全文获取类型
收费全文 | 2815篇 |
免费 | 138篇 |
国内免费 | 1篇 |
专业分类
2954篇 |
出版年
2022年 | 14篇 |
2021年 | 28篇 |
2020年 | 15篇 |
2019年 | 22篇 |
2018年 | 40篇 |
2017年 | 43篇 |
2016年 | 69篇 |
2015年 | 92篇 |
2014年 | 93篇 |
2013年 | 193篇 |
2012年 | 177篇 |
2011年 | 165篇 |
2010年 | 121篇 |
2009年 | 108篇 |
2008年 | 163篇 |
2007年 | 167篇 |
2006年 | 165篇 |
2005年 | 158篇 |
2004年 | 120篇 |
2003年 | 125篇 |
2002年 | 119篇 |
2001年 | 42篇 |
2000年 | 52篇 |
1999年 | 53篇 |
1998年 | 30篇 |
1997年 | 27篇 |
1996年 | 30篇 |
1995年 | 26篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 31篇 |
1991年 | 29篇 |
1990年 | 35篇 |
1989年 | 29篇 |
1988年 | 25篇 |
1987年 | 20篇 |
1986年 | 24篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1974年 | 14篇 |
1972年 | 12篇 |
1971年 | 15篇 |
排序方式: 共有2954条查询结果,搜索用时 15 毫秒
1.
Genes for the biosynthesis of spinosyns: applications for yield improvement in Saccharopolyspora spinosa 总被引:2,自引:0,他引:2
K Madduri C Waldron P Matsushima M C Broughton K Crawford D J Merlo R H Baltz 《Journal of industrial microbiology & biotechnology》2001,27(6):399-402
Spinosyns A and D are the active ingredients in an insect control agent produced by fermentation of Saccharopolyspora spinosa. Spinosyns are macrolides with a 21-carbon, tetracyclic lactone backbone to which the deoxysugars forosamine and tri-O-methylrhamnose are attached. The spinosyn biosynthesis genes, except for the rhamnose genes, are located in a cluster that
spans 74 kb of the S. spinosa genome. DNA sequence analysis, targeted gene disruptions and bioconversion studies identified five large genes encoding type
I polyketide synthase subunits, and 14 genes involved in sugar biosynthesis, sugar attachment to the polyketide or cross-bridging
of the polyketide. Four rhamnose biosynthetic genes, two of which are also necessary for forosamine biosynthesis, are located
outside the spinosyn gene cluster. Duplication of the spinosyn genes linked to the polyketide synthase genes stimulated the
final step in the biosynthesis — the conversion of the forosamine-less pseudoaglycones to endproducts. Duplication of genes
involved in the early steps of deoxysugar biosynthesis increased spinosyn yield significantly. Journal of Industrial Microbiology & Biotechnology (2001) 27, 399–402.
Received 31 May 2001/ Accepted in revised form 09 July 2001 相似文献
2.
The cdc6 mutants of Schizosaccharomyces pombe have been classified as being defective in progression through the G2 phase of the cell cycle. We cloned an S. pombe gene that could complement the temperature-sensitive growth of the cdc6-23 mutant. Unexpectedly, the cloned gene was allelic to pol3, which encodes the catalytic subunit of DNA polymerase δ. Integration mapping confirmed that cdc6 and pol3 are identical. The cdc6-23 mutant carries one amino acid substitution in the conserved N3 region of Pol3.
Received: 17 October 1996 / Accepted: 19 November 1996 相似文献
3.
4.
Yuichi Esaki Kenji Obayashi Keigo Saeki Kiyoshi Fujita Nakao Iwata Tsuyoshi Kitajima 《Chronobiology international》2020,37(6):887-896
ABSTRACT Previous studies have found that keeping the room dark at night was associated with a decrease in manic symptoms for patients with bipolar disorder (BD). However, the association between light at night of real-life conditions and manic symptoms is unclear. We investigated the association between bedroom light exposure at night and manic symptoms in BD patients. One-hundred and eighty-four outpatients with BD participated in this cross-sectional study. The average light intensity at night during sleep was evaluated using a portable photometer for seven consecutive nights. Manic symptoms were assessed using the Young Mania Rating Scale (YMRS), and scores ≥5 were treated as a “hypomanic state.” The median (interquartile range) YMRS score was 2.0 (0–5.0), and 52 (28.2%) participants were in a hypomanic state. The prevalence of a hypomanic state was significantly higher in the participants with an average light intensity at night exposure of ≥3 lux than in those with <3 lux (36.7% versus 21.9%; P = .02). In multivariable logistic regression analysis adjusted for BD type, depressive symptoms, sleep duration, and daytime physical activity, the odds ratio (OR) for a hypomanic state was significantly higher for the participants with an average light intensity at night exposure of ≥3 lux than for those with <3 lux (OR: 2.15, 95% confidence interval: 1.09–4.22, P = .02). This association remained significant at the cutoff value of YMRS score ≥6 (OR: 2.51, 95% confidence interval: 1.15–5.46; P = .02). The findings of this study indicate bedroom light exposure at night is significantly associated with manic symptoms in BD patients. Although the results of this cross-sectional investigation do not necessarily imply causality, they may serve to inform beneficial nonpharmacological intervention and personalized treatment of BD patients. 相似文献
5.
