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   10894篇
  免费   1942篇
  国内免费   1311篇
化学   8104篇
晶体学   69篇
力学   679篇
综合类   82篇
数学   1091篇
物理学   4122篇
  2024年   27篇
  2023年   279篇
  2022年   333篇
  2021年   403篇
  2020年   501篇
  2019年   437篇
  2018年   365篇
  2017年   301篇
  2016年   528篇
  2015年   450篇
  2014年   541篇
  2013年   790篇
  2012年   1005篇
  2011年   1026篇
  2010年   666篇
  2009年   661篇
  2008年   757篇
  2007年   660篇
  2006年   578篇
  2005年   494篇
  2004年   382篇
  2003年   340篇
  2002年   279篇
  2001年   220篇
  2000年   224篇
  1999年   267篇
  1998年   218篇
  1997年   200篇
  1996年   222篇
  1995年   181篇
  1994年   146篇
  1993年   128篇
  1992年   111篇
  1991年   77篇
  1990年   86篇
  1989年   59篇
  1988年   49篇
  1987年   46篇
  1986年   30篇
  1985年   28篇
  1984年   14篇
  1983年   9篇
  1982年   13篇
  1981年   8篇
  1980年   5篇
  1979年   2篇
  1957年   1篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
121.
脱蜡剂DF-1是一种含多种有机成分的碳氢化合物,经气相色谱-红外光谱联用分析后,确定了这些组分的组成与含量。  相似文献   
122.
煤焦在CO2气化过程中微孔结构的变化   总被引:1,自引:0,他引:1  
  相似文献   
123.
显微组分焦样的CO2气化动力学和表面变化   总被引:7,自引:0,他引:7  
  相似文献   
124.
125.
The Cu-Mo/ZSM-5 catalysts with different Cu/Mo ratios were prepared by wet impregnation method, and their catalytic performance for selective catalytic reduction of NOx was studied. The results showed that Cu-Mo/ZSM-5 is a very effective catalyst for NOx catalytic reduction with ammonia, especially when Cu/Mo molar ratio is about 1.5. It not only exhibited the extremely high catalytic activity, but also showed good stability for 02. The bulk phase structure of Cu-Mo/ZSM-5 catalysts was determined by XRD technique, and the results indicated that there is a maximum dispersion for Cu species when Cu/Mo molar ratio is 1.5, and an interaction between Cu and Mo along with HZSM-5 may be present in Cu-Mo/ZSM-5, which may possibly result in a special structure favorable for the catalytic reduction of NOx over Cu-Mo/ZSM-5 catalyst.  相似文献   
126.
Nonaqueous capillary electrophoretic (NACE) method for the separation of nine structurally similar chiral anticholinergic drugs was developed. The eight drug enantiomers were separated on baseline within 18 min using 20mM phosphoric acid and 10 mM NaOH, containing 10 mM heptakis(2,3-dimethyl-6-sulfato)-4beta-cyclodextrin (HDMS-beta-CD) in methanol. The results were compared with those obtained in the high performance liquid chromatography system.  相似文献   
127.
Three new 8-hydroxyquinoline derivatives, i.e. 5-[(4-styryl-benzylidene)-amino]-quinolin-8-ol (1), 5-[(4-bromo-2-fluoro-benzylidene)-amino]-quinoline-8-ol (2) and 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol (3), and their metallic complexes were synthesized and identified by ultraviolet-visible (UV-Vis), 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectrometer (FTIR), mass spectrometry (MS) spectra and elemental analyses. Their fluorescence properties were studied by photoluminescence, which indicated that the luminescence wavelength of 5-and 2-substitued-8-hydroxyquinoline derivatives shifted to red in comparison with that of 8-hydroxyquinoline. Meanwhile, the fluorescence lifetime of 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol and its zinc complex showed long lifetime in benzene solution. __________ Translated from Chinese Journal of Organic Chemistry, 2007, 27(3): 402–408 [译自: 有机化学]  相似文献   
128.
CdSe/ZnS-labeled carboxymethyl chitosan as a bioprobe for live cell imaging   总被引:2,自引:0,他引:2  
A simple and convenient method for the construction of CdSe/ZnS-labeled polysaccharides as bioprobes were developed, which are highly biocompatible and photostable, and have been proven to be suitable for live cell imaging.  相似文献   
129.
三(2-苯并咪唑亚甲基)胺硝酸镍(Ⅱ)配合物的合成及结构   总被引:5,自引:0,他引:5  
三(2-苯并咪唑亚甲基)胺简称NTB与Ni(Ⅱ)的硝酸盐形成配合物C28H35N9O9S2Ni。本文报道其合成,红外光谱及晶体结构。该化合物为三斜晶系,空间P1↑-,a=9.650(3),b=12.716(2),c=14.436A,α=11.46(2),β=91.66(3),γ=97.55(2)°,V=1718(2)A^3,Z=2,F(000)=793,Dc=1.48g/cm^3,Mr=764.1  相似文献   
130.
The harmonic vibrational force fields and the IR spectrum of XSO2NCO (X= F, C1) molecules have been studied usingab initio HF/SCF method with the 6-31G’ basis set. Theab initio harmonic force fields are scaled empirically using the scaled quantum mechanical (SQM) method of Pulay. A set of scale factors are optimized by the least-squares fitting to the experimental frequencies of FSO2NCO and then are transferred to CISO2NCO to give ana priori prediction of its fundamental frequencies. The average deviations between the theoretical frequencies and the experimental values for FSO2NCO and C1SO2NCO are 3 and 5 cm-1, respectively. The assignments of the fundamentals for these two molecules are also made atcording to the potential energy distributions and theab initio IR intensities Project supported by the National Natural Science Foundation of China (Grant No. 29673029)  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