全文获取类型
收费全文 | 93553篇 |
免费 | 7947篇 |
国内免费 | 4054篇 |
专业分类
电工技术 | 5376篇 |
技术理论 | 9篇 |
综合类 | 8570篇 |
化学工业 | 16676篇 |
金属工艺 | 1637篇 |
机械仪表 | 2117篇 |
建筑科学 | 14102篇 |
矿业工程 | 5217篇 |
能源动力 | 5790篇 |
轻工业 | 5447篇 |
水利工程 | 18908篇 |
石油天然气 | 7872篇 |
武器工业 | 238篇 |
无线电 | 1530篇 |
一般工业技术 | 4485篇 |
冶金工业 | 3479篇 |
原子能技术 | 1138篇 |
自动化技术 | 2963篇 |
出版年
2024年 | 285篇 |
2023年 | 1070篇 |
2022年 | 2143篇 |
2021年 | 2610篇 |
2020年 | 2783篇 |
2019年 | 2387篇 |
2018年 | 2274篇 |
2017年 | 2736篇 |
2016年 | 3108篇 |
2015年 | 3036篇 |
2014年 | 5754篇 |
2013年 | 5767篇 |
2012年 | 7015篇 |
2011年 | 7028篇 |
2010年 | 5183篇 |
2009年 | 5450篇 |
2008年 | 4781篇 |
2007年 | 6393篇 |
2006年 | 5907篇 |
2005年 | 5404篇 |
2004年 | 4209篇 |
2003年 | 3835篇 |
2002年 | 3308篇 |
2001年 | 2697篇 |
2000年 | 2236篇 |
1999年 | 1720篇 |
1998年 | 1259篇 |
1997年 | 1025篇 |
1996年 | 797篇 |
1995年 | 713篇 |
1994年 | 517篇 |
1993年 | 395篇 |
1992年 | 321篇 |
1991年 | 258篇 |
1990年 | 185篇 |
1989年 | 197篇 |
1988年 | 122篇 |
1987年 | 136篇 |
1986年 | 107篇 |
1985年 | 113篇 |
1984年 | 101篇 |
1983年 | 70篇 |
1982年 | 31篇 |
1981年 | 10篇 |
1980年 | 23篇 |
1979年 | 18篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
901.
论述了金属的电化学腐蚀和外加电流阴极保护原理。说明对以海水为介质的冷却、冷凝设备,采用外加电流阴极保护是防止设备腐蚀的有效方法。举例说明了应用效果。 相似文献
902.
The effects of poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), sodium polyacrylate (NaPA), poly(ethylene glycol) (PEG), pectin (P), and carboxymethyl cellulose (CMC) on the corrosion of cadmium in a 0.5M hydrochloric acid (HCl) solution were studied with both electrochemical impedance spectroscopy and Tafel plot techniques. Measurements were carried out at cathodic, open‐circuit, and anodic potentials. All the investigated polymers had inhibitory effects on both the cathodic (except for NaPA, P, and CMC) and anodic processes, with a predominant anodic inhibiting action. However, NaPA, P, and CMC exhibited a slight cathodic inhibiting action only at higher polymer concentrations. This behavior may be attributed to the very weak adsorbability of the polymers on the cathodic sites. Because PVA and PEG had hydroxy groups, there could be bridging between the polymer and the surface, resulting in an inhibiting effect in the HCl solution. However, PVA had much greater adsorbability on the surface than PEG at the anodic potential. The adsorption of most of the polymers obeyed a Temkin adsorption isotherm, and this indicated indicating that the main process of inhibition was adsorption. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 866–871, 2003 相似文献
903.
904.
905.
