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211.
Astrid?Kodric-BrownEmail author Paul?F.?Nicoletto 《Environmental Biology of Fishes》2005,73(3):299-307
Synopsis We document differences in the use of microhabitats, male courtship behavior, and swimming performance of populations from headwater and downstream sites in two rivers of the Oropuche drainage in Trinidad. Guppies from headwater sites used microhabitats with higher water velocities, had a higher swimming performance, and were less patchily distributed than guppies from downstream sites. Although males from the headwater and downstream sites had similar display rates, males from headwater sites displayed in microhabitats with higher velocities (riffles) whereas males in downstream sites courted in still pools. Subtle effects of female choice maintain the honesty of male courtship behavior in various microhabitats. In downstream sites, where predators impose a survivorship cost on ornamental males, swimming performance was positively correlated with area of carotenoid ornamentation. In headwater sites, males frequently displayed in fast-flowing water, thus paid a higher metabolic cost of courtship. Interactions between characteristics of the physical habitat and predation pressure not only affect the distribution of guppies, but also have subtle effects on the types of condition-dependent traits favored by females. 相似文献
212.
Wohlgemuth S Kiel C Krämer A Serrano L Wittinghofer F Herrmann C 《Journal of molecular biology》2005,348(3):741-758
Common domain databases contain sequence motifs which belong to the ubiquitin fold family and are called Ras binding (RB) and Ras association (RalGDS/AF6 Ras associating) (RA) domains. The name implies that they bind to Ras (or Ras-like) GTP-binding proteins, and a few of them have been documented to qualify as true Ras effectors, defined as binding only to the activated GTP-bound form of Ras. Here we have expressed a large number of these domains and investigated their interaction with Ras, Rap and M-Ras. While their (albeit weak) sequence homology suggest that the domains adopt a common fold, not all of them bind to Ras proteins, irrespective of whether they are called RB or RA domains. We used fluorescence spectroscopy and isothermal titration calorimetry to show that the binding affinities vary over a large range, and are usually specific for either Ras or Rap. Moreover, the specificity is dictated by a set of key residues in the interface. Stopped-flow kinetic analysis showed that the association rate constants determine the different affinities of effector binding, while the dissociation rate constants are in a similar range. Manual sequence analysis allowed us to define positively charged sequence epitopes in certain secondary structure elements of the ubiquitin fold (beta1, beta2 and alpha1) which are located at similar positions and comprise the hot spots of the binding interface. These residues are important to qualify an RA/RB domain as a true candidate Ras or Rap effector. 相似文献
213.
Sovic A Panzenboeck U Wintersperger A Kratzer I Hammer A Levak-Frank S Frank S Rader DJ Malle E Sattler W 《Journal of neurochemistry》2005,94(1):109-119
Normal neurological function depends on a constant supply of polyunsaturated fatty acids to the brain. A considerable proportion of essential fatty acids originates from lipoprotein-associated lipids that undergo uptake and/or catabolism at the blood-brain barrier (BBB). This study aimed at identifying expression and regulation of endothelial lipase (EL) in brain capillary endothelial cells (BCEC), major constituents of the BBB. Our results revealed that BCEC are capable of EL synthesis and secretion. Overexpression of EL resulted in enhanced hydrolysis of extracellular high-density lipoprotein (HDL)-associated sn-2-labeled [(14)C]20 : 4 phosphatidylcholine. [(14)C]20 : 4 was recovered in cellular lipids, indicating re-uptake and intracellular re-esterification. To investigate local regulation of EL in the cerebrovasculature, BCEC were cultured in the presence of peroxisome-proliferator activated receptor (PPAR)- and liver X receptor (LXR)-agonists, known to regulate HDL levels. These experiments revealed that 24(S)OH-cholesterol (a LXR agonist), bezafibrate (a PPARalpha agonist), or pioglitazone (a PPARgamma agonist) resulted in down-regulation of EL mRNA and protein levels. Our findings implicate that EL could generate fatty acids at the BBB for transport to deeper regions of the brain as building blocks for membrane phospholipids. In addition PPAR and LXR agonists appear to contribute to HDL homeostasis at the BBB by regulating EL expression. 相似文献
214.
