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981.
Chi-Yen Lin You-Ming Chen Hsiao-Fan Chen Fu-Chuan Fang Yu-Cheng Lin Wen-Yi Hung Ken-Tsung Wong Raymond C. Kwong Sean C. Xia 《Organic Electronics》2009,10(1):181-188
This paper describes the synthesis of three triaryldiamine derivatives presenting two thermally polymerizable trifluorovinyl ether groups that can be polymerized through thermal curing to form perfluorocyclobutyl (PFCB) polymers. These PFCB polymers, studied using time-of-flight techniques for the first time, exhibited remarkable non-dispersive hole-transport properties, with values of μh of ca. 10?4 cm2 V?1 s?1. When we employed these thermally polymerized polymers as hole-transport layers (HTLs) in electroluminescence devices containing tris(8-hydroxyquinolate) aluminum (Alq3) as the emission layer, we obtained high current densities (ca. 3400 mA cm?2), impressive brightnesses (5 × 104 cd m?2), and high external quantum efficiencies (EQEs = 1.43%). These devices exhibited the same turn-on voltage, but higher EQEs, relative to those incorporating the vacuum-processed model compound N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine (α-NPD) (EQE = 1.37%) as the HTL under the same device structure. 相似文献
982.
Multiwall carbon nanotube reinforced poly (phenylene sulfide) (PPS) nanocomposites were successfully fabricated through melt compounding. Structural, electrical, thermal, rheological, and mechanical properties of the nanocomposites were systematically studied as a function of carbon nanotube (CNT) fraction. Electrical conductivity of the polymer was dramatically enhanced at low loading level of the nanotubes; the electrical percolation threshold lay between 1 and 2 wt % of the CNTs. Rheological properties of the PPS nanocomposites also showed a sudden change with the CNT fraction; the percolation threshold was in the range of 0–0.5 wt % of CNTs. The difference in electrical and rheological percolation threshold was mainly due to the different requirements needed in the carbon nanotube network in different stages. The crystallization and melting behavior of CNT‐filled PPS nanocomposites were studied with differential scanning calorimetry; no new crystalline form of PPS was observed in the nanocomposites, but the crystallization rate was reduced. The thermal and mechanical properties of the nanocomposites were also investigated, and both of them showed significant increase with CNT fraction. For 5 wt % of CNT‐filled PPS composite, the onset of degradation temperature increased by about 13.5°C, the modulus increased by about 33%, and tensile strength increased by about 172%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
983.
Dunmin Lin Kin Wing Kwok Helen Wong Lai-wa Chan 《Journal of the American Ceramic Society》2009,92(6):1362-1365
In this work, the double-loop-like characteristics of K0.5 Na0.5 NbO3 + x mol% K5.4 Cu1.3 Ta10 O9 ceramic and its relationships with the transition temperature, aging, and switching have been investigated. Our results reveal that the phase transition temperature is an important parameter determining the aging requirement for the ceramics to exhibit the double-loop-like characteristics. For a ceramic with a high transition temperature, e.g. the ceramic with x =0.75 (tetragonal–orthorhombic phase temperature ∼206°C), the vacancies can migrate during the crystal transformation and settle in a distribution with the same symmetry as the crystal after the transformation. As a result, defect dipoles along the polarization direction are formed and provide restoring forces to reverse the switched polarizations, and thus producing a double polarization hysteresis ( P – E ) loop. On the other hand, aging is required for a ceramic with a low transition temperature, e.g. aging at 80°C for 30 days is required for the ceramic with x =1.5 (transition temperature ∼175°C). Our results also reveal that the defect dipoles can be switched under a slow-switching electric field (<1 Hz) or at high temperatures (>100°C), thus leading to an opening of the double P – E loop. 相似文献
984.
Terry C. Chilcott Elicia L.S. Wong Hans G.L. Coster Michael James 《Electrochimica acta》2009,54(14):3766-6808
Electrical impedance spectroscopy characterisations of gold surfaces formed on mica templates in contact with potassium chloride electrolytes were performed at the electric potential of zero charge over a frequency range of 6 × 10−3 to 100 × 103 Hz. They revealed constant-phase-angle (CPA) behaviour with a frequency exponent value of 0.96 for surfaces that were also characterised as atomically flat using atomic force microscopy (AFM). As the frequency exponent value was only marginally less than unity, the CPA behaviour yielded a realistic estimate for the capacitance of the ionic double layer. The retention of the CPA behaviour was attributed to specific adsorption of chloride ions which was detected as an adsorption conductance element in parallel with the CPA impedance element. Significant variations in the ionic double layer capacitance as well as the adsorption conductance were observed for electrolyte concentrations ranging from 33 μM to 100 mM, but neither of these variations correlated with concentration. This is consistent with the electrical properties of the interface deriving principally from the inner or Stern region of the double layer. 相似文献
985.
