全文获取类型
收费全文 | 7862篇 |
免费 | 1085篇 |
国内免费 | 577篇 |
专业分类
电工技术 | 1144篇 |
综合类 | 617篇 |
化学工业 | 373篇 |
金属工艺 | 85篇 |
机械仪表 | 572篇 |
建筑科学 | 375篇 |
矿业工程 | 276篇 |
能源动力 | 97篇 |
轻工业 | 333篇 |
水利工程 | 138篇 |
石油天然气 | 173篇 |
武器工业 | 85篇 |
无线电 | 1346篇 |
一般工业技术 | 676篇 |
冶金工业 | 268篇 |
原子能技术 | 140篇 |
自动化技术 | 2826篇 |
出版年
2024年 | 16篇 |
2023年 | 180篇 |
2022年 | 168篇 |
2021年 | 225篇 |
2020年 | 415篇 |
2019年 | 355篇 |
2018年 | 260篇 |
2017年 | 286篇 |
2016年 | 356篇 |
2015年 | 342篇 |
2014年 | 485篇 |
2013年 | 574篇 |
2012年 | 589篇 |
2011年 | 576篇 |
2010年 | 448篇 |
2009年 | 444篇 |
2008年 | 451篇 |
2007年 | 526篇 |
2006年 | 456篇 |
2005年 | 401篇 |
2004年 | 316篇 |
2003年 | 272篇 |
2002年 | 231篇 |
2001年 | 192篇 |
2000年 | 166篇 |
1999年 | 132篇 |
1998年 | 98篇 |
1997年 | 89篇 |
1996年 | 69篇 |
1995年 | 70篇 |
1994年 | 48篇 |
1993年 | 54篇 |
1992年 | 38篇 |
1991年 | 29篇 |
1990年 | 30篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1976年 | 4篇 |
1959年 | 5篇 |
1958年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有9524条查询结果,搜索用时 156 毫秒
61.
62.
取样扰动引起土层剪切波速变化的试验研究 总被引:2,自引:0,他引:2
对3个工程场地土层的原位剪切波速和相同场地原状土样的室内剪切波速进行了比较试验,研究结果表明,随土性的不同,剪切波速的变化程度也不同。对于粘性土,两者测试结果一般相差在11%以内,个别相差达到13%左右:对于砂性土,室内测试结果一般偏小,相差在14%以内,最大相差达到20%。这些结果为依据室内剪切波速测试资料比较客观地评价原位土层剪切波速提供了客观依据,同时,也为评价取样过程对土样的扰动程度提供了一个定量的参考指标。 相似文献
63.
将从日本引进的新型土工静力一动力液压三轴扭转多功能剪切仪,配备了工业控制计算机和高精度模数转换接口板,以VC++6.0语言作为编程平台,利用现代计算机技术中的多线程编程技术和计算机绘图技术,实现三轴扭转试验仪的计算机数据采集处理系统,完成试验全过程的应力、应变和孔压等12种数据的实时监测、绘制实时动态曲线及实时数据采集处理,或形成数据文件供后期数据处理绘图。系统使用工控机内部高频时钟进行精确的系统采样定时,使试验仪采样周期的精确度达到微秒级,有效地保证数据采集精度改造后的试验仪数据采集处理系统不仅使试验数据的精确采集、处理过程全部自动化,且成功地完成对试验数据后续处理,如滞回圈等非规则曲线面积及莫尔圆公切线求解等一系列复杂计算。 相似文献
64.
The contribution from impurities in chlorine to levels of chlorinated organics found in potable water after chlorination was investigated. Techniques for sampling of chlorine and gas chromatography (GC) determination of chlorinated organics in chlorine are described. The detection limits were better than 1 ppm for each of chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, hexachloroethane, hexachloropropane and hexachlorobenzene in chlorine. With the exception of chloroform which occasionally accounted for nearly 1 μg l−1 in water, the levels of the nine compounds in chlorine accounted for less than 0.1 μg l−1 of each compound in chlorinated water from 10 Canadian treatment plants. The occurrence of these nine and 28 additional chlorinated organics previously detected in water supplies was determined by aid of liquid-liquid extraction of water samples. Seven compounds, including chloroform, carbon tetrachloride, trichloroethylene and tetrachloroethylene were detected, usually at levels ranging from 0.1 to 1 μg l−1 in chlorinated water from the treatment plant. 相似文献
65.
