全文获取类型
收费全文 | 2556篇 |
免费 | 148篇 |
国内免费 | 1篇 |
专业分类
2705篇 |
出版年
2022年 | 20篇 |
2021年 | 41篇 |
2020年 | 17篇 |
2019年 | 16篇 |
2018年 | 38篇 |
2017年 | 39篇 |
2016年 | 56篇 |
2015年 | 85篇 |
2014年 | 100篇 |
2013年 | 142篇 |
2012年 | 164篇 |
2011年 | 157篇 |
2010年 | 104篇 |
2009年 | 99篇 |
2008年 | 130篇 |
2007年 | 164篇 |
2006年 | 146篇 |
2005年 | 137篇 |
2004年 | 122篇 |
2003年 | 135篇 |
2002年 | 109篇 |
2001年 | 46篇 |
2000年 | 50篇 |
1999年 | 40篇 |
1998年 | 40篇 |
1997年 | 41篇 |
1996年 | 28篇 |
1995年 | 31篇 |
1994年 | 28篇 |
1993年 | 18篇 |
1992年 | 26篇 |
1991年 | 31篇 |
1990年 | 21篇 |
1989年 | 23篇 |
1988年 | 15篇 |
1987年 | 18篇 |
1986年 | 12篇 |
1985年 | 28篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1974年 | 14篇 |
1973年 | 13篇 |
1970年 | 9篇 |
1969年 | 8篇 |
排序方式: 共有2705条查询结果,搜索用时 0 毫秒
1.
S Ikei M Ogawa T Beppu C Ohara K Sakamoto H Sameshima H Arakawa Y Yamaguchi T Yamanaka S Kudo 《Cytokine》1992,4(6):581-584
In an attempt to investigate the interaction between the changes of cytokines and acute phase reactants after transcatheter arterial chemoembolization therapy (TACE), the levels of interleukin 6 (IL-6), interleukin 8 (IL-8), C-reactive protein (CRP) and pancreatic secretory trypsin inhibitor (PSTI) in the blood of patients with unresectable hepatocellular carcinoma (HCC) were measured. Before the therapy, serum IL-6 and plasma IL-8 levels were detectable in 77.8% and 28.5%, respectively, of patients with HCC. Levels of serum IL-6 and plasma IL-8 increased after TACE and reached a peak on day 3 in all patients (18/18) and in 87.5% of patients (12/14), respectively. Both blood levels of IL-6 and IL-8 reached a peak earlier than those of CRP and PSTI did after the therapy. When the maximal values of IL-6 were compared with those of CRP and PSTI, there were significant positive correlations (r = 0.63, P < 0.01 and r = 0.81, P < 0.01, respectively). Similarly, comparisons of the maximal values of IL-8 with those of CRP and PSTI gave a significant correlation (r = 0.68, P < 0.01 and r = 0.67, P < 0.05, respectively). However, no significant correlation was found between the elevation of IL-6 and IL-8. 相似文献
2.
3.
Condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solutions 总被引:1,自引:0,他引:1
Junpei Yamanaka Katsuhiko Inomata Yukio Yamagata 《Origins of life and evolution of the biosphere》1988,18(3):165-178
The dehydration condensation of glycine with trimetaphosphate in aqueous solution has been reinvestigated. Although it has been reported that the condensation of glycine under the alkaline conditions was brought about through the formation of cyclic acylphosphoramidate and hence the condensation of polyglycines could not occur, we found that the condensation of oligoglycines with trimeta- and tetrametaphosphate in aqueous solution are possible through the formation of their acylphosphates under the neutral or weak acidic conditions.Aqueous solutions of 1.0 M glycylglycine and 1.0 M trimetaphosphate in the various pH from 4.0 to 9.0 were incubated at 38 °C. The solutions were analyzed by HPLC with ninhydrin reaction system. Tetraglycine and hexaglycine were detected and their maximum yields were given in the reaction carried out around pH 7. They are approximately 15% and 4% after 30 days, respectively. Analogous experiments were performed with tetrametaphosphate. The results showed a similar pH dependence for the condensation, but the yields were about one-tenth of those of corresponding experiments with trimetaphosphate.Relative rates of dimerization of glycine, diglycine and triglycine in the equimolar concentration were also investigated at pH 6.0 at 38 °C. The rates for digylcine and triglycine were approximately twice and four times as large as that for glycine.Relevance of the experiments to chemical evolution is discussed. 相似文献
4.
