全文获取类型
收费全文 | 768篇 |
免费 | 80篇 |
专业分类
848篇 |
出版年
2023年 | 7篇 |
2022年 | 19篇 |
2021年 | 24篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 31篇 |
2017年 | 19篇 |
2016年 | 24篇 |
2015年 | 53篇 |
2014年 | 56篇 |
2013年 | 58篇 |
2012年 | 72篇 |
2011年 | 62篇 |
2010年 | 54篇 |
2009年 | 29篇 |
2008年 | 38篇 |
2007年 | 45篇 |
2006年 | 30篇 |
2005年 | 29篇 |
2004年 | 34篇 |
2003年 | 27篇 |
2002年 | 20篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1954年 | 1篇 |
1935年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有848条查询结果,搜索用时 15 毫秒
91.
92.
Hommelgaard AM Roepstorff K Vilhardt F Torgersen ML Sandvig K van Deurs B 《Traffic (Copenhagen, Denmark)》2005,6(9):720-724
The role of caveolae in endocytosis is hotly debated. Here, we argue that most caveolae are stable microdomains at the cell surface. Only a small fraction of caveolae is constitutively internalized, leading to a quantitatively minor uptake of ligands and receptors. In addition, we suggest that a more pronounced downregulation of caveolae from the plasma membrane can occur, presumably stimulated by receptor cross-linking and clustering in caveolae. Finally, we propose that future studies dealing with internalization of caveolae should actually document such internalization and include kinetic data. 相似文献
93.
Sommer F Drepper F Haehnel W Hippler M 《The Journal of biological chemistry》2004,279(19):20009-20017
On the lumenal side of photosystem I (PSI), each of the two large core subunits, PsaA and PsaB, expose a conserved tryptophan residue to the surface. PsaB-Trp(627) is part of the hydrophobic recognition site that is essential for tight binding of the two electron donors plastocyanin and cytochrome c(6) to the donor side of PSI (Sommer, F., Drepper, F., and Hippler, M. (2002) J. Biol. Chem. 277, 6573-6581). To examine the function of PsaA-Trp(651) in binding and electron transfer of both donors to PSI, we generated the mutants PsaA-W651F and PsaA-W651S by site-directed mutagenesis and biolistic transformation of Chlamydomonas reinhardtii. The protein-protein interaction and the electron transfer between the donors and PSI isolated from the mutants were analyzed by flash absorption spectroscopy. The mutation PsaA-W651F completely abolished the formation of a first order electron transfer complex between plastocyanin (pc) and the altered PSI and increased the dissociation constant for binding of cytochrome (cyt) c(6) by more than a factor of 10 as compared with wild type. Mutation of PsaA-Trp(651) to Ser had an even larger impact on the dissociation constant. The K(D) value increased another 2-fold when the values obtained for the interaction and electron transfer between cyt c(6) and PSI from PsaA-W651S and PsaA-W651F are compared. In contrast, binding and electron transfer of pc to PSI from PsaA-W651S improved as compared with PSI from PsaA-W651F and admitted the formation of an inter-molecular electron transfer complex, resulting in a K(D) value of about 554 microm that is still five times higher than observed for wild type. These results demonstrate that PsaA-Trp(651) is, such as PsaB-Trp(627), crucial for high affinity binding of pc and cyt c(6) to PSI. Our results also indicate that the highly conserved structural recognition motif that is formed by PsaA-Trp(651) and PsaB-Trp(627) confers a differential selectivity in binding of both donors to PSI. 相似文献
94.
This report describes a case series of septicaemia caused by infection with Aerococcus viridans in immunodeficient NOD/LtSz-Prkdc(scid) (NOD/SCID) mice. During a period of 3 weeks more than 40 animals died or became ill with clinical signs of ruffled coat, weight loss, laboured breeding, and distended abdomen. At necropsy it was found that the animals displayed symptoms of sepsis with widespread abscesses in the liver, heart, lungs or pyogenic peritonitis. A Gram-positive coccus was isolated in pure culture from the abscesses or peritoneum from affected animals. According to phenotypic and phylogenetic characterization, the isolate was identified as A. viridans. This is the first report of a spontaneous outbreak of septicaemia caused by A. viridans infection in immunodeficient laboratory mice and we conclude that A. viridans should be considered as a pathogen in immunodeficient mice. 相似文献
95.
