全文获取类型
收费全文 | 7103篇 |
免费 | 990篇 |
国内免费 | 705篇 |
专业分类
化学 | 2313篇 |
晶体学 | 94篇 |
力学 | 1009篇 |
综合类 | 103篇 |
数学 | 1419篇 |
物理学 | 3860篇 |
出版年
2024年 | 14篇 |
2023年 | 61篇 |
2022年 | 124篇 |
2021年 | 157篇 |
2020年 | 145篇 |
2019年 | 141篇 |
2018年 | 130篇 |
2017年 | 205篇 |
2016年 | 265篇 |
2015年 | 215篇 |
2014年 | 355篇 |
2013年 | 496篇 |
2012年 | 400篇 |
2011年 | 480篇 |
2010年 | 412篇 |
2009年 | 439篇 |
2008年 | 458篇 |
2007年 | 511篇 |
2006年 | 436篇 |
2005年 | 419篇 |
2004年 | 357篇 |
2003年 | 322篇 |
2002年 | 320篇 |
2001年 | 244篇 |
2000年 | 230篇 |
1999年 | 198篇 |
1998年 | 169篇 |
1997年 | 144篇 |
1996年 | 130篇 |
1995年 | 109篇 |
1994年 | 113篇 |
1993年 | 101篇 |
1992年 | 76篇 |
1991年 | 76篇 |
1990年 | 49篇 |
1989年 | 39篇 |
1988年 | 38篇 |
1987年 | 20篇 |
1986年 | 21篇 |
1985年 | 27篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 31篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 11篇 |
1973年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有8798条查询结果,搜索用时 15 毫秒
71.
72.
Nusselt number correlations for heat transfer to small spheres in thermal plasma flows 总被引:1,自引:0,他引:1
Seven different equations predicting heat transfer rates to small spheres in plasma flows are examined considering argon and nitrogan as plasma gases from 300 to 21,000 K at 1 atm. For argon there is a general consensus up to 9000 K, beyond which wide deviations in behavior occur. For nitrogen, the seven correlations are in good agreement up to 4000 K, but show substantial deviations beyond this value. Comparisons with the sparsely available experimental data are made for argon from 300 to 17,000 K and for nitrogen up to 5500 K. Disagreement between the various correlations and experiment can exceed one order of magnitude. 相似文献
73.
74.
75.
For the methylsilsesquioxane film whose optical birefringence is almost zero, it was recently reported that its vertical thermal expansion coefficient (CTE) was approximately one order of magnitude larger than the lateral CTE. Though the birefringence is not an absolute predictor of anisotropic behavior, the discrepancy in both the CTEs was so remarkable that it was essential to investigate whether the anisotropy was intrinsic property or not. If the effect of Poisson's ratio is considered in the calculation of the vertical CTE and when elastic modulus measured by surface acoustic wave spectroscopy is used in the assessment of the lateral CTE, both the CTEs are coincident with each other. Therefore, it can be concluded that the discrepancy in the CTEs can be attributed to a higher in‐plane polymer chain orientation but it can also arise from the misleadingly assumed modulus and Poisson's ratio. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3109–3120, 2006 相似文献
76.
B. W. Skews 《Shock Waves》1994,4(3):145-154
A study to determine the general gas dynamic behaviour associated with the impact of a shock wave on a porous wedge has been undertaken. A number of interesting features are noted. The pattern of wave reflection is shown to be significantly affected by the inflow of gas into the wedge. This has the effect of reducing the triple point trajectory angle for cases of Mach reflection and for strongly reducing the reflection angle in regular reflection. The permeability of the wedge has a significant effect on the strength of the reflected wave and in some cases this wave can be attenuated to the extent that it is almost eradicated. Pressure measurements taken under the wedge are characterized by oscillations which are of similar shape, for a given wedge, over a range of shock wave Mach numbers. It is shown that the wave transmitted into the wedge is attenuated to varying degrees depending on the material properties, and that for weak incident waves the mean propagation velocity can be less than the sound speed in the pore fluid. Photographs taken using a specially constructed wedge which allows the transmitted wave to be visualised, show that the transmitted wave is nearly plane.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
77.
用高密度等离子体模型可以计算出一整套输运参数,并且在很宽的等离子体温度和密度范围内有合理的精度,可广泛应用于Z箍缩等离子体、激光聚变和磁约束聚变等领域,并将这个模型计算出的各种输运参数拟合成了实用的公式。 相似文献
78.
Yang Lingxia Ge Debiao Wei Bing 《International Journal of Infrared and Millimeter Waves》2003,24(11):1893-1897
A modified formulation for fringe component of diffraction coefficient is implemented to TD-EEC method. An example of diffraction by perfectly conducting plate is used to illustrate our scheme. Comparing with the FDTD results we observe that the improved expression for fringe component is more accurate than that of Michaeli's formulation. This high frequency time domain technique is available for treating the bistatic scattering problems for millimeter waves. 相似文献
79.
复合广义齐次Poisson过程的多险种破产概率 总被引:11,自引:0,他引:11
于文广 《应用数学与计算数学学报》2003,17(2):63-69
本文推广了经典的复合泊松风险模型,建立了两类复合广义齐次poisson过程的多险种破产模型.对于新模型,我们得到了初始资本为u的破产概率φ(u)的精确表达式以及特殊情况下φ(0)的表达式,并且导出了调节系数方程和调节系数R的上下界. 相似文献
80.
The patterns of absorption and reflection of an ultrashort laser pulse by a plasma with a solid-state density, which are realized in the mode of the normal skin effect, are studied. It is shown that a decrease in low-power pulse duration shorter than the period corresponding to the fundamental frequency of radiation leads to an increase in the absorption coefficient. If the pulse power is so high as to provide electron heating during a time shorter than the reciprocal fundamental frequency, nonlinear suppression of absorption takes place and the spectrum of the reflected radiation contains odd harmonics of the fundamental frequency. 相似文献