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   4065篇
  免费   707篇
  国内免费   352篇
化学   2686篇
晶体学   54篇
力学   298篇
综合类   18篇
数学   403篇
物理学   1665篇
  2024年   17篇
  2023年   111篇
  2022年   156篇
  2021年   177篇
  2020年   163篇
  2019年   159篇
  2018年   164篇
  2017年   125篇
  2016年   222篇
  2015年   202篇
  2014年   235篇
  2013年   310篇
  2012年   387篇
  2011年   373篇
  2010年   254篇
  2009年   219篇
  2008年   240篇
  2007年   225篇
  2006年   215篇
  2005年   179篇
  2004年   132篇
  2003年   105篇
  2002年   86篇
  2001年   73篇
  2000年   83篇
  1999年   69篇
  1998年   67篇
  1997年   52篇
  1996年   55篇
  1995年   52篇
  1994年   30篇
  1993年   40篇
  1992年   39篇
  1991年   23篇
  1990年   21篇
  1989年   15篇
  1988年   11篇
  1987年   7篇
  1986年   6篇
  1985年   10篇
  1984年   1篇
  1983年   6篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1978年   1篇
  1957年   1篇
排序方式: 共有5124条查询结果,搜索用时 0 毫秒
31.
Wang  Li  Duan  Liying  Wang  Enbo  Xiao  Dongrong  Li  Yangguang  Lan  Yang  Xu  Lin  Hu  Changwen 《Transition Metal Chemistry》2004,29(2):212-215
The novel complex, Co(H2O)5[Co(2,6-pydc)2] (1) has been prepared in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analyses and i.r. spectra. X-ray structural analysis revealed that three novel compounds each possess both stacking and hydrogen-bonding interaction three-dimensional (3-D) networks.  相似文献   
32.
熔融碳酸盐燃料电池阳极材料表面改性   总被引:1,自引:0,他引:1  
方百增  刘新宇 《电化学》1997,3(2):143-147
选择铌作为合金化元素,通过氟化物熔盐电化学表面合金化的方法对熔融碳酸盐燃料电池阳极材料镍进行表面改性,改性后的阳极材料的耐蚀性能与电催化性能均得到明显的改善。  相似文献   
33.
We studied the LAS degradation of immobilized Pseudomonas aeruginosa with low-intensity ultrasonic and the influence of original LAS concentration, pH, rotary velocity and different conditions of low-intensity ultrasonic irradiation on the degradation of LAS. In our experiment, the degradation rate of LAS was the main index. We found that low-intensity ultrasonic irradiation could improve the metabolism of microorganism cells and promote the LAS biodegradation of immobilized cells. In the experiment, 50 mg/l LAS were used to simulate wastewater, and low-intensity ultrasonic was considered. We found the influence was obvious, and the optimal degradation rate was acquired when the conditions of ultrasonic were frequency 24 kHz, power 8 W, stimulation time 5 s, intermissive time 30 s, and total time 10 min. The LAS degradation rate of immobilized cells with ultrasonic were respectively 40% and 9.5% higher than that of the suspending cells and immobilized cells without irradiation.  相似文献   
34.
In this paper, the authors study the multiplicity of solutions to the weighted p-Laplacian with isolated singularity and di?usion suppressed by convection ?div(|x|α|?u|p?2?u) + λ 1/|x|β |?u|p?2?u · x = |x|γg(|x|) in B \ {0} subject to nonlinear Robin boundary value condition |x|α|?u|p?2?u · ?n = A ? ρu on ?B,where λ > 0, B ? RN(N ≥ 2) is the unit ball centered at the origin, α > 0, p > 1, β ∈ R, γ > ?N, g ∈ C([0,1]) with g(0) > 0, A ∈ R, ρ > 0 and ?n is the unit outward normal. The same problem with di?usion promoted by convection, namely λ ≤ 0, has already been discussed by the last two authors (Song-Yin (2012)), where the existence, nonexistence and classi?cation of singularities for solutions are presented. Completely di?erent from [Song, H. J. and Yin, J. X., Removable isolated singularities of solutions to the weighted p-Laplacian with singular convection, Math. Meth. Appl. Sci., 35, 2012, 1089–1100], in the present case λ > 0, namely the di?usion is suppressed by the convection, non-singular solutions are not only existent but also may be in?nite which vary according only to the values of solutions at the isolated singular point. At the same time, the singular solutions may exist only if the di?usion dominates the convection.  相似文献   
35.
In this paper,we investigate the solvability,regularity and the vanishing dissipation limit of solutions to the three-dimensional viscous magnetohydrodynamic(MHD)equations in bounded domains.On the boundary,the velocity field fulfills a Navier-slip condition,while the magnetic field satisfies the insulating condition.It is shown that the initial boundary value problem has a global weak solution for a general smooth domain.More importantly,for a flat domain,we establish the uniform local well-posedness of the strong solution with higher-order uniform regularity and the asymptotic convergence with a rate to the solution of the ideal MHD equation as the dissipations tend to zero.  相似文献   
36.
37.
38.
39.
40.
Photoinduced electron transfer of the model system composed of vitamin E and duroquinone has been investigated using time-dependent density functional theory. Calculations for the excited states tell that the photoexcitation of the model system can directly yield the charge transfer states in which the vitamin E moiety is positively charged but the duroquinone moiety is negatively charged. Our theoretical investigations indicate that the second charge transfer state of the model system can also be produced through the decay of higher locally excited state S(4). Since S(4) state in the model system corresponds to S(1) state of the isolated duroquinone used as a model for peroxyl radical, and S(2) state has the character of electron transfer from the tertiary amine group of the vitamin E moiety to the duroquinone moiety, the decay from S(4) to S(2) corresponds to the dynamic process following the photoexcitation of the duroquinone moiety of the model system, i.e., the initial stage of antioxidant reaction of vitamin E. Calculations of the kinetic parameters for the electron transfer have been carried out in the framework of the Marcus-Jortner-Levich formalism. Our calculations confirm that the electron transfer from S(4) to S(2) possesses the character of the inverted regime and the barrier is negligibly small.  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