首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2812篇
  免费   138篇
  国内免费   1篇
  2022年   16篇
  2021年   21篇
  2020年   14篇
  2019年   22篇
  2018年   25篇
  2017年   23篇
  2016年   39篇
  2015年   67篇
  2014年   89篇
  2013年   236篇
  2012年   152篇
  2011年   173篇
  2010年   116篇
  2009年   108篇
  2008年   189篇
  2007年   158篇
  2006年   160篇
  2005年   160篇
  2004年   149篇
  2003年   168篇
  2002年   153篇
  2001年   47篇
  2000年   43篇
  1999年   42篇
  1998年   43篇
  1997年   44篇
  1996年   31篇
  1995年   28篇
  1994年   21篇
  1993年   36篇
  1992年   36篇
  1991年   28篇
  1990年   23篇
  1989年   21篇
  1988年   14篇
  1987年   24篇
  1986年   18篇
  1985年   19篇
  1984年   20篇
  1983年   29篇
  1982年   20篇
  1981年   21篇
  1980年   13篇
  1979年   7篇
  1978年   15篇
  1977年   9篇
  1976年   6篇
  1975年   9篇
  1974年   7篇
  1970年   7篇
排序方式: 共有2951条查询结果,搜索用时 46 毫秒
91.
Applied Entomology and Zoology - The pink citrus rust mite, Aculops pelekassi (Keifer) (Acari: Eriophyidae), is a serious pest and is widely distributed in most citrus-growing areas of the world....  相似文献   
92.
Dietary carotenoids are absorbed in the intestine and delivered to various tissues by circulating lipoproteins; however, the mechanism underlying selective delivery of different carotenoid species to individual tissues remains elusive. The products of the Yellow cocoon (C) gene and the Flesh (F) gene of the silkworm Bombyx mori determine the selectivity for transport of lutein and β-carotene, respectively, to the silk gland. We previously showed that the C gene encodes Cameo2, a CD36 family member, which is thought to function as a transmembrane lipoprotein receptor. Here, we elucidated the molecular identity of the F gene product by positional cloning, as SCRB15, a paralog of Cameo2 with 26% amino acid identity. In the F mutant, SCRB15 mRNA structure was severely disrupted, due to a 1.4 kb genomic insertion in a coding exon. Transgenic expression of SCRB15 in the middle silk gland using the binary GAL4-UAS expression system enhanced selective β-carotene uptake by the middle silk gland, while transgenic expression of Cameo2 enhanced selective lutein uptake under the same GAL4 driver. Our findings indicate that divergence of genes in the CD36 family determines the selectivity of carotenoid species uptake by silk gland tissue and that CD36-homologous proteins can discriminate among carotenoid species.  相似文献   
93.
Here, we demonstrate display of beta-glucosidase (BGL) on the surface of Schizosaccharomyces pombe cells using novel anchor proteins. A total of four candidate anchor proteins (SPBC21D10.06c, SPBC947.04, SPBC19C7.05, and SPBC359.04c) were selected from among almost all of S. pombe membrane proteins. The C-terminus of each anchor protein was genetically fused to the N-terminus of BGL, and the fusion protein was expressed using S. pombe as a host. The highest cell surface-associated BGL activity (107 U/105 cells was achieved with SPBC359.04c serving as the anchor, followed by SPBC947.04 (44 U/105 cells) and SPBC21D10.06c (38 U/105 cells). S. pombe displaying BGL with SPBC359.04c as an anchor showed the highest growth on 2 % cellobiose (10.7?×?107 cells/mL after 41 h of cultivation from an initial density of 0.1?×?107 cells/mL). Additionally, culturing BGL-displaying S. pombe in medium containing cellobiose as the sole carbon source did not affect protein expression, and ethanol fermentation from cellobiose was successfully demonstrated using BGL-displaying S. pombe. This is the first report describing a cell surface display system for the functionalization of S. pombe.  相似文献   
94.
