全文获取类型
收费全文 | 2688篇 |
免费 | 172篇 |
专业分类
2860篇 |
出版年
2022年 | 23篇 |
2021年 | 26篇 |
2020年 | 21篇 |
2019年 | 39篇 |
2018年 | 36篇 |
2017年 | 44篇 |
2016年 | 54篇 |
2015年 | 96篇 |
2014年 | 95篇 |
2013年 | 154篇 |
2012年 | 204篇 |
2011年 | 170篇 |
2010年 | 127篇 |
2009年 | 109篇 |
2008年 | 191篇 |
2007年 | 217篇 |
2006年 | 188篇 |
2005年 | 170篇 |
2004年 | 182篇 |
2003年 | 176篇 |
2002年 | 176篇 |
2001年 | 26篇 |
2000年 | 19篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 19篇 |
1996年 | 26篇 |
1995年 | 21篇 |
1994年 | 24篇 |
1993年 | 19篇 |
1992年 | 9篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有2860条查询结果,搜索用时 11 毫秒
161.
Internodal elongation in floating rice (Oryza sativa) is known to be enhanced by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH). However, ethylene-induced internodal elongation is inhibited at low RH, while GA3-induced internodal elongation is hardly affected by humidity. We examined the effects of ethylene and GA3 on the rate of transpiration in stem segments incubated at 30% or 100% RH. Ethylene promoted the transpiration of stem segments at 30% RH, but not at 100% RH, while GA3 had little effect on transpiration at either 30% or 100% RH. We propose that the absence of ethylene-induced internodal elongation at low RH is due, at least in part, to ethylene-induced transpiration. 相似文献
162.
163.
Identification of the lantibiotic nisin Q,a new natural nisin variant produced by Lactococcus lactis 61-14 isolated from a river in Japan 总被引:1,自引:0,他引:1
Zendo T Fukao M Ueda K Higuchi T Nakayama J Sonomoto K 《Bioscience, biotechnology, and biochemistry》2003,67(7):1616-1619
Lactococcus lactis 61-14 isolated from river water produced a bacteriocin active against a wide range of Gram-positive bacteria. N-terminal amino acid sequencing, mass spectral analysis of the purified bacteriocin, and genetic analysis using nisin-specific primers showed that the bacteriocin was a new natural nisin variant, termed nisin Q. Nisin Q and nisin A differ in four amino acids in the mature peptide and two in the leader sequence. 相似文献
164.
Saiki R Ogiyama Y Kainou T Nishi T Matsuda H Kawamukai M 《BioFactors (Oxford, England)》2003,18(1-4):229-235
We previously constructed two Schizosaccahromyces pombe ubiquinone-10 (or Coenzyme Q10) less mutants, which are either defective for decaprenyl diphosphate synthase or p-hydroxybenzoate polyprenyl diphosphate transferase. To further confirm the roles of ubiquinone in S. pombe, we examined the phenotype of the abc1Sp (coq8Sp) mutant, which is highly speculated to be defective in ubiquinone biosynthesis. We show here that the abc1Sp defective strain did not produce UQ-10 and could not grow on minimal medium. The abc1Sp-deficient strain required supplementation with antioxidants such as cysteine or glutathione to grow on minimal medium. In support of the antioxidant function of ubiquinone, the abc1Sp-deficient strain is sensitive to H2O2 and Cu2+. In addition, expression of the stress inducible ctt1 gene was much induced in the ubiquinone less mutant than wild type. Interestingly, we also found that the abc1-deficient strain as well as other ubiquinone less mutants produced a significant amount of H2S, which suggests that oxidation of sulfide by ubiquinone may be an important pathway for sulfur metabolism in S. pombe. Thus, analysis of the phenotypes of S. pombe ubiquinone less mutants clearly demonstrate that ubiquinone has multiple functions in the cell apart from being an integral component of the electron transfer system. 相似文献
165.
Stimulatory effect of regucalcin on proteolytic activity is impaired in the kidney cortex cytosol of rats with saline ingestion 总被引:1,自引:0,他引:1
The effect of regucalcin (RC) on neutral proteolytic activity in the cytosol of rat kidney cortex was investigated. Proteolytic activity was significantly increased by the presence of RC (0.01 + 0.10 M) in the enzyme reaction mixture. This increase was completely abolished by the addition of anti-RC monoclonal antibody (150 ng/ml). When the renal cortex cytosol was incubated without RC addition, the degradation of globin of substrate was demonstrated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. This degradation was clearly inhibited by the addition of anti-RC antibody (150 ng/ml), indicating that protein degradation results partly from the cytosolic endogenous RC. Meanwhile, proteolytic activity was significantly decreased in the renal cortex cytosol of rats with saline ingestion for 2, 7, and 14 days. The effect of RC (0.1 M) in increasing proteolytic activity was weakened in the kidney cortex cytosol of saline-ingested rats. The present study suggests that endogenous RC plays a role in the activation of proteases in the renal cortex cytosol, and that the RC effect is impaired in saline-ingested rats. 相似文献
166.
167.