Degradation of azo dyes by laccase and ultrasound treatment 总被引:3,自引:0,他引:3
The goal of this work was to investigate the decomposition of azo dyes by oxidative methods, such as laccase and ultrasound treatments. Each of these methods has strong and feeble sides. The laccase treatment showed high decolorization rates but cannot degrade all investigated dyes (reactive dyes), and high anionic strength led to enzyme deactivation. Ultrasound treatment can decolorize all tested dyes after 3 h at a high energy input, and prolonged sonication leads to nontoxic ionic species, which was demonstrated by ion chromatography and toxicity assays. For the first time, it was shown that a combination of laccase and ultrasound treatments can have synergistic effects, which was shown by higher degradation rates. Bulk light absorption and ion-pairing high-performance liquid chromatography (IP-HPLC) were used for process monitoring, while with reversed-phase HPLC, a lower number of intermediates than expected by IP-HPLC was found. Liquid chromatography-mass spectrometry indicated that both acid orange dyes lead to a common end product due to laccase treatment. Acid Orange 52 is demethylated by laccase and ultrasound treatment. Further results confirmed that the main effect of ultrasound is based on *OH attack on the dye molecules. 相似文献
215.
Fanconi anemia (cross)linked to DNA repair 总被引:2,自引:0,他引:2
Fanconi anemia is characterized by hypersensitivity to DNA interstrand crosslinks (ICLs) and susceptibility to tumor formation. Despite the identification of numerous Fanconi anemia (FANC) genes, the mechanism by which proteins encoded by these genes protect a cell from DNA interstrand crosslinks remains unclear. The recent discovery of two DNA helicases that, when defective, cause Fanconi anemia tips the balance in favor of the direct involvement of the FANC proteins in DNA repair and the bypass of DNA lesions. 相似文献
216.
Effects of hypothermia and re-warming on the inflammatory response in a murine multiple hit model of trauma 总被引:13,自引:0,他引:13
Hildebrand F van Griensven M Giannoudis P Luerig A Harwood P Harms O Fehr M Krettek C Pape HC 《Cytokine》2005,31(5):382-393
INTRODUCTION: Although, hypothermia is a frequent event after trauma, it is unclear whether its beneficial or detrimental effects are more important. This study aims to quantify the effects of hypothermia and re-warming on the inflammatory response after fracture/hemorrhage and subsequent fracture stabilization with resuscitation. MATERIALS AND METHODS: Eighty-one male C57Bl/6 mice (aged 8-10 weeks, weighing 22.0+/-3.0 g) underwent femoral fracture and hemorrhage followed by resuscitation and splint fixation of the fracture. Animals were sacrificed 3h after induction of hemorrhage and fracture. Besides a sham group (n=6), four experimental groups were created: A: normothermia (n=12), B: hypothermia after trauma (n=21), C: re-warming after resuscitation and before stabilization (n=21), and D: hypothermia before trauma (n=21). Groups B-D were further subdivided into three subgroups according to the degree of hypothermia (subgroup 1: 35-33 degrees C, subgroup 2: 32.9-30.0 degrees C, and subgroup 3: 29.9-27.0 degrees C). Plasma cytokine (TNF-alpha, IL-6, and IL-10) and chemokine (MCP-1) concentrations were determined by ELISA, pulmonary permeability changes were quantified, and histological analysis of lung and liver tissues was performed. RESULTS: Normothermia resulted in a significantly increased early mortality rate. A significantly increased pro-inflammatory and decreased anti-inflammatory responses were also observed in normothermia as compared to hypothermia. The extent of these changes was most pronounced in the severe hypothermic group. Re-warming after mild hypothermia resulted in a pro-inflammatory response comparable to normothermia. CONCLUSION: Hypothermia has a beneficial effect on early survival after trauma, which appears to be independent of the level of hypothermia and re-warming. Re-warming, however, enhanced the pro-inflammatory response. Further studies with a longer posttraumatic observation period are required to investigate the long term effects of the hypothermia and re-warming-induced changes on the pro- and anti-inflammatory responses. 相似文献
217.
Tumor necrosis factor (TNF) signaling is mediated via two distinct receptors, TNFR2 and TNFR1, which shows partially overlapping signaling mechanisms and biological roles. In the present study, TNFR2 and TNFR1 signal transduction mechanisms involved in activation of NFkappaB and CMV promoter-enhancer were compared with respect to their susceptibility towards inhibitors of intracellular signaling. For this, we used SW480 cells, where we have shown that TNF-signaling can occur independently through each of the two receptors. The TNFR1 response was inhibited by D609, bromophenacyl bromide (BPB), nordihydroguararetic acid (NDGA), and by sodium salicylate, while TNFR2-mediated activation of NFkappaB and CMV promoter-enhancer was resistant to these compounds. The signaling mechanisms known to be affected by these inhibitors include phospholipases as well as redox- and pH-sensitive intracellular components. Our results imply that TNFR2 signaling involved in NFkappaB activation proceeds independently of these inhibitor-sensitive signaling components, indicating distinct signaling pathways not shared with TNFR1. 相似文献
218.
