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101.
This paper proposes an empirical analytical framework for agglomeration economies based on a translog production-inverse input
demand system. Estimation of the system allows us to identify effects on total factor productivity (TFP), partial factor productivity,
factor prices and factor demands. It also provides a decomposition of the aggregate agglomeration elasticity into returns
that arise from the increased efficiency of factor inputs and a “direct” agglomeration effect which exists over and above
any factor augmentation. This enables us to indirectly address the problem of unobserved heterogeneity in factor “quality”.
The paper provides an empirical application of the model using firm level data for UK manufacturing and service industries. 相似文献
102.
Jun-Hyuk Yim Youn Geun Jung Jong Sung Lim 《Korean Journal of Chemical Engineering》2010,27(1):284-288
High-pressure vapor-liquid equilibrium data were measured for the binary mixtures of CO2+n-propanol at various isotherms (313.15–343.15 K). The vapor and liquid compositions and pressures were measured in a circulation-type
apparatus. To facilitate easy equilibration, both vapor and liquid phases were circulated separately in the experimental apparatus
and the equilibrium composition was analyzed by an on-line gas chromatograph. The experimental data were compared with literature
results and correlated with the Peng-Robinson (PR) equations of state using the Wong-Sandler mixing rules. Calculated results
with PR EOS showed good agreement with our experimental data. 相似文献
103.
Alexandre Douaud Sandra Helena Messaddeq Younès Messaddeq 《Journal of Materials Science: Materials in Electronics》2017,28(10):6989-6999
The spontaneous formation of self-assembled and/or self-organized patterns is a fundamental and technologically significant topic. This process is achieved via a phenomenon called dewetting, should it be thermally induced, or caused by laser exposure. Although dewetting seems to be a well-known phenomenon for metallic and polymeric thin films, no proper investigation regarding glassy thin films seems to have been done. Thus, in the present study we try to elaborate on the process of thermal dewetting applied to glassy thin films of the system Agx(As20S80)100?x. 相似文献
104.
Aoues Younès Pagnacco Emmanuel Lemosse Didier Khalij Leila 《Structural and Multidisciplinary Optimization》2017,55(4):1471-1482
Structural and Multidisciplinary Optimization - The reliability-based design optimization (RBDO) aims to find the most balanced design through a compromise between cost and safety when... 相似文献
105.
Chao HuByeng D. Youn 《Structural Safety》2011,33(3):218-231
Reliability analysis plays an essential role in the development of structural systems. However, commonly used reliability analysis methods suffer from either the curse of dimensionality or the lack of accuracy in many structural problems. This paper presents an asymmetric dimension-adaptive tensor-product (ADATP) method to resolve the difficulties of existing reliability analysis methods. The proposed method leverages three ideas: (i) an asymmetric dimension-adaptive scheme to efficiently build the tensor-product interpolation considering both directional and dimensional importance, (ii) a hierarchical interpolation scheme using either piecewise multi-linear basis functions or cubic Lagrange splines, (iii) a hierarchical surplus as an error indicator to automatically detect the highly nonlinear regions in a random space and adaptively refine the collocation points in these regions. The proposed method has three distinct features for reliability analysis: (a) automatically detecting and adaptively reproducing tri- and higher-variate interactions, (b) greatly alleviating the curse of dimensionality, and (c) no need of response sensitivities. Several mathematical and engineering problems involving high nonlinearity are used to demonstrate the effectiveness of the ADATP method. 相似文献
106.
Hyunseung Choo Seong-Moo Yoo Hee Yong Youn 《Parallel and Distributed Systems, IEEE Transactions on》2000,11(5):475-484
Multicomputer systems achieve high performance by utilizing a number of computing nodes. Recently, by achieving significant reductions in communication delay, the three-dimensional (3D) torus has emerged as a new candidate interconnection topology for message-passing multicomputer systems. In this paper, we propose an efficient processor allocation scheme-scan search scheme-for the 3D torus based on a first-fit approach. The scan search scheme minimizes the average allocation time for an incoming task by effectively manipulating the 3D information on a torus as 2D information using a data structure called the CST (Coverage Status Table). Comprehensive computer simulation reveals that the allocation time of the scan search scheme is always smaller than that of the earlier scheme based on a best-fit approach. The difference gets larger as the input load increases, and it is as much a factor of 3 for high load. To investigate the performance of the proposed scheme in different scheduling environments, we also consider a non-FCFS scheduling policy along with the typical FCFS policy. The allocation time complexity of the scan search scheme is O(LW2H2). This is significantly smaller than that of the existing scheme which is O(L4W4H4). Here, L, W, and H represent the length, width, and height of 3D torus, respectively 相似文献
107.