6.
Production of monocyte chemotactic and activating factor (MCAF) by human dermal fibroblasts in response to interleukin 1 or tumor necrosis factor 总被引:16,自引:0,他引:16
C G Larsen C O Zachariae J J Oppenheim K Matsushima 《Biochemical and biophysical research communications》1989,160(3):1403-1408
Normal human dermal fibroblasts rapidly expressed (less than 30 min.) considerable mRNA for monocyte chemotactic and activating factor (MCAF) and released high levels of biological activity in response to interleukin 1 (IL 1) or tumor necrosis factor (TNF). In contrast, cultured normal human keratinocytes did not express MCAF mRNA when stimulated with IL 1 or TNF. These results suggest the important role of dermal fibroblasts, the predominant cells in dermal connective tissue, in the recruitment of monocytes during inflammation. This is the first report of the induction of MCAF by IL 1 or TNF in any cell type. 相似文献
7.
Cloning and sequencing of the cDNA for human monocyte chemotactic and activating factor (MCAF) 总被引:28,自引:0,他引:28
Y Furutani H Nomura M Notake Y Oyamada T Fukui M Yamada C G Larsen J J Oppenheim K Matsushima 《Biochemical and biophysical research communications》1989,159(1):249-255
cDNA clones having a nucleotide sequence encoding a human monocyte chemotactic and activating factor (MCAF) were isolated and sequenced. The amino acid sequence deduced from the nucleotide sequence reveals the primary structure of the MCAF precursor to be composed of a putative signal peptide sequence of 23 amino acid residues and a mature MCAF sequence of 76 amino acid residues. The amino acid sequence of MCAF showed 25-55% homology with other members of an inducible cytokine family, including macrophage inflammatory protein and some putative polypeptide mediators known as JE, LD78, RANTES and TCA-3. This suggests that MCAF is a member of family of factors involved in immune and inflammatory responses. 相似文献
8.
9.
Fujita Yuichi; Takahashi Yasuhiro; Shonai Fumio; Ogura Yutaka; Matsubara Hiroshi 《Plant & cell physiology》1991,32(7):1093-1106
The frxC gene, found in liverwort chloroplast DNA, encodes aprotein of unknown function. The deduced amino acid sequenceof the protein shows significant homology to that of ni-trogenaseFe-protein encoded by the nifH gene. We have cloned the frxCand nifH genes from the nitrogen-fixing cyanobacterium Plectonemaboryanum, using frxC- and nifH-specific probes, and have determinedtheir nucleotide sequences. The amino acid sequence deducedfrom the frxC gene of P. boryanum exhibits 83% homology to thatof the protein encoded by the/rxCgene from liverwort, whereasit exhibits only 34% homology to that encoded by the nifH genefrom the same organism, namely, P. boryanum. Northern blot analysisshowed that the frxC gene was transcribed more actively undernitrogenase-repressed conditions than under nitrogenase-inducedconditions, suggesting that the FrxC protein has a functiondistinct from nitrogen fixation. These results, together withthe phylogenetic relationship between the nifH and frxC genes,indicate that the frxC and nifH genes are derived from a commonancestral gene but have evolved independently to encode proteinswith different functions. (Received April 27, 1991; Accepted August 12, 1991) 相似文献
10.
Amylase activity in the saliva, salivary glands, serum, liver (perfused and non perfused) and pancreas was assayed and isoamylases were separated by electrophoresis in these organs using C57BR/cdJ and M. m. molossinus (Kor) mice. Amylase isozymes in the saliva, parotid gland, serum and liver were identical in both strains, respectively. Amylase activity in the liver was lower than that in the serum and liver amylase disappeared almost by perfusion. Major serum amylase was released from the parotid gland in intact animals. 相似文献