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101.
102.
Tressia M. Dayton Karen A. Diefenbach Michelle L. Fuller Joshua Valtos Eric C. Niederhoffer 《Biometals》1996,9(2):131-137
Proteus mirabilis and Proteus vulgaris expressed a combination of superoxide dismutase (Sod) activities, which was assigned to FeSod1, FeSod2 and MnSod for P. mirabilis, and FeSod, MnSod and CuZnSod for P. vulgaris. Production of the Sod proteins was dependent on the availability of iron, whether cells were grown under anaerobiosis or aerobiosis and growth phase. Nalidixic acid and chloramphenicol inhibited cell growth and the iron- and dioxygen-dependent production of Sod. These results support the involvement of metal ions and redox status in the production of Proteus Sods. 相似文献
103.
104.
Benzothiadiazole induces disease resistance in Arabidopsis by activation of the systemic acquired resistance signal transduction pathway 总被引:18,自引:6,他引:12
Kay A. Lawton Leslie Friedrich Michelle Hunt Kris Weymann Terrance Delaney Helmut Kessmann Theodor Staub John Ryals 《The Plant journal : for cell and molecular biology》1996,10(1):71-82
Benzothiadiazole (BTH) is a novel chemical activator of disease resistance in tobacco, wheat and other important agricultural plants. In this report, it is shown that BTH works by activating SAR in Arabidopsis thaliana. BTH-treated plants were resistant to infection by turnip crinkle virus, Pseudomonas syringae pv ‘tomato’ DC3000 and Peronospora parasitica. Chemical treatment induced accumulation of mRNAs from the SAR-associated genes, PR-1, PR-2 and PR-5. BTH treatment induced both PR-1 mRNA accumulation and resistance against P. parasitica in the ethylene response mutants, etr1 and ein2, and in the methyl jasmonate-insensitive mutant, jar1, suggesting that BTH action is independent of these plant hormones. BTH treatment also induced both PR-1 mRNA accumulation and P. parasitica resistance in transgenic Arabidopsis plants expressing the nahG gene, suggesting that BTH action does not require salicylic acid accumulation. However, because BTH-treatment failed to induce either PR-1 mRNA accumulation or P. parasitica resistance in the non-inducible immunity mutant, nim1, it appears that BTH activates the SAR signal transduction pathway. 相似文献
105.
Balzer Sandrock Karen M. Hudson Douglas E. Williams Michael A. Lieberman 《In vitro cellular & developmental biology. Animal》1996,32(4):225-233
Summary The regulation of megakaryopoeisis by cytokines is not yet well understood. It is possible that autocrine loops are established
during megakaryocyte growth and differentiation, aiding in the maturation of these cells. The CHRF-288-11 human megakaryoblastic
cell line has been examined for cytokine production in growing cells and cells stimulated to differentiate by the addition
of phorbol esters. It has been demonstrated that these cells produce RNA corresponding to the interleukins IL-1α, 1β, 3, 7,
8, and 11, granulocyte-macrophage colony stimulating factor (GM-CSF), stem cell factor (SCF), transforming growth factor-β
(TGF-β), tumor necrosis factor-α (TNF-α), interferon-α (INF-α), and basic fibroblast growth factor (bFGF). Additionaly, RNA
corresponding to the receptors for IL-6, GM-CSF, SCF, INF-α,β, bFGF, and monocyte colony stimulating factor (M-CSF) were also
expressed by the cells. The receptor for TNF-α was detected immunologically. Analysis at the protein level demonstrated that
significant amounts of INF-α, TNF-α, GM-CSF, SCF, IL-1α, and a soluble form of the IL-6 receptor were produced by the cells.
Addition of phorbol esters to CHRF-288-11 cells enhances their megakaryocytic phenotype; such treatment also results in increased
secretion of INF-α, TNF-α, and GM-CSF. These results suggest that potential autocrine loops are established during the differentiation
of CHRF-288-11 cells, which may alter the capability of the cell to differentiate. These findings are similar to those recently
obtained for marrow-derived megakaryocytes (Jiang et al.) suggesting that CHRF-288-11 cells provide a useful model system
for the study of cytokine release during megakaryocyte differentiation. 相似文献
106.
