全文获取类型
收费全文 | 26605篇 |
免费 | 4728篇 |
国内免费 | 2842篇 |
专业分类
化学 | 14404篇 |
晶体学 | 208篇 |
力学 | 1687篇 |
综合类 | 324篇 |
数学 | 6076篇 |
物理学 | 11476篇 |
出版年
2024年 | 79篇 |
2023年 | 411篇 |
2022年 | 727篇 |
2021年 | 803篇 |
2020年 | 936篇 |
2019年 | 844篇 |
2018年 | 763篇 |
2017年 | 914篇 |
2016年 | 1256篇 |
2015年 | 1211篇 |
2014年 | 1609篇 |
2013年 | 2329篇 |
2012年 | 1685篇 |
2011年 | 1872篇 |
2010年 | 1565篇 |
2009年 | 1726篇 |
2008年 | 1888篇 |
2007年 | 1868篇 |
2006年 | 1581篇 |
2005年 | 1443篇 |
2004年 | 1177篇 |
2003年 | 1058篇 |
2002年 | 853篇 |
2001年 | 659篇 |
2000年 | 655篇 |
1999年 | 575篇 |
1998年 | 541篇 |
1997年 | 435篇 |
1996年 | 313篇 |
1995年 | 311篇 |
1994年 | 297篇 |
1993年 | 207篇 |
1992年 | 195篇 |
1991年 | 155篇 |
1990年 | 126篇 |
1989年 | 130篇 |
1988年 | 130篇 |
1987年 | 109篇 |
1986年 | 87篇 |
1985年 | 124篇 |
1984年 | 85篇 |
1983年 | 46篇 |
1982年 | 75篇 |
1981年 | 51篇 |
1980年 | 41篇 |
1979年 | 43篇 |
1978年 | 47篇 |
1977年 | 31篇 |
1976年 | 26篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
We extend the matrix version of Cochran's statistical theorem to outer inverses of a matrix. As applications, we investigate the Wishartness and independence of matrix quadratic forms for Kronecker product covariance structures. 相似文献
62.
Within the framework of a piecewise homogeneous body model, with the use of three-dimensional geometrically nonlinear exact equations of elasticity theory, a method for determining the stress—strain state in unidirectional fibrous composites with locally curved fibers is developed for the case where the interaction between the fibers is neglected. All the investigations are carried out for an infinite elastic body containing a single locally curved fiber. Numerical results illustrating the effect of geometrical nonlinearity on the distribution of the self-balanced normal and shear stresses acting on the interface and arising as a result of local curving of the fiber are presented.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 433–448, July–August, 2005. 相似文献
63.
YBa2Cu3O7-x (YBCO) bulk is one of the most important high temperature superconducting materials for magnetic levitation applications, because it has a high magnetic irreversibility field Hirr at liquid nitrogen temperature, and can grow into large grains. The levitation force of YBCO bulk is proportional to the critical current density (Jc) and grain radius (r)[1], so higher Jc and r are appreciated for YBCO bulks to achieve higher levitation force. Now single-domain YBCO bulks up to s… 相似文献
64.
T Utsunomiya M. Sekine 《International Journal of Infrared and Millimeter Waves》2005,26(11):1651-1660
We have conducted a millimeter wave propagation experiment at 103 GHz (2.9 mm) on a propagation path of 390 m. The results
were compared with the rain attenuation calculations from the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions
for raindrop-size. It has been shown that the Weibull distribution has a good agreement with the experiments. 相似文献
65.
The rain attenuation was calculated by using the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions for raindrop-size. The results were compared with the recent measurements from 8 to 312.5 GHz at the rain rate R = 50mm/hr. Especially, the Weibull distribution has a good agreement with the measurements at 312.5 GHz (0.96 mm) in the submillimeter wavelength. Specific attenuation values from 1 to 1000 GHz were calculated for a rain temperature of –10°C, 0°C and 20°C by using the Weibull distribution. 相似文献
66.
67.
相对论重离子碰撞实验中混合事件方法的研究 总被引:1,自引:0,他引:1
把RQMD(Relativistic Quantum Molecular Dynamics)产生器产生的数据输入作为原始事例取样,讨论了在比较复杂的背景情况下,一种新的混合事件方法,用以证实在相对论重离子碰撞实验中高能量激发共振态的存在.并以共振态重子Δ++为例演示了这一方法的应用. 相似文献
68.
C. H. Hesse 《Statistical Inference for Stochastic Processes》2007,10(1):75-95
In this work the Cauchy problem for the one-dimensional heat equation is considered. In contrast to existing literature it
is assumed that the initial state f is unknown and that information regarding f is obtained by some process of measurement. To enhance realism, both measurement errors and missing data are allowed for.
Under assumptions on f in the Fourier-domain first an approximation to f is derived from the data by means of a novel uncertainty principle. Then, it is studied how this perturbation in the initial
state propagates with time.
相似文献
69.
SUN Qiyu 《数学年刊B辑(英文版)》2003,24(3):367-386
In this paper, the author at first develops a method to study convergence of the cascade algorithm in a Banach space without stable assumption on the initial (see Theorem 2.1), and then applies the previous result on the convergence to characterizing compactly supported refinable distributions in fractional Sobolev spaces and Holder continuous spaces (see Theorems 3.1, 3.3, and 3.4). Finally the author applies the above characterization to choosing appropriate initial to guarantee the convergence of the cascade algorithm (see Theorem 4.2). 相似文献
70.
乌桕类可可脂结晶过程中表现体积变化 总被引:1,自引:0,他引:1
为了解乌桕类可可脂(CTCBE)缓冷结晶横向胀罐爆裂原因,研究CTCBE结晶过程中的膨胀特性,采用流体静力法测试了不同等温结晶条件下CTCBE结晶形成的表观密度和表观体积及其横纵向膨胀状况。结果表明,CTCBE缓冷结晶后形成外部和中部两个晶区。在5-25℃的各等温结晶范围内,当结晶温度增加时,外部结晶区域减小、表观密度变化不大;中部结晶区域增大、表观密度明显减小,CTCBE的表观体积、横向、纵向膨胀率均增大,膨胀横向大于纵向。进一步表明CTCBE在自然缓冷固化的表观体积根本上由其结晶温度决定。为有效防止横向胀罐,自然缓冷固化温度应低于10℃。 相似文献