Heinz Ludwig 《Desalination》2004,164(1):1-18
Ever since seawater desalination has been applied on an industrial scale, and particular in the countries of the Arabian Gulf, the application of desalination processes in dual-purpose facilities—water and power—as a hybrid configuration has been discussed in many feasibility investigations and also planning concepts. It is above all the combination of reverse osmosis with thermal processes that has found increasing interest with the aim of ensuring, as economically as possible, uniform water supplies under the specific, greatly varying load conditions in the Gulf countries. Such design concepts for hybrid configurations encompass straightforward structures with a low degree of coupling between membrane and thermal desalination processes, but range up to very complex configurations with strong interconnections on both the water side and thermally, as well as with several desalination processes connected in series or in parallel. Classical hybrid concepts in which the permeate from an RO desalination component is mixed with distillate from thermal desalination have already been implemented in Saudi Arabian dual-purpose plants, like Jeddah and Yanbu-Medina. Although hybrid systems of greater complexity have been addressed in many design studies and publications, up to now none has been brought to fruition. Coming into consideration asthe design basis for determining the capacity shares of the various desalination processes operated in a hybrid configuration are: arrangement of thermal cycle of the power plant component; water/power ratio of the dual-purpose seawater desalination and power plant; provision of undiminished water production of the desalination plant as electricity generation varies; provision of a specified drinking water quality with regard to composition and salt content; combination of all these aspects. Also gaining in importance are concerns of environmental pollution and sustainable development when selecting seawater desalination and power plant configurations, as well as their optimization when considering desalination and electricity generation as a whole. In the practical design of hybrid membrane and thermal systems, aspects come to light, though, that restrict linking of the two systems and joint utilization of facilities, as conceived in studies and conceptual design investigations. This applies both for common utilization of intakes and the use of heated up cooling water from thermal processes as a feed stream for the RO part of the desalination process. Additionally, requirements of drinking water composition, particularly chloride content, TDS and compliance with a specific residual content of boron, influence specifically the design of the membrane process part and its share in the total desalination capacity. Such practical aspects have greatly influenced the design and configuration of the Fujairah hybrid plant for which, from a total desalination capacity of 100 MIGD (454,600 m3/d), the share of 37.5 MIGD (170,500 m3/d) makes its seawater RO plant the biggest currently being constructed anywhere in the world. From the findings of the engineering of this plant and the idea that, by increasing interconnection between the two processes on the water side, it is possible to advance a hybrid configuration of this type with regard to cost optimization in the membrane installation, but also by joint utilization of the intake equipment, perspectives result for applied research efforts over the near and long terms, for example: long-term behavior of membranes at elevated temperatures; tendency for biofouling in membrane process with common utilization of cooling water and brine; influences of such interconnections on the overall availability of the facility. But also for the operation and maintenance organization of such large facilities, consequences can be foreseen for the future development of hybrid plants, particularly for operation management and organisation of the interplay of the different power plant and desalination systems, monitoring of SWRO membrane replacement and cleaning, as well as controlling water quality. 相似文献
906.
在人类生存、发展的历史进程中,作为饮水用具的陶瓷杯盏经历了从无到有、由简单到复杂、由粗糙到精致的嬗变过程,而这一过程在很大程度上受到陶瓷生产技术、人们的饮水方式及审美情趣的变化等因素的影响。 相似文献
907.
908.
《Journal of Great Lakes research》2022,48(1):24-36
In Ontario, there is limited comprehensive research regarding the contribution of chloride in groundwater to surface water systems. The delivery of chloride via groundwater can contribute to the degradation of the Great Lakes and their tributaries. Thus, this review intends to fill or identify knowledge gaps regarding assessing groundwater as a potential source of road salt, the single largest use of salt in urban cold region environments, contamination to surface water by synthesizing existing groundwater chloride research in the Lake Ontario Basin. Knowledge regarding source characterization, properties, pathways, and impacts of chloride in the environment is essential to evaluate the contribution of chloride via groundwater. Past groundwater chloride research in the basin is primarily concentrated in highly urbanized areas and has identified localized trends of increasing groundwater chloride concentrations in these regions; however, few investigations have been conducted in varying land uses (e.g., rural or less urbanized watersheds) or at sufficient temporal and/or spatial scales. Significant chloride accumulation is occurring in watersheds and aquifers within the basin. Concentrations are expected to increase until equilibrium is obtained, thus resulting in sustained yearlong elevated concentrations in tributaries. Recently, chloride loading to Lake Ontario has increased significantly, with groundwater inputs having the potential to support long-term increases in chloride concentrations in the lake. However, few studies have evaluated the explicit contribution via groundwater to Lake Ontario, and therefore a knowledge gap continues to exist. We provide a synthesis of additional research priorities to better understand the magnitude of groundwater chloride issues in the basin. 相似文献
909.
受全球气候变暖的影响,“中华水塔”地区正面临着以“变暖变湿”为主的气候变化。受气候及下垫面条件的综合影响,区域水资源显著增加,各流域产流机理在空间上呈现出明显的地区差异特征。基于“中华水塔”区域1956—2020年水文气象资料,通过趋势、突变、距平等分析方法,分析其水文要素和产流规律的变化趋势、特征及相互之间影响关系。结果表明:近年来“中华水塔”区域气温显著升高,蒸发能力总体增强,区域进入丰水期,降水、径流显著增加,在同等降水径流尺度下,黄河源区产流能力有所降低,长江、澜沧江源区产流能力明显增强;气温升高、降水量持续偏丰以及流域前期影响雨量(蓄水量)增加、枯季径流比例提高、下垫面生态持水能力增强是引起区域产流规律变化、水资源量增加的主要原因。 相似文献
910.