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991.
电力污染之谐波的抑制 总被引:1,自引:0,他引:1
电力谐波会使电网电能的生产、传输和利用效率降低;使电气设备产生嗓音、缩短使用寿命、故障甚至烧毁;造成电能计量混乱;严重干扰通讯设备和电子设备信号.文中对电力污染中谐波现象及危害进行陈述,分析产生谐波的主要原因,提出治理谐波问题的新思路. 相似文献
992.
综述了污水处理中重金属对生物反应动力学常数,活性污泥微生物群落结构及污水生物处理效率的影响,进而研究了重金属对生物脱氮除磷的毒性效应,对提高污水处理效果具有重要的现实意义。 相似文献
993.
Conesa HM María-Cervantes A Alvarez-Rogel J González-Alcaraz MN 《The Science of the total environment》2011,409(20):4470-4479
The aims of this study were to determine the factors which control metal and As phytoavailability in the different microenvironments (Sand Dunes, Salt Flat, Dry River and Shrubs) present at a Mediterranean salt marsh polluted by mining wastes. We performed a field study following a plot sampling survey. The analyses of soil parameters (pH, electrical conductivity (EC), organic carbon contents, etc.), total metal and As concentrations and their phytoavailability assessed with EDTA were related to each microenvironment and the corresponding plant species uptake. The averages of pH and EC were slightly alkaline (pH ≈ 7.5) and saline (≈ 2.2 to 17.1 dS m−1) respectively. The soil samples from the Salt Flat subzone showed the highest metal concentrations (e.g. 51 mg kg−1 Cd, 11,600 mg kg−1 Pb) while for As, the highest concentrations occurred in the Dry River (380 mg kg−1 As). The total metal and EDTA-extractable concentrations occurred as it follows: Salt Flat > Dry River > Degraded Dunes > Shrubs. In relation to plant metal and As accumulation, the highest root concentrations were obtained in the species from the Salt Flat subzone: ~ 17 mg kg−1 As, ~ 620 mg kg−1 Pb, for both, Juncus maritimus and Arthrocnemum macrostachyum. However the highest metal and As shoot concentrations occurred in species from the Sand Dunes: ~ 23 mg kg−1 As ~ 270 mg kg−1 Pb for Dittrichia viscosa; ~ 23 mg kg−1 As, ~ 390 mg kg−1 Zn for Crucianella maritima. The occurrence of edaphic gradients including salinity and texture determined the vegetation distribution. However, it cannot be concluded that there was a disturbance due to metal(loid)s soil concentrations in terms of vegetation composition except in the Degraded Dunes and Dry River. The higher EDTA-extractable concentrations were coincidental with the most saline soils but this did not result in higher metal(loid)s plant accumulation. 相似文献
994.
995.
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997.
Air pollution and meteorological processes in the growing dryland city of Urumqi (Xinjiang, China) 总被引:1,自引:0,他引:1
Seven years (2000-2006) of monthly PM10 (particulate matter, d ≤ 10 μm), SO2, and NO2 concentrations are reported for Urumqi, the capital of Xinjiang in NW China. Considerably high mean annual concentrations have been observed, which ranged between 150 and 240 μg m− 3 (PM10), 31 and 50 μg m− 3 (NO2), and 49 and 160 μg m− 3 (SO2). The shapes of seasonal variation of all pollutants were remarkably similar; however, winter/summer ratios of concentrations were quite different for PM10 (2-3) and NO2 (≈ 4) compared to SO2 (up to 30). Very high consumption rates of fossil fuels for energy generation and domestic heating are mainly responsible for high annual pollution levels, as well as the (very) high winter/summer ratios. Detailed analysis of the 2000-2006 records of Urumqi's meteorological data resulted in inter-annual and seasonal frequency distributions of (a) (surface) inversion events, (b) heights of surface inversions, (c) stability classes of Urumqi's boundary layer, and (d) the “Air Stagnation Index (ASI)”. Urumqi's boundary layer is shown to be characterized by high mean annual and seasonal frequencies of (surface) inversions and by the dominance of stable dispersion classes. A further outcome of the meteorological analysis is the proof of Urumqi's strong diurnal wind system, which might have particularly contributed to the stabilization of the nocturnal boundary layer. Annual and seasonal variations of pollutant's concentrations are discussed in the context of occurrences of inversions, boundary layer, stability classes, and ASI. The trend of Urumqi's air pollution indicates a strong increase of mean annual concentrations 2000-2003, followed by a slight increase during 2003-2006. These are in strong contrast to (a) the growth of Urumqi's fleet of motor vehicles and (b) to the growing number of stable regimes of Urumqi's boundary layer climate during same period. It is concluded that the (regional and) local administrative technical countermeasures have efficiently lowered Urumqi's air pollution levels. 相似文献
998.
Nitrogen pollution and source identification in the Haicheng River basin in Northeast China 总被引:3,自引:0,他引:3
A survey was conducted in the Haicheng River near Liaodong Bay to analyze the characteristics and sources of the in-stream nitrogen pollution throughout the year 2010. The results indicated that the total nitrogen (TN) concentrations in the river water all exceeded the GB3838-2002 standard for Class V guideline of 2.0 mg/l at all sampling sites during the sampling seasons. Ammoniacal nitrogen (NH3-N) dominated TN during the spring season, while nitrate nitrogen (NO3-N) dominated during the summer and autumn seasons. Different forms of nitrogen had significant seasonal variations (p < 0.01 or p < 0.05). Only NH3-N and NO3-N displayed distinct spatial differences at p < 0.05 and p < 0.001, respectively. Most forms of nitrogen were interrelated with physicochemical parameters during different seasons, displaying nitrification and denitrification processes that occurred in the river rather than seasonal biological demand. Based on the nitrogen parameters, the 30 sampling sites were divided into three clusters, by which the pollution sources from chemical nitrogen fertilizers, animal wastes, domestic sewage, and industrial wastewater were identified. Generally, the Haicheng River basin provided about 700 tons of the annual TN flux, contributing to the eutrophication of the Liaodong Bay and Bohai Sea. 相似文献
999.
1000.
Most household fuels used in Asian countries are solid fuels such as coal and biomass (firewood, crop residue and animal dung). The particulate matter (PM), CO, NOx and SOx produced through the combustion of these fuels inside the residence for cooking and heating has an adverse impact on people's health. PM 2.5 in particular, consisting of particles with an aerodynamic diameter of 2.5 μm or less, penetrates deep into the lungs and causes respiratory system and circulatory system diseases and so on. As a result, the World Health Organization (WHO) established guideline values for this type of particulate matter in 2005. In this study, the authors focused on PM 2.5 and estimated indoor exposure concentrations for PM 2.5 in 15 Asian countries. For each environment used for cooking, eating, heating and illumination in which people are present temporarily (microenvironment), exposure concentrations were estimated for individual cohorts categorized according to sex, age and occupation status. To establish the residence time in each microenvironment for each of the cohorts, data from time use surveys conducted in individual countries were used. China had the highest estimate for average exposure concentration in microenvironment used for cooking at 427.5 μg/m3 , followed by Nepal, Laos and India at 285.2 μg/m3, 266.3 μg/m3 and 205.7 μg/m3 , respectively. The study found that, in each country, the PM2.5 exposure concentration was highest for children and unemployed women between the ages of 35 and 64. The study also found that the exposure concentration for individual cohorts in each country was greatly affected by people's use of time indoors. Because differences in individual daily life activities were reflected in the use of time and linked to an assessment of exposure to indoor air-polluting substances, the study enabled detailed assessment of the impact of exposure. 相似文献