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   406篇
  免费   5篇
化学   221篇
晶体学   5篇
力学   39篇
数学   19篇
物理学   127篇
  2021年   3篇
  2020年   9篇
  2019年   4篇
  2016年   12篇
  2015年   6篇
  2014年   3篇
  2013年   27篇
  2012年   13篇
  2011年   24篇
  2010年   14篇
  2009年   7篇
  2008年   22篇
  2007年   18篇
  2006年   21篇
  2005年   24篇
  2004年   10篇
  2003年   5篇
  2002年   6篇
  2001年   5篇
  2000年   6篇
  1997年   5篇
  1996年   4篇
  1995年   3篇
  1994年   2篇
  1993年   5篇
  1992年   7篇
  1991年   5篇
  1989年   5篇
  1988年   5篇
  1987年   7篇
  1986年   2篇
  1985年   6篇
  1984年   7篇
  1983年   5篇
  1982年   8篇
  1981年   3篇
  1980年   11篇
  1979年   6篇
  1978年   3篇
  1977年   10篇
  1976年   8篇
  1975年   4篇
  1974年   6篇
  1973年   9篇
  1972年   4篇
  1971年   4篇
  1967年   2篇
  1966年   3篇
  1935年   2篇
  1934年   2篇
排序方式: 共有411条查询结果,搜索用时 15 毫秒
61.
    
In May 2014, the Rosetta spacecraft is scheduled to rendezvous with the comet Churyumov-Gerasimenko ('67P'). One of the instruments on board the 'Lander' which will descend on to the surface of the comet is a miniaturised GC/MS system that incorporates an ion trap mass spectrometer, specially developed for isotope ratio analysis. This article describes the development and optimisation of the ion trap for this unique application, and presents a summary of the range of pre-programmed experiments that will contribute to the characterisation of the solid and volatile cometary materials.  相似文献   
62.
    
Several new liquid-crystalline indene and pseudoazulene systems are reported. These molecules give rise to either columnar hexagonal mesophases and/or columnar plastic phases. The unique nature of these compounds stems from their non-classical discotic structure. Although the molecules have rigid aromatic cores, they lack terminal tails and instead the polarizable atoms (S, halogens) or polar groups (CN, CO) act as unusual soft parts. On the basis of many structurally related materials, we conclude that for this type of compound molecular stacking in the solid state is a prerequisite for the appearance of a columnar mesophase, although other intermolecular interactions within the layers are also important in establishing liquid-crystalline order. The behavior reported for these mesomorphic molecules opens up new possibilities in the search for related molecular interactions that might be useful for the construction of supramolecular architectures with particular properties.  相似文献   
63.
64.
We have used our measurements of final states from e+e? containing an isolated muon and a hadronic or electron shower to search for new spin 0 charged particles. We exclude (95% CL) a supersymmetric partner of the τ with a mass less than 14 GeV/c2. We obtain upper limits on the branching ratio to τvτ for charged Higgs particles or technipions with masses up to 14 GeV/c2. This disagrees with some technicolor model predictions.  相似文献   
65.
66.
The paper outlines some effects of the reorganisation of the British National Health Service with its increasing emphasis on service planning. Current policies will involve substantial change in the configuration of the Health Service. Various aspects of the management of change, the involvement with decision makers and the implementation of results are discussed. It is expected that Operational Research in the health services will become more closely concerned with the medical and nursing aspects of the provision of care and the measured benefits to patients from this care. This involvement will assist in the production of more realistic models for decision making within districts, areas, regions and at the national level.  相似文献   
67.
Secondary ion mass spectroscopy (SIMS) was used to study the adsorption of carbon monoxide on polycrystalline nickel, copper, iron, palladium and tungsten foils. The results demonstrate the ability of SIMS to distinguish, qualitatively, between molecular and dissociative adsorption. A correlation between SIMS results and those obtained by infra-red spectroscopy for molecular adsorption is also suggested.  相似文献   
68.
The differential and total corss sections and the decay density matrix elements have been measured for the reactions, γp→ωp and γp→ωΔ+ (1232) in the photon energy range 2.8 to 4.8 GeV. The total cross sections for ωΔ+ (1232) photo-production are found to be slightly larger than those for elastic ω photo-production in this energy range. The data are compared to the predictions of a theoretical model and the contributing exchange mechanics are discussed.  相似文献   
69.
70.
We report the measurement of the reaction e+ + e? → hadronic jets at a center-of-mass energy √s=30 GeV using the MARK-J detector at PETRA. By measuring the energy and angular distribution of both neutrals and charged particles we were able to isolate unambiguously the three-jet events in a kinematic region where the backgrounds from qq and phase space contributions and other processes are small. Various comparisons of the data with quantum chromodynamics were made. The relative yield of three-jet events and the shape distribution of the events enable us to determine αs = 0.23 ± 0.02 (statistical error) with a systematic error of ± 0.04.  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