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991.
992.
Mattsson C Rask E Carlström K Andersson J Eliasson M Ahrén B Söderberg S Olsson T 《Obesity (Silver Spring, Md.)》2007,15(4):887-894
Objective: Reduction of cortisone to cortisol is mediated by 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1), a putative key enzyme in obesity‐related complications. Experimental studies suggest that adipokines, notably leptin and tumor necrosis factor‐α (TNF‐α), are of importance for 11βHSD1 activity. We hypothesized that the regulation of hepatic preceptor glucocorticoid metabolism is gender‐specific and associated with circulating levels of leptin and TNF‐α receptors and/or sex hormones. Research Methods and Procedures: A total of 34 males and 38 women (14 premenopausal and 22 postmenopausal) underwent physical examination and fasting blood sampling. Insulin sensitivity was tested by euglycemic hyperinsulinemic clamps, and hepatic 11βHSD1 enzyme activity was estimated by the conversion of orally‐ingested cortisone to cortisol. Results: Hepatic 11βHSD1 activity was negatively associated with leptin and soluble TNF (sTNF) r1 and sTNFr2 in males. These correlations remained significant after adjustment for age and insulin sensitivity, and for sTNF‐α receptors also after adjustment of BMI and waist circumference. In contrast, 11β reduction of cortisone was positively associated to leptin in females after adjustment for BMI and waist circumference. Discussion: Hepatic 11β reduction shows different links to circulating adipocyte‐derived hormones in males and females. This emphasizes the need for further studies on tissue‐specific regulation of 11βHSD1 in both genders. 相似文献
993.
994.
Summary The locomotory turns of the beetle Tenebrio molitor were recorded from free walking animals which were held in stationary position and orientation by means of a tread compensator. Striped patterns revolved around an animal elicit optomotor responses which undergo an inversion at smaller stripe widths. The position of the inversion point characterizes the resolving power of the motion detectors, and corresponds to a 6.5° average angle between the optical axes of interacting elements in the motion detecting device. This indirectly determined value is consistent with the anatomically measured 7° average angle between the axes of neighbouring ommatidia in the Tenebrio compound eye. 相似文献
995.
Summary The chromosome numbers of 11 species ofBiscutella were counted, in 5 species they were found out for the first time.Biscutella laevigata proved to be diploid in some places of Baveria, which are accordingly Submediterranean not Dealpin relicts. Chromosome numbers of n=8, 9 and 18 were counted in Spanish species of the Ser. Laevigatae. By these investigations it was shown that The problem ofBiscutella laevigata (Manton, 1934, 1937) and its allied species is not yet solved, but further cytotaxonomical research may bring forth fundamental results. 相似文献
996.
Summary In the present paper certain properties of potassium permanganate (KMnO4), a fixative used for electron microscopical investigations, have been studied in model test tube experiments and on tissues. Evidence was obtained that KMnO4 reacts with different types of biogenic monoamines resulting in a formation of a precipitate. In addition, also various monoamine analogues, precursors and metabolites reacts with KMnO4. The reaction taking place may be an oxidation-reduction-reaction in which KMnO4 is reduced, probably mainly to manganese dioxide by hydroxyl groups of the amines and related compounds. This is corroborated by the fact that no reaction takes place between KMnO4 and -phenylethylamine or amphetamine, two substances, which lack hydroxyl groups.Using labelled monoamines evidence was obtained that the amine partly is retained within the precipitate formed after the reaction with KMnO4 and also in tissues fixed with KMnO4, indicating a possibility to perform autoradiographic studies on KMnO4 fixed tissue.Electron microscopic studies on tissues fixed under various conditions revealed that fixation with low concentrations (0.6 and 1.0%) of KMnO4 and at high temperatures (about 20° C) leads to inferior results as to general morphology and as to the visualization of intraneuronal amine stores.Different types of permanganates were tested as fixatives. These results show that fixation with permanganates with monovalent metallic ions (K+, Li+ and Na+) give good results of comparable quality, whereas fixation with zinc permanganate results in seriously destroyed tissues. However, tissue fixed with calcium permanganate reveals very distinct membranes. Furthermore, evidence was obtained that fixation with high concentrations of LiMnO4 (6 and 9%) and NaMnO4 (6 and 9%) was more sensitive as to the demonstration of monoamines at the ultrastructural level as compared to 3% KMnO4. Thus, with e.g. 6 and 9% LiMnO4 small granular vesicles could be seen in slices from the caudate nucleus after incubation with -methyl-dopamine. This was not possible when using 3% KMnO4 as a fixative. 相似文献
997.
Spatial and temporal heterogeneity in the environment is a common feature affecting many natural populations. For example,
both the resource levels and optimal habitat choices of individuals likely change over time. One way for organisms to cope
with environmental variation is to display adaptive plasticity in traits such as behavior and morphology. Since trait plasticity
is hypothesized to be a prerequisite for character divergence, studies of mechanisms behind such plasticity are warranted.
