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排序方式: 共有851条查询结果,搜索用时 15 毫秒
31.
32.
I. V. Kityk S. Soltan N. S. AlZayed R. Viennois C. Reibel M. Shahabuddin A. M. El-Naggar Salem A. S. Qaid M. S. Shah 《Journal of Materials Science: Materials in Electronics》2013,24(11):4585-4589
The occurrence of the optical second harmonic generation (SHG) at fundamental wavelength of Er:glass nanosecond 1,540 nm stimulated by two coherent CO2 microsecond laser beams at wavelengths 10.6 and 5.3 μm was observed for the MgB2 films. The SHG signal has shown its sensitivity to the occurrence of the superconducting (SC) phase transition. The SHG achieves its maximum at temperatures higher with respect to the SC transition. The effect is reversible with respect to the photo induced treatment. After the switching off of the external photoinducing treatment the effect almost disappears. However, this still strongly affects the SC properties of the MgB2 thin layers, as the critical current is increased by 50 % after illumination. 相似文献
33.
AA2124 nanopowders <100 nm in particle size and 20 nm internal structure produced by high energy ball milling of gas-atomized
micronpowders ~45 μm in particle size and 700 nm internal structure were processed in to bulk rods. The micro- and nanopowders
were hot compacted using uniaxial pressing for preliminary densification at 0.7T
m of the alloy. Selected intact hot compacts (HCs) were promoted for warm severe plastic deformation via equal channel angular
pressing (ECAP) at the minimum possible deforming temperature for final densification. Effect of the fabrication method of
the consolidated powders was investigated. A combined processing via HC/ECAP produced bulk nanostructured rods 2.5 μm and
50-60 nm in grain size for the micro- and nanopowder consolidates, respectively. The powder properties controlled the degree
of densification and mechanical behavior during the hot compaction stage, which influenced strongly the deformation behavior
during subsequent ECAP. At the end of HC/ECAP one pass, the HC stage was responsible for about 83 and 95% of the total grain
coarsening encountered for the micro- and nanopowder HCs, respectively. Throughout the various consolidation stages employed,
the ball-milled (BM) nanopowder consolidates exhibited 2/3 the grain growth and displayed almost twice the hardness and compressive
strength values of the gas-atomized micronpowder ones. Influence of BM and HC on the Al2O3 layer formed around the individual powder particles was also investigated. 相似文献
34.
SPARCL: an effective and efficient algorithm for mining arbitrary shape-based clusters 总被引:3,自引:3,他引:0
Vineet Chaoji Mohammad Al Hasan Saeed Salem Mohammed J. Zaki 《Knowledge and Information Systems》2009,21(2):201-229
Clustering is one of the fundamental data mining tasks. Many different clustering paradigms have been developed over the years,
which include partitional, hierarchical, mixture model based, density-based, spectral, subspace, and so on. The focus of this
paper is on full-dimensional, arbitrary shaped clusters. Existing methods for this problem suffer either in terms of the memory
or time complexity (quadratic or even cubic). This shortcoming has restricted these algorithms to datasets of moderate sizes.
In this paper we propose SPARCL, a simple and scalable algorithm for finding clusters with arbitrary shapes and sizes, and
it has linear space and time complexity. SPARCL consists of two stages—the first stage runs a carefully initialized version
of the Kmeans algorithm to generate many small seed clusters. The second stage iteratively merges the generated clusters to
obtain the final shape-based clusters. Experiments were conducted on a variety of datasets to highlight the effectiveness,
efficiency, and scalability of our approach. On the large datasets SPARCL is an order of magnitude faster than the best existing
approaches. 相似文献
35.
36.
In the present work, the suitability of printing natural fabrics (wool, silk, cotton and flax) with two natural dyes (alkanet and rhubarb) using pigment-printing technique has been investigated. The effect of different factors, i.e. dye concentration, nature of thickening agent, type of fixation, concentration and type of mordant, has been studied. The printed goods were evaluated by measuring the K/S value and the overall fastness properties. Results show that the highest K/S value was obtained by using Meypro gum as a thickener. The K/S increases rapidly as the concentration of the natural dye powder in the printing paste increases from 10 to 40 g/kg printing paste. Moreover, results show that the printed goods, which were fixed via steaming, have relatively higher colour strength than their corresponding samples fixed via thermofixation. The effect of mordants on colour development was also studied and alkanet dye was chosen as an example for this investigation. The best results were obtained by using mordant at a concentration of 20 g/kg printing paste. Different colour yields could be obtained by using different mordants, and all of colour fastness results were ranging between very well and excellent. 相似文献
37.
