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   3628篇
  免费   224篇
  国内免费   164篇
  4016篇
  2024年   10篇
  2023年   36篇
  2022年   53篇
  2021年   80篇
  2020年   88篇
  2019年   121篇
  2018年   112篇
  2017年   93篇
  2016年   95篇
  2015年   75篇
  2014年   177篇
  2013年   197篇
  2012年   133篇
  2011年   216篇
  2010年   166篇
  2009年   214篇
  2008年   251篇
  2007年   246篇
  2006年   262篇
  2005年   204篇
  2004年   172篇
  2003年   155篇
  2002年   142篇
  2001年   80篇
  2000年   80篇
  1999年   75篇
  1998年   87篇
  1997年   50篇
  1996年   49篇
  1995年   38篇
  1994年   37篇
  1993年   31篇
  1992年   40篇
  1991年   15篇
  1990年   10篇
  1989年   14篇
  1988年   6篇
  1987年   13篇
  1986年   8篇
  1985年   12篇
  1984年   14篇
  1983年   5篇
  1982年   8篇
  1981年   8篇
  1980年   10篇
  1979年   9篇
  1978年   3篇
  1977年   4篇
  1976年   5篇
  1975年   3篇
排序方式: 共有4016条查询结果,搜索用时 8 毫秒
171.
Plasmodium yoelii is a rodent parasite commonly used as a model to study malaria infection. It is the preferred model parasite for liver-stage immunological studies and is also widely used to study hepatocyte, erythrocyte and mosquito infection. We have generated a P. yoelii yoelii 17XNL line that is stably transfected with the green fluorescent protein (gfp) gene. This parasite line constitutively expresses high levels of GFP during the complete parasite life cycle including liver, blood and mosquito stages. These fluorescent parasites can be used in combination with fluorescence activated cell sorting or live microscopy for a wide range of experimental applications.  相似文献   
172.
173.
In addition to its classic glycolytic role, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been implicated in many activities unrelated to glycolysis, such as membrane fusion, binding to host proteins and signal transduction. GAPDH can be the target of several modifications that allow incorporation to membranes and possible regulation of its activity; among these modifications is mono-ADP-ribosylation. This post-translational modification is important for the regulation of many cellular processes and is the mechanism of action of several bacterial toxins. In a previous study, we observed the extracellular ADP-ribosylation of a 37-kDa ameba protein. We report here that GAPDH and cysteine synthase A are the main ADP-ribosylated proteins in Entamoeba histolytica extracellular medium, GAPDH is secreted from ameba at 37 degrees C in a time-dependent manner, and its enzymatic activity is not inhibited by ADP-ribosylation. Extracellular GAPDH from ameba may play an important role in the survival of this human pathogen or in interaction with host molecules, as occurs in other organisms.  相似文献   
174.
Clusterin is associated with spontaneous breast cancer in TA2 mice   总被引:5,自引:0,他引:5  
Sun B  Zhang S  Zhang D  Liu Y  Li Y  Rong Z  Zhu Y  Jia X 《FEBS letters》2007,581(17):3277-3282
Two-dimensional electrophoresis and Matrix-assisted laser desorption ionization-time of flight-time of mass spectrometry were used to detect the differentially expressed proteins in serum of tientsin albinao 2 mice with spontaneous breast cancer, normal tientsin albinao 2 mice and tientsin albinao 1 mice. Only nuclear clusterin (n-CLU) was expressed in tientsin albinao 1. Immunohistochemistry and western blot validated that n-CLU was present in normal tientsin albinao 2 and tientsin albinao 1 mammary epithelium, and secretory clusterin expressed in the cytoplasm of normal tientsin albinao 2 mammary epithelium and spontaneous breast cancer. n-CLU may play an important role in tientsin albinao 2 spontaneous breast cancer initiation and development.  相似文献   
175.
The Ajuga reptans L. galactan:galactan galactosyltransferase (ArGGT) is a vacuolar enzyme that synthesizes long-chain raffinose family oligosaccharides (RFOs), the major storage carbohydrates of this plant. ArGGT is structurally and functionally related to acid plant alpha-galactosidases (alpha-Gals) of the glycosylhydrolase family 27, present in the apoplast or the vacuole. Sequence comparison of acid alpha-Gals with ArGGT revealed that they all contain an N-terminal signal sequence and a highly similar core sequence. Additionally, ArGGT and some acid alpha-Gals contain C-terminal extensions with low sequence similarities to each other. Here, we show that the C-terminal pentapeptide, SLQMS, is a non-sequence-specific vacuolar sorting determinant. Analogously, we demonstrate that the C-terminal extensions of selected acid alpha-Gals from Arabidopsis, barley, and rice, are also non-sequence-specific vacuolar sorting determinants, suggesting the presence of at least one vacuolar form of acid alpha-Gal in every plant species.  相似文献   
176.
Merret R  Cirioni J  Bach TJ  Hemmerlin A 《FEBS letters》2007,581(27):5295-5299
3-Hydroxy-3-methylglutaryl-CoA reductase (HMGR) is unique in the first part of the cytoplasmic isoprenoid pathway, as it contains a membrane domain that includes ER-specific retention motifs. When fused to GFP, this domain targets two tobacco BY-2 HMGR isoforms differentially. While the first isoform is ER-localized, a second stress-induced one forms globular structures connected by tubular structures. A serine positioned upstream of the ER retention motif seems to be implicated in this specific subcellular localization. Surprisingly, these structures are closely connected to F-actin, and their intactness is dependent upon the integrity of the filaments or the action of a calmodulin antagonist.  相似文献   
177.
