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101.
Prolonged culture in low glucose induces apoptosis of rat pancreatic beta-cells through induction of c-myc 总被引:4,自引:0,他引:4
Van de Casteele M Kefas BA Cai Y Heimberg H Scott DK Henquin JC Pipeleers D Jonas JC 《Biochemical and biophysical research communications》2003,312(4):937-944
Prolonged culture in low-glucose concentrations (=5mM) induces apoptosis in pancreatic beta-cells by a poorly defined mechanism. We now show that, in both purified rat beta-cells and isolated rat islets, culture in the presence of 3 or 5mM (G3-G5) instead of 10mM glucose (G10) induces a large increase in c-myc expression before onset of a caspase-dependent apoptosis. These effects were prevented by addition of leucine and glutamine to G3 and G5, and were mimicked by addition of the mitochondrial poison azide to G10. In contrast, inhibition of Ca(2+) influx and insulin secretion with diazoxide under control conditions did not stimulate islet c-myc expression nor beta-cell apoptosis. In rat beta-cells, adenovirus-mediated c-myc overexpression increased their rate of apoptosis, whereas antisense-c-myc expression reduced low-glucose-induced apoptosis by approximately 50%. In the insulin producing MIN6 cell line, apoptosis induction by either low glucose or an activator of AMP-activated protein kinase (AMPK) was associated with c-myc mRNA and protein upregulation. In conclusion, stimulation of beta-cell apoptosis by prolonged culture at low glucose partly results from early and sustained induction of beta-cell c-myc expression. These effects may be due to sustained restriction in nutrient-derived metabolic signals. 相似文献
102.
Katharina A. Quadt Lea Barfod Daniel Andersen Jonas Bruun Ben Gyan Tue Hassenkam Michael F. Ofori Lars Hviid 《PloS one》2012,7(9)
Background
The virulence of Plasmodium falciparum malaria is related to the parasite’s ability to evade host immunity through clonal antigenic variation and tissue-specific adhesion of infected erythrocytes (IEs). The P. falciparum erythrocyte membrane protein 1 (PfEMP1) family expressed on dome-shaped protrusions called knobs on the IE surface is central to both. Differences in receptor specificity and affinity of expressed PfEMP1 are important for IE adhesiveness, but it is not known whether differences in the number and size of the knobs on which the PfEMP1 proteins are expressed also play a role. Therefore, the aim of this study was to provide detailed information on isolate- and time-dependent differences in knob size and density.Methodology/Principal Findings
We used atomic force microscopy to characterize knobs on the surface of P. falciparum-infected erythrocytes. Fourteen ex vivo isolates from Ghanaian children with malaria and 10 P. falciparum isolates selected in vitro for expression of a particular PfEMP1 protein (VAR2CSA) were examined. Knob density increased from ∼20 h to ∼35 h post-invasion, with significant variation among isolates. The knob density ex vivo, which was about five-fold higher than following long-term in vitro culture, started to decline within a few months of culture. Although knob diameter and height varied among isolates, we did not observe significant time-dependent variation in these dimensions.Conclusions/Significance
The density of knobs on the P. falciparum-IE surface depends on time since invasion, but is also determined by the infecting isolate in a time-independent manner. This is the first study to quantitatively evaluate knob densities and dimensions on different P. falciparum isolates, to examine ex vivo isolates from humans, and to compare ex vivo and long-term in vitro-cultured isolates. Our findings contribute to the understanding of the interaction between P. falciparum parasites and the infected host. 相似文献103.
