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201.
A mesoporous template route to the low-temperature preparation of efficient green light emitting Zn2SiO4:Mn phosphors 总被引:1,自引:0,他引:1
Xiong L Shi J Gu J Li L Huang W Gao J Ruan M 《The journal of physical chemistry. B》2005,109(2):731-735
Green light emitting Zn2SiO4:Mn phosphors have been prepared via a low-temperature solid-state reaction using mesoporous silica SBA-15 template. This mesoporous silica template method features low-temperature formation of phosphors and easy doping. The structure and morphology of the phosphors were characterized by XRD, SEM, TEM, and N2 adsorption/desorption techniques, which confirmed the single crystallinity, ordered mesostructure, closed pore channels, and elongated ropelike morphology. The luminescent properties were examined by photoluminescence spectroscopy at room temperature, and the results of fluorescence decay time measurements show non-single-exponential decay behavior and a decrease of the decay time with an increase of the Mn concentration. 相似文献
202.
Cross-coupling cyclization reaction between 2,3-allenoic acids 1 and 2,3-allenols 2, in which two allenes functioned differently, was realized to afford 4-(1',3'-dien-2'-yl)-2(5H)-furanone derivatives 3. The reaction may proceed via an oxypalladation, insertion, and beta-hydroxide elimination process. A high E-stereoselectivity of the new formed C=C double bond was observed. 相似文献
203.
INTRODUCTIONThe wicking technique has been used to determine the surface energy components of solids[1-7]. Generally, thereare two wicking processes in practice, i.e. thin layer wicking and column wicking. A comparison of the twowicking techniques made by van Oss et al.[2], shows that column wicking has a problem of showing differentpacking density due to some kinds of powder materials, i.e. clay can not give good repacking reproducibility[2].But thin layer wicking has a problem in sample… 相似文献
204.
Joo J Kwon SG Yu T Cho M Lee J Yoon J Hyeon T 《The journal of physical chemistry. B》2005,109(32):15297-15302
A simple method of synthesizing a large quantity of TiO(2) nanorods was developed. A nonhydrolytic sol-gel reaction between titanium(IV) isopropoxide and oleic acid at 270 degrees C generated 3.4 nm (diameter) x 38 nm (length) sized TiO(2) nanocrystals. The transmission electron microscopic image showed that the particles have a uniform diameter distribution. X-ray diffraction and selected-area electron diffraction patterns combined with high-resolution transmission electron microscopic image showed that the TiO(2) nanorods are highly crystalline anatase crystal structure grown along the [001] direction. The diameters of the TiO(2) nanorods were controlled by adding 1-hexadecylamine to the reaction mixture as a cosurfactant. TiO(2) nanorods with average sizes of 2.7 nm x 28 nm, 2.2 nm x 32 nm, and 2.0 nm x 39 nm were obtained using 1, 5, and 10 mmol of 1-hexadecylamine, respectively. The optical absorption spectrum of the TiO(2) nanorods exhibited that the band gap of the nanorods was 3.33 eV at room temperature, which is 130 meV larger than that of bulk anatase (3.2 eV), demonstrating the quantum confinement effect. Oleic acid coordinated on the nanorod surface was removed by the reduction of the carboxyl group of oleic acid, and the Brunauer-Emmett-Teller surface area of the resulting naked TiO(2) nanorods was 198 m(2)/g. The naked TiO(2) nanorods exhibited higher photocatalytic activity than the P-25 photocatalyst for the photocatalytic inactivation of E. coli. 相似文献
205.
Two new ent‐abietane diterpenoids, macrophynin E ( 1 ) and macrophynin F ( 2 ), and a known related ent‐abietanoid (?)‐lambertic acid ( 3 ), together with four known ent‐kauranoids, were isolated from the roots and aerial parts of Isodon macrophylla, respectively. The structures of the new compounds were elucidated on the basis of spectroscopic‐data analysis and chemical correlations. 相似文献
206.
With fluorometry this paper has proved that alpha-cyclodextrin (CD) and gamma-CD do not form inclusion complexes with procaine, while beta-CD and HP-beta-CD do. Their molar ratios are demonstrated both 1:1 with the equimolar variation method. The constant current coulometric titration method (CCCT) is first proposed and applied in the determination of the CD inclusion constant. To compare with this method, the fluorescence experiment has been done with the satisfactory results. 相似文献
207.
