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91.
92.
Phase separation during polymerization was studied in a model system consisting of a diepoxide based on diglycidyl ether of bisphenol A (DGEBA), variable amounts of ethylenediamine (EDA) and the mass of castor oil (CO) necessary to obtain a mass fraction equal to 0-15 in a final system where the stoichiometric ratio of amine to epoxy equivalents, r, was equal to 1. A two-step polymerization process was performed by curing first a system with r = 0-5, during variable times before phase separation, and then carrying the system to r = 1. Thermodynamic analysis of samples with different r values led to a linear relationship between the Flory-Huggins interaction parameter and r. The concentration (P) and average size (D?) of dispersed-phase particles followed opposite trends, i.e. P increased while D? decreased, when either r was increased or the time of curing in the first step of a two-step process was decreased. This was explained by assuming that the competition between nucleation and growth was determined by the viscosity at the cloud point, ηcp. Low values of ηcp favoured growth over nucleation and led to fewer but larger particles. 相似文献
93.
J. W. Huang J. M. Ryan K. L. Bray T. F. Kuech 《Journal of Electronic Materials》1995,24(11):1539-1546
The defect engineering in metalorganic vapor phase epitaxy InxGa1-xAs and InP by controlled oxygen doping using diethyl aluminum ethoxide (DEALO) was developed in this study. DEALO doping has
led to the incorporation of Al and O, and the compensation of shallow Si donors in InxGa1−xAs: Si with 0 ≤ x ≤ 0.25. With the same DEALO mole fraction during growth, the incorporation of Al and O was found to be independent
of x, but the compensation of Si donors decreases with increasing In content. Deep level transient spectroscopy analysis on
a series of InxGa1-xAs: Si. samples with 0 ≤ x ≤ 0.18 revealed that oxygen incorporation led to a set of deep levels, similar to those found in
DEALO doped GaAs. As the In composition was increased, one or more of these deep levels became resonant with the conduction
band and led to a high electron concentration in oxygen doped In0.53Ga0.47As. Low temperature photoluminescence emission measurements at 12K on the same set of samples revealed the quenching of the
near-band edge peak, and the appearance of new oxygen-induced emission features. DEALO doping in InP has also led to the incorporation
of Al and O, and the compensation of Si donors due to oxygen-induced multiple deep levels. 相似文献
94.
由于器件的快速退化,101.5小时似乎成了Znse基蓝绿色半导体激光器难于逾越的寿命极限。分析退化机制,发现在强电流注入的半导体激光器中,热退化具有重要影响。研究表明,用作载流子限制层的宽带Ⅱ-Ⅵ族四元合金(如ZnMgSSe)只能对ZnSe中的电子有效地限制,无法对空穴很好地限制;而对BeTe,却只能对空穴进行有效的限制,无法对电子很好地限制。这导致ZnSe(或BeTe)活性层空穴(或电子)漏电发热,引起退化。本文提出以ZnSe/BeTe超晶格为蓝绿发光层,并用包络函数理论具体计算了阱宽、垒宽对载流子能级的不同影响,考察了ZnSe、BeTe厚度比和超晶格周期对带隙、载流子限制能力的调节。为研制新型长寿命蓝绿色半导体激光器提供了一条新的途径。 相似文献
95.
96.
The growth of nominally undoped GaSb layers by atmospheric pressure metalorganic vapor phase epitaxy on GaSb and GaAs substrates
is studied. Trimethylgallium and trimethylantimony are used as precursors for the growth at 600°C in a horizontal reactor.
The effect of carrier gas flow, V/III-ratio, and trimethylgallium partial pressure on surface morphology, electrical properties
and photoluminescence is investigated. The optimum values for the growth parameters are established. The carrier gas flow
is shown to have a significant effect on the surface morphology. The optimum growth rate is found to be 3–8 μm/ h, which is
higher than previously reported. The 2.5 μm thick GaSb layers on GaAs are p-type, having at optimized growth conditions room-temperature
hole mobility and hole concentration of 800 cm2 V−1 s−1 and 3·1016 cm-3, respectively. The homoepitaxial GaSb layer grown with the same parameters has mirror-like surface and the photoluminescence
spectrum is dominated by strong excitonic lines. 相似文献
97.
98.
99.
J. Shin Y. Hsu T. C. Hsu G. B. Stringfellow R. W. Gedridge 《Journal of Electronic Materials》1995,24(11):1563-1569
GalnSb alloys as well as the constituent binaries InSb and GaSb have been grown by organometallic vapor phase epitaxy using
the new antimony precursor trisdimethylaminoantimony (TDMASb) combined with conventional group III precursors trimethylindium
(TMIn) and trimethylgallium (TMGa). InSb layers were grown at temperatures between 275 and 425°C. The low values of V/III
ratio required to obtain good morphologies at the lowest temperatures indicate that the pyrolysis temperature is low for TDMASb.
In fact, at the lowest temperatures, the InSb growth efficiency is higher than for other antimony precursors, indicating the
TDMASb pyrolysis products assist with TMIn pyrolysis. A similar, but less pronounced trend is observed for GaSb growth at
temperatures of less than 500°C. No excess carbon contamination is observed for either the InSb or GaSb layers. Ga1-xInxSb layers with excellent morphologies with values of x between 0 and 0.5 were grown on GaSb substrates without the use of
graded layers. The growth temperature was 525°C and the values of V/III ratio, optimized for each value of x, ranged between
1.25 and 1.38. Strong photoluminescence (PL) was observed for values of x of less than 0.3, with values of halfwidth ranging
from 13 to 16 meV, somewhat smaller than previous reports for layers grown using conventional precursors without the use of
graded layers at the interface. The PL intensity was observed to decrease significantly for higher values of x. The PL peak
energies were found to track the band gap energy; thus, the luminescence is due to band edge processes. The layers were all
p-type with carrier concentrations of approximately 1017 cm3. Transmission electron diffraction studies indicate that the Ga0.5In0.5 Sb layers are ordered. Two variants of the Cu-Pt structure are observed with nearly the same diffracted intensities. This
is the first report of ordering in GalnSb alloys. 相似文献
100.
以行波半导体光放大器速度方程为基础,采用传输矩阵方法,对锥形结构半导体光放大器的增益和饱和特性进行理论研究。讨论了不同锥形长度,不同结构时的增益和饱和特性差异。理论研究表明,锥形结构能改善半导体光放大器的偏振灵敏度。在同一锥度下,长锥形长度能提高饱和增益,降低偏振度。在进行半导体光放大器有源条结构设计时要综合考虑锥度及锥形长度的影响,以实现结构优化 。 相似文献