全文获取类型
收费全文 | 19679篇 |
免费 | 4151篇 |
国内免费 | 956篇 |
专业分类
化学 | 1543篇 |
晶体学 | 61篇 |
力学 | 3078篇 |
综合类 | 159篇 |
数学 | 2591篇 |
物理学 | 8546篇 |
无线电 | 8808篇 |
出版年
2024年 | 75篇 |
2023年 | 246篇 |
2022年 | 409篇 |
2021年 | 518篇 |
2020年 | 631篇 |
2019年 | 515篇 |
2018年 | 533篇 |
2017年 | 661篇 |
2016年 | 750篇 |
2015年 | 755篇 |
2014年 | 1264篇 |
2013年 | 1236篇 |
2012年 | 1308篇 |
2011年 | 1527篇 |
2010年 | 1211篇 |
2009年 | 1181篇 |
2008年 | 1243篇 |
2007年 | 1275篇 |
2006年 | 1197篇 |
2005年 | 1073篇 |
2004年 | 941篇 |
2003年 | 934篇 |
2002年 | 804篇 |
2001年 | 712篇 |
2000年 | 554篇 |
1999年 | 459篇 |
1998年 | 433篇 |
1997年 | 353篇 |
1996年 | 319篇 |
1995年 | 275篇 |
1994年 | 237篇 |
1993年 | 214篇 |
1992年 | 179篇 |
1991年 | 153篇 |
1990年 | 122篇 |
1989年 | 116篇 |
1988年 | 81篇 |
1987年 | 55篇 |
1986年 | 35篇 |
1985年 | 37篇 |
1984年 | 35篇 |
1983年 | 15篇 |
1982年 | 30篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1973年 | 7篇 |
1971年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Zhang Xun Zhang Hongjie Zhang Ping Chen Weibin Luo Xizhang 《International Journal of Infrared and Millimeter Waves》2003,24(11):1967-1976
Based on the basic theory of molecular vibration relaxation and semi-classical density matrix theory, operating parameters optimization of buffer gas in the process of miniature pulsed optically pumped submillimeter wave laser was systemically studied and the theoretical calculated result was tested by experiments. The result would do favor to develop and study high-power and wide-range tunable miniature and high-efficient pulsed optically pumped submillimeter wave laser and also had some instruction to its application. 相似文献
52.
Yang Ju Yo Hirosawa Masumi Saka Hiroyuki Abé 《International Journal of Infrared and Millimeter Waves》2003,24(3):391-397
We developed a compact equipment working at 94 GHz to replace the commonly used network analyzer for nondestructive testing of materials. The compact equipment was designed to measure the variations in the amplitude and phase of the reflected signal from the material relative to a reference signal. A good accuracy of the amplitude and phase measurement of the equipment was obtained in the confirmative experiments. The distribution of a drop of water in a wood plate is clearly visible in the millimeter wave images obtained by the amplitude and phase measurement. 相似文献
53.
研究了 2 0 0 0年 MCM— B题 ,将问题推广到有三层干扰的复杂情况 ,给出并严格证明了 ( k,1,1)问题的最优解 相似文献
54.
一种固定阈值的毫米波图像边缘检测方法 总被引:1,自引:0,他引:1
文章提出了一种固定阈值的毫米波图像边缘检测方法。根据图像的统计特征确定出像素的标准梯度强度,并采用单阈值对图像进行边缘粗定位,然后施行非最大抑制处理和滤波,得到最终检测结果。由于该算法对各幅毫米波图像设置相同的阈值,故能实现自动检测,同时还具有计算量小的特点。实验结果表明该方法进行毫米波图像边缘检测的有效性和可行性。 相似文献
55.
Using the multipoles method, we formulate the problems of radiation (both heave and sway) of water waves by a submerged sphere
in deep as well as in uniform finite depth water with an ice-cover, with the ice-cover being modelled as an elastic plate
of very small thickness. In each case this leads to an infinite system of linear equations which are solved numerically by
standard techniques. The added-mass and damping coefficients for a heaving and swaying sphere are obtained and depicted graphically
against the wave number for various values of the radius of the submerged sphere and flexural rigidity of the ice-cover to
show the effect of the presence of ice-cover on these quantities. When the flexural rigidity is taken to be zero, the numerical
results for the added-mass and damping coefficient for water with a free surface are recovered. 相似文献
56.
CHEN Bao-Zhen HUANG Zu-Qia 《理论物理通讯》2004,42(9)
The theoretical signal-pressure curves are calculated from approximate analytical solutions of the coupledequations describing the third order parametric wave mixing in a gas-filled capillary of femto-second laser pulses. Thecomparison with the corresponding experimental curves suggests that the following three factors exert important influ-ences on the degree of fitting between the theoretical and experimental results: the walk-off, the phase modulation, andthe third order harmonic of idler pulse. 相似文献
57.
58.
研究了在均匀分层介质中构成标准矢量波函数的必要条件。研究结果表明在均匀分层介质中构成标准矢量波函数一般需遵循Morse-Feshbach判据外,领示矢量只能选取与折射率变化方向一致的那根坐标轴单位矢量。但在某些特定的条件下,对领示矢量的选取条件可以放宽为只需遵循Morse-Feshbach判据即可。 相似文献
59.
ON INTERACTION OF SHOCK AND SOUND WAVE (I) 总被引:1,自引:1,他引:0
Chen Shuxing 《数学年刊B辑(英文版)》1996,17(1):35-42
This paper studies the interaction of shock and gradient wave (sound wave) of solutions to the system of inviscid isentropic gas dynamics as a model for the corresponding problems for nonlinear hyperbolic systems. The problem can be reduced to a boundary value problem in a wedged dormain, By using the method of constructing asymptotic solutions and Newton‘siteration process it is proved that if a weak shock hits a gradient wave, then the grandient wave will split into two gradient waves, while the shock continuses propagating. In this paper the author reduces the problem to a standard form and constructs asymptotic solution of the problem. The existence of the genuine solution will he given in the following paper. 相似文献