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101.
ABSTRACT: BACKGROUND: The enzymatic conversion of lignocellulosic plant biomass into fermentable sugars is a crucial step in the sustainable and environmentally friendly production of biofuels. However, a major drawback of enzymes from mesophilic sources is their suboptimal activity under established pretreatment conditions, e.g. high temperatures, extreme pH values and high salt concentrations. Enzymes from extremophiles are better adapted to these conditions and could be produced by heterologous expression in microbes, or even directly in the plant biomass. RESULTS: Here we show that a cellulase gene (sso1354) isolated from the hyperthermophilic archaeon Sulfolobus solfataricus can be expressed in plants, and that the recombinant enzyme is biologically active and exhibits the same properties as the wild type form. Since the enzyme is inactive under normal plant growth conditions, this potentially allows its expression in plants without negative effects on growth and development, and subsequent heat-inducible activation. Furthermore we demonstrate that the recombinant enzyme acts in high concentrations of ionic liquids and can therefore degrade alpha-cellulose or even complex cell wall preparations under those pretreatment conditions. CONCLUSION: The hyperthermophilic endoglucanase SSO1354 with its unique features is an excellent tool for advanced biomass conversion. Here we demonstrate its expression in planta and the possibility for post harvest activation. Moreover the enzyme is suitable for combined pretreatment and hydrolysis applications. 相似文献
102.
Yap MW Lindemann D Stanke N Reh J Westphal D Hanenberg H Ohkura S Stoye JP 《Journal of virology》2008,82(11):5429-5439
Foamy viruses (FVs) are unconventional retroviruses with a replication strategy that is significantly different from orthoretroviruses and bears some homology to that of hepadnaviruses. Although some cellular proteins, such as APOBEC3, have been reported to block FVs, no restriction by Trim5alpha has been described to date. The sensitivity of three FV isolates of human-chimpanzee or prototypic (PFV), macaque (SFVmac), and feline (FFV) origin to a variety of primate Trim5alphas was therefore tested. PFV and SFVmac were restricted by Trim5alphas from most New World monkeys, but not from other primates, whereas FFV-based vectors were restricted by Trim5alphas from the great apes gorilla and orangutan. Trim5alphas from Old World monkeys did not restrict any FV isolate tested. Capuchin Trim5alpha was unique, as it restricted SFVmac and FFV but not PFV. Trim5alpha specificity for FVs was determined by the B30.2 domain, interestingly involving, in some instances, the same residues of the variable regions previously implicated as major determinants for human immunodeficiency virus type 1 restriction. FVs with chimeric Gags were made to map the viral determinants of sensitivity to restriction. The N-terminal half of the Gag molecule was found to contain the regions that control susceptibility. This region most likely corresponds to the capsid of conventional retroviruses. Due to their unique replication strategy, FVs should provide a valuable new system to examine the mechanism of retroviral restriction by Trim5alpha. 相似文献
103.
Andreas Ludwig Stefan Herrmann Evelyn Hoesl Juliane Stieber 《Progress in biophysics and molecular biology》2008,98(2-3):179
Pacemaker activity of the heart is generated by a small group of cells forming the sinoatrial node (SAN). Cells of the SAN are spontaneously active and generate action potentials with remarkable regularity and stability under all physiological conditions. The exact molecular mechanisms underlying pacemaker potentials in the SAN have not yet been fully elucidated. Several voltage-dependent ion channels as well as intracellular calcium cycling processes are thought to contribute to the pacemaker activity. Hyperpolarization-activated cation channels, which generate the If current, have biophysical properties which seem ideally suited for the initiation of spontaneous electrical activity. This review describes recent work on several transgenic mice lacking different cardiac HCN channel subtypes. The role of If for normal pacemaking and sinus node arrhythmia as revealed by these genetic models will be discussed. In addition, a new mouse line is described which enables gene targeting in a temporally-controlled manner selectively in SAN cells. Elucidating the function of HCN and other ion channels in well-controlled mouse models should ultimately lead to a better understanding of the mechanisms underlying human sinoatrial arrhythmias. 相似文献
104.
105.
The regulation of SIRT2 function by cyclin-dependent kinases affects cell motility 总被引:3,自引:0,他引:3 下载免费PDF全文
106.
