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91.
内皮衍生舒张因子对缺血(缺氧),再灌注(复氧)心肌的保护作用 总被引:13,自引:1,他引:12
血管内皮产生的内皮衍生舒张因子(endothelium-derived relaxing factor,EDRF)即一氧化氮(nitric oxide,NO)本工作分别在大鼠Langendorff离体心脏灌流模型和培养的大鼠心肌细胞上观察了NO、NO的前体物质L-精氨酸(L-Arg)、NO的前体物质L-精氨酸(L-Arg)、NO的合成阻断剂L-硝基精氨酸(L-NNA)对心肌缺血(缺氧)再灌注(复氧 相似文献
92.
Ronald A. Venters Chih-Chin Huang Bennett T. Farmer II Ronald Trolard Leonard D. Spicer Carol A. Fierke 《Journal of biomolecular NMR》1995,5(4):339-344
Summary The protein human carbonic anhydrase II (HCA II) has been isotopically labeled with 2H, 13C and 15N for high-resolution NMR assignment studies and pulse sequence development. To increase the sensitivity of several key 1H/13C/15N triple-resonance correlation experiments, 2H has been incorporated into HCA II in order to decrease the rates of 13C and 1HN T2 relaxation. NMR quantities of protein with essentially complete aliphatic 2H incorporation have been obtained by growth of E. coli in defined media containing D2O, [1,2-13C2, 99%] sodium acetate, and [15N, 99%] ammonium chloride. Complete aliphatic deuterium enrichment is optimal for 13C and 15N backbone NMR assignment studies, since the 13C and 1HN T2 relaxation times and, therefore, sensitivity are maximized. In addition, complete aliphatic deuteration increases both resolution and sensitivity by eliminating the differential 2H isotopic shift observed for partially deuterated CHnDm moieties. 相似文献
93.
Radical-pair decay kinetics and molecular triplet quantum yields at various magnetic fields are reported for quinone-depleted reaction centers from the photosynthetic bacterium Rhodopseudomonas sphaeroides R26. The radical-pair decay is observed by picosecond absorption spectroscopy to be a single exponential to within the experimental uncertainty at all fields. The decay time increases from 13 ns at zero field to 17 ns at 1 kG, and decreases to 9 ns at 50 kG. The orientation averaged quantum yield of formation of the molecular triplet of the primary electron donor, 3P, drops to 47% of its zero-field value at 1 kG and rises to 126% at 50 kG. Combined analysis of these data gives a singlet radical-pair decay rate constant of 5 · 107s?1, a lower limit for the triplet radical-pair decay rate constant of 1 · 108s?1 and a lower limit for the quantum yield of radical-pair decay by the triplet channel of 38% at zero field. The upper limit of the quantum yield of 3P formation at zero field is measured to be 32%. In order to explain this apparent discrepancy, decay of the radical pair by the triplet channel must lead to some rapid ground state formation as well as some 3P formation. It is proposed that the triplet radical pair decays to a triplet charge-transfer state which is strongly coupled to the ground state by spin-orbit interactions. Several possibilities for this charge-transfer state are discussed. 相似文献
94.
Purification of bacterial L-methionine gamma-lyase 总被引:1,自引:0,他引:1
A chromatographic procedure using sequential ion-exchange columns is described for separating choline, trimethylamine, trimethylamine oxide, and betaine extracted from marine fish tissues; added exogenous carnitine can also be separated by the system. Choline with its positive charge binds to the AG 50W-X8 (Na+, pH 9) column. The column is first eluted with 0.1 N NaOH to collect trimethylamine, trimethylamine oxide, and betaine; choline is then eluted with 0.5 N NaOH. The amines collected with 0.1 N NaOH are subsequently separated using an AG 50W-X8 (H+, pH 4) column eluted with a linear 0-1 M NaC1 gradient. 相似文献
95.
96.
Transfer of Lemna minor fronds to culture medium containing 50% (v/v) deuterium oxide induces a large increase in the rate of protein breakdown, which is not due to an increase in the activity of acidic or neutral proteolytic enzymes or peptidases. Biochemical and ultrastructural evidence indicates that deuterium oxide affects the properties of certain membranes, particularly the tonoplast, and allows vacuolar proteolytic enzymes to pass into the cytoplasm and cause the increased protein breakdown.Abbreviations BAPA
benzylarginine-p-nitroanilide
- LPA
leucine-p-nitroanilide
- TCA
trichloroacetic acid 相似文献
97.
