全文获取类型
收费全文 | 24340篇 |
免费 | 4169篇 |
国内免费 | 3545篇 |
专业分类
化学 | 18028篇 |
晶体学 | 274篇 |
力学 | 1411篇 |
综合类 | 248篇 |
数学 | 3370篇 |
物理学 | 8723篇 |
出版年
2024年 | 68篇 |
2023年 | 537篇 |
2022年 | 555篇 |
2021年 | 808篇 |
2020年 | 1103篇 |
2019年 | 1014篇 |
2018年 | 867篇 |
2017年 | 859篇 |
2016年 | 1260篇 |
2015年 | 1194篇 |
2014年 | 1390篇 |
2013年 | 1873篇 |
2012年 | 2145篇 |
2011年 | 2275篇 |
2010年 | 1575篇 |
2009年 | 1477篇 |
2008年 | 1636篇 |
2007年 | 1409篇 |
2006年 | 1275篇 |
2005年 | 1151篇 |
2004年 | 912篇 |
2003年 | 834篇 |
2002年 | 945篇 |
2001年 | 761篇 |
2000年 | 586篇 |
1999年 | 559篇 |
1998年 | 401篇 |
1997年 | 350篇 |
1996年 | 381篇 |
1995年 | 346篇 |
1994年 | 285篇 |
1993年 | 207篇 |
1992年 | 187篇 |
1991年 | 174篇 |
1990年 | 141篇 |
1989年 | 108篇 |
1988年 | 62篇 |
1987年 | 71篇 |
1986年 | 90篇 |
1985年 | 51篇 |
1984年 | 36篇 |
1983年 | 33篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1975年 | 3篇 |
1959年 | 4篇 |
1957年 | 9篇 |
1936年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
121.
现代免疫分析技术研究进展 总被引:1,自引:0,他引:1
本文着重分析了各种标记免疫分析方法的发展状况,指出更多的非同位素标记物的使用,自动化分析等将是免疫分析法的未来发展趋势。 相似文献
122.
Qingrong Zheng Gang Su Jian Wang Hong Guo 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):233-238
We report a theoretical analysis of the phonon thermal conductance, κ(T), for single wall carbon nanotubes (SWCN). In a range of low temperatues up to 100 K, κ(T) of perfect SWCN is found to increase with temperature, approximately, in a parabolic fashion. This is qualitatively consistent
with recent experimental measurements where the tube-tube interactions are negligibly weak. When the carbon-carbon bond length
is slightly varied, κ(T) is found to be qualitatively unaltered which implies that the anharmonic effect does not change the qualitative behavior
of κ(T).
Received 12 June 2001 相似文献
123.
关于《一类奇异边值问题的正解》的注记 总被引:3,自引:0,他引:3
文[4]通过构造反例断言文[1]中定理的必要性证明有误,本文首先指出文[4] 的这个断言不正确,然后对文[4]中定理2.1作了本质性的改进. 相似文献
124.
给出目标信息系统学习的多准则决策方法,建立多准则决策的规则学习模型,讨论该模型的性质。该模型优于Z.Pawlak方法,将规则提取与信息融合为一体。也优于AHP等模型,具有简洁性.通过实例计算,取得了满意结果。 相似文献
125.
A subgroup H of a finite group G is said to have the semi cover-avoiding property in G if there is a normal series of G such that H covers or avoids every normal factor of the series. In this paper, some new results are obtained based on the assumption that some subgroups have the semi cover-avoiding property in the group. 相似文献
126.
By introducing an imaginary space transform curvature ρs, a complex space called Riemannian space is constructed, in which the light propagating in free space has the trajectory
of straight line while propagating. Moreover, this curvature couples with that of the wave front of the paraxial beam ρw, and therefore a complex curvature ρc is constructed, which can be employed to investigate the behavior of the light transmission and to generalize the ABCD law.
Project supported by the National Hi-Tech Inertial Confinement Fusion Committee, the Guangdong Natural Science Foundation
the Postdoctoral Foundation of Guangdong and National Postdoctoral Foundation of China. 相似文献
127.
R. P. Spielmann Jin Zhen H. J. Triebel V. Nicolas M. Heller E. Bü cheler 《Magnetic resonance imaging》1992,10(6):893-901
To correlate the appearance of poststenotic jets on gradient echo images with features of localized Doppler spectra of the jets, we studied an in vitro model of steady flow-through stenoses of 86, 96, and 99% area reduction. As fluids, water and a 40% glycerol solution in water were used. MRI was performed with a 1.5 T whole body imager and gradient echo images were obtained in planes parallel to the direction of flow. Doppler spectra were acquired separately from the MR measurements at 1 cm intervals for a distance of 10 cm downstream from the stenosis. Poststenotic signal void was observed for water and for the 40% glycerol solution only if the mean velocity within the stenosis exceeded a limit of 50–60 cm/sec. On the MR images, the jets could be divided into two segments: A proximal jet segment of uniform width equal to the diameter of the stenosis, followed by a distal jet segment which was characterized by broadening and then dissipating signal void. Except for the 99% stenosis, a high signal intensity core was present within the proximal jet segment. In the proximal jet segment, the Doppler measurements showed a low temporal fluctuation of the maximal flow velocity and only little flow opposite to the main flow direction. In the distal jet segment, the velocity fluctuation and the intensity of reverse flow increased sharply. The high signal intensity core of the jet was associated with a poststenotic zone of constant maximal flow velocity. The results demonstrate a close relationship between characteristic features of poststenotic jets in MRI and pulsed Doppler sonography. 相似文献
128.
129.
130.
稳态锁模产生4ps激光脉冲 总被引:1,自引:0,他引:1
首次利用GaAs光电导开关,控制Nd:YLF激光器腔内Q值,实现稳态锁模,获得脉宽和能量稳定性极高的4ps激光脉冲。 相似文献