Identification and Cloning of waaF (rfaF) from Bordetella pertussis and Use To Generate Mutants of Bordetella spp. with Deep Rough Lipopolysaccharide
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A DNA locus from Bordetella pertussis capable of reconstituting lipopolysaccharide (LPS) O-antigen biosynthesis in Salmonella typhimurium SL3789 (rfaF511) has been isolated, by using selection with the antibiotic novobiocin. DNA within the locus encodes a protein with amino acid sequence similarity to heptosyltransferase II, encoded by waaF (previously rfaF) in other gram-negative bacteria. Mutation of this gene in B. pertussis, Bordetella parapertussis, and Bordetella bronchiseptica by allelic exchange generated bacteria with deep rough LPS phenotypes consistent with the proposed function of the gene as an inner core heptosyltransferase. These are the first LPS mutants generated in B. parapertussis and B. bronchiseptica and the first deep rough mutants of any of the bordetellae. 相似文献
168.
Toshikazu Ushijima Tomoko Nomoto Takashi Sugimura David E. Housman Minako Nagao 《Mammalian genome》1998,9(12):1008-1012
Mapping of genetic suppressors, modifiers, and quantitative trait loci (QTLs) requires genetic markers that can be efficiently
and inexpensively genotyped for a large number of individuals. To isolate rat genetic markers suitable for this purpose, representational
difference analysis (RDA) was performed with amplicons prepared by PCR with the B1 repetitive sequence used as the primer
(B1-amplicons). In total, 48 polymorphic DNA fragments were isolated by five series of RDA, subtracting the B1-amplicons prepared
from an ACI/N (ACI) rat from those prepared from BUF/Nac (BUF), and vice versa. All the polymorphic fragments detected ``presence-or-absence'
polymorphisms with B1-amplicons prepared from ACI, BUF, and their F2 progeny, and each fragment was linkage mapped. Dot-blotting amplicons onto filters at a high density and hybridization of
the filters with these B1-RDA markers made it possible to genotype a large number of rats simultaneously for multiple loci.
These B1-RDA markers were polymorphic between two given inbred strains of rat at frequencies between 30% and 70%. This is
the first report on the isolation of B1-RDA markers among inbred strains of rats.
Received: 15 July 1998 / Accepted: 18 August 1998 相似文献
169.
Tokuo Saito Takamasa Ueno Tomoko Kubori Shigeru Yamaguchi Tetsuo Iino & Shin-Ichi Aizawa 《Molecular microbiology》1998,27(6):1129-1139
Among motile revertants isolated from flagellar hook-deficient ( flgE ) mutants of Salmonella typhimurium one produced only short flagellar filaments in L broth, despite the fact that flagellin itself has the ability to polymerize into long filaments in vitro . This pseudorevertant has an intragenic suppressor, resulting in a two-amino-acid substitution (Asp-Gln→Ala-Arg) in the C-terminal region of the hook protein, FlgE. The flagellation of the pseudorevertant was greatly affected by the concentration of NaCl in the culture media: we observed no filaments in the absence of NaCl, short filaments in 1% NaCl and full-length filaments in 2% NaCl. Electron microscopy of osmotically shocked cells showed that the number of hook–basal bodies on cells was constant under various NaCl conditions. Furthermore, we found that the mutant hook was straight rather than curved. We monitored the cellular flagellin level of this pseudorevertant under various NaCl concentrations by immunoblotting. It was revealed that little flagellin was present under NaCl-free conditions in contrast with the ordinary amounts of flagellin present in 2% NaCl. As the expression of flagellin is regulated by competitive interaction of a sigma factor, FliA, and a corresponding anti-sigma factor, FlgM, we also observed the effect of NaCl on the secretion of FlgM. FlgM was secreted into the media in more than 1% NaCl but accumulated inside the cells in the absence of NaCl, indicating that the failure of secretion of FlgM in the absence of salt was the cause of the impaired elongation of filaments. 相似文献
170.
Noriaki Kurata Tomoko Kuramitsu Hiromi Tanii Eiichi Fuse Takashi Kuwabara Hiroyuki Kobayashi Satoshi Kobayashi 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,708(1-2)
We have established a highly sensitive high-performance liquid chromatographic method for the determination of an anticancer drug, UCN-01, in human plasma or urine. Using a fluorescence detector set at an excitation wavelength of 310 nm and emission monitored at 410 nm, there was a good linearity for UCN-01 in human plasma (r=0.999) or urine (r=0.999) at concentrations ranging from 0.2 to 100 ng/ml or 1 to 400 ng/ml, respectively. For intra-day assay, in plasma samples, the precision and accuracy were 1.8% to 5.6% and −10.0% to 5.2%, respectively. For inter-day assay, the precision and accuracy were 2.0% to 18.2% and 2.4% to 10.0%, respectively. In urine samples, the intra- and inter-day precision and accuracy were within 3.9% and ±2.7%, respectively. The lower limit of quantification (LLOQ) was set at 0.2 ng/ml in plasma and 1 ng/ml in urine. UCN-01 in plasma samples was stable up to two weeks at −80°C and also up to four weeks in urine samples. This method could be very useful for studying the human pharmacokinetics of UCN-01. 相似文献