全文获取类型
收费全文 | 3088篇 |
免费 | 127篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 88篇 |
综合类 | 13篇 |
化学工业 | 442篇 |
金属工艺 | 55篇 |
机械仪表 | 70篇 |
建筑科学 | 137篇 |
矿业工程 | 3篇 |
能源动力 | 127篇 |
轻工业 | 231篇 |
水利工程 | 29篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 621篇 |
一般工业技术 | 503篇 |
冶金工业 | 482篇 |
原子能技术 | 25篇 |
自动化技术 | 388篇 |
出版年
2023年 | 18篇 |
2022年 | 56篇 |
2021年 | 44篇 |
2020年 | 27篇 |
2019年 | 36篇 |
2018年 | 53篇 |
2017年 | 61篇 |
2016年 | 58篇 |
2015年 | 67篇 |
2014年 | 119篇 |
2013年 | 193篇 |
2012年 | 156篇 |
2011年 | 187篇 |
2010年 | 128篇 |
2009年 | 129篇 |
2008年 | 149篇 |
2007年 | 121篇 |
2006年 | 128篇 |
2005年 | 98篇 |
2004年 | 88篇 |
2003年 | 76篇 |
2002年 | 84篇 |
2001年 | 67篇 |
2000年 | 65篇 |
1999年 | 77篇 |
1998年 | 191篇 |
1997年 | 133篇 |
1996年 | 78篇 |
1995年 | 71篇 |
1994年 | 61篇 |
1993年 | 65篇 |
1992年 | 36篇 |
1991年 | 24篇 |
1990年 | 37篇 |
1989年 | 22篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1975年 | 14篇 |
1974年 | 9篇 |
1972年 | 9篇 |
1965年 | 6篇 |
排序方式: 共有3223条查询结果,搜索用时 15 毫秒
131.
132.
氧气平炉的电除尘灰粒径小,水渗透性差,因而极易在空中飘浮,在装卸、运输、储存的过程中,易造成二次环境污染。用颗粒状没有粘性的平炉水淬渣作吸附体,与电除尘灰一起加水搅拌成渣灰混合料,既解决了电除尘灰对环境的污染问题,又为烧结厂提供了合格原料。 相似文献
133.
Maximum reflectance, Rmax, can be calculated by the following equation: in which R1, R2, and R3 are three separate reflectance readings on the same vitrinite grain at 45° angular intervals. The equation is derived from the reflectance distribution function for a central section of a reflectance indicatrix: Rα = Rmaxcos2α + R′minsin2α where Rα is the reflectance measured in the direction α degrees from Rmax, R′min is an apparent minimum which has the minimum value on this central section, and Rmax ? R′min ? Rmin. This new technique can be further simplified by rotating the polarizer in 45-degree intervals to obtain three photometer readings and then converting them to R1, R2, and R3, by the use of empirically-established conversion factors. The new techniques do not require the full revolution of the microscope stage and, therefore, are particularly suitable for measuring small grains of vitrinite. 相似文献
134.
A study was made of the change in anisotropy field, coercivity, angular dispersion, and creep threshold of an ordinary Ni-Fe film when coupled with a stripe-domain film. It was found that the values of these properties all increased as a result of the coupling. 相似文献
135.
General error criteria and probability distributions on the circle are studied in connection with estimation by using their Fourier series representations. Conditional probability densities for certain discrete-time folded normal processes, which are analogous to the continuous-time processes associated with the bilinear problems considered in Part I of this series, are computed. An intrinsic physical difference between the discrete-time and continuous-time problems is discussed, and the complexity of the estimation equations in the discrete-time case is analyzed in this setting. Suboptimal sequential filtering schemes are briefly discussed. In addition, Fourier analysis of conditional probability distributions exposes the inherent rich structure in quite general classes of estimation problems on the circle. 相似文献
136.
