全文获取类型
收费全文 | 3272篇 |
免费 | 297篇 |
出版年
2021年 | 38篇 |
2020年 | 29篇 |
2019年 | 20篇 |
2018年 | 39篇 |
2017年 | 28篇 |
2016年 | 67篇 |
2015年 | 104篇 |
2014年 | 107篇 |
2013年 | 139篇 |
2012年 | 183篇 |
2011年 | 207篇 |
2010年 | 146篇 |
2009年 | 127篇 |
2008年 | 204篇 |
2007年 | 203篇 |
2006年 | 210篇 |
2005年 | 162篇 |
2004年 | 172篇 |
2003年 | 165篇 |
2002年 | 173篇 |
2001年 | 46篇 |
2000年 | 54篇 |
1999年 | 51篇 |
1998年 | 44篇 |
1997年 | 55篇 |
1996年 | 47篇 |
1995年 | 49篇 |
1994年 | 36篇 |
1993年 | 27篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 33篇 |
1989年 | 44篇 |
1988年 | 48篇 |
1987年 | 24篇 |
1986年 | 22篇 |
1985年 | 26篇 |
1984年 | 36篇 |
1983年 | 21篇 |
1982年 | 28篇 |
1981年 | 27篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 12篇 |
1977年 | 17篇 |
1976年 | 15篇 |
1975年 | 20篇 |
1972年 | 11篇 |
1969年 | 13篇 |
1968年 | 10篇 |
排序方式: 共有3569条查询结果,搜索用时 31 毫秒
61.
Synaptic Vesicle Traffic: Rush Hour in the Nerve Terminal 总被引:6,自引:0,他引:6
62.
63.
Plant-parasitic nematodes cause devastating agricultural damage worldwide. Only a few synthetic nematicides can be used and their application is limited in fields. Therefore, there is a need for sustainable and environment-friendly alternatives. Nematode-trapping fungi (NTF) are natural predators of nematodes. They capture and digest them with their hyphae and are starting to being used as bio-control agents. In this study, we applied the NTF Arthrobotrys flagrans (Duddingtonia flagrans) against the wine pathogenic nematode Xiphinema index. A. flagrans reduced the number of X. index juveniles in pot cultures of Ficus carica, an alternative host plant for X. index, significantly. Sodium-alginate pellets with A. flagrans spores were produced for vineyard soil inoculation under laboratory conditions. The NTF A. conoides, A. musiformis and A. superba were enriched from several soil samples, showing their natural presence. Trap formation is an energy-consuming process and depends upon various biotic and abiotic stimuli. Here, we show that bacteria of the genus Delftia, Bacillus, Pseudomonas, Enterobacter and Serratia induced trap formation in NTF like A. conoides and A. oligospora but not in A. flagrans in the absence of nematodes. The application of NTF along with such bacteria could be a combinatorial way of efficient biocontrol in nematode-infested soil. 相似文献
64.
Thomas Kinateder Lukas Drexler Kristina Straub Rainer Merkl Reinhard Sterner 《Protein science : a publication of the Protein Society》2023,32(1):e4536
The conservation of fold and chemistry of the enzymes associated with histidine biosynthesis suggests that this pathway evolved prior to the diversification of Bacteria, Archaea, and Eukaryotes. The only exception is the histidinol phosphate phosphatase (HolPase). So far, non-homologous HolPases that possess distinct folds and belong to three different protein superfamilies have been identified in various phylogenetic clades. However, their evolution has remained unknown to date. Here, we analyzed the evolutionary history of the HolPase from γ-Proteobacteria (HisB-N). It has been argued that HisB-N and its closest homologue d -glycero-d -manno-heptose-1,7-bisphosphate 7-phosphatase (GmhB) have emerged from the same promiscuous ancestral phosphatase. GmhB variants catalyze the hydrolysis of the anomeric d -glycero-d -manno-heptose-1,7-bisphosphate (αHBP or βHBP) with a strong preference for one anomer (αGmhB or βGmhB). We found that HisB-N from Escherichia coli shows promiscuous activity for βHBP but not αHBP, while βGmhB from Crassaminicella sp. shows promiscuous activity for HolP. Accordingly, a combined phylogenetic tree of αGmhBs, βGmhBs, and HisB-N sequences revealed that HisB-Ns form a compact subcluster derived from βGmhBs. Ancestral sequence reconstruction and in vitro analysis revealed a promiscuous HolPase activity in the resurrected enzymes prior to functional divergence of the successors. The following increase in catalytic efficiency of the HolP turnover is reflected in the shape and electrostatics of the active site predicted by AlphaFold. An analysis of the phylogenetic tree led to a revised evolutionary model that proposes the horizontal gene transfer of a promiscuous βGmhB from δ- to γ-Proteobacteria where it evolved to the modern HisB-N. 相似文献
65.
