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21.
Muhammad Faisal Nobuaki Sato Armando T. Quitain Hiroyuki Daimon Koichi Fujie 《国际化学动力学杂志》2007,39(3):175-180
The kinetics and pathway of hydrothermal decomposition of aspartic acid were studied using a continuous‐flow tubular reactor. The reaction was carried out in the temperature range of 200–260°C and at a pressure of 20 MPa. Deamination was the primary reaction, indicated by the presence of significant amount of ammonia, fumaric acid, or maleic acid in the products. Other reaction products were pyruvic acid, malic acid, and traces of succinic and lactic acid. Traces of alanine were also detected, showing the possibility of decomposing high‐molecular weight amino acids to obtain simple amino acids such as glycine or alanine. Results on the effect of reaction parameters demonstrated that decomposition of aspartic acid is highly temperature dependent under hydrothermal conditions. For a slight temperature difference of 60°C (from 200 to 260°C), the first‐order reaction rate constants of 0.003 significantly increased to 0.231 s?1. The activation energy was 144 kJ/mol, as calculated by the Arrhenius equation. No significant effect was exhibited by other reaction parameters such as pH and pressure. The results are useful in controlling the hydrolysis of proteinaceous materials toward high yield of aspartic acid under hydrothermal conditions. © 2007 Wiley Periodicals, Inc. 39: 175–180, 2007 相似文献
22.
The oxodiperoxo complexes of Mo(VI) of the type [MoO(O2)2L], where L = Morpholinomethyl urea, morpholinomethyl thiourea, piperidinomethyl urea, piperidinomethyl thiourea, pyrrolidinomethyl
urea, and pyrrolidinomethyl thiourea have been synthesized and characterized by elemental analysis, molar conductance, IR,
UV-Vis, and TGA/DTA techniques. It is shown that the ligands coordinate to the metal ion in a symmetrical bidentate fashion
through heterocyclic nitrogen and carbonyl oxygen or thiocarbonyl sulfur. Thermal studies indicate continuous weight loss
until a stable oxide is formed.
The text was submitted by authors in English. 相似文献
23.
Muhammad Taher Abuelma'atti 《International Journal of Infrared and Millimeter Waves》1995,16(2):391-400
A Fourier-series model describing the current-voltage characteristic of a quantum-well diode (QWD) is presented. Using this model, closed-form expressions are obtained for the harmonic and intermodulation performance of a QWD excited by a multisinusoidal voltage superimposed on a dc voltage. 相似文献
24.
25.
Ding LP Yuan YX Farooq S Bhatia SK 《Langmuir : the ACS journal of surfaces and colloids》2005,21(2):674-681
A dual resistance model with distribution of either barrier or pore diffusional activation energy is proposed in this work for gas transport in carbon molecular sieve (CMS) micropores. This is a novel approach in which the equilibrium is homogeneous, but the kinetics is heterogeneous. The model seems to provide a possible explanation for the concentration dependence of the thermodynamically corrected barrier and pore diffusion coefficients observed in previous studies from this laboratory on gas diffusion in CMS. The energy distribution is assumed to follow the gamma distribution function. It is shown that the energy distribution model can fully capture the behavior described by the empirical model established in earlier studies to account for the concentration dependence of thermodynamically corrected barrier and pore diffusion coefficients. A methodology is proposed for extracting energy distribution parameters, and it is further shown that the extracted energy distribution parameters can effectively predict integral uptake and column breakthrough profiles over a wide range of operating pressures. 相似文献
26.
Gábor Blaskó S.Fazal Hussain Alan J. Freyer Maurice Shamma 《Tetrahedron letters》1981,22(33):3127-3130
The dark yellow indenobenzazepine alkaloids lahorine () and lahoramine () have been found in Lam. (Fumariaceae). In a transformation with biogenetic implications, treatment of the spirobenzylisoquinolines dihydrofumariline () and dihydroparfumidine () with methanesulfonyl chloride and triethylamine in dry THF, followed by iodine oxidation, provided and , respectively. 相似文献
27.