本文提出了基于整体承载极限状态的钢结构可靠度设计思路。这种思路建立在钢结构整体非线性分析和验算的基础上,并确保结构整体而非构件的可靠度水平,使结构整体的实际可靠度水平尽可能地接近于设计的目标值。本文针对门式钢刚架结构建立了一套实现这种设计的方法,包括结构整体非线性分析、结构体系可靠度计算以及实用的设计表达式。通过三个门式钢刚架结构设计实例比较了传统的构件设计方法,不考虑体系可靠度的整体承载极限状态设计方法和本文考虑体系可靠度的整体承载极限状态设计方法的设计结果,说明本文所提出设计思想的先进性。 相似文献
66.
The water authorities in England and Wales, which have now become water companies, recently had to provide anticipated costs for maintaining the water supply and sewerage systems over the next 20 years. Probabilistic models and statistical inference provide an opportunity to quantify the uncertainty in such exercises. Their use in a study undertaken by a water authority in the north-east of England is described and illustrated with interim data which were available at an early stage in the exercise. 相似文献
67.
混凝土结构火灾后的检测方法研究 总被引:11,自引:0,他引:11
本文通过对混凝土结构火灾后的火场温度确定分析以及不同方法检测火灾后混凝土的强度试验,系统地研究了混凝土结构在遭受火灾后的检测方法.提出了一些有效的检测手段。 相似文献
68.
69.
Organophosphate and phthalate esters in air and settled dust - a multi-location indoor study 总被引:1,自引:0,他引:1
This paper reports the abundance in indoor air and dust of eleven organophosphate esters and six phthalate esters. Both groups of these semi-volatile compounds are widely incorporated as additives into plastic materials used in the indoor environment, thus contributing to indoor exposure to industrial chemicals. Thirty sampling sites representing three different indoor environments (private homes, day care centers, and workplaces) in the Stockholm area, Sweden, were selected to obtain representative concentration profiles in both ambient air and settled dust. Eight of the target organophosphate esters and all six phthalate esters were found in both air and dust samples at all locations. The phthalate esters were more abundant than the organophosphate esters, typically ten times higher total concentrations. Especially interesting were the high levels of tributoxyethyl phosphate in the day care centers, the relatively high levels of chlorinated organophosphate esters in the air of workplaces and the overall high levels of diethylhexyl phthalate in dust. The air concentration profiles of the phosphate esters differed significantly between the three indoor environments, whereas the concentration profiles of the phthalate esters as well as their total concentrations were similar. The correlation between concentrations found in air and in dust was found to be weak. PRACTICAL IMPLICATIONS: Organophosphate esters and phthalate esters are commonly used as additives in numerous building materials and consumer products. The use of these compounds is increasing, and phosphate and phthalate esters are to be regarded as ubiquitous contaminants in the indoor environment. These compounds comprise a number of different compounds that have been associated with biologic effects in animal studies as well as in humans. Thus, it is of concern to increase the knowledge about human exposure of these compounds because of their presence in indoor air. In this paper, thirty indoor environments have been surveyed with respect to seventeen of the most abundant of these compounds. 相似文献
70.
设计了1个采样点/1km2、1个组合样/4km2,1个采样点/100~1000km2和1个采样点/1000~10000km23个层次的采样密度,系统研究了泛滥平原沉积物的超低密度采样代表性。运用统计学原理对泛滥平原沉积物中30~40余种元素进行正态母体显著性检验、t检验及对多元素总体的灰关联分析,表明用1个采样点/1000~10000km2的采样密度采集的泛滥平原沉积物具有代表性。因此建议在国际地球化学填图中用泛滥平原沉积物作为全球超低密度地球化学填图的采样介质。 相似文献