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81.
椭圆法用于阳极溶出伏安法测定微量银 总被引:6,自引:1,他引:6
用新物理量Vop的椭圆法对阳极溶出伏安法分析的含银离子浓度为10^5-10^-9mol/L的一系列溶液进行了研究。结果表明:光学方法与电化学方法所得分析结果相同;椭圆法可检测的浓度下限比电化学方法低一个数量级以上。而且测量的相对平均偏差也小于电化学方法。 相似文献
82.
本文报导了与硅原子直接相连的有机基团(R)对杂氮硅三环成环速率的影响。利用气相色谱检测成环反应的产物之一——乙醇的生成速率和数量,并同与硅相连的R基团对成环反应速率的影响作比较。实验结果表明五种杂氮硅三环成环速度顺序为Cl_2CH—>ClCH_2—>ClCH_2CH_2CH_2—>CH_2=CH—>CH_3—,这与理论推断相符。 相似文献
83.
Giampiero Bettinetti Milena Sorrenti Laura Catenacci Franca Ferrari Silvia Rossi Ilaria Salvadeo Paolo Carraro 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):329-332
Triacetyl α-cyclodextrin, triacetyl β-cyclodextrin and triacetyl γ-cyclodextrin were tested as possible hydrophobic carriers
to prolong the release of hydrophilic teicoplanin (TCP). Physical–chemical characterization of individual components, drug-carrier
physical mixtures at 0.5, 0.67 and 0.75 mass fraction of carrier, and the respective interaction products by kneading or evaporative
crystallization under microwave irradiation was carried out using differential scanning calorimetry (DSC) and thermogravimetric
analysis (TGA). In vitro drug release in pH 7.4 phosphate buffer at 37 °C was determined by intrinsic dissolution rate (IDR)
measurements on non disintegrating compressed discs. Solid-state interactions of TCP with triacetyl α-cyclodextrin by evaporative
crystallization and kneading and with triacetyl β-cyclodextrin by evaporative crystallization (probably resulting in carrier
amorphization) were demonstrated. The role of carrier hydrophobicity, carrier mass fraction and preparation method of solid
drug-carrier combinations on solid-state drug-carrier interactions and slowing down of TCP release was assessed. Modulation
of drug release can be achieved using TCP-triacetyl γ-cyclodextrin combinations at 0.5 mass fraction of carrier. 相似文献
84.
Ronny Kleinhempel Gunar Kaune Matthias Herrmann Hartmut Kupfer Walter Hoyer Frank Richter 《Mikrochimica acta》2006,156(1-2):61-67
Indium tin oxide (ITO) thin films were deposited by mid frequency pulsed dual magnetron sputtering using a metallic alloy
target with 10 wt.% tin in an atmosphere of argon and oxygen. The aim of the work was to study the interdependence of structural,
electrical and optical properties of ITO films deposited in the reactive and transition target mode, respectively. The deposition
rate in the transition mode exceeds the deposition rate in the reactive mode by a factor of six, a maximum value of 100 nm·m min−1 could be achieved. This corresponds to a static deposition rate of 200 nm min−1. The lowest electrical resistivity of 1.1·10−3 Ω cm was measured at samples deposited in the high oxygen flow range in the transition mode. The samples show a good transparency
in the visible range corresponding to extinction coefficients being below 10−2. X-ray diffraction was used to characterise crystalline structure as well as film stress. ITO films prepared in the transition
mode show a slightly preferred orientation in (211) direction, whereas films deposited in the reactive mode are strongly (222)
oriented. Compared to undoped In2O3 all samples have an enlarged lattice. The lattice strain perpendicular to the surface is about 0.8% and 2.0% for films grown
in the transition and the reactive mode, respectively. Deposition in the transition mode introduces a biaxial film stress
in the range of −300 MPa, while stress in reactive mode samples is −1500 MPa. 相似文献
85.