Muhammad Ilyas Sarwar Sonia Zulfiqar Zahoor Ahmad 《Colloid and polymer science》2007,285(15):1733-1739
Fluoro-aramid-based sol/gel-derived nanocomposites were synthesized by condensing a mixture of 4,4′-(hexafluoro-isopropylidene)dianiline
and 1,3-phenylenediamine with terephthaloylchloride (TPC) in dimethylacetamide. TPC was added in slight excess to produce
amide chains with carbonyl chloride end groups and then replaced with alkoxy groups using aminophenyltrimethoxysilane to develop
bonding with the silica network. Mechanical, dynamic mechanical thermal, water absorption and morphological measurements were
carried out on the thin hybrid films. Increase in the tensile strength and modulus was observed as compared to pristine polyamide.
The thermal decomposition temperature was found in the range of 400–500 °C. The water absorption was found to be reduced with
higher silica content. The glass transition temperature and the storage moduli increased with increasing silica concentration.
The maximum increase in the T
g value (345 °C) was observed with 20 wt% silica. Scanning electron microscopy revealed the uniform distribution of silica
in the matrix with an average particle size ranging from 8 to 50 nm. 相似文献
28.
Fluorotricyanomethane is prepared from potassium tricyanomethanide and perchlorylfluoride. The crystal structure of this compound (orthorhombic, space group P212121, with a=6.270, b=6.734, c=11.776 Å) has been determined by X-ray analysis. The results are discussed in relation to those of (NC)3C? X (X=? CH3, ? Cl, ? Br or ? CN). 相似文献
29.
Muhammad Mufazzal Saeed 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(2):427-433
Summary The sorption of microquantities of Tm(III) ions on washed polyurethane foam (PUF) from a mixture of aqueous solution and ethanol
containing PAN was examined. The maximum sorption of 3.18. 10-6M solution of Tm(III) ions was observed at pH 8 with 30-minute equilibration time. The optimum ratio of aqueous-ethanol phase
for the sorption of Tm(III) ions was found to be 3:1 v/v, respectively. The sorption rate of metal ions on PUF is followed a first order kinetics and obeyed the equation for an intra
particle diffusion process. The equilibrium concentration data of Tm(III) ions could be described satisfactorily by several
adsorption isotherms. The Freundlich adsorption isotherm constants 1/nand KFare 0.66±0.02 and (5.7±0.3). 10-3mol. g-1, respectively. The Langmuir isotherm constants for monolayer coverage (Q) and binding strength of sorption (b) are (2.5±0.7). 10-5mol. g-1and (1.6±0.1). 104l. mol-1, respectively. The sorption capacity derived from Dubinin-Radushkevich (D-R) isotherm is (1.7±0.2). 10-4mol. g-1and the sorption free energy (E) is 9.8±0.2 kJ. mol-1indicating chemisorption phenomena. The thermodynamic parameters indicate that the sorption of Tm(III) ions onto PUF is endothermic,
entropy driven and spontaneous in nature. 相似文献
30.
Leavitt AJ Wyrwas RB Wallace WT Serrano DS Arredondo MG Leslie LM Khan FA Whetten RL 《The journal of physical chemistry. A》2005,109(28):6218-6222
Carbon-cluster anions, CN-, are very reactive toward SO2 (sticking probability of 0.012 +/- 0.005 for C27- at 25 degrees C), in contrast to their inertness toward other common atmospheric gases and pollutants. In flow reactor experiments at ambient temperature and near atmospheric pressure, primary adsorption of SO2 by the carbon cluster anions, N = 4-60, yields CNSO2- or CN-1S-. The inferred elimination of neutral CO2 is also detected as meta-stable decay in collision-induced dissociation. At higher temperatures, the reaction of SO2 with nascent carbon clusters yields CN-1SO- as well as undetected CO. The size-dependent initial reactivity reflects the previously established structural transitions (i.e., from chain to cyclic to cage structures). Such carbon clusters are formed in sooting flames and may act as nuclei for the formation of primary soot particles and serve as models for the local structural features of active soot particle sites for black-carbon soot. The facile generation of reactive carbon-sulfide and -sulfinate units may therefore have implications for understanding the health and environmental effects attributed to the coincidence of soot and SO2. 相似文献