In this study, we looked at the interaction of two potentially important environmental variables on behavioral and morphological
plasticity in Eurasian perch (Perca fluviatilis L.). More specifically, the plastic responses in activity and morphology of perch exposed to different resource levels and
simulated habitat types were studied in an aquarium experiment. The resource level experienced had a large influence on plasticity
in both activity and morphology. Behavioral adaptations have been thought to mediate morphological transitions, and we suggest
that the morphological response to the resource level was mediated by differences in activity and growth rates. The habitat
type also affected morphological plasticity but to a lesser extent, and there was no effect on activity from habitat type.
Based on these results, we suggest that it is essential to include several environmental factors acting in concert when studying
mechanisms behind trait plasticity. We also propose that variation in resource levels might play a key role in fostering trait
plasticity in at least fish populations, while other environmental variables such as divergent habitat complexities and prey
types might be less influential. Dynamics in resource levels and optimal habitat choices might thus be important factors influencing
character divergence in natural populations. 相似文献
998.
Christine Köppl Otto Gleich 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2007,193(6):601-612
Gross electrical responses to tone bursts were measured in adult barn owls, using a single-ended wire electrode placed onto
the round window. Cochlear microphonic (CM) and compound action potential (CAP) responses were evaluated separately. Both
potentials were physiologically vulnerable. Selective abolishment of neural responses at high frequencies confirmed that the
CAP was of neural origin, while the CM remained unaffected. CAP latencies decreased with increasing stimulus frequency and
CAP amplitudes were correlated with known variations in afferent fibre numbers from the different papillar regions. This suggests
a local origin of the CAP along the tonotopic gradient within the basilar papilla. The audiograms derived from CAP and CM
threshold responses both showed a broad frequency region of optimal sensitivity, very similar to behavioural and single-unit
data, but shifted upward in absolute sensitivity. CAP thresholds rose above 8 kHz, while CM responses showed unchanged sensitivity
up to 10 kHz. 相似文献
999.
Edgcomb VP Molyneaux SJ Böer S Wirsen CO Saito M Atkins MS Lloyd K Teske A 《Extremophiles : life under extreme conditions》2007,11(2):329-342
Growth and survival of hyperthermophilic archaea in their extreme hydrothermal vent and subsurface environments are controlled
by chemical and physical key parameters. This study examined the effects of elevated sulfide concentrations, temperature,
and acidic pH on growth and survival of two hydrothermal vent archaea (Pyrococcus strain GB-D and Thermococcus fumicolans) under high temperature and pressure regimes. These two strains are members of the Thermococcales, a family of hyperthermophilic,
heterotrophic, sulfur-reducing archaea that occur in high densities at vent sites. As actively growing cells, these two strains
tolerated regimes of pH, pressure, and temperature that were in most cases not tolerated under severe substrate limitation.
A moderate pH of 5.5–7 extends their survival and growth range over a wider range of sulfide concentrations, temperature and
pressure, relative to lower pH conditions. T. fumicolans and Pyrococcus strain GB-D grew under very high pressures that exceeded in-situ pressures typical of hydrothermal vent depths, and included
deep subsurface pressures. However, under the same conditions, but in the absence of carbon substrates and electron acceptors,
survival was generally lower, and decreased rapidly when low pH stress was combined with high pressure and high temperature.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
1000.
Näsström T Gonçalves S Sahlin C Nordström E Screpanti Sundquist V Lannfelt L Bergström J Outeiro TF Ingelsson M 《PloS one》2011,6(10):e27230
Recent research implicates soluble aggregated forms of α-synuclein as neurotoxic species with a central role in the pathogenesis of Parkinson's disease and related disorders. The pathway by which α-synuclein aggregates is believed to follow a step-wise pattern, in which dimers and smaller oligomers are initially formed. Here, we used H4 neuroglioma cells expressing α-synuclein fused to hemi:GFP constructs to study the effects of α-synuclein monoclonal antibodies on the early stages of aggregation, as quantified by Bimolecular Fluorescence Complementation assay. Widefield and confocal microscopy revealed that cells treated for 48 h with monoclonal antibodies internalized antibodies to various degrees. C-terminal and oligomer-selective α-synuclein antibodies reduced the extent of α-synuclein dimerization/oligomerization, as indicated by decreased GFP fluorescence signal. Furthermore, ELISA measurements on lysates and conditioned media from antibody treated cells displayed lower α-synuclein levels compared to untreated cells, suggesting increased protein turnover. Taken together, our results propose that extracellular administration of monoclonal antibodies can modify or inhibit early steps in the aggregation process of α-synuclein, thus providing further support for passive immunization against diseases with α-synuclein pathology. 相似文献