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   204118篇
  免费   1311篇
  国内免费   437篇
化学   105317篇
晶体学   3391篇
力学   10287篇
综合类   10篇
数学   22040篇
物理学   64821篇
  2021年   1977篇
  2020年   2033篇
  2019年   2589篇
  2018年   3669篇
  2017年   3682篇
  2016年   4844篇
  2015年   2375篇
  2014年   4331篇
  2013年   8629篇
  2012年   6900篇
  2011年   8126篇
  2010年   6506篇
  2009年   6682篇
  2008年   7713篇
  2007年   7688篇
  2006年   6782篇
  2005年   6006篇
  2004年   5688篇
  2003年   5214篇
  2002年   5207篇
  2001年   5628篇
  2000年   4160篇
  1999年   3142篇
  1998年   2713篇
  1997年   2768篇
  1996年   2564篇
  1995年   2217篇
  1994年   2336篇
  1993年   2230篇
  1992年   2525篇
  1991年   2651篇
  1990年   2553篇
  1989年   2622篇
  1988年   2531篇
  1987年   2551篇
  1986年   2411篇
  1985年   3032篇
  1984年   3102篇
  1983年   2596篇
  1982年   2564篇
  1981年   2532篇
  1980年   2336篇
  1979年   2709篇
  1978年   2671篇
  1977年   2870篇
  1976年   2872篇
  1975年   2664篇
  1974年   2602篇
  1973年   2711篇
  1972年   2085篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
121.
122.
123.
124.
125.
126.
Bismuth, antimony and its alloys are the typical representatives of a class of semimetals, which electric conductance is lower in 102-103 times, than of usual well conducting an electrical current metals. The alloys bismuth with antimony have semi-conductor properties in wide area of compositions at temperatures below 77 °K. The semimetals are rather perspective materials from the point of view of their probable application in various devices [1,2,3].In present time the semimetal alloys BiSb have wide application in thermoelectric generators and refrigerators. In work [3] the opportunity of use of semimetals BiSb with percentage content of Bi and Sb from 8 % up to 25 % was shown as high-sensitivity and of small inertion indicators of the mm range radiation where thermoelectric effect is used. The principle of action of such indicators is based on occurrence of temperature gradient in a semimetal crystal BiSb that has two contacts of the various area with flowing electrical current. Basic element of such device is the dot contact metal - semimetal. One of the main characteristics is volt-watt sensitivity of metal-semimetal BiSb contact which calculating is shown in present work.  相似文献   
127.
Nonlinear (at the second-harmonic frequency of the incident light) optical reflection by two-dimensional magnetic superstructures is theoretically studied. A square lattice of magnetic dots and a hexagonal lattice of magnetic bubbles (cylindrical magnetic domains) are considered. Because the periods of these structures are comparable with the wavelengths of the fundamental and the second-harmonic radiation, it would be possible to observe diffraction at the second-harmonic frequency. A polarization analysis of nonlinearly diffracted radiation is performed and the numbers of observable diffraction orders for the above structures are estimated. Received: 10 January 2002 / Published online: 11 June 2002  相似文献   
128.
A cluster mechanism is considered for the detachment of particles when the surface of a high-temperature superconducting target absorbs laser pulses. By proposing a fractal nature for the surface, one can model it as an assembly of a large number of nonlinear oscillators (clusters). Utilizing the method of sudden perturbations, a calculation was made of the probability of dissociation of these oscillators, i.e., of the detachment of clusters from the surface. The calculated probability decreases rapidly as the power density of the laser radiation is reduced to some limiting value. This is in agreement with experiments. State Institute of Sensory Microelectronics. Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 73–77, June, 1997.  相似文献   
129.
The mutual coupling of the radiating elements in microstrip antennas is studied using a rigorous electrodynamic approach in which the field singularities at the radiator edges are taken into account with analytic accuracy. A spectral method is employed in combination with a method of semi-inversion by extraction of the Green-function singularity. The degree of interaction of the elements of microstrip structures at the fundamental and higher current harmonicsis determined, and the applicability of various approximations is assessed.Radio-Astronomy Institute, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 8, pp. 688–701, August, 1992.  相似文献   
130.
A two-dimensional self consistent model of the Beam-Plasma-Discharge (BPD) has been developed to calculate the discharge ignition of a bandlike electron beam in a discharge chamber. The discharge was considered in Argon with an initial concentration of 1014 cm?3. The model allows calculation of the time evolution of perpendicular profiles of electron density, temperature and the potential.  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