全文获取类型
收费全文 | 4584篇 |
免费 | 1003篇 |
国内免费 | 1859篇 |
专业分类
化学 | 3427篇 |
晶体学 | 241篇 |
力学 | 415篇 |
综合类 | 162篇 |
数学 | 588篇 |
物理学 | 2613篇 |
出版年
2024年 | 15篇 |
2023年 | 44篇 |
2022年 | 154篇 |
2021年 | 158篇 |
2020年 | 176篇 |
2019年 | 169篇 |
2018年 | 173篇 |
2017年 | 229篇 |
2016年 | 184篇 |
2015年 | 242篇 |
2014年 | 290篇 |
2013年 | 385篇 |
2012年 | 397篇 |
2011年 | 408篇 |
2010年 | 434篇 |
2009年 | 492篇 |
2008年 | 461篇 |
2007年 | 459篇 |
2006年 | 393篇 |
2005年 | 346篇 |
2004年 | 270篇 |
2003年 | 232篇 |
2002年 | 184篇 |
2001年 | 208篇 |
2000年 | 239篇 |
1999年 | 150篇 |
1998年 | 56篇 |
1997年 | 44篇 |
1996年 | 59篇 |
1995年 | 39篇 |
1994年 | 43篇 |
1993年 | 41篇 |
1992年 | 38篇 |
1991年 | 25篇 |
1990年 | 35篇 |
1989年 | 32篇 |
1988年 | 24篇 |
1987年 | 27篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有7446条查询结果,搜索用时 0 毫秒
941.
942.
944.
A realistic finite grand unified model has to accommodate at least three generations of ordinary fermions. When this criterion is imposed, we found that only few models of SU(N), SO(2N), SO (2N+1) and exceptional groups can survive as candidates for possible realistic finite supersymmetric grand unified models. All possible solutions are obtianed, but the SU(5) model is excluded. 相似文献
945.
946.
947.
948.
949.
MODELING AND SCALING OF CHIELECTRIC RELAXATION OF NONLINEAR OPTICAL POLYMERS IN FREQUENCY DOMAIN 下载免费PDF全文
chielectric relaxation theory was demonstrated, chielectric relaxation that selectively probes chromophore reorientation in the frequency domain was described by the Havriliak Negami(HN) function, chielectric spectra of several nonlinear optical (NLO) polymers were fitted well by the HN function. To describe the scaling of chromophore reorientation relaxation in frequency domain, two-shape parameters m and n describing the low- and high- frequency wings of the chielectric spectra need to be specified, besides the chielectric characteristic relaxation time τ and the chielectric strength Δχ(2). From the temperature dependences of m and n of NLO polymers, the relations between the chromophore relaxation and the a relaxation of the polymer host have been revealed. 相似文献
950.
TOMOGRAPHY FORMULA FOR BIOCHEMICAL IMAGING OF THIN TISSUE WITH DIFFUSE-PHOTON DENSITY WAVES 下载免费PDF全文
Using the transport theory to describe the near infrared light propagating in tissue with finite parallel-plane geometry, and taking the zero-boundary condition, we obtain the analytical expression of average photon density and Green's function incorporating the boundary effects in the homogeneous tissure. Making use of perturbation theory we also obtain the analytical expression of scattered wave induced by the heterogeneity, and present the 2-dimensional spatial transform of scattered wave with respect to transverse coordinate. If the information of heterogeneity on depth and thickness is available, diffraction tomography formula is presented to save the time of image reconstruction; if the information is unknown, we suggest to obtain the inhomogeneous function from the one-dimensional integral equation of 2-dimensional spatial transform of scattered wave applying the direct matrix method or iterative method for image reconstruction. This approach avoids directly solving three-dimensional integral equation of scattered wave. In our proposed approach the strong points of the direct matrix method, iterative method, and diffraction tomography are fully combined. 相似文献