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   2725篇
  免费   98篇
  国内免费   1篇
化学   1779篇
晶体学   20篇
力学   94篇
数学   380篇
物理学   551篇
  2023年   25篇
  2022年   29篇
  2021年   54篇
  2020年   58篇
  2019年   52篇
  2018年   80篇
  2017年   74篇
  2016年   156篇
  2015年   112篇
  2014年   125篇
  2013年   210篇
  2012年   200篇
  2011年   233篇
  2010年   139篇
  2009年   92篇
  2008年   195篇
  2007年   177篇
  2006年   134篇
  2005年   98篇
  2004年   78篇
  2003年   81篇
  2002年   55篇
  2001年   35篇
  2000年   32篇
  1999年   26篇
  1998年   20篇
  1997年   15篇
  1996年   16篇
  1995年   16篇
  1994年   22篇
  1993年   15篇
  1992年   12篇
  1991年   14篇
  1990年   6篇
  1989年   10篇
  1988年   4篇
  1987年   5篇
  1986年   8篇
  1985年   13篇
  1984年   13篇
  1983年   7篇
  1982年   7篇
  1981年   5篇
  1980年   11篇
  1979年   8篇
  1978年   5篇
  1976年   6篇
  1975年   4篇
  1974年   6篇
  1973年   7篇
排序方式: 共有2824条查询结果,搜索用时 15 毫秒
151.
Treatment of polluted soil is one of the priorities in the search of a more sustainable planet. Electrochemically assisted soil remediation has been considered a good option for removing organic contaminants contained in soil, including the removal of volatile organic compounds, associated with gaseous streams produced during the treatment. Also, recently, electrochemical gas treatment technologies have been appointed as promising for the treatment of volatile organic compounds. In this work, we review the current opinion about the most recent studies in both areas. The first section focuses on the production of gaseous compounds during soil remediation by conventional and electrochemical systems. The second section describes the recent progress in the integration of adsorption and absorption with electrochemical processes. Finally, we discuss the holistic application of assisted electrochemical technologies in soil remediation, considering also emerging processes recently published in the literature.  相似文献   
152.
A number of polymer dispersed liquid crystal (PDLC) films based on dimethacrylate monomers were synthesised by polymer-induced phase separation (PIPS) using polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (TX-100) as an additive up to total solution weight of 10% aiming to modify the initial anchorage force of the liquid crystal (LC) molecules to the polymeric matrix. The effects of the addition of this additive to the PDLC films were studied resorting to electro-optical studies. Using a fitting model, several parameters were correlated such as the permanent memory effect (PME), the voltage required to achieve 90% of maximum transmittance (E90), the average elastic constant (K) and the rotational viscosity of the director (γ). The use of TX-100 results on an increase on the PME and γ, and decrease on the E90 and K.  相似文献   
153.
154.
This work reports for the first time the nutritional profile and antioxidant potential of the edible sea cucumber Holothuria arguinensis from the North-eastern Atlantic. H. arguinensis has high levels of protein, with the amino acids profile dominated by alanine, glycine and proline and low lysine/arginine ratios. Its carbohydrate and energetic contents are also low as well as the total lipid levels, although its lipid profile is rich in polyunsaturated fatty acids (PUFA), especially arachidonic, eicosapentaenoic and docosahexaenoic acids. In addition, H. arguinensis has high levels of calcium. The water and ethanol extracts show ability to scavenge free radicals and to chelate copper and iron ions. Our results indicate that H. arguinensis has a balanced nutritional quality suitable for human consumption. In addition, it contains compounds with antioxidant potential; thus its intake can contribute for a healthy and well-balanced diet.  相似文献   
155.
156.
Journal of Solid State Electrochemistry - This paper reports a new platform for oligonucleotide hybridization, prepared by electropolymerization of 3-hydroxyphenylacetic acid onto gold electrode...  相似文献   
157.
158.
A different approach to enzyme kinetics stressing the cyclic nature of the catalytic process is presented. The time-dependence of the substrate concentration is derived in a simple way not invoking the quasi-steady-state approximation. According to this approach the turnover rate can be written as the ratio of two parameters with a direct meaning: enzyme efficiency and average cycle duration. Real kinetic data for two enzyme-substrate pairs is used to show that the enzyme kinetic efficiency is best measured by the turnover rate.  相似文献   
159.
A novel sapphyrin derivative was obtained from the reaction between a free‐base sapphyrin and dimethyl acetylenedicarboxylate (DMAD). The formation of the new compound involved a double aza‐Michael addition of two pyrrolic NH groups to a DMAD molecule, with the formation of a disubstituted ethano bridge. The NMR spectral data reveal a product with an unsymmetrical structure; DFT calculations provided support for a structure in which the ethano bridge links two adjacent pyrrole units. The present study provides a seemingly unprecedented example of an N,N′‐dinucleophile reacting with DMAD to form a heterocyclic compound in which the two N‐atoms are linked to the two sp3 carbon atoms derived from a substituted acetylene.  相似文献   
160.
Quasiclassical trajectories have been run to study the fundamental one‐quantum vibrational transition formed from collisions of ground‐state nitric oxide with atomic oxygen at temperatures of 500, 750, and 1000 K. Two adiabatic potential energy surfaces of different symmetry (2A′ and 2A″ of NO2) have been utilized. The rate constant for the title process is given along with the rotational distributions, and the results shown to corroborate previous atmospheric models that describe the nascent state by a Maxwell–Boltzmann distribution at the local temperature. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 345–352, 2011  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