María Herranz Jonas Thormar Jesús BenitoNuria Sánchez Fernando Pardos 《Zoologischer Anzeiger》2012,251(3):161-179
A new kinorhynch genus, Meristoderes gen. nov., and two new species from Spain and the Solomon Islands, respectively, are described. The new genus is distinguished from all other genera by the first segment consisting of a closed cuticular ring, and the second segment having partial tergosternal junctions, and a superficial midventral fold. This is a new cuticular configuration that may shed light into the phylogenetic relationships of echinoderid kinorhynchs. Meristoderes macracanthus gen. et sp. nov. from the Mediterranean coast of Spain is recognised by the presence of middorsal spines on segments 4, 6 and 8, ventrolateral tubules on segment 2, lateroventral tubules on segment 5, lateroventral spines on segments 6-9, lateral accessory tubules on segment 8, one pair of laterodorsal tubules on segment 10. Meristoderes galatheae sp. nov. from the Solomon Islands is recognized by having a middorsal spine on segment 4 only, ventrolateral tubules on segment 2, lateroventral tubules on segment 5, lateroventral spines on segments 6-9, lateral accessory tubules on segment 8 and subdorsal tubules on segment 10. Both species have a pattern of paraventral perforation site clusters on segments 3-9, with conspicuously long bracteate hairs from the posteriormost perforations sites on the segments 3-7 and 3-6, respectively.The new genus Meristoderes gen. nov. is included into the family Echinoderidae Bütschli, 1876 and appears closely related with the genera Cephalorhyncha Adrianov, 1999 and Echinoderes Claparède, 1863. The new information it provides is discussed to clarify the internal phylogeny of Echinoderidae. The terminology for cuticular characters in the overlapping area between consecutive segments is also standardized. 相似文献
104.
R J Frampton H A Jonas R A MacMahon R G Larkins 《Journal of developmental physiology》1990,13(3):125-133
To investigate the response of the growth retarded neonatal rat to insulin-like growth factor-I (IGF-I) we have measured the effect of IGF-I on in vitro muscle protein synthesis and degradation rates in growth retarded and control neonatal rat pups. The growth retarded pups were growth retarded in utero by ligation of the uterine blood supply at day 17 of gestation. Basal levels of muscle protein synthesis in vitro were significantly lower in growth retarded pups compared with controls. Protein degradation rate were not different in muscles taken from the two groups. IGF-I stimulated protein synthesis in muscle from control pups by 12% and 15% at 20 ng/ml and 200ng/ml respectively. Net protein degradation was inhibited by 20% in the presence of 20ng/ml IGF-I. IGF-I had no effect on net protein synthesis or degradation in muscle from growth retarded pups. Neither Multiplication Stimulating Activity (at 20ng/ml or 200ng/ml) nor insulin (at 40ng/ml or 800ng/ml) was able to increase synthesis or decrease degradation of protein. Specific receptors for IGF-I are present on muscle membranes from both groups. Unlabelled IGF-I was more effective than MSA or insulin in competing with 125I-IGF-I for binding to the receptor. The relative affinities are consistent with type I IGF receptors. The affinity of these receptors for IGF-I was similar (Kd approximately 5nM) in both groups and the receptor concentration in both cases was approximately 250 fmol/mg protein. The refractility of tissue from growth retarded pups to IGF-I may be partially responsible for the lack of catch up growth in growth retarded neonates. 相似文献
105.
106.
107.
Alfhild Grönbladh Jenny Johansson Mark M. Kushnir Jonas Bergquist Mathias Hallberg 《Steroids》2013,78(12-13):1192-1199
Growth hormone (GH) and anabolic androgenic steroids (AAS) are commonly used in sports communities. Several studies have suggested an association between GH and AAS. We have investigated the impact of GH in rats treated with nandrolone decanoate (ND). Male Wistar rats received ND (15 mg/kg) every third day during three weeks and were subsequently treated with recombinant human GH (1.0 IU/kg) for ten consecutive days. Plasma samples were collected and peripheral organs (i.e. heart, liver, testis and thymus) were dissected and weighed. Concentration of thirteen endogenous steroids was measured in the rat plasma samples using high specificity LC–MS/MS methods. Seven steroids were detected and quantified, and concentrations of estrone, testosterone, and androstenedione were significantly different among the groups, while concentrations of pregnenolone, DHEA, 17-hydroxyprogesterone and corticosterone were not altered. Administration of rhGH alone altered the plasma steroid distribution, and the results demonstrated significantly increased concentrations of plasma estrone as well as decreased concentrations of testosterone and androstenedione in the ND-treated rats. Administration of rhGH to ND-pretreated rats did not reverse the alteration of the steroid distribution induced by ND. Administration of ND decreased the weight of the thymus, and addition of rhGH did not reverse this reduction. However, rhGH administration induced an enlargement of thymus. Taken together, the plasma steroid profile differed in the four groups, i.e. control, AAS, rhGH and the combination of AAS and rhGH treatment. 相似文献
108.
