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   103797篇
  免费   1360篇
  国内免费   542篇
化学   41597篇
晶体学   1056篇
力学   7444篇
综合类   1篇
数学   34181篇
物理学   21420篇
  2023年   145篇
  2022年   274篇
  2021年   625篇
  2020年   484篇
  2019年   517篇
  2018年   10738篇
  2017年   10532篇
  2016年   6774篇
  2015年   1509篇
  2014年   1220篇
  2013年   1909篇
  2012年   5638篇
  2011年   12488篇
  2010年   6937篇
  2009年   7149篇
  2008年   8325篇
  2007年   10237篇
  2006年   1838篇
  2005年   2671篇
  2004年   2731篇
  2003年   2990篇
  2002年   1978篇
  2001年   862篇
  2000年   842篇
  1999年   528篇
  1998年   425篇
  1997年   384篇
  1996年   514篇
  1995年   336篇
  1994年   304篇
  1993年   343篇
  1992年   245篇
  1991年   219篇
  1990年   205篇
  1989年   188篇
  1988年   152篇
  1987年   151篇
  1986年   136篇
  1985年   146篇
  1984年   110篇
  1983年   93篇
  1982年   120篇
  1981年   124篇
  1980年   93篇
  1979年   108篇
  1978年   90篇
  1977年   70篇
  1976年   76篇
  1974年   66篇
  1973年   70篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
Baik  Hyungryul  Kim  Changsub  Kwak  Sanghoon  Shin  Hyunshik 《Geometriae Dedicata》2021,214(1):399-426
Geometriae Dedicata - We show that an Anosov map has a geodesic axis on the curve graph of the torus. The direct corollary of our result is the stable translation length of an Anosov map on the...  相似文献   
33.
34.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
35.
36.
A theory is developed for the density profile of low temperature plasmas confined by applied magnetic field and an experiment of the electron-cyclotron-resonance (ECR) plasma is conducted to compare the theoretical prediction and experimental measurements. Due to a large electron mobility along the magnetic field, electrons move quickly out of the system, leaving ions behind and building a space charge potential, which leads to the ambipolar diffusion of ions. In a steady-state condition, the plasma generation by ionization of neutral molecules is in balance with plasma loss due to the diffusion, leading to the electron temperature equation, which is expressed in terms of the plasma size, chamber pressure, and the ionization energy and cross section of neutrals. The power balance condition leads to the plasma density equation, which is also expressed in terms of the electron temperature, the input microwave power and the chamber pressure. It is shown that the plasma density increases, reaches its peak and decreases, as the chamber pressure increases from a small value (0.1 mTorr). These simple expressions of electron temperature and density provide a scaling law of ECR plasma in terms of system parameters. After carrying out an experimental observation, it is concluded that the theoretical predictions of the electron temperature and plasma density agree remarkably well with experimental data  相似文献   
37.
38.
39.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective.  相似文献   
40.
This paper describes three case studies which investigated issues relating to the implementation and management of advanced information technology. The benefits derived from information technology were found to vary from one organization to another. These studies provide further evidence to support earlier research findings that senior management has an important role to play in the effective exploitation of information technology, and that the investment approach taken by an organization has a significant effect on the development of computer-based information systems. The effectiveness of a system depends not only on applying the appropriate technology, but also on how successfully technical and behavioural issues are resolved.  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