全文获取类型
收费全文 | 1399篇 |
免费 | 117篇 |
国内免费 | 1篇 |
出版年
2022年 | 8篇 |
2021年 | 28篇 |
2020年 | 21篇 |
2019年 | 22篇 |
2018年 | 23篇 |
2017年 | 22篇 |
2016年 | 35篇 |
2015年 | 63篇 |
2014年 | 75篇 |
2013年 | 89篇 |
2012年 | 102篇 |
2011年 | 89篇 |
2010年 | 77篇 |
2009年 | 70篇 |
2008年 | 93篇 |
2007年 | 88篇 |
2006年 | 71篇 |
2005年 | 71篇 |
2004年 | 66篇 |
2003年 | 71篇 |
2002年 | 47篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1995年 | 5篇 |
1992年 | 5篇 |
1988年 | 6篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1973年 | 6篇 |
1969年 | 5篇 |
1967年 | 5篇 |
1965年 | 7篇 |
1962年 | 6篇 |
1956年 | 6篇 |
1938年 | 4篇 |
1936年 | 5篇 |
1927年 | 7篇 |
1926年 | 4篇 |
1920年 | 5篇 |
1917年 | 4篇 |
1908年 | 5篇 |
排序方式: 共有1517条查询结果,搜索用时 203 毫秒
121.
The intra-annual variability of soft-bottom macrobenthos abundance patterns in the North Channel of the Seine estuary 总被引:2,自引:0,他引:2
Nicolas Desroy Anne-Laure Janson Lionel Denis Gregory Charrier Sandric Lesourd Jean-Claude Dauvin 《Hydrobiologia》2007,588(1):173-188
Temporal and spatial variability of the Abra alba–Pectinaria koreni and Macoma balthica communities was examined in the northern part of the Seine estuary (North Channel) over different space and time scales in
order to assess the role that the hydrologic regime and/or anthropogenic influences play in defining benthic communities over
time. Sediment in the North Channel displayed strong spatial and temporal variability, sustained by intense sediment transport
episodes. Total macrobenthic abundances ranged widely on the course of the year and there was no evidence of a seasonal signal
for the density fluctuations, whatever the spatial scale considered. The bio-sedimentary dynamics can be divided into two
periods: the first corresponds to the high flow rate period (January–May) during which fauna is influenced by fine silt/clay
deposition, and the second to the low flow rate period (June–December) during which sandy deposits prevail. Despite the absence
of significant correlations between sediment composition and abundance, episodes of sediment transport seem to be an important
structuring mechanism in the Seine estuary. As a consequence, the faunal composition varied throughout the year. The winter
and spring fauna, characterised by species living on muddy fine-sands or muds, were enriched during the summer and autumn
by species living in clean fine sand, such as Donax vittatus, Nephtys cirrosa or Spio decoratus, mainly represented by adult individuals. Secondary settlement of drifters may explain the rapid structuration of assemblages
a few days after the sandy deposits. Our results suggest the importance of the bentho-pelagic coupling, primarily induced
by the sedimentary instability, on the macrobenthic fauna dynamics. The intra-annual variability of assemblages at the mouth
of the Seine river and the silted situation of the North Channel might simply be the result of the silting up and alteration
of the inner estuary, generated by several decades of man-made modifications and natural processes. 相似文献
122.
Identification of the L,D-transpeptidases responsible for attachment of the Braun lipoprotein to Escherichia coli peptidoglycan
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Magnet S Bellais S Dubost L Fourgeaud M Mainardi JL Petit-Frère S Marie A Mengin-Lecreulx D Arthur M Gutmann L 《Journal of bacteriology》2007,189(10):3927-3931
The L,D-transpeptidase Ldt(fm) catalyzes peptidoglycan cross-linking in beta-lactam-resistant mutant strains of Enterococcus faecium. Here, we show that in Escherichia coli Ldt(fm) homologues are responsible for the attachment of the Braun lipoprotein to murein, indicating that evolutionarily related domains have been tailored to use muropeptides or proteins as acyl acceptors in the L,D-transpeptidation reaction. 相似文献
123.
A biosensor for the electrical detection of human antibodies from serum has been fabricated and experimentally demonstrated. The device is based on the immobilization of proteins used as probes between a set of microelectrodes. Incubation with diluted human serum was followed by incubation with anti-human secondary antibodies labeled with gold nanoparticles (GNPs) and then precipitation of silver on the nanoparticles. The output of the device was defined as the percentage of short-circuited microelectrodes after silver deposition independently of the gap conductance. Two model probes were studied: protein A and goat antibodies. The effects of the microgap spacing (5, 10, 15 or 20 microm) and the duration of the silver treatment were examined. The data obtained showed that a large spacing (20 microm) led to poor sensitivity. Alternately, 5 microm gaps led to high sensitivity and saturation of the signal. Interestingly, 10-15 microm gaps enabled a non-saturated and distinct signal for both probes that was correlated with the GNP density between the microgaps as determined by atomic force microscopy. Different capture efficiencies could be easily distinguished. The biosensor described here is easy to use and thus can be applied to real detection experiments. 相似文献
124.
