全文获取类型
收费全文 | 3077篇 |
免费 | 233篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 38篇 |
综合类 | 3篇 |
化学工业 | 762篇 |
金属工艺 | 89篇 |
机械仪表 | 240篇 |
建筑科学 | 46篇 |
矿业工程 | 5篇 |
能源动力 | 132篇 |
轻工业 | 281篇 |
水利工程 | 14篇 |
石油天然气 | 4篇 |
武器工业 | 3篇 |
无线电 | 513篇 |
一般工业技术 | 620篇 |
冶金工业 | 163篇 |
原子能技术 | 32篇 |
自动化技术 | 373篇 |
出版年
2024年 | 6篇 |
2023年 | 56篇 |
2022年 | 73篇 |
2021年 | 128篇 |
2020年 | 106篇 |
2019年 | 134篇 |
2018年 | 124篇 |
2017年 | 123篇 |
2016年 | 142篇 |
2015年 | 94篇 |
2014年 | 161篇 |
2013年 | 220篇 |
2012年 | 201篇 |
2011年 | 259篇 |
2010年 | 155篇 |
2009年 | 176篇 |
2008年 | 150篇 |
2007年 | 148篇 |
2006年 | 120篇 |
2005年 | 92篇 |
2004年 | 79篇 |
2003年 | 76篇 |
2002年 | 45篇 |
2001年 | 58篇 |
2000年 | 39篇 |
1999年 | 39篇 |
1998年 | 64篇 |
1997年 | 38篇 |
1996年 | 39篇 |
1995年 | 28篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 22篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1964年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有3318条查询结果,搜索用时 0 毫秒
1.
Salim Hengky K. Padfield Rory Lee Chew Tin Syayuti Khadijah Papargyropoulou Effie Tham Mun Hou 《Clean Technologies and Environmental Policy》2018,20(3):529-538
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food... 相似文献
2.
3.
4.
In polyolefin processes the melt index (MI) is the most important control variable indicating product quality. Because of
the difficulty in the on-line measurement of MI, a lot of MI estimation and correlation methods have been proposed. In this
work a new dynamic MI estimation scheme is developed based on system identification techniques. The empirical MI estimation
equation proposed in the present study is derived from the 1
st
-order dynamic models. Effectiveness of the present estimation scheme was illustrated by numerical simulations based on plant
operation data including grade change operations in high density polyethylene (HDPE) processes. From the comparisons with
other estimation methods it was found that the proposed estimation scheme showed better performance in MI predictions. The
virtual sensor model developed based on the estimation scheme was combined with the virtual on-line analyzer (VOA) to give
a quality control system to be implemented in the actual HDPE plant. From the application of the present control system, significant
reduction of transition time and the amount of off-spec during grade changes was achieved 相似文献
5.
EK Yeong R Mann M Goldberg L Engrav D Heimbach 《Canadian Metallurgical Quarterly》1996,40(6):956-61; discussion 961-2
The utility of the laser Doppler for determining burn depth has been questioned because of problems with technology and methodology. This study prospectively evaluates the ability of a new laser Doppler technique to predict burn healing time. Using the Periflux System 4000 laser Doppler, readings were taken on 305 burns (147 patients) on postburn day 3 or 4. Sixty-six wounds were used to derive a predictive function (phase I) and 152 wounds were used to test the function (phase II). Blood flow dynamics (flux), microvascular dilation capacity of the wounds to beat stress, and flow motion wave pattern (vasomotion) were studied using the laser Doppler, and seven parameters were evaluated to determine their relative contribution to the prediction of healing time. These parameters are hyperemic flux (flux value after heating to 42 degrees C), average hyperemic wave amplitude (AHWA), number of average flux units >100(F100), number readings with wave amplitude 75 (A5), average flux change (AFC), percentage of average flux increase, and relative flow capacity (RFC = AFC/average hyperemic flux). After readings were made, the wounds were observed and divided into two groups: those that healed in less than 14 days and those that healed or were grafted after 14 days. A step-wise discriminant analysis was used to assess the relative contribution of the Doppler-derived measures to healing time prediction. AHWA, F100, and RFC were included in the final discriminant function explaining 72% of the healing time variance (Wilks' lambda value 0.28; p value <0.0001). Predicted outcome = 0.05(AHWA) + 0.31(F100) + 5.0(RFC) - 2.3. With this derived function, there is 94% accuracy in the prediction of burn wound healing time compared with a physician predictive accuracy of 70%. 相似文献
6.