Vivek K. Bajpai Atiqur Rahman Ung Kyu Choi Sun Joo Youn Sun Chul Kang 《Food chemistry》2007,105(3):1061-1066
The aim of this work was to examine the chemical composition of the essential oil and various solvent extracts isolated from the floral cone of Metasequoia glyptostroboides Miki ex Hu and to test their efficacy against a diverse range of organisms comprising food spoilage and food-borne pathogenic bacteria. The chemical composition of essential oil isolated by hydrodistillation was analysed by GC-MS. It was determined that 59 compounds, which represented 97.06% of total oil, were present in the oil. The oil contains mainly α-pinene (29.54%), totarol (9.37%), α-thujene (8.63%), bornylene (8.63%), β-caryophyllene (4.40%), totarol acetate (3.98%), δ-3-carene (3.19%) and 2-β-pinene (2.25%). The oil was found containing mainly the oxygenated mono- and sesquiterpenes and their respective hydrocarbons. Antibacterial activity of essential oil, methanol extract and various organic sub-fractions of methanol extract of M. glyptostroboides was determined in vitro using agar diffusion method and MIC determination test against eleven (four Gram-positive, seven Gram-negative) bacterial strains including food spoilage and food-borne pathogens. The essential oil (5 μl/ml, corresponding to 1000 ppm/disc), methanol extract and various organic sub-fractions (7.5 μl/ml, corresponding to 1500 ppm/disc) of M. glyptostroboides exhibited great potential of antibacterial activity against four Gram-positive bacteria such as Bacillus subtilis (ATCC 6633), Listeria monocytogenes (ATCC 19166), Staphylococcus aureus (KCTC 1916), S. aureus (ATCC 6538) and one Gram-negative bacterium, Pseudomonas aeruginosa (KCTC 2004). The zones of inhibition of different concentrations of essential oil, methanol extract and its derived various organic sub-fractions against the tested bacteria were found in the range of 10 ∼ 20 mm and the MIC values were recorded between 125 and 1000 μg/ml. This study shows that M. glyptostroboides mediated essential oil and extracts can be applied in food industries as a natural preservatives or flavoring additives to control food spoilage and food-borne pathogenic bacteria causing severe destruction in food. 相似文献
108.
Dong Seong Oh Kwan Yuhl Cho Myong Joong Youn 《Power Electronics, IEEE Transactions on》1992,7(2):364-373
A current control technique for a voltage-fed PWM inverter is presented. The discretized state equation of an inverter and a load independent of operating conditions with the delayed input voltage feedback has been derived using the averaging concept. The discretized current controller is proposed to reduce the current error as fast as possible using the deadbeat control strategy and to stabilize the closed loop system asymptotically when the variations of load parameters are given in the predetermined stabilized region. This proposed control scheme is realized by the symmetrical uniform sampling method and is easily implemented using a microprocessor-based system. Computer simulation for the proposed controller has been carried out and the results show good static and dynamic performances 相似文献
109.
Se-Kyo Chung Hyun-Soo Kim Chang-Gyun Kim Myung-Joong Youn 《Power Electronics, IEEE Transactions on》1998,13(3):388-400
A new instantaneous torque-control strategy is presented for high-performance control of a permanent magnet (PM) synchronous motor. In order to deal with the torque pulsating problem of a PM synchronous motor in a low-speed region, new torque estimation and control techniques are proposed. The linkage flux of a PM synchronous motor is estimated using a model reference adaptive system technique, and the developed torque is instantaneously controlled by the proposed torque controller combining a variable structure control (VSC) with a space-vector pulse-width modulation (PWM). The proposed control provides the advantage of reducing the torque pulsation caused by the nonsinusoidal flux distribution. This control strategy is applied to the high-torque PM synchronous motor drive system for direct-drive applications and implemented by using a software of the digital signal processor (DSP) TMS320C30. The simulations and experiments are carried out for this system, and the results demonstrate the effectiveness of the proposed control 相似文献
110.
The adsorption and desorption of carbon monoxide and water as well as interaction between them on polycrystalline platinum
has been studied using the technique of thermal desorption spectroscopy (TDS) under ultrahigh vacuum (UHV) conditions. A small
amount of water adsorbs on the surface of the platinum at 310K and desorbs readily and steadily in the temperature range of
350-450 K. When exposure of water by more than 100 L is followed by saturation exposure of carbon monoxide, the height of
carbon monoxide desorption peak appeared at 790 K becomes higher. It suggests that preadsorbed water dissociates a small part
of carbon monoxide to atomic carbon and oxygen on the surface of the sample. And, interaction of water and carbon monoxide
(or atomic carbon) results in the water-gas shift reaction. 相似文献