全文获取类型
收费全文 | 1469篇 |
免费 | 244篇 |
出版年
2021年 | 30篇 |
2020年 | 12篇 |
2016年 | 17篇 |
2015年 | 39篇 |
2014年 | 31篇 |
2013年 | 51篇 |
2012年 | 71篇 |
2011年 | 63篇 |
2010年 | 34篇 |
2009年 | 43篇 |
2008年 | 45篇 |
2007年 | 76篇 |
2006年 | 49篇 |
2005年 | 61篇 |
2004年 | 52篇 |
2003年 | 54篇 |
2002年 | 43篇 |
2001年 | 49篇 |
2000年 | 53篇 |
1999年 | 29篇 |
1998年 | 26篇 |
1997年 | 25篇 |
1996年 | 21篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 18篇 |
1992年 | 31篇 |
1991年 | 29篇 |
1990年 | 35篇 |
1989年 | 28篇 |
1988年 | 28篇 |
1987年 | 34篇 |
1986年 | 16篇 |
1985年 | 31篇 |
1984年 | 17篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 23篇 |
1978年 | 26篇 |
1977年 | 25篇 |
1976年 | 19篇 |
1975年 | 25篇 |
1974年 | 25篇 |
1973年 | 31篇 |
1972年 | 20篇 |
1970年 | 12篇 |
1969年 | 14篇 |
1968年 | 11篇 |
排序方式: 共有1713条查询结果,搜索用时 31 毫秒
901.
Agnese Serafini Lendl Tan Stuart Horswell Steven Howell Daniel J. Greenwood Deborah M. Hunt Minh‐Duy Phan Mark Schembri Mercedes Monteleone Christine R. Montague Warwick Britton Acely Garza‐Garcia Ambrosius P. Snijders Brian VanderVen Maximiliano G. Gutierrez Nicholas P. West Luiz Pedro S. de Carvalho 《Molecular microbiology》2019,112(4):1284-1307
902.
Zhou Shijie Kolding Jeppe Garcia Serge M. Plank Michael J. Bundy Alida Charles Anthony Hansen Cecilie Heino Mikko Howell Daniel Jacobsen Nis S. Reid David G. Rice Jake C. van Zwieten Paul A. M. 《Reviews in Fish Biology and Fisheries》2019,29(3):711-733
Reviews in Fish Biology and Fisheries - Balanced harvest has been proposed to reduce fishing impact on ecosystems while simultaneously maintaining or even increasing fishery yield. The concept has... 相似文献
903.
Clinical expression of Leber hereditary optic neuropathy is affected by the mitochondrial DNA-haplogroup background 下载免费PDF全文
Hudson G Carelli V Spruijt L Gerards M Mowbray C Achilli A Pyle A Elson J Howell N La Morgia C Valentino ML Huoponen K Savontaus ML Nikoskelainen E Sadun AA Salomao SR Belfort R Griffiths P Man PY de Coo RF Horvath R Zeviani M Smeets HJ Torroni A Chinnery PF 《American journal of human genetics》2007,81(2):228-233
Leber hereditary optic neuropathy (LHON) is due primarily to one of three common point mutations of mitochondrial DNA (mtDNA), but the incomplete penetrance implicates additional genetic or environmental factors in the pathophysiology of the disorder. Both the 11778G-->A and 14484T-->C LHON mutations are preferentially found on a specific mtDNA genetic background, but 3460G-->A is not. However, there is no clear evidence that any background influences clinical penetrance in any of these mutations. By studying 3,613 subjects from 159 LHON-affected pedigrees, we show that the risk of visual failure is greater when the 11778G-->A or 14484T-->C mutations are present in specific subgroups of haplogroup J (J2 for 11778G-->A and J1 for 14484T-->C) and when the 3460G-->A mutation is present in haplogroup K. By contrast, the risk of visual failure is significantly less when 11778G-->A occurs in haplogroup H. Substitutions on MTCYB provide an explanation for these findings, which demonstrate that common genetic variants have a marked effect on the expression of an ostensibly monogenic mtDNA disorder. 相似文献
904.
The soil yeast Lipomyces starkeyi (NCYC 1436) secretes dextranase activity into the growth medium. Resolution of a dextranase-active protein fraction by SDS-PAGE
produced three protein bands, of 66 kDa, 68 kDa and 78 kDa, and isoelectric focusing of the same fraction resulted in seven
protein bands, of pIs 3.50, 3.85, 4.20, 4.80, 4.85, 5.00 and 5.30. Dextranase activity was demonstrated for all the isoelectric
forms, and for the 78 kDa species in the presence of SDS. Amino acid compositions of the 66 kDa, 68 kDa and 78 kDa protein
bands were determined, and the N-termini of the 66 kDa and 78 kDa protein bands were sequenced: the first two amino acids
at the N-terminus of each protein were alanine and valine, respectively; an alanine-valine pair is seen early in the N-terminal
coding sequences of the dextranases and the isopullulanase produced by the phylogenetically disparate organisms contributing
to glycosyl hydrolase family 49. 相似文献
905.
906.
