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   377945篇
  免费   3849篇
  国内免费   1131篇
化学   164537篇
晶体学   5375篇
力学   15539篇
综合类   7篇
数学   38480篇
物理学   109744篇
无线电   49243篇
  2021年   3496篇
  2020年   3777篇
  2019年   4243篇
  2018年   5721篇
  2017年   5872篇
  2016年   8070篇
  2015年   4376篇
  2014年   7658篇
  2013年   17092篇
  2012年   13092篇
  2011年   15668篇
  2010年   11963篇
  2009年   12445篇
  2008年   15117篇
  2007年   15630篇
  2006年   14513篇
  2005年   12765篇
  2004年   11910篇
  2003年   10699篇
  2002年   10598篇
  2001年   12300篇
  2000年   9550篇
  1999年   7636篇
  1998年   6599篇
  1997年   6404篇
  1996年   5924篇
  1995年   5220篇
  1994年   5140篇
  1993年   4981篇
  1992年   5409篇
  1991年   5514篇
  1990年   5232篇
  1989年   4961篇
  1988年   4638篇
  1987年   4425篇
  1986年   4113篇
  1985年   5143篇
  1984年   5181篇
  1983年   4312篇
  1982年   4317篇
  1981年   4019篇
  1980年   3908篇
  1979年   4157篇
  1978年   4126篇
  1977年   4118篇
  1976年   4064篇
  1975年   3881篇
  1974年   3779篇
  1973年   3817篇
  1972年   2731篇
排序方式: 共有10000条查询结果,搜索用时 755 毫秒
61.
Crystallography Reports - Some questions related to the establishment, development, and prospects of physical studies using inelastic thermal-neutron scattering are briefly reviewed. The directions...  相似文献   
62.
Crystallography Reports - The specific features of the formation of crystallites in gallium arsenide crystals grown by the Czochralski method have been investigated. The crystallites are found to...  相似文献   
63.
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.  相似文献   
64.
65.
Russian Physics Journal - The paper shows that the values of zero-point energy and vibrations of atoms in a crystal determined by the uncertainty principle, depend on the dynamic response of atoms....  相似文献   
66.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
67.
68.
69.
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity).  相似文献   
70.
Journal of Communications Technology and Electronics - Abstract—The article presents a rigorous numerical solution, using the Wiener–Hopf method, to the problem of plane wave...  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