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971.
Thin films of bis(dimethylglyoximato)palladium(II) complex of polycrystalline structure were prepared by sublimation in a vacuum at 140 °C, on glass and p-Si substrates. The films were characterised by spectral optical absorption, energy dispersion X-ray fluorescence (EDXRF), and X-ray diffraction (XRD) methods. After characterisation, metal-insulator (complex)-semiconductor MIS devices were fabricated to measure the frequency dependence of ac-conductivity in a range of 5-100 kHz. Data of ac-measurements follow the correlated barrier-hopping CBH model, from which one of the fundamental absorption peaks, the minimum hopping distance, and other parameters of the CBH model were determined, connecting and relating the optical, structural, and electrical measurements. The dielectric properties of the complex were studied through Debye model, from which the relaxation time for the dipoles (2.45 × 10−6 s) and the molecular dipole moment (3.63 × 10−30 C m ) were determined. 相似文献
972.
973.
环多肽晶体的浮动电荷极化力场模拟 总被引:2,自引:0,他引:2
利用原子键电负性均衡结合分子力场方法(ABEEM/MM)对五种环多肽晶体进行了研究. 与传统力场相比, 该方法中的静电势包含了分子内和分子间的静电极化作用, 以及分子内电荷转移影响, 同时加入了化学键等非原子中心电荷位点, 合理地体现了分子中的电荷分布. 相对其他极化力场模型, 具有计算量较小的特点. 该模型下计算得到的环多肽分子单元相对实验测得的结构的原子位置、氢键长度和二面角的均方根偏差分别为0.009 nm、0.013 nm和5.16°, 能够很好地重复实验结果. 总体上, 其结果优于或相当于其他力场模型, 适用于对实际蛋白质体系的模拟和研究. 相似文献
974.
流动注射双安培法测定多巴胺 总被引:5,自引:0,他引:5
通过偶合多巴胺在铂电极上的氧化和高锰酸钾在铂电极上的还原,建立了一个不施加电压的条件下的流动注射双安培法直接测定多巴胺的新方法。以0.05 mol/L硫酸为载液,多巴胺的氧化峰电流与其浓度在0.8~160 mg/L范围内呈线性关系,线性回归方程为i(nA)=652.9C-239.2(r=0.9998,n=10),检出限为0.2 mg/L;RSD为2.86%(N=80 mg/L,n=14);进样频率为80次/h。本方法具有很高的选择性和灵敏度,样品处理方法简单快速,适于连续自动测定。用于实际样品的测定,结果满意。 相似文献
975.
976.
Guang-hui Cai 《Journal of mathematical chemistry》2008,43(1):375-385
Consider the partly linear regression model Y = xβ + g(t) + e where the explanatory x is erroneously measured, and both t and the response Y are measured exactly, the random error e is ρ−-mixing. Let be a surrogate variable observed instead of the true x in the primary survey data. Assume that in addition to the primary data set containing N observations of , which is ρ−-mixing data sets, an independent validation data containing n observations of is available. The exact observations on x may be obtained by some expensive or diffcult procedures for only a small subset of subjects enrolled in the study. In this
paper, inspired by Berberan-Santos et al. [J. Math. Chem. 37 (2005)101], a semiparametric method with the primary data is
employed to obtain the estimators of β and g(·) based on the least squares criterion with the help of validata. The proposed estimators are proved to be strongly consistent.
相似文献
977.
Sancheeta Kolay Kallol K. Ghosh Amy MacDonald Jonathan Moulins Rama M. Palepu 《Journal of solution chemistry》2008,37(1):59-72
The thermodynamics of micellization and other micellar properties of alkyl- (C10-, C12-, C14- and C16-) triphenylphosphonium bromides in water + ethylene glycol (EG) (0 to 30% v/v) mixtures over a temperature range of 298 to
318 K and cetyltriphenylphosphonium bromide in water + diethylene glycol (DEG) mixtures (0 to 30% v/v) at 298 K have been
studied conductometrically. In all cases, an increase in the percentage of co-solvent results in an increase in the cmc values.
