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31.
NiCuZn铁氧体和银内电极的共烧行为 总被引:2,自引:0,他引:2
NiCuZn铁氧体正作为磁介质广泛地应用于低烧多层片式电感,因此有必要对其与银内电极的共烧行为进行研究。该文主要介绍NiCuZn铁氧体/银内电极多层复合体共烧过程中的烧结收缩、界面反应、扩散对介质性能的影响。尖晶石结构中存在相当数量的空位,这为银离子提供了一定的溶解度,因此在共烧过程中银对铁氧体的相组成影响较小。银对铁氧体性能的影响体现在两个方面。一方面是由于银具有相对低的烧结温度,从而在烧结过程中起到助烧剂的作用,促进致密化过程,提高烧结体的密度和磁导率;另一方面,银促使铁氧体中的铜在晶界处析出,导致晶界处应力,使磁导率降低,晶粒生长也被一定程度地抑制。 相似文献
32.
38MnSiVS5 steel is similar to 38MnVS6 steel (EN), the difference being the addition of a small Ti content. Typical Ti and Al contents in the chemical composition of 38MnSiVS5 steel are Ti=0.020 and Al=0.035 mass%. Both elements combine easily with nitrogen, especially Ti, and it has been observed that relatively high Al levels are harmful for austenite grain size control at reheating temperatures. In this work 38MnSiVS5 steel is used to manufacture a large number of castings, varying only the Ti and Al contents and obtaining ingots with a different Ti/Al ratio in each case. The results show that abnormal growth of the austenitic grain occurs irrespective of the Ti and Al contents, due fundamentally to the partial dissolution and coarsening of TiN precipitates. However, the steels with high Al contents present worse behaviour due to the formation of a second type of precipitates, namely AIN, which quickly dissolve between 1000 and 1100°C, causing a drastic decline in local pinning forces that gives rise to more pronounced abnormal growth of the affected grains. 相似文献
33.
34.
低价硫化铝法从氧化铝直接炭还原制铝的动力学研究 总被引:3,自引:0,他引:3
低价硫化铝法从氧化铝直接炭还原制铝的动力学过程极为复杂,过程的前期受界面化学反应控制,过程后期受扩散过程控制,并求得不同时期的活化能,反应前期:E1=63.81 kJ/mol(6.67 Pa)、E2=50.82 kJ/mol(66.7 Pa)、E3=54.72 kJ/mol(666.7 Pa)、E4=39.61 kJ/mol(1333 Pa);反应后期:E*1=112.90 kJ/mol(6.67 Pa)、E*2=89.92 kJ/mol(66.7 Pa)、E*3=97.32 kJ/mol(666.7 Pa)、E*4=51.83 kJ/mol(1333 Pa).从动力学的角度提出了反应的较佳条件.温度、真空度的提高一方面可增大反应速率,但另一方面却加大了硫化铝的挥发,仅从增大速率而言,温度应大于1100 ℃,真空度应优于1333 Pa为宜. 相似文献
35.
A thin film of poly(l-serine) was prepared via electropolymerization for the determination of trace levels of estradiol. In pH 5.0 phosphate buffer,
l-serine was oxidized during the cyclic potential sweeps between −0.60 and 2.0 V, forming a thin film at the electrode surface.
The electrochemical behavior of estradiol was investigated. The oxidation peak potential of estradiol shifts negatively at
the poly(l-serine) film-coated glassy carbon electrode (GCE) compared with that at the bare GCE. Otherwise, the oxidation peak current
greatly increases at the poly(l-serine) film-modified GCE. These phenomena suggest that the poly(l-serine) film exhibits catalytic activity towards the electrochemical oxidation of estradiol. Based on this, a sensitive,
rapid and simple electrochemical method was proposed for the determination of estradiol. The limit of detection is evaluated
to be 2.0 × 10−8 mol L−1. Finally, this method was successfully used to determine estradiol in blood serum. 相似文献
36.
Ahmad Nozad Golikand Elaheh Lohrasbi Mohammad Ghannadi Maragheh Mehdi Asgari 《Journal of Applied Electrochemistry》2008,38(6):869-874
The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by
cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms,
polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface
area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The
formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of
a gas diffusion electrode for oxygen reduction reaction. 相似文献
37.