Joke Hollants Frederik Leliaert Olivier De Clerck Anne Willems 《Symbiosis (Philadelphia, Pa.)》2010,51(1):131-138
In the search for endosymbiotic bacteria, elimination of ectosymbionts is a key point of attention. Commonly, the surface
of the host itself or the symbiotic structures are sterilized with aggressive substances such as chlorine or mercury derivatives.
Although these disinfectants are adequate to treat many species, they are not suitable for surface sterilization of delicate
samples. In order to study the bacterial endosymbionts in the marine green alga Bryopsis, the host plant’s cell wall was mechanically, chemically and enzymatically cleaned. Merely a chemical and enzymatic approach
proved to be highly effective. Bryopsis thalli treated with cetyltrimethylammonium bromide (CTAB) lysis buffer, proteinase K and bactericidal cleanser Umonium Master
showed no bacterial growth on agar plates or bacterial fluorescence when stained with a DNA fluorochrome. Moreover, the algal
cells were intact after sterilization, suggesting endophytic DNA is still present within these algae. This new surface sterilization
procedure opens the way to explore endosymbiotic microbial communities of other, even difficult to handle, samples. 相似文献
96.
Sara Vander Borght Louis Libbrecht Aezam Katoonizadeh Jos van Pelt David Cassiman Frederik Nevens Alfons Van Lommel Bryon E Petersen Johan Fevery Peter L Jansen Tania A Roskams 《The journal of histochemistry and cytochemistry》2006,54(9):1051-1059
Breast cancer resistance protein (BCRP/ABCG2) is an ATP-binding cassette transport protein that is expressed in several organs including the liver. Previous studies have shown that ABC transport proteins play an important pathophysiological role in several liver diseases. However, to date, expression pattern and possible role of BCRP in human liver diseases and animal models have not been studied in detail. Here we investigated the expression pattern of BCRP in normal liver, chronic parenchymal and biliary human liver diseases, and parallel in different rat models of liver diseases. Expression was studied by immunohistochemistry and additionally by RT-PCR analysis in Thy-1-positive rat oval cells. Bile ducts, hepatic progenitor cells, reactive bile ductules, and blood vessel endothelium were immunoreactive for BCRP in normal liver and all types of human liver diseases and in rat models. BCRP was expressed by the canalicular membrane of hepatocytes in normal and diseased human liver, but never in rat liver. Remarkably, there was also expression of BCRP at the basolateral pole of human hepatocytes, and this was most pronounced in chronic biliary diseases. In conclusion, BCRP positivity in the progenitor cells/reactive ductules could contribute to the resistance of these cells to cytotoxic agents and xenotoxins. Basolateral hepatocytic expression in chronic biliary diseases may be an adaptive mechanism to pump bile constituents back into the sinusoidal blood. Strong differences between human and rat liver must be taken into account in future studies with animal models. 相似文献
97.
Niessen RC Sijmons RH Ou J Olthof SG Osinga J Ligtenberg MJ Hogervorst FB Weiss MM Tops CM Hes FJ de Bock GH Buys CH Kleibeuker JH Hofstra RM 《Human genetics》2006,119(1-2):206-211
Biallelic germline mutations of MUTYH—a gene encoding a base excision repair protein—are associated with an increased susceptibility of colorectal cancer. Whether
monoallelic MUTYH mutations also increase cancer risk is not yet clear, although there is some evidence suggesting a slight increase of risk.
As the MUTYH protein interacts with the mismatch repair (MMR) system, we hypothesised that the combination of a monoallelic
MUTYH mutation with an MMR gene mutation increases cancer risk. We therefore investigated the prevalence of monoallelic MUTYH mutations in carriers of a germline MMR mutation: 40 carriers of a truncating mutation (group I) and 36 of a missense mutation
(group II). These patients had been diagnosed with either colorectal or endometrial cancer. We compared their MUTYH mutation frequencies with those observed in a group of 134 Dutch colorectal and endometrial cancer patients without an MMR
gene mutation (0.7%) and those reported for Caucasian controls (1.5%). In group I one monoallelic MUTYH mutation was found (2.5%). In group II five monoallelic germline MUTYH mutations were found (14%), four of them in MSH6 missense mutation carriers (20%). Of all patients with an MMR gene mutation, only those with a missense mutation showed a
significantly higher frequency of (monoallelic) MUTYH mutations than the Dutch cancer patients without MMR gene mutations (P=0.002) and the published controls (P=0.001). These results warrant further study to test the hypothesis of mutations in MMR genes (in particular MSH6) and MUTYH acting together to increase cancer risk. 相似文献
98.
