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   1245篇
  免费   52篇
  国内免费   24篇
  2022年   12篇
  2021年   19篇
  2020年   19篇
  2019年   16篇
  2018年   20篇
  2017年   20篇
  2016年   19篇
  2015年   18篇
  2014年   33篇
  2013年   39篇
  2012年   23篇
  2011年   24篇
  2010年   38篇
  2009年   39篇
  2008年   51篇
  2007年   38篇
  2006年   43篇
  2005年   33篇
  2004年   46篇
  2003年   38篇
  2002年   49篇
  2001年   31篇
  2000年   38篇
  1999年   31篇
  1998年   23篇
  1997年   20篇
  1996年   22篇
  1995年   29篇
  1994年   44篇
  1993年   33篇
  1992年   28篇
  1991年   27篇
  1990年   27篇
  1989年   31篇
  1988年   32篇
  1987年   19篇
  1986年   36篇
  1985年   27篇
  1984年   35篇
  1983年   14篇
  1982年   14篇
  1981年   12篇
  1980年   14篇
  1979年   12篇
  1978年   14篇
  1977年   10篇
  1976年   11篇
  1975年   8篇
  1974年   8篇
  1971年   8篇
排序方式: 共有1321条查询结果,搜索用时 15 毫秒
141.
An oligohalobic peritrichous ciliate, Epistylis chlorelligerum Shen, 1980, was collected from a ditch in Hangzhou, China. The morphology, oral infraciliature, and morphogenesis of the species were studied using living and protargol-impregnated specimens. Zooids of E. chlorelligerum are 160-230 × 50-60 μm in vivo, and characterized by green-colored endoplasm containing symbiotic algae. The oral infraciliature presents a well-developed filamentous reticulum linked to the circular fiber of the cytostome; the outer two rows of P3 extend adstomally over P1 and usually enfold it. During binary fission, one daughter cell inherits most part of the old buccal apparatus and the reorganized haplokinety and germinal kinety (Hk' and G'), and new buccal apparatus of the other daughter cell is mostly developed from the original germinal kinety (G) and haplokinety (Hk): new peniculi 2, 3 (2P2, 2P3), new haplokinety (2Hk), and new germinal kinety (2G) are formed from G, while the new peniculus 1 (2P1) and its peristomial extention (2Pk) originate from Hk. The epistomial membrane can be observed until the two sets of buccal apparatus begin to separate from each other.  相似文献   
142.
In the present work we report the variation in swimming speed ofVibrio cholerae with respect to the change in concentration of sodium ions in the medium. We have also studied the variation in swimming speed with respect to temperature. We find that the swimming speed initially shows a linear increase with the increase of the sodium ions in the medium and then plateaus. The range within which the swimming speed attains saturation is approximately the same at different temperatures.  相似文献   
143.
Crithidia fasciculata is a trypanosomatid flagellate that parasitizes several species of mosquito. Within the alimentary tract of its host, C. fasciculata exists in two forms: one is a non-motile form, attached in clusters to the lining of the gut, the other a more elongated form swimming freely in the gut lumen. We have developed an in vitro culture system that reproduces the appearance of these two distinct morphological forms. Using two different cultivation methods, shaking and stationary incubations, we have demonstrated that adherence phenotypes are growth-phase dependent. Organisms in the logarithmic phase of growth possess the ability to adhere to substrates; this ability is lost when the organism enters a stationary growth phase. Parasite adherence was independent of cultivation method or substrate. Furthermore, adherent forms of Crithidia maintained their adhesive properties following their removal from substrates. Our data reveal a growth-phase-regulated process of cell attachment that may influence the transmission and dissemination of this parasitic flagellate.  相似文献   
144.
We recently showed that oxysterol-binding protein (OSBP), one of twelve related PH domain containing proteins with lipid and sterol binding activity, interacts with VAMP-associated protein (VAP)-A on the endoplasmic reticulum (ER). In addition to OSBP, seven OSBP-related proteins (ORPs) bind VAP-A via a conserved E-F/Y-F/Y-DA 'FFAT' motif. We focused on this interaction for ORP9, which is expressed as a full-length (ORP9L) or truncated version missing the PH domain (ORP9S). Mutation analysis showed that the interaction required the ORP9 FFAT motif and the N-terminal conserved domain of VAP. Endogenous ORP9L displayed Golgi localization, which was partially mediated by the PH domain based on limited localization of OPR9-PH-GFP with the Golgi apparatus. When inducibly overexpressed, ORP9S and ORP9L colocalized with VAP-A and caused vacuolation of the ER as well as retention of the ER-Golgi intermediate compartment marker ERGIC-53/p58 in the ER. ORP9L mutated in the VAP-A binding domain (ORP9L-FY-->AA) did not localize to the ER but appeared with giantin and Sec31 on large vesicular structures, suggesting the presence of a hybrid Golgi-COPII compartment. Normal Golgi localization was also observed for ORP9L-FY-->AA. Results show that VAP binding and PH domains target ORP9 to the ER and a Golgi-COPII compartment, respectively, and that ORP9L overexpression in these compartments severely perturbed their organization.  相似文献   
145.
