全文获取类型
收费全文 | 4451篇 |
免费 | 180篇 |
国内免费 | 29篇 |
专业分类
化学 | 2450篇 |
晶体学 | 39篇 |
力学 | 177篇 |
数学 | 1130篇 |
物理学 | 864篇 |
出版年
2023年 | 40篇 |
2022年 | 69篇 |
2021年 | 126篇 |
2020年 | 127篇 |
2019年 | 157篇 |
2018年 | 155篇 |
2017年 | 144篇 |
2016年 | 194篇 |
2015年 | 150篇 |
2014年 | 205篇 |
2013年 | 337篇 |
2012年 | 309篇 |
2011年 | 324篇 |
2010年 | 177篇 |
2009年 | 196篇 |
2008年 | 238篇 |
2007年 | 204篇 |
2006年 | 156篇 |
2005年 | 126篇 |
2004年 | 129篇 |
2003年 | 93篇 |
2002年 | 79篇 |
2001年 | 69篇 |
2000年 | 47篇 |
1999年 | 33篇 |
1998年 | 26篇 |
1997年 | 30篇 |
1996年 | 47篇 |
1995年 | 38篇 |
1994年 | 32篇 |
1993年 | 42篇 |
1992年 | 34篇 |
1991年 | 37篇 |
1990年 | 31篇 |
1989年 | 21篇 |
1988年 | 26篇 |
1987年 | 34篇 |
1986年 | 36篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 25篇 |
1982年 | 30篇 |
1981年 | 29篇 |
1980年 | 21篇 |
1979年 | 37篇 |
1978年 | 25篇 |
1977年 | 21篇 |
1976年 | 23篇 |
1975年 | 20篇 |
1974年 | 14篇 |
排序方式: 共有4660条查询结果,搜索用时 17 毫秒
91.
92.
93.
Sanjiban Chakraborty Yamil J. Colón Randall Q. Snurr SonBinh T. Nguyen 《Chemical science》2015,6(1):384-389
Porous organic polymers (POPs) possessing meso- and micropores can be obtained by carrying out the polymerization inside a mesoporous silica aerogel template and then removing the template after polymerization. The total pore volume (tpv) and specific surface area (ssa) can be greatly enhanced by modifying the template (up to 210% increase for tpv and 73% for ssa) as well as by supercritical processing of the POPs (up to an additional 142% increase for tpv and an additional 32% for ssa) to include larger mesopores. The broad range of pores allows for faster transport of molecules through the hierarchically porous POPs, resulting in increased diffusion rates and faster gas uptake compared to POPs with only micropores. 相似文献
94.
This paper examines the cycling behavior of a deterministic and a stochastic version of the economic interpretation of the Lotka–Volterra model, the Goodwin model. We provide a characterization of orbits in the deterministic highly non-linear model. We then study a stochastic version, with Brownian noise introduced via a heterogeneous productivity factor. Existence conditions for a solution to the system are provided. We prove that the system produces cycles around a unique equilibrium point in finite time for general volatility levels, using stochastic Lyapunov techniques for recurrent domains. Numerical insights are provided. 相似文献
95.
Hoo Van Nguyen Naing Min Tun A. Yu. Kryukov I. M. Izvol’skii E. G. Rakov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(9):1559-1563
The “solubility” of oxidized carbon nanotubes depends on the acidity of aqueous solutions and increases drastically when pH increases from 1 (when it is almost zero) to 2. The same behavior is inherent in graphite and graphene oxides, the only difference lying in smoother increase in the solubility and in a wider range of pH. The reason for the change in solubility was shown to be cleavage of hydrogen bonds between the carboxyl groups of different particles and the behavior of the oxidized fragments (oxidation debris). It was concluded that the character of the dependences was dictated by the different geometries of nanoparticles and different distributions of carboxyl groups on their surface. 相似文献
96.
Transport in Porous Media - Compositional displacements in porous media, where chemical components partition between phases during a displacement, occur in flow processes such as surfactant... 相似文献
97.
Phu H. Dang Linh T. T. Nguyen Hue T. T. Nguyen Tho H. Le Truong N. V. Do Hai X. Nguyen 《Natural product research》2019,33(20):2883-2889
From an EtOAc-soluble fraction of the stem barks of Swintonia floribunda (Anacardiaceae), one new dimeric alkylresorcinol named integracin E (1), together with 4 known compounds (2–5) were isolated. Their chemical structures were elucidated based on the spectroscopic data interpretation. The absolute configuration of 1 was determined by the specific rotation analysis of its acid-catalyzed hydrolysis product. Compound 1 showed potent tyrosinase inhibitory activity with an IC50 value of 48.2?μM. 相似文献
98.
Tran Thu Ha Nguyen Hong Phong François-Xavier Le Dimet Hong Son Hoang 《Comptes Rendus Mecanique》2019,347(5):423-444
This article presents a correction method for a better resolution of the problem of estimating and predicting pollution, governed by Burgers' equations. The originality of the method consists in the introduction of an error function into the system's equations of state to model uncertainty in the model. The initial conditions and diffusion coefficients, present in the equations for pollution and concentration, and also those in the model error equations, are estimated by solving a data assimilation problem. The efficiency of the correction method is compared with that produced by the traditional method without introduction of an error function.Three test cases are presented in this study in order to compare the performances of the proposed methods. In the first two tests, the reference is the analytical solution and the last test is formulated as part of the “twin experiment”.The numerical results obtained confirm the important role of the model error equation for improving the prediction capability of the system, in terms of both accuracy and speed of convergence. 相似文献
99.
100.