全文获取类型
收费全文 | 1364篇 |
免费 | 65篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 260篇 |
金属工艺 | 27篇 |
机械仪表 | 54篇 |
建筑科学 | 20篇 |
能源动力 | 88篇 |
轻工业 | 80篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 192篇 |
一般工业技术 | 274篇 |
冶金工业 | 153篇 |
原子能技术 | 11篇 |
自动化技术 | 251篇 |
出版年
2024年 | 5篇 |
2023年 | 27篇 |
2022年 | 51篇 |
2021年 | 70篇 |
2020年 | 51篇 |
2019年 | 50篇 |
2018年 | 63篇 |
2017年 | 67篇 |
2016年 | 58篇 |
2015年 | 25篇 |
2014年 | 57篇 |
2013年 | 99篇 |
2012年 | 58篇 |
2011年 | 75篇 |
2010年 | 58篇 |
2009年 | 53篇 |
2008年 | 49篇 |
2007年 | 51篇 |
2006年 | 37篇 |
2005年 | 34篇 |
2004年 | 23篇 |
2003年 | 36篇 |
2002年 | 30篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 22篇 |
1998年 | 40篇 |
1997年 | 26篇 |
1996年 | 21篇 |
1995年 | 22篇 |
1994年 | 13篇 |
1993年 | 21篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1973年 | 5篇 |
1970年 | 3篇 |
1969年 | 5篇 |
排序方式: 共有1437条查询结果,搜索用时 578 毫秒
81.
82.
S Anand 《Canadian Metallurgical Quarterly》1982,6(6):236-241
Biomedical engineering has been recognized in India for the last decade. Technological developments have been in areas of importance to the country, with several groups actively involved in the promotion of bioengineering, particularly in New Delhi. A group at the National Physical Laboratory has contributed significantly to the field of ultrasonics as well as to the development of piezoelectric transducers for other biomedical uses. The Centre for Biomedical Engineering of the Indian Institute of Technology and the All India Institute of Medical Sciences is one of the country's leading centres producing outstanding work in areas like instrumentation, rehabilitation, biomaterials, modelling and analysis. Research in technology applied to reproductive physiology (an area especially relevant to India's needs) was initiated at this centre. Research at the School of Environmental Sciences, Jawaharlal Nehru University has elucidated the effects and mechanisms of the action of low-energy electromagnetic radiation and ultrasound on biological systems--in one of the school's projects the use of bone material for ultrasonic transducers and optical detectors was successfully demonstrated. A selected list of publications shows the wide spectrum of research carried out at these institutions. 相似文献
83.
The Capacitated Arc Routing Problem (CARP) stands among the hardest combinatorial problems to solve or to find high quality solutions. This becomes even more true when dealing with large instances. This paper investigates methods to improve on lower and upper bounds of instances on graphs with over 200 vertices and 300 edges, dimensions that, today, can be considered of large scale. On the lower bound side, we propose to explore the speed of a dual ascent heuristic to generate capacity cuts. These cuts are next improved with a new exact separation enchained to the linear program resolution that follows the dual heuristic. On the upper bound, we implement a modified Iterated Local Search procedure to Capacitated Vehicle Routing Problem (CVRP) instances obtained by applying a transformation from the CARP original instances. Computational experiments were carried out on the set of large instances generated by Brandão and Eglese and also on the regular size sets. The experiments on the latter allow for evaluating the quality of the proposed solution approaches, while those on the former present improved lower and upper bounds for all instances of the corresponding set. 相似文献
84.
Anand Arur P. Krishnan Grinson George M. P. Goutham Bharathi M. Kaliyamoorthy K. Hareef Baba Shaeb 《International journal of remote sensing》2013,34(17):6418-6443
Mesoscale eddies enhance the productivity in a stratified coastal environment by upwelling. The seas around the Andaman and Nicobar Islands have been found to have frequent mesoscale eddy activity. Commercial fishing grounds coincide with upwelling areas associated with cyclonic and anticyclonic eddies and also with areas between two adjacent eddies. There are different eddy zones supporting different types of fishing gears and fish. The current study aims at identifying the different zones of mesoscale eddies in the Andaman Sea and compares the productivity and fishing activity in each of them. Data collected from 454 commercial fishing trips in the Andaman Sea along with maps of sea level anomaly and Moderate Resolution Imaging Spectroradiometer (MODIS) global level 3 mapped thermal infrared (IR) daytime sea surface temperature (SST) from the Aqua and Terra satellites were used for the study. Known upwelling areas such as the periphery of anticyclonic and the core of cyclonic eddies showed higher catches in longlines, ring seines among the fishing gears, and among all the fish species groups. Downwelling areas such as the periphery of cyclonic and the core of anticyclonic eddies showed lower catches with ring seines and the fish species groups. Areas in between adjacent eddies were explored in this study and the fish captures in such areas were found to be different with types of fishing and the target fish group. The study shows results that link eddy activity with the performance of a fishery. 相似文献
85.
