全文获取类型
收费全文 | 6560篇 |
免费 | 196篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 82篇 |
综合类 | 8篇 |
化学工业 | 1276篇 |
金属工艺 | 215篇 |
机械仪表 | 191篇 |
建筑科学 | 141篇 |
矿业工程 | 11篇 |
能源动力 | 475篇 |
轻工业 | 573篇 |
水利工程 | 76篇 |
石油天然气 | 88篇 |
武器工业 | 2篇 |
无线电 | 722篇 |
一般工业技术 | 1380篇 |
冶金工业 | 789篇 |
原子能技术 | 69篇 |
自动化技术 | 684篇 |
出版年
2023年 | 103篇 |
2022年 | 212篇 |
2021年 | 253篇 |
2020年 | 217篇 |
2019年 | 202篇 |
2018年 | 299篇 |
2017年 | 249篇 |
2016年 | 250篇 |
2015年 | 166篇 |
2014年 | 238篇 |
2013年 | 492篇 |
2012年 | 256篇 |
2011年 | 317篇 |
2010年 | 237篇 |
2009年 | 254篇 |
2008年 | 236篇 |
2007年 | 189篇 |
2006年 | 187篇 |
2005年 | 116篇 |
2004年 | 92篇 |
2003年 | 101篇 |
2002年 | 82篇 |
2001年 | 61篇 |
2000年 | 75篇 |
1999年 | 89篇 |
1998年 | 221篇 |
1997年 | 156篇 |
1996年 | 131篇 |
1995年 | 103篇 |
1994年 | 83篇 |
1993年 | 89篇 |
1992年 | 67篇 |
1991年 | 66篇 |
1990年 | 53篇 |
1989年 | 60篇 |
1988年 | 48篇 |
1987年 | 45篇 |
1986年 | 53篇 |
1985年 | 69篇 |
1984年 | 50篇 |
1983年 | 57篇 |
1982年 | 61篇 |
1981年 | 61篇 |
1980年 | 52篇 |
1979年 | 46篇 |
1978年 | 26篇 |
1977年 | 39篇 |
1976年 | 46篇 |
1974年 | 28篇 |
1973年 | 23篇 |
排序方式: 共有6782条查询结果,搜索用时 10 毫秒
91.
92.
93.
This paper addresses the problem of target coverage for wireless sensor networks, where the sensing range of sensors can vary, thereby saving energy when only close targets need to be monitored. Two versions of this problem are addressed. In the first version, sensing ranges are supposed to be continuously adjustable (up to the maximum sensing range). In the second version, sensing ranges have to be chosen among a set of predefined values common to all sensors. An exact approach based on a column generation algorithm is proposed for solving these problems. The use of a genetic algorithm within the column generation scheme significantly decreases computation time, which results in an efficient exact approach. 相似文献
94.
95.
In component‐based development, software systems are built by assembling components already developed and prepared for integration. To estimate the quality of components, complexity, reusability, dependability, and maintainability are the key aspects. The quality of an individual component influences the quality of the overall system. Therefore, there is a strong need to select the best quality component, both from functional and nonfunctional aspects. The present paper produces a critical analysis of metrics for various quality aspects for components and component‐based systems. These aspects include four main quality factors: complexity, dependency, reusability, and maintainability. A systematic study is applied to find as much literature as possible. A total of 49 papers were found suitable after a defined search criteria. The analysis provided in this paper has a different objective as we focused on efficiency and practical ability of the proposed approach in the selected papers. The various key attributes from these two are defined. Each paper is evaluated based on the various key parameters viz. metrics definition, implementation technique, validation, usability, data source, comparative analysis, practicability, and extendibility. The paper critically examines various quality aspects and their metrics for component‐based systems. In some papers, authors have also compared the results with other techniques. For characteristics like complexity and dependency, most of the proposed metrics are analytical. Soft computing and evolutionary approaches are either not being used or much less explored so far for these aspects, which may be the future concern for the researchers. In addition, hybrid approaches like neuro‐fuzzy, neuro‐genetic, etc., may also be examined for evaluation of these aspects. However, to conclude that one particular technique is better than others may not be appropriate. It may be true for one characteristic by considering different set of inputs and dataset but may not be true for the same with different inputs. The intension in the proposed work is to give a score for each metric proposed by the researchers based on the selected parameters, but certainly not to criticize any research contribution by authors. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
96.