Electrochemical intercalation studies are used to characterize a series of ionic liquids composed of a variety of cationic and anionic species. Electrochemically, the ionic liquids are characterized by cyclic voltammograms and charge–discharge experiments for the intercalation and de-intercalation of the various cationic and anionic species into graphite. X-ray structure analysis is also performed to determine the relationship between the electrochemical behaviour of the ionic liquids, and the formation of intercalated graphitic compounds. Two different types of imidazolium cations are studied, specifically the di- and trisubstituted imidazolium. These cations are paired with the following anions: tetrafluoroborate, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, bis(perfluoroethanesulfonyl)imide, nitrate and hydrogen sulfate. Results indicate stronger intercalation chemistry for the trisubstituted imidazoliums, correlating with the greater charge–discharge efficiencies found for these types of ionic liquids. Many of the anions exhibit very poor charge–discharge efficiencies, correlating to very poorly formed graphite intercalates. The exception to this is the hydrogen sulfate intercalate, which had low charge–discharge efficiencies but formed a well defined graphite intercalate. Only the imide based anions exhibited both high charge–discharge efficiencies and the formation of a clearly defined graphite intercalate. 相似文献
986.
The indoor environmental quality (IEQ) in residential buildings is examined from the prospect of an occupant's acceptance in four aspects: thermal comfort, indoor air quality, noise level and illumination level. Based on the evaluations by 125 occupants living in 32 typical residential apartments in Hong Kong, this study proposes empirical expressions to approximate the overall IEQ acceptance with respect to four contributors, namely operative temperature, carbon dioxide concentration, equivalent noise level and illumination level, via a multivariate logistic regression model. A range of IEQ acceptances for regular residential conditions is determined and the dependence of the predicted overall IEQ acceptance on the variations of the contributors is discussed. The proposed overall IEQ acceptance can be used as a quantitative assessment criterion for similar residential environments where an occupant's evaluation is expected. 相似文献
987.
988.
The behaviour of composite cellular floor beams is becoming important as such members are increasingly used in multistorey
buildings. In the event of fire, this issue becomes increasingly critical, particularly for exposed steelwork. In a fire situation,
a composite beam has a much higher perimeter area exposed to fire in its lower web-flange section than in the upper web-flange
section, and so the temperature distribution across a composite beam is usually non-uniform. The reduction in fire of the
strength and stiffness of the material properties of the perforated steel beam, as well as differential thermal expansion,
therefore becomes an important influence on the overall behaviour of the composite beam. The objective of this research is
to enhance the level of understanding of the generic behaviour of composite cellular floor beams in fire conditions. In this
paper, three-dimensional nonlinear finite element models of composite cellular floor beams have been developed, taking into
consideration the influence of the changes in material properties with temperature. Experimental data from furnace tests on
cellular composite floor beams obtained from previous research work has been used to validate the FE models. An analytical
model based on existing design guides is also presented in this paper. It is concluded that finite element analysis results
are in good agreement with the experimental data, and all the failure modes have been accurately predicted. The proposed simplified
analytical methods show reasonable agreement with the test and FE results, and are always conservative. 相似文献
989.
The charge-transfer properties of DNA duplexes are exploited to produce a fast, simple, sensitive, and selective DNA biosensor by exposing the DNA recognition interface to a sample containing target DNA and the redox-active intercalator, anthraquinonemonosulfonic acid (AQMS). Electrochemistry from electron transfer through the DNA to AQMS intercalated into DNA duplexes can be differentiated from electrochemistry due to direct access of the AQMS to the electrode surface due to the difference in the environment of the AQMS giving a shift in the potential at which the molecule is reduced. The ability to distinguish between the two electrochemical signals enables DNA hybridization to be monitored in real time. This in situ detection scheme has good selectivity, being able to differentiate between a complementary target DNA sequence and one containing either C-A or G-A single-base mismatches. The concentration detection limit of the biosensor is 0.5 nM (1 pmol) with an assay time of 1 h. The fact that the end user is only required to simultaneously add the sample containing the target DNA and AQMS gives a DNA biosensor that is highly compatible with PCR on chip technologies. 相似文献
990.
Chun-Yen Chang Jiong-Guang Su Shyh-Chyi Wong Tiao-Yuan Huang Yuan-Chen Sun 《Microelectronics Reliability》2002,42(4-5)
This paper presents a high performance RF CMOS technology with a complete portfolio of RF and base band components for single-chip systems. Using an optimized 0.13 μm CMOS topology, fT of 86 GHz and fmax of 73 GHz are obtained, in addition to a NFmin of 1.5 dB without ground-shielded signal pad. The high-Q accumulation-mode and diode varactors are optimized to perform a high tuning range of 47% and 25%, respectively. Inductors with a quality factor of 18 at 1.7 nH are obtained using copper interconnect, while capacitors with high unit capacitance and quality factor are fabricated with metal-insulator-metal structures. Finally, a deep n-well isolation is adopted to suppress the interblock coupling noise penetrating through substrate by 40 and 25 dB at 0.1 and 2.4 GHz, respectively. These results clearly demonstrate that CMOS technology can provide a complete solution for single-chip wireless systems. 相似文献