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651.
The authors examined the prediction of occupational attainment by age 40 from contextual and personal variables assessed during childhood and adolescence in 2 participant samples: (a) the Columbia County Longitudinal Study, a study of 856 third graders in a semirural county in New York State that began in 1960, and (b) the Jyv?skyl? Longitudinal Study of Personality and Social Development, a study of 369 eight-year-olds in Jyv?skyl?, Finland, that began in 1968. Both samples were followed up during adolescence and early and middle adulthood. Structural modeling analyses revealed that in both countries, for both genders, children's age 8 cognitive-academic functioning and their parents' occupational status had independent positive long-term effects on the children's adult occupational attainment, even after other childhood and adolescent personal variables were controlled for. Further, childhood and adolescent aggressive behavior negatively affected educational status in early adulthood, which in turn predicted lower occupational status in middle adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
652.
W. H. Hager  K. Hutter 《Acta Mechanica》1984,53(3-4):183-200
Summary The differential equation that governs the longitudinal variation of the surface profileh(x) in steady plane channel flow is qualitatively discussed for the case of pseudo-uniform flow states. The solutions are either of the cnoidal or solitary wave type. It is shown that, among all cnoidal waves, solitary waves have minimum energy head. Further, surface profiles mustbreak whenever the Froude-number exceeds the value (which is close to experimentally determined values). The model equations are applied to the undular hydraulic jump, and it is shown how the equations can be used in practical situations of open channel flow hydraulics.With 11 Figures  相似文献   
653.
As part of an international measurement intercomparison of instruments used to measure atmospheric 222Rn, four participating laboratories made nearly simultaneous measurements of 222Rn activity concentration in commonly sampled, ambient air over approximately a 2 week period, and three of these four laboratories participated in the measurement comparison of 14 introduced samples with known, but undisclosed (“blind”) 222Rn activity concentration. The exercise was conducted in Bermuda in October 1991. The 222Rn activity concentrations in ambient Bermudian air over the course of the intercomparison ranged from a few hundredths of a Bq · m−3 to about 2 Bq · m−3, while the standardized sample additions covered a range from approximately 2.5 Bq · m−3 to 35 Bq · m−3. The overall uncertainty in the latter concentrations was in the general range of 10 %, approximating a 3 standard deviation uncertainty interval. The results of the intercomparison indicated that two of the laboratories were within very good agreement with the standard additions, and almost within expected statistical variations. These same two laboratories, however, at lower ambient concentrations, exhibited a systematic difference with an averaged offset of roughly 0.3 Bq · m−3. The third laboratory participating in the measurement of standardized sample additions was systematically low by about 65 % to 70 %, with respect to the standard addition which was also confirmed in their ambient air concentration measurements. The fourth laboratory, participating in only the ambient measurement part of the intercomparison, was also systematically low by at least 40 % with respect to the first two laboratories.  相似文献   
654.
The eastern Mediterranean faces a severe water crisis: water supply decreases due to climate change, while demand increases due to rapid population growth. The GLOWA Jordan River project generates science-based management strategies for maximizing water productivity under global climate change. We use a novel definition of water productivity as the full range of services provided by landscapes per unit blue (surface) and green (in plants and soil) water. Our combined results from climatological, ecological, economic and hydrological studies suggest that, in Israel, certain landscapes provide high returns as ecosystem services for little input of additional blue water. Specifically, cultural services such as recreation may by far exceed that of food production. Interestingly, some highly valued landscapes (e.g. rangeland) appear resistant to climate change, making them an ideal candidate for adaptive land management. Vice versa, expanding irrigated agriculture is unlikely to be sustainable under global climate change. We advocate the inclusion of a large range of ecosystem services into integrated land and water resources management. The focus on cultural services and integration of irrigation demand will lead to entirely different but productive water and land allocation schemes that may be suitable for withstanding the problems caused by climate change.  相似文献   
655.
656.
