全文获取类型
收费全文 | 14203篇 |
免费 | 1710篇 |
国内免费 | 1151篇 |
专业分类
化学 | 3634篇 |
晶体学 | 168篇 |
力学 | 1830篇 |
综合类 | 144篇 |
数学 | 2130篇 |
物理学 | 5895篇 |
无线电 | 3263篇 |
出版年
2024年 | 36篇 |
2023年 | 147篇 |
2022年 | 273篇 |
2021年 | 363篇 |
2020年 | 342篇 |
2019年 | 293篇 |
2018年 | 306篇 |
2017年 | 411篇 |
2016年 | 427篇 |
2015年 | 449篇 |
2014年 | 646篇 |
2013年 | 1050篇 |
2012年 | 832篇 |
2011年 | 1003篇 |
2010年 | 773篇 |
2009年 | 860篇 |
2008年 | 877篇 |
2007年 | 953篇 |
2006年 | 856篇 |
2005年 | 781篇 |
2004年 | 685篇 |
2003年 | 629篇 |
2002年 | 567篇 |
2001年 | 426篇 |
2000年 | 438篇 |
1999年 | 322篇 |
1998年 | 326篇 |
1997年 | 290篇 |
1996年 | 236篇 |
1995年 | 213篇 |
1994年 | 203篇 |
1993年 | 161篇 |
1992年 | 147篇 |
1991年 | 99篇 |
1990年 | 97篇 |
1989年 | 59篇 |
1988年 | 63篇 |
1987年 | 39篇 |
1986年 | 49篇 |
1985年 | 60篇 |
1984年 | 42篇 |
1983年 | 17篇 |
1982年 | 55篇 |
1981年 | 26篇 |
1980年 | 28篇 |
1979年 | 16篇 |
1978年 | 20篇 |
1977年 | 10篇 |
1976年 | 22篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
871.
The periodic risk model with investment 总被引:1,自引:0,他引:1
We consider a periodic risk model with the possibility of investing into a risky asset, given by a geometrical Brownian motion. The aim is to maximize the adjustment coefficient of the risk process. It is shown that the optimal investment strategy only depends on the averaged data of the model and is constant over time. Thus maximizing the adjustment coefficient is a very weak optimization criterion. 相似文献
872.
Significant influence of sample preparation on thermal decomposition of polyolefin-technological oil mixtures was proved during
tests. Samples of polymer-oil mixtures were prepared with two methods: reducing size and components mixing and soaking in
temperature 170°C. Soaking causes decreasing thermal stability of the charge. This fact manifests itself in decreasing of
thermal decomposition temperature in laboratory scale, as well as in change of characteristic decomposition temperatures during
thermogravimetric analyses. Data analysis was performed with the use of classic method based on Arrhenius kinetic equation
and three-parameter model. The influence of sample composition and preparation method on values of three-parameter equation
coefficients was observed. 相似文献
873.
Magnetic susceptibility and heat capacity due to spin-state excitations in LaCoO3 were analyzed with an irregular solution model composed of Co3+ ions in the low-spin ground state and in the high-spin excited state. An energy-levels diagram proposed by Ropka and Radvanskii
[1] was used for the high-spin excited state. This analysis showed that the entropy of mixing is less than that of ideal solutions
and the enthalpy of mixing is negative, indicating that the high-spin Co ions are arranged as far apart as possible. 相似文献
874.
In the mathematical modeling of population growth, and in particular of bacterial growth, parameters are either measured directly or determined by curve fitting. These parameters have large variability that depends on the experimental method and its inherent error, on differences in the actual population sample size used, as well as other factors that are difficult to account for. In this work the parameters that appear in the Monod kinetics growth model are considered random variables with specified distributions. A stochastic spectral representation of the parameters is used, together with the polynomial chaos method, to obtain a system of differential equations, which is integrated numerically to obtain the evolution of the mean and higher-order moments with respect to time. 相似文献
875.
在曲线的多分辨率分析基础上,构造了一种新的非线性三分多分辨率算法.并研究这个正则三分多分辨率算法的收敛性和稳定性,进一步,证明了小波参数的收敛性精密地依靠这个基本的多分辨率细分算法的收敛性. 相似文献
876.
V. V. Sargsyan Z. Kanokov G. G. Adamyan N. V. Antonenko 《Theoretical and Mathematical Physics》2008,156(3):1331-1346
Based on the non-Markovian quantum Langevin equations, we obtain time-dependent transport coefficients for an inverted oscillator
coupled linearly in the coordinate to a thermostat. We comparatively analyze the diffusion coefficients for harmonic and inverted
oscillators and study the role of quantum statistical effects in the passage through a parabolic barrier.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 156, No. 3, pp. 425–443, September, 2008. 相似文献
877.
The influence of poly(ethylene glycol) on the partition of a charged long chain spin probe between membranes and an external phase is studied. The partition coefficient is derived from the ESR spectra. Membranes of different properties are used (egg lecithin liposomes, erythrocytes) to differentiate between the influence of the external phase and the specific properties of the membrane.The partition coefficient is decreased in an exponential manner on increasing the PEG concentration, which indicates a lowering of the thermodynamic stability of the membranes. The determination of the change in the difference of the chemical potential is dependent on the PEG concentration.The membrane destabilization induced by PEG is caused in an indirect manner by a change of the chemical potential difference as result of the changed water structure and the osmotic pressure, surface tension and hydration of the membrane. This destabilization could be connected with the high fusogenic activity of PEG. 相似文献
878.
879.
通过引入带参数的指数积分并利用Bernoulli不等式以及改进了的Hlder不等式,对Hardy-Hilbert积分不等式作了有意义改进.特别,当p=2时,得到了经典的Hilbert积分不等式的一个很强的结果. 相似文献
880.
We consider in a new statement the inverse problem of the theory of vibrational spectra of molecules, in which a theoretical spectral curve directly gets closer to the experimental one. A coefficient of correlation between the curves is used as a criterion of the closeness of the curves and as a functional of the inverse problem. The procedure developed for solving the inverse problem makes it possible to dispense with the preliminary referencing of frequencies in an experimental spectrum and with its expansion into elementary absorption bands. 相似文献