全文获取类型
收费全文 | 2376篇 |
免费 | 34篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 46篇 |
化学工业 | 409篇 |
金属工艺 | 83篇 |
机械仪表 | 70篇 |
建筑科学 | 140篇 |
矿业工程 | 6篇 |
能源动力 | 61篇 |
轻工业 | 299篇 |
水利工程 | 20篇 |
石油天然气 | 3篇 |
无线电 | 159篇 |
一般工业技术 | 577篇 |
冶金工业 | 212篇 |
原子能技术 | 72篇 |
自动化技术 | 260篇 |
出版年
2019年 | 15篇 |
2018年 | 25篇 |
2017年 | 19篇 |
2016年 | 31篇 |
2015年 | 30篇 |
2014年 | 37篇 |
2013年 | 97篇 |
2012年 | 53篇 |
2011年 | 76篇 |
2010年 | 71篇 |
2009年 | 64篇 |
2008年 | 65篇 |
2007年 | 83篇 |
2006年 | 72篇 |
2005年 | 67篇 |
2004年 | 58篇 |
2003年 | 71篇 |
2002年 | 90篇 |
2001年 | 77篇 |
2000年 | 63篇 |
1999年 | 81篇 |
1998年 | 122篇 |
1997年 | 80篇 |
1996年 | 67篇 |
1995年 | 55篇 |
1994年 | 44篇 |
1993年 | 36篇 |
1992年 | 22篇 |
1991年 | 33篇 |
1990年 | 35篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 30篇 |
1984年 | 31篇 |
1983年 | 20篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 31篇 |
1979年 | 27篇 |
1978年 | 26篇 |
1977年 | 19篇 |
1976年 | 35篇 |
1975年 | 20篇 |
1974年 | 17篇 |
1973年 | 12篇 |
1972年 | 17篇 |
1967年 | 16篇 |
1939年 | 12篇 |
排序方式: 共有2417条查询结果,搜索用时 0 毫秒
31.
This work presents a method for efficiently simplifying the pressure projection step in a liquid simulation. We first devise a straightforward dimension reduction technique that dramatically reduces the cost of solving the pressure projection. Next, we introduce a novel change of basis that satisfies free‐surface boundary conditions exactly, regardless of the accuracy of the pressure solve. When combined, these ideas greatly reduce the computational complexity of the pressure solve without compromising free surface boundary conditions at the highest level of detail. Our techniques are easy to parallelize, and they effectively eliminate the computational bottleneck for large liquid simulations. 相似文献
32.
Conventionally drought severity is assessed based on drought indices. Recently the Reconnaissance Drought Index (RDI) was
proposed to assess drought severity based on the precipitation to potential evapotranspiration ratio (P/PET). In this paper
RDI is studied as a bivariate index under a set of assumptions and simplifications. The paper presents a simple computational
procedure for estimating the P/PET ratio for selected reference periods varying from 3 to 12 months, for any return period
of drought. Alternatively, based on this procedure, the severity of any drought episode is rationally assessed. A bivariate
probability analysis is employed based on the assumption that P and PET values are normally distributed and often negatively
correlated. Examples for the application of the proposed procedure are presented using data from several meteorological stations
in Greece. It is shown that the assumption of normality of both P and PET holds for long periods at all examined stations. 相似文献
33.
A.?Konstantinidis Th.?TsiatsosEmail author A.?Pomportsis 《Multimedia Tools and Applications》2009,44(2):279-304
E-learning systems have gone through a radical change from the initial text-based environments to more stimulating multimedia
systems. Such systems are Collaborative Virtual Environments, which could be used in order to support collaborative e-learning
scenarios. The main aim of this paper is to aid educational designers in selecting, designing and evaluating three dimensional
collaborative virtual environments in order to gain the pedagogical benefits of Computer Supported Collaborative Learning.
Therefore, this paper initially discusses the potential of three dimensional networked virtual environments for supporting
collaborative learning. Furthermore, based on a two-step platform selection process this paper (a) presents and compares three
dimensional multi-user virtual environments for supporting collaborative learning and (b) validates the most promising solution
against a set of design principles for educational virtual environments. According to these principles, an educational environment
has been implemented on top of the selected platform in order to support collaborative e-learning scenarios. The design of
this environment is also presented. In addition, this paper presents the results of three small scale studies carried out
in a tertiary education department, to assess the educational environment. This environment has been evaluated based on a
hybrid evaluation methodology for uncovering usability problems, collecting further requirements for additional functionality
to support collaborative virtual learning environments, and determining the appropriateness of different kinds of learning
scenarios.
相似文献
A. PomportsisEmail: |
34.
