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   5091篇
  免费   131篇
  国内免费   8篇
化学   2991篇
晶体学   114篇
力学   171篇
数学   407篇
物理学   1547篇
  2023年   32篇
  2022年   71篇
  2021年   110篇
  2020年   116篇
  2019年   125篇
  2018年   126篇
  2017年   162篇
  2016年   195篇
  2015年   144篇
  2014年   193篇
  2013年   397篇
  2012年   312篇
  2011年   322篇
  2010年   215篇
  2009年   191篇
  2008年   257篇
  2007年   223篇
  2006年   157篇
  2005年   158篇
  2004年   126篇
  2003年   105篇
  2002年   111篇
  2001年   59篇
  2000年   54篇
  1999年   35篇
  1998年   33篇
  1997年   37篇
  1996年   42篇
  1995年   31篇
  1994年   32篇
  1993年   39篇
  1992年   48篇
  1991年   35篇
  1990年   39篇
  1989年   51篇
  1988年   44篇
  1987年   42篇
  1986年   32篇
  1985年   61篇
  1984年   57篇
  1983年   37篇
  1982年   44篇
  1981年   50篇
  1980年   44篇
  1979年   49篇
  1978年   44篇
  1977年   51篇
  1976年   54篇
  1975年   44篇
  1974年   38篇
排序方式: 共有5230条查询结果,搜索用时 721 毫秒
21.
Sea nodules were extensively studied over a wide range of temperature ranging from 77K to 1175K using Mossbauer effect and ESR. The Mossbauer studies of the nodules at 77K and room temperature show a quadrupole doublet whereas at higher temperatures magnetic spectra were obtained starting at around 875K which ultimately gives a hyperfine field of around 390 KOe at 1175 K. The Mossbauer spectra recorded at 30K did not show any significant change in the room temperature spectra. The analysis of the spectra upto 775K showed two positions of FeR+, vie., octahedral and tetrahedral which were varified by ESR of the diluted samples.  相似文献   
22.
23.
Our main object in this paper is to discuss some results on rings with left identity in which certain subsets satisfy some functional identities.  相似文献   
24.
Excess enthalpies of mixing H m E of tetrahydrofuran and tetrahydropyran with trichloromethane, tetrachloromethane, 1,2-dichloroethane, 1,1,2-trichloroethane and 1,1,2,2-tetrachloroethane have been determined at 26.9°C and are found to be negative over the entire composition range for both sets of the ether mixtures. H m E decreases in the sequence; dichloroethane > tetrachloromethane > trichloroethane > trichloromethane > tetrachloroethane. The results are explained on the basis of strong O...H-C and weak Cl...O specific interactions. Flory's theory has been used to correlate the experimental data with good agreement found between the theoretical and experimental values of H m E .  相似文献   
25.
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently.  相似文献   
26.
Recent X-ray diffraction studies on α-quartz (SiO2) by Kingmaet al [1], have shown the occurrence of a reversible, crystalline-to-crystalline, phase transition just prior to amorphization at ≈ 21 GPa. This precursor transition has also been confirmed by our recent molecular dynamics simulation study [2]. In order to investigate the possibility of a similar behaviour in other isostructural compounds, which also undergo pressure induced amorphization, α-GeO2 and α-AlPO4 (berlinite form) were studied using energy dispersive X-ray diffraction. In either of these materials, no such phase transition is detected prior to amorphization. The onset of amorphization and its reversal is found to be time dependent in GeO2.  相似文献   
27.
28.
29.
30.
An explicit expression has been derived for the volume dependence of electron-phonon coupling strength () by using a recently proposed quadratic form of the screened pseudopotential and by considering the variation of Fermi momentum with volume. Variation of Coulomb pseudopotential ( *) has also been explicitly considered by varying the Fermi momentum. Dependence of transition temperatureT c and the logarithm of the effective interaction strength (N 0 V) on the volume has been studied for eight nontransition metallic superconductors. A linear drop inT c for small values of (–/ 0) as well as the calculated values of= InN 0 V/ In, exhibits better matching with the experimental data, as compared to the earlier theoretical results.  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