全文获取类型
收费全文 | 157887篇 |
免费 | 9734篇 |
国内免费 | 5695篇 |
专业分类
电工技术 | 8602篇 |
技术理论 | 25篇 |
综合类 | 13579篇 |
化学工业 | 19145篇 |
金属工艺 | 8609篇 |
机械仪表 | 9853篇 |
建筑科学 | 21632篇 |
矿业工程 | 6047篇 |
能源动力 | 4203篇 |
轻工业 | 9605篇 |
水利工程 | 5687篇 |
石油天然气 | 5319篇 |
武器工业 | 966篇 |
无线电 | 9927篇 |
一般工业技术 | 11066篇 |
冶金工业 | 11431篇 |
原子能技术 | 1024篇 |
自动化技术 | 26596篇 |
出版年
2024年 | 436篇 |
2023年 | 1408篇 |
2022年 | 2673篇 |
2021年 | 3511篇 |
2020年 | 3981篇 |
2019年 | 2844篇 |
2018年 | 2585篇 |
2017年 | 3393篇 |
2016年 | 4247篇 |
2015年 | 4644篇 |
2014年 | 10914篇 |
2013年 | 9924篇 |
2012年 | 11278篇 |
2011年 | 12043篇 |
2010年 | 8955篇 |
2009年 | 9420篇 |
2008年 | 8757篇 |
2007年 | 11033篇 |
2006年 | 10181篇 |
2005年 | 8786篇 |
2004年 | 7614篇 |
2003年 | 6848篇 |
2002年 | 5667篇 |
2001年 | 4463篇 |
2000年 | 3688篇 |
1999年 | 3009篇 |
1998年 | 2221篇 |
1997年 | 1703篇 |
1996年 | 1499篇 |
1995年 | 1205篇 |
1994年 | 964篇 |
1993年 | 676篇 |
1992年 | 545篇 |
1991年 | 438篇 |
1990年 | 284篇 |
1989年 | 264篇 |
1988年 | 210篇 |
1987年 | 124篇 |
1986年 | 135篇 |
1985年 | 130篇 |
1984年 | 137篇 |
1983年 | 126篇 |
1982年 | 43篇 |
1981年 | 37篇 |
1980年 | 41篇 |
1979年 | 28篇 |
1977年 | 28篇 |
1961年 | 14篇 |
1959年 | 17篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Osama Y. Abudayyeh 《Advances in Engineering Software》1993,16(3):187-193
Effective management of construction projects depends on good access to and control of data, especially data pertaining to cost and schedule control functions. However, the proper design and development of automated mechanisms have not had the facility to acquire and store quality data in a timely manner. The purpose of this paper, then, is to discuss a prototype, automated data acquisition system that was developed to support an integrated project management system. The data acquisition system is composed of an integrated set of electronic forms used in conjunction with a bar coding data-entry tool. 相似文献
32.
W D Tiner 《International Journal of Project Management》1985,3(1):13-18
In order to control a project, construction management requires project information. This is obtained through accounting, estimating, cost management and scheduling functions which produce project reports. These reports are best obtained by subdividing the project into small parts. The ways in which each of these functions subdivides a project in order to produce its reports is discussed, together with a means of interrelating this information with a technique known as the work breakdown structure. 相似文献
33.
Yong Ma Yong‐zhen Peng Xiao‐lian Wang Shu‐ying Wang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(10):1118-1124
The laboratory scale anaerobic–anoxic–aerobic (A2O) process fed with synthetic brewage wastewater was designed to investigate the effects of changing feed C/P ratio on the performance of biological nutrient removal (BNR) processes. In the experiment, the influent chemical oxygen demand (COD) concentration was kept at approximately 300 mg L?1 while the total phosphorus concentration was varied to obtain the desired C/P ratio. Results showed that when the C/P ratio was lower than 32, phosphorus removal efficiency increased as C/P ratio increased linearly, while when the C/P ratio was higher than 32, the P removal efficiency was maintained at 90–98%, and effluent P concentration was lower than 0.5 mg L?1. However, regardless of the C/P ratio, excellent COD removal (90% or higher) and good total nitrogen removal (75–84%) were maintained throughout the experiments. It was also found that very good linear correlation was obtained between COD uptake per unit P released in the anaerobic zone and C/P ratio. In addition, the P content in the wasted activated sludge increased with the decrease in the C/P ratio. Based on the results, it was recommended that the wastewater C/P ratio and its effects be incorporated into BNR design and operational procedures, appropriate C/P ratios were used to achieve the effluent treatment goals. Copyright © 2005 Society of Chemical Industry 相似文献
34.