We propose a new fluid control technique that uses scale-dependent force control to preserve small-scale fluid detail. Control particles define local force fields and can be generated automatically from either a physical simulation or a sequence of target shapes. We use a multi-scale decomposition of the velocity field and apply control forces only to the coarse-scale components of the flow. Small-scale detail is thus preserved in a natural way avoiding the artificial viscosity often introduced by force-based control methods. We demonstrate the effectiveness of our method for both Lagrangian and Eulerian fluid simulation environments. 相似文献
35.
This study examines the effect of training procedures, as measured by the results of a test, on the level of assimilation of a new safety programme in 80 Quebec companies. The Workplace Hazardous Materials Information System (WHMIS) was introduced in the province in 1989. The bipartite safety association representing the manufacturers of transportation equipment and machinery offered two types of WHMIS training services to their members: (a) 4 h employee training courses, and (b) two-day trainer training courses. Companies were free to choose from these and other services to comply with the WHMIS training requirements. A test was issued to a stratified sample of 862 employees approximately one year after the training. On average, the scores were best in plants having employees trained directly by experts from the safety association (type a). The training of internal trainers for companies produced slightly inferior learning results (type b). 相似文献
36.
Denis Thérien 《Computational Complexity》1994,4(4):383-388
Algebraic techniques are used to prove that any circuit constructed with MOD
q
gates that computes the AND function must use (n) gates at the first level. The best bound previously known to be valid for arbitraryq was (logn). 相似文献
37.
Card-based systems are simple, effective means of controlling production. Yet most systems concentrate on controlling the shop floor. They neglect other planning tasks, like estimating short, feasible due dates during customer enquiry management. A card-based version of the workload control concept for job shops – COBACABANA (COntrol of BAlance by CArd-BAsed Navigation) – was proposed in the literature to overcome this shortcoming. COBACABANA uses cards for due date setting and order release, making it a potentially important solution for small shops with limited resources. But many such firms operate as flow shops rather than job shops. Research demonstrated that COBACABANA’s release mechanism must be adapted if applied to a pure flow shop, but its approach to due date setting has not been evaluated in such an environment. We show COBACABANA has the potential to improve pure flow shop performance, but its due date setting procedure should be adapted compared to job shops. In a flow shop, due date estimation can also be further simplified by considering the load awaiting release to the first (gateway) station only while maintaining most performance benefits. The results are important for all card-based systems that aim to stabilise work-in-process, including kanban and ConWIP (Constant Work-in-Process). 相似文献
38.
One of the key functions of Workload Control is order release. Jobs are not released immediately onto the shop floor – they are withheld and selectively released to create a mix of jobs that keeps work-in-process within limits and meet due dates. A recent implementation of Workload Control’s release method highlighted an important issue thus far overlooked by research: How to accommodate re-entrant flows, whereby a station is visited multiple times by the same job? We present the first study to compare the performance of Workload Control both with and without re-entrant flows. Simulation results from a job shop model highlight two important aspects: (i) re-entrant flows increase variability in the work arriving at a station, leading to a direct detrimental effect on performance; (ii) re-entrant flows affect the release decision-making process since the load contribution of all visits by a job to a station has to fit within the norm. Both aspects have implications for practice and our interpretation of previous research since: (i) parameters given for work arriving may significantly differ from those realised; (ii) increased workload contributions at release mean that prior simulations may have been unstable, leading to some jobs never being released. 相似文献
39.
Gian Luigi Angrisani Piriya Taptimthong Susanne Elisabeth Thürer Christian Klose Hans Jürgen Maier Marc Christopher Wurz Kai Möhwald 《Advanced Engineering Materials》2018,20(9)
40.
Electrochemical Behavior of Single CuO Nanoparticles: Implications for the Assessment of their Environmental Fate 下载免费PDF全文
Giorgia Zampardi Jorg Thöming Hendrik Naatz Hatem M. A. Amin Suman Pokhrel Lutz Mädler Richard G. Compton 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(32)
The electrochemical behavior of copper oxide nanoparticles is investigated at both the single particle and at the ensemble level in neutral aqueous solutions through the electrode‐particle collision method and cyclic voltammetry, respectively. The influence of Cl? and NO3? anions on the electrochemical processes occurring at the nanoparticles is further evaluated. The electroactivity of CuO nanoparticles is found to differ between the two types of experiments. At the single‐particle scale, the reduction of the CuO nanoparticles proceeds to a higher extent in the presence of chloride ion than of nitrate ion containing solutions. However, at the multiparticle scale the CuO reduction proceeds to the same extent regardless of the type of anions present in solution. The implications for assessing realistically the environmental fate and therefore the toxicity of metal‐based nanoparticles in general, and copper‐based nanoparticles in particular, are discussed. 相似文献