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991.
Bongliba T. Sangtam 《Petroleum Science and Technology》2013,31(18):1432-1438
AbstractTo prevent the plug of hydrate it is important to study the relationship between temperature and pressure at which hydrate form and dissociate. An empirical correlation was developed to predict the equilibrium condition to form the gas hydrate with and without presence of inhibitors. Overall 600 data points of equilibrium, to form gas hydrate have used to obtain the empirical correlation. The overall average absolute deviations are found to have good agreement with the experimental data. The present study may be helpful for further understanding the correlation of gas hydrate formation equilibrium condition. 相似文献
992.
Anti-encrustation additives were mainly investigated in nitric acid solution with zirconium (Zr), molybdenum (Mo), and tellurium (Te) to prevent the encrustation of zirconium molybdate hydrate (ZMH). The ZMH generated by reaction crystallization of Mo and Zr as main fission products has a high adhesion property in spent nuclear fuel reprocessing. In addition, it is reported that Te, which is also one of the fission products, precipitates together with ZMH. Encrustation of precipitates containing Te was effectively prevented by adding molybdenum trioxide (MoO3) crystals as an anti-encrustation reagent. The encrustation amount was found to be larger than that under the condition of only Zr and Mo without Te. Consequently, it was suggested that the high adhesion property of Te affected the encrustation amount of ZMH. 相似文献
993.
994.
The vanadium(IV) ion is found to form the [VO(SO4)(H2O)4]·H2O complex, as well as the dimer, [VO(H2O)3]2(μ-SO4)2, in concentrated H2SO4 media. Their formation mechanisms were investigated by UV–Visible spectroscopy (UV–Vis), Raman spectroscopy, X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). UV–Vis spectroscopy study showed that [VO(SO4)(H2O)4]·H2O concentration in H2SO4 solution was proportional to concentrations of VO2+ and SO42−. The increased deviation from the near centrosymmetry of the octahedral complexes is due to the replacement of an equatorial water oxygen in [VO(H2O)5]SO4 by a sulfate oxygen in [VO(SO4)(H2O)4]·H2O. The dimer shows symmetrical structure, which correlates very well with non-activity in UV–Vis spectroscopic analysis. Structural information on both vanadium(IV) species can be confirmed by Raman and XRD measurements of crystals from the supersaturated solution of VOSO4 in 1 M, 6 M and 12 M sulfuric acid. A solution of vanadium(IV) (0.05 M) in 12 M H2SO4, in which the vanadium(IV) species is [VO(H2O)3]2(μ-SO4)2, exhibits a reversible redox behavior near 1.14 V (vs. SCE) on the carbon paper electrode. 相似文献
995.
Hamidreza Sefidroodi Pei Cheng Chua Malcolm A. Kelland 《Chemical engineering science》2011,66(10):3289
Small, cationic tetraalkylammonium ions (particularly for alkyl=butyl or pentyl) are known to inhibit tetrahydrofuran (THF) and natural gas hydrate crystal growth and have been used as synergists for commercial kinetic hydrate inhibitor polymers (KHIs), such as N-vinylcaprolactam polymers, for a number of years. The ability for small, organic anionic molecules to inhibit (THF) hydrate crystal growth and their potential as KHI synergists in blends with poly(N-vinylcaprolactam) have been investigated. Several series of sodium alkyl carboxylates, sulphates and sulphonates were synthesised. It was found that none of these molecules were capable of inhibiting THF hydrate crystal growth as well as the best tetraalkylammonium salts. Alkyl carboxylates appeared to be more effective as inhibitors than the sulphonates or sulphates. The most effective anionic THF hydrate crystal growth inhibitors had butyl or pentyl groups, with alkyl branching at the tail (i.e. iso- rather than n-isomers) being advantageous. Anionic carboxylate molecules, particularly with isopentyl or isobutyl groups, showed some kinetic inhibition synergy with poly(N-vinylcaprolactam) lowering the onset and catastrophic hydrate formation temperatures in high pressure (78 bar) constant cooling experiments with Structure II hydrates by 1–2 °C when dosed at 2500 ppm compared with using 2500 ppm polymer alone. This synergism was however less than the best tetraalkylammonium salts (alkyl=n-butyl or n-pentyl) at the same test conditions. Sodium butyl sulphonate and sodium 4-methylpentanoate did not prevent hydrate agglomeration with 3.6% brine and decane at 25% water cut in stirred sapphire cells when dosed at 20,000 ppm based on the aqueous phase, whereas 10,000–20,000 ppm active material of several commercially available anti-agglomerants gave fine transportable slurries and no hydrate deposits at the same conditions. 相似文献
996.
997.
998.
Time‐dependent isochoric formation of methane hydrate was investigated in the presence of low‐dose poly(ethylene oxides) (PEOs). The effect of different molecular weights of PEO on methane hydrate nucleation time and storage capacity was studied and compared. Kinetic measurements revealed a dual effect of PEO, including inhibition and stabilization effects, on methane hydrate formation. The nature and type of the effect arises from the difference in molecular weights and concentration ranges of PEOs. These parameters directly affect the nucleation time and storage capacity of methane hydrate. Generally, in comparison with pure water, PEO improved the storage capacity of methane hydrate. PEO (1000 kD) at a concentration of 0.5 wt % exhibits a significant kinetic inhibitory performance. However, it was an efficient low‐dosage hydrate stabilizer at a concentration of 0.25 wt %, along with producing gas‐rich methane hydrate suitable for gas fuel storage and transportation. 相似文献
999.
1000.
激励及地电条件与天然气水合物的电偶源电场响应 总被引:5,自引:0,他引:5
海底天然气水合物电磁勘探采用动态水平电偶源发射与静态阵列式海底偶极接收的测量方式。基于一维地电模型,求解海底水平层状介质的电偶源电场响应,得到海底两个水平正交电场的传播表达式,据此研究天然气水合物电场响应的影响因素。对供电频率、电偶源离地高度、海水深度、覆盖层厚度以及天然气水合物地层自身的物理化学结构等因素与归一化电场幅值的关系分别进行了计算分析,结果显示:调整供电频率可使归一化电场幅值变化于10-16~10-10V/(A.m2);将电偶源施放至离海底数十米高度进行拖曳可获得较好的作业效果,且不改变信号采集的质量;深水及浅薄覆盖层属于有利的探测环境,该环境下的感应场源具有较高的信噪比;天然气水合物的孔隙度、饱和度影响介质电阻率值,其电阻率越高,电场响应幅值越大。正演模拟结果可对天然气水合物探测设备研制及海洋作业提出切实可行的设计方案。图7参22 相似文献