In this paper, we present an accurate and general interconnect model for planar transmission line interconnects with arbitrary boundary conditions. Based on the unified approach, we develop a SPICE-compatible parameter extraction algorithm that can be used in high-performance computer-aided-design applications. A range of multilayered interconnect geometries with arbitrary boundaries are analyzed. Different typical configurations of ground placement are considered to verify the applicability of this method. For all such cases, results are compared for admittance, line parameters, and delay giving physical insight on the effect of boundary conditions on them. Compared with existing industry standard numerical field-solvers, like HFSS, the proposed model demonstrates more than 10× speedup within 2% accuracy. 相似文献
97.
P V Ananthapadmanabhan A V Bapat A K Das B K Karan R Majumder R K Marwah D S Patil S V K Rao V K Rohatgi K G Sankaran P Satyamurthy R Sharma P B Shrivastava M K Totlani N Venkat-Ramani F A Akopov A V Karpukhin V V Kirillov V I Maksimenko A S Prokop A I Romanov B V Roshin E V Shishkov A S Tikhotsky V I Zalkind N I Antonov V V Brajevsky D K Burenkov V A Efremov V N Sukhov 《Sadhana》1982,5(3):169-195
This paper summarizes the major results of the joint Indo-Soviet experiment for testing the Indianmhd generator channel section, designed and fabricated at the Bhabha Atomic Research Centre, Bombay, which was carried out at the U-02 facility in Moscow, USSR, in May 1980. The total test duration was 65 hours and included electrophysical tests and life tests under applied electric fields. The main purpose of the tests was to substantiate the physical concepts, computer codes, design features and special processing techniques involved in the development ofmhd generators for the Indian pilot plant at Tiruchirapalli. The experimental observations on the phenomena of heat transfer to the walls, gas dynamics in the channel, electrical characteristics of the generator and near-electrode processes including the analysis of arc spots correlate with the theoretical estimates based on present understanding of the physical processes occuring in similarmhd generators. The post-operational inspection of the channel section and extensive investigation of materials through microscopic analysis, chemical analysis and x-ray analysis are also reported in this paper. The joint test programme has clearly demonstrated the definite operating capability of the test section and has given sufficient information and encouragement for building better and improved channels for the future. 相似文献
98.
Purnendu Parhi Satya Sadhan Singh Alok R. Ray A. Ramanan 《Bulletin of Materials Science》2006,29(2):115-118
This communication reports a novel mechanochemically assisted room temperature solid state metathesis reaction for the synthesis
of submicron-size alkaline-earth molybdates crystallizing in a tetragonal Scheelite structure. The solids were characterized
by powder XRD, FTIR, TGA, DTA, SEM, EDAX and TEM to ascertain their composition, phase homogeneity and morphology. 相似文献
99.
D. Patidar R. Sharma N. Jain T. P. Sharma N. S. Saxena 《Bulletin of Materials Science》2006,29(1):21-24
Chemical method has been used to prepare cadmium sulphide by using cadmium, hydrochloric acid and H2S. The reflection spectra of covered and uncovered sintered films of CdS have been recorded by ‘Hitachi spectrophotometer’
over the wavelength range 300–700 nm. The energy band gaps of these films have been calculated from reflection spectra. It
is found that the energy band gap of both films is same as 2.41 eV. It is indicated that energy band gap of these films does
not change. This value of band gap is in good agreement with the value reported by other workers. The measurement of photocurrent
has also been carried out using Keithley High Resistance meter/ Electrometer. This film shows the high photosensitivity and
high photocurrent decay. Thus so obtained films are suitable for fabrication of photo detectors and solar cells. 相似文献
100.
M. Darvizeh H. Haftchenari A. Darvizeh R. Ansari C.B. Sharma 《Composite Structures》2006,74(4):495-502
A calculation of overall dynamic response of thin orthotropic cylindrical shells is presented. Due to the obvious importance of the effects of transverse shear deformation and rotary inertia, these terms are included in the analysis. The exact method is modified to predict the dynamic behavior of an orthotropic circular cylindrical shell. The modal forms are assumed to have the axial dependence in the form of a simple Fourier series. By using the present modified exact analysis various aspects such as influence of boundary conditions, changes in shell geometrical parameters, changes in the directions of orthotropy, etc., on the frequencies, mode shapes and modal forces are studied. Analytical results are shown to be in good agreement with some available experimental and theoretical results. 相似文献