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   198133篇
  免费   2250篇
  国内免费   491篇
化学   108134篇
晶体学   2483篇
力学   7933篇
综合类   11篇
数学   19058篇
物理学   63255篇
  2020年   1720篇
  2019年   1918篇
  2018年   2237篇
  2017年   2355篇
  2016年   3516篇
  2015年   2194篇
  2014年   3547篇
  2013年   9082篇
  2012年   6512篇
  2011年   8014篇
  2010年   5702篇
  2009年   5656篇
  2008年   7160篇
  2007年   7072篇
  2006年   6698篇
  2005年   6053篇
  2004年   5477篇
  2003年   4995篇
  2002年   4408篇
  2001年   5922篇
  2000年   4364篇
  1999年   3248篇
  1998年   2506篇
  1997年   2504篇
  1996年   2400篇
  1995年   2366篇
  1994年   2265篇
  1993年   2111篇
  1992年   2745篇
  1991年   2648篇
  1990年   2606篇
  1989年   2603篇
  1988年   2642篇
  1987年   2646篇
  1986年   2499篇
  1985年   3232篇
  1984年   3241篇
  1983年   2523篇
  1982年   2640篇
  1981年   2701篇
  1980年   2477篇
  1979年   2821篇
  1978年   2821篇
  1977年   2946篇
  1976年   2784篇
  1975年   2530篇
  1974年   2473篇
  1973年   2440篇
  1972年   1676篇
  1968年   1703篇
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
11.
12.
Siberian Mathematical Journal - Under study is the multidimensional inverse problem of determining the convolutional kernel of the integral term in an integro-differential wave equation....  相似文献   
13.
Russian Physics Journal - The process of radiative decay of a Higgs boson into a fermion-antifermion pair $$ H\Rightarrow \overline{ff}\upgamma . $$ is investigated within the framework of the...  相似文献   
14.
Physics of Atomic Nuclei - A model of dynamics with separate temperature feedback formed by average temperatures of the fuel and the coolant is constructed for the IBR-2M pulsed reactor of periodic...  相似文献   
15.
Activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP)-based aqueous miniemulsion polymerization where the polymerization takes place in the stabilized monomer droplets is described. In this work, we compared styrene, n-butyl methacrylate (nBMA) and tert-butyl methacrylate (tBMA) and investigated the influence of their hydrophobicity on dispersity, molecular weight and particle stability based their partition coefficients (logP) (2.67, 2.23, and 1.86, respectively). Tetrabutylammonium bromide (TBAB) was used as a phase transfer agent for the controlled delivery of Cu2+-Br/tris(2-pyridylmethyl)amine (TPMA), a hydrophilic catalyst, into monomer droplets of varying hydrophobicity. The resulting dispersity and particle stability of each polymer is a function of its logP value, with the most hydrophobic monomer (styrene) displaying the narrowest dispersity and most control (Đ < 1.3), and the most hydrophilic polymer poly(tert-butyl methacrylate) (PtBMA) having reduced emulsion stability, determined by the observation of aggregate formation. Selected polymerization parameters, including effects of total ascorbic acid feed concentration and the monomer concentration and their effects on dispersity are reported. The controlled polymerizations of hydrophilic monomers using ARGET-ATRP in miniemulsion conditions and understanding the effect of monomer hydrophilicity on the emulsion stability will broaden the use of ARGET-ATRP in emulsion polymerization for the synthesis of polymer-grafted nanoparticles with hydrophilic corona.  相似文献   
16.
17.
Photo-catalytic elimination of organic contaminants plays a significant role in wastewater treatment. Developing a highly efficient photo-catalyst is one of the leading research topic. Herein, we reported the fabrication of a novel nanoporous NiO@SiO2 photo-catalyst by a simple ion-exchange method to eliminate the reactive dyes. The synthesized NiO@SiO2 catalyst exhibited fast photo-degradation and excellent adsorption capability and could efficiently remove Red FN-3GL dye from wastewater, due to a high loading of NiO and a large specific surface area, abundant electron-withdrawing groups, as well as narrow bandgap energy. In addition, the NiO@SiO2 photo-catalyst also displayed a high capability to remove reactive dyes over a wide range of pH values (pH 3–9). The prominent adsorption and photo-degradation of dyes were strongly dependent on the surface charge of the catalyst and the generation of hydroxyl radicals (OH?) by the catalyst, respectively. Furthermore, the NiO@SiO2 photo-catalyst also exhibited excellent recyclability, thus demonstrating the feasibility of practical applications in industries. The strategy of covering the metal oxide to nanoporous silica is a promising method for developing active photo-catalysts and applying them in the wastewater treatments.  相似文献   
18.
Numerical Algorithms - Inthis paper, we discuss two first-order completely discrete schemes based on Backward Euler and its linearized variant methods for the 2D Sobolev equations with...  相似文献   
19.
Premchand  V. P.  Balaram  Bipin  Mani  Ajith K.  Narayanan  M. D.  Sajith  A. S. 《Nonlinear dynamics》2022,110(1):573-588
Nonlinear Dynamics - Optimisation procedures for nonlinear vibrating systems are made cumbersome due to the fact that the regimes of periodic response are not known beforehand. Moreover, such...  相似文献   
20.
Journal of Structural Chemistry - N-cyanomethylanabasine is prepared with an yield of 70% by the interaction of the alkaloid anabasine with glyconitrile. It is shown that the highest yield of the...  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