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101.
Parshikov IA Moody JD Heinze TM Freeman JP Williams AJ Sutherland JB 《FEMS microbiology letters》2002,214(1):133-136
The ability of the fungus Beauveria bassiana ATCC 7159 to transform the antibacterial agent cinoxacin was investigated. Cultures in sucrose-peptone broth were dosed with cinoxacin, grown for 20 days, and then extracted with ethyl acetate. Two metabolites were detected and purified by high-performance liquid chromatography. The major metabolite was identified by mass and proton nuclear magnetic resonance spectra as 1-ethyl-1,4-dihydro-3-(hydroxymethyl)[1,3]dioxolo[4,5-g]cinnolin-4-one and the minor metabolite was identified as 1-ethyl-1,4-dihydro-6,7-dihydroxy-3-(hydroxymethyl)cinnolin-4-one. B. bassiana also reduced quinoline-3-carboxylic acid to 3-(hydroxymethyl)quinoline. 相似文献
102.
Lakowicz JR Shen Y D'Auria S Malicka J Fang J Gryczynski Z Gryczynski I 《Analytical biochemistry》2002,301(2):261-277
Metallic surfaces can have unusual effects on fluorophores such as increasing or decreasing the rates of radiative decay and the rates of resonance energy transfer (RET). In the present article we describe the effects of metallic silver island films on the emission spectra, lifetimes, and energy transfer for several fluorophores. The fluorophores are not covalently coupled to the silver islands so that there are a range of fluorophore-to-metal distances. We show that proximity of fluorophores to the silver islands results in increased fluorescence intensity, with the largest enhancement for the lowest-quantum-yield fluorophores. Importantly, the metal-induced increases in intensity are accompanied by decreased lifetimes and increased photostability. These effects demonstrate that the silver islands have increased the radiative decay rates of the fluorophore. For solvent-sensitive fluorophores the emission spectra shifted to shorted wavelengths in the presence of the silver islands, which is consistent with a decrease of the apparent lifetime for fluorophores near the metal islands. We also observed an increased intensity and blue spectral shift for the protein human glyoxalase, which displays a low quantum yield for its intrinsic tryptophan emission. In this case the blue shift is thought to be due to increased emission from a buried low-quantum-yield tryptophan residue. Increased intensities were also observed for the intrinsic emission of the nucleic acid bases adenine and thymine and for single-stranded 15-mers poly(T) and poly(C). And finally, we observed increased RET for donors and acceptors in solution and when bound to double-helical DNA. These results demonstrate that metallic particles can be used to modify the emission from intrinsic and extrinsic fluorophores in biochemical systems. 相似文献
103.
John J. Varga Liliana Losada Adrian M. Zelazny Lauren Brinkac Derek Harkins Diana Radune Jessica Hostetler Elizabeth P. Sampaio Catherine M. Ronning William C. Nierman David E. Greenberg Steven M. Holland Joanna B. Goldberg 《Journal of bacteriology》2012,194(22):6356-6357
Burkholderia multivorans is a Gram-negative bacterium and a member of the Burkholderia cepacia complex, which is frequently associated with respiratory infections in people with cystic fibrosis (CF) and chronic granulomatous disease (CGD). We are reporting the genome sequences of 4 B. multivorans strains, 2 from CF patients and 2 from CGD patients. 相似文献
104.