Biros SM Moisan L Mann E Carella A Zhai D Reed JC Rebek J 《Bioorganic & medicinal chemistry letters》2007,17(16):4641-4645
The design and synthesis of alpha-helix peptidomimetics using inverse electron demand Diels-Alder reactions is described. The potency of the resulting pyridazine-based library to disrupt the Bak/Bcl-X(L) interaction was tested using an in vitro fluorescence polarization assay. 相似文献
125.
Orlandi-Pradines E Almeras L Denis de Senneville L Barbe S Remoué F Villard C Cornelie S Penhoat K Pascual A Bourgouin C Fontenille D Bonnet J Corre-Catelin N Reiter P Pagés F Laffite D Boulanger D Simondon F Pradines B Fusaï T Rogier C 《Microbes and infection / Institut Pasteur》2007,9(12-13):1454-1462
Exposure to vectors of infectious diseases has been associated with antibody responses against salivary antigens of arthropods among people living in endemic areas. This immune response has been proposed as a surrogate marker of exposure to vectors appropriate for evaluating the protective efficacy of antivectorial devices. The existence and potential use of such antibody responses in travellers transiently exposed to Plasmodium or arbovirus vectors in tropical areas has never been investigated. The IgM and IgG antibody responses of 88 French soldiers against the saliva of Anopheles gambiae and Aedes aegypti were evaluated before and after a 5-month journey in tropical Africa. Antibody responses against Anopheles and Aedes saliva increased significantly in 41% and 15% of the individuals, respectively, and appeared to be specific to the mosquito genus. A proteomic and immunoproteomic analysis of anopheles and Aedes saliva allowed for the identification of some antigens that were recognized by most of the exposed individuals. These results suggest that antibody responses to the saliva of mosquitoes could be considered as specific surrogate markers of exposure of travellers to mosquito vectors that transmit arthropod borne infections. 相似文献
126.
Braun T Carvalho G Grosjean J Ades L Fabre C Boehrer S Debili N Fenaux P Kroemer G 《Apoptosis : an international journal on programmed cell death》2007,12(6):1101-1108
Myelodysplastic syndromes (MDS) constitute a preneoplastic condition in which potentially malignant cancer stem cells continuously
die during differentiation. This MDS-associated cell death often involves caspase-3 activation, yet can also occur without
caspase activation, for instance in differentiating megakaryocytes (MK). We investigated, the mechanisms through which MK
from MDS patients undergo premature cell death. While polyploid, mature MK from healthy subjects or MDS patients manifested
caspase-3 activation during terminal differentiation, freshly isolated, immature MK from MDS died without caspase-3 activation.
Similarly, purified bone marrow CD34+ cells from MDS patients that were driven into MK differentiation in vitro died without caspase-3 activation at an immature stage, before polyploidization. The premature death of MDS MK was accompanied
by the mitochondrial release of cytochrome c, Smac/DIABLO and endonuclease G, a caspase-independent death effector, as well loss of the mitochondrial membrane potential
and plasma membrane phosphatidylserine exposure before definitive loss of viability. Thus, a stereotyped pattern of mitochondrial
alterations accompanies differentiation-associated MK death in MDS.
T. Braun and G. Carvalho contributed equally to this paper. 相似文献
127.
Escherichia coli is the most common organism associated with asymptomatic bacteriuria (ABU) in humans. In contrast to uropathogenic E. coli (UPEC) that cause symptomatic urinary tract infection, very little is known about the mechanisms by which these strains colonize the urinary tract. Here, we have investigated the biofilm-forming capacity on abiotic surfaces of groups of ABU strains and UPEC strains in human urine. We found that there is a strong bias; ABU strains were significantly better biofilm formers than UPEC strains. Our data suggest that biofilm formation in urinary tract infectious E. coli seems to be associated with ABU strains and appears to be an important strategy used by these strains for persistence in this high-flow environment. 相似文献
128.
129.
Persistence of long-term memory storage requires a late protein synthesis- and BDNF- dependent phase in the hippocampus 总被引:1,自引:0,他引:1
Persistence is the most characteristic attribute of long-term memory (LTM). To understand LTM, we must understand how memory traces persist over time despite the short-lived nature and rapid turnover of their molecular substrates. It is widely accepted that LTM formation is dependent upon hippocampal de novo protein synthesis and Brain-Derived Neurotrophic Factor (BDNF) signaling during or early after acquisition. Here we show that 12 hr after acquisition of a one-trial associative learning task, there is a novel protein synthesis and BDNF-dependent phase in the rat hippocampus that is critical for the persistence of LTM storage. Our findings indicate that a delayed stabilization phase is specifically required for maintenance, but not formation, of the memory trace. We propose that memory formation and memory persistence share some of the same molecular mechanisms and that recurrent rounds of consolidation-like events take place in the hippocampus for maintenance of the memory trace. 相似文献