全文获取类型
收费全文 | 15229篇 |
免费 | 1998篇 |
国内免费 | 1212篇 |
专业分类
化学 | 3264篇 |
晶体学 | 70篇 |
力学 | 1328篇 |
综合类 | 322篇 |
数学 | 7361篇 |
物理学 | 6094篇 |
出版年
2023年 | 128篇 |
2022年 | 226篇 |
2021年 | 367篇 |
2020年 | 353篇 |
2019年 | 291篇 |
2018年 | 336篇 |
2017年 | 477篇 |
2016年 | 529篇 |
2015年 | 401篇 |
2014年 | 811篇 |
2013年 | 1087篇 |
2012年 | 850篇 |
2011年 | 915篇 |
2010年 | 751篇 |
2009年 | 922篇 |
2008年 | 1038篇 |
2007年 | 1016篇 |
2006年 | 892篇 |
2005年 | 841篇 |
2004年 | 677篇 |
2003年 | 680篇 |
2002年 | 631篇 |
2001年 | 499篇 |
2000年 | 480篇 |
1999年 | 449篇 |
1998年 | 424篇 |
1997年 | 327篇 |
1996年 | 293篇 |
1995年 | 255篇 |
1994年 | 214篇 |
1993年 | 150篇 |
1992年 | 147篇 |
1991年 | 112篇 |
1990年 | 91篇 |
1989年 | 88篇 |
1988年 | 82篇 |
1987年 | 78篇 |
1986年 | 57篇 |
1985年 | 92篇 |
1984年 | 58篇 |
1983年 | 38篇 |
1982年 | 50篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 38篇 |
1978年 | 36篇 |
1977年 | 20篇 |
1976年 | 23篇 |
1975年 | 10篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
A sample of 1233 events is used to study the general characteristics of {}^{16}O-Em interactions at 4.5 A GeV/c. Multiplicity and angular distributions of slow particles and correlations among them are discussed. The present data are compared with the corresponding results from the interactions of other projectiles at the same energy and also the same projectile at different energies. The results indicate that black particle production is independent of the energy and mass of the projectile, but for grey particles it is dependent on the mass of projectile. 相似文献
32.
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
33.
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
34.
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
35.
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
36.
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
37.
38.
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
39.
Zi‐Niu Wu 《国际流体数值方法杂志》2005,48(5):541-564
The widely used locally adaptive Cartesian grid methods involve a series of abruptly refined interfaces. In this paper we consider the influence of the refined interfaces on the steady state errors for second‐order three‐point difference approximations of flow equations. Since the various characteristic components of the Euler equations should behave similarly on such grids with regard to refinement‐induced errors, it is sufficient enough to conduct the analysis on a scalar model problem. The error we consider is a global error, different to local truncation error, and reflects the interaction between multiple interfaces. The steady state error will be compared to the errors on smooth refinement grids and on uniform grids. The conclusion seems to support the numerical findings of Yamaleev and Carpenter (J. Comput. Phys. 2002; 181: 280–316) that refinement does not necessarily reduce the numerical error. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
40.
A time discrete scheme is used to approximate the solution toa phase field system of PenroseFife type with a non-conservedorder parameter. An a posteriori error estimate is presentedthat allows the estimation of the difference between continuousand semidiscrete solutions by quantities that can be calculatedfrom the approximation and given data. 相似文献