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91.
A simple method of determining ultra-trace Au in natural water was presented by using graphite furnace atomic absorption spectrophotometry (GFAAS) after in situ enrichment with thiol cotton fiber (TCF). The sample solution was adjusted to pH 1.5-2.0 with HCl, then the water sample was passed through a column packed with 0.10-0.20 g TCF and the flow rate was controlled at 20-40 ml min−1. The effects of interferences, such as complexing and oxidizing agents and other elements adsorbed on TCF were overcome by chemical treatments prior to the desorption of Au. The adsorbed Au was adsorbed with 2.0 ml hot acid, then it was extracted with 1.00 ml methyl isobutylketone (MIBK). For a 5 l water sample, the detection limit of Au is 0.02 ng l−1. The relative standard deviation (R.S.D.) for the determination of 1.44 ng l−1 Au was 9.4%.The method was applied to determine ultra-trace Au both in suspended phase and soluble phase in natural water, the concentrations of total Au in natural water samples range from 0.51 to 67.82 ng l−1. The recovery of added 0.50-6.00 ng l−1 Au was 80-95%. The method is useful in prospecting for Au deposits by means of hydrogeochemical methods. The enrichment is carried out in the field, and then the determination of Au is completed later in the laboratory. 相似文献
92.
A method is developed for a stress analysis in an infinite elastic body containing two neighboring periodically cophasaly curved fibers located along two parallel lines. The stress distribution is studied when the body is loaded at infinity by uniformly distributed normal forces in the fiber direction. The investigation is carried out within the framework of a piecewise homogeneous body model with the use of exact three-dimensional equations of elasticity theory. Numerical results related to the stress distribution considered and the influence of interaction between the fibers on this distribution are given. 相似文献
93.
94.
AbbasA. Zaman 《Particle & Particle Systems Characterization》2003,20(5):342-350
Effects of a low molecular weight physically adsorbed polyethylene oxide (PEO) and the range of the electrostatic repulsion on the rheological behavior of silica dispersions (as a model system) has been investigated. Particular attention is given to the evolution of the rheological behavior with increasing the polymer concentration in the system and also effectiveness of the polymer as a dispersant under extreme conditions (high ionic strength). Results indicate that at small separation distances and low polymer coverage, the polymer chains are long enough to adsorb on the surface of two particles simultaneously causing bridging flocculation in the system and hence increasing the viscosity and linear viscoelastic functions of the dispersion. A significant increase was observed in the viscosity of the dispersion at salt concentrations high enough to eliminate electrostatics between the particles. Under these conditions,the viscosity of the system increased significantly when PEO was added to the dispersion showing that at high electrolyte concentrations, a neutral polymer such as PEO is not able to stabilize the system. 相似文献
95.
《Surface and interface analysis : SIA》2004,36(9):1304-1313
For rough heterogeneous samples, the contrast observed in XPS images may result from both changes in elemental or chemical composition and sample topography. Background image acquisition and subtraction are frequently utilized to minimize topographical effects so that images represent concentration variations in the sample. This procedure may significantly increase the data acquisition time. Multivariate statistical methods can assist in resolving topographical and chemical information from multispectral XPS images. Principal component analysis (PCA) is one method for identification of the highest correlation/variation between the images. Topography, which is common to all of the images, will be resolved in the first most significant component. The score of this component contains spatial information about the topography of the surface, whereas the loading is a quantitative representation of the topography contribution to each elemental/chemical image. The simple‐to‐use self‐modelling mixture analysis (Simplisma) method is a pure variable method that searches for the source of most differences in the data and therefore has the potential to distinguish between chemical and topographical phases in images. The mathematical background correction scheme is developed and validated by comparing results to the experimental background correction for samples with differing degrees of topography. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
96.
Sean D. Brooks M. F. Mahmood J. A. Donaldson 《Journal of Mathematical Modelling and Algorithms》2004,3(1):19-29
A numerical investigation, based on the split-step Fourier transform algorithm of all optical switching of solitons in a low
birefringent optical fiber is presented. The numerical algorithm is described in detail.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
97.
Low-loss and rugged distal tips for CO2 laser have been proposed and fabricated based on a commercially available stainless steel (St) pipe. A method of smoothening the inner surface of the St pipe with a rough inner surface is put forward. Fabrication parameters, transmission properties, and mechanical strength of the cyclic olefin polymer-coated silver hollow St distal tip are experimentally discussed. 相似文献
98.
99.
Gel polymer electrolyte (GPE) films comprising of poly(vinylidenefluoride), propylene carbonate, ethylene carbonate and zinc trifluoromethane sulfonate are prepared and characterized. The composition of GPE is optimized to contain minimum liquid components with a maximum specific conductivity of 3.94×10−3 S cm−1 at (25±1) °C. A detailed investigation on the properties such as ionic conductivity, transport number, electrochemical stability window, reversibility of Zn/Zn2+ couple and Zn/gel electrolyte interfacial stability have been carried out. The ionic conductivity follows a VTF behaviour with an activation energy of about 0.0014 eV. Cationic transport number varies from 0.51 at 25 °C to 0.18 at 70 °C. Several cells have been assembled with GPE as the electrolyte, zinc as the anode, γ-MnO2 as the cathode and their charge–discharge behaviour followed. Capacity values of 105, 82, 64 and 37 mAh/g of MnO2 have been achieved at 10, 50, 100 and 200 μA/cm2 discharge current densities, respectively. The discharge capacity values are almost constant for about 55 cycles for all values of current densities. Cyclic voltammetric study of MnO2 electrode in Zn/GPE/MnO2 cell clearly shows intercalation/deintercalation of Zn2+. 相似文献
100.
用溶胶 凝胶法以磷钼酸 (MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2 催化剂 .使用ICP、XRD、TG DTA、IR、TPD MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能 .杂多钼酸盐与TiO2 通过O2 -在TiO2 表面发生了键合 .在 6 2 3K下 ,杂多阴离子仍保持原有的Keggin结构 .CO2 在Lewis酸位Ni(Ⅱ )和Lewis碱位Ni-O -Mo的桥氧协同作用下生成CO2 卧式吸附态Ni(Ⅱ )←O - (CO)← (O--Ni) .丙烯有多种吸附态在催化剂上吸附 .在 5 6 3K、1MPa和空速 15 0 0h-1的反应条件下 ,丙烯的摩尔转化率为 3.2 % ,产物MAA选择性为 95 % . 相似文献