Qayyum Imran Zubrow Alan B. Ashraf Qazi M. Kubin Joanna Delivoria-Papadopoulos Maria Mishra Om P. 《Neurochemical research》2001,26(10):1163-1169
Previous studies have shown that hypoxia induces nitric oxide synthase-mediated generation of nitric oxide free radicals leading to peroxynitrite production. The present study tests the hypothesis that hypoxia results in NO-mediated modification of Na+, K+-ATPase in the fetal brain. Studies were conducted in guinea pig fetuses of 58-days gestation. The mothers were exposed to FiO2 of 0.07% for 1 hour. Brain tissue hypoxia in the fetus was confirmed biochemically by decreased ATP and phosphocreatine levels. P2 membrane fractions were prepared from normoxic and hypoxic fetuses and divided into untreated and treated groups. The membranes were treated with 0.5 mM peroxynitrite at pH 7.6. The Na+, K+-ATPase activity was determined at 37°C for five minutes in a medium containing 100 mM NaCl, 20 mM KCl, 6.0 mM MgCl2, 50 mM Tris HCl buffer pH 7.4, 3.0 mM ATP with or without 10 mM ouabain. Ouabain sensitive activity was referred to as Na+, K+-ATPase activity. Following peroxynitrite exposure, the activity of Na+, K+-ATPase in guinea pig brain was reduced by 36% in normoxic membranes and further 29% in hypoxic membranes. Enzyme kinetics was determined at varying concentrations of ATP (0.5 mM-2.0 mM). The results indicate that peroxynitrite treatment alters the affinity of the active site of Na+, K+-ATPase for ATP and decreases the Vmax by 35% in hypoxic membranes. When compared to untreated normoxic membranes Vmax decreases by 35.6% in treated normoxic membranes and further to 52% in treated hypoxic membranes. The data show that peroxynitrite treatment induces modification of Na+, K+-ATPase. The results demonstrate that peroxynitrite decreased activity of Na+, K+-ATPase enzyme by altering the active sites as well as the microenvironment of the enzyme. We propose that nitric oxide synthase-mediated formation of peroxynitrite during hypoxia is a potential mechanism of hypoxia-induced decrease in Na+, K+-ATPase activity. 相似文献
105.
Murphy G Knäuper V Lee MH Amour A Worley JR Hutton M Atkinson S Rapti M Williamson R 《Biochemical Society symposium》2003,(70):65-80
Pericellular proteolysis represents one of the key modes by which the cell can modulate its environment, involving not only turnover of the extracellular matrix but also the regulation of cell membrane proteins, such as growth factors and their receptors. The metzincins are active players in such proteolytic events, and their mode of regulation is therefore of particular interest and importance. The TIMPs (tissue inhibitors of metalloproteinases) are established endogenous inhibitors of the matrix metalloproteinases (MMPs), and some have intriguing abilities to associate with the pericellular environment. It has been shown that TIMP-2 can bind to cell surface MT1-MMP (membrane-type 1 MMP) to act as a 'receptor' for proMMP-2 (progelatinase A), such that the latter can be activated efficiently in a localized fashion. We have examined the key structural features of TIMP-2 that determine this unique function, showing that Tyr36 and Glu192-Asp193 are vital for specific interactions with MT1-MMP and proMMP-2 respectively, and hence activation of proMMP-2. TIMP-3 is sequestered at the cell surface by association with the glycosaminoglycan chains of proteoglycans, especially heparan sulphate, and we have shown that it may play a role in the regulation of some ADAMs (a disintegrin and metalloproteinases), including tumour necrosis factor alpha-converting enzyme (TACE; ADAM17). We have established that key residues in TIMP-3 determine its interaction with TACE. Further studies of the features of TIMP-3 that determine specific binding to both ADAM and glycosaminoglycan are required in order to understand these unique properties. 相似文献
106.
Klos J Sliwinska E Kula A Golczyk H Grabowska-Joachimiak A Ilnicki T Szostek K Stewart A Joachimiak AJ 《Genetics and molecular biology》2009,32(3):528-537
The subgenus Ceratochloa of the genus Bromus includes a number of closely related allopolyploid forms or species that present a difficult taxonomic problem. The present work combines data concerning chromosome length, heterochromatin distribution and nuclear genome size of different 6x, 8x and 12x accessions in this subgenus. Special attention is paid to the karyotype structure and genomic constitution of duodecaploid plants recently found in South America. Hexaploid lineages possess six almost indistinguishable genomes and a nuclear DNA content between 12.72 pg and 15.10 pg (mean 1Cx value = 2.32 pg), whereas octoploid lineages contain the same six genomes (AABBCC) plus two that are characterized by longer chromosomes and a greater DNA content (1Cx = 4.47 pg). Two duodecaploid accessions found in South America resemble each other and apparently differ from the North American duodecaploid B. arizonicus as regards chromosome size and nuclear DNA content (40.00 and 40.50 pg vs. 27.59 pg). These observations suggest that the South American duodecaploids represent a separate evolutionary lineage of the B. subgenus Ceratochloa, unrecognized heretofore. 相似文献
107.
