全文获取类型
收费全文 | 10521篇 |
免费 | 867篇 |
国内免费 | 529篇 |
专业分类
电工技术 | 1413篇 |
综合类 | 632篇 |
化学工业 | 2875篇 |
金属工艺 | 1491篇 |
机械仪表 | 549篇 |
建筑科学 | 132篇 |
矿业工程 | 179篇 |
能源动力 | 1077篇 |
轻工业 | 336篇 |
水利工程 | 34篇 |
石油天然气 | 141篇 |
武器工业 | 46篇 |
无线电 | 766篇 |
一般工业技术 | 1140篇 |
冶金工业 | 529篇 |
原子能技术 | 102篇 |
自动化技术 | 475篇 |
出版年
2024年 | 36篇 |
2023年 | 145篇 |
2022年 | 217篇 |
2021年 | 281篇 |
2020年 | 318篇 |
2019年 | 294篇 |
2018年 | 214篇 |
2017年 | 345篇 |
2016年 | 311篇 |
2015年 | 320篇 |
2014年 | 521篇 |
2013年 | 549篇 |
2012年 | 598篇 |
2011年 | 927篇 |
2010年 | 660篇 |
2009年 | 716篇 |
2008年 | 639篇 |
2007年 | 766篇 |
2006年 | 671篇 |
2005年 | 508篇 |
2004年 | 460篇 |
2003年 | 386篇 |
2002年 | 360篇 |
2001年 | 303篇 |
2000年 | 253篇 |
1999年 | 192篇 |
1998年 | 197篇 |
1997年 | 137篇 |
1996年 | 104篇 |
1995年 | 99篇 |
1994年 | 111篇 |
1993年 | 64篇 |
1992年 | 48篇 |
1991年 | 37篇 |
1990年 | 34篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1964年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
本文旨在通过对石墨防爆片的变形、应力分布及爆破压力的试验研究,探讨以石墨电极为原材料加工石墨防爆片的可行性。文中运用有限单元法及薄板理论对该防爆破片的应力分布做了初步分析,并以电测和爆破试验验证了以薄板理论为基础的爆破压力计算公式,可供进一步研究时参考。 相似文献
102.
采用有限元法对比研究了φ500mm的日本电极和国产电极炼钢时电极-接头连接区的热应力分布,对结果进行了分析和讨论,并提出了相应的结论和建议。 相似文献
103.
The electrochemical behaviour of the chromium electrode in borate buffer solution (pH 9.3) was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Chromium passivity was observed over a broad potential region, from –1.0 to 0.5 V vs SCE. The passivation process took place in two steps: formation of a chromium oxide monolayer and transition of chromium to a higher valence state. The anodic film exhibited the properties of a p-type semiconductor. Transpassive dissolution of chromium occurred at 0.5 V vs SCE, with two reaction intermediates present, CrCr
III and Crad
4+. 相似文献
104.
The effect of dissolved oxygen on the rate of chemical etching of copper by acidic cuprous chloride solution was investigated numerically for the case of a rotating disc electrode (RDE). Copper dissolution in aerated acidic cupric chloride solutions of composition 3.5M CuCl2 + 0.5M HCl + 0.5M KCl and 3.5M CuCl2+0.5M HCl was investigated with consideration of the instantaneous homogeneous reaction 4CuCl32-+4H++O2rlhar4CuCl 3-+2H2O which takes place within the mass transport boundary layer. It was assumed that CuCl32- and O2 react instantaneously, resulting in the formation of a reaction plane which separated the mass transport boundary layer into two regions: a region adjacent to the electrode where oxygen was depleted, and a region adjacent to the bulk where CuCl32- was absent. A one-dimensional mathematical model was developed to predict the position of the reaction plane. The model accounted for diffusion, migration and fluid flow generated by an RDE and included nine species and five heterogeneous electrochemical reactions. The homogeneous redox reaction served to regenerate the chemical etchant solution and thus enhance the etch rate. With increasing oxygen concentration and rotation rate the reaction plane was found to move closer toward the electrode and thus the etch rate of copper increased. Addition of KCl increased the Cl- content in solution so as to shift the reaction plane toward the bulk. 相似文献
105.