Thermoplasma acidophilum is a thermo-acidophilic archaeon. We purified tRNALeu (UAG) from T. acidophilum using a solid-phase DNA probe method and determined the RNA sequence after determining via nucleoside analysis and m7G-specific aniline cleavage because it has been reported that T. acidophilum tRNA contains m7G, which is generally not found in archaeal tRNAs. RNA sequencing and liquid chromatography–mass spectrometry revealed that the m7G modification exists at a novel position 49. Furthermore, we found several distinct modifications, which have not previously been found in archaeal tRNA, such as 4-thiouridine9, archaeosine13 and 5-carbamoylmethyuridine34. The related tRNA modification enzymes and their genes are discussed.  相似文献   
95.
96.
A series of novel 6-(aminomethylphenoxy)benzoxaborole analogs was synthesized for the investigation of the structure–activity relationship of the inhibition of TNF-alpha, IL-1beta, and IL-6, from lipopolysaccharide stimulated peripheral blood mononuclear cells. Compounds 9d and 9e showed potent activity against all three cytokines with IC50 values between 33 and 83 nM. Chloro substituted analog 9e (AN3485) is considered to be a promising lead for novel anti-inflammatory agent with a favorable pharmacokinetic profile.  相似文献   
97.
Structure–activity relationships of 6-(benzoylamino)benzoxaborole analogs were investigated for the inhibition of TNF-α, IL-1β, and IL-6 from lipopolysaccharide stimulated peripheral blood mononuclear cells. Compound 1q showed potent activity against all three cytokines with IC50 values between 0.19 and 0.50 μM, inhibited LPS-induced TNF-α and IL-6 elevation in mice and improved collagen-induced arthritis in mice. Compound 1q (AN4161) is considered to be a promising lead for novel anti-inflammatory agent with an excellent pharmacokinetic profile.  相似文献   
98.
Glycogen synthase (GS) catalyzes the transfer of glucose residues from UDP-glucose to a glycogen polymer chain, a critical step for glucose storage. Patients with type 2 diabetes normally exhibit low glycogen levels and decreased muscle glucose uptake is the major defect in whole body glucose disposal. Therefore, activating GS may provide a potential approach for the treatment of type 2 diabetes. In order to identify non-carboxylic acids GS activators, we designed and synthesized a series of 2-N-alkyl- and 2-N-aryl-indazolone derivatives and studied their activity in activating human GS.  相似文献   
99.
Despite almost 30 years since the identification of the human immunodeficiency virus type I (HIV-1), development of effective AIDS vaccines has been hindered by the high mutability of HIV-1. The HIV-1 co-receptors CCR5 and CXCR4 are genetically stable, but viral proteins may mutate rapidly during the course of infection. CXCR4 is a seven transmembrane G protein-coupled receptor, possessing an N-terminal region (NT) and three extracellular loops (ECL1-3). Previous studies have shown that the CXCR4-ED-derived peptides inhibit the entry of HIV-1 by interacting with gp120, an HIV-1 envelope glycoprotein. In the present study, antigenicity of CXCR4-derived peptides has been investigated and the anti-HIV-1 effects of induced antisera have been assessed. It was found that CXCR4-ED-derived antigen molecules immunize mice, showing that the linear peptides have higher antigenicity than the cyclic peptides. The L1- and L2-induced antisera inhibited the HIV-1 entry significantly, while anti-N1 antibodies have no inhibitory activity. This study produced promising examples for the design of AIDS vaccines which target the human protein and can overcome mutability of HIV-1.  相似文献   
100.
The presence of glucose-6-phosphate markedly stimulated the anaerobic utilization of glyoxylate by either cell-free extracts or partially purified enzyme preparations of coli-aerogenes bacteria. The enzymic reduction of glyoxylate to glycollate was found to occur in the presence of TPN with the following substrates; glucose-6-phosphate, glucose plus ATP, gluconate plus ATP, glucose-1-phosphate or malate. The data indicated that the reduction of glyoxylate to glycollate was coupled to the oxidation of glucose-6-phosphate via the hexose monophosphate shunt pathway. It was propounded that the operation of the hexose monophosphate oxidative pathway might be controlled by TPN-linked glyoxylic reductase, and the mechanisms of enzymic regulation in microbial respiration were also discussed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号