66.
Martin Werner Reinhard von Wasielewski Paul Komminoth 《Histochemistry and cell biology》1996,105(4):253-260
In this overview we emphasize new methods of improving immunohistochemical results in formaldehyde-fixed tissue samples. The benefit of heat-induced antigen retrieval in demasking of concealed epitopes is demonstrated. We provide guidance on the influence of heat-induced antigen retrieval in commonly applied monoclonal and polyconal antibodies. Moreover, we show the promising methods of signal amplification using biotinylated tyramine and signal intensification of diaminobenzidine reaction products by metallic ions. 相似文献
67.
68.
Ana María Bravo-Angel Heinz-Albert Becker Reinhard Kunze Barbara Hohn Wen-Hui Shen 《Molecular & general genetics : MGG》1995,248(5):527-534
A reverse genetic system for studying excision of the transposable elementDs1 in maize plants has been established previously. In this system, theDs1 element, as part of the genome of maize streak virus (MSV), is introduced into maize plants via agroinfection. In the presence
of theAc element, excision ofDs1 from the MSV genome results in the appearance of viral symptoms on the maize plants. Here, we used this system to study DNA
sequences requiredin cis for excision ofDs1. TheDs1 element contains theAc transposase binding motif AAACGG in only one of its subterminal regions (defined here as the 5′ subterminal region). We showed
that mutation of these motifs abolished completely the excision capacity ofDs1. This is the first direct demonstration that the transposase binding motifs are essential for excision. Mutagenesis with
oligonucleotide insertions in the other (3′) subterminal region resulted in elements with either a reduced or an increased
excision efficiency, indicating that this subterminal region also has an important function. 相似文献
69.
A focal adhesion factor directly linking intracellularly motile Listeria monocytogenes and Listeria ivanovii to the actin-based cytoskeleton of mammalian cells. 总被引:12,自引:4,他引:8
下载免费PDF全文
![点击此处可从《The EMBO journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
T Chakraborty F Ebel E Domann K Niebuhr B Gerstel S Pistor C J Temm-Grove B M Jockusch M Reinhard U Walter et al. 《The EMBO journal》1995,14(7):1314-1321
The surface-bound ActA polypeptide of the intracellular bacterial pathogen Listeria monocytogenes is the sole listerial factor needed for recruitment of host actin filaments by intracellularly motile bacteria. Here we report that following Listeria infection the host vasodilator-stimulated phosphoprotein (VASP), a microfilament- and focal adhesion-associated substrate of both the cAMP- and cGMP-dependent protein kinases, accumulates on the surface of intracytoplasmic bacteria prior to the detection of F-actin 'clouds'. VASP remains associated with the surface of highly motile bacteria, where it is polarly located, juxtaposed between one extremity of the bacterial surface and the front of the actin comet tail. Since actin filament polymerization occurs only at the very front of the tail, VASP exhibits properties of a host protein required to promote actin polymerization. Purified VASP binds directly to the ActA polypeptide in vitro. A ligand-overlay blot using purified radiolabelled VASP enabled us to identify the ActA homologue of the related intracellular motile pathogen, Listeria ivanovii, as a protein with a molecular mass of approximately 150 kDa. VASP also associates with actin filaments recruited by another intracellularly motile bacterial pathogen, Shigella flexneri. Hence, by the simple expedient of expressing surface-bound attractor molecules, bacterial pathogens effectively harness cytoskeletal components to achieve intracellular movement. 相似文献
70.
Feeding biology of two brachionid rotifers: Brachionus quadridentatus and Brachionus plicatilis 总被引:1,自引:0,他引:1
Brachionus quadridentatus and Brachionus plicatilis were examined in laboratory cultures to investigate their (1) food requirements and (2) ability to select particles on the basis of size. Growth experiments showed that the Chlorophyceans Nannochloris sp. and Chlorella vulgaris possess good nutritional value for these rotifers. However, B. quadridentatus declined in cultures with Microcystis firma, detritus of Enteromorpha sp. or Pseudomonas sp. (bacteria) as a sole source of food, thus indicating that these foods were inadequate. Utilization of latex microspheres by these two species indicate that they respond to particle size in different ways: B. quadridentatus had a higher selectivity index for 3 and 5 µm beads, while B. plicatilis had a higher selectivity index for 2 µm beads. 相似文献