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   329994篇
  免费   3103篇
  国内免费   929篇
化学   164798篇
晶体学   5416篇
力学   15548篇
综合类   7篇
数学   38478篇
物理学   109779篇
  2021年   3132篇
  2020年   3339篇
  2019年   3761篇
  2018年   5198篇
  2017年   5439篇
  2016年   7368篇
  2015年   4139篇
  2014年   7028篇
  2013年   15906篇
  2012年   12377篇
  2011年   14826篇
  2010年   11012篇
  2009年   10913篇
  2008年   13233篇
  2007年   13194篇
  2006年   12137篇
  2005年   10520篇
  2004年   9833篇
  2003年   8686篇
  2002年   8672篇
  2001年   10393篇
  2000年   7655篇
  1999年   5967篇
  1998年   4973篇
  1997年   4811篇
  1996年   4479篇
  1995年   3864篇
  1994年   3820篇
  1993年   3701篇
  1992年   4096篇
  1991年   4306篇
  1990年   4096篇
  1989年   4009篇
  1988年   3779篇
  1987年   3917篇
  1986年   3683篇
  1985年   4630篇
  1984年   4681篇
  1983年   3885篇
  1982年   3973篇
  1981年   3697篇
  1980年   3647篇
  1979年   3913篇
  1978年   3901篇
  1977年   3906篇
  1976年   3879篇
  1975年   3675篇
  1974年   3615篇
  1973年   3650篇
  1972年   2603篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
271.
Moscow University Chemistry Bulletin - A piezoactive nanofiber composite PVDF film with TiO2 nanoparticles included in it was synthesized by electrospinning. The composition, morphology and...  相似文献   
272.
Kinetics and Catalysis - It has been established that the reactions of sulfur dioxide oxidation and carbon dioxide conversion take place in aqueous suspensions of calcium fluoride at room...  相似文献   
273.
Journal of Structural Chemistry - Two hydrogen-bonded organic frameworks of the composition [((CH3)2NH2)3.5(Ni-H4.5TPPP)]·DMF·H2O (1) and [((CH3)2NH2)4(Ni-H4TPPP)(H2O)3]·DMF·H2O...  相似文献   
274.
Journal of Structural Chemistry - A series of MnOx–ZrO2 catalysts is prepared by coprecipitation with variation of the calcinationtemperature from 400 °C to...  相似文献   
275.
Saraca asoca is an IUCN red-listed tree species that extensively famous in the Ayurvedic medicine field. Saraca asoca (Roxb.) de Wilde belongs to the family Fabaceae, has been used to treat various gynecological disorders, bacterial infections, worm infestations, haemmorhagic dysentery, uterine pain, skin diseases, cancer, circulatory, cardiovascular disorders, and many others. All parts of the Saraca asoca have medicinal values. Numerous antioxidant compounds like flavonoids, catechin, beta-sitosterol, lignin glycosides are present in the bark, leaf, and flower of Saraca asoca plant, which help to stabilize free radicals molecules that are associated with the development of cancer conditions. Currently in the cancer research study field new and more effective modes of natural therapies are recently being analyzed. Traditional medicines have been used for their preventative role against various diseases in the human population. Plant based therapy for cancer prevention is becoming more demanding due to its various unique properties such as natural chemical composition, less expensiveness, naturally available., easily orally administrable, significant chemo-protective activities, nontoxic to normal cells in the body, less side effects compared to other synthetic chemotherapeutic drugs. The chemotherapeutic drugs will be harmful to both cancer and normal cells. Additionally, some common side effects or health consequences like vomiting, nausea, bleeding, hair fall, alopecia, hyperuricemia, thrombocytopenia, bone marrow depression, mucositis are very common after chemotherapeutic drug treatment in cancer. This review paper summarizes the evidences which agree with the fact that flavonoids and other phenolic compounds in Saraca asoca plant possess significant antioxidant activity and an efficient chemopreventive characteristic against different types of cancer. This paper reviews the anticancer activities of Saraca asoca bark and flower and discusses the potential preventive roles of phenolic and flavonoids compounds, present in bark and flower of Saraca asoca in the cancer treatment process.  相似文献   
276.
Chen  C. Y.  Kao  C. L.  Tsai  Y. S.  Wu  M. D.  Cheng  M. J. 《Chemistry of Natural Compounds》2022,58(5):923-925
Chemistry of Natural Compounds -  相似文献   
277.
Chemistry of Natural Compounds - Ursane-type triterpenoids containing functionalized heterocyclic substituents were chemically modified. Aminomethylation of ursane hybrids with 1,3,4-oxadiazole-...  相似文献   
278.

This paper describes the method of wet chemistry used for hydrophobization of coarse calico surface. It was found that hydrophobicity of coarse calico surface is achieved by the formation of aluminum oxide on the surface. An experimental plan was drawn up according to the Taguchi method. The effect of soap solution temperature, aluminum chloride solution concentration, sample treatment time in aluminum chloride solution and heat treatment temperature on water absorption, contact angle, capillary absorption and calico moisture content was studied. The dependencies of hygroscopic properties on the process parameters were obtained. Capillary absorption and water absorption of the test samples increased with increasing concentration of aluminum chloride solution. An increase in the processing time of coarse calico samples in an aluminum chloride solution leads to a decrease in the hydrophobicity of the samples. The characteristics of the dependencies of hygroscopic properties on the temperature of heat treatment and the temperature of the soap solution are similar.

  相似文献   
279.
280.
This study presents a quantitative evaluation of the influence of radiation upon the parameters of a long induced discharge in argon at atmospheric pressure. Radiation heat transfer in the optically transparent tin plasma layers with thickness of the order of several centimeters) and reabsorption spectral intervals is examined. Experimental error produced by inaccurate knowledge of the transfer and optical characteristics of the plasma is evaluated. The effect of convection on radial temperature profile is evaluated.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiztki, No. 6, pp. 35–43, November–December, 1971.  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