Francisco Berguido Michelle Kagey Charles F. Howard Jr. Susan R. Stapleton 《Primates; journal of primatology》1995,36(3):423-429
Members of the monkey speciesMacaca nigra spontaneously develop impairments in insulin secretion and glucose clearance, and eventually become overtly diabetic. Changes
in certain metabolic signals such as clearance of glucose and insulin increment secreted in an intravenous glucose tolerance
test have allowed the identification of four stages in the progression from non-diabetes to diabetes in monkeys — non-diabetic,
hormonally impaired, borderline diabetic, and diabetic. Recently, another metabolic stage, hyperinsulinemic, was also identified
in these animals. In recent years, other factors besides those listed above have been implicated to be correlated with the
metabolic progression from a nondiabetic to a diabetic state. One of these factors, is insulin like growth factor I (IGF-I).
In diabetic humans who are in poor metabolic control, and in rats with streptozotocin induced ketotic diabetes, serum levels
of IGF-I are lowered by as much as 40–50% of control non-diabetics. If indeed decreased IGF-I levels are correlated with the
onset of diabetes then changes in IGF-I concentrations prior to the clinically diagnosed disease state would be expected.
Using serum samples collected from different animals in a colony ofMacaca nigra in a variety of metabolic states, we have found that IGF-I and insulin levels decrease in each defined metabolic state as
the animals progress from nondiabetic to diabetic. Since IGF-I and insulin levels decrease in a similar fashion in the progression
of this disease then this maybe indicative of the coordinate expression of these two factors. 相似文献
107.
Jean-Frédéric Brun Rosine Guintrand-Hugret Colette Fons Joseph Carvajal Christine Fedou Michelle Fussellier Lucette Bardet André Orsetti 《Biological trace element research》1995,47(1-3):385-391
Zinc improves both insulin secretion and insulin sensitivity, and exerts insulin-like effects. We investigated its acute effects on the parameters of glucose assimilation determined with the minimal model technique from frequent sampling intravenous glucose tolerance test (FSIVGTT) in seven healthy volunteers. FSIVGTTs (0.5 g/kg of glucose, followed by 2 U insulin iv injection at 19 min) were performed after the subjects had taken 20 mg zinc gluconate twice (the evening before and 30 min before the beginning of the test) or placebo pills (simple blind randomized protocol). Glucose assimilation was analyzed by calculating Kg (slope of the exponential decrease in glycemia), glucose effectiveness Sg (i.e., ability of glucose itself to increase its own disposal independent of insulin response), and SI (insulin sensitivity, i.e. the effect of increases in insulinemia on glucose disposal). The two latter parameters were calculated by fitting the experimental data with the two equations of Bergman’s “minimal model”. Zinc increased Kg (p<0.05) and Sg (p<0.05), whereas SI and insulin first-phase secretion did not significantly increase. This study suggests that zinc improves glucose assimilation, as evidenced by the increase in Kg, and that this improvement results mainly from an increase in glucose effectiveness (insulin-like effect), rather than an action on insulin response or insulin sensitivity. 相似文献
108.
