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   390篇
  免费   9篇
  国内免费   1篇
化学   210篇
晶体学   12篇
力学   4篇
数学   22篇
物理学   152篇
  2023年   4篇
  2020年   11篇
  2019年   15篇
  2018年   7篇
  2017年   10篇
  2016年   14篇
  2015年   5篇
  2014年   6篇
  2013年   24篇
  2012年   14篇
  2011年   19篇
  2010年   9篇
  2009年   11篇
  2008年   8篇
  2007年   17篇
  2006年   15篇
  2005年   16篇
  2004年   12篇
  2003年   12篇
  2002年   7篇
  2001年   3篇
  2000年   3篇
  1999年   9篇
  1998年   7篇
  1997年   3篇
  1996年   4篇
  1995年   5篇
  1994年   6篇
  1993年   5篇
  1992年   8篇
  1991年   6篇
  1990年   6篇
  1989年   3篇
  1988年   7篇
  1987年   4篇
  1986年   6篇
  1985年   10篇
  1984年   12篇
  1983年   5篇
  1982年   2篇
  1981年   10篇
  1980年   4篇
  1979年   3篇
  1977年   7篇
  1974年   3篇
  1973年   4篇
  1972年   2篇
  1971年   5篇
  1955年   2篇
  1954年   2篇
排序方式: 共有400条查询结果,搜索用时 15 毫秒
101.
Accurate gender determination is crucial in many scientific disciplines, especially in prenatal diagnosis of X-linked diseases and forensic investigations. Today, molecular techniques, especially typing for a length variation in the X–Y homologous amelogenin gene (AMEL X and AMEL Y), are used for gender assignation. This amelogenin is an integral part of most PCR multiplex kits for gender determination marker, but in 1998 there was a report of two normal males being typed as female with this marker. Subsequently, a small number of males with amelogenin deleted genes have been reported in various populations but little data are available characterizing these deletions. This review aims to explore possible relationships among the AMEL Y deleted samples and Y-chromosome microsatellite haplotypes. Also, attempts are made to determine the frequency of males with AMEL Y deleted gene in various countries across the globe. Although some studies have shown that males with AMEL Y deleted gene are extremely rare in most populations, typing an additional gender-determining locus should be considered in forensic investigations where the reference sample is of unknown gender.  相似文献   
102.
Solvent extraction of plutonium(VI) from nitric acid (1 to 5M) into 20% and 30% TBP in dodecane saturated with uranium(VI) (0% to 80%) has been studied. For a particular nitric acid concentration, the distribution coefficient (K d ) is found to decrease with the increase in saturation of organic phase with uranium(VI). At a fixed organic phase the saturationK d increased with increase in nitric acid concentration, however, the magnitude of this increase inK d decreased with the increase in saturation.  相似文献   
103.
Structures of complexes formed in aqueous solutions by some anionic polyelectrolytes (double and single stranded (ds and ss) DNA, poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS)) with a cationic surfactant system consisting of cetyltrimethylammonium bromide (CTAB) and sodium 3-hydroxy-2-naphthoate (SHN) have been determined using small angle X-ray diffraction. All complexes are found to have a two-dimensional (2-D) hexagonal structure at low SHN concentrations. Analysis of the diffraction data shows that the ds DNA—CTAB complex has an intercalated structure, with each DNA strand surrounded by three cylindrical micelles. On increasing SHN concentration, DNA—CTAB—SHN complexes exhibit a hexagonal-to-lamellar transition, whereas PVS complexes show a hexagonal → centered rectangular → lamellar transition. PSS complexes show yet another sequence of structures. These results indicate the significant influence of the chemical nature of the polyelectrolyte on the structure of the complexes.  相似文献   
104.
P. D. Semalty  Kapil Dev  P. N. Ram 《Pramana》2006,66(6):1077-1092
A detailed theoretical study of the low-temperature lattice specific heat of Ni-based dilute alloys has been carried out. Lattice Green’s function method has been used to calculate the local density of states of substitutional impurities and lattice specific heat in different alloys. The resonance condition has been investigated for possible occurrence of resonance modes. Except in NiCr and NiMn, low-frequency resonance modes have been obtained in all the alloys. However, no localized mode was obtained. The impurity-induced increase in lattice specific heat is explained on the basis of the obtained resonance modes. The calculation shows an excellent agreement with the measured lattice specific heat in these alloys  相似文献   
105.
Probability-one homotopy algorithms have strong convergence characteristics under mild assumptions. Such algorithms for mixed complementarity problems (MCPs) have potentially wide impact because MCPs are pervasive in science and engineering. A probability-one homotopy algorithm for MCPs was developed earlier by Billups and Watson based on the default homotopy mapping. This algorithm had guaranteed global convergence under some mild conditions, and was able to solve most of the MCPs from the MCPLIB test library. This paper extends that work by presenting some other homotopy mappings, enabling the solution of all the remaining problems from MCPLIB. The homotopy maps employed are the Newton homotopy and homotopy parameter embeddings.  相似文献   
106.
Motivated by recent observations of rheochaos in sheared wormlike micelles, we study the coupled nonlinear partial differential equations for the hydrodynamic velocity and order-parameter fields in a sheared nematogenic fluid. In a suitable parameter range, we find irregular, dynamic shear banding and establish by decisive numerical tests that the chaos we observe in the model is spatiotemporal in nature.  相似文献   
107.
108.
The band-head energies of the two-quasiparticle states expected in the doubly odd deformed nucleus170Ho are calculated for a zero range residual interaction. The results are compared with the available experimental information. It is concluded that the ground state has the Nilsson configuration 6+{7/2?[523↑] p }+5/2[512↑] n being the 2.76m isomer whereas the 43s isomer is the 1+ =0 state arising from the same configuration and lies at about 100 keV excitation energy in agreement with the experiment. The first excited state in this nucleus is predicted to be the 4?{3/2+[411↑] p +5/2?[521↑] n } state close to the ground state with the corresponding 1? =0 member expected to appear well above the 1+ isomer.  相似文献   
109.
A generalized VMD mechanism, implemented through the OPC model, is proposed for E1 and M1 decays of cc mesons wherein the photon couples to two infinite sequences of radial excitations of 3S1 and 3D1cc states. The results reveal good accord with data under the conventional assignments, with a parameter signifying a reduced magnetic coupling of ψ-ions with c quarks.  相似文献   
110.
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