Kunitoshi Yamanaka Teru Ogura Kazuyoshi Murata Toshinobu Suzaki Hironori Niki Sota Hiraga 《FEMS microbiology letters》1994,116(1):61-66
Abstract The smbA gene of Escherichia coli is essential for cell proliferation. The smbA2 mutant shows cold-sensitive colony formation at 22°C. A novel morphological phenotype, formation of a translucent segment at midcell or at a cell pole, was observed by phase-contrastt microscopy at a high frequency in the smbA2 mutant cells incubated in L medium lacking NaCl at 22°C, but not observed in L medium containing 1% NaCl or 20% sucrose at the same temperature. No translucent segment was observed in the wild-type cells in any of the media used. Electron microscopic observation revealed that the translucent segments resulted from the enlargement of a periplasmic space by separation of the inner membrane from the peptidoglycan layer and the outer membrane. 相似文献
5.
The values of pH and the concentrations of nitrogen (N) and ammonia in the middle part of the small intestinal and cecal contents of germfree (GF) and conventionalized (CVZ) seven-week-old rats were compared. The pH of the small intestinal and cecal contents of GF rats was higher than that of CVZ rats. There was no difference in total N per fresh weight in contents from the middle part of the small intestine between GF and CVZ, whereas total N per fresh weight of the cecal contents was higher in CVZ than in GF rats. The ammonia concentrations per fresh weight or per total N in the intestinal and cecal contents of CVZ rats were higher than those of GF rats. 相似文献
6.
7.
Yoshihiro Takasugi Keiji Kawata Takahiko Okuda Yoshihisa Koga Nobuyuki Mizuguchi Shigeaki Yamanaka Shinsuke Watanabe 《Experimental Animals》2003,52(5):429-432
Age-related alterations and differences of weights and those of amino acid concentrations in the cerebrospinal fluid (CSF) were evaluated between Sprague Dawley (SD) rats and Wistar Kyoto (WKY) rats from eight to twenty weeks of age. The weights of SD rats were heavier than WKY rats at all ages. The age-related alterations of the CSF concentration of many amino acids within each strain were significant but showed no significant trend with age. Between the strains, the concentration differences of excitatory and inhibitory amino acids were not frequent although the concentrations of arginine, alanine and threonine were significantly higher in SD rats than in WKY rats. These results suggest that the different CSF concentrations of amino acids may relate to characteristics of rat strains. 相似文献
8.
Selective inhibition of growth by pentitols was observed when Klebsiella aerogenes M-7 which could not utilize pentitols was grown on pentoses. D-Arabitol inhibited the growth on D-arabinose as a sole carbon source, but had no effect on the growth on L-arabinose, D-xylose, and D-ribose. Similarly, L-arabitol inhibited the growth on D-arabinose and L-arabinose, ribitol inhibited the growth on D-arabinose and L-arabinose, and xylitol inhibited the growth on D-xylose. From the following reasons, we postulated that the selective growth inhibition by pentitols was due to the competitive inhibition of pentose isomerase reaction by the cell by pentitols. (i) D-Arabinose transport activity was not inhibited by pentitols. (ii) Induction of D-arabinose and L-arabinose isomerases was not inhibited by D- and L-arabitol, respectively. (iii) The specificity of growth inhibition by pentitols was the same as that of competitive inhibition of pentose isomerases by pentitols. 相似文献
9.
N Kida S Suzuki T Yamanaka K Furuyama F Taguchi 《Nihon saikingaku zasshi. Japanese journal of bacteriology》1992,47(4):625-629
Ethylenediaminetetraacetic acid (EDTA), a chelating agent, was examined for the antibacterial activity against 15 species of bacteria by treating with a 10mM solution at pH adjusted to 5.0, 7.0 or 9.0. All bacterial species tested were classified into three groups; tentatively named the pH5 EDTA-sensitive group comprising Vibrio cholerae and Staphylococcus aureus, the pH9 EDTA-sensitive group comprising Escherichia coli and Pseudomonas aeruginosa and the EDTA-nonsensitive group comprising Proteus mirabilis. The EDTA-sensitivity grouping may be used as a tool for preferential decontamination of certain bacteria in live edible fishes, although further experiments are needed to characterize more strains and also species of bacteria. 相似文献
10.
A novel type of cytochrome c oxidase was purified to homogeneity from Pseudomonas aeruginosa which was grown aerobically. The purified oxidase contained two molecules of heme a, two atoms of copper, and one molecule of protoheme per molecule. One of the two heme a molecules in the oxidase reacted with carbon monoxide, so that the enzyme was of baa3-type. The oxidase molecule was composed of three subunits with molecular weights of 38,000, 57,000, and 82,000. Although the oxidase oxidized ferrocytochrome c-550 obtained from the bacterial cells grown aerobically, the oxidizing activity was not high. The "resting form" and the "pulsed form" of the oxidase were observed clearly with this enzyme, and the transition from the resting form to the pulsed form was accompanied by a distinct change of the enzymatic activity. The difference in the kinetics of the catalytic reactions between the two forms is discussed. 相似文献