Cyst wall proteins 1 and 2 (CWP1 and CWP2) are major constituents of the giardial cyst wall and are expressed with similar kinetics by encysting trophozoites. In the present study, we were interested to determine if the expression of giardial CWPs as heterologous proteins in a higher eukaryotic cell would result in their trafficking across the secretory pathway, as is the case in encysting trophozoites. Recombinant (r)CWP1 and rPro-CWP2 were detected in the lysate and culture media of transfected HEK-293 cells. We then conducted intracellular localization experiments using confocal microscopy and found that the proteins were trafficked in membrane enclosed vesicles across the secretory pathway and released to the culture medium by transfected HEK-293 cells. We then dissected the rCWP1 and rPro-CWP2 molecules to identify the portion(s) responsible for their secretion and found that the putative N-terminal signal peptide was sufficient for directing the secretion of rCWP1, while both the putative N-terminal signal peptide and the 13kDa C-terminal regions were necessary for the secretion of rPro-CWP2 by transfected HEK-293 cells. Taken together, these results demonstrate the degree of conservation of signal peptide recognition between lower and higher eukaryotes.  相似文献   
146.
147.
The mechanisms of secretory transport through the Golgi apparatus remain an issue of debate. The precise functional importance of calcium ions (Ca2+) for intra-Golgi transport has also been poorly studied. Here, using different approaches to measure free Ca2+ concentrations in the cell cytosol ([Ca2+]cyt) and inside the lumen of the Golgi apparatus ([Ca2+]GA), we have revealed transient increases in [Ca2+]cyt during the late phase of intra-Golgi transport that are concomitant with a decline in the maximal [Ca2+]GA restoration ability. Thus, this redistribution of Ca2+ from the Golgi apparatus into the cytosol during the movement of cargo through the Golgi apparatus appears to have a role in intra-Golgi transport, and mainly in the late Ca2+-dependent phase of SNARE-regulated fusion of Golgi compartments.  相似文献   
148.
MotA and MotB form the proton-channel complex of the proton-driven bacterial flagellar motor. A plug segment of Escherichia coli MotB suppresses proton leakage through the MotA/B complex when it is not assembled into the motor. Using a ratiometric pH indicator protein, pHluorin, we show that the proton-conductivity of a Salmonella MotA/B complex not incorporated into the motor is two orders of magnitude lower than that of a complex that is incorporated and activated. This leakage is, however, significant enough to change the cytoplasmic pH to a level at which the chemotaxis signal transduction system responds.  相似文献   
149.
L-arginine has attracted a great deal of attention as an agent for refolding denatured proteins, and the mildness of its effects offer hope for a wide range of potential applications for this substance, including medicines with few side effects. We report that both L- and D-arginine inhibits Na+-driven flagellar motors of alkaliphilic Bacillus by competing with Na+, which we take as evidence that arginine specifically binds to a molecular target.  相似文献   
150.
In vertebrate cells, the centrosome consists of a pair of centrioles and surrounding pericentriolar material. Using anti-Golgi 58K protein antibodies that recognize formiminotransferase cyclodeaminase (FTCD), we investigated its localization to the centrosome in various cultured cells and human oviductal secretory cells by immunohistochemistry. In addition to the Golgi apparatus, FTCD was localized to the centrosome, more abundantly around the mother centriole. The centrosome localization of FTCD continued throughout the cell cycle and was not disrupted after Golgi fragmentation, which was induced by colcemid and brefeldin A. Centriole microtubules are polyglutamylated and stable against tubulin depolymerizing drugs. FTCD in the centrosome may be associated with polyglutamylated residues of centriole microtubules and may play a role in providing centrioles with glutamate produced by cyclodeaminase domains of FTCD.  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