von Montfort C Beier JI Guo L Kaiser JP Arteel GE 《American journal of physiology. Gastrointestinal and liver physiology》2008,294(5):G1227-G1234
It is well known that ethanol preexposure sensitizes the liver to LPS hepatotoxicity. The mechanisms by which ethanol enhances LPS-induced liver injury are not completely elucidated but are known to involve an enhanced inflammatory response. Ethanol exposure also increases the metabolic rate of the liver, and this effect of ethanol on liver is mediated, at least in part, by the sympathetic hormone, epinephrine. However, whether or not the sympathetic nervous system also contributes to the sensitizing effect of ethanol preexposure on LPS-induced liver damage has not been determined. The purpose of this study was therefore to test the hypotheses that 1) epinephrine preexposure enhances LPS-induced liver damage (comparable to that of ethanol preexposure) and that 2) the sympathetic nervous system contributes to the sensitizing effect of ethanol. Accordingly, male C57BL/6J mice were administered epinephrine for 5 days (2 mg/kg per day) via osmotic pumps or bolus ethanol for 3 days (6 g/kg per day) by gavage. Twenty-four hours later, mice were injected with LPS (10 mg/kg ip). Both epinephrine and ethanol preexposure exacerbated LPS-induced liver damage and inflammation. Concomitant administration of propranolol with ethanol significantly attenuated the sensitizing effect of ethanol on LPS-induced liver damage. These data support the hypothesis that the sympathetic nervous system contributes, at least in part, to the mechanism of the sensitizing effect of ethanol. These results also suggest that sympathetic tone may contribute to the initiation and progression of alcoholic liver disease. 相似文献
107.
108.
RNA thermometers are thermosensors that regulate gene expression by temperature-induced changes in RNA conformation. Naturally occurring RNA thermometers exhibit complex secondary structures which are believed to undergo a series of gradual structural changes in response to temperature shifts. Here, we report the de novo design of considerably simpler RNA thermometers that provide useful RNA-only tools to regulate bacterial gene expression by a shift in the growth temperature. We show that a single small stem-loop structure containing the ribosome binding site is sufficient to construct synthetic RNA thermometers that work efficiently at physiological temperatures. Our data suggest that the thermometers function by a simple melting mechanism and thus provide minimum size on/off switches to experimentally induce or repress gene expression by temperature. 相似文献
109.
Juliane Feurle Eric Espinosa Susanne Eckstein Frédéric Pont Volker Kunzmann Jean-Jacques Fournié Markus Herderich Martin Wilhelm 《The Journal of biological chemistry》2002,277(1):148-154
Human Vgamma9delta2 T lymphocytes are suggested to play an important role in the immune response to various microbial pathogens. In contrast to alphabeta T cells, gammadelta T lymphocytes recognize small, non-protein, phosphate-bearing antigens (phosphoantigens) in a major histocompatibility complex-independent manner. Four different phosphoantigens termed TUBag1 to TUBag4 with a common 3-formyl-1-butyl-pyrophosphate moiety and isopentenyl-pyrophosphate have been isolated and identified from mycobacteria. However, natural occurring gammadelta T cell ligands from other bacterial species were not characterized so far. Here, we describe the structural identification of the two compounds responsible for the gammadelta T cell-stimulating capacity of Escherichia coli as similar to the mycobacterial phosphoantigens 3-formyl-1-butyl-pyrophosphate and its M(r) 275 homologue TUBag2. In addition, E. coli phosphoantigens exert bioactivities on gammadelta T cells with similar potencies to the mycobacterial phosphoantigens at 5-15 nm concentration. Furthermore, our results clearly prove that the deoxyxylulose 5-phophate pathway (also referred to as Rohmer metabolic route of isoprenoid biosynthesis) is essential for the biosynthesis of the phosphoantigens in E. coli. Because this pathway is absent from human cells, it proves an ideal target for focusing efficiently the antimicrobial selectivity of human gammadelta T lymphocytes. 相似文献
110.
Effect of different carbon sources on the enhanced biological phosphorus removal in a sequencing batch reactor 总被引:1,自引:0,他引:1
Hollender Juliane van der Krol Doris Kornberger Liane Gierden Edith Dott Wolfgang 《World journal of microbiology & biotechnology》2002,18(4):359-364
The effect of the different carbon sources acetate, acetate/glucose or glucose on the enhanced biological phosphorus removal
(EBPR) process was studied by experiments under alternating anaerobic–aerobic conditions in one sequencing batch reactor for
each carbon source. The glucose was consumed completely within the first 30 min of the anaerobic phase whereas acetate degradation
was slow and incomplete. Phosphate was released independently of the carbon source during the whole anaerobic phase. The highest
phosphate release (27 mg P l−1) and polyhydroxyalkanoate (PHA) storage (20 mg C g−1 dry matter (DM)) during the anaerobic phase as well as the highest polyphosphate (poly-P) (8 mg P g−1 DM) and glycogen storage (17 mg C g−1 DM) during the aerobic phase were observed with acetate. In contrast to other investigations, glycogen storage did not increase
with glucose as substrate but was significantly smaller than with acetate. The PHA composition was also influenced strongly
by the carbon source. The polyhydroxyvalerate (PHV) portion of the PHA was maximal 17% for acetate and 82% for glucose. Due
to the strong influence of the carbon source on the PHA concentration and composition, PHA storage seems to regulate mainly
the phosphate release and uptake.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献