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   690191篇
  免费   6055篇
  国内免费   1812篇
化学   342686篇
晶体学   7782篇
力学   35571篇
综合类   21篇
数学   100651篇
物理学   211347篇
  2021年   5391篇
  2020年   6335篇
  2019年   7108篇
  2018年   13565篇
  2017年   13859篇
  2016年   15445篇
  2015年   7751篇
  2014年   12302篇
  2013年   28782篇
  2012年   24175篇
  2011年   32678篇
  2010年   23029篇
  2009年   22956篇
  2008年   30327篇
  2007年   32188篇
  2006年   22984篇
  2005年   23405篇
  2004年   20275篇
  2003年   18649篇
  2002年   16410篇
  2001年   17327篇
  2000年   13406篇
  1999年   9991篇
  1998年   8576篇
  1997年   8640篇
  1996年   8128篇
  1995年   7587篇
  1994年   7593篇
  1993年   7385篇
  1992年   7848篇
  1991年   8368篇
  1990年   8018篇
  1989年   7891篇
  1988年   7742篇
  1987年   7535篇
  1986年   7251篇
  1985年   9375篇
  1984年   9835篇
  1983年   8152篇
  1982年   8634篇
  1981年   8051篇
  1980年   7652篇
  1979年   8249篇
  1978年   8670篇
  1977年   8510篇
  1976年   8461篇
  1975年   8047篇
  1974年   7914篇
  1973年   8327篇
  1972年   5934篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Journal of Applied Spectroscopy - It is shown that the relations for determining a purely electronic transition from diffuse absorption or emission spectra, obtained under the assumption of...  相似文献   
52.
In this article, the effect of ionization on the energy spectrum of electrons within the interaction of a laser pulse with hydrogen atoms is investigated using particle-in-cell simulation codes. The results show that the behaviour of electrons' energy distribution function in the field-ionized plasma, which occurred due to the field ionization, compared with that in the pre-plasma strongly depends on the pulse shape. For short rise-time pulses (here 30 fs), due to the rapid enhancement of laser electric field, ionization occurs quickly, and as a result, there is not much difference in the electron energy in both the media. However, for pulses with rise time of 40 fs, in the pre-plasma state, the electron population reaches higher energies compared with the field-ionized plasma state. The main reason for this difference is the nonlinear wave breaking that happens earlier due to density inhomogeneity in the field-ionized plasma. On the other hand, at longer rise-time pulses (here 60 and 70 fs), electrons achieve higher energies in the field-ionized plasma than those in the case of pre-plasma. In this case, because of density fluctuations in the field-ionized plasma, the Raman backscattered radiations are seeded by a strong initial noise at the earlier times and the Mendonca condition for chaos threshold is met sooner. Therefore, the electrons gain more energy through the stochastic mechanism that is in agreement with chaotic nature of the motion.  相似文献   
53.
Garmanova  T. A. 《Mathematical Notes》2021,109(3-4):527-533
Mathematical Notes - The paper deals with sharp estimates of derivatives of intermediate order $$k\le n-1$$ in the Sobolev space $$\mathring W^n_2[0;1]$$ , $$n\in\mathbb N$$ . The functions...  相似文献   
54.
Journal of Applied Mechanics and Technical Physics - This paper describes a problem of steady-state creep of a long narrow rectangular membrane in the case of a linear dependence between the...  相似文献   
55.
Journal of Experimental and Theoretical Physics - The structural (lattice metric) and elastic characteristics of ErBaCo4O7 + x cobaltites, which are subjected to different heat treatment and are...  相似文献   
56.
Melnikov  A.  Aksentyev  A.  Senichev  Y. 《Physics of Atomic Nuclei》2021,84(11):1871-1873
Physics of Atomic Nuclei - We have investigated the robustness of the spin-navigator based method for manipulating the beam polarization to bend magnet installation errors. Toward that end,...  相似文献   
57.
Physics of the Solid State - The interference of excited and received by current antennae magnetoelastic waves counterpropagating in an yttrium iron garnet film is experimentally studied. It is...  相似文献   
58.
Journal of Applied Spectroscopy - With the COVID-19 outbreak, many challenges are posed before the scientific world to curb this pandemic. The diagnostic testing, treatment, and vaccine development...  相似文献   
59.
Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The...  相似文献   
60.
Çiftçi  C.  Aytaç  A. 《Mathematical Notes》2021,109(3-4):517-526
Mathematical Notes - The vulnerability in a communication network is the measurement of the strength of the network against damage that occurs in nodes or communication links. It is important that...  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