A simple method has been devised for immobilization of acetylcholinesterase (AChE) covalent bonding to a multiwall carbon
nanotube (MWNT)-cross-linked cellulose acetate composite on a screen-printed carbon electrode (SPCE) and a sensitive and disposable
amperometric sensor for rapid determination of carbaryl pesticide is proposed. The immobilized enzyme was preserved on this
film because of the excellent biocompatibility and non-toxicity of cellulose acetate. Based on the inherent conductive properties
of the MWNT, the immobilized AChE had greater affinity for ATCl and excellent catalytic effect in the hydrolysis of ATCl.
MWNT improved the interface enzymatic hydrolysis reaction and increased the amperometric response of the sensor. Under optimum
conditions, the inhibition of carbaryl on AChE increased linearly with the increasing concentration of carbaryl in two ranges,
from 0.01 to 0.5 μg mL−1 and from 2 to 20 μg mL−1, with the correlation coefficients of 0.9985 and 0.9977, respectively. The detection limit was 0.004 μg mL−1 taken as the concentration equivalent to 10% decrease in signal. The sensor showed acceptable stability, accuracy and could
be fabricated in batches, thus it is economic and portable. This type of disposable enzyme-based amperometric sensor has extensive
application potential in environmental monitoring of pesticides. 相似文献
38.
Debasmita Das Purabi Rani Samaddar Pratik Kumar Sen Kaushik Das 《Journal of Applied Electrochemistry》2008,38(6):743-749
Galvanostatic steady state current potential measurements were carried out for oxidation of a series of aliphatic alcohols
having varying number of hydroxyl groups. The anodically deposited layer of MnO2 on platinum was used as the electrode material. The deposit was characterised by scanning electron microscopy (SEM), energy
dispersive X-ray analysis (EDAX) and electrode potential measurements. The catalytic role of MnO2 in the electro-oxidation of alcohols was indicated by the chronopotentiograms and the cyclic voltammograms. An analysis of
the electrochemical data indicated a catalytic EC mechanism in which Mn (V) is generated electrochemically and consumed chemically
in succession. Based on this and the hydrogen bonding interaction between alcoholic hydroxyl groups and MnO2 layer, a mechanism was proposed which accounts for the variation in the observed electrochemical reaction orders. Tafel behaviour
was found to be followed only approximately. Current efficiency of the electrochemical oxidation of polyols was studied. Replacement
of platinum by carbon as current collector was found to leave the electrocatalytic activity of the MnO2 deposit practically unaltered. 相似文献
39.
Teresa Łuczak 《Journal of Applied Electrochemistry》2008,38(4):469-476
The electrooxidation of phenylethanolamine (2-amino-1-phenylethanol) at a gold electrode in alkaline electrolyte has been
studied. Measurement of the differential capacitance of the electric double layer versus the electrode potential has shown
that the adsorption of phenylethanolamine at the gold-solution interface plays a significant role in the oxidation mechanism.
The effect of amine concentration, electrolyte pH and potential scan rate on the electrooxidation is analysed. 相似文献
40.
Hamdy F. M. Mohamed 《应用聚合物科学杂志》2008,108(2):1307-1313
Coincidence Doppler broadening of annihilation radiation (CDBAR) and Vickers hardness techniques were performed to study pure Al2O3, pure polyvinyl chloride (PVC), and doped PVC with different concentrations of Al2O3 (10–50%). The CDBAR ratio curves with respect to pure PVC were presented and reflect the momentum distribution of all the samples. The peak around 14.5 ×10?3 moC in the CDBAR ratio curves suggests a large contribution of positron annihilation with the Al2O3. There is a linear correlation between the height of this peak and the Al2O3 concentration. The S‐ and W‐parameters were extracted from the CDBAR spectra and increase with increasing the Al2O3 concentration showing discontinuity at 30% of Al2O3 concentration on PVC. The present data confirmed that there is no positronium formation in pure Al2O3 as a result of smaller S‐parameter. The Vickers hardness increases with increasing the Al2O3 concentration in PVC showing a linear dependence with two different slopes depend on the Al2O3 concentration range. A correlation between the Vickers hardness (macroscopic data) and the W‐parameter (microscopic data) was observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献