全文获取类型
收费全文 | 212258篇 |
免费 | 3377篇 |
国内免费 | 1738篇 |
专业分类
化学 | 108597篇 |
晶体学 | 3315篇 |
力学 | 9854篇 |
综合类 | 86篇 |
数学 | 23424篇 |
物理学 | 72097篇 |
出版年
2021年 | 1933篇 |
2020年 | 2115篇 |
2019年 | 2307篇 |
2018年 | 2929篇 |
2017年 | 2824篇 |
2016年 | 4149篇 |
2015年 | 2644篇 |
2014年 | 4128篇 |
2013年 | 9689篇 |
2012年 | 7973篇 |
2011年 | 9529篇 |
2010年 | 6587篇 |
2009年 | 6439篇 |
2008年 | 8531篇 |
2007年 | 8596篇 |
2006年 | 8167篇 |
2005年 | 7355篇 |
2004年 | 6760篇 |
2003年 | 5964篇 |
2002年 | 5824篇 |
2001年 | 6705篇 |
2000年 | 5165篇 |
1999年 | 4000篇 |
1998年 | 3224篇 |
1997年 | 3203篇 |
1996年 | 2951篇 |
1995年 | 2737篇 |
1994年 | 2606篇 |
1993年 | 2436篇 |
1992年 | 2806篇 |
1991年 | 2767篇 |
1990年 | 2673篇 |
1989年 | 2471篇 |
1988年 | 2491篇 |
1987年 | 2474篇 |
1986年 | 2314篇 |
1985年 | 2986篇 |
1984年 | 3231篇 |
1983年 | 2648篇 |
1982年 | 2814篇 |
1981年 | 2779篇 |
1980年 | 2645篇 |
1979年 | 2698篇 |
1978年 | 2795篇 |
1977年 | 2810篇 |
1976年 | 2867篇 |
1975年 | 2653篇 |
1974年 | 2633篇 |
1973年 | 2758篇 |
1972年 | 1744篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Chao Liu Liying Wang Lin Yang Famei Wang Chunhong Xu Jingwei Lv Guanglai Fu Xianli Li Qiang Liu Haiwei Mu Tao Sun Paul K. Chu 《Physics letters. A》2019,383(25):3200-3206
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (), the diameter of inner air holes (), the metal film thickness (t), as well as the liquid refractive index (n). 相似文献
72.
Martín D. Safe 《Journal of Graph Theory》2020,93(2):268-298
A graph is concave-round if its vertices can be circularly enumerated so that the closed neighborhood of each vertex is an interval in the enumeration. In this study, we give a minimal forbidden induced subgraph characterization for the class of concave-round graphs, solving a problem posed by Bang-Jensen, Huang, and Yeo [SIAM J. Discrete Math., 13 (2000), pp. 179–193]. In addition, we show that it is possible to find one such forbidden induced subgraph in linear time in any given graph that is not concave-round. As part of the analysis, we obtain characterizations by minimal forbidden submatrices for the circular-ones property for rows and for the circular-ones property for rows and columns and show that, also for both variants of the property, one of the corresponding forbidden submatrices can be found (if present) in any given matrix in linear time. We make some final remarks regarding connections to some classes of circular-arc graphs. 相似文献
73.
JETP Letters - The leading role of the bremsstrahlung at resonant Compton scattering of a hard X-ray photon by a multielectron atom has been theoretically predicted. This result can be important in... 相似文献
74.
International Applied Mechanics - Problems of parametric optimization of rod structure stated in terms of the nonlinear programming problem are considered. Use is made of the method of projection... 相似文献
75.
76.
77.
78.
79.
E. A. Andrianova V. D. Davidenko V. F. Tsibulskiy S. V. Tsibulskiy 《Physics of Atomic Nuclei》2015,78(11):1252-1258
Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed. 相似文献
80.