全文获取类型
收费全文 | 421篇 |
免费 | 18篇 |
专业分类
化学 | 340篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 16篇 |
物理学 | 78篇 |
出版年
2023年 | 4篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 21篇 |
2012年 | 23篇 |
2011年 | 34篇 |
2010年 | 26篇 |
2009年 | 15篇 |
2008年 | 17篇 |
2007年 | 27篇 |
2006年 | 21篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 16篇 |
2002年 | 16篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1971年 | 2篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有439条查询结果,搜索用时 0 毫秒
11.
An HPLC assay of hydroxyl radicals by the hydroxylation reaction of terephthalic acid 总被引:2,自引:0,他引:2
Linxiang L Abe Y Nagasawa Y Kudo R Usui N Imai K Mashino T Mochizuki M Miyata N 《Biomedical chromatography : BMC》2004,18(7):470-474
An HPLC assay for hydroxyl radicals is described. The hydroxyl radical was trapped by terephthalic acid (non-fluorescent), and 2-hydroxyl terephthalic acid (fluorescent) was quantitated by HPLC-fluorescence detection. At a terephthalic acid concentration of 4.25 mmol/L, the hydroxyl radical formed in the Fenton reaction was successfully assayed in the concentration range of hydrogen peroxide of 2.5-50 micro mol/L, where the concentration of Fe(II) was 50 micro mol/L. The fluorescence of 2-hydroxy terephthalate was stable at 24 h, and its detection limit by this method was 5 nmol/L (100 fmol). 相似文献
12.
Chiral urea compounds 10a-g were synthesized as catalysts for conjugate addition of pyrrolidine (2) to gamma-crotonolactone (3). In the presence of a catalytic amount of the chiral ureas, this hetero-Michael reaction was greatly accelerated. Asymmetric induction was observed with the catalysts 10e, 10f, and 10g. 相似文献
13.
Allylation and propargylation of glyoxylic oxime ether in the presence of a catalytic amount of palladium(0) complex and indium(I) iodide were studied. Excellent diastereoselectivities in allylation were achieved in the presence of water, although low diastereoselectivities were observed in the absence of water. Propargylation of glyoxylic oxime ether proceeded with good diastereoselectivities in the presence of LiBr or LiCl. 相似文献
14.
15.
Visualization of tumor-specific protein biomarkers on cell membranes has the potential to contribute greatly to basic biological research and therapeutic applications. We recently reported a unique supramolecular strategy for specific protein detection using self-assembling fluorescent nanoprobes consisting of a hydrophilic protein ligand and a hydrophobic BODIPY fluorophore in test tube settings. This method is based on recognition-driven disassembly of the nanoprobes, which induces a clear turn-on fluorescent signal. In the present study, we have successfully extended the range of applicable fluorophores to the more hydrophilic ones such as fluorescein or rhodamine by introducing a hydrophobic module near the fluorophore. Increasing the range of available fluorophores allowed selective imaging of membrane-bound proteins under live cell conditions. That is, overexpressed folate receptor (FR) or hypoxia-inducible membrane-bound carbonic anhydrases (CA) on live cell surfaces as cancer-specific biomarkers were fluorescently visualized using the designed supramolecular nanoprobes in the turn-on manner. Moreover, a cell-based inhibitor-assay platform for CA on a live cell surface was constructed, highlighting the potential applicability of the self-assembling turn-on probes. 相似文献
16.
Masatoshi Oue Akira Ishigaki Keiichi Kimura Yousuke Matsui Toshiyuki Shono 《Journal of polymer science. Part A, Polymer chemistry》1985,23(7):2033-2042
Poly- and bis(thiacrown ether) derivatives in which some oxygen atoms of benzocrown ether moiety are replaced by sulfur atoms have been synthesized. Their cation-binding abilities were investigated by using the solvent extraction method. The poly- and bis(benzothiacrown ether)s showed great affinity for silver ion, being more excellent in the affinity than the corresponding monocyclic analogs. They, however, possess very poor cation-binding ability for alkali and alkaline-earth metal ions. The poly- and bis(thiacrown ether)s also bind mercuric ions effectively, whereas the corresponding monomeric analogs do not at all. 相似文献
17.
Yusuke Fukahori Yohei Takayama Takuya Imaoka Dr. Osamu Iwamoto Prof. Dr. Kazuo Nagasawa 《化学:亚洲杂志》2013,8(1):244-250
We present a diastereoselective synthesis of disubstituted cyclopentane 8 having a nitrogen‐containing quaternary carbon center, which is found in axinellamine A ( 5 ) and related compounds. During this work, we found that the 1,3‐dipolar cycloaddition product 24 immediately underwent intramolecular redox reaction at the newly formed morpholin‐2‐one moiety, thus affording disubstituted cyclopentane containing a tertiary amine ( 9 ) stereoselectively in good yield. The amine 9 was successfully converted into guanidine 31 , which corresponds to 8 , through iminium cation–enamine isomerization. 相似文献
18.
Distribution of pirarubicin in human blood. 总被引:1,自引:0,他引:1
K Nagasawa N Kitada C Tsuji M Ogawa T Yokoyama N Ohnishi S Iwakawa K Okumura 《Chemical & pharmaceutical bulletin》1992,40(10):2866-2869
We investigated the distribution and stability of pirarubicin in human blood obtained from 12 healthy volunteers. The distribution of pirarubicin into blood cells showed marked temperature- and concentration-dependencies and the Arrhenius plot for pirarubicin uptake in blood was biphasic. Therefore, pirarubicin appears to be taken up into blood cells by a carrier-mediated system. Pirarubicin was mainly enzymatically metabolized to pirarubicinol in blood cells, but pirarubicin was not metabolized into doxorubicin in either blood or plasma. On the other hand, in plasma, pirarubicin was degraded to unknown inactive compounds instead of pirarubicinol. It is therefore suggested that blood cells serve to protect against the degradation of pirarubicin into inactive compounds in blood. Accordingly, when the monitoring of pirarubicin and its active metabolites is carried out in patients, both blood and plasma must be frozen immediately after blood collection. 相似文献
19.
Ikeda Y Nakamura T Yorimitsu H Oshima K 《Journal of the American Chemical Society》2002,124(23):6514-6515
A cobalt complex, CoCl2[1,6-bis(diphenylphosphino)hexane], catalyzes an alkylation reaction of styrenes in the presence of Me3SiCH2MgCl in ether to yield beta-alkylstyrenes. A variety of alkyl halides including alkyl chlorides can be employed as an alkyl source. A radical mechanism is strongly suggested for this alkylation reaction. 相似文献
20.
A system involving two polymer-supported reagents for the selective and organocatalytic oxidation of alcohols to aldehydes or ketones has been developed in which both polymeric reagents can be recovered and reused. 相似文献