全文获取类型
收费全文 | 1388篇 |
免费 | 40篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 169篇 |
综合类 | 68篇 |
化学工业 | 100篇 |
金属工艺 | 14篇 |
机械仪表 | 36篇 |
建筑科学 | 158篇 |
矿业工程 | 26篇 |
能源动力 | 189篇 |
轻工业 | 50篇 |
水利工程 | 31篇 |
石油天然气 | 41篇 |
武器工业 | 2篇 |
无线电 | 33篇 |
一般工业技术 | 68篇 |
冶金工业 | 16篇 |
原子能技术 | 9篇 |
自动化技术 | 442篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 20篇 |
2021年 | 30篇 |
2020年 | 39篇 |
2019年 | 54篇 |
2018年 | 34篇 |
2017年 | 33篇 |
2016年 | 47篇 |
2015年 | 39篇 |
2014年 | 64篇 |
2013年 | 79篇 |
2012年 | 57篇 |
2011年 | 125篇 |
2010年 | 59篇 |
2009年 | 90篇 |
2008年 | 100篇 |
2007年 | 99篇 |
2006年 | 74篇 |
2005年 | 66篇 |
2004年 | 52篇 |
2003年 | 63篇 |
2002年 | 33篇 |
2001年 | 32篇 |
2000年 | 35篇 |
1999年 | 31篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有1452条查询结果,搜索用时 265 毫秒
1.
The topic of value creation through the recovery of returned products in closed loop supply chains is scattered across various bodies of literature. We undertake a systematic literature review of 144 articles in relevant green, reverse and closed loop supply chain literature to synchronize existing knowledge on value creation. Value manifestations of four types of value, namely economic, environmental, information and customer value, are identified. Value adding concepts from the forward- and reverse supply chain may leverage the process of value creation. They are classified into six subclasses, namely partnerships and collaboration, product design characteristics, service concepts, IT solutions, supply chain processes and organizational characteristics. We present a conceptual framework on a strategic level. In this way companies can create competitive advantages by closing the loop. The results of the literature analysis suggest avenues for future research on the operational and strategic level. 相似文献
2.
《Energy Policy》2015
In this paper we construct an indirect measure of the supply marginal cost function for the main generators from the observed bid data in the Italian electricity market in the period 2004–2007. We compute the residual demand function for each generator, taking explicitly into account the issue of transmission line congestion. This procedure allows recovering correct zonal Lerner index and the implied measure of the marginal cost function. We find evidence of a stable U-shaped marginal cost function for three main Italian generators, but a flat function for ENEL, the former national monopolist. The policy relevance of our approach lies in the possibility to offer some empirical knowledge of the marginal cost function of each generator to the regulator to design appropriate policy measures geared to the promotion of competitive market conditions. We propose a new market surveillance mechanism, which is based on the principle of sanctioning excessive deviations from the estimated measure of the marginal cost function presented in this work. 相似文献
3.
Setting baseline emissions is one of the principal tasks involved in awarding credits for greenhouse gas emission (GHG) mitigation projects under the Clean Development Mechanism (CDM). An emission baseline has to be project-specific in order to be accurate. However, project-specific baseline calculations are subject to high transaction costs, which disadvantage small-scale projects. For this reason, the CDM-Executive Board (CDM-EB) has approved simplified baseline methodologies for selected small-scale CDM project categories. While the simplified methods help reduce the transaction cost, they may also result in inaccuracies in the estimation of emission reductions from CDM projects. The purpose of this paper is to present a rigorous economic scheduling method for calculating the GHG emission reduction in a hypothetical competitive electricity industry due to the operation of a renewable energy-based power plant under CDM and compare the GHG emission reduction derived from the rigorous method with that obtained from the use of a simplified (i.e., standardized) method approved by the CDM-EB. A key finding of the paper is that depending upon the level of power demand, prices of electricity and input fuels, the simplified method can lead to either significant overestimation or substantial underestimation of emission reduction due to the operation of renewable energy-based power projects in a competitive electricity industry. 相似文献
4.
In this paper we design a dynamic dictionary for
the priced information model initiated by Charikar et al. Assume that a set S consisting of n elements is given such that
each element has an associated price, a positive real number. The cost of performing an operation on elements of S is a function
of their prices. The cost of an algorithm is the sum of the costs of
all operations it performs. The objective is to design algorithms
which incur low cost. In this model we propose a dynamic dictionary, supporting
search, insert and delete, for keys drawn from a linearly ordered set.
