全文获取类型
收费全文 | 28679篇 |
免费 | 2661篇 |
国内免费 | 1889篇 |
专业分类
化学 | 3878篇 |
晶体学 | 80篇 |
力学 | 1095篇 |
综合类 | 304篇 |
数学 | 5542篇 |
物理学 | 6317篇 |
综合类 | 16013篇 |
出版年
2024年 | 65篇 |
2023年 | 232篇 |
2022年 | 502篇 |
2021年 | 610篇 |
2020年 | 538篇 |
2019年 | 494篇 |
2018年 | 518篇 |
2017年 | 658篇 |
2016年 | 699篇 |
2015年 | 784篇 |
2014年 | 1422篇 |
2013年 | 1495篇 |
2012年 | 1590篇 |
2011年 | 1718篇 |
2010年 | 1361篇 |
2009年 | 1589篇 |
2008年 | 1653篇 |
2007年 | 1936篇 |
2006年 | 1638篇 |
2005年 | 1551篇 |
2004年 | 1332篇 |
2003年 | 1256篇 |
2002年 | 1179篇 |
2001年 | 998篇 |
2000年 | 949篇 |
1999年 | 852篇 |
1998年 | 818篇 |
1997年 | 626篇 |
1996年 | 586篇 |
1995年 | 506篇 |
1994年 | 490篇 |
1993年 | 413篇 |
1992年 | 363篇 |
1991年 | 311篇 |
1990年 | 255篇 |
1989年 | 265篇 |
1988年 | 221篇 |
1987年 | 188篇 |
1986年 | 109篇 |
1985年 | 91篇 |
1984年 | 57篇 |
1983年 | 38篇 |
1982年 | 53篇 |
1981年 | 29篇 |
1980年 | 26篇 |
1979年 | 32篇 |
1978年 | 35篇 |
1977年 | 22篇 |
1976年 | 21篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 687 毫秒
51.
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
52.
53.
L. Brian Lawrence 《Transactions of the American Mathematical Society》2005,357(7):2535-2556
Working in ZFC, we give an example as indicated in the title.
54.
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
55.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献
56.
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
57.
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
58.
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
59.
60.
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