This work provides kinetic and transport parameters of Li-ion during its extraction/insertion into thin film LiNi0.5Mn1.5O4 free of binder and conductive additive. Thin films of LiNi0.5Mn1.5O4 (0.2 μm thick) were prepared on electronically conductive gold substrate utilizing the electrostatic spray deposition technique. High purity LiNi0.5Mn1.5O4 thin film electrodes were observed with cyclic voltammetry, to exhibit very sharp peaks, high reversibility, and absence of the 4 V signal related to the Mn3+/Mn4+ redox couple. The electrode subjected to 100 CV cycles of charge/discharge delivered a capacity of 155 mAh g−1 on the first cycle and sustained a good cycling behavior while retaining 91% of the initial capacity after 50 cycles. Kinetics and mass-transport of Li-ion extraction at LiNi0.5Mn1.5O4 thin film electrode were investigated by means of electrochemical impedance spectroscopy. The apparent chemical diffusion coefficient (Dapp) value determined from EIS measurements changed depending on the electrode potential in the range of 10−10-10−12 cm2 s−1. The Dapp profile shows two minimums at the potential values close to the peak potentials of the corresponding cyclic voltammogram. 相似文献
106.
Anodic dissolution of Au is facilitated by the presence of thiourea owing to formation of strongly complexed Au ions. The present paper reports studies of this process using cyclic voltammetry (CV), chronopotentiometry and chronoamperometry, usefully complemented by nanogravimetry employing an electrochemical quartz-crystal nanobalance (EQCN). The molar masses per faraday for Au dissolution were determined from EQCN measurements, coupled with information derived from CV, chronopotentiometry and chronoamperometry, and clearly indicate that Au becomes dissolved over the potential range 0.45—0.65 V vs RHE via a 1e– oxidation process in 0.5 M HClO4 solution containing thiourea. The peak potential for Au dissolution in the presence of thiourea is about 600 mV less positive than that in the presence of Br– or Cl– (1.20 V vs RHE for Br– and 1.39 V vs RHE for Cl–). The linear relationship between anodic peak currents at about 0.630 V vs RHE and square-root of the sweep rate indicates that the Au dissolution process is diffusion-controlled. The anodic current efficiency for Au dissolution is 93%. 相似文献
107.
M.A. Montero 《Electrochimica acta》2007,52(5):2083-2090
An alternative method for the determination of the kinetic parameters involved in the elementary steps of the reaction mechanism of the hydrogen electrode reaction is proposed. It is based on the determination of the variation of the polarization resistance in a tubular platinum electrode with a laminar flow of electrolyte as a function of the activity of protons of the electrolyte solution. A theoretical expression that relates the experimental variables and the equilibrium polarization resistance is developed, which takes into account the current distribution along the electrode surface. The results are compared with others obtained previously, contributing to the verification of the kinetic mechanism through a completely different experimental procedure. 相似文献
108.
109.
110.
Spherical lithium manganese oxide spinel was synthesized by an ultrasonic spray pyrolysis method, and has been characterized using X-ray diffraction, scanning electron microscopy, transimission electron microscopy and electrochemical cycling at 3 V regions. The LiMn2O4 powders were composed of about 10 nm-sized primary particles. The delivered discharge capacity of the synthesized nano-material was 125 mAh g−1 between 2.4 and 3.5 V and its retention was about 96% upon 50 cycling. From the high resolution transmission electron microscopic study, it was found that structural transition of the parent material did not occur even after the 50th electrochemical cycling on the 3 V region. It seems that the reversible structural change is possible for nanocrystalline LiMn2O4 as observed by the X-ray diffraction and transition electron microscopic observations. 相似文献