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   5176篇
  免费   39篇
  国内免费   7篇
化学   2465篇
晶体学   124篇
力学   173篇
综合类   3篇
数学   602篇
物理学   1855篇
  2019年   46篇
  2018年   67篇
  2017年   68篇
  2016年   74篇
  2015年   53篇
  2014年   81篇
  2013年   210篇
  2012年   160篇
  2011年   186篇
  2010年   109篇
  2009年   141篇
  2008年   175篇
  2007年   182篇
  2006年   151篇
  2005年   134篇
  2004年   138篇
  2003年   115篇
  2002年   119篇
  2001年   108篇
  2000年   106篇
  1999年   91篇
  1998年   53篇
  1997年   57篇
  1996年   70篇
  1995年   63篇
  1994年   71篇
  1993年   57篇
  1992年   74篇
  1991年   74篇
  1990年   84篇
  1989年   60篇
  1988年   46篇
  1987年   60篇
  1986年   62篇
  1985年   60篇
  1984年   82篇
  1983年   88篇
  1982年   82篇
  1981年   89篇
  1980年   99篇
  1979年   75篇
  1978年   90篇
  1977年   96篇
  1976年   71篇
  1975年   52篇
  1974年   48篇
  1973年   44篇
  1972年   37篇
  1971年   34篇
  1969年   34篇
排序方式: 共有5222条查询结果,搜索用时 31 毫秒
41.
IR spectroscopy and viscometry data have shown that poly(acrylic acid) and poly(methacrylic acid) form complexes with agar-agar in aqueous solutions as they do with other polysaccharides. The polyacid-agar-agar complexes are typical hydrogels. The swelling index of hydrogels based on the poly(methacrylic acid)-agar-agar complex has been found to be markedly lower than that of poly(acrylic acid)-agaragar complex. The hydrogels based on the complex of cross-linked poly(acrylic acid) with agar-agar can be of practical interest as polymeric carriers for drugs.  相似文献   
42.
Using pulsed neutrons of 19.8 Å wavelength a quasielastic line broadening as low as 0.03 eV (FWHM) has been observed due to Na+ diffusion in the glass Na2O·2SiO2. From the linewidths a Na+ self-diffusion coefficient of 3.1·10–8 cm2/s at 420°C was obtained in excellent agreement with the diffusion coefficient determined for the same sample batch using22Na radioactive tracers. The experimental Q dependence of the quasielasic linewidths gives a hint for deviations from a purely random walk in an ionic glass.  相似文献   
43.
The electric quadrupole interaction of55Mn nuclei was studied in the weakly ferromagnetic system MnSi using muon level-crossing resonance (LCR) technique. The temperature dependence of the electric field gradient (EFG) shows a critical behavior near the ferromagnetic transition temperature, indicating that the EFG due to the conduction electron is strongly correlated with the magnetic susceptibility in the itinerant electron magnetism. The temperature dependence of EFG is in reasonable agreement with the self-consistent renormalization theory developed by Moriya and coworkers.We gratefully acknowledge helpful discussion with Dr. N. Nishida. We also wish to thank Keith Hoyle and Curtis Ballard for technical support.  相似文献   
44.
The NMR enhancement factor of a frozenCuMn spin glass has been measured at a temperatureT?T g /5. The measurements were performed as function of static magnetic fields of different directions. A two component model of a spin glass has been outlined. One component being a “system of single spins” and the other one being a “subsystem of clusters”. Both components were attributed to different kinds of interaction being RKKY and dipole interaction respectively. The effective anisotropy field of the single spin system consists of two unidirectional contributionsH a s andH a c , which have been measured for different conditions. A second anisotropy fieldH d binds the cluster system to the system of single spins. All anisotropy fields depend on the annealing temperature of the alloys.  相似文献   
45.
We discuss in full detail the basic results of the theory of subdynamics. We analyse the regularity requirements of the projective components of the resolvent in the theory and correct a recent mathematical result of M. Courbage regarding the impossibility of simultaneous analytic continuation of the collision and creation operators. We offer further some critiques on the interpretation of the various results of the subdynamics formalism.  相似文献   
46.
We have carried out neutron diffraction on a HoCo2Si2 powder sample at 4.2 K. The magnetic structure of this compound is collinear antiferromagnetic with the holmium magnetic moments parallel to the c-axis of the crystal. The magnetic moment value of holmium is 9.85 μB. The magnetic space group is I4/mm'm' (Sh410128) k = 000 The ordering temperature is tn = 12(1) K.  相似文献   
47.
An explicit expression is obtained for the Green's functions of a massive scalar field for nonnull temperatures and density in the form of a series in powers of m/T. The equivalence of the spectral-geometric approach and the temperature technique of Matsubara and Bernard is demonstrated. Corrections to the Stefan-Boltzmann law are obtained on the basis of the calculated Green's functions. The energy density is calculated in regions of high and low temperatures. The formulas obtained can prove to be useful in the discussion of the phase transition hadrons-quark-gluon plasma.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 32–40, July, 1991.  相似文献   
48.
High quality flux grown and defect enriched peritectically grown YBa2Cu3O7–x single crystals have been investigated by an ac-susceptibility technique. This method allows to determine an irreversibility line from the temperature and field dependence of the peaked imaginary part of the susceptibility, which is due to magnetic losses. For magnetic fieldsH ac perpendicular to thec-axis of the crystal, the irreversibility line of the defect enriched crystal shows a shift to higher field values as compared to the perfect crystal, a sign that crystal defects like Y2BaCuO5(211)-precipitates and microcracks act as strong pinning centers. ForH ac parallel to thec-axis no clear evidence for a stronger pinning is found. From these results we conclude that different pinning mechanisms are dominating at different field orientations.  相似文献   
49.
50.
The influence of spatio-temporal external multiplicative fluctuations on a single kink in a bistable distributed system is studied. For this purpose we derive a stochastic dynamic equation for the position of the shifted kink. An analytical estimate for spatio-temporally uncorrelated fluctuations is represented and discussed. We draw the conclusion that multiplicative noise induces a propagation of the most probable kink into the region of larger noise. This effect is demonstrated in numerical simulations.  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