Javed Syed Rahmath Ulla Baig Salem Algarni Y.V.V. Satyanarayana Murthy Mohammad Masood Mohammed Inamurrahman 《International Journal of Hydrogen Energy》2017,42(21):14750-14774
The rapid growth of vehicular pollution; mostly running on the diesel engine, emissions emerging are the concerns of the day. Owing to clean burn characteristics features, Hydrogen (H2) as a fuel is the paradigm of the researcher. Extensive research presented in the literature on H2 dual fueled diesel engine reveals, the significant role of H2 in reducing emissions and enhancing the performance of a dual fueled diesel engine. With meager qualitative experiment data, the feasibility to develop an efficient Artificial Neural Network (ANN) model is investigated, the developed model can be utilized as a tool to investigate the H2 dual fueled diesel engine further. In the process of developing an ANN model, engine load and H2 flow rate are varied to register performance and emission characteristics. The creditability of the experiment is ascertained with uncertainty analysis of measurable and computed parameters. Leave-out-one method is adopted with 16 data sets; seven training algorithms are explored with eight transfer function combinations to evolve a competent ANN model. The efficacy of the developed model is adjudged with standard benchmark statistic indices. ANN model trained with Broyden, Fletcher, Goldfarb, & Shanno (BFGS) quasi-Newton backpropagation (trainbfg) stand out the best among other algorithms with regression coefficient ranging between 0.9869 and 0.9996. 相似文献
38.
This paper presents economic efficiency evaluation of electricity markets operating on the basis of a coordinated multilateral trading concept. The evaluation accounts for the overall costs of power generation, network losses, and system and unit constraints. We assume a non-collusive oligopolistic competition. An iterative Cournot model is used to characterize the competitive behavior of suppliers. A supplier maximizes the profit of each of his generating units while taking rivals' generation as given. Time span is over multiple hours. This leads to a mixed integer non-linear programming problem. We use the augmented Lagrangian approach to solve iteratively for globally optimal schedules. An IEEE 24-bus, 8-supplier, and 17-customer test system is used for illustration. The results show that such a market at times of light demands exhibits little market power, and at times of large demands exhibits a great deal of market power. This contrasts with the PCMI and HHI concentration measures, which give fixed measurement values of market power. The results of two-year (730 round) market simulations show a range of deadweight efficiency loss between 0.9 and 6% compared to that of PoolCo which results in a range between 0.5 and 10% for the same test case. 相似文献
39.
This paper presents a technical approach for electronic multilateral trade of electricity in competitive power industries. The trade involves strategic sharing of data among agents in an attempt to provide the opportunity to intelligently discover competitive behavior of peer suppliers. A trading logic is implemented as a specialized software module within the agent. The logic mimics intelligence of the human strategic trade. A time-bounded trade protocol has been introduced as a trading basis among rivalry trade agents in the market. The protocol limits the trade rounds in order to bind the trading process to specific deadlines. The protocol is coded as part of the automated trade server. The results of a generic 3-bus test system show that the electronic multilateral trade logic presented in this paper better distributes market sales, lowers prices and consequently provides higher social welfare compared to the standard Cournot economic model that may be used by the human decision-maker for market trading. Based on a set of test cases with different load profiles, it is noted that the electronic multilateral trade drives the market price closer to the marginal cost of generation supply and far away from the estimated Cournot price. 相似文献
40.
Noha M. Hassan Maher Y. Younan Hanadi G. Salem 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(10):38-42
The deformation behaviors of an Al-Li-Cu alloy (Aluminum 8090) during uniaxial and biaxial stress states were modeled using
the nonlinear finite element analysis package ABAQUS 5.8. Two different material models were used for the purpose of comparison and to propose a valid and accurate superplastic material
deformation behavior. Using a power law strain hardening model, the material was modeled with either constant or variable
properties of strain-rate sensitivity and strain-hardening exponent. Results from the numerical models were compared to experimental
results by Chen and Huang, who investigated the uniaxial and biaxial states of stress. Experimental data were primarily used
to acquire the needed uniaxial material parameters for the model. The strain-rate sensitivity and strain-hardening exponent
were dependent on the strain and strain rates. Comparing the two material models for both stress states indicated that the
material model with variable properties better represented the true behavior of the material when compared to the experimental
results.
For more information, contact Noha M. Hassan, the American University in Cairo, 113 Kasr El Aini St., P.O. Box 2511, Cairo
11511, Egypt; +202-797-5336; fax +202-797-7565; e-mail nhassan@vt.edu. 相似文献