35.
所开发的压水堆核燃料循环分析计算机经济程序包括12个子程序,代表着压水堆整个核燃料循环各种不同的工艺过程。本程序能算出压水堆核电站核燃料循环中燃料费用对发电成本的影响,给出各工艺过程对燃料成本的敏感度分析,并尽可能给出燃料循环中燃料材料及服务的价格数据. 相似文献
36.
Waters in the Great Lakes basin contain more than 400 contaminant chemicals that potentially affect fishery resources, commerce, and human inhabitants. We determined in the laboratory the effects of selected contaminants on the toxicity of the widely used lampricides TFM (3-trifluoromethyl-4-nitrophenol) and Bayer 73 (2′,5-dichloro-4′-nitrosalicylanilide) to three species of fish—rainbow trout (Salmo gairdneri), white sucker (Catostomus commersoni), and fathead minnow (Pimephales promelas). The fish were exposed to paired mixtures of lampricides and selected contaminants in standardized, acute static toxicity tests to determine the resulting type of response—less than additive, additive, or greater than additive (synergistic). As expected, the toxicities of combinations of lampricides with organic pesticides, metal, industrial or municipal pollutants, and tannic acid were mostly additive. However, the toxicity of a combination of TFM, Delnav, and malathion was synergistic, and extremely small quantities of each chemical became lethal when mixed. The concentration that produced 50% mortality was 1.64 mg/L for TFM alone but only 0.041 mg/L for TFM with the pesticides. Toxicities of the pesticides in the combination also increased commensurately. The triple combination of chemicals produced extraordinary synergism and effectively demonstrated the hazards that may result if certain chemical combinations occur in the aquatic environment. However, synergism is not the only kind of toxic action that produces hazards to aquatic organisms. All three types of toxic action are of concern because toxic units produced by contaminant chemicals add to the toxic units of applied management chemicals. Since the toxicity of the majority of chemical combinations is simply additive, this cumulative toxic action contributes more total units to aquatic environments than the extreme actions of less than additive and synergism. The toxicity of the lampricide TFM, as well as other management chemicals, is reinforced by the presence of any contaminant that contributes additional units of toxicity. Therefore, all types of cumulative toxic action should be of concern to people and agencies involved with protecting the environment. 相似文献
37.
介绍了二次盐水及离子膜电解工序的主要设备和流程,对二次盐水及离子膜电解工序运行中出现的问题进行了分析,并提出了解决措施。 相似文献
38.
对中、美两国高校高水平运动队管理体制的探讨 总被引:15,自引:0,他引:15
彭中东 《武汉工业学院学报》2003,22(2):125-128
通过调查和查阅了大量的资料,对中、美两国的高校高水平运动队的管理体制进行了比较,旨在通过学习和借鉴将我国高校的高水平运动队管理体制不断的完善,提供一定的参考。 相似文献
39.
Argyris G. Kagiannas Thanassis Didis Dimitris Th. Askounis John Psarras 《国际能源研究杂志》2003,27(2):173-186
The needs that an energy supply system must meet are constantly changing, due to technological, social and political reasons. Effective energy planning is a dynamic process that is repeated periodically and adjusts to changing conditions. Energy decision makers and planners are no longer able to rely on inductive decision making since they have to investigate the effect of various decision parameters and possible future changes. To help in this process, models have been developed where estimates of future load growth, candidate power plants, fuels and other key factors can be introduced, from which the planners can evaluate decision parameters and the available alternatives. The paper presents the different methodologies and practices that are used by 11 energy models for energy demand forecasting, supply side management and generation expansion planning, demand side management and integrated resource planning. The paper concludes to the presentation of a strategic appraisal of the examined energy models appropriate for energy planning in Mozambique. Three models are proposed for conducting demand forecasting, generation expansion planning and demand side management. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
40.
Gülü Insel Derin Orhon Peter A Vanrolleghem 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):437-445
Hydrolysis mechanism plays a dominant role in the delicate balance of electron donor/electron acceptor ratios in BNR and EBPR systems as an important carbon source. In this study, the surface‐saturation‐type hydrolysis kinetics was investigated based on respirometric measurements, within the context of the theoretical and the practical identifiability of mathematical models. The identifiable parameters of a selected model were derived from respirograms. In addition, the information from the experiments was evaluated on the basis of Optimal Experimental Design (OED) methodology for different initial conditions of the batch respirometric experiment. © 2003 Society of Chemical Industry 相似文献