A young child with [S, L, L] segmental anatomy, double-inlet left ventricle, transposition of the great arteries, rudimentary right ventricle, and mildly restrictive bulboventricular foramen is reported, in whom intraoperative temporary snaring of the modified Blalock-Taussig shunt resulted in instantaneous and dramatic volume contraction of the left ventricle, decrease in bulboventricular foramen size, and increase of the gradient across the latter from 10 mm Hg preoperatively to 50 mm Hg. A modified Damus-Stansel-Kaye procedure using autogenous aortic tissue resulted in unobstructed aortic outflow; in addition, a bidirectional cavopulmonary shunt was performed. The importance of early relief of actual or potential aortic outflow obstruction in hearts with restrictive bulboventricular foramen is emphasized. 相似文献
7.
During the 1997 winter season, shipborne polarimetric backscatter measurements of Great Lakes (freshwater) ice types using the Jet Propulsion Laboratory C-band scatterometer, together with surface-based ice physical characterization measurements and environmental parameters, were acquired concurrently with Earth Resource Satellite 2 (ERS-2) and RADARSAT Synthetic Aperture Radar (SAR) data. This polarimetric data set, composed of over 20 variations of different ice types measured at incident angles from 0° to 60° for all polarizations, was processed to radar cross-section to establish a library of signatures (look-up table) for different ice types. The library is used in the computer classification of calibrated satellite SAR data. Computer analysis of ERS-2 and RADARSAT ScanSAR images of Great Lakes ice cover using a supervised classification technique indicates that different ice types in the ice cover can be identified and mapped, and that wind speed and direction can have an influence on the classification of water as ice based on single frequency, single polarization data. Once satellite SAR data are classified into ice types, the ice map provides important and necessary input for environmental protection and management, ice control and ice breaking operations, and ice forecasting and modeling efforts. 相似文献
8.
This paper proposes a new LDMOSFET structure with a trenched sinker for high‐power RF amplifiers. Using a low‐temperature, deep‐trench technology, we succeeded in drastically shrinking the sinker area to one‐third the size of the conventional diffusion‐type structure. The RF performance of the proposed device with a channel width of 5 mm showed a small signal gain of 16.5 dB and a maximum peak power of 32 dBm with a power‐added efficiency of 25% at 2 GHz. Furthermore, the trench sinker, which was applied to the guard ring to suppress coupling between inductors, showed an excellent blocking performance below ?40 dB at a frequency of up to 20 GHz. These results confirm that the proposed trenched sinker should be an effective technology both as a compact sinker for RF power devices and as a guard ring against coupling. 相似文献
9.
Hyukmin Son Sanghoon Lee 《Communications Letters, IEEE》2006,10(5):360-362
A cell planning technique termed BRD (bandwidth and region division) is presented for overcoming interference, maintaining QoS (quality of service) and improving channel capacity over OFDM (orthogonal frequency division multiplexing)-based broadband cellular networks. Through an optimal combination of sectorization and zero padding, bandwidth and region division is achieved that minimizes the outage probability for forward-link cell planning. In order to verify the effectiveness of the proposed algorithm, a Monte Carlo simulation is performed over multi-cell environments. 相似文献
10.
R Mann EK Yeong ML Moore LH Engrav 《Canadian Metallurgical Quarterly》1997,18(2):160-3; discussion 159
This article introduces a new tool to measure the pressure that is under pressure garments. The Iscan (Tekscan, Inc.) system uses a patented ultra-thin (0.007 inch) sensor with multiple sensing locations that sample continuously at 100 times per second. It is noninvasive, convenient, and quick. The study had two parts. First, we established the validity and reliability of the device. Next, garment/scar interface pressures were measured on new garments with use of the Iscan system. Four garment types were studied, with 10 measurements made in each group: Isotoner gloves (Smith & Nephew Roylan, Inc.); custom-fit pressure gloves; Tubigrip forearm sleeves (Seton Health Care Group); and custom-fit pressure forearm sleeves. Mean garment/scar interface pressures were 18 +/- 2 mm Hg for the Isotoner glove, 34 +/- 5 mm Hg for the custom-fit pressure glove, 20 +/- 7 mm Hg for the Tubigrip sleeve, and 35 +/- 6 mm Hg for the custom-fit sleeve. We concluded that the Iscan system can be used to measure pressure under pressure garments accurately and reliably, and that custom-fit hand and forearm garments provide more pressure than Isotoner gloves or Tubigrip sleeves. 相似文献