全文获取类型
收费全文 | 1015篇 |
免费 | 111篇 |
国内免费 | 61篇 |
专业分类
电工技术 | 13篇 |
综合类 | 57篇 |
化学工业 | 38篇 |
金属工艺 | 43篇 |
机械仪表 | 53篇 |
建筑科学 | 38篇 |
矿业工程 | 36篇 |
能源动力 | 21篇 |
轻工业 | 18篇 |
水利工程 | 58篇 |
石油天然气 | 470篇 |
武器工业 | 10篇 |
无线电 | 23篇 |
一般工业技术 | 61篇 |
冶金工业 | 22篇 |
原子能技术 | 19篇 |
自动化技术 | 207篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 33篇 |
2021年 | 35篇 |
2020年 | 43篇 |
2019年 | 38篇 |
2018年 | 42篇 |
2017年 | 41篇 |
2016年 | 28篇 |
2015年 | 44篇 |
2014年 | 58篇 |
2013年 | 63篇 |
2012年 | 81篇 |
2011年 | 85篇 |
2010年 | 69篇 |
2009年 | 52篇 |
2008年 | 45篇 |
2007年 | 53篇 |
2006年 | 47篇 |
2005年 | 50篇 |
2004年 | 34篇 |
2003年 | 31篇 |
2002年 | 32篇 |
2001年 | 20篇 |
2000年 | 26篇 |
1999年 | 15篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1987年 | 8篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有1187条查询结果,搜索用时 0 毫秒
1.
2.
An adaptable die is one that not only produces the correct geometrical shape, but also is designed through an adaptable method to impart other desirable properties to the product or process. In this first part of a series of papers, six kinematically admissible velocity fields are developed for use in upper bound models for axisymmetric extrusion through various dies, including extrusion through adaptable dies. Three base velocity fields are presented:
- (1) assuming proportional angles in the deformation zone,
- (2) assuming proportional areas in the deformation zone, or
- (3) assuming proportional distances from the centerline in the deformation zone.
3.
四川盆地中部上三叠统香溪群岩性油气藏圈闭类型及其特征 总被引:4,自引:0,他引:4
四川盆地川中地区构造平缓,大型断裂欠发育,已发现的油气藏与背斜关系并不十分密切。研究认为,川中地区香溪群主要发育岩性圈闭,根据圈闭形成主控因素,结合香溪群沉积前的古地貌特征和裂缝发育特点,将川中香溪群岩性圈闭划分为4种类型:①与地层尖灭相关的地层—岩性圈闭;②与沉积—成岩相变密切相关的成岩—岩性圈闭;③与古地貌有关的差异压实作用形成的岩性圈闭;④与断层转化调节相关的裂缝—岩性复合圈闭。其中成岩—岩性圈闭和地层—岩性圈闭,是川中香溪群最重要的、分布最广泛的圈闭类型。 相似文献
4.
万里飘 《电网与水力发电进展》2003,19(2):28-30
介绍了江苏沙河抽水蓄能电站上进出水口设计特点,上进水口体型参数的确定,工程处理措施,结构稳定分析和结构计算。 相似文献
5.
Benchmarking Fluvial Dynamics for Process‐Based River Restoration: the Upper Rhine River (1816–2014) 下载免费PDF全文
Multi‐temporal analysis of river‐floodplain processes is a key tool for the identification of reference conditions or benchmarks and for the evaluation of deviations or deficits as a basis for process‐based river restoration in large modified rivers. This study developed a methodology for benchmarking fluvial processes at river segment level, focusing on those interrelations between morphodynamics (aggradation, erosion, channel shift) and vegetation succession (initial, colonization, transition) that condition habitat structure. Habitat maps of the free‐flowing Upper Rhine River downstream from Iffezheim dam (France–Germany border) were intersected with a geographic information system‐based approach. Patches showing trajectories of anthropization, changeless, progression and regression allowed for the identification of natural and human‐induced processes over almost 200 years. Before channelization, the riverine system was characterized by a shifting habitat mosaic with natural heterogeneity, high degree of surface water connectivity and equilibrium between progression and regression processes. On the other hand, the following 175 years of human interventions led to severe biogeomorphologic deficits evidenced by loss of natural processes and habitat heterogeneity, hydrological disconnection between the river and its floodplain and imbalance of progression versus regression dynamics. The main driving forces of change are found in hydromorphological impacts (channelization, regulation and hydropower plant construction). Regression processes are now almost absent and have to be the objective of process‐based river restoration measures for the studied river‐floodplain system. A sustainable view on water management and river restoration should aim at a more resilient riverine system by balancing the recovery of natural processes with societal needs. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
6.
