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排序方式: 共有3153条查询结果,搜索用时 15 毫秒
981.
Nashiour Rohman Sekh Mahiuddin Narendra N. Dass Ki-Pung Yoo 《Korean Journal of Chemical Engineering》2002,19(4):679-684
We studied the effect of ion-solvent and ion-ion interactions on the isentropic compressibility of aqueous and methanolic
electrolytic solutions. In aqueous electrolytic solutions a critical concentration is attained and correlated with the completion
of the primary hydration shell. Such a situation is lacking in methanolic solutions. An expression has been derived for estimating
the hydration numbers of the electrolyte in its solutions by using the isentropic compressibility data.
This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University. 相似文献
982.
In the frame of topology optimization, the multi-objective ability has to be considered since structural design is usually required to satisfy more than one requirement. A modified topology optimization method based on the response surface method (RSM) is proposed to generate a structure of a small form factor (SFF) swing arm type actuator satisfying maximum compliance and maximum stiffness at the same time using the multi-objective optimization approach. The multi-objective function is defined to maximize the compliance in the direction of focusing as well as the eigen-frequency of the structure. The design of experiments (DOE) is performed to select sensitive variables. Based on DOE results, the response surface functions are formulated to construct the multi-objective function. The weight factors between conflicting objective functions are determined by the Pareto optimum method. By applying the optimal combination of design variables to the design domain, the optimized topology can be obtained.This work was supported by Korea Research Foundation (KRF) Grant KRF-2004-042-D00004. 相似文献
983.
It is an exceptional success when multibody dynamics researchers Multibody System Dynamics journal one of the most highly
ranked journals in the last 10 years. In the inaugural issue, Professor Schiehlen wrote an interesting article explaining
the roots and perspectives of multibody system dynamics. Professor Shabana also wrote an interesting article to review developments
in flexible multibody dynamics. The application possibilities of multibody system dynamics have grown wider and deeper, with
many application examples being introduced with multibody techniques in the past 10 years. In this paper, the development
of multibody dynamics is briefly reviewed and several applications of multibody dynamics are described according to the author’s
research results. Simulation examples are compared to physical experiments, which show reasonableness and accuracy of the
multibody formulation applied to real problems. Computer simulations using the absolute nodal coordinate formulation (ANCF)
were also compared to physical experiments; therefore, the validity of ANCF for large-displacement and large-deformation problems
was shown. Physical experiments for large deformation problems include beam, plate, chain, and strip. Other research topics
currently being carried out in the author’s laboratory are also briefly explained.
Commemorative Contribution. 相似文献
984.
Adaptive Dynamic Surface Control for Stabilization of Parametric Strict-Feedback Nonlinear Systems With Unknown Time Delays 总被引:2,自引:0,他引:2
Sung Jin Yoo Jin Bae Park Yoon Ho Choi 《Automatic Control, IEEE Transactions on》2007,52(12):2360-2365
The robust stabilization method via the dynamic surface control (DSC) is proposed for uncertain nonlinear systems with unknown time delays in parametric strict-feedback form. That is, the DSC technique is extended to state time delay nonlinear systems with linear parametric uncertainties. The proposed control system can overcome not only the problem of ldquoexplosion of complexityrdquo inherent in the backstepping design method but also the uncertainties of the unknown time delays by choosing appropriate Lyapunov-Krasovskii functionals. In addition, we prove that all the signals in the closed-loop system are semiglobally uniformly bounded. Finally, an example is provided to illustrate the effectiveness of the proposed control system. 相似文献
985.
Jinsu Yoo 《Thin solid films》2007,515(12):5000-5003
Hydrogenated films of silicon nitride (SiNx:H) were investigated by varying the deposition condition in plasma enhanced chemical vapor deposition (PECVD) reactor and annealing condition in infrared (IR) heated belt furnace to find the optimized condition for the application in multicrystalline silicon solar cells. By varying the gas ratio (ammonia to silane), the silicon nitride films of refractive indices 1.85-2.45 were obtained. Despite the poor deposition rate, silicon wafer with the film deposited at 450 °C showed the best minority carrier lifetime. The film deposited with the gases ratio of 0.57 showed the best peak of carrier lifetime at the annealing temperature of 800 °C. The performance parameters of cells fabricated by varying co-firing peak temperature also showed the best values at 800 °C. The multicrystalline silicon (mc-Si) solar cells fabricated in conventional industrial production line applying the optimized film deposition and annealing conditions on large area substrate (125 mm × 125 mm) was found to have the conversion efficiency of 15%. 相似文献
986.
987.
We fabricated a single-electron transistor using DNA-assisted assembly of Au nanoparticles. Most devices exhibited clear Coulomb blockade and oscillations. In contrast to conventional single-electron transistors, however, the period of Coulomb oscillations was observed to depend on the temperature. This temperature dependence is probably ascribed to the temperature dependence of gate capacitance. 相似文献
988.
Sungdeok Cha Hanseong Son Junbeom Yoo Eunkyung Jee Poong Hyun Seong 《Reliability Engineering & System Safety》2003,82(1):11-20
Fault tree analysis, the most widely used safety analysis technique in industry, is often applied manually. Although techniques such as cutset analysis or probabilistic analysis can be applied on the fault tree to derive further insights, they are inadequate in locating flaws when failure modes in fault tree nodes are incorrectly identified or when causal relationships among failure modes are inaccurately specified. In this paper, we demonstrate that model checking technique is a powerful tool that can formally validate the accuracy of fault trees. We used a real-time model checker UPPAAL because the system we used as the case study, nuclear power emergency shutdown software named Wolsong SDS2, has real-time requirements. By translating functional requirements written in SCR-style tabular notation into timed automata, two types of properties were verified: (1) if failure mode described in a fault tree node is consistent with the system's behavioral model; and (2) whether or not a fault tree node has been accurately decomposed. A group of domain engineers with detailed technical knowledge of Wolsong SDS2 and safety analysis techniques developed fault tree used in the case study. However, model checking technique detected subtle ambiguities present in the fault tree. 相似文献
989.
Sung-Il Kim Byung-Chul Ko Ho-In Lee Yeon-Chul Yoo 《Metals and Materials International》2003,9(5):447-451
The high-temperature deformation behavior and dynamic softening transition from dynamic recrystallization (DRX) to dynamic
recovery (DRV) of Al-18 wt.%Si alloy was studied by torsion tests in a temperature range of 573∼773 K and a strain rate range
of 0.001∼1/sec. The alloy was produced by spray-forming followed by hot extrusion. The dependence of flow stress (σ) on strain
rate and temperature (T) could be described by the power Arrhenius relationship,. The activation energy and stress exponent values were higher at the low temperature region than those at the high temperature
region. The alloy showed a flow curve of DRX in the temperature range of 573∼673 K, while at 673∼773 K, the alloy exhibited
a flow curve of DRV. These results were analyzed by observing the shapes of the flow curves throughout the deformation condition.
Also, the transition behavior from DRX to DRV has been investigated through observation of deformed microstructure and flow
curves during hot deformation. 相似文献
990.
Jeong Wahn Yoo Brian Moran Jiun‐Shyan Chen 《International journal for numerical methods in engineering》2004,60(5):861-890
A stabilized conforming nodal integration scheme is implemented in the natural neighbour method in conjunction with non‐Sibsonian interpolation. In this approach, both the shape functions and the integration scheme are defined through use of first‐order Voronoi diagrams. The method illustrates improved performance and significant advantages over previous natural neighbour formulations. The method also shows substantial promise for problems with large deformations and for the computation of higher‐order gradients. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献