Three complexes of NO with cytochrome c oxidase are described which are all photodissociable at low temperatures as measured by EPR. The EPR parameters of the cytochrome a2+3-NO complex are the same both in the fully reduced enzyme and in the mixed-valence enzyme. The kinetics of photodissociation of cytochrome a2+3-NO and recombination of NO with cytochrome a2+3 (in the 30–70 K region) revealed no differences in structure between cytochrome a2+3 in the fully reduced and the mixed-valence states. The action spectrum of the photodissociation of cytochrome a2+3-NO as measured by EPR has maxima at 595, 560 and 430 nm, and corresponds to the absorbance spectrum of cytochrome a2+3-NO. Photodissociation of cytochrome a2+3-NO in the mixed-valence enzyme changes the EPR intensity at g 3.03, due to electron transfer from cytochrome a2+3 to cytochrome a3+. The extent of electron transfer was found to be temperature dependent. This suggests that a conformational change is coupled to this electron transfer. The complex of NO with oxidized cytochrome c oxidase shows a photodissociation reaction and recombination of NO (in the 20–40 K region) which differ completely from those observed in cytochrome a2+3-NO. The observed recombination occurs at a temperature 15 K lower than that found for the cytochrome a2+3-NO complex. The action spectrum of the oxidized complex shows a novel spectrum with maxima at 640 and below 400 nm; it is assigned to a Cu2+B-NO compound. The triplet species with Δms = 2 EPR signals at g 4 and Δms = 1 signals at g 2.69 and 1.67, that is observed in partially reduced cytochrome c oxidase treated with azide and NO, can also be photodissociated. 相似文献
98.
S-亚硝基化是一种重要的蛋白质翻译后修饰方式, 是指一氧化氮(NO)基团共价连接至靶蛋白特定半胱氨酸残基的自由巯基, 从而形成S-亚硝基硫醇(SNO)的过程。S-亚硝基化修饰广泛存在于各有机体中, 通过改变蛋白质生化活性、稳定性、亚细胞定位以及蛋白质-蛋白质相互作用等机制而调控不同的生物学过程或信号通路。在蛋白质S-亚硝基化检测分析方法中, 最为广泛使用的是生物素转化法(biotin switch assay), 其基本原理是首先封闭未被修饰的自由巯基, 进而将被修饰的SNO基团特异地还原为自由巯基并使用生物素将其特异标记。被生物素标记的半胱氨酸残基(即被修饰位点)可进一步通过蛋白质免疫印迹和/或质谱等方法进行检测分析。该文详细描述了植物蛋白质样品的体内和体外生物素转化法的实验流程, 并对实验过程中的注意事项进行了讨论。 相似文献
99.
Weber AL 《Journal of molecular evolution》1992,35(1):1-6
Summary Iron(III) hydroxide oxide [Fe(OH)O] efficiently catalyzed the condensation of 25 MM dl-glyceraldehyde to ketohexoses at 25°C (pH 5–6). At 16 days the yields were sorbose (15.2%), fructose (12.9%), psicose (6.1%), tagatose (5.6%), and dendroketose (2.5%) with 19.6% of triose unreacted. Analysis at 96 days showed no decomposition of hexoses. Under these conditions Fe(OH)O also catalyzed the isomerization and rearrangement of glyceraldehyde to dihydroxyacetone and lactic acid, respectively. In these reactions, about 10% of the glyceraldehyde was oxidized to glyceric acid with concurrent reduction of the iron(III) to iron(II). The partial reduction of Fe(OH)O did not noticeably reduce its ability to catalyze hexose synthesis. The relationship of these results to prebiotic sugar synthesis is discussed. 相似文献
100.
An experimental investigation of the low hydration phase properties of phospholipid mixtures is described. 2H (D2O) NMR, X-ray diffraction and differential scanning calorimetry have been used to elucidate the phase properties of mixtures of the mixed chain phospholipids palmitoyloleoylphosphatidylcholine (POPC) and palmitoyloleoylphosphatidylethanolamine (POPE). At 10% hydration pure POPE exhibited a HII phase above 330 K, a fluid lamellar phase below 315 K, and a minimally hydrated crystalline phase below 300 K. For the 1:1 mixture, the samples exhibited only gel or fluid phases between 270 K and 360 K for hydrations in the range 15% to 30%. Below 15% hydration the mixture exhibited two fluid phases with different repeat spacings, as predicted previously. 相似文献