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   949篇
  免费   48篇
  国内免费   2篇
化学   745篇
晶体学   3篇
力学   9篇
数学   116篇
物理学   126篇
  2023年   6篇
  2022年   8篇
  2021年   8篇
  2020年   10篇
  2019年   15篇
  2017年   10篇
  2016年   34篇
  2015年   28篇
  2014年   34篇
  2013年   23篇
  2012年   39篇
  2011年   39篇
  2010年   33篇
  2009年   27篇
  2008年   37篇
  2007年   42篇
  2006年   42篇
  2005年   31篇
  2004年   25篇
  2003年   22篇
  2002年   24篇
  2001年   21篇
  2000年   11篇
  1999年   13篇
  1998年   23篇
  1997年   12篇
  1996年   12篇
  1995年   26篇
  1994年   21篇
  1993年   11篇
  1992年   12篇
  1991年   13篇
  1989年   15篇
  1988年   10篇
  1987年   16篇
  1986年   17篇
  1985年   23篇
  1984年   13篇
  1983年   14篇
  1982年   18篇
  1981年   13篇
  1980年   17篇
  1979年   18篇
  1978年   13篇
  1977年   10篇
  1976年   9篇
  1975年   6篇
  1973年   12篇
  1971年   10篇
  1970年   5篇
排序方式: 共有999条查询结果,搜索用时 15 毫秒
61.
62.
The structure of hadronic final states in deep inelastic scattering expected from QCD is analyzed in terms of the shape parameters Hl and Cl. We find that the effects of the fragmentation of quarks and gluons into hadrons are typically governed by √s = [Q2(1/x?1)]12. For √s?30 GeV, the distributions of events in H2 and C2 should allow a test of the perturbative QCD prediction of three-jet events.  相似文献   
63.
64.
65.
Raman spectra of aqueous Zn(II)–perchlorate solutions were measured over broad concentration (0.50–3.54 mol-L–1) and temperature (25–120°C) ranges. The weak polarized band at 390 cm–1 and two depolarized modes at 270 and 214 cm–1 have been assigned to 1(a 1g), 2(e g), and 5(f 2g) of the zinc–hexaaqua ion. The infrared-active mode at 365 cm–1 has been assigned to 3(f 1u). The vibrational analysis of the species [Zn(OH2) 2 + ] was done on the basis of O h symmetry (OH2 as point mass). The polarized mode 1(a 1g)-ZnO6 has been followed over the full temperature range and band parameters (band maximum, full width at half height, and intensity) have been examined. The position of the 1(a 1g)-ZnO6 mode shifts only about 4 cm–1 to lower frequencies and broadens by about 32 cm–1 for a 95°C temperature increase. The Raman spectroscopic data suggest that the hexaaqua–Zn(II) ion is thermodynamically stable in perchlorate solution over the temperature and concentration range measured. These findings are in contrast to ZnSO4 solutions, recently measured by one of us, where sulfate replaces a water molecule of the first hydration sphere. Ab initio geometry optimizations and frequency calculations of [Zn(OH2) 2 + ] were carried out at the Hartree–Fock and second-order Møller–Plesset levels of theory, using various basis sets up to 6-31 + G*. The global minimum structure of the hexaaqua–Zn(II) species corresponds with symmetry T h. The unscaled vibrational frequencies of the [Zn(OH2) 2 + ] are reported. The unscaled vibrational frequencies of the ZnO6, unit are lower than the experimental frequencies (ca. 15%), but scaling the frequencies reproduces the measured frequencies. The theoretical binding enthalpy for [Zn(OH2) 2 + ] was calculated and accounts for ca. 66% of the experimental single-ion hydration enthalpy for Zn(II).Ab initio geometry optimizations and frequency calculations are also reported for a [Zn(OH2) 2 18 ] (Zn[6 + 12]) cluster with 6 water molecules in the first sphere and 12 in the second sphere. The global minimum corresponds with T symmetry. Calculated frequencies of the zinc [6 + 12] cluster correspond well with the observed frequencies in solution. The 1-ZnO6 (unscaled) mode occurs at 388 cm–1 almost in perfect correspondence to the experimental value. The theoretical binding enthalpy for [Zn(OH2) 2 18 ] was calculated and is very close to the experimental single ion-hydration enthalpy for Zn(II). The water molecules of the first sphere form strong hydrogen bonds with water molecules in the second hydration shell because of the strong polarizing effect of the Zn(II) ion. The importance of the second hydration sphere is discussed.  相似文献   
66.
67.
68.
Sticking probability for oxygen adsorption on thin iron films and readsorption on surface sites liberated due to incorporation of the adsorbate adatoms below the surface during thermal treatment has been studied by means of the Wagener flow method. Sticking probability for oxygen adsorption on oxidized thin iron films has also been measured for comparison.
, . .
  相似文献   
69.
The equilibrium bond distances, harmonic frequencies, and bond dissociation energies of the 21 homonuclear diatomics Li2—F2, Na2—Cl2, and K2—Br2 have been determined using approximate density functional theory (DFT) employing various widely used functionals and basis sets ranging from single zeta to triple zeta plus polarization quality. The results are in general much less sensitive to the size of the basis set as in conventional ab initio molecular orbital (MO) theory, while the choice of the functional is of much more significance. For one basis set (6-311G*), the performance of the DFT-based calculations has been compared and found to be superior to Hartree-Fock (HF) Møller Plesset second order perturbation theory (MP2), or configuration interaction with single and double excitations (CISD) calculations. Particularly, no pathological cases, such as the group 2 dimers (Be2, Mg2, Ca2), are observed. © 1995 by John Wiley & Sons, Inc.  相似文献   
70.
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