fox and Uhlenbeck. It reduces to the general Landau-Lifshitz equations of fluid dynamics in the presence of fluctuations in a similar hydrodynamic approximation to that used by Chapman and Enskog with respect to the Boltzmann equation.This work received financial support from the Alexander von Humboldt Foundation. 相似文献
74.
V.L. Furer A.E. Vandyukov J.P. Majoral A.M. Caminade V.I. Kovalenko 《Vibrational Spectroscopy》2006,40(2):155-160
The Raman (10–3500 cm−1) and infrared (150–3500 cm−1) spectra have been recorded for tris(4-oxibenzaldehyde)thiophosphate. This compound includes structural parts of elementoorganic dendrimers: a core and terminal aldehyde groups. The structural optimization and normal mode analysis are performed for elementoorganic dendrimer on the basis of the ab initio density functional theory. It is found that the dendrimer exist in a single stable conformation with planar C6H4CHO fragments. Our calculations show that conformer with one trans and two gauche 4-oxibenzaldehyde groups is realized. All these observations suggest that steric congestion does not disturb the construction of dendrimers even for the highest generations, and that terminal groups are readily available for further reactions. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the studied dendrimers. 相似文献
75.
Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1 ng ml−1, which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50 ng ml−1 of glyburide in plasma and the method can be used for quantitative analysis of glyburide. 相似文献
76.
77.
F. Thuijsman S. H. Tijs O. J. Vrieze 《Journal of Optimization Theory and Applications》1991,69(2):311-324
We examine stochastic games with finite state and action spaces. For the -discounted case, as well as for the irreducible limiting average case, we show the existence of trembling-hand perfect equilibria and give characterizations of those equilibria. In the final section, we give an example which illustrates that the existence of stationary limiting average equilibria in a nonirreducible stochastic game does not imply the existence of a perfect limiting average equilibrium.Support was provided by the Netherlands Organization for Scientific Research NWO via the Netherlands Foundation for Mathematics SMC, Project 10-64-10. 相似文献
78.
K. Marti 《Mathematical Methods of Operations Research》1992,36(3):259-294
In engineering and economics often a certain vectorx of inputs or decisions must be chosen, subject to some constraints, such that the expected costs (or loss) arising from the deviation between the outputA() x of a stochastic linear systemxA()x and a desired stochastic target vectorb() are minimal. Hence, one has the following stochastic linear optimization problem minimizeF(x)=Eu(A()x b()) s.t.xD, (1) whereu is a convex loss function on
m
, (A(), b()) is a random (m,n + 1)-matrix, E denotes the expectation operator andD is a convex subset of
n
. Concrete problems of this type are e.g. stochastic linear programs with recourse, error minimization and optimal design problems, acid rain abatement methods, problems in scenario analysis and non-least square regression analysis.Solving (1), the loss functionu should be exactly known. However, in practice mostly there is some uncertainty in assigning appropriate penalty costs to the deviation between the outputA ()x and the targetb(). For finding in this situation solutions hedging against uncertainty a set of so-called efficient points of (1) is defined and a numerical procedure for determining these compromise solutions is derived. Several applications are discussed. 相似文献
79.
80.
利用破产理论和随机控制理论研究保险基金最优投资策略,建立生存概率最大化的目标函数,得到最优投资策略满足的随机微分方程;在初始金逼近0时得到保险基金的最优投资策略的显示解;采用递推算法,得到初始准备金为任意值时的最优投资策略. 相似文献