全文获取类型
收费全文 | 2138篇 |
免费 | 112篇 |
专业分类
2250篇 |
出版年
2023年 | 11篇 |
2022年 | 17篇 |
2021年 | 54篇 |
2020年 | 28篇 |
2019年 | 41篇 |
2018年 | 47篇 |
2017年 | 47篇 |
2016年 | 73篇 |
2015年 | 95篇 |
2014年 | 116篇 |
2013年 | 128篇 |
2012年 | 187篇 |
2011年 | 169篇 |
2010年 | 112篇 |
2009年 | 104篇 |
2008年 | 156篇 |
2007年 | 117篇 |
2006年 | 116篇 |
2005年 | 123篇 |
2004年 | 119篇 |
2003年 | 100篇 |
2002年 | 80篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 28篇 |
1998年 | 15篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1968年 | 4篇 |
1967年 | 2篇 |
1965年 | 3篇 |
排序方式: 共有2250条查询结果,搜索用时 0 毫秒
1.
2.
Hiroshi Taniguchi Takuya Tokida Hiroshi Fujita Hiraku Itikawa 《Molecular & general genetics : MGG》1989,217(2-3):317-323
Summary IndnaK7(Ts) mutant cells, scission of DNA strands occurred after temperature shift up. When cells at 30°C were labeled with [3H]-thymidine and then shifted to 46° or 49°C for 20 min, the profiles of sedimentation of thier cellular DNA in an alkaline
sucrose gradient revealed a decrease in the size of DNA to a quarter of that at 30°C in the mutant, but not in wild-type cells.
The level of manganese-containing superoxide dismutase (MnSOD) in the mutant was about twice that in wild-type cells, even
at the permissive temperature, implying increased production of superoxide radical anion, which may cleave DNA strands directly
or indirectly in the mutant. Moderate increase in the MnSOD level on temperature shift up was observed in both strains. These
results indicated that some components of the DnaK protein participate in protection of cellular membrane functions from thermal
damage resulting from elevated production of the superoxide anion radical. 相似文献
3.
4.
Kazuhisa Toyoda Takuya Sugahara Kunio Inouye Koji Yamada Sanetaka Shirahata Hiroki Murakami 《Cytotechnology》1990,3(2):189-197
An immunoglobulin (Ig) production stimulating factor (IPSF) for hybridomas was found in spent medium of the human B lymphoblastoid cell line, HO-323. The IPSF was purified by serial use of DEAE chromatography, ultrafiltration, gel filtration and HPLC-DEAE chromatography. Purified IPSF was estimated to be a 410 k macro molecule by gel filtration, and contained three types of isomers which were separated from each other by native polyacrylamide gel electrophoresis. All of the isomers were, however, assumed to have the same protein components by SDS polyacrylamide gel electrophoresis.The IPSF was effective for human-human and mouse-mouse hybridomas producing IgM, but not for IgG producers in the experimental condition used here. Human-human hybridoma HF10B4, cultured in IPSF-containing medium, produced 20 times more IgM than in IPSF-free medium under serum-free conditions. The IPSF showed very little proliferation stimulating activity on HF10B4 cells. 相似文献
5.
6.
C Nishio S Komura K Kurahashi 《Biochemical and biophysical research communications》1983,116(2):751-758
Biogenesis of subtilin, an antimicrobial peptide produced by Bacillus subtilis ATCC 6633, was studied in growing cells. Pulse-chase labeling experiments with [35S]cysteine revealed the presence of precursor proteins of subtilin. The synthesis of both precursor proteins and subtilin was inhibited by inhibitors of protein and RNA synthesis. When the precursor proteins were incubated with crude extracts of the organism in vitro, they were converted to subtilin. Pepstatin and phenylmethylsulfonyl fluoride in combination inhibited this conversion. 相似文献
7.
Takuya Kajimoto 《Ecological Research》1989,4(1):55-69
Aboveground biomass and litterfall ofPinus pumila scrubs, growing on the Kiso mountain range in central Japan, were investigated from 1984 to 1985. The biomass of two research
plots (P1 and P2) with different scrub heights was estimated by two methods, the stratified clip technique and the allometric
method. Aboveground total biomass estimated by the latter method reached 181 ton d.w. ha−1 in P1 and 132 ton d.w. ha−1 in P2. Creeping stems contributed to about half of the total biomass. Although estimates of woody organs differed between
the two plots, leaf biomass estimates were almost the same at 15.5 ton d.w. ha−1. The canopies of the twoP. pumila scrubs were characterized by a large mean leaf area density of 5.0 m2 m−3. Despite this large area density, relatively moderate attenuation of light intensity was observed. Specific leaf area generally
increased with reduced leaf height. Annual total litterfall was estimated to be 3.60 ton d.w. ha−1 yr−1 in P1 and 2.39 ton d.w. ha−1 yr−1 in P2. Annual leaf fall in both plots was approximately 2.0 ton d.w. ha−1 yr−1. Leaves fell mainly in early autumn. Annual loss rates of branches, estimated as the sum of annual branch litterfall and
the amount of newly formed attached dead branches, were 0.29 ton d.w. ha−1 yr−1 in P1 and 0.37 ton d.w. ha−1 yr−1 in P2. 相似文献
8.