Schroeder P Voevodskaya N Klotz LO Brenneisen P Gräslund A Sies H 《Biochemical and biophysical research communications》2005,326(3):614-617
The flavonoid (-)-epicatechin was previously demonstrated to interfere with tyrosine nitration by peroxynitrite [Biochem. Biophys. Res. Commun. 285 (2001) 782]. This effect was hypothesized to be based upon an interaction of epicatechin with a transiently generated tyrosyl radical. In the present study, using electron paramagnetic resonance, we demonstrate that (-)-epicatechin is capable of destabilizing the tyrosyl radical of the mouse ribonucleotide reductase R2 component. First-order rate constants for the disappearance of tyrosyl radical signals were 1 x 10(-4) and 2 x 10(-4)s(-1)for epicatechin and hydroxyurea, a well-known tyrosyl radical scavenger, respectively. In keeping with scavenging the ribonucleotide reductase tyrosyl radical, cellular production of deoxyribonucleotides and DNA synthesis were impaired by (-)-epicatechin in normal human keratinocytes and in human squamous carcinoma cells. 相似文献
219.
Expression of mutated cationic trypsinogen reduces cellular viability in AR4-2J cells 总被引:1,自引:0,他引:1
Gaiser S Ahler A Gundling F Kruse ML Savkovic V Selig L Teich N Tomasini R Dagorn JC Mössner J Keim V Bödeker H 《Biochemical and biophysical research communications》2005,334(2):721-728
Mutations in the human cationic trypsinogen are associated with hereditary pancreatitis. The cDNA coding for human cationic trypsinogen was subcloned into the expression vector pcDNA3. The mutations R122H, N29I, A16V, D22G, and K23R were introduced by site directed mutagenesis. We constructed an expression vector coding for active trypsin by subcloning the cDNA of trypsin lacking the coding region for the trypsin activating peptide behind an appropriate signal peptide. Expression of protein was verified by Western blot and measurement of enzymatic activity. AR4-2J cells were transiently transfected with the different expression vectors and cell viability and intracellular caspase-3 activity were quantified. In contrast to wild-type trypsinogen, expression of active trypsin and mutated trypsinogens reduced cell viability of AR4-2J cells. Expression of trypsin and R122H trypsinogen induced caspase-3 activity. Acinar cells might react to intracellular trypsin activity by triggering apoptosis. 相似文献
220.
Age-related increase of kynurenic acid in human cerebrospinal fluid - IgG and beta2-microglobulin changes 总被引:2,自引:0,他引:2
Kynurenic acid (KYNA) is an endogenous metabolite in the kynurenine pathway of tryptophan degradation and is an antagonist at the glycine site of the N-methyl-D-aspartate as well as at the alpha 7 nicotinic cholinergic receptors. In the brain tissue KYNA is synthesised from L-kynurenine by kynurenine aminotransferases (KAT) I and II. A host of immune mediators influence tryptophan degradation. In the present study, the levels of KYNA in cerebrospinal fluid (CSF) and serum in a group of human subjects aged between 25 and 74 years were determined by using a high performance liquid chromatography method. In CSF and serum KAT I and II activities were investigated by radioenzymatic assay, and the levels of beta(2)-microglobulin, a marker for cellular immune activation, were determined by ELISA. The correlations between neurochemical and biological parameters were evaluated. Two subject groups with significantly different ages, i.e. <50 years and >50 years, p < 0.001, showed statistically significantly different CSF KYNA levels, i.e. 2.84 +/- 0.16 fmol/microl vs. 4.09 +/- 0.14 fmol/microl, p < 0.001, respectively; but this difference was not seen in serum samples. Interestingly, KYNA is synthesised in CSF principally by KAT I and not KAT II, however no relationship was found between enzyme activity and ageing. A positive relationship between CSF KYNA levels and age of subjects indicates a 95% probability of elevated CSF KYNA with ageing (R = 0.6639, p = 0.0001). KYNA levels significantly correlated with IgG and beta(2)-microglobulin levels (R = 0.5244, p = 0.0049; R = 0.4253, p = 0.043, respectively). No correlation was found between other biological parameters in CSF or serum. In summary, a positive relationship between the CSF KYNA level and ageing was found, and the data would suggest age-dependent increase of kynurenine metabolism in the CNS. An enhancement of CSF IgG and beta(2)-microglobulin levels would suggest an activation of the immune system during ageing. Increased KYNA metabolism may be involved in the hypofunction of the glutamatergic and/or nicotinic cholinergic neurotransmission in the ageing CNS. 相似文献