Lörinczi E Napp J Contreras-Jurado C Pardo LA Stühmer W 《European biophysics journal : EBJ》2009,38(3):279-284
The ether-à-go-go potassium channels hEag1 and hEag2 are highly homologous. Even though both possess identical voltage-sensing
domain S4, the channels act differently in response to voltage. Therefore we asked whether transmembrane domains other than
the voltage sensor could contribute to the voltage-dependent behaviour of these potassium channels. For this chimaeras were
created, in which each single transmembrane domain of hEag1 was replaced by the corresponding segment of hEag2. The voltage-dependent
properties of the chimaeras were analysed after expression in Xenopus laevis oocytes using the two-electrode voltage-clamp method. By this we found, that only the mutations in transmembrane domains
S5 and S6 are able to change the voltage sensitivity of hEag1 by shifting the half-activation potential (V
50) to values intermediate between the two wild types. Moreover, the presence of Mg2+ has strong effects on the voltage sensitivity of hEag2 shifting V
50 by more than 50 mV to more positive values. Interestingly, despite the identical binding site Mg2+ showed only little effects on hEag1 or the chimaeras. Altogether, our data suggest that not only transmembrane spanning regions,
but also non-membrane spanning regions are responsible for differences in the behaviour of the hEag1 and hEag2 potassium channels.
EBSA Satellite meeting: Ion channels, Leeds, July 2007. 相似文献
108.
Joanna Skommer Tom Brittain Subhadip Raychaudhuri 《Apoptosis : an international journal on programmed cell death》2010,15(10):1223-1233
BH3 mimetics have been proposed as new anticancer therapeutics. They target anti-apoptotic Bcl-2 proteins, up-regulation of
which has been implicated in the resistance of many cancer cells, particularly leukemia and lymphoma cells, to apoptosis.
Using probabilistic computational modeling of the mitochondrial pathway of apoptosis, verified by single-cell experimental
observations, we develop a model of Bcl-2 inhibition of apoptosis. Our results clarify how Bcl-2 imparts its anti-apoptotic
role by increasing the time-to-death and cell-to-cell variability. We also show that although the commitment to death is highly
impacted by differences in protein levels at the time of stimulation, inherent stochastic fluctuations in apoptotic signaling
are sufficient to induce cell-to-cell variability and to allow single cells to escape death. This study suggests that intrinsic
cell-to-cell stochastic variability in apoptotic signaling is sufficient to cause fractional killing of cancer cells after
exposure to BH3 mimetics. This is an unanticipated facet of cancer chemoresistance. 相似文献
109.
Garg R Juncadella IJ Ramamoorthi N Ashish Ananthanarayanan SK Thomas V Rincón M Krueger JK Fikrig E Yengo CM Anguita J 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(10):6579-6583
Salp15 is an Ixodes scapularis salivary protein that inhibits CD4+ T cell activation through the repression of TCR ligation-triggered calcium fluxes and IL-2 production. We show in this study that Salp15 binds specifically to the CD4 coreceptor on mammalian host T cells. Salp15 specifically associates through its C-terminal residues with the outermost two extracellular domains of CD4. Upon binding to CD4, Salp15 inhibits the subsequent TCR ligation-induced T cell signaling at the earliest steps including tyrosine phosphorylation of the Src kinase Lck, downstream effector proteins, and lipid raft reorganization. These results provide a molecular basis to understanding the immunosuppressive activity of Salp15 and its specificity for CD4+ T cells. 相似文献
110.
The aim of the study was to determine the quality and quantity of siderophores produced by bacteria isolated from plants' roots. The second aim was to determine the effect of siderophores on plants growth (Festuca rubra L. and Brassica napus L.). The study was carried out using bacteria isolated from roots of: Arabidopsis thaliana L., F. rubra, and Agrostis capillaris L., growing on the heavy metals contaminated area. The chrome azurol sulfonate (CAS) test, Arnow's test for catechol siderophores, and Csaksy's test for hydroxamate siderophores were performed. Among the bacteria, 42 isolates (39%) had a positive result in the CAS. Endophytic bacteria were mostly producing the catechol siderophores. It was found that F. rubra is the plant which is linked with the highest number of siderophores producing bacteria. The highest concentration of siderophores was noted for ectorhizospheric bacteria associated with A. thaliana, hyperaccumulating plant. It was found that hydroxamate siderophores are mainly produced by ectorhizosphere and rhizoplane bacteria. The siderophores producing bacteria reduced the toxicity of metals and improved the phytoremediation. Siderophores treatment increased the growth of plants in the biological assay, growing on two different soils: one highly contaminated with heavy metals and the second strongly alkaline soil. 相似文献