全文获取类型
收费全文 | 11079篇 |
免费 | 935篇 |
国内免费 | 821篇 |
专业分类
化学 | 2634篇 |
晶体学 | 74篇 |
力学 | 983篇 |
综合类 | 174篇 |
数学 | 5815篇 |
物理学 | 3155篇 |
出版年
2023年 | 91篇 |
2022年 | 154篇 |
2021年 | 182篇 |
2020年 | 265篇 |
2019年 | 274篇 |
2018年 | 259篇 |
2017年 | 271篇 |
2016年 | 335篇 |
2015年 | 216篇 |
2014年 | 486篇 |
2013年 | 707篇 |
2012年 | 483篇 |
2011年 | 599篇 |
2010年 | 504篇 |
2009年 | 618篇 |
2008年 | 736篇 |
2007年 | 649篇 |
2006年 | 638篇 |
2005年 | 564篇 |
2004年 | 441篇 |
2003年 | 450篇 |
2002年 | 463篇 |
2001年 | 358篇 |
2000年 | 335篇 |
1999年 | 297篇 |
1998年 | 290篇 |
1997年 | 244篇 |
1996年 | 204篇 |
1995年 | 123篇 |
1994年 | 132篇 |
1993年 | 120篇 |
1992年 | 108篇 |
1991年 | 79篇 |
1990年 | 89篇 |
1989年 | 54篇 |
1988年 | 73篇 |
1987年 | 54篇 |
1986年 | 42篇 |
1985年 | 104篇 |
1984年 | 126篇 |
1983年 | 55篇 |
1982年 | 103篇 |
1981年 | 116篇 |
1980年 | 62篇 |
1979年 | 60篇 |
1978年 | 61篇 |
1977年 | 43篇 |
1976年 | 31篇 |
1974年 | 19篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Under the non-Lipschitzian condition, a small time large deviation principle of diffusion processes on Hilbert spaces is established. The operator theory and Gronwall inequality play an important role. 相似文献
912.
At present, the methods of constructing vector valued rational interpolation function in rectangular mesh are mainly presented by means of the branched continued fractions. In order to get vector valued rational interpolation function with lower degree and better approximation effect, the paper divides rectangular mesh into pieces by choosing nonnegative integer parameters d1 (0 〈 dl ≤ m) and d2 (0 ≤ d2≤ n), builds bivariate polynomial vector interpolation for each piece, then combines with them properly. As compared with previous methods, the new method given by this paper is easy to compute and the degree for the interpolants is lower. 相似文献
913.
New determinations of the ground-state electric dipole moments of acrylonitrile and propionitrile have been made from Stark effect measurements at conditions of supersonic expansion. The measurements were made on selected Stark lobes of fully resolved hyperfine components of several lowest-J rotational transitions. The results are μa = 3.821(3) D, μb = 0.687(8) D, μtot = 3.882(3) D for acrylonitrile, and μa = 3.816(3) D, μb = 1.235(1) D, μtot = 4.011(3) D for propionitrile. The new value of μb for acrylonitrile is appreciably different from those reported previously and it has been substantiated by both ab initio calculations and relative intensity measurements. The new dipole moment implies a considerable revision in the calculated intensities of the strongest THz-region rotational transitions of acrylonitrile, to 59% of previous values. 相似文献
914.
A high contrast and capacity efficient visual cryptography scheme for the encryption of multiple secret images 总被引:1,自引:0,他引:1
The visual secret sharing for multiple secrets (VSSM) allows for the encryption of a greater number of secret images into a given image area. Previous researches on VSSM schemes incur a very serious pixel expansion that will damage capable of increasing the capacity of secret image encryption. Moreover, the most of VSSM schemes will decrease the contrast of recover images while the amount of secret image encryption increases. These drawbacks limit applicability of the existing VSSM schemes. In this paper, we propose a highly efficient encryption algorithm to cope with this problem. The proposed algorithm adopts a novel hybrid encryption approach that includes a VC-based encryption and a camouflaging process. The experimental results demonstrate that the proposed approach not only can increase the capacity efficient for VSSM schemes, but also maintains an excellent level of contrast in the recovered secret images. 相似文献
915.
We propose a new two-mode squeezed coherent state representation |z1, z2〉g which is characteristic of the correlation between the squeezing and the displacement. Based on it and using the technique of integration within an ordered product of operators we obtain a generalized two-mode Fresnel operator (GTFO), which is an image of the mapping from (z1, z2) to in |z1, z2〉g representation. The matrix element of GTFO in the coordinate representation leads to a generalized two-dimensional Collins formula (Huygens-Fresnel integration transformation describing optical diffraction) in entangled form. 相似文献
916.
We present simple and accurate analytical expressions for transmission coefficient at the splice with angular offset and transverse offset in case of first higher mode propagation in graded index fibers. We employ the simple series expression for first higher order modal field for graded index fiber. The evaluation of the concerned parameters based on our formalism requires very little computations. Here, we show that our estimations match excellently well with the exact results in case of step and parabolic index fibers. Further, splice being highly tolerant for longitudinal separation, our analysis is judiciously restricted to the case of transverse and angular mismatches only. The analysis should find application in dual mode graded index fiber in all optical technology. 相似文献
917.
918.
919.
920.
介绍了基于神光Ⅲ原型装置的成像型任意反射面速度干涉仪(VISAR)的系统结构和实验结果,详细阐述了为解决VISAR系统的光路对接调试、干涉仪零程差状态保持、探针激光方式、条纹相机触发时间等问题而采取的特殊手段。对系统性能进行了测试,结果表明:时间分辨力优于30 ps,空间分辨力优于10 μm,测速范围为10~50 km·s-1。通过神光Ⅲ原型装置进行打靶实验,结果表明:该系统能获得透明材料中冲击波作用形成的清晰干涉条纹,能依据条纹分布情况来判断冲击波在空间不同位置的作用情况。对双灵敏度结构获得的两幅条纹图像进行处理,计算得到了冲击波在透明材料中的传播速度为36.5 km·s-1。 相似文献