On the basis of these results, the thermodynamic parameters, the Gibbs energy (ΔG
mo), enthalpy (ΔH
mo) and entropy (ΔS
mo) of micellization have been evaluated. In addition to the conductivity measurements, kinetic experiments have also been done
to determine the dependence of observed rate constant for the nucleophilic substitution reaction of p-nitrophenyl acetate and benzohydroxamate ions in the presence of the surfactant cetyltriphenylphosphonium bromide with a
varying concentration of EG and DEG ranging from 0 to 50% v/v at pH=7.9 and 300 K. All of the reactions followed pseudo-first-order
kinetics. An increase in the surfactant concentration results in an increase in the reaction rate and for a given surfactant
concentration, the rate constant decreases as the concentration of co-solvent in the mixture increases. The kinetic micellar
effects have been explained by using the pseudophase model. The thermodynamic and structural changes originating from the
presence of solvents control the micellar kinetic effects. 相似文献
978.
Design of a field flow system for the on-line spectrophotometric determination of phosphate, nitrite and nitrate in natural water and wastewater 总被引:1,自引:0,他引:1
Ioannis A. Tsoulfanidis George Z. Tsogas Dimosthenis L. Giokas Athanasios G. Vlessidis 《Mikrochimica acta》2008,160(4):461-469
This study describes the design and optimisation of a field flow system for the in-situ collection and on-line determination
of phosphate, nitrate and nitrite by flow injection analysis-spectrophotometry. The method is based on the initial determination
of phosphate as its phosphoantimonylmolybdenum blue complex which is then oxidized on-line by nitrite and the decrease in
absorbance is monitored at 880 nm. Nitrate is determined as the difference between total and initial nitrite content in a
separate flow after reduction to nitrite in a cadmium reductive column. The calibration curves were linear in the range 0–2.00 mg L−1 P-phosphate, 0–10.00 mg L−1 nitrite and 0–7.00 mg L−1 nitrate with correlation coefficients of 0.9979, 0.9993 and 0.9995, respectively. The detection limits, calculated as 3S/N,
were 0.15 mg L−1 for P-phosphate, 0.17 mg L−1 for nitrite and 0.09 mg L−1 for nitrate. The reproducibility was below 3.0% (n = 7). Method validation in the analysis of natural water and wastewater samples revealed that it can efficiently be applied
to the determination of the target analytes, with recoveries in the range of 92–108%.
Correspondence: Athanasios G. Vlessidis, Laboratory of Analytical Chemistry, Department of Chemistry, University of Ioannina,
Ioannina 45110, Greece 相似文献
979.
Reverse flow injection spectrophotometric determination of iron(III) using chlortetracycline reagent
Ruengsitagoon W 《Talanta》2008,74(5):1236-1241
A simple reversed flow injection colourimetric procedure for determining iron(III) was proposed. It is based on the reaction between iron(III) with chlortetracycline, resulting in an intense yellow complex with a suitable absorption at 435 nm. A 200 μl chlortetracycline reagent solution was injected into the phosphate buffer stream (flow rate 2.0 ml min−1) which was then merged with iron(III) standard or sample in dilute nitric acid stream (flow rate 1.5 ml min−1). Optimum conditions for determining iron(III) were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range 0.5–20.0 μg ml−1. The detection limit (3σ) and the quantification limit (10σ) were 0.10 and 0.82 μg ml−1, respectively. The relatives standard deviation of the proposed method calculated from 12 replicate injections of 2.0 and 10.0 μg ml−1 iron(III) were 0.43 and 0.59%, respectively. The sample throughput was 60 h−1. The proposed method has been satisfactorily applied to the determination of iron(III) in natural waters. 相似文献
980.
采用微分脉冲阳极溶出伏安法, 研究了Ag+、Cu2+、Pb2+、Sn2+、Cd2+等多种共存金属离子在掺硼金刚石(BDD)表面双金属共沉积-共溶出电化学行为. 结果表明, 双金属在掺硼金刚石膜表面的共沉积-共溶出模型是由金属本身的析出电位, 金属之间的相互作用, 金属离子和溶液间的相互作用等多种因素决定的. 微分阳极溶出法的研究结果表明, 双金属在掺硼金刚石电极上的共沉积-共溶出过程表现出金属1溶出-金属2溶出、金属1溶出-析氢-金属2溶出、金属1溶出-金属合金溶出-金属2溶出、金属1溶出-析氢-金属2络合物形成-金属2溶出等四种模型. 相似文献