首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   33420篇
  免费   4531篇
  国内免费   3271篇
化学   23182篇
晶体学   329篇
力学   2088篇
综合类   346篇
数学   3634篇
物理学   11643篇
  2024年   117篇
  2023年   644篇
  2022年   1033篇
  2021年   1111篇
  2020年   1243篇
  2019年   1242篇
  2018年   1024篇
  2017年   944篇
  2016年   1447篇
  2015年   1427篇
  2014年   1740篇
  2013年   2264篇
  2012年   2905篇
  2011年   2956篇
  2010年   1864篇
  2009年   1832篇
  2008年   1971篇
  2007年   1876篇
  2006年   1672篇
  2005年   1394篇
  2004年   1093篇
  2003年   901篇
  2002年   885篇
  2001年   676篇
  2000年   639篇
  1999年   710篇
  1998年   614篇
  1997年   603篇
  1996年   696篇
  1995年   547篇
  1994年   493篇
  1993年   404篇
  1992年   383篇
  1991年   345篇
  1990年   268篇
  1989年   218篇
  1988年   164篇
  1987年   144篇
  1986年   134篇
  1985年   125篇
  1984年   88篇
  1983年   67篇
  1982年   42篇
  1981年   37篇
  1980年   19篇
  1978年   19篇
  1977年   24篇
  1976年   20篇
  1975年   31篇
  1974年   27篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
All-optical wavelength conversion of 10-Gb/s signal based on four-wave mixing is experimentally demonstrated in a 30-m-long dispersion-flattened microstructure fiber with small positive dispersion. For an average pump power of 26 dBm, the conversion efficiency was around -19.5 dB with the fluctuation less than ±1.4 dB, covering a conversion bandwidth of 20 nm. The eye diagram of the converted signal shows good eye opening.  相似文献   
62.
The transmission properties of elastic waves propagating in a three-dimensional composite structure embedded periodically with spherical inclusions are analyzed by the transfer matrix method in this paper. Firstly, the periodic composite structures are divided into many layers, the transfer matrix of monolayer structure is deduced by the wave equations, and the transfer matrix of the entire structure is obtained in the case of boundary conditions of displacement and stress continuity between layers. Then, the effective impedance of the structure is analyzed to calculate its reflectivity and transmissivity of vibration isolation. Finally, numerical simulation is carried out; the experiment results validate the accuracy and feasibility of the method adopted in the paper and some useful conclusions are obtained. Project (No. 50075029) supported by the National Natural Science Foundation of China.  相似文献   
63.
本文通过“1 4-1 5”智力玩具和最优戴断切割问题两个实例 ,讨论了逆序数在解决实际问题中的应用  相似文献   
64.
In this paper, we generalize Hu Ke's sharpness of Hölder's inequality. As application, the obtained result is used to improve the well-known Opial-Olech inequality.  相似文献   
65.
Highly ordered composite nanowires with multilayer Ni/Cu and NiFe/Cu have been fabricated by pulsed electrodeposition into nanoporous alumina membrane. The diameter of wires can be easily varied by pore size of alumina, ranging from 30 to 100 nm. The applied potential and the duration of each potential square pulse determine the thickness of the metal layers. The nanowires have been characterized by transmission electron microscopy (TEM), magnetic force microscopy (MFM), and vibrating sample magnetometer (VSM) measurements. The MFM images indicate that every ferromagnetic layer separated by Cu layer was present as single isolated domain-like magnet. This technique has potential use in the measurement and application of magnetic nanodevices.  相似文献   
66.
67.
68.
This paper considers a two-echelon capacitated supply chain with two non-identical retailers and information sharing. We characterize the optimal inventory policies. We also study the benefits of the optimal stock rationing policy over the first come first served (FCFS) and the modified echelon-stock rationing (MESR) policies.  相似文献   
69.
70.
Weak vector equilibrium problems with bi-variable mappings from product space of two bounded complete locally convex Hausdorff topological vector spaces to another topological vector space are studied. The existence theorems of solutions are proved by the FKKM fixed point theorem. Viscosity principle of vector equilibrium problems is dealt with. The relations between solutions of the vector equilibrium problem and those of its perturbation problem are presented.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号