全文获取类型
收费全文 | 14222篇 |
免费 | 2561篇 |
国内免费 | 1399篇 |
专业分类
化学 | 5689篇 |
晶体学 | 174篇 |
力学 | 1792篇 |
综合类 | 89篇 |
数学 | 1245篇 |
物理学 | 9193篇 |
出版年
2024年 | 17篇 |
2023年 | 85篇 |
2022年 | 158篇 |
2021年 | 196篇 |
2020年 | 287篇 |
2019年 | 301篇 |
2018年 | 320篇 |
2017年 | 418篇 |
2016年 | 522篇 |
2015年 | 568篇 |
2014年 | 753篇 |
2013年 | 1316篇 |
2012年 | 890篇 |
2011年 | 1046篇 |
2010年 | 798篇 |
2009年 | 985篇 |
2008年 | 1043篇 |
2007年 | 1054篇 |
2006年 | 946篇 |
2005年 | 804篇 |
2004年 | 720篇 |
2003年 | 633篇 |
2002年 | 578篇 |
2001年 | 489篇 |
2000年 | 510篇 |
1999年 | 409篇 |
1998年 | 361篇 |
1997年 | 267篇 |
1996年 | 296篇 |
1995年 | 234篇 |
1994年 | 181篇 |
1993年 | 141篇 |
1992年 | 152篇 |
1991年 | 114篇 |
1990年 | 78篇 |
1989年 | 64篇 |
1988年 | 80篇 |
1987年 | 59篇 |
1986年 | 46篇 |
1985年 | 50篇 |
1984年 | 43篇 |
1983年 | 16篇 |
1982年 | 33篇 |
1981年 | 31篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 220 毫秒
101.
Fiber-Optic Backscattering Profile Measurements for Determination of the Optical Coefficients of Turbid Media 总被引:1,自引:0,他引:1
A. M. Maiorova S. P. Kotova M. A. Rakhmatulin V. V. Yakutkin 《Journal of Russian Laser Research》2003,24(1):1-13
The necessity of using anisotropic approximation in techniques for determining optical parameters from the backscattered radiation profile is shown. A fiber-optic technique for simultaneous determination of the anisotropy parameter as well as the scattering and absorption coefficients of turbid media is proposed. It is based on the comparison of the experimental backscattered radiation profiles and those obtained by the numerical Monte Carlo method. 相似文献
102.
On the basis of the hydrodynamic equations for nonlinear elastic-gravity waves beneath a solid ice cover and their Hamiltonian representation, a three-wave kinetic equation for the time evolution of the wave spectrum is formulated. The properties of the kernel of the kinetic integral describing the nonlinear interactions between wave triplets are investigated. An algorithm for numerically calculating the kinetic integral is developed. The rate of nonlinear energy transfer over the wave spectrum is estimated quantitatively and its most important characteristics are found. 相似文献
103.
变系数计量经济学联立模型的局部线性工具向量估计及其性质 总被引:3,自引:1,他引:2
联立方程计量经济学模型在经济政策制定、经济结构分析和经济预测方面起着重要作用。本文首次提出了我国宏观经济的一类变系数联立模型,并建立了函数系数的局部线性工具向量估计,同时在时间点列固定设计、经济变量随机设计条件下,研究了估计量的大样本性质。与我国宏观经济经典线性联立模型相比,变系数联立模型拟合效果更优。另外它也有助于克服我国宏观经济数据不多而造成的非参数方法应用困难的现实情况。 相似文献
104.
A. D. Krisch 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):417-423
There will be a review of the history of polarized proton beams, and a discussion of the unexpected and still unexplained
large transverse spin effects found in several high-energy proton-proton spin experiments at the ZGS, AGS and Fermilab. Next,
there will be a discussion of present and possible future experiments on the violent elastic collisions of polarized protons
at IHEP-Protvino's 70GeV U-70 accelerator in Russia and the new high-intensity 50GeV J-PARC facility being built at Tokai
in Japan. 相似文献
105.
Monia Belhabri Jack Legrand Nathalie LeSauze Abdellah Arhaliass 《Particle & Particle Systems Characterization》2004,21(5):365-371
Emulsions are of great importance to industry. They are involved in many engineering operations, including chemical reactions, extraction, emulsification and suspension polymerization, etc. However, an important problem for these processes is how to control the size distribution of the dispersed phase. Indeed, off‐line analysis of the emulsion may generate uncertainties due to sampling and dilution of the product, which are likely to change the dispersion state and physico‐chemical properties. In this work, an on‐line optical method is proposed to characterize dispersed media in real flowing conditions. This method is based on the time‐analysis of back‐scattered light fluctuations. The present paper deals with the development of this method and its application to dispersions of alumina in water. The results obtained with the on‐line optical method are compared with those acquired by classical laser light scattering and microscopy. 相似文献
106.
Jonatan Lenells 《Journal of Mathematical Analysis and Applications》2007,325(2):1468-1478
We use the inverse scattering transform to show that a solution of the Camassa-Holm equation is identically zero whenever it vanishes on two horizontal half-lines in the x-t space. In particular, a solution that has compact support at two different times vanishes everywhere, proving that the Camassa-Holm equation has infinite propagation speed. 相似文献
107.
108.
副品红共振光散射法测定脱氧核糖核酸 总被引:3,自引:0,他引:3
本文基于脱氧核糖核酸 (DNA)对有机染料副品红的共振光散射的增强效应 ,拟定了一种测定DNA的共振光散射法。在pH =0 5~ 1 5范围内 ,有机染料副品红于 35 5nm处的共振光散射强度被DNA强烈增强 ,且增强程度与DNA浓度呈线性关系 ,线性范围为 0 10~ 15 μg·mL- 1 ,检出限可达 36ng·mL- 1 。该方法简便、快速、具有较高的灵敏度和准确度 ,且线性范围较宽。将该方法用于混合样品中DNA的测定 ,结果令人满意。 相似文献
109.
Deák L. Bottyán L. Major M. Nagy D. L. Spiering H. Szilágyi E. Tanczikó F. 《Hyperfine Interactions》2002,144(1-4):45-52
Hyperfine Interactions - Synchrotron Mössbauer Reflectometry (SMR), the grazing incidence nuclear resonant scattering of synchrotron radiation, can be applied to perform depth-selective phase... 相似文献
110.
M. Iuga G. Steinle-Neumann J. Meinhardt 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):127-133
Athermal elasticity for some ceramic materials (α-Al2O3,
SiC (α and β phases), TiO2 (rutile and anatase),
hexagonal AlN and TiB2, cubic BN and CaF2, and monoclinic
ZrO2) have been investigated via density functional theory.
Energy-volume equation-of-state computations to obtain the zero pressure
equilibrium volume and bulk modulus as well as computations of the full
elastic constant tensor of these ceramics at the experimental zero pressure
volume have been performed. The present results for the single crystal
elasticity are in good agreement with experiments both for the aggregate
properties (bulk and shear modulus) and the elastic anisotropy. In contrast,
a considerable discrepancy for the zero pressure bulk modulus of some
ceramics evaluated from the energy-volume fit to the computational zero
pressure volume has been observed. 相似文献