An amperometric cholesterol biosensor based on immobilization of cholesterol oxidase in a Prussian blue (PB)/polypyrrole (PPy) composite film on the surface of a glassy carbon electrode was fabricated. Hydrogen peroxide produced by the enzymatic reaction was catalytically reduced on the PB film electrode at 0 V with a sensitivity of 39 μA (mol/L)?1. Cholesterol in the concentration range of 10?5 ? 10?4 mol/L was determined with a detection limit of 6 × 10?7 mol/L by amperometric method. Normal coexisting compounds in the bio‐samples such as ascorbic acid and uric acid do not interfere with the determination. The excellent properties of the sensor in sensitivity and selectivity are attributed to the PB/PPy layer modified on the sensor. 相似文献
208.
Xiaoxiong Xu Zhaoyin Wen Zhonghua Gu Xiaohe Xu Zuxiang Lin 《Electrochemistry communications》2004,6(12):342
Li2O–Cr2O3–GeO2–P2O5 based glasses were synthesized by a conventional melt-quenching method and successfully converted into glass-ceramics through heat treatment. Experimental results of DTA, XRD, ac impedance techniques and FESEM indicated that Li1.4Cr0.4Ge1.6(PO4)3 glass-ceramics treated at 900 °C for 12 h in the Li1 + xCrxGe2 − x(PO4)3 (x = 0–0.8) system exhibited the best glass stability against crystallization and the highest ambient conductivity value of 6.81 × 10−4 S/cm with an activation energy as low as 26.9 kJ/mol. In addition, the Li1.4Cr0.4Ge1.6(PO4)3 glass-ceramics displayed good chemical stability against lithium metal at room temperature. The good thermal and chemical stability, excellent conducting property, easy preparation and low cost make it promising to be used as solid-state electrolytes for all-solid-state lithium batteries. 相似文献
209.
Zhonghua Ji Jingjian Li Gu Yuan Shengmin Cai Jia Liu Chang Liu 《Journal of Electroanalytical Chemistry》2004,570(2):265-273
Polyamides containing N-methyl pyrroles and N-methyl imidazoles are a type of small molecule that can bind and recognize the bases of DNA with high affinity and specificity. Five polyamides were studied at glassy carbon electrode in acetate buffer by cyclic and differential pulse voltammetry to clarify their redox pathways. The polyamide electrochemical responses are compared by peak currents and peak potentials. The slopes of the three anodic Ep vs. pH plots of a typical polyamide are linear and show 0.059, 0.057, 0.056 V per pH in acid media, respectively, which correspond to a mechanism involving the equal number of electrons and protons. A possible mechanism for the redox pathway of various polyamides is proposed: the oxidation product of imidazole ring is acylamide and the results of in situ UV–Vis spectroscopy at Pt web electrode support the proposed mechanism. electrospray ionization mass spectroscopy (ESI-MS) indicates that one or two oxygen atoms are added into polyamide molecule after electrochemical oxidation. 相似文献
210.
Deposition of spherical particles onto cylindrical solid surfaces. I. Numerical simulations 总被引:4,自引:0,他引:4
The permeability of fractal porous aggregates with realistic three-dimensional structure is investigated theoretically using model aggregates composed of identical spherical primary particles. Synthetic aggregates are generated by several techniques, including a lattice-based method, simulation of aggregation by differential settling and turbulent shear, and the specification of simple cubic structures, resulting in aggregates characterized by the number of primary particles, solid fraction, characteristic radius, and fractal dimension. Stokesian dynamics is used to determine the total hydrodynamic force on and the distribution of velocity within an aggregate exposed to a uniform flow. The aggregate permeability is calculated by comparing these values with the total force and velocity distribution calculated from the Brinkman equation applied locally and to the entire aggregate using permeability expressions from the literature. The relationship between the aggregate permeability and solid fraction is found to be best predicted by permeability expressions based on cylindrical rather than spherical geometrical elements, the latter tending to underestimate the aggregate permeability significantly. The permeability expressions of Jackson and James or Davies provide good estimates of the force on and flow through porous aggregates of known structure. These relationships are used to identify a number of general characteristics of fractal aggregates. 相似文献