Summary A 1.2-kb DNA fragment of the cytochrome oxidase subunit I (CO I) gene of mitochondria isolated from an ascidian,Halocynthia roretzi, was amplified by polymerase chain reaction (PCR) and sequenced. Codons AGA and AGG appeared in its reading frame, indicating
that these are sense codons in this organelle. Sequence comparisons with the corresponding regions of other animal mitochondrial
CO I genes suggest that codons AGA and AGG correspond to glycine in the ascidian mitochondrial genome, but not to serine as
in most invertebrate genomes, nor to stops as in vertebrate genomes. The other codons are identical to those of vertebrate
mitochondria. 相似文献
9.
Norio Tada Takuya Sakamoto Akihiko Kagami Keiko Mochizuki Kosei Kurosaka 《Molecular and cellular biochemistry》1993,119(1-2):171-178
Human plasmain vitro inhibits the growth of coagulase negative staphylococci,S. epidermidis, which may be pathogenic in the immunocompromised host. To determine the antimicrobial components, serum was fractionated by column chromatography, which revealed that elution areas where lipoproteins can be yielded had high antimicrobial activity againstS. epidermidis. Therefore, lipoprotein fractions, including very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL), were separated by ultracentrifugation and incubated withS. epidermidis. All 3 lipoprotein fractions suppressed bacterial growth within the first 3 h but VLDL enhanced bacterial growth after 9 h of incubation compared with the control. HDL, however, inhibited bacterial growth throughout 21 h of incubation.To confirm these results, serum from healthy volunteers was separated by ion exchange column chromatography and again by HPLC to purify the antimicrobial fraction. In the protein analysis with gradient polyacrylamide-SDS gel, apolipoprotein Al (apo Al), which is a major apolipoprotein of HDL, was detected in the antimicrobial fraction. Therefore, this fraction was loaded onto an immunoaffinity column coupled with the anti-apo Al monoclonal antibody (Mab). Unbound fraction had no antimicrobial activity, but anti-S. epidermidis activity was recovered from the bound fraction which consisted mainly of apo Al, All and apo C in protein composition.These results indicated that the antimicrobial activity was associated with the apo Al-containing lipoprotein particles (HDL). This property of HDL may directly affect bacterial growth and promote the self-defense mechanisms of normal and immunocompromised individuals. 相似文献
10.
K Ogata A Kurahashi S Tanaka H Kazukiro K Terao H Ohsue 《Journal of biochemistry》1991,110(6):1030-1036
The 5SrRNA in the rat liver postmicrosomal supernatant was investigated. Acrylamide gel electrophoresis and Northern blot analysis showed that most of the 5SrRNA was present in the fractions obtained on high molecular weight regions separated by Sephadex G-200 column chromatography of the supernatant, which contained the bulk of the methionyl-tRNA synthetase (Fraction I) and tyrosyl-tRNA synthetase (Fraction II). A high molecular weight complex containing nine aminoacyl-tRNA synthetases [Mirande, M., LeCorre, D., & Waller, J.-P. (1985) Eur. J. Biochem. 147, 281-289] was purified by fractional precipitation with polyethylene glycol 6000, gel filtration on Bio-Gel A-1.5m, and finally tRNA-Sepharose column chromatography, which gave two fractions. Fraction B showed the activities of nine aminoacyl-tRNA synthetases and gave protein bands corresponding to eight previously identified enzymes on SDS-PAGE. Fraction A, eluted with a lower KCl concentration than Fraction B, showed lower activities than fraction B of eight of the aminoacyl-tRNA synthetases, the exception being prolyl-tRNA synthetase. The staining patterns with ethidium bromide of the RNAs after PAGE showed 5SrRNA bands for Fraction A but not for Fraction B. However, Northern blot analysis indicated that 5SrRNA was present in both Fractions A and B. The staining pattern after SDS-PAGE of Fraction A with Coomassie Brilliant Blue showed several protein bands in addition to those observed for Fraction B, one of which, with a staining intensity comparable with those of other bands, was located at the same position as ribosomal protein L5, which is the protein moiety of the 5SrRNA-L5 protein complex of ribosomal 60S subunits.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献