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81.
The synthesis of micron-sized polymer particles with a core-shell pomegranate-like morphology is presented. The proposed polymerization technique takes advantage of a reaction-induced micro-phase separation within a suspended organic liquid droplet containing monomer, a chemical initiator, a steric stabilizer, and a poor solvent for the polymer. With an increase in monomer conversion, the monomer droplet suspended in a continuous aqueous medium is transformed first into a micro-capsule with a thick pericellular membrane, and eventually into a polymer particle packed with 300-500 nm polymer sub-particles. The experimentally observed evolution of particle morphology indicates that the reaction pathway is strongly influenced by micro-phase separation and transport phenomena. In the first stage of polymerization, a pseudo-homogeneous polymerization takes place at the droplet surface, followed by a starved macro-dispersive polymerization in the inner region where polymer precipitates out from the solvent phase as nano-sized sub-particles. 相似文献
82.
Using the industrial technologies of rubber latex irradiation, hydrophilic nanoscale calcium carbonate (HNCC) slurry preparing and spray drying, we have prepared a novel ultrafine full-vulcanized powder nitrile butadiene rubber (UFPNBR)/HNCC nanocompound, in which the UFPNBR particles and HNCC particles are isolated and adhered to each other. When the UFPNBR/HNCC nanocompound powder is mixed with crude NBR, UFPNBR particles are easily dispersed well in NBR matrix because of their good compatibility, thus the HNCC particles are also dispersed in NBR matrix because of the carrier aidance of UFPNBR particles in 7 phr HNCC loading range, then the novel NBR/UFPNBR/HNCC ternary nanocomposites is fabricated. Compared with NBR/organic reagent-treated HNCC (ONCC) binary composites, the NBR/UFPNBR/HNCC ternary nanocomposites has shorter vulcanization time and better properties of abrasive resistance, oil resistance, dynamic compression properties and flame retardancy in fire. 相似文献
83.
84.
M.R. Theobald W.J. Bealey Y.S. Tang A. Vallejo M.A. Sutton 《The Science of the total environment》2009,407(23):6024-6033
The dry deposition of ammonia from the atmosphere to the surface can lead to eutrophication of sensitive ecosystems and acidification of the soil. A large proportion of the ammonia emitted from agricultural sources can be deposited within a few kilometres and, therefore, impacts of ammonia dry deposition often occur near to the source. To assess these impacts, short-range atmospheric dispersion models are often applied to simulate the emission, dispersion and deposition of ammonia. However, these models can be time-consuming to run and often require detailed input data and, therefore, for multiple assessments it is useful to have a method of screening to discard scenarios where impacts are expected to be negligible. The SCAIL model (Simple Calculation of Ammonia Impact Limits) has been developed for this purpose. SCAIL estimates the atmospheric concentration and dry deposition at the nearest edge of a sensitive ecosystem (receptor) downwind of an ammonia source. These estimates are calculated based on simple meteorological data, the emission rate of the source, land cover type and distance to the receptor. Analysis of the model predictions showed that uncertainty in the model input data leads to an uncertainty in concentration and dry deposition estimates of 25–30% and 40–45% respectively. Detailed atmospheric dispersion models will also have similar uncertainties since they use similar types of input data. Comparison of the concentration predictions with previous measurements made around eight farms showed that the model significantly underestimated concentrations although the model performance was similar to existing screening techniques. The measurement dataset was used to calibrate the SCAIL model which subsequently performed better, using independent verification data, than existing models calibrated in a similar way. The benefits of the SCAIL model are already being seen in the UK, where it is used to screen farms for potential impacts on statutory nature conservation areas. 相似文献
85.
本文讨论了实际的和理论的分选粒度下限及降低实际分选粒度下限的办法,讨论了作为微粒分选前提条件的矿浆分散的重要性以及微粒分选的主要途径。 相似文献
86.
87.
A multi-step processing technique produced large colloidal particles from whey proteins, prompting instantaneous thickening upon hydration. Analysis of the rheological characteristics and zeta potential of the modified whey suspensions of defined particle sizes allowed investigation into the role of size on ingredient functionality. Preliminarily, the modified protein powders were sieved to achieve three size ranges, and analyzes were conducted on each of the three distributions and the non-sieved fractions. Following hydration, steady and oscillatory shear analyzes were performed using a controlled stress rheometer to determine rheological characteristics. Intrinsic viscosity was determined with a capillary viscometer and application of the Huggins equation. Zeta potential was calculated from colloidal electrophoretic mobility, measured with a ZetaPALS analyser. After thorough hydration, particle-size analysis revealed a size increase of >1.3 times for each fraction. When analysed on a protein basis, increasing particle size yielded an increase to intrinsic viscosity, flow behavior index, zero shear viscosity, and a decreased zeta potential and consistency coefficient. Knowledge of the interrelationship between zeta potential, rheological properties, and particle size of the modified whey ingredient will further advance an understanding of the functionality of this protein ingredient. 相似文献
88.
One-stage photoinitiated RAFT dispersion polymerization (PRDP) has been studied. It was found that the structure of the RAFT agent has a strong influence on the particle morphology. Carboxyl-functionalized trithiocarbonates, including S,S′-bis(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (BDMAT), S-1-dodecyl-S′-(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (DDMAT), S-1-ethyl-S′-(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (EDMAT), were found to be suitable RAFT agents for preparing highly monodisperse microspheres. GPC traces suggested that the polymerization does not follow the typical controlled/living process due to the low RAFT agent concentration in comparison with photoinitiator concentration. Particle size and uniformity changed very little with a wide range of concentrations of the stabilizer and photoinitiator. Highly monodisperse microspheres were obtained even at low stabilizer concentration (5 wt% PVP). Increasing the monomer concentration led to an increase in particle diameter with an exponent of 0.63, which is similar in scale to conventional dispersion polymerization. The microspheres were monodisperse at monomer concentrations ranging from 5 to 15 wt%. 相似文献
89.
本文在低频和声频范围内研究了砂岩、大理岩及花岗岩在不同饱和液体情况下的衰减和模量随温度的变化,同时还探讨了衰减与激发频率、共振振幅的关系。并根据时温等效原理,得出了饱和原油砂岩在衰减~温度港上28℃的衰减峰应该与衰减~频率港上8.9HZ的衰减峰相对应的结论。 相似文献
90.
HPAM/柠檬酸铝胶态分散凝胶形成条件研究 总被引:34,自引:7,他引:34
采用一种简化的实验程序测定胶态分散凝胶(CDG)的转变压,用测得的转变压值作为评价参数,考察由HPAM、柠檬酸铝、硫脲、氯化钾组成的CDG的形成条件及相对强度。所考察的形成条件包括HPAM的来源和浓度,柠檬酸铝和氯化钾的浓度,pH值,绝大部分实验工作在40℃和pH=7.0的条件下进行,用一组实验考察了温度的影响(70℃和40℃)。 相似文献