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191.
Hyuk Jae Kwon Youngjin Kim In-Sik Nam Seong Moon Jung Ju-Hyung Lee 《Topics in Catalysis》2010,53(7-10):439-446
A paper-like ceramic fiber was employed as a monolith substrate for removing NO by NH3. The stronger hydrothermal stability of the ceramic fiber washcoated with V2O5/TiO2 was observed by the pre-calcination of the substrate, mainly due to the well dispersed AlPO4 formed on the substrate surface improving the washcoating of the catalysts and moderating the phase transformation of TiO2 from anatase to rutile. 相似文献
192.
193.
G. Fernandez J. Moon 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2010,25(5):560-566
Field observations indicate that current engineering practice does not consistently estimate ground water flows into unlined rock excavated tunnels due to various factors that analytical solutions do not take into account. These factors include significant geological features, groundwater drawdown, inadequate estimates of hydraulic conductivity from packer tests, and stress-induced rock-mass permeability reduction in the vicinity of tunnel (lining-like zone). A key variable that is not properly accommodated in current practice, is the hydro-mechanical interaction within the joints in the surrounding rock mass. The significance of this variable is discussed in the 1st part of the paper which presents an analytical solution assessing ground water inflow rate into a tunnel using a mathematical derivation that takes into account the excavation-induced rock permeability reduction in the vicinity of a tunnel based on hydro-mechanical coupling effect. In the 2nd part of the paper, results from numerical analysis are presented to verify the proposed analytical solution for estimating ground water inflow rate into a tunnel. Further studies are currently underway to identify other key variables and their impact on the behavior of unlined tunnels and hydrological flow regime in the surrounding fractured rock mass using a distinct element method program which can fully consider hydro-mechanical coupled behavior of joints. 相似文献
194.
Gyo-Ho Lee Sang-Hyun Moon Min-Cheol Kim Si-Jin Kim Sojeong Choi Eun-Soo Kim Sang-Beom Han Kyung-Won Park 《Ceramics International》2018,44(7):7972-7977
The fabrication process and material design of flexible lithium-ion batteries (LIBs) are essential in flexible portable devices. In particular, the carbon nanofiber (CNF)-based active anodes with flexibility synthesized using an electrospinning technique showed fairly stable cycling performance in the LIBs. In this study, we synthesized the molybdenum carbide (MoC) embedded in CNFs as an anode for LIBs (MoC/CNF) using an electrospinning technique with amorphous Mo precursor and polyacrylonitrile as the molybdenum and carbon sources, respectively, and using a heating process under an N2 atmosphere. The as-prepared flexible MoC/CNF showed a 3D porous structure consisting of crystalline MoC and amorphous CNF. MoC/CNF, directly utilized as an active electrode without binder, conductor, or current collector, exhibited superior LIB performance, i.e. high capacity, cyclability, and high-rate properties. In particular, at a considerably high charge/discharge rate of 10?A?g?1, the specific capacity of MoC/CNF (109?mAh?g?1) was significantly higher than that of pure CNF electrode (3?mAh?g?1). 相似文献
195.
Three-dimensional locomotion control of single-legged robot: Resonance hopping and running direction
Tae Hun Kang Jeon Il Moon 《International Journal of Control, Automation and Systems》2016,14(5):1331-1339
This study proposes a locomotion controller for a single-legged robot. The locomotion controller comprises five parts: virtual spring, height control, forward velocity control, body attitude control, and angular momentum control. First, we propose an effective method called a virtual spring to generate a springy force using a linear actuator. Two virtual springs are adopted to compute the energy exchange and to compensate the energy loss during hopping. A simple and intuitive method is proposed to implement resonance oscillation in terms of energy loss. A height controller is proposed based on the resonance oscillation using a virtual spring. In addition, a running direction controller, which has never been resolved in previous studies, is proposed. This novel controller can remove the unexpected angular momentum about the yaw direction during running. All of the proposed algorithms and methods are validated through dynamic simulations. 相似文献
196.