Hydroxyl Radical-Mediated Oxidation of Serotonin: Potential Insights into the Neurotoxicity of Methamphetamine 总被引:1,自引:1,他引:0
Monika Z. Wrona Zhaoliang Yang Michelle McAdams Susan O'Connor-Coates Glenn Dryhurst 《Journal of neurochemistry》1995,64(3):1390-1400
Abstract: When incubated with a hydroxyl radical (HO?)-generating system (ascorbic acid/Fe2+-EDTA/O2/H2O2), 5-hydroxytryptamine (5-HT; serotonin) is rapidly oxidized initially to a mixture of 2,5-, 4,5-, and 5,6-dihydroxytryptamine (DHT). The major reaction product is 2,5-DHT, which at physiological pH exists as its keto tautomer, 5-hydroxy-3-ethylamino-2-oxindole (5-HEO). Rapid autoxidation of 4,5-DHT gives tryptamine-4,5-dione (T-4,5-D), which reacts with the C(3)-centered carbanion of 5-HEO to give 3,3′-bis(2-aminoethyl)-5-hydroxy-[3,7′-bi-1H-indole]-2,4′,5′-3H-trione (7). The latter slowly cyclizes to 3′-(2-aminoethyl)-1′,6′,7′,8′-tetrahydro-5-hydroxyspiro[3H-indole-3,9′-[9H]pyrrolo[2,3-f]quinoline]-2,4′,5′(1H)- trione (9). A minor amount of T-4,5-D dimerizes to give 7,7′-bi-(5-hydroxytryptamine-4-one) (7,7′-D). In the presence of GSH, the reaction of T-4,5-D with 5-HEO is diverted and, in the presence of sufficient concentrations of this tripeptide, completely blocked. This is because GSH preferentially reacts with T-4,5-D to give 7-S-glutathionyltryptamine-4,5-dione (11). The results of this investigation suggest that 5,6-DHT, 5-HEO, 7, and 9 are products unique to the HO?-mediated oxidation of 5-HT. Thus, the observation of other investigators that 5,6-DHT is formed in the brains of rats following a large dose of methamphetamine (MA) suggests that this drug might evoke HO? formation. However, the present in vitro study indicates that 5,6-DHT is a rather minor, unstable product of the HO?-mediated oxidation of 5-HT and suggests that detection of 5-HEO, 7/9, and 11 in rat brain following MA administration could provide additional support for HO? formation. Furthermore, one or more of the intermediates and major products of oxidation of 5-HT by HO? might, in addition to 5,6-DHT, contribute to the MA-induced degeneration of serotonergic neurons. 相似文献
109.
An analytic expression for the expected nucleotide diversity is obtained for a neutral locus in a region with deleterious mutation and recombination. Our analytic results are used to predict levels of variation for the entire third chromosome of Drosophila melanogaster. The predictions are consistent with the low levels of variation that have been observed at loci near the centromeres of the third chromosome of D. melanogaster. However, the low levels of variation observed near the tips of this chromosome are not predicted using currently available estimates of the deleterious mutation rate and of selection coefficients. If considerably smaller selection coefficients are assumed, the low observed levels of variation at the tips of the third chromosome are consistent with the background selection model. 相似文献
110.
Alexander A. Kortt Robin E. Guthrie Mark G. Hinds Barbara E. Power Neva Ivancic J. Bruce Caldwell L. Clem Gruen Raymond S. Norton Peter J. Hudson 《Journal of Protein Chemistry》1995,14(3):167-178
The VH domain of anti-influenza neuraminidase antibody NC41, with and without a C-terminal hydrophilic marker peptide (FLAGTM), has been expressed in high yield (15–27 mg/L) inEscherichia coli. Both forms were secreted into the periplasm where they formed insoluble aggregates which were solubilized quantitatively with 2 M guanidine hydrochloride and purified to homogeneity by ion-exchange chromatography. The VH-FLAG was composed of three isoforms (pI values of 4.6, 4.9, and 5.3) and the VH molecule was composed of two isoforms with pI values of 5.1 and 6.7; the difference between the VH isoforms was shown to be due to cyclization of the N-terminal glutamine residue in the pI 5.1 isoform. At 20°C and concentrations of 5–10mg/ml the VH domain dimerized in solution and then partly precipitated, resulting in the broadening of resonances in its1H NMR spectrum. Reagents such as CHAPS,n-octylglucoside, and ethylene glycol, which presumably mask the exposed hydrophobic interface of the VH molecule, prevented dimerization of the VH and permitted good-quality NMR spectra on isotope-labeled protein to be obtained. 相似文献