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   1958篇
  免费   95篇
  国内免费   8篇
化学   1360篇
晶体学   37篇
力学   75篇
综合类   1篇
数学   133篇
物理学   455篇
  2024年   15篇
  2023年   18篇
  2022年   110篇
  2021年   94篇
  2020年   60篇
  2019年   69篇
  2018年   105篇
  2017年   89篇
  2016年   104篇
  2015年   66篇
  2014年   66篇
  2013年   172篇
  2012年   143篇
  2011年   135篇
  2010年   93篇
  2009年   77篇
  2008年   93篇
  2007年   85篇
  2006年   57篇
  2005年   49篇
  2004年   38篇
  2003年   29篇
  2002年   56篇
  2001年   36篇
  2000年   39篇
  1999年   12篇
  1998年   17篇
  1997年   12篇
  1996年   6篇
  1995年   8篇
  1994年   5篇
  1993年   8篇
  1992年   6篇
  1991年   4篇
  1990年   11篇
  1989年   7篇
  1988年   4篇
  1987年   6篇
  1986年   4篇
  1985年   3篇
  1984年   9篇
  1983年   3篇
  1982年   5篇
  1981年   3篇
  1980年   3篇
  1979年   6篇
  1978年   5篇
  1977年   3篇
  1974年   2篇
  1937年   2篇
排序方式: 共有2061条查询结果,搜索用时 31 毫秒
1.
2.
Journal of Thermal Analysis and Calorimetry - The operating temperature of Li-ion batteries used in modern electric vehicles should be maintained within an allowable range to avoid thermal runaway...  相似文献   
3.
LetP(z) be a polynomial of degreen which does not vanish in |z|<1. In this paper, we estimate the maximum and minimum moduli of thekth polar derivative ofP(z) on |z|=1 and thereby obtain compact generalizations of some known results, which among other results, yields interesting refinements of Erdos-Lax theorem and a theorem of Ankeny and Rivlin.  相似文献   
4.
A mathematical model of laser beam treatment of double layer alloys (Ni/Fe, Al/Fe and Cr/Fe systems) describing the effect of laser beam on different physical and geometrical parameters of coated layer system has been adapted. The numerical solutions of the non-homogeneous heat-transport differential equation could estimate the temperature of the treated region.The suggested model allows investigation of the temperature distribution as a function of treated surface and laser parameters. The physical parameters of the treated materials were taken as functions of temperature due to the change in the temperature of the treated double layer materials.  相似文献   
5.
In this paper we establish a sharp result concerning integral mean estimates for self-reciprocal polynomials.  相似文献   
6.
In solid state fermentation, Pleurotus sajor-caju has been found to be able to degrade at least 30% oil palm empty Fruit Bunch (EFB) fibre leaving 70 % useful materials. Conditions under which fermentation carried out were investigated. It was found that, in the temperature range between 25– 28 °C, relative ph between 6–8, moisture between 60–70 % and medium composition of CaCO3: rice bran 2 %: 5 % were the optimum conditions. The results showed in fermented products that, there were substantial reduction in cellulosic component such as Crude Fiber (CF, 18 %); Acid Detergent Fibre (ADF, 45 %), Neutral Detergent Fibre (NDF, 61 %) and Acid Detergent Lignin (ADL, 14 %). However, Crude Protein (CP, 10%) increased resulted from single cell protein enrichment of mycelial microbial mass. The mass reductions of substrate in fermentation process corresponds to the CO2 released during fermentation. Hence, attributable to the decreased in content of CF, ADF, NDF, and ADL. The digestibility study has also been carried out to determine the useful level of this product to ruminant. Aflatoxin content was detected low in both the initial substrates and products. Based on nutritional value and low content of aflatoxin, the product is useful as a source of roughage to ruminant.  相似文献   
7.
Curvature collineations are symmetry directions for the Riemann tensor, as isometries are for the metric tensor and Ricci collineations are for the Ricci tensor. Complete listings of many metrics possessing some minimal symmetry have been given for a number of symmetry groups for the latter two symmetries. It is shown that a claimed complete listing of cylindrically symmetric static metrics by their curvature collineations [1] was actually incomplete and is completed here. It turns out that in this complete list, unlike the previous claim, there are curvature collineations that are distinct from the set of isometries and of Ricci collineations. The physical interpretation of some of the metrics obtained is given.  相似文献   
8.
The scaled factorial moments and the multifractal moments have been investigated in differentη-intervals to study the dynamical fluctuation of pions produced in 200 AGeV32S-Ag/Br interaction. In order to investigate the detail characteristics of intermittency behaviour, theF-moments are extracted up to the eighth order of moments in differentM-intervals. The analysis indicates a non-thermal phase transition and different regime of particle production during the hadronisation process.  相似文献   
9.
In the title compound, C18H13BrClNO3, the heterocyclic ring of the indole is distorted from planarity towards an envelope conformation. The orientations of the indole, oxetane, chloro and bromo­phenyl substituents are conditioned by the sp3 states of the spiro‐junction and the Cl‐attached C atoms.  相似文献   
10.
We have investigated the synthesis of perovskite-type SrFeOx (2.5 x 3.0) using three preparative methods: sol-gel, mechanochemical processing and solid state reactions at high temperature of the corresponding oxides. The sample obtained after calcination of the gel from sol-gel method, contained the least amount of strontium carbonate impurity. The amount of strontium carbonate impurity decreased with the increase in calcination temperature. Perovskites obtained have been characterized by X-ray diffraction (XRD) and nitrogen adsorption isotherms. Samples obtained from three methods have been compared with respect to calcination temperature, crystallite size and specific surface area.Issued as NRCC No. 46479.  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