甲醇的裂解产物为H_2与CO,故甲醇被视为一种方便、安全的贮氢材料,可作为汽油的代用燃料;其裂解气作为保护气氛可广泛应用于热处理工业。甲醇裂解有两种方法,高温热裂解(约930℃)与低温催化裂解(约300℃)由于低温催化裂解有诸多优点,在工业上的应用正在发展。 相似文献
86.
Cheng-Fang Ou 《European Polymer Journal》2002,38(3):467-473
The crystallization characteristics of polypropylene (PP) and low ethylene content PP copolymers with and without nucleating agents were studied by differential scanning calorimetry (DSC). PP and PP copolymers was blended with three different kinds of co[poly(butylene terephthalate-p-oxybenzoate)] copolyesters, designated B28, B46, and B64, with the copolyester level varying from 5 to 15 wt.%. All samples were prepared by solution blending in hot xylene solvent at 50 °C. The crystallization behavior of samples was then studied by DSC. The results indicate that these three copolyesters accelerate the crystallization rate of PP and PP copolymers in a manner similar to that of a nucleating agent. The acceleration of crystallization rate was most pronounced in these blend systems with a maximum level at 5 wt.% of B28. The observed changes in crystallization behavior are explained by the effect of the composition and the amount of copolyester in the blends. 相似文献
87.
The influence of the pH of precipitation and the ionic medium nature on the composition, surface charge, and kinetic sorption characteristics of aluminum oxyhydroxides formed by alkaline hydrolysis of an aqueous solution of aluminum nitrate was studied. The methods of drop titration with alkali, argentometric titration, point of zero charge, and indicator reactions of heterogeneous hydrolysis were used. The composition of the freshly precipitated hydrogels of aluminum(iii) oxyhydroxide, rate constants of heterogeneous hydrolysis of the IrCl6
2– ions as indicator reactions, and the pH of the point of zero charge were determined. The rate of indicator reactions (as for other oxyhydroxide hydrogels) depends strongly on the pH of precipitation. However, it is lower than the rates characteristics of iron(iii) and chromium(iii) oxyhydroxides obtained under similar conditions. The pH of the point of zero charge for the alumogels in a chloride medium is 8.3 and that in a sulfate medium is 9.5. 相似文献
88.
A series of acrylic ester copolymers with viologen group as pendant were synthesizedthrough the reaction of MMA-EBA (Ethenyl bromoacetate) copolymer with 4-(4'-pyridyl)-N-alkyl (or arylalkyl) pyridiniums. These viologen copolymers can exchange their anionwith NH_4PF_6 in methanol to improve their solubility in organic solvents such as DMFand acetone. Compared with the corresponding low molecular viologens, these viologencopolymers have relatively lower color development rate under UV light and fade fasterin air due to less affinity to photo-reductant and deficiency of association between theircation radicals. Their photofatigue resistant ability is also slightly better than that of lowmolecular vinlogens. 相似文献
89.
The title reaction has been used as an example to test the importance of using a hindered rotor treatment instead of a harmonic oscillator model for calculating vibrational partition functions corresponding to low-frequency internal rotation modes. First, a normal-mode analysis according to the Ayala and Schlegel's algorithm has been used to identify the internal rotation modes of methanethiol and the transition state structure. Then, after calculation of the energy barrier for each internal rotation, the corresponding hindered rotor partition functions have been calculated following the CW scheme of Chuang and Truhlar. The results show that the anharmonic treatment produces a rather modest improvement of the rate constants at room temperature or below. 相似文献
90.
Kinetics of chemiluminescence reactions of 2-methyl-6-phenylimidazo[1,2-a]pyrazin-3(7H)-one (1c, Cypridina luciferin analogue) and substituent effects of the 6-aryl group of derivatives 1 strongly suggest that the rate-determining step is a single electron transfer from an anion derived from 1 to a triplet molecular oxygen (O2) in the oxygenation process. 相似文献