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   1724篇
  免费   39篇
  国内免费   26篇
化学   1117篇
晶体学   20篇
力学   27篇
综合类   1篇
数学   342篇
物理学   282篇
  2023年   5篇
  2022年   32篇
  2021年   40篇
  2020年   25篇
  2019年   30篇
  2018年   28篇
  2017年   25篇
  2016年   56篇
  2015年   36篇
  2014年   54篇
  2013年   117篇
  2012年   99篇
  2011年   112篇
  2010年   79篇
  2009年   104篇
  2008年   100篇
  2007年   102篇
  2006年   99篇
  2005年   80篇
  2004年   78篇
  2003年   45篇
  2002年   61篇
  2001年   26篇
  2000年   33篇
  1999年   22篇
  1998年   19篇
  1997年   17篇
  1996年   21篇
  1995年   19篇
  1994年   8篇
  1993年   16篇
  1992年   14篇
  1991年   7篇
  1990年   19篇
  1989年   11篇
  1988年   5篇
  1987年   6篇
  1986年   8篇
  1985年   16篇
  1984年   17篇
  1983年   12篇
  1982年   15篇
  1981年   12篇
  1980年   11篇
  1979年   7篇
  1978年   6篇
  1977年   6篇
  1976年   7篇
  1973年   6篇
  1929年   4篇
排序方式: 共有1789条查询结果,搜索用时 15 毫秒
61.
Five chemical compounds, CuMoO4, Cu3Mo2O9, Cu2Mo3O10, Cu6Mo4O15, and Cu4?x Mo3O12 (0.10 ? x ? 0.40), were identified in the system Cu2OCuOMoO3 and characterized by DTA, X-ray powder patterns, ir spectra, and magnetic properties. Cupric molybdates CuMoO4 and Cu3Mo2O9 are stable in air up to 820 and 855°C, respectively, melting at these temperatures with simultaneous decomposition (oxygen loss). Congruent mp of cuprous molybdates Cu2Mo3O10 and Cu6Mo4O15, in argon, are 532 and 466°C, respectively. Nonstoichiometric phase Cu4?x Mo3O12 = Cu2+3Cu01?xMo6+3O12, melts in argon between 630 and 650°C depending on the value of x and at 525–530°C undergoes polymorphic transformation. Areas of coexistence of the above-mentioned phases are determined. The μeff of Cu2+ ions and θ values are: 1.80 B.M. and 28°K for CuMoO4, 1.71 B.M. and ? 12°K for Cu3Mo2O9, and 1.74 B.M. and ? 93°K for Cu4?xMo3O12. Below 200°K CuMoO4 becomes antiferromagnetic. Cu2Mo3O10 and Cu6Mo4O15 show weak temperature-independent paramagnetism.  相似文献   
62.
63.
64.
Labeled RNAs are invaluable probes for investigation of RNA function and localization. However, mRNA labeling remains challenging. Here, we developed an improved method for 3′-end labeling of in vitro transcribed RNAs. We synthesized novel adenosine 3′,5′-bisphosphate analogues modified at the N6 or C2 position of adenosine with an azide-containing linker, fluorescent label, or biotin and assessed these constructs as substrates for RNA labeling directly by T4 ligase or via postenzymatic strain-promoted alkyne-azide cycloaddition (SPAAC). All analogues were substrates for T4 RNA ligase. Analogues containing bulky fluorescent labels or biotin showed better overall labeling yields than postenzymatic SPAAC. We successfully labeled uncapped RNAs, NAD-capped RNAs, and 5′-fluorescently labeled m7Gp3Am-capped mRNAs. The obtained highly homogenous dually labeled mRNA was translationally active and enabled fluorescence-based monitoring of decapping. This method will facilitate the use of various functionalized mRNA-based probes.  相似文献   
65.
66.
67.
68.
Journal of Solution Chemistry - Recently ionic liquids have been considered as prospective substances for application as heat transfer fluids, which requires accurate knowledge of their thermal...  相似文献   
69.
Amorphous silicon oxycarbide (a-SiOC:H) films produced by remote plasma RPCVD from diethoxymethylsilane (DEMS) were characterized in terms of their basic properties related to the coatings deposited using conventional plasma enhanced PECVD method. The effect of substrate temperature (TS) on the growth rate, chemical composition, structure, and properties of resulting a-SiOC:H films is reported. Film growth is an adsorption-controlled process, wherein two mechanisms can be distinguished with a transition at about TS=70°C. Depending on the temperature, films of different nature can be obtained, from polymer-like to highly crosslinked material with C-Si-O network. The chemical structure of a-SiOC:H films was characterized by FTIR, 13C and 29Si solid-state NMR, and X-ray photoelectron spectroscopes. The a-SiOC:H films were also characterized in terms of their density, refractive index, surface morphology, conformality of coverage, hardness, adhesion to a substrate, and friction coefficient. The films were found to be morphologically homogeneous materials exhibiting good conformality of coverage and small surface roughness. Their refractive index exhibits anomalous effect revealing a minimum value at TS=125°C. Due to their exceptional physical properties a-SiOC:H films produced by RPCVD from DEMS precursor seems to be useful as potential dielectric materials or coatings for various encapsulation applications.  相似文献   
70.
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