    
Biomass can be used for energy purposes by either combustion to heat and power or refining into solid and liquid biofuels. The majority of biomass is used for residential purposes in developing countries. Modern biomass use in industrialized countries is increasing, and more and more biomass is also traded to be used for energy purposes. The purpose of this paper is to locate the 15 largest ethanol, biodiesel, and wood pellet plants. Facilities generating heat, steam and electricity were left out. Secondly it is not generally known what share of biomass users are large plants. Also an effort is made to find out how much these large‐scale biomass refining plants use imported feedstock. For the most part, very large industrial processing facilities are found in a small number of countries. The largest ethanol mills are found almost exclusively in the United States, with one very large plant in the Netherlands. The distribution of biodiesel and wood pellet plants is more dispersed. The countries with the most large biodiesel plants include the USA, Brazil, Spain, and the Netherlands. The countries with the most very large wood pellet plants include the USA, Canada, Russia, and Germany. Torrefaction and pyrolysis technologies are still rarely used on industrial scale. Ethanol and wood pellet plants tend to be sourced from local feedstocks, while biodiesel plants are much more likely to use imported feedstocks or a mix of imports and local biomass. All of these fuels are increasingly traded through the international market. © 2014 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   
657.
Pedestrian-navigation services enable people to retrieve precise instructions to reach a specific location. However, the development of mobile spatial-information technologies for pedestrians is still at the beginning and faces several difficulties. As the spatial behavior of people on foot differs in many ways from the driver's performance, common concepts for car-navigation services are not suitable for pedestrian navigation. Particularly, the usage of landmarks is vitally important in human navigation. This contribution points out the main requirements for pedestrian-navigation technologies and presents an approach to identify pedestrian flows and to imply landmark information into navigation services for pedestrians  相似文献   
658.
三代(3G)无线通信正在快速地变成现实.3G得以成功实施,一个重要的原因是在传输的两端扮演了支撑角色的锗硅(SiGe)双极和BiCMOS工艺技术.在手机中,SiGe在更低的电压下给射频(RF)发射机和接收机带来更快的速率,在支持3 G多媒体通信所必需的更高带宽的同时,保持功耗降低.基站也从SiGe受益:高速的数据转换器和运算放大器成功地用更宽的带宽处理更多的通道.虽然SiGe的基本特性对两种应用而言是相似的,但对应于每种应用背后的半导体工艺之间有差别.  相似文献   
659.
Electrospinning is a long-known polymer processing technique that has received more interest and attention in recent years due to its versatility and potential use in the field of biomedical research. The fabrication of three-dimensional (3D) electrospun matrices for drug delivery and tissue engineering is of particular interest. In the present study, we identified optimal conditions to generate novel electrospun polymeric scaffolds composed of poly-d/l-lactide and poly-l-lactide in the ratio 50:50. Scanning electron microscopic analyses revealed that the generated poly(d/l-lactide-co-l-lactide) electrospun hybrid microfibers possessed a unique porous high surface area mimicking native extracellular matrix (ECM). To assess cytocompatibility, we isolated dermal fibroblasts from human skin biopsies. After 5 days of in vitro culture, the fibroblasts adhered, migrated and proliferated on the newly created 3D scaffolds. Our data demonstrate the applicability of electrospun poly(d/l-lactide-co-l-lactide) scaffolds to serve as substrates for regenerative medicine applications with special focus on skin tissue engineering.  相似文献   
660.
Cr, Cu, Zn, Co, Ni, Mo, Rh, Pd, Ag, Cd, Sb, Pt, Au, and U have been determined in clean room conditions by inductively coupled plasma sector field mass spectrometry and other analytical techniques, in various sections of two dated snow/ice cores from the high-altitude (4450 m asl) glacier saddle Colle Gnifetti, Monte Rosa massif, located in the Swiss-Italian Alps. These cores cover a 350-year time period, from 1650 to 1994. The results show highly enhanced concentrations for most metals in snow/ice dated from the second half of the 20th century, compared with concentrations in ancient ice dated from the 17th and 18th centuries. The highest increase factors from the pre-1700 period to the post-1970 period are observed for Cd (36), Zn (19), Bi (15), Cu (11), and Ni (9), confirming the importance of atmospheric pollution by heavy metals in Europe. Metal concentrations observed in Colle Gnifetti snow around 1980 appear to be quantitatively related to metal emissions from Italy, Switzerland, Germany, France, Belgium, and Austria at that time, making it possible to reconstruct past changes in metal emission in these countries during the last centuries.  相似文献   
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