Masayuki Hanaoka Mark R Nicolls Andrew P Fontenot Donatas Kraskauskas Douglas G Mack Adelheid Kratzer Jonas Salys Vita Kraskauskiene Nana Burns Norbert F Voelkel Laimute Taraseviciene-Stewart 《Respiratory research》2010,11(1):179
Background
The presence of anti-endothelial cell antibodies and pathogenic T cells may reflect an autoimmune component in the pathogenesis of emphysema. Whether immune modulatory strategies can protect against the development of emphysema is not known.Methods
Sprague Dawley rats were immunized with human umbilical vein endothelial cells (HUVEC) to induce autoimmune emphysema and treated with intrathymic HUVEC-injection and pristane. Measurements of alveolar airspace enlargement, cytokine levels, immuno histochemical, western blot analysis, and T cell repertoire of the lung tissue were performed.Results
The immunomodulatory strategies protected lungs against cell death as demonstrated by reduced numbers of TUNEL and active caspase-3 positive cells and reduced levels of active caspase-3, when compared with lungs from HUVEC-immunized rats. Immunomodulatory strategies also suppressed anti-endothelial antibody production and preserved CNTF, IL-1alpha and VEGF levels. The immune deviation effects of the intrathymic HUVEC-injection were associated with an expansion of CD4+CD25+Foxp3+ regulatory T cells. Pristane treatment decreased the proportion of T cells expressing receptor beta-chain, Vβ16.1 in the lung tissue.Conclusions
Our data demonstrate that interventions classically employed to induce central T cell tolerance (thymic inoculation of antigen) or to activate innate immune responses (pristane treatment) can prevent the development of autoimmune emphysema. 相似文献109.
Patterns and controls of the variability of radiation use efficiency and primary productivity across terrestrial ecosystems 总被引:2,自引:0,他引:2
Martín F. Garbulsky Josep Peñuelas Dario Papale Jonas Ardö Michael L. Goulden Gerard Kiely Andrew D. Richardson Eyal Rotenberg Elmar M. Veenendaal Iolanda Filella 《Global Ecology and Biogeography》2010,19(2):253-267
Aim The controls of gross radiation use efficiency (RUE), the ratio between gross primary productivity (GPP) and the radiation intercepted by terrestrial vegetation, and its spatial and temporal variation are not yet fully understood. Our objectives were to analyse and synthesize the spatial variability of GPP and the spatial and temporal variability of RUE and its climatic controls for a wide range of vegetation types. Location A global range of sites from tundra to rain forest. Methods We analysed a global dataset on photosynthetic uptake and climatic variables from 35 eddy covariance (EC) flux sites spanning between 100 and 2200 mm mean annual rainfall and between ?13 and 26°C mean annual temperature. RUE was calculated from the data provided by EC flux sites and remote sensing (MODIS). Results Rainfall and actual evapotranspiration (AET) positively influenced the spatial variation of annual GPP, whereas temperature only influenced the GPP of forests. Annual and maximum RUE were also positively controlled primarily by annual rainfall. The main control parameters of the growth season variation of gross RUE varied for each ecosystem type. Overall, the ratio between actual and potential evapotranspiration and a surrogate for the energy balance explained a greater proportion of the seasonal variation of RUE than the vapour pressure deficit (VPD), AET and precipitation. Temperature was important for determining the intra‐annual variability of the RUE at the coldest energy‐limited sites. Main conclusions Our analysis supports the idea that the annual functioning of vegetation that is adapted to its local environment is more constrained by water availability than by temperature. The spatial variability of annual and maximum RUE can be largely explained by annual precipitation, more than by vegetation type. The intra‐annual variation of RUE was mainly linked to the energy balance and water availability along the climatic gradient. Furthermore, we showed that intra‐annual variation of gross RUE is only weakly influenced by VPD and temperature, contrary to what is frequently assumed. Our results provide a better understanding of the spatial and temporal controls of the RUE and thus could lead to a better estimation of ecosystem carbon fixation and better modelling. 相似文献
110.
Mörner Torsten Malmsten Jonas Bernodt Karin Lunneryd Sven-Gunnar 《Acta veterinaria Scandinavica》2013,55(1):1-3