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   954篇
  免费   25篇
  国内免费   11篇
化学   675篇
晶体学   5篇
力学   9篇
数学   162篇
物理学   139篇
  2023年   5篇
  2022年   26篇
  2021年   24篇
  2020年   19篇
  2019年   24篇
  2018年   15篇
  2017年   26篇
  2016年   42篇
  2015年   17篇
  2014年   30篇
  2013年   74篇
  2012年   43篇
  2011年   72篇
  2010年   51篇
  2009年   38篇
  2008年   57篇
  2007年   49篇
  2006年   49篇
  2005年   39篇
  2004年   32篇
  2003年   31篇
  2002年   27篇
  2001年   20篇
  2000年   16篇
  1999年   16篇
  1998年   11篇
  1997年   9篇
  1996年   8篇
  1995年   4篇
  1994年   9篇
  1993年   7篇
  1992年   8篇
  1991年   3篇
  1990年   4篇
  1989年   4篇
  1986年   4篇
  1984年   5篇
  1983年   5篇
  1982年   4篇
  1980年   8篇
  1979年   5篇
  1977年   2篇
  1976年   7篇
  1975年   2篇
  1974年   3篇
  1973年   4篇
  1972年   6篇
  1971年   6篇
  1965年   4篇
  1937年   2篇
排序方式: 共有990条查询结果,搜索用时 15 毫秒
981.
A convenient and simple method for preparation of commercial nonwovens with antimicrobial properties was elaborated. The process consists in preparation of poly(l ‐lactide) microspheres (from poly(l ‐lactide) with M n  = 10,560 and M w /M n  = 1.39) containing triclosan (5‐chloro‐2‐(2,4‐dichlorophenoxy) phenol) and loading them onto the nonwovens. The microspheres were prepared by spray drying (D n  = 3.91 μm, D w /D n  = 2.43) and oil‐in‐water emulsification‐solvent evaporation method (D n  = 5.84 μm, D w /D n  = 1.25). Content of triclosan in microspheres ranged from 4.65 to 4.95 wt%. The antibacterial nonwovens were prepared by padding of the fibers with the microspheres using the microsphere suspension. The resulting antibacterial nonwovens were examined using inhibition zone measurement method. Inhibition zones from 4 to 9 mm indicated that the modified nonwovens had antibacterial properties against Gram (+)—Staphylococcus aureus and Gram (?)—Klebsiella pneumoniae . Nonwovens were conditioned up to 12 months at relative humidity <5%, 50%, and 100% in desiccators and up to 6 months air‐conditioning system at relative humidity = 65%. Antimicrobial activity of the modified nonwovens was examined as a function of time and air humidity. Time of conditioning has strong influence on antibacterial activity, whereas the impact of the air humidity was negligible. All nonwovens had antibacterial properties even after 12 months of conditioning. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   
982.
In this paper cointegration and error correction models are used to explore the long run and short run behavior of personal consumption in Croatia as a function of income, house prices and total credit to households. The results of the analysis showed that income (approximated by net real wage), house price and total credits to households play an important role in determining personal consumption. Also, lagged values of house prices showed significant impact on consumption, suggesting house price persistence. The most likely factors driving the house price persistence may include expectations and idiosyncratic institutional characteristics like illiquid real estate markets, inadequate property rights protection, high transaction costs, and underdeveloped financial instruments.  相似文献   
983.
984.
Summary Let Abe a semisimple H*-algebra and let T: AAbe an additive mapping such that T(x n +1)<span lang=EN-US style='font-size:10.0pt;mso-ansi-language:EN-US'>=T(x)x n+x n T(x) holds for all xAand some integer n≥1. In this case Tis a left and a right centralizer.  相似文献   
985.
The aim of this paper is to study the asymptotic behavior of the solution of a convection–diffusion equation in perforated domains with oscillating velocity and a Robin boundary condition which describes the adsorption on the bord of the obstacles. Without any periodicity assumption, for a large range of perforated media and by mean of variational homogenization, we find the global behavior when the characteristic size ε of the perforations tends to zero. The homogenized model, is a convection–diffusion equation but with an extra term coming from the weak adsorption boundary condition. An example is presented to illustrate the methodology.  相似文献   
986.
We prove the existence of solutions of four-point boundary value problems under the assumption that f fulfils various combinations of sign conditions and no growth restrictions are imposed on f. In contrast to earlier works all our results are proved for the Carathéodory case.  相似文献   
987.
We consider semidiscrete approximations of parabolic boundary value problems based on an elliptic approximation by J. Nitsche, in which the approximating subspaces are not subject to any boundary conditions. Optimal Lp (L 2) error estimates are derived for both smooth and nonsmooth boundary data. The approach is

based on semigroup theory combined with the theory of singular integrals.  相似文献   

988.
989.
The polymerization of crystalline diacetylenes TS and DCH with different lattice structure was studied under high hydrostatic pressures (up to 4 kbar). It was shown that pressure increases the deformation of chain growing in monomer crystal. The features of such deformation depend on lattice structure that governs the influence of pressure on polymerization rate. We studied also polymerization of diacetylene HD crystals obtained in the pores of stretched polymer (PP). The field of polymer matrix influences the crystal state and the rate of polymerization. It was shown that the interaction of monomer crystals with the matrix leads to growth of more strained chains in these crystals.  相似文献   
990.
The precipitation temperature (Tpr) value of aqueous poly(dimethylamino-ethoxyacryloyl-propylsulphonate) (PDMAPS) solutions decreases with the rise of electric field intensity both in the absence and in the presence of a low molecular salt. This electrostimulated Tpr shift is explained qualitatively by means of the model taking into account both the dominating intermacromolecular dipole-dipole interaction and the dipole cluster formation.  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