As an application we show that the dictionary can be used in
computing the trapezoidal map of a set of line segments, a fundamental problem in
computational geometry. 相似文献
5.
This article is based on experiences with data and text mining to gain information for strategic business decisions, using host-based analysis and visualisation (A/V), primarily in the field of patents. The potential advantages of host-based A/V are pointed out and the features of the first such A/V software, STN®AnaVist™, are described in detail. Areas covered include the user interfaces, initial set of documents for A/V, data mining, text mining, reporting, and suggestions for further development. 相似文献
6.
Neural Nets Successfully Solve Complex Fluid Flow Problem. Much research is being done in the area of neural networks, and industry is actively seeking successful application to real world problems. We describe here a successful application. We have used neural networks to model complex coolant flow patterns, such as those encountered in design of hypersonic aircraft. Previous calculation methods, while reasonably accurate, are iterative and extremely time consuming. Our new approach uses a hierarchical neural network architecture to model coolant flow distribution in multiple heat exchanger panels. This method is direct, fast, and accurate. 相似文献
7.
HLA-DRB1等位基因主要参与人类的抗原免疫功能,对其进行比较研究,有助于追溯人类的进化迁移史,开发类群特异性药物.本研究以Matlab为平台,用自组织竞争网络(Self-Organizing Competitive Neural Network),对世界54个民族和人群、14个HLA-DRB1等位基因,进行了无监督模式分类.结果表明,各民族之间存在差异性,同民族的各人群之间有相似性.西伯利亚各人群,澳洲各土著人群,黑人各人群,南美印第安各人群,犹太族各人群,日本各人群,及欧美白人各人群有相对独立性:南美印第安人与西伯利亚人有高度相似性;中国民族在南方人群和北方人群间存在较大差异;中国汉族中,广东汉族地位特殊,与少数民族如拉祜族、瑶族关系密切. 相似文献
8.
Tom Carter 《Urban Policy and Research》2005,23(3):265-286
Current demographic trends in Canada include population aging and declining household growth. These trends generally result in falling housing demand and stable or declining house prices. Housing markets in Canada's major cities, however, have been characterized by increases in demand and prices in recent years; due in large part to the influence of arriving immigrants. The destinations of 76 percent of international immigrants to Canada are the three global cities—Toronto, Vancouver and Montreal—where they have a very significant effect on housing demand, particularly as under current immigration policy many of those arriving come with considerable wealth. Their influence, however, is much broader and includes the growth of exclusive, prosperous immigrant neighbourhoods, new architectural designs and other neighbourhood changes. Not all immigrants, however, arrive with wealth. Many are poor, live in less attractive neighbourhoods and pay unrealistic amounts of their inadequate incomes for poor quality housing. Some end up homeless on the street. The role of immigrants in housing markets is an important consideration for urban and housing policy. 相似文献
9.
针对信息化时代企业情报工作面临的新课题,结合本企业情况,从成为企业技术创新的加油站、成为职工素质提高的资源库、成为企业获取和分析竞争环境的侦察兵、成为企业信息安全的保护伞等方面论述了企业情报工作与时俱进等理念和方法。 相似文献
10.
Young 《Algorithmica》2002,33(3):371-383
Abstract. Consider the following file caching problem: in response to a sequence of requests for files, where each file has a specified
size and retrieval cost , maintain a cache of files of total size at most some specified k so as to minimize the total retrieval cost. Specifically, when a requested file is not in the cache, bring it into the cache
and pay the retrieval cost, and remove other files from the cache so that the total size of files remaining in the cache is
at most k . This problem generalizes previous paging and caching problems by allowing objects of arbitrary size and cost, both important attributes when caching files for world-wide-web browsers, servers, and proxies.
We give a simple deterministic on-line algorithm that generalizes many well-known paging and weighted-caching strategies,
including least-recently-used, first-in-first-out, flush-when-full, and the balance algorithm. On any request sequence, the
total cost incurred by the algorithm is at most k/(k-h+1) times the minimum possible using a cache of size h ≤ k .
For any algorithm satisfying the latter bound, we show it is also the case that for most choices of k , the retrieval cost is either insignificant or at most a constant (independent of k ) times the optimum. This helps explain why competitive ratios of many on-line paging algorithms have been typically observed
to be constant in practice. 相似文献