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991.
992.
This study investigated the molecular and biological variation among different Giardia duodenalis assemblages. In vitro growth and susceptibility to albendazole, fenbendazole, flubendazole, metronidazole, tinidazole and furazolidone was studied for laboratory (AI: WB, AII: G1 and B: GS/M-83-H7) and 6 field isolates of assemblage subtype AI, AII, B and EIII. Additionally, isolates of the 3 assemblages were evaluated in the gerbil upon 3-day oral treatment with albendazole (6 mg/kg), flubendazole (5 mg/kg) and metronidazole (20 mg/kg). Assemblage AI grew significantly faster than all other assemblage subtypes, which showed comparable generation times. The assemblage A laboratory strains displayed altered in vitro drug susceptibilities compared to their matching AI or AII field isolate. No variation in drug susceptibility was observed between field isolates of assemblages A and E. However, assemblage A laboratory strains were more susceptible to the benzimidazoles and less susceptible to the nitro-imidazoles and furazolidone than the assemblage B laboratory strain. In the gerbil, no markedly different drug susceptibilities were observed. In conclusion, the Giardia assemblage subtype can be associated with differences in growth characteristics rather than in drug susceptibility. 相似文献
993.
Cuveliers EL Volckaert FA Rijnsdorp AD Larmuseau MH Maes GE 《Molecular ecology》2011,20(17):3555-3568
Heavy fishing and other anthropogenic influences can have profound impact on a species' resilience to harvesting. Besides the decrease in the census and effective population size, strong declines in mature adults and recruiting individuals may lead to almost irreversible genetic changes in life-history traits. Here, we investigated the evolution of genetic diversity and effective population size in the heavily exploited sole (Solea solea), through the analysis of historical DNA from a collection of 1379 sole otoliths dating back from 1957. Despite documented shifts in life-history traits, neutral genetic diversity inferred from 11 microsatellite markers showed a remarkable stability over a period of 50 years of heavy fishing. Using simulations and corrections for fisheries induced demographic variation, both single-sample estimates and temporal estimates of effective population size (N(e) ) were always higher than 1000, suggesting that despite the severe census size decrease over a 50-year period of harvesting, genetic drift is probably not strong enough to significantly decrease the neutral diversity of this species in the North Sea. However, the inferred ratio of effective population size to the census size (N(e) /N(c) ) appears very small (10(-5) ), suggesting that overall only a low proportion of adults contribute to the next generation. The high N(e) level together with the low N(e) /N(c) ratio is probably caused by a combination of an equalized reproductive output of younger cohorts, a decrease in generation time and a large variance in reproductive success typical for marine species. Because strong evolutionary changes in age and size at first maturation have been observed for sole, changes in adaptive genetic variation should be further monitored to detect the evolutionary consequences of human-induced selection. 相似文献
994.
995.
996.
Hoeberichts FA van Doorn WG Vorst O Hall RD van Wordragen MF 《Journal of experimental botany》2007,58(11):2873-2885
997.
Alter G Suscovich TJ Teigen N Meier A Streeck H Brander C Altfeld M 《Journal of immunology (Baltimore, Md. : 1950)》2007,178(12):7658-7666
Persistent immune activation is a hallmark of chronic viremic HIV-1 infection. Activation of cells of the innate immune system, such as NK cells, occurs rapidly upon infection, and is sustained throughout the course of the disease. However, the precise underlying mechanism accounting for the persistent HIV-1-induced activation of NK cells is poorly understood. In this study, we assessed the role of uridine-rich ssRNA derived from the HIV-1 long terminal repeat (ssRNA40) on activation of NK cells via TLR7/8. Although dramatic activation of NK cells was observed following stimulation of PBMC with ssRNA40, negligible activation was observed following stimulation of purified NK cells despite their expression of TLR8 mRNA and protein. The functional activation of NK cells by this HIV-1-encoded TLR7/8 ligand could not be reconstituted with exogenous IL-12, IFN-alpha, or TNF-alpha, but was critically dependent on the direct contact of NK cells with plasmacytoid dendritic cells or CD14(+) monocytes, indicating an important level of NK cell cross-talk and regulation by accessory cells during TLR-mediated activation. Coincubation of monocyte/plasmacytoid dendritic cells, NK cells, and ssRNA40 potentiated NK cell IFN-gamma secretion in response to MHC-devoid target cells. Studies using NK cells derived from individuals with chronic HIV-1 infection demonstrated a reduction of NK cell responsiveness following stimulation with TLR ligands in viremic HIV-1 infection. These data demonstrate that HIV-1-derived TLR ligands can contribute to the immune activation of NK cells and may play an important role in HIV-1-associated immunopathogenesis and NK cell dysfunction observed during acute and chronic viremic HIV-1 infection. 相似文献
998.