ABSTRACTSU5416 (Z-isomer), the first in its class of angiogenesis inhibitors, in solution converts to the E-isomer following light exposure and reverts to the Z-isomer in the dark. Kinetics of this Z-E isomerism in pharmaceutical media is reported. Analytical solutions need light protection at 5°C to maintain integrity. While E-isomer in light-exposed product increased to 0.9% in 24 hours, light-protected product showed no change (25°C, 18 months). Infusate studies indicated that < 1.9% E-isomer will be dosed to patients and would likely convert to the Z-isomer, following administration. This report implies Z-E isomerism in SU5416 is controllable with no limitations towards ensuring pharmaceutical product quality. 相似文献
86.
In this paper an aerosol charger that largely avoids the production of multiply charged particles in the 0.1–1.0 μm diameter range is described. The input aerosol is first passed through an electrostatic condenser to remove all charged particles and ions. The remaining neutral aerosol then flows into a 23-cm-long, 2.1-cm inner diameter cylindrical tube; the inner surface of this tube is uniformly coated with 0.09 μCi63 Ni, a 0.067 MeV β-emitter with a half-life of 92 years. At typical airflow rates of 0.2–1.0 lpm, this low-activity source of ionizing radiation produces bipolar ion concentrations ranging from 1 × 104 to 9 × 104 ion/cm3, which is much lower than levels required to bring the aerosol to Boltzmann charge equilibrium. At a flow rate of 1.0 lpm, particles smaller than about 1.0 μm typically interact with no more than one ion en route through the charger. Therefore, particles at the charger exit are mostly either neutral or singly charged. Charge distributions of initially-neutral mono-disperse polystyrene latex particles were measured at the exit from the charger for particle diameters ranging in size from 0.09 to 1.09 μm. It was found that, at an airflow rate of 1.0 lpm and particle size 1.09 μm, the ratios of singly, doubly, and triply charged to total positively charged concentrations were 0.75, 0.19, and 0.06 respectively; particles with more than three charges were not detected. In contrast, the analogous charge ratio at Boltzmann equilibrium is 0.28 (+ 1), 0.24 (+ 2), 0.19 (+ 3), 0.13 (+ 4), 0.08 (+ 5), 0.05 (+ 6), and 0.7 (+ 02). 相似文献
87.
B. J. Fran F. S. Wong A. R. McFarland N. K. Anand 《Aerosol science and technology》2013,47(4):326-332
Deposition of aerosol particles on the inner walls of sampling probes is of concern in many aerosol sampling applications. Only inertial and gravitational effects have been considered in previous studies of the aerosol deposition; however, the lift force on particles is also of significance. In this investigation, experiments have been conducted to construct a database for aerosol deposition in Willeke-type sampling probes. An empirical correlation has been made between wall losses and the depositional forces of drag, gravity, inertia, and particle lift through the use of dimensionless parameters. Inclusion of the lift effect in this correlation not only helps to better predict particle behavior in the sampling inlet, but it also provides a basis for understanding of the intrinsic deposition phenomenon. The correlation has a geometric standard deviation of 1.13 and a 0.93 correlation coefficient relative to the experimental data. 相似文献
88.
In this paper, the concept of application of morphological multistage watershed segmentation for detection of flaws in radiographic weld images is discussed. It is simple and intuitive and always produces a complete division of the image. The multistage watershed segmentation used here reduces the problem of over segmentation besides generating boundaries with very less deviation from their original position. Two-stage water segmentation is implemented here. At the first stage, watershed transform is applied to an X-ray image and the resultant mosaic image pattern is further thresholded by Otsu's thresholding method and converted into the binary image. Then, morphology and top-hat transformation is applied on binary image to separate partially overlapping objects. Euclidean distance map is calculated for each basin to label resultant segments uniquely and to separate ridges. This follows the second stage of watershed segmentation to obtain better-defined boundaries while removing over-segmented regions. Watershed segmentation algorithm has been able to detect flaws like slag inclusions and wormholes-type weld flaws. It shows all defects with reasonable accuracy having close contours. Similarly, small cavities are also highlighted successfully. 相似文献
89.
90.
Justin D. Mlcak N.K. Anand Michael J. Rightley 《International Journal of Heat and Mass Transfer》2008,51(21-22):5182-5191
Heat transfer and laminar fluid flow in an array of parallel microchannels etched on a silicon substrate with water as the circulating fluid was studied numerically. The fluid region consisted of a microchannel with a hydraulic diameter of 85.6 μm and aspect ratios ranging from 0.10 to 1.0. A constant heat flux of 90 W/cm2 was applied to the y = H face of the computational domain, which simulates thermal energy generation from an integrated circuit. Generalized transport equations were discretized and solved in three dimensions for velocities, pressure, and temperature. The SIMPLE algorithm [S.V. Patankar, Numerical Heat Transfer and Fluid Flow, Hemisphere, New York, 1980] was used to link pressure and velocity fields, and a thermally repeated boundary condition was applied in the lateral direction to model the repeating nature of the geometry. The numerical results for apparent friction coefficient and convective thermal resistance at the channel inlet and exit closely matched the experimental data in the literature for the case of 0.32 aspect ratio. Apparent friction coefficients were found to increase linearly with Reynolds number. Inlet and outlet thermal resistance values monotonically decreased with increasing Reynolds number and increased with aspect ratio. 相似文献