Measured attenuations associated with a variety of cloud conditions at wavelengths near 8.6 and 3.2 mm are reported. Two specific events, during which heavy rain clouds covered the sky, are examined and statistical data collected over a six-month period on a variety of cloud types are presented. The number of observations of some cloud types was not large and it was not possible to account for the gaseous attenuation with sufficient accuracy to get reliable values for the attenuation by the cloud droplets for a number of cloud types. The clouds causing the largest attenuations were the rain-bearing cumulonimbus ones. Of the nonrain clouds the two types for which the sample sizes are adequate and attenuations are sufficient for meaningful conclusions are stratocumulus and cumulus, their 35 GHz/95 GHz mean attenuation values being 0.18/0.61 dB and 0.12/0.34 dB, respectively. 相似文献
137.
Protein concentrates have been prepared from rapeseed meals by extraction with sodium chloride solution, followed by removal of the seed coat by screen filtration. This method yielded up to 75% of the original meal N in the form of products containing 61–64% protein (Nx 6·25). The products showed a considerably greater content of ash, and lower content of crude fibre and glucosinolate than did the starting meals, but amino acid patterns were similar and P levels were unchanged. Protein quality of the products prepared from heat-treated (myrosinase-inactivated) meals, was measured by determination of protein efficiency ratio and net protein utilisation, and was found to be similar to that of casein. 相似文献
138.
Traditional fault detection and isolation methods are based on quantitative models which are sometimes difficult and costly to obtain. In this paper, qualitative bond graph (QBG) reasoning is adopted as the modeling scheme to generate a set of qualitative equations. The QBG method provides a unified approach for modeling engineering systems, in particular, mechatronic systems. An input-output qualitative equation derived from QBG formalism performs continuous system monitoring. Fault diagnosis is activated when a discrepancy is observed between measured abnormal behavior and predicted system behavior. Genetic algorithms (GA's) are then used to search for possible faulty components among a system of qualitative equations. In order to demonstrate the performance of the proposed algorithm, we have tested it on a laboratory scale servo-tank liquid process rig. Results of the proposed model-based fault detection and diagnosis algorithm for the process rig are presented and discussed. 相似文献
139.
This paper proposes a qualitative assessment methodology that is comprised of a cluster analysis and an autoregression analysis that assess the effects of various road safety strategies implemented in Hong Kong over the last 10 years. The cluster analysis is first used to group over a hundred road safety projects and programs into a smaller set of meaningful road safety policy strategy clusters. These strategies, together with the trend factor, seasonal pattern, car crashworthiness and meteorological data are then used in the autoregression analysis to relate to the fatality and casualty rates of drivers, passengers, motorcyclists, and pedestrians. This method allows the evaluation of the overall effects of the road safety strategies, and the effects and relative significance of each individual strategy. The evaluation method is described, and the main findings of the study are discussed. 相似文献
140.
A cellobiose dehydrogenase (CDH)-modified graphite electrode was designed for amperometric detection of catecholamines in the flow injection mode, by their recycling between the graphite electrode (+300 mV vs Ag|AgCl) and the reduced FAD cofactor of adsorbed CDH, resulting in an amplified response signal. The high efficiency of the enzyme-catecholamine reaction leads to a detection limit below 1 nM and a sensitivity of 15.8 A.M(-1) x cm(-2) (approximately 1150 nA/microM) for noradrenaline, with a coverage of less than 2.5 microg of CDH adsorbed on the electrode surface (0.073 cm(2)). Working parameters such as pH, cellobiose concentration, carrier buffer, and applied potential were optimized, using hydroquinone as a model analyte. The sensitivity, linear range, and amplification factor can be modulated by the steady-state concentration of cellobiose in the flow buffer. The response of the sensor decreases only 2% when run continuously for 4 h in the flow injection mode. The response peak maximum is obtained within 6 s at a flow rate of 0.5 mL/min, representing the time of the entire sample segment to pass the electrode. CDH enzymes from Phanerochaete chrysosporium and Sclerotium rolfsii were investigated, providing different characteristics of the sensor, with sensors made with CDH from P. chrysosporium being the better ones. 相似文献