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991.
992.
Condition monitoring of electric motors avoids severe economical losses resulting from unexpected motor failures and greatly improves the system reliability and maintainability. Efficiency estimation, which shares many common requirements with condition monitoring in terms of data collections, is expected to be implemented in an integrated product. This brings more considerations into the selection of the efficiency-estimation methods. This paper presents the results of an up-to-date literature survey on efficiency-estimation methods of in-service motors, particularly with considerations of the motor-condition-monitoring requirements. More than 20 of the most commonly used methods are briefly described and classified into nine categories according to their physical properties. Six categories of these methods are more related to in-service testing and are compared in a table summarizing the required tests and measurements, intrusion level, and average accuracy. Estimation of the rotor speed and the stator resistance, the two stumbling blocks of various efficiency-estimation methods, is also carefully studied; commonly used methods are summarized. Based on the survey results, four efficiency-estimation methods are suggested as candidates for nonintrusive in-service motor-efficiency estimation and condition-monitoring applications. Another contribution of this paper is that a general approach for developing nonintrusive motor-efficiency-estimation methods is proposed, incorporating rotor speed, stator resistance, and no-load loss estimations. 相似文献
993.
Polycrystal of GdPO4:RE3+ (RE=Tb, Tm) phosphors were prepared by solid-state method. Vacuum ultraviolet excitation and emission spectrum and the energy
transfer mechanism between the host and dopants of Tb3+ and Tm3+ were investigated respectively. The emission of Gd3+ at 313 nm was enhanced by the strong absorption of CTS of Tm3+ at 180 nm in GdPO4: Tm. It has also been concluded that the excitation of Gd3+ is transferred to Tb3+ and then emission peaks of 5DJ→7FJ of Tb3+ were observed. 相似文献
994.
恰希玛核电站二期工程核岛基坑降水与回灌,没有可供参考的先例。本文阐述了降水与回灌所经历的过程、改进措施以及最后取得的成果,总结了与回灌技术相关的经验教训,为类似的大型工程提供借鉴。 相似文献
995.
K.K.Y. Wong Guo-Wei Lu Lian-Kuan Chen 《Photonics Technology Letters, IEEE》2006,18(13):1442-1444
We have demonstrated, for the first time to our knowledge, simultaneous all-optical inverted and noninverted wavelength conversion by using a single-stage two-pump fiber-optical parametric amplifier with an extinction ratio between 7 and 14 dB over 24 nm. 相似文献
996.
A multi-domain (12-domain) vertical alignment liquid crystal display (MVA-LCD) device is proposed and its electro-optic characteristics evaluated through a 3-D simulator. The MVA-LCD exhibits advantages in wide viewing angle, high transmittance, fast response time, and small color shift when a pair of wide view crossed circular polarizers is employed. Potential applications of this MVA-LCD for high quality LCD TVs and computer monitors are emphasized. 相似文献
997.
The lead free Sn–Ag–y%Cu (y = 0.0, 0.5, 1.0 and 2.0) interconnect interfacial microstructures and the microstructure evolution under thermal treatment (isothermal aging, 150 °C/1000 h) were studied in detail by using surface microetching microscopy and cross section microscopy. The corresponding mechanical and reliability behaviors were evaluated by performing shear test and fracture mode analysis before and after the thermal treatment. The results indicate: (i) The interconnects could have different microstructures and intermetallic compound (IMC), depending on the Cu content. The Cu–Sn IMC could have microstructures that were clusters or protrusion-like, Augustine grass leaf-like, scissor-like, tweezers-like, etc. (ii) Ag3Sn IMCs were not observed at time zero for any interconnect groups, but they occurred after the aging for all groups. The Ag3Sn IMC could have different microstructures, again depending on Cu content. For low Cu content, the Ag3Sn IMCs were granules or nodules; for higher Cu content, Ag3Sn IMCs were plate-like. (iii) The growth of Ag3Sn plates was promoted by the growth of Cu–Sn IMCs, but indirectly linked to the Cu content. (iv) High Cu content (1.0 wt% and higher) could degrade the mechanical and reliability performances of the LF interconnect by providing a brittle joint, which was mainly achieved through the substantial growth of Cu–Sn IMCs and Ag3Sn plates. 相似文献
998.
Y. Gomeniuk A. Nazarov Ya. Vovk Yi Lu O. Buiu S. Hall J.K. Efavi M.C. Lemme 《Materials Science in Semiconductor Processing》2006,9(6):980
Metal-oxide-semiconductor capacitors based on HfO2 gate stack with different metal and metal compound gates (Al, TiN, NiSi and NiAlN) are compared to study the effect of the gate electrode material on the trap density at the insulator–semiconductor interface.C–V and G–ω measurements were made in the frequency range from 1 kHz to 1 MHz in the temperature range 180–300 K. From the maximum of the plot G/ω vs. ln(ω) the density of interface states was calculated, and from its position on the frequency axis the trap cross-section was found. Reducing temperature makes it possible to decrease leakage current through the dielectric and to investigate the states located closer to the band edge.The structures under study were shown to contain significant interface trap densities located near the valence band edge (around 2×1011 cm−2eV−1 for Al and up to (3.5–5.5)×1012 cm−2 eV−1 for other gate materials). The peak in the surface state distribution is situated at 0.18 eV above the valence band edge for Al electrode. The capture cross-section is 5.8×10−17 cm2 at 200 K for Al–HfO2–Si structure. 相似文献
999.
This paper simulates a kind of new sub-50 nm n-type double gate MOS nanotransistors by solving coupled Poisson-Schrödinger equations in a self-consistent manner with a finite element method, and presents a systematic simulation-based study on quantum-mechanical effects, gate leakage current of FinFETs. The simulation results indicate that the deviation from the classical model becomes more important as the gate oxide, gate length and Fin channel width becomes thinner and the Fin channel doping increases. Gate tunneling current density reduces with the body thickness decreasing. Excessive scaling increases the gate current below Fin thickness of 5 nm. The gate current can be dramatically reduced beyond 1017 cm−3 with the Fin body doping increasing. In order to understand the influence of electron confinement, quantum mechanical simulation results are also compared with the results from the classical approach. Our simulation results indicate that quantum mechanical simulation is essential for the realistic optimization of the FinFET structure. 相似文献
1000.