Neumüller RA Wirtz-Peitz F Lee S Kwon Y Buckner M Hoskins RA Venken KJ Bellen HJ Mohr SE Perrimon N 《Genetics》2012,190(3):931-940
In Drosophila collections of green fluorescent protein (GFP) trap lines have been used to probe the endogenous expression patterns of trapped genes or the subcellular localization of their protein products. Here, we describe a method, based on nonoverlapping, highly specific, shRNA transgenes directed against GFP, that extends the utility of these collections to loss-of-function studies. Furthermore, we used a MiMIC transposon to generate GFP traps in Drosophila cell lines with distinct subcellular localization patterns, which will permit high-throughput screens using fluorescently tagged proteins. Finally, we show that fluorescent traps, paired with recombinant nanobodies and mass spectrometry, allow the study of endogenous protein complexes in Drosophila. 相似文献
99.
Grimm KS Klupp BG Granzow H Müller FM Fuchs W Mettenleiter TC 《Journal of virology》2012,86(12):6512-6521
Herpesvirus nucleocapsids are translocated from their assembly site in the nucleus to the cytosol by acquisition of a primary envelope at the inner nuclear membrane which subsequently fuses with the outer nuclear membrane. This transport through the nuclear envelope requires homologs of the conserved herpesviral pUL31 and pUL34 proteins which form the nuclear egress complex (NEC). In its absence, 1,000-fold less virus progeny is produced. We isolated a UL34-negative mutant of the alphaherpesvirus pseudorabies virus (PrV), PrV-ΔUL34Pass, which regained replication competence after serial passages in cell culture by inducing nuclear envelope breakdown (NEBD) (B. G. Klupp, H. Granzow, and T. C. Mettenleiter, J. Virol. 85:8285-8292, 2011). To test whether this phenotype is unique, passaging experiments were repeated with a UL31 deletion mutant. After 60 passages, the resulting PrV-ΔUL31Pass replicated similarly to wild-type PrV. Ultrastructural analyses confirmed escape from the nucleus via NEBD, indicating an inherent genetic disposition in herpesviruses. To identify the mutated viral genes responsible for this phenotype, the genome of PrV-ΔUL34Pass was sequenced and compared to the genomes of parental PrV-Ka and PrV-ΔUL34. Targeted sequencing of PrV-ΔUL31Pass disclosed congruent mutations comprising genes encoding tegument proteins (pUL49, pUL46, pUL21, pUS2), envelope proteins (gI, pUS9), and protease pUL26. To investigate involvement of cellular pathways, different inhibitors of cellular kinases were tested. While induction of apoptosis or inhibition of caspases had no specific effect on the passaged mutants, roscovitine, a cyclin-dependent kinase inhibitor, and U0126, an inhibitor of MEK1/2, specifically impaired replication of the passaged mutants, indicating involvement of mitosis-related processes in herpesvirus-induced NEBD. 相似文献
100.
The plant pathogen Fusarium graminearum is the infamous cause of Fusarium head blight worldwide resulting in significant losses of yield and reduced grain feed quality. It also has the potential to produce a range of small bioactive peptides produced by the non ribosomal peptide synthetases (NRPSs). Most of these are unknown as F. graminearum contains 19 NRPS encoding genes, but only three have been assigned products. For the first time, we use deletion and overexpression mutants to investigate the functions and product of NRPS4 in F. graminearum. Deletion of NRPS4 homologues in Alternaria brassicicola and Cochloibolus heterostrophus has been shown to result in mutants unable to repel water. In a time study of surface hydrophobicity we observed that water droplets could penetrate 7 d old colonies of the NRPS4 deletion mutants. Loss in ability to repel water was first observed on 13 d old cultures of the wild type strain, whereas the overexpression strain remained water repellant throughout the 38 d time study. The conidia of both mutants were examined and those of the overexpression mutant showed distinct morphological differences in form of collapsed cells. These observations might suggest that the peptide product of NRPS4 could be an architectural factor in the cell walls of Fusarium or an indirect regulator of hydrophobicity. 相似文献