Depending on the species, the end of flower life span is characterized by petal wilting or by abscission of petals that are
still fully turgid. Wilting at the end of petal life is due to programmed cell death (PCD). It is not known whether the abscission
of turgid petals is preceded by PCD. We studied some parameters that indicate PCD: chromatin condensation, a decrease in nuclear
diameter, DNA fragmentation, and DNA content per nucleus, using Prunus yedoensis and Delphinium
belladonna which both show abscission of turgid petals at the end of floral life. No DNA degradation, no chromatin condensation, and
no change in nuclear volume was observed in P. yedoensis petals, prior to abscission. In abscising D.
belladonna petals, in contrast, considerable DNA degradation was found, chromatin was condensed and the nuclear volume considerably
reduced. Following abscission, the nuclear area in both species drastically increased, and the chromatin became unevenly distributed.
Similar chromatin changes were observed after dehydration (24 h at 60°C) of petals severed at the time of flower opening,
and in dehydrated petals of Ipomoea nil and Petunia hybrida, severed at the time of flower opening. In these flowers the petal life span is terminated by wilting rather than abscission.
It is concluded that the abscission of turgid petals in D. belladonna was preceded by a number of PCD indicators, whereas no such evidence for PCD was found at the time of P. yedoensis petal abscission. Dehydration of the petal cells, after abscission, was associated with a remarkable nuclear morphology which
was also found in younger petals subjected to dehydration. This nuclear morphology has apparently not been described previously,
for any organism. 相似文献
999.
Validation of an individualised model of human thermoregulation for predicting responses to cold air
van Marken Lichtenbelt WD Frijns AJ van Ooijen MJ Fiala D Kester AM van Steenhoven AA 《International journal of biometeorology》2007,51(3):169-179
Most computer models of human thermoregulation are population based. Here, we individualised the Fiala model [Fiala et al.
(2001) Int J Biometeorol 45:143–159] with respect to anthropometrics, body fat, and metabolic rate. The predictions of the adapted
multisegmental thermoregulatory model were compared with measured skin temperatures of individuals. Data from two experiments,
in which reclining subjects were suddenly exposed to mild to moderate cold environmental conditions, were used to study the
effect on dynamic skin temperature responses. Body fat was measured by the three-compartment method combining underwater weighing
and deuterium dilution. Metabolic rate was determined by indirect calorimetry. In experiment 1, the bias (mean difference)
between predicted and measured mean skin temperature decreased from 1.8°C to −0.15°C during cold exposure. The standard deviation
of the mean difference remained of the same magnitude (from 0.7°C to 0.9°C). In experiment 2 the bias of the skin temperature
changed from 2.0±1.09°C using the standard model to 1.3±0.93°C using individual characteristics in the model. The inclusion
of individual characteristics thus improved the predictions for an individual and led to a significantly smaller systematic
error. However, a large part of the discrepancies in individual response to cold remained unexplained. Possible further improvements
to the model accomplished by inclusion of more subject characteristics (i.e. body fat distribution, body shape) and model
refinements on the level of (skin) blood perfusion, and control functions, are discussed. 相似文献
1000.
Langeslag M Clark K Moolenaar WH van Leeuwen FN Jalink K 《The Journal of biological chemistry》2007,282(1):232-239
TRPM7 is a ubiquitously expressed nonspecific cation channel that has been implicated in cellular Mg(2+) homeostasis. We have recently shown that moderate overexpression of TRPM7 in neuroblastoma N1E-115 cells elevates cytosolic Ca(2+) levels and enhances cell-matrix adhesion. Furthermore, activation of TRPM7 by phospholipase C (PLC)-coupled receptor agonists caused a further increase in intracellular Ca(2+) levels and augmented cell adhesion and spreading in a Ca(2+)-dependent manner (1). Regulation of the TRPM7 channel is not well understood, although it has been reported that PIP(2) hydrolysis closes the channel. Here we have examined the regulation of TRPM7 by PLC-coupled receptor agonists such as bradykinin, lysophosphatidic acid, and thrombin. Using FRET assays for second messengers, we have shown that the TRPM7-dependent Ca(2+) increase closely correlates with activation of PLC. Under non-invasive "perforated patch clamp" conditions, we have found similar activation of TRPM7 by PLC-coupled receptor agonists. Although we could confirm that, under whole-cell conditions, the TRPM7 currents were significantly inhibited following PLC activation, this PLC-dependent inhibition was only observed when [Mg(2+)](i) was reduced below physiological levels. Thus, under physiological ionic conditions, TRPM7 currents were activated rather than inhibited by PLC-activating receptor agonists. 相似文献