Reimers CE Stecher HA Westall JC Alleau Y Howell KA Soule L White HK Girguis PR 《Applied and environmental microbiology》2007,73(21):7029-7040
The decomposition of marine plankton in two-chamber, seawater-filled microbial fuel cells (MFCs) has been investigated and related to resulting chemical changes, electrode potentials, current efficiencies, and microbial diversity. Six experiments were run at various discharge potentials, and a seventh served as an open-circuit control. The plankton consisted of a mixture of freshly captured phytoplankton and zooplankton (0.21 to 1 mm) added at an initial batch concentration of 27.5 mmol liter(-1) particulate organic carbon (OC). After 56.7 days, between 19.6 and 22.2% of the initial OC remained, sulfate reduction coupled to OC oxidation accounted for the majority of the OC that was degraded, and current efficiencies (of the active MFCs) were between 11.3 and 15.5%. In the open-circuit control cell, anaerobic plankton decomposition (as quantified by the decrease in total OC) could be modeled by three terms: two first-order reaction rate expressions (0.79 day(-1) and 0.037 day(-1), at 15 degrees C) and one constant, no-reaction term (representing 10.6% of the initial OC). However, in each active MFC, decomposition rates increased during the third week, lagging just behind periods of peak electricity generation. We interpret these decomposition rate changes to have been due primarily to the metabolic activity of sulfur-reducing microorganisms at the anode, a finding consistent with the electrochemical oxidization of sulfide to elemental sulfur and the elimination of inhibitory effects of dissolved sulfide. Representative phylotypes, found to be associated with anodes, were allied with Delta-, Epsilon-, and Gammaproteobacteria as well as the Flavobacterium-Cytophaga-Bacteroides and Fusobacteria. Based upon these results, we posit that higher current efficiencies can be achieved by optimizing plankton-fed MFCs for direct electron transfer from organic matter to electrodes, including microbial precolonization of high-surface-area electrodes and pulsed flowthrough additions of biomass. 相似文献
907.
Alysia Birkholz Marek Nem?ovi? Esther Dawen Yu Enrico Girardi Jing Wang Archana Khurana Nora Pauwels Elisa Farber Sampada Chitale Richard W. Franck Moriya Tsuji Amy Howell Serge Van Calenbergh Mitchell Kronenberg Dirk M. Zajonc 《The Journal of biological chemistry》2015,290(28):17206-17217
The ability of different glycosphingolipids (GSLs) to activate type I natural killer T cells (NKT cells) has been known for 2 decades. The possible therapeutic use of these GSLs has been studied in many ways; however, studies are needed in which the efficacy of promising GSLs is compared under identical conditions. Here, we compare five unique GSLs structurally derived from α-galactosylceramide. We employed biophysical and biological assays, as well as x-ray crystallography to study the impact of the chemical modifications of the antigen on type I NKT cell activation. Although all glycolipids are bound by the T cell receptor of type I NKT cells in real time binding assays with high affinity, only a few activate type I NKT cells in in vivo or in vitro experiments. The differences in biological responses are likely a result of different pharmacokinetic properties of each lipid, which carry modifications at different parts of the molecule. Our results indicate a need to perform a variety of assays to ascertain the therapeutic potential of type I NKT cell GSL activators. 相似文献
908.
John C. Whitney Gregory B. Whitfield Lindsey S. Marmont Patrick Yip A. Mirela Neculai Yuri D. Lobsanov Howard Robinson Dennis E. Ohman P. Lynne Howell 《The Journal of biological chemistry》2015,290(20):12451-12462
Pseudomonas aeruginosa is an opportunistic human pathogen that secretes the exopolysaccharide alginate during infection of the respiratory tract of individuals afflicted with cystic fibrosis and chronic obstructive pulmonary disease. Among the proteins required for alginate production, Alg44 has been identified as an inner membrane protein whose bis-(3′,5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) binding activity post-translationally regulates alginate secretion. In this study, we report the 1.8 Å crystal structure of the cytoplasmic region of Alg44 in complex with dimeric self-intercalated c-di-GMP and characterize its dinucleotide-binding site using mutational analysis. The structure shows that the c-di-GMP binding region of Alg44 adopts a PilZ domain fold with a dimerization mode not previously observed for this family of proteins. Calorimetric binding analysis of residues in the c-di-GMP binding site demonstrate that mutation of Arg-17 and Arg-95 alters the binding stoichiometry between c-di-GMP and Alg44 from 2:1 to 1:1. Introduction of these mutant alleles on the P. aeruginosa chromosome show that the residues required for binding of dimeric c-di-GMP in vitro are also required for efficient alginate production in vivo. These results suggest that the dimeric form of c-di-GMP represents the biologically active signaling molecule needed for the secretion of an important virulence factor produced by P. aeruginosa. 相似文献
909.
The construction of a large dendritic arbor requires robust growth and the precise delivery of membrane and protein cargoes to specific subcellular regions of the developing dendrite. How the microtubule-based vesicular trafficking and sorting systems are regulated to distribute these dendritic development factors throughout the dendrite is not well understood. Here we identify the small GTPase RAB-10 and the exocyst complex as critical regulators of dendrite morphogenesis and patterning in the C. elegans sensory neuron PVD. In rab-10 mutants, PVD dendritic branches are reduced in the posterior region of the cell but are excessive in the distal anterior region of the cell. We also demonstrate that the dendritic branch distribution within PVD depends on the balance between the molecular motors kinesin-1/UNC-116 and dynein, and we propose that RAB-10 regulates dendrite morphology by balancing the activity of these motors to appropriately distribute branching factors, including the transmembrane receptor DMA-1. 相似文献
910.