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   870篇
  免费   7篇
  国内免费   3篇
化学   448篇
晶体学   9篇
力学   26篇
数学   49篇
物理学   348篇
  2024年   6篇
  2023年   15篇
  2022年   17篇
  2021年   27篇
  2020年   31篇
  2019年   30篇
  2018年   19篇
  2017年   18篇
  2016年   31篇
  2015年   13篇
  2014年   25篇
  2013年   41篇
  2012年   30篇
  2011年   40篇
  2010年   31篇
  2009年   24篇
  2008年   37篇
  2007年   38篇
  2006年   38篇
  2005年   33篇
  2004年   34篇
  2003年   24篇
  2002年   12篇
  2001年   26篇
  2000年   14篇
  1999年   8篇
  1998年   5篇
  1997年   6篇
  1995年   7篇
  1994年   10篇
  1993年   9篇
  1992年   8篇
  1991年   12篇
  1990年   13篇
  1989年   9篇
  1988年   14篇
  1987年   10篇
  1986年   8篇
  1985年   10篇
  1984年   11篇
  1983年   6篇
  1982年   6篇
  1981年   11篇
  1980年   18篇
  1979年   4篇
  1978年   7篇
  1977年   7篇
  1974年   5篇
  1973年   4篇
  1933年   3篇
排序方式: 共有880条查询结果,搜索用时 0 毫秒
211.
    
In many intracellular processes, the length distribution of microtubules is controlled by depolymerizing motor proteins. Experiments have shown that, following non-specific binding to the surface of a microtubule, depolymerizers are transported to the microtubule tip(s) by diffusion or directed walk and, then, depolymerize the microtubule from the tip(s) after accumulating there. We develop a quantitative model to study the depolymerizing action of such a generic motor protein, and its possible effects on the length distribution of microtubules. We show that, when the motor protein concentration in solution exceeds a critical value, a steady state is reached where the length distribution is, in general, non-monotonic with a single peak. However, for highly processive motors and large motor densities, this distribution effectively becomes an exponential decay. Our findings suggest that such motor proteins may be selectively used by the cell to ensure precise control of MT lengths. The model is also used to analyze experimental observations of motor-induced depolymerization.https://doi.org/10.1209/0295-5075/83/40006  相似文献   
212.
We report the electrical resistivity of HCl doped polyaniline in the temperature range 77 T 300 K. A maximum is obtained in the conductivity versus concentration of HCl curve at 3(N) HCl. The resistivity of the sample has been observed to show a decreasing trend with increase in temperature. The resistivity obeys the Mott variable range hopping theory. The Mott characteristic temperature (T Mott) is very low in this sample compared to other studies. The Hall voltages have been found to be negative. The Hall coefficient, carrier concentration, and density of states have been determined from Hall measurement. From the conductivity versus temperature plot, different physical quantities such as localisation length and molecular vibrational frequency have been determined.  相似文献   
213.
214.
Functional parameters contributing to the recognizable good performance of a highly crosslinked olefinic polymer based on cyclopentadiene have been evaluated by a limited range of stress decay and creep recovery from a fixed deformation over constant time periods. The experimental design for these involved a calculated stress (load) at the initial sample deformation (displacement) for determination of changes in stress in bending mode and flex creep under applied load at three constant temperature segments of 6 h each with 20 min recovery time between segments. The results have identified a behavior which is typical of interfacial orientational effect in a two-component system. Thermal conductivity, heat capacity and density at the same temperatures were measured for determination of variations in thermal diffusivity as an indication of the competing effects of densification and thermal expansion for such a system.Static charging and polarization experiments were performed for evaluation of other desired uses of this material, in moving parts and in direct or induced voltage applications. The latter allows measurement of dynamic charge transport through the resin matrix. Calculations indicate generation of charge carriers from weak secondary bonding typical of polymer interlaces. The polarization itself consists of dipole orientation characterized by relatively high activation energy.The intrinsic mechanical properties for this material had been determined by the manufacturer, but the performance parameters reported in this study have been determined for the first time for exploration of further uses for this material.The author wishes to acknowledge the assistance provided by Ralph Pitman in the preparation of the samples for this work.  相似文献   
215.
The hydrated clusters of tetrahydroisoquinoline have been investigated by laser-induced fluorescence (LIF), UV-UV hole burning, and IR-UV double-resonance spectroscopy in a seeded supersonic jet. Clusters of different sizes and isomeric structures have different 0-0 transitions (origins) in the LIF spectrum. UV-UV hole burning spectroscopy has been used to identify different cluster species and their vibrational modes. The structures of the clusters have been predicted by comparing the observed OH and NH frequencies in the IR-UV double-resonance spectra with the results calculated at different levels of sophistication. It is found that the water molecules form linear and six- and eight-membered cyclic H-bonded structures at the nitrogen center of 1:1, 1:2, and 1:3 clusters, respectively.  相似文献   
216.
217.
Ultrafast all-optical NOR gate based on two photon absorption (2PA) process in SOI waveguide is already established. We have designed NAND gate also based on this process with a novel waveguide coupler structure. Power attenuation due to 2PA process and the working of these gates is developed with FDTD simulation. Dominant 2PA process is incorporated in FDTD update equations and it is shown that the influence of high intensity pump pulses on a different frequency continuous probe beam can be utilized to form NOR as well as NAND gates.  相似文献   
218.
219.
Nonlinear integrable systems in (2 + 1)dimensions which are supersymmetric are generated in twodifferent ways. In one approach the homogeneous spacesof super-Lie algebra are used, and in the other we use a different technique of extending thedimension of the system. The two sets of equations turnout to be different. The methodologies ofDarbux–Backlund transformation and gaugetransformation are used to generate the Backlund transformations ofthese equations. An important result of our analysis isthe existence of purely fermionic nonlinear systems in(2 + 1) dimensions.  相似文献   
220.
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