Young-Su Kwon Jeong-Hum Lee Sang-Ho Moon Byung-Ki Kwon Chang-Ho Choi Jul-Ki Seok 《Industry Applications, IEEE Transactions on》2009,45(5):1610-1618
We propose a current injection-based estimator to identify accurately standstill induction motor (IM) parameters necessary for vector control. A mathematical model that faithfully represents the general deep bar effect is introduced. Then, two exciting signals with a different frequency are sequentially injected to track the parameters based on the frequency function of the rotor bar. The proposed methodology employs closed-loop control of an injected current due to little knowledge of the unknown motor, rather than the open-loop voltage injection approaches commonly used in sensorless control schemes. Subsequently, this control scheme proactively prevents electrical accidents resulting from inadequate open-loop voltage injection. Our developed specialized offline commissioning test compensates for the phase delay resulting from the drive, which significantly affects estimation precision. The effectiveness of the identification technique is validated by means of experiments performed on three different IMs. 相似文献
197.
198.
Quasi-isotropic bending responses of metallic sandwich plates with bi-directionally corrugated cores
In order to reduce anisotropic behaviors of sandwich plates with open channel cores under the bending load, bi-directionally corrugated cores were introduced. Bi-directionally corrugated core has two additional design parameters related with a corrugation pass than uni-directionally corrugated core, so that its properties with respect to core orientations can be controlled. Sandwich plate with bi-directionally corrugated core is designed optimally so that beam buckling of face sheets is reduced drastically and anisotropic buckling behavior in the face sheets is minimized. The cores fabricated by a sectional forming process were bonded with face sheets by adhesive bonding. Three-point bending experiments were carried out with respect to core orientations. It has been shown from the experiments that sandwich plates with bi-directionally corrugated cores exhibit quasi-isotopic bending behaviors and structural performances in sandwich plates. 相似文献
199.
In Chul Lee Young Su Kang Hee Jang Moon Seok Pil Jang Jin Kon Kim Jaye Koo 《Journal of Mechanical Science and Technology》2010,24(7):1425-1431
Modulated liquid jets injected into subsonic cross-flows are empirically studied by using a mechanical liquid jet modulation
apparatus. Experimental investigations were conducted using water over a range of cross-flow velocities from 5 m/s to 143
m/s and with modulated liquid jet frequencies from 35.7 Hz to 166.2 Hz and so on. PDPA(phase Doppler particle anemometry)
was employed to measure droplet diameter and velocity with various spray cross-sections from Z/d=20 to Z/d=60. The spray structure,
penetration depth, SMD(Sauter mean diameter), volume flux and velocity characteristics of modulated liquid jets injected into
cross-flows were examined. As oscillation of the periodic pressure that could make liquid jet moved up and down in cross-flow
field, the mixing process was facilitated. This phenomenon has the advantage of mixing the spray concentration from the center
area to the outer area. Also, a bulk liquid jet puff was detected in the upper field of the liquid jet surface. The modulation
effect appears significant in the extent of the spray oscillation. The correlation equations for the liquid jet boundary of
the upper and lower regions which related to the Strouhal number have been presented to predict the spray structure under
modulation conditions. Because of the modulation frequency, an inclination of averaged SMD for the structured layer was evanescent
which contributed to the promotion of the macroscopic spray mixing process. Cross-sectional characteristics of SMD had the
same tendency over a range of various modulation frequencies. As the modulation frequency increased, the region of volume
flux distribution also increased. 相似文献
200.
Kee Do Woo Jae Hwang Kim Eui Pyo Kwon Min Seok Moon Hyun Bom Lee Tatsuo Sato Zhiguang Liu 《Metals and Materials International》2010,16(2):213-218
To fabricate an Al-V matrix composite reinforced with submicron-sized Al2O3 and AlxVy (Al3V, Al10V) phases, high energy mechanical milling (HEMM) and sintering were employed. By increasing the milling time, the size of
mechanically milled powder was significantly reduced. In this study, the average powder size of 59 μm for Al, and 178 μm for
V2O5 decreased with the formation of a new product, Al-Al2O3-AlxVy, with a size range from 1.3 μm to 2.6 μm formed by the in-situ combustion reaction during sintering of HEM milled Al and
V2O5 composite powders. The in-situ reaction between Al and V2O5 during the HEMM and sintering transformed the Al2O3 and AlxVy (Al3V, Al10V) phases. Most of the reduced V reacted with excess the Al to form AlxVy (Al3V, Al10V) with very little V dissolved into Al matrix. By increasing the milling time and weight percentage of V2O5, the hardness of the Al-Al2O3-AlxVy composite sintered at 1173 K increased. The composite fabricated with the HEMM Al-20wt.%V2O5 composite powder and sintering at 1173 K for 2 h had the highest hardness. 相似文献