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   292篇
  免费   12篇
  国内免费   19篇
化学   259篇
晶体学   3篇
力学   5篇
数学   13篇
物理学   43篇
  2024年   3篇
  2023年   2篇
  2022年   9篇
  2021年   18篇
  2020年   10篇
  2019年   16篇
  2018年   9篇
  2017年   12篇
  2016年   12篇
  2015年   9篇
  2014年   13篇
  2013年   25篇
  2012年   20篇
  2011年   24篇
  2010年   11篇
  2009年   21篇
  2008年   13篇
  2007年   11篇
  2006年   13篇
  2005年   13篇
  2004年   14篇
  2003年   9篇
  2002年   9篇
  2001年   5篇
  2000年   2篇
  1999年   1篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1989年   1篇
  1983年   1篇
  1978年   1篇
  1977年   2篇
  1973年   1篇
  1970年   3篇
  1969年   1篇
  1967年   2篇
  1966年   2篇
  1965年   1篇
  1963年   1篇
排序方式: 共有323条查询结果,搜索用时 15 毫秒
41.
42.
43.
A phosphorus-containing monomer(10-oxo-10-hydro-9-oxa-10λ~5-phosphaphenanthrene-10-yl)-methyl acrylate(M_1) was copolymerized with styrene to give a potential flame retardant copolymer of high thermal stability.The structures of monomer and copolymer were characterized by FT-IR and ~1H NMR measurements.The reactivity ratios for free-radical of the monomer(M_1) and styrene(M_2) were studied.The calculated results are as follows:r_1=0.225,r_2=0.503;Q_1=0.413,e_1= 0.476;azeotropic point = 0.37.TGA and DTG c...  相似文献   
44.
The kinetics of the liquid-phase hydrogenation of cyclodienes with various structures (endo-tricyclo[ 5.2.1.02,6]decadiene-3,8 and cis,cis-1,5-cyclooctadiene) by hydrogen over a finely dispersed 1%Pd/C catalyst at atmospheric pressure has been studied. The catalyst provides the possibility for successive saturation of the double bonds of the dienes. The reactivities of the cyclodienes determined by their electron-donating properties have been compared. The solvent nature is the determining factor in the ratio of hydrogen absorption rates in the case of successive saturation of the double bonds of the hydrocarbons. The hydrogenation kinetics of cyclic dienes, including dicyclopentadiene, can be modeled using the Langmuir–Hinshelwood equation when the process is carried out in a perfectly mixed flow reactor.  相似文献   
45.
We demonstrate the feasibility of fabrication of semiconducting nanowires (quantum dots) using F-actin as a template. Three different approaches of assembling quantum dots into nanowires are described. The nanowires were characterized by fluorescence microscopy.  相似文献   
46.
47.
A sulfate-encapsulating complex, [Cu(1)L(6)]·3[Cu(2)L(2)(DMF)(4)](SO(4))(4) (1, L = N-(1-naphthyl)-N'-(3-pyridyl)urea) is synthesized in which two C(3)-clefts of the octahedral complexes interdigitate to form a cavity to encapsulate the sulfate ion by six urea groups.  相似文献   
48.
Pectolinarin and linarin are two major flavone O-glycosides of Cirsium japonicum, which has been used for thousands of years in traditional Chinese medicine. Pharmacological research on pectolinarin and linarin is meaningful and necessary. Here, a process for the purification of pectolinarin and linarin from C. japonicum was established using macroporous resin enrichment followed by prep-HPLC separation. The results show the purity of pectolinarin and linarin reached 97.39% and 96.65%, respectively. The in vitro bioactivities result shows the ORAC values of pectolinarin and linarin are 4543 and 1441 µmol TE/g, respectively, meanwhile their inhibition rate of BSA-MGO-derived AGEs is 63.58% and 19.31% at 2 mg/mL, which is 56.03% and 30.73% in the BSA-fructose system, respectively. The COX-2 inhibition rate at 50 µg/mL of linarin and pectolinarin reached 55.35% and 40.40%, respectively. Furthermore, the in vivo bioassay combining of histopathologic evaluation and biochemical analysis of liver glutamic oxaloacetic transaminase, serum creatinine and TNF-α show pectolinarin can alleviate lipopolysaccharide (LPS)-induced acute liver and kidney injury in mice. Metabolomics analysis shows that pectolinarin attenuates LPS-challenged liver and kidney stress through regulating the arachidonic acid metabolism and glutathione synthesis pathways. Collectively, our work presents a solid process for pectolinarin and linarin purification and has discovered a promising natural therapeutic agent—pectolinarin.  相似文献   
49.
50.
A humidity controlled inlet system was developed to measure the hygroscopic growth of aerosol scattering coefficient in conjunction with nephelometry at an urban site of Chinese Academy of Meteorological Sciences (CAMS) in Beijing and a rural site at Shangdianzi Regional Background Air Pollution Monitoring Station (SDZ) outside Beijing during winter, from December 2005 to January 2006. Measurements were carried out at a wavelength of 525 nm with an Ecotech M9003 nephelometer. The hygroscopic growth function (or factor) of the aerosol scattering coefficientf(RH) increased continuously with increasing relative humidity (RH) and showed no obvious "step-like" deliquescent behavior at both sites during the experiment. The average growth factorf(RH) at the SDZ site could reach 1.5 when RH increased from less than 40% to 92%, and to 2.1 at the CAMS site when RH increased from less than 40% to 93%. The average hygroscopic growth factor at a relative humidity of 80%, f(RH=80±1%), was found to be about 1.26±0.15 at CAMS and 1.24±0.11 at SDZ. Further analysis indicated that under relatively polluted conditions, the average hygroscopic growth factor was higher at the CAMS site than that at the SDZ site. However, under relatively clean air conditions, the difference between the two sites was small, showing a hygroscopic growth behavior similar to those of burning biomass or blowing dust. These results reflected the different characteristics of aerosol types at the two sites.  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