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   2661篇
  免费   935篇
  国内免费   247篇
化学   914篇
晶体学   61篇
力学   171篇
综合类   68篇
数学   155篇
物理学   2474篇
  2024年   3篇
  2023年   15篇
  2022年   59篇
  2021年   65篇
  2020年   99篇
  2019年   58篇
  2018年   68篇
  2017年   125篇
  2016年   130篇
  2015年   108篇
  2014年   176篇
  2013年   212篇
  2012年   238篇
  2011年   226篇
  2010年   218篇
  2009年   207篇
  2008年   205篇
  2007年   190篇
  2006年   188篇
  2005年   176篇
  2004年   162篇
  2003年   119篇
  2002年   98篇
  2001年   119篇
  2000年   105篇
  1999年   49篇
  1998年   68篇
  1997年   48篇
  1996年   43篇
  1995年   44篇
  1994年   23篇
  1993年   33篇
  1992年   25篇
  1991年   23篇
  1990年   17篇
  1989年   10篇
  1988年   24篇
  1987年   9篇
  1986年   10篇
  1985年   7篇
  1984年   6篇
  1983年   3篇
  1982年   3篇
  1980年   4篇
  1979年   5篇
  1978年   3篇
  1977年   4篇
  1976年   3篇
  1975年   2篇
  1974年   5篇
排序方式: 共有3843条查询结果,搜索用时 15 毫秒
81.
The current leak tests for gloves are qualitative. The developed quantitative leak test uses vacuum pressure to draw measured volumes of water to detect microholes/tears in whole gloves and glove pieces. A modified plastic vacuum desiccator interfaced with a Frazier air permeability tester allowed exposure of disposable unsupported/unlined/powderless Kimtech Blue nitrile to 50 mL of water for glove pieces or to 600 mL within a whole glove at vacua of 8–9 in. (20–23 cm) and 11–12 in. (28–30 cm) water gauge, respectively. Punctures of known dimensions were made before testing in specific glove areas using 21-, 22-, 26-, 30-, and 33-gauge needles (outer/inner diameters in micrometres of 873/514, 794/413, 635/311, 476/127, 318/159 and 238/133, respectively). The length of the punctures varied from 0.13 ± 0.01 to 0.80 ± 0.11 mm. Flow rates of water through the holes/tears ranged from 2.5 ± 0.4 to 106 ± 7 mL/min for glove pieces. For whole gloves, the ranges were from 31 ± 9 to 543 ± 110 mL/min in the palm area; and 0.23 ± 0.06 to 82 ± 18 mL/min in the finger/fingertip area. The method quantified tear lengths as short as 0.13 ± 0.01 mm.  相似文献   
82.
The conduction model has been proposed for the metal-TiO2–Si (MIS) structures. Rutile films have been prepared on Si substrates by magnetron sputtering of TiO2 target and annealing in the air at temperatures T?=?800 and 1050 K. The current-voltage (CVC) and capacitance-voltage characteristics of the structures have been measured over the range of T?=?283–363 K. At positive potentials on the gate, the conductivity of the MIS structures is determined by the space charge-limited current in the dielectric layer.  相似文献   
83.
84.
In this paper, by the use of the topological current theory, the topological structures and the dynamic processes in thin-film ferromagnetic systems are investigated directly from the viewpoint of topology. It is found that the topological charge of a thin-film ferromagnetic system can be changed by annihilation or creation processes of opposite polarized vortex–antivortex pairs taking place at space–time singularities of the normalized magnetization vector field of the system, the variation of the topological charge is integer and can further be expressed in terms of the Hopf indices and Brouwer degrees of the magnetization vector field around the singularities. Moreover, the change of the topological charge of the system is crucial to vortex core reversal processes in ferromagnetic thin films. With the help of the topological current theory and implicit function theorem, the processes of vortex merging, splitting as well as vortex core reversal are discussed in detail.  相似文献   
85.
86.
A controllable etching process for indium zinc oxide (IZO) films was developed by using a weak etchant of oxalic acid with a slow etching ratio. With controllable etching time and temperature, a patterned IZO electrode with smoothed surface morphology and slope edge was achieved. For the practical application in organic light emitting devices (OLEDs), a sup- pression of the leak current in the current-voltage characteristics of OLEDs was observed. It resulted in a 1.6 times longer half lifetime in the IZO-based OLEDs compared to that using an indium tin oxide (ITO) anode etched by a conventional strong etchant of aqua regia.  相似文献   
87.
分析了实验室瞬态X射线产生的系统电磁脉冲(SGEMP)效应测试所面临的技术问题,提出了解决方法、措施以及实验室模拟瞬态X射线的SGEMP模拟试验方法。通过电子屏蔽、电磁屏蔽、光电隔离、信号对称提取等特殊技术处理,解决了SGEMP效应模拟试验方法和测量系统抗X射线、抗电磁辐射等技术问题,并在大型瞬态X射线模拟源上,测出了瞬态X射线辐照时金属腔内线缆的SGEMP效应波形及幅值。  相似文献   
88.
89.
Current in heterogeneous tunnel junctions is studied in the framework of the parabolic conduction-band model. The developed model of the electron tunneling takes explicitly into account the difference of effective masses between ferromagnetic and insulating layers and between conduction subbands. Calculations for Fe/MgO/Fe-like structures have shown the essential impact of effective mass differences in regions (constituents) of the structure on the tunnel magnetoresistance of the junction.  相似文献   
90.
A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins.Extensive Langevin simulations of the model are performed.We discuss the dependences of motion and efficiency on the model parameters,including the external force and the temperature.A good qualitative agreement with the expected behavior is observed.  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