全文获取类型
收费全文 | 3062篇 |
免费 | 174篇 |
国内免费 | 3篇 |
出版年
2022年 | 19篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 21篇 |
2018年 | 34篇 |
2017年 | 45篇 |
2016年 | 69篇 |
2015年 | 91篇 |
2014年 | 100篇 |
2013年 | 172篇 |
2012年 | 168篇 |
2011年 | 215篇 |
2010年 | 113篇 |
2009年 | 146篇 |
2008年 | 207篇 |
2007年 | 191篇 |
2006年 | 174篇 |
2005年 | 190篇 |
2004年 | 154篇 |
2003年 | 171篇 |
2002年 | 175篇 |
2001年 | 70篇 |
2000年 | 62篇 |
1999年 | 50篇 |
1998年 | 37篇 |
1997年 | 34篇 |
1996年 | 39篇 |
1995年 | 27篇 |
1994年 | 25篇 |
1993年 | 17篇 |
1992年 | 33篇 |
1991年 | 25篇 |
1990年 | 31篇 |
1989年 | 33篇 |
1988年 | 32篇 |
1987年 | 13篇 |
1986年 | 26篇 |
1985年 | 19篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1968年 | 8篇 |
排序方式: 共有3239条查询结果,搜索用时 15 毫秒
61.
D Ayusawa K Iwata T Kozu S Ikegami T Seno 《Biochemical and biophysical research communications》1979,91(3):946-954
Mutants that were resistant to aphidicolin were isolated from mutagenized mouse FM3A cells at a frequency of about 10?6. Resistance to aphidicolin in these mutants was not due to an effect on [3H]thymidine incorporation into DNA, DNA synthesis in permeabilized cells, or DNA polymerase α.All the mutants showed a greatly increased dATP pool and decreased ability to incorporate [3H]deoxycytidine into DNA. They also showed cross-resistance to both 1-β-D-arabinofuranosyladenine and 1-β-D-arabinofuranosylcytosine.These results indicate that an enzyme involved in production of dATP or its regulation is altered in these mutants. It is suggested that dATP competes with aphidocolin at its killing site or that dATP reverses the effect of aphidicolin by some unknown mechanism . 相似文献
62.
2-Acetamido-2-deoxy-5-thio-d-glucopyranose (12) has been synthesized from methyl 2-acetamido-2-deoxy-5,6-O-isopropylidene-β-d-glucofuranoside (1). Benzoylation of 1, followed by O-deisopropylidenation, gave methyl 2-acetamido-3-O-benzoyl-2-deoxy-β-d-glucofuranoside, which was converted, via selective benzoylation and mesylation, into methyl 2-acetamido-3,6-di-O-benzoyl-2-deoxy-5-O-mesyl-β-d-glucofuranoside (5). Treatment of 6, formed by the action of sodium methoxide in chloroform on 5, with thiourea gave methyl 2-acetamido-2,5,6-trideoxy-5,6-epithio-β-d-glucofuranoside (7), which was converted into the 5-thio compound 9 by cleavage of the epithio ring in 7 with potassium acetate. Alkaline treatment of 10, derived from 9 by hydrolysis, afforded the title compound. Evidence in support of the structures assigned to the new derivatives is presented. 相似文献
63.
64.
65.
Staphylococcus E-46, which exhibits high virulence in mice mainly due to resistance to phagocytosis, gradually lost its virulence during growth in artificial media [Heart-Infusion (HI) slants]. Staphylococcus E-46 is coagulase-negative and DNase-positive, and has a capsule-like structure, and the less-virulent derivative (LVD) strain seemed not to be changed in this respect. The bacteria which had been exposed to HI slants for more than one year (= LVD strain) became more sensitive to phagocytosis by mouse peritoneal macrophages than bacteria which were kept in a lyophilized state. The chemiluminescent response of macrophages to the LVD strain was remarkably higher than that to the original Staphylococcus E-46. When the LVD or the sera for opsonization were heated, the chemiluminescence to the LVD was as low as that to the original Staphylococcus E-46. Polyacrylamide gel electrophoresis of sonication-released membrane protein from the LVD strain showed a unique band with a molecular weight of about 40,000. The factor concerned with the virulence of Staphylococcus E-46 is discussed based on these results. 相似文献
66.
Heitaroh Iwata Toshio Matsuda Sadaaki Maeda Akemichi Baba 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,583(2):159-166
The effect of ascorbic acid on microsomal thiamine diphosphate activity in rat brain was examined. Ascorbic acid at 0.02–0.1 mM increased the thiamine diphosphate activity by 20–600% and produced a significant amount of lipid peroxide, which was measured with thiobarbiturate under the same conditions as the enzyme. A lag period of about 10 min was observed in the process of stimulation of enzyme activity by ascorbic acid. The stimulation of enzyme activity and the lipid peroxidation induced by ascorbic acid were blocked by metal-binding compounds (EDTA, α,α′-dipyridyl, o-phenanthroline) and an antioxidant (N,N′-diphenyl p-phenylenediamine). GSH significantly enhanced the stimulation of enzyme activity and formation of lipid peroxide by 0.02–0.05 mM ascorbic acid. The effect of GSH was due in part to maintenance of the concentration of ascorbic acid in the medium, since GSH could convert dehydroascorbic acid, an oxidized form of ascorbic acid, to ascorbic acid. 相似文献
67.
Sadako Iwata Kunio Tochikubo Keijiro Kato Takanori Hirata Shozo Kotani Kunio Yagi 《Microbiology and immunology》1976,20(2):123-129
Enzyme(s) capable of decomposing N-acetylglucosaminyl ribitol teichoic acid prepared from the cell wall of Staphylococcus aureus FDA 209 P was obtained from the culture supernatant of a gram-negative, rod-shaped, spore-forming soil bacterium. Properties of the bacterium were very similar to those of Bacillus circulans. 相似文献
68.
69.
Limnology - The in-stream processing of nutrients plays an important role in the fluvial nutrient transport from lands to the ocean, but few empirical studies have addressed the temporal dynamics... 相似文献
70.