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   1792篇
  免费   50篇
  国内免费   10篇
化学   1280篇
晶体学   21篇
力学   70篇
数学   110篇
物理学   371篇
  2024年   10篇
  2023年   20篇
  2022年   33篇
  2021年   39篇
  2020年   35篇
  2019年   62篇
  2018年   38篇
  2017年   35篇
  2016年   64篇
  2015年   32篇
  2014年   50篇
  2013年   144篇
  2012年   83篇
  2011年   155篇
  2010年   77篇
  2009年   49篇
  2008年   67篇
  2007年   71篇
  2006年   65篇
  2005年   46篇
  2004年   53篇
  2003年   40篇
  2002年   47篇
  2001年   27篇
  2000年   24篇
  1999年   11篇
  1997年   11篇
  1996年   16篇
  1995年   10篇
  1994年   13篇
  1993年   15篇
  1992年   16篇
  1988年   19篇
  1987年   21篇
  1986年   13篇
  1985年   19篇
  1984年   11篇
  1983年   15篇
  1980年   20篇
  1979年   11篇
  1978年   15篇
  1976年   9篇
  1975年   10篇
  1966年   25篇
  1965年   18篇
  1964年   14篇
  1963年   16篇
  1962年   43篇
  1961年   11篇
  1960年   12篇
排序方式: 共有1852条查询结果,搜索用时 14 毫秒
11.
In the present work angular momenta of the fragments corresponding to132Im,g have been deduced from the radiochemically determined independent isomeric yield ratios and statistical model based analysis in neutron induced fission of235U,239Pu and245Cm and spontaneous fission of252Cf. These data along with similar data on134I, reported earlier from this laboratory, bring out the effects of deformed 66n and spherical 82n shells on fragment angular momentum showing also an inverse correlation of the latter with elemental yields. Quantitative estimates of fragment scission point deformation and the coefficient of change of fragment angular momentum with kinetic/excitation energy have been deduced and are seen to be in good agreement with the expected theoretical estimates.  相似文献   
12.
40Ar-emulsion interactions are studied, to investigate the question of anomalons, in twoG- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect,N h dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level.  相似文献   
13.
Steady propagation of a single pulse in an inhomogeneously broadened resonant medium is studied. 2π-pulse solutions which are slightly different from those given in the literature are reported and it is shown that π-pulse solutions do not exist.  相似文献   
14.
15.
This is the report of the subgroup QCD of Working Group-4 at WHEPP-9. We present the activities that had taken place in the subgroup and report some of the partial results arrived at following the discussion at the working group meetings.  相似文献   
16.
Nanocrystalline Li2TiO3 was successfully synthesized using solid-state reaction method. The microstructural and electrochemical properties of the prepared material are systematically characterized. The X-ray diffraction pattern of the prepared material exhibits predominant (002) orientation related to the monoclinic structure with C2/c space group. HRTEM images and SAED analysis reveal the well-developed nanostructured particles with average size of ~40 nm. The electrochemical properties of the prepared sample are carried out using cyclic voltammetry (CV) and chronopotentiometry (CP) using Pt//Li2TiO3 cell in 1 mol L?1 Li2SO4 aqueous electrolyte. The Li2TiO3 electrode exhibits a specific discharge capacity of 122 mAh g?1; it can be used as anode in Li battery within the potential window 0.0–1.0 V, while investigated as a supercapacitor electrode, it delivers a specific capacitance of 317 F g?1 at a current density of 1 mA g?1 within the potential range ?0.4 to +0.4 V. The demonstration of both anodic and supercapacitor behavior concludes that the nanocrystalline Li2TiO3 is a suitable electrode material for supercapattery application.  相似文献   
17.
In this study, we successfully synthesized single-phase hexagonal closed packed (HCP) and face-centered cubic (FCC) nickel nanoparticles via reduction of nickel nitrate hexahydrate and nickel acetate tetrahydrate, respectively, in polyethylene glycol-200. Structural information of the as-synthesized nickel nanoparticles are studied by X-ray diffraction (XRD) as a function of the molar concentration of the nickel precursor. XRD results reveal that low concentrations of nickel precursor (0.005?M and below) favor the HCP, while high concentrations favor the mixture of HCP and FCC crystal structures. Particle size of HCP structure is found in the range of ~15?nm via transmission electron microscope analysis. Vibratory sample magnetometer is employed to study its magnetic behavior and the results reveal that FCC crystalline phase shows ferromagnetic nature with high saturation magnetization (M s?~?39.6?emu?gm?1) as compared to metastable HCP crystalline structure (M s?~?2?emu?gm?1). The surfactants bonding on the surface of nickel nanoparticles are studied.  相似文献   
18.
19.
A protoneutron star is formed immediately after the gravitational collapse of the core of a massive star. At birth, the hot and high density matter in such a star contains a large number of neutrinos trapped during collapse. Trapped neutrinos generally inhibit the presence of exotic matter — hyperons, a kaon condensate, or quarks. However, as the neutrinos diffuse out in about 10–15 s, the threshold for the appearance of strangeness is reduced; hence, the composition and the structure of the star can change significantly. The effect of exotic, negatively-charged, strangeness-bearing components is always to soften the equation of state, and the possibility exists that the star collapses to a black hole at this time. This could explain why no neutron star has yet been seen in the remnant of supernova SN1987A, even though one certainly existed when neutrinos were detected on Feb. 23, 1987. With new generation neutrino detectors it is feasible to test different theoretical scenarios observationally.  相似文献   
20.
We study three-dimensional conformal field theories described by U(N) Chern?CSimons theory at level k coupled to massless fermions in the fundamental representation. By solving a Schwinger?CDyson equation in light-cone gauge, we compute the exact planar free energy of the theory at finite temperature on ?2 as a function of the ??t?Hooft coupling ??=N/k. Employing a dimensional reduction regularization scheme, we find that the free energy vanishes at |??|=1; the conformal theory does not exist for |??|>1. We analyze the operator spectrum via the anomalous conservation relation for higher spin currents, and in particular show that the higher spin currents do not develop anomalous dimensions at leading order in 1/N. We present an integral equation whose solution in principle determines all correlators of these currents at leading order in 1/N and present explicit perturbative results for all three-point functions up to two loops. We also discuss a light-cone Hamiltonian formulation of this theory where a W ?? algebra arises. The maximally supersymmetric version of our theory is ABJ model with one gauge group taken to be U(1), demonstrating that a pure higher spin gauge theory arises as a limit of string theory.  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