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   27437篇
  免费   4579篇
  国内免费   3819篇
化学   20714篇
晶体学   330篇
力学   1498篇
综合类   211篇
数学   2986篇
物理学   10096篇
  2024年   89篇
  2023年   491篇
  2022年   908篇
  2021年   974篇
  2020年   989篇
  2019年   1101篇
  2018年   939篇
  2017年   902篇
  2016年   1289篇
  2015年   1365篇
  2014年   1619篇
  2013年   2038篇
  2012年   2495篇
  2011年   2372篇
  2010年   1712篇
  2009年   1654篇
  2008年   1851篇
  2007年   1685篇
  2006年   1532篇
  2005年   1417篇
  2004年   1114篇
  2003年   883篇
  2002年   939篇
  2001年   744篇
  2000年   620篇
  1999年   598篇
  1998年   501篇
  1997年   456篇
  1996年   412篇
  1995年   345篇
  1994年   305篇
  1993年   252篇
  1992年   206篇
  1991年   182篇
  1990年   204篇
  1989年   137篇
  1988年   110篇
  1987年   70篇
  1986年   77篇
  1985年   73篇
  1984年   36篇
  1983年   37篇
  1982年   34篇
  1981年   22篇
  1980年   12篇
  1979年   4篇
  1977年   6篇
  1936年   7篇
  1930年   2篇
  1916年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
931.
The problem of robust decentralized adaptive synchronization of general complex networks with coupling delayed and uncertainties is investigated in this article. It is only assumed that the upper normal bound of uncertain inner and outer coupling matrices is positive but its concrete structure is not also required to be known. The time‐varying coupling delay is a any nonnegative continuous and bounded function and not require its derivative to be less than one, that is, general time‐varying coupling delays and uncertainties. For such a class of uncertain complex networks, a new synchronization scheme is presented by a class of continuous memoryless robust decentralized adaptive synchronization controllers. It is also shown that the synchronization error dynamics of uncertain complex networks can be guaranteed as uniformly exponentially convergent toward a ball that can be as small as desired. Finally, numerical simulations are provided to demonstrate the effectiveness and robustness of proposed complex networks synchronization schemes. © 2013 Wiley Periodicals, Inc. Complexity 19: 10–26, 2014  相似文献   
932.
This paper is devoted to the high-dimensional and multilinear Hausdorff operators on the Heisenberg group H n. The sharp bounds for the strong type(p, p)(1 ≤ p ≤∞) estimates of n-dimensional Hausdorff operators on H n are obtained. The sharp bounds for strong(p, p) estimates are further extended to multilinear cases. As an application, we derive the sharp constant for the multilinear Hardy operator on H n. The weak type(p, p)(1 ≤ p ≤∞) estimates are also obtained.  相似文献   
933.
在激光等离子体机理的研究中,为实现灵活的界面配置和多路脉冲激光器高精度的时序延时,设计了一种基于微控制器STM32和FPGA的多路时序延时控制系统。重点介绍了基于FPGA的多路ns级时序信号和基于ucGUI的触摸屏界面的设计。另外,采用高速光电隔离技术和高速FET开关电路技术,对驱动电路进行了设计,缩短了输出脉冲上升沿的时间,提高了系统延时精度、驱动能力和抗干扰性能。测试结果表明,该设计每路延时可调,调节范围为5 ns~10 ms,最小可调步进为5 ns,延时误差小于1 ns。  相似文献   
934.
We theoretically present the results for a scanning tunneling transport between a metallic tip and a Kondo lattice.We calculate the density of states(DOS)and the tunneling current and differential conductance(DC)under different conduction-fermion band hybridization and temperature in the Kondo lattice.It is found that the hybridization strength and temperature give asymmetric coherent peaks in the DOS separated by the Fermi energy.The corresponding current and DC intensity depend on the temperature and quantum interference effect among the c-electron and f-electron states in the Kondo lattice.  相似文献   
935.
Magnetic alloy(MA)-loaded cavities have been widely used in compact proton and heavy-ion synchrotrons,and the MA core is the key issue in their development.Chinese-produced MA has never yet been adopted as core material for an MA-loaded cavity.To use Chinese-produced MA as the core material,it is necessary to study its properties,and compare with MA material produced elsewhere.In this paper,the properties of several MA cores made of Chinese-produced material are measured.Based on the measured results,a schematic design is produced for a cavity which could obtain 1 kV gap voltage with less than 1.5 kW power dissipation in the frequency range of0.5-7 MHz.The difference between resonant frequencies obtained from simulation and analytical results is less than10%.  相似文献   
936.
Beam-based BPM offset calibration was carried out for Injector II at the C-ADS demonstration facility at the Institute of Modern Physics(IMP), Chinese Academy of Science(CAS). By using the steering coils integrated in the quadrupoles, the beam orbit can be effectively adjusted and BPM positions recorded at the Medium Energy Beam Transport of the Injector II Linac. The studies were done with a 2 m A, 2.1 Me V proton beam in pulsed mode.During the studies, the "null comparison method" was applied for the calibration. This method is less sensitive to errors compared with the traditional transmission matrix method. In addition, the quadrupole magnet's center can also be calibrated with this method.  相似文献   
937.
何宴辉  汪理虎  刘涛 《应用声学》2016,24(7):268-271
LVDT模拟器在航空发动机的测试系统中有着广泛的应用,针对传统模拟器中由于引入变压器导致精度低的缺点,从LVDT传感器原理出发,设计了一种幅频自校准方法,利用乘法型DAC芯片实现了电路合成模拟LVDT传感器的目的并克服了变压器的幅频响应,提高了LVDT模拟器在宽频率范围的仿真精度。该模拟器已成功应用于某型号发动控制系统的地面仿真测试系统中,达到了预期效果。  相似文献   
938.
研究了一种新的利用含氧化合物制备纯氢的催化变换过程,该过程耦合了含氧化合物的催化重整、水煤气变换反应和CO2去除步骤. 详细研究了重整催化剂的筛选、反应条件以及不同的含氧化合物催化重整行为. 利用所述集成方法获得的最高氢气浓度为99.96vol%和最大转化率为97.1mol%. 此外,通过含氧化合物的解离、催化重整和水煤气变换反应研究,探讨了含氧化合物制备纯氢的相关反应路径.  相似文献   
939.
随着软件功能实现技术越来越复杂,软件测试领域迫切需要具有自动化、多平台、开销小的自动化测试框架,STAF的出现很好地解决了这个问题。提出一种基于STAF的自动化测试框架,并进行模拟实践,采用ATT工具设计自动测试引擎,通过模拟实验测试,构建基于STAF的自动化测试框架。测试结果显示:在不同环境下,该框架均具有软件测试自动化程度高、测试效率高,易于管理、维护和可扩展等优点。  相似文献   
940.
For a graph G and two positive integers j and k, an m-L(j, k)-edge-labeling of G is an assignment on the edges to the set {0, 1, 2,..., m}, such that adjacent edges which receive labels differ at least by j, and edges which are distance two apart receive labels differ at least by kThe λ j,k-number of G is the minimum m such that an m-L(j, k)-edge-labeling is admitted by GIn this article, the L(1, 2)-edge-labeling for the hexagonal lattice, the square lattice and the triangular lattice are studied, and the bounds for λ j,k-numbers of these graphs are obtained.  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