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   2546篇
  免费   402篇
  国内免费   316篇
化学   1741篇
晶体学   69篇
力学   183篇
综合类   46篇
数学   363篇
物理学   862篇
  2024年   12篇
  2023年   78篇
  2022年   136篇
  2021年   113篇
  2020年   192篇
  2019年   146篇
  2018年   121篇
  2017年   113篇
  2016年   139篇
  2015年   141篇
  2014年   149篇
  2013年   164篇
  2012年   196篇
  2011年   164篇
  2010年   153篇
  2009年   149篇
  2008年   151篇
  2007年   122篇
  2006年   118篇
  2005年   100篇
  2004年   76篇
  2003年   67篇
  2002年   77篇
  2001年   46篇
  2000年   34篇
  1999年   30篇
  1998年   28篇
  1997年   32篇
  1996年   38篇
  1995年   28篇
  1994年   11篇
  1993年   17篇
  1992年   18篇
  1991年   22篇
  1990年   11篇
  1989年   10篇
  1988年   8篇
  1986年   7篇
  1985年   4篇
  1984年   4篇
  1983年   5篇
  1982年   6篇
  1981年   4篇
  1980年   5篇
  1979年   5篇
  1978年   4篇
  1977年   4篇
  1976年   3篇
  1974年   1篇
  1935年   1篇
排序方式: 共有3264条查询结果,搜索用时 0 毫秒
141.
In this article, supramolecular silicone elastomers with self‐healing function were first prepared by simple and controllable “salt‐forming vulcanization” of polyaminopropylmethylsiloxane with acids. Their structures and micrographs were verified by Fourier transform infrared spectra, Small‐angle X‐ray scattering experiments and atomic force microscope. The experimental results showed that the ion‐association complexes were formed during vulcanization, and the obtained elastomers displayed self‐healing and good mechanical properties even if the cross‐linking agent was excessed. The thermogravimetric analysis showed that the elastomers crosslinked by inorganic acid were stable under high temperature. Unexpectedly, bionic structures were observed in the elastomers, which further changed the hydrophobicity of the surfaces of the elastomers physically. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 903–911  相似文献   
142.
<正>Cr ion implantations in glass with the different doses of D=1.493×10~(17) and 4.976×10~(17) ion/cm~2 are obtained by metal vapor vacuum arc(MEVVA).The effects of the different Cr ion implanted doses on terahertz(THz) transmission property are analyzed from THz time-domain spectroscopy.The results show that the more the Cr ion implanted dose in the micro-area implantation glasses,the larger the THz transmission except the larger absorption at 0.24 THz.This is an effect attributed to the coupling of plasmas on both the implantation and the implantation affected zones of the Cr ion implantation glass.  相似文献   
143.
Inositol phosphates regulate important biological functions in intracellular signal transduction events. Phosphonates, because of the stability towards the action of phosphatases, were extensively used to replace phosphates. We herein reported the synthesis of inositol phosphonate analogues using myo-inositol as the starting material, and found that two of phosphonate analogues exhibited relative good cytotoxic activity against non-small cell lung cancer (NSCLC) cell line A549.  相似文献   
144.
145.
The structure of sialic acid on living cells can be modulated by metabolism of unnatural biosynthetic precursors. Here we investigate the conversion of a panel of azide-functionalized mannosamine and glucosamine derivatives into cell-surface sialosides. A key tool in this study is the Staudinger ligation, a highly selective reaction between modified triarylphosphines and azides that produces an amide-linked product. A preliminary study of the mechanism of this reaction, and refined conditions for its in vivo execution, are reported. The reaction provided a means to label the glycoconjugate-bound azidosugars with biochemical probes. Finally, we demonstrate that the cell-surface Staudinger ligation is compatible with hydrazone formation from metabolically introduced ketones. These two strategies provide a means to selectively modify cell-surface glycans with exogenous probes.  相似文献   
146.
A series of well-defined enantiopure 1,1'-binaphthyl-based oligomers linked through their 6,6'-positions, ranging from quaternaphthol to decanaphthol, have been synthesized by Suzuki and Stille coupling reactions. These novel oligonaphthyls have been characterized by (1)H and (13)C[(1)H] NMR spectroscopy and high-resolution mass spectrometry. A combination of X-ray structural and CD studies suggests that these oligonaphthyls adopt zigzag but not helical conformations. As the chain length increases, the compounds show enhanced fluorescence. The fluorescence intensity of oligonaphthols is almost 2 orders of magnitude higher than that of 1,1'-bi-2-naphthol and can be effectively and enantioselectively quenched with trans-1,2-diaminocyclohexane with an enantioselectivity factor of 1.24. The present work thus demonstrates the potential of constructing chiral sensory materials based on well-defined enantiopure oligonaphthols.  相似文献   
147.
A zeolite-based microengineered reactor was fabricated and tested for 1-pentene epoxidation over titanium silicalite-1 (TS-1) catalyst, which has been selectively incorporated within the microreactor channel using a new synthesis procedure.  相似文献   
148.
149.
150.
StudyoftheLaserLightEffectonImprovingSheepSemenQuality¥YUEWenbin;LIUWenzhong(DepartmentofAnimalShanxiAgricultutalUniversity,S...  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