全文获取类型
收费全文 | 1499篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 61篇 |
晶体学 | 1篇 |
力学 | 14篇 |
综合类 | 3篇 |
数学 | 709篇 |
物理学 | 272篇 |
无线电 | 458篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 5篇 |
2015年 | 15篇 |
2014年 | 22篇 |
2013年 | 18篇 |
2012年 | 64篇 |
2011年 | 220篇 |
2010年 | 215篇 |
2009年 | 229篇 |
2008年 | 203篇 |
2007年 | 159篇 |
2006年 | 126篇 |
2005年 | 72篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 27篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
排序方式: 共有1518条查询结果,搜索用时 265 毫秒
41.
Xu Xiaoyong Zheng Guoguang Wang Qing-an 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,92(1):61-72
This paper experimentally and theoretically examines the scattering properties of simulated non-spherical hydrometeors including water oblates, ice oblates and ice sphere-cone-oblates, in terms of the backscattering cross-section and the differential reflectivity. The experimental measurements of the backscattering cross-sections of non-spherical hydrometeor samples were performed in the Electromagnetic Scattering Laboratory of China National Space Industrial Corporation. Meanwhile, the backscattering cross-sections have been computed with the transition (T) matrix method. The theoretical results are compared with the experimental data, showing that the calculations are consistent with the observations in general. Experimental and theoretical analyses indicate that the backscattering cross-section of non-spherical particles increases as the particle size parameter increases, and fluctuates when the sizes are larger under the effect of resonance scattering. Differential reflectivity ZDR of water oblates in natural rainfall is always greater than 0 dB whereas ZDR of hailstones may be negative. There is a good linear relationship between differential reflectivity and aspect ratio of a particle. These derivations agree with the literature and can be used to identify the presence of hail particles and distinguish between plate-type and columnar-type hydrometeors. In this study, the measuring experiment and the T-matrix method calculations for the scattering of simulated raindrop and ice particles are also briefly described. 相似文献
42.
Karen Yagdjian 《Journal of Differential Equations》2004,206(1):227-252
Barros-Neto and Gelfand (Duke Math. J. 98 (3) (1999) 465; Duke Math. J. 117 (2) (2003) 561) constructed for the Tricomi operator on the plane the fundamental solutions with the supports in the regions related to the geometry of the characteristics of the Tricomi operator. We give for the Tricomi-type operator a fundamental solution relative to an arbitrary point of Rn+1 with the support in the region t?0, where the operator is hyperbolic. Our key observation is that the fundamental solution for the Tricomi-type operator can be written like an integral of the distributions generated by the fundamental solution of the Cauchy problem for the wave equation. The application of that fundamental solution to the Lp-Lq estimate for the forced Tricomi-type equation is given as well. 相似文献
43.
Ákos Császár 《Journal of Mathematical Analysis and Applications》2004,297(2):490-494
The paper presents a formula for the γ-interior of a set under special conditions for , more general than those in the previous paper [Acta Math. Hungar. 80 (1998) 89-93]. There are also some applications. 相似文献
44.
We develop a notion of an n-fold monoidal category and show that it corresponds in a precise way to the notion of an n-fold loop space. Specifically, the group completion of the nerve of such a category is an n-fold loop space, and free n-fold monoidal categories give rise to a finite simplicial operad of the same homotopy type as the classical little cubes operad used to parametrize the higher H-space structure of an n-fold loop space. We also show directly that this operad has the same homotopy type as the n-th Smith filtration of the Barratt-Eccles operad and the n-th filtration of Berger's complete graph operad. Moreover, this operad contains an equivalent preoperad which gives rise to Milgram's small model for when n=2 and is very closely related to Milgram's model of for n>2. 相似文献
45.
Guoen Hu 《Journal of Mathematical Analysis and Applications》2003,283(2):351-361
boundedness is considered for the commutator of higher-dimensional Marcinkiewicz integral. Some conditions implying the and the boundedness for the commutator of the Marcinkiewicz integral are obtained. 相似文献
46.
47.
随着互联网的进一步发展,调动互联网用户之间的互动类业务已经成为互联网业务新的发展趋势,以网民之间的协作和互动为显著特征的Web 2.0类业务正在蓬勃发展。在众多Web 2.0类业务中,Second Life所引领的虚拟世界类应用不论是其注册用户数以及商业模式创新方面都取得了巨大的成功。通过介绍Second Life的产生和发展,分析Second Life的业务特点以及商业模式,并结合国内虚拟世界的发展情况分析了虚拟世界类应用在中国的发展前景。 相似文献
48.
文章参考NGOSS体系结构,针对Web2.0增值业务的特点,设计了Web2.0增值业务安全运营支撑系统的功能框架。同时,论文还提出了基于RBAC的工作流技术,来实现具体的运营过程并对用户进行权限控制以保障系统的安全。 相似文献
49.
50.
介绍了IXIA公司4~7层工具IxLoad实现的WAP网关测试功能,该功能可以很好地帮助设备制造商验证设备的容量,帮助运营商模拟真实用户模型下的多业务流量,确保网络的升级和扩容能够满足业务发展的需求,这个测试功能和模型是IXIA公司长期与主流设备制造商以及运营商共同合作的结果,具有较强的参考和实用价值。 相似文献