全文获取类型
收费全文 | 2908篇 |
免费 | 367篇 |
国内免费 | 281篇 |
专业分类
电工技术 | 179篇 |
综合类 | 489篇 |
化学工业 | 233篇 |
金属工艺 | 84篇 |
机械仪表 | 160篇 |
建筑科学 | 367篇 |
矿业工程 | 129篇 |
能源动力 | 61篇 |
轻工业 | 153篇 |
水利工程 | 151篇 |
石油天然气 | 132篇 |
武器工业 | 26篇 |
无线电 | 265篇 |
一般工业技术 | 257篇 |
冶金工业 | 83篇 |
原子能技术 | 29篇 |
自动化技术 | 758篇 |
出版年
2024年 | 16篇 |
2023年 | 31篇 |
2022年 | 77篇 |
2021年 | 85篇 |
2020年 | 99篇 |
2019年 | 73篇 |
2018年 | 69篇 |
2017年 | 87篇 |
2016年 | 114篇 |
2015年 | 124篇 |
2014年 | 166篇 |
2013年 | 160篇 |
2012年 | 255篇 |
2011年 | 241篇 |
2010年 | 198篇 |
2009年 | 182篇 |
2008年 | 189篇 |
2007年 | 197篇 |
2006年 | 195篇 |
2005年 | 161篇 |
2004年 | 138篇 |
2003年 | 125篇 |
2002年 | 83篇 |
2001年 | 92篇 |
2000年 | 70篇 |
1999年 | 51篇 |
1998年 | 49篇 |
1997年 | 38篇 |
1996年 | 36篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1972年 | 2篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有3556条查询结果,搜索用时 0 毫秒
51.
根据大化水电站扩建工程枢纽布置的需要,引水渠右侧、接头土石坝坡脚处设置了一段圆弧型翼墙,因基础地质较差,采取了一系列工程处理措施,经过两年多时间的运行,证明上游翼墙设计合理、工程处理合适。 相似文献
52.
谷勤勤 《安徽工业大学学报》2012,(2):180-182
假设R是环,S是R的几乎优化扩张环。主要研究环R和环S上的Gorenstein同调维数的关系。首先,假设M是S模,证明MR是Gorenstein投射的充分必要条件为Ms是Gorenstein投射的。其次,证明了环R的左Gorenstein维数跟环S的左Gorenstein同调维数相等。 相似文献
53.
利用可拓集理论建立了基于区间值可拓集的员工绩效评价模型,并应用该模型进行了销售人员绩效评价实例分析。实例研究结果表明该模型通过关联度和等级特征值的计算,可以确定员工的绩效等级以及其在某个等级中的位置,能直观地反映员工绩效水平质与量的变化,而且该方法采用区间值对员工的绩效状态进行度量,反映的信息更加完整,另外采用这种方法不需要对数据进行标准化处理,减轻了计算难度。 相似文献
54.
55.
56.
本文研究了不确定离散系统的神经网络自适应控制器的设计。因为它不需要假设系统状态是可测的,一个观测器用来估计不可测状态。与现有离散系统的结果相比,该控制器具有较少的直接自适应参数。因此,可以很方便地实现工程算法。利用Lyapunov分析方法,所有的闭环系统的信号是保证最终有界(UUB),并且能够实现系统输出跟踪参考信号到有界紧集。一个仿真例子,验证了该方法的有效性。 相似文献
57.
23 highly hypnotizable undergraduates (Harvard Group Scale of Hypnotic Susceptibility) underwent 2 specially constructed 7-item hypnotic inductions. Over the 14 items, the main finding was of a relationship between E. R. Hilgard's (1973, 1977, 1979) "hidden observer" effect and 2 aspects of hypnotic age regression. Ss reporting a hidden observer experienced duality during regression to age 5, in which they were aware of being both adult and child. When asked to write a complex sentence, most did so, usually without spelling errors. The Ss not reporting this effect experienced quasi-lateral age regression in which they had the exclusive feeling of being 5 yrs old, with no sense of an adult identity. Most of these Ss were unable to write the same complex sentence when requested to during age regression. The study replicated Hilgard's finding of the hidden observer phenomenon in terms of its incidence and obtained similar verbal reports from Ss experiencing it. At the same time, the results suggest that a neodissociation account of hypnosis may need some modifications to accommodate these additional findings. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
58.
Chemical and Chromatic Bases for Preferential Visiting By the Cabbage Butterfly, Pieris rapae, to Rape Flowers 总被引:1,自引:2,他引:1
Scent and coloration of corolla were examined as floral attributes responsible for preferential visiting by the cabbage butterfly, Pieris rapae, to rape flower, Brassica rapa. Floral volatile components that release the flower-visiting behavior of the butterfly were identified by chemical analyses, electroantennography (EAG), and two behavioral bioassays: proboscis extension reflex (PER) in response to odor and attraction to artificial flowers. GC and GC-MS analyses of the headspace volatiles from the flowers revealed the presence of six aromatic compounds, benzaldehyde, phenylacetaldehyde, benzyl alcohol, 2-phenylethanol, phenylacetonitrile, and indole in decreasing order of quantity. Of these, phenylacetaldehyde elicited the highest response in the PER assay. While benzyl alcohol, 2-phenylethanol, benzaldehyde, and phenylacetonitrile evoked moderate responses, the PER-eliciting activity of indole was very weak. In two-choice behavioral bioassays, artificial flowers scented with any one of these PER-active compounds attracted significantly more butterflies than control (unscented) flowers, whereas those treated with indole were almost inactive. The EAG activities of the six chemicals were not high and were about the same at a low dose (1 g), but phenylacetaldehyde elicited a much stronger response from both sexes at higher doses (10 and 100 g). An overall profile of EAG responses at a dose of 100 g was analogous to that of PER performance, suggesting that floral volatiles may be involved in close-range location or recognition of flowers rather than long-range attraction. By spectroscopic and UV-photographic examinations of rape flower, the central part of the corolla was found to absorb UV rays in marked contrast to the other parts, which reflected near-UV rays (max = 350 nm). This indicates that the flower is endowed with a conspicuous nectar guide that is probably an important visual stimulus for attracting foraging adults of P. rapae. Consequently, the present findings strongly suggest that this elaborate pollination strategy of rape flower, characterized by its good combination of olfactory and visual attractiveness, accounts for preferential visiting by the cabbage butterfly to the flower. 相似文献
59.
从“八卦”一词在现代报刊杂志中产生的新义出发,认识到这是词义引申的结果,并从产生这种现象的原因出发,进一步分析现象后面深层次的原因,以求对这种现象有比较清楚的认识。 相似文献
60.
提出一种用于参数曲线自由变形的新的缩放因子,用该因子此去作用(缩放)待变形曲线,从而使曲线发生形变。通过交互改变控制参数,可达到预期的变形效果。实验表明,这种方法数学背景简单,易于控制,重复使用可获得丰富的变形效果,适用于几何造型、计算机动画等领域。 相似文献