Park SH  Oh HB  Seong WK  Kim CW  Cho SY  Yoo CK 《Proteomics》2007,7(20):3743-3758
Bacillus anthracis is a gram-positive bacterial organism responsible for anthrax. This organism has two pathogenic plasmids: pX01 and pX02. The genetic function of pX01, which comprises about 198 kb, is not known, except for a region called the pathogenic island, which contains three genes-pag, lef, and cya-that code for three toxic proteins. A 2-D difference gel electrophoresis (2-D DIGE) system was used to verify the existence of proteins controlled by the pX01 plasmid, and protein regulation data were obtained using DeCyder software. A total of 1728 proteins were identified in the wild-type strain of this organism and 1684 in the pX01 plasmid. Twenty-seven of these proteins disappeared and eight appeared when the pX01 plasmid was removed. An additional 52 proteins were downregulated and 15 were upregulated when this plasmid was removed. A total of 102 proteins have been identified using the MALDI-TOF method of analysis, including 49 whose functions are unknown. Among these, 31 participate in metabolic processes, two in cellular processes, 15 in the processing of genetic information, and five in the processing of extracellular information. Another seven proteins participate in bacterial virulence and pathogenesis. We investigated the functions of these proteins in other bacteria, particularly the B. anthracis derivative H9041. Bacterial growth differed between pX01+/pX02+ B. anthracis and its pX01-/pX02+ derivative as did the cytotoxicity of macrophages infected by pX01+/pX02+ B. anthracis and the pX01-pX02+ derivative. We also found that S100B protein levels increased in the host infected with pX01+/pX02+ B. anthracis or its pX01-/pX02+ derivative. These data suggest that the pX01 plasmid plays a key role in the regulation of protein functions in B. anthracis.  相似文献   
178.
利用野生青狗尾草N10为母本,谷子农家品种大青秸为父本,进行种间杂交,获得了3株杂种。杂种在农艺性状上表现为谷子和青狗尾草的种间类型,花器表现了雄性败育,但雌蕊发育正常,能接受外来花粉结实。细胞形态学观察表明,其雄性败育表现为单核小孢子典败。该谷子雄性不育材料的获得,为利用野生青狗尾草的细胞质培育谷子质核互作雄性不育系,进而为实现谷子三系配套杂种优势利用奠定了基础。  相似文献   
179.
In the present study, different water samples from Red Sea coastal area at Rabigh city, Saudi Arabia were studied for their dominant algal species. Microalgal isolation was carried out based on dilution method and morphologically examined using F/2 as a growth medium. Dry weight and main biochemical composition (protein, carbohydrates, lipids) of all species were performed at the end of the growth, and biodiesel characteristics were estimated. Nannochloropsis sp., Dunaliella sp., Tetraselmis sp., Prorocentrum sp., Chlorella sp., Nitzschia sp., Coscinodiscus sp., and Navicula sp. were the most dominant species in the collected water samples and were used for further evaluation. Nannochloropsis sp. surpassed all other isolates in concern of biomass production with the maximum recorded dry weight of 0.89 g L?1, followed by Dunaliella sp. (0.69 g L?1). The highest crude protein content was observed in Nitzschia sp. (38.21%) and Dunaliella sp. (18.01%), while Nannochloropsis sp. showed 13.38%, with the lowest recorded lipid content in Coscinodiscus sp. (10.09%). Based on the growth, lipid content, and biodiesel characteristics, the present study suggested Dunaliella sp. and Nitzschia sp. as promising candidates for further large-scale biodiesel production.  相似文献   
180.
There is a need for large-scale demonstrations to address the challenges and possibilities for upscaling of ecosystem restoration, and for learning and sharing knowledge across professions and habitats. Large-scale and complex restoration projects need new perspectives on goal formulation, indicators for success, and evaluation to encompass both scientific approaches and the tacit knowledge held by practitioners. The objective of this paper is to use the restoration of a 165 km2 former military training area in alpine central Norway into National Park to demonstrate the challenges of upscaling and integration. Main tasks were to remove roads and technical infrastructure, prepare for natural recovery and remove undetonated ordnance. In total, 19 indicators were used to evaluate the restoration outcome, related to four overall restoration goals formulated by the Norwegian Parliament: nature protection, considerable nature benefit, safe civilian use, and restoration back to natural state. Despite an overall linear project cycle, a dynamic and adaptive process of planning, implementation and evaluation was performed at the individual site scale. A dynamic dialogue between all involved professions allowed for exchanging scientific and tacit knowledge, and continuous improvement of solutions. The study demonstrated the relevance of qualitative assessments combined with quantitative indicators – i.e., use of expert opinions and the continuous evaluation to feed back into planning and improving the implementation of restoration measures. A “Green training” procedure was developed, linking top-down formally defined settings of the project with bottom-up hand-on solutions. This procedure can be directly transferred to other large-scale mitigation and restoration projects. Demonstration sites like the one described here, are valuable to develop an expanded vision of restoration to meet the UN Sustainable Goals.  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