罗渝 《四川大学学报(工程科学版)》2010,42(Z1):93-99
对于一些性质复杂,滑坡推力巨大的边(滑)坡,单一的抗滑结构对其整治已显得无能为力,于是各种组合抗滑结构应运而生,然而目前对采用组合防治结构加固边坡稳定性的研究又十分稀缺。因此,本文以桩锚组合结构加固边坡为例,运用极限分析上限定理,推导出了地震作用下桩锚组合结构加固边坡中抗滑桩所需提供抗力的计算公式以及该加固边坡的屈服加速度计算公式,并提出了永久位移的预测方法,为地震带边坡防治结构的设计提供理论依据。通过对桩锚组合结构加固的实例边坡的计算分析,得到了在确定的锚索布置条件下,抗滑桩所需提供抗力和边坡屈服加速度与地震系数、抗滑桩布置位置、边坡特性和坡体材料特性等因素相关关系的一系列研究结果,揭示了地震作用下桩锚组合结构加固边坡的稳定性。 相似文献
7.
In this paper, we introduce a single-machine scheduling problem with an exponentially time-dependent learning effect. The processing time of a job is assumed to be an exponential function of the total normal processing time of jobs already processed before it. For such a scheduling problem, we first provide the upper bound for the maximum lateness and for the total weighted completion time. Next, we show that problems with the following criteria: makespan, the total completion time, the total weighted completion time, the total earliness/tardiness penalties and the maximum lateness under some agreeable conditions, are polynomially solvable. 相似文献
8.
Fuzzy utility mining has been an emerging research issue because of its simplicity and comprehensibility. Different from traditional fuzzy data mining, fuzzy utility mining considers not only quantities of items in transactions but also their profits for deriving high fuzzy utility itemsets. In this paper, we introduce a new fuzzy utility measure with the fuzzy minimum operator to evaluate the fuzzy utilities of itemsets. Besides, an effective fuzzy utility upper-bound model based on the proposed measure is designed to provide the downward-closure property in fuzzy sets, thus reducing the search space of finding high fuzzy utility itemsets. A two-phase fuzzy utility mining algorithm, named TPFU, is also proposed and described for solving the problem of fuzzy utility mining. At last, the experimental results on both synthetic and real datasets show that the proposed algorithm has good performance. 相似文献
9.
知识的属性扰动引起知识规律的变化,这些变化的规律称为扰动规律.利用单向S-粗集和单向S-粗集对偶,给出属性扰动的知识规律的上规律.下规律的概念,并对知识规律与属性扰动的知识规律进行了讨论,提出了属性扰动知识规律(上规律,下规律)的不等式定理. 相似文献
10.
Six different methods to calculate the Strain Index (SI) scores for jobs with multiple forces/tasks were developed. Exposure data of 733 subjects from 12 different worksites were used to calculate these SI scores. Results show that using different SI computation methods could result in different SI scores, hence different risk level classifications. However, some simpler methods generated SI scores were comparable to the more complicated composite SI method. Despite differences in the scores between the six different SI computation methods, Spearman rank-order correlation coefficients of 0.61-0.97 were found between the methods. With some confidence, ergonomic practitioners may use simpler methods, depending on their specificity requirement in job evaluations and available resources. Some SI computation methods may tend to over-estimate job risk levels, while others may tend to under-estimate job risk levels, due to different ways used in obtaining the various SI parameters and computations. 相似文献