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   98759篇
  免费   5725篇
  国内免费   4624篇
化学   56230篇
晶体学   1331篇
力学   5587篇
综合类   322篇
数学   11833篇
物理学   33805篇
  2023年   749篇
  2022年   1711篇
  2021年   2053篇
  2020年   2313篇
  2019年   2507篇
  2018年   2893篇
  2017年   2824篇
  2016年   3491篇
  2015年   2410篇
  2014年   3479篇
  2013年   4918篇
  2012年   5061篇
  2011年   5362篇
  2010年   4252篇
  2009年   4258篇
  2008年   4454篇
  2007年   4173篇
  2006年   3805篇
  2005年   3375篇
  2004年   3037篇
  2003年   2712篇
  2002年   2828篇
  2001年   2551篇
  2000年   1987篇
  1999年   1601篇
  1998年   1534篇
  1997年   1332篇
  1996年   1293篇
  1995年   1077篇
  1994年   1157篇
  1993年   1096篇
  1992年   1062篇
  1991年   1124篇
  1990年   1118篇
  1989年   1039篇
  1988年   917篇
  1987年   914篇
  1986年   881篇
  1985年   921篇
  1984年   915篇
  1983年   822篇
  1982年   800篇
  1979年   801篇
  1978年   812篇
  1977年   806篇
  1976年   919篇
  1975年   812篇
  1974年   844篇
  1973年   847篇
  1972年   752篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Summary Pust' Ej (j =1,2) - lokal'no vypuklye prostranstva funktsii, odnoznachnykh i lokal'no analiticheskikh na nekotorom mnozhestve Q ⊂ℂ. Pust', dalee, m(E1,E2) - mnozhestvo vsekh mul'tiplikatorov pary E1, E2 i L (E1, E2) sovokupnost' vsekh lineinykh operatorov, deistvuyushchikh iz E1 v E2. V stat'e e pri opredelennykh predpolozheniyakh poluchen kriterii predstavleniya operatora T iz L (E1, E2), kommutiruyushchego s fiksirovannym elementom a m(E1,E1) ∩m(E2,E2), v kanonicheskoi forme Ty = b · y, gde bm(E1,E2). Obsuzhdayut·sya predpolozheniya, pri kotorykh poluchen kriterii, i privodyat·sya primery, pokazyvayushchie ikh sushchestvennost'.  相似文献   
992.
We prove analogs of the Telyakovskii-Pochuev criteria for multipliers of uniform convergence and of convergence in the integral metric for multiplicative systems with bounded generating sequence.  相似文献   
993.
Two novel dithienylethenes with ferrocene units were synthesized by Wittig reaction. The structure of 2a has been established by X‐ray diffraction studies. They could reversibly interconvert between two thermally stable forms, an open and a closed one, using light of different wavelengths as triggers. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
994.
The magnetic and magnetoelastic parameters of Fe64Co21B15 and Fe81.5B13.5Si3C2 amorphous ferromagnetic alloys treated by direct electric current in air are studied as functions of the applied magnetic field and current density. The samples of the alloy have the form of narrow strips with different lengths. It is found that the magnetoelastic parameters of the dc-treated alloys depend on the magnetic field in a qualitatively different way. From the behavior of the magnetic and magnetoelastic parameters of the alloys in the magnetic field a model of magnetization nonuniform distribution in amorphous ferromagnetic alloys subjected to dc treatment is proposed.  相似文献   
995.
A direct (without sample pretreatment) atomic-absorption method of V and Ni determination in oil with electrothermal atomization and Zeeman correction of background was developed.  相似文献   
996.
The possibility of raising the static exchange capacity of strongly acidic ion-exchange materials produced by grafting of styrene onto polypropylene fibers, with the subsequent sulfonation of the products synthesized, was analyzed. The chemical and osmotic stabilities of the sulfonic cation exchangers obtained and their frost resistance in freeze-thaw cycles were studied.  相似文献   
997.
Conformationally heterogeneous 2-substituted 1,3-dithiacyclohept-5-enes (R = Ph, Me, t-Bu), which exist in solution as chair and boat conformers, react with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate with high exo-diastereoselectivity: only the chair conformer is involved. The steric structure of 4-methyl-3,5-dithia-9,10-diazabicyclo[5.4.0]undeca-7,10-diene was determined by X-ray analysis. Its crystal packing and supramolecular structure were also analyzed.  相似文献   
998.
Dioxirane generated in situ by reaction of chiral 1,2:4,5-di-O-isopropylidene-D-erythro-hexo-2,4-diulo-2,6-pyranose with Oxone oxidizes prochiral sulfides to the corresponding sulfoxides with an enantiomeric excess of 2 to 25%.  相似文献   
999.
The properties of Mn-doped GaAs layers grown by laser deposition were investigated with measurements of Hall effect and magneto-optical Kerr effect (MOKE). The electrical and magnetic parameters of the layers were defined by growth temperature and quantity of sputtered Mn. It was shown that room-temperature ferromagnetism is revealed by MOKE and, after ruby laser 25 ns pulse annealing, by Hall effect measurements.  相似文献   
1000.
Retraction: The following article from Biomedical Chromatography, “Determination of scutellarin isomer, a predominant metabolite of scutellarin, in human plasma by HPLC/tandem mass spectrometry and its application to the pharmacokinetic study in Chinese healthy volunteers” by Chun‐hua Xia, Yu‐qing Xiong, and Guang‐ji Wang, published online on 21 June 2007 in Wiley Interscience (www.interscience.wiley.com/journal/bmc), has been retracted at the authors' request.  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