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   1054篇
  免费   32篇
  国内免费   4篇
化学   851篇
晶体学   6篇
力学   7篇
数学   34篇
物理学   192篇
  2020年   11篇
  2019年   13篇
  2018年   12篇
  2017年   7篇
  2016年   14篇
  2015年   20篇
  2014年   20篇
  2013年   53篇
  2012年   47篇
  2011年   47篇
  2010年   28篇
  2009年   36篇
  2008年   48篇
  2007年   48篇
  2006年   50篇
  2005年   49篇
  2004年   45篇
  2003年   40篇
  2002年   44篇
  2001年   26篇
  2000年   39篇
  1999年   23篇
  1998年   13篇
  1997年   7篇
  1996年   22篇
  1995年   13篇
  1994年   19篇
  1993年   14篇
  1992年   14篇
  1991年   7篇
  1990年   12篇
  1989年   14篇
  1988年   12篇
  1987年   11篇
  1986年   13篇
  1985年   15篇
  1984年   16篇
  1983年   7篇
  1982年   9篇
  1981年   18篇
  1980年   6篇
  1979年   7篇
  1978年   11篇
  1977年   18篇
  1976年   15篇
  1975年   13篇
  1974年   11篇
  1973年   9篇
  1971年   7篇
  1969年   6篇
排序方式: 共有1090条查询结果,搜索用时 31 毫秒
101.
The excitation and subsequent proton decay of the isovector spin-flip giant monopole resonance (IVSGMR) is studied via the 208Pb(3He,t) reaction at 410 MeV. In the inclusive spectrum (60+/-5)% of the non-energy-weighted sum-rule strength for this 2 variant Planck's over 2h omega resonance was found in the region 29相似文献   
102.
The first solid-phase synthesis of 1,2,4-benzothiadiazin-3-one 1,1-dioxides has been developed. Synthesis of the title compounds was achieved by the reduction of 2-nitrobenzenesulfonamides, followed by cyclization with carbonyldiimidazole. Because 1,2,4-benzothiadiazin-3-one 1,1-dioxides have been known to possess various bioactivities, this method is useful from the viewpoint of new drug discovery. In addition to the excellent purity of the title compounds, a large number of compounds can be synthesized with this method, because this synthesis includes four diversity points.  相似文献   
103.
Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.  相似文献   
104.
It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced.  相似文献   
105.
(19)F homonuclear dipolar recoupling methods were used to measure internuclear distances ranging from 5 to 12 A in fluorinated organic compounds in the solid state. Magic-angle-spinning-based high-resolution techniques were utilized. Trifluoromethyl and aromatic fluorine groups were separated by rigid aromatic spacers; these compounds were diluted into nonfluorinated host molecule matrices to give isolated homonuclear spin pairs with known internuclear distances. Radiofrequency-driven recoupling (RFDR) was used to elicit magnetization exchange between the spin pairs in 1D and 2D experiments. Simulation of the exchange was accomplished using a Monte Carlo-type algorithm to search the parameter space. These methods allow the determination of distances with an accuracy of 1 A at shorter distances and 2 A at longer distances, with the assumption of no prior knowledge of T(2)(ZQ).  相似文献   
106.
The sequential analysis of a peptide of CDYEGRLI, relating to the nucleic proteins in influenza virus, was performed by the postsource decay (PSD) fragmentation method using matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The sequence of the peptide was difficult to analyze by MALDI-MS since the PSD fragment ions of the peptide were almost never observed and were not amenable to complete sequence interpretation. The peptide was modified by 4(5)-(iodoacetamide) fluorescent reagent to improve the sensitivity of the MALDI-PSD fragment spectrum. In the spectrum of the fluorescent modified peptide, almost all sequential b-series fragment ions were observed clearly, which was sufficient for complete sequence interpretation. The results indicate the advantage of fluorescent modification for the total sequencing of the peptides by MALDI-MS.  相似文献   
107.
The adhesion strength of polybutylene terephthalate (PBT) on aluminum was investigated using density functional theory-based total energy calculations. Aluminum atom was connected to a PBT monomer at different orientations and total energies were calculated in order to determine the most stable orientation. The energy differences showed that the Al oriented at 180° with the ester group of the monomer bonded strongly. Using this orientation, the PBT monomer-adhesion on aluminum surface and the aluminum atom adhesion on PBT bulk were also investigated.  相似文献   
108.
109.
110.
We modified a commercially available thermogravimetric analyzer to introduce helium alone or with steam, oxygen or both, atmosphere of which was controllable to be similar to that in a fixed-bed or an entrained-flow type gasifier, for studying basic properties of biomass gasification. We also connected it to a gas chromatograph-mass selective detector for identifying materials produced during the thermogravimetric analyses. Thermogravimetric analyses of Japanese cedar wood and identifications of the produced materials at around 365 °C were measured as demonstrations.  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