首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1328篇
  免费   59篇
  国内免费   5篇
电工技术   15篇
综合类   2篇
化学工业   369篇
金属工艺   19篇
机械仪表   35篇
建筑科学   63篇
矿业工程   2篇
能源动力   39篇
轻工业   145篇
水利工程   9篇
石油天然气   1篇
无线电   118篇
一般工业技术   194篇
冶金工业   70篇
原子能技术   11篇
自动化技术   300篇
  2023年   16篇
  2022年   47篇
  2021年   60篇
  2020年   24篇
  2019年   27篇
  2018年   33篇
  2017年   33篇
  2016年   58篇
  2015年   31篇
  2014年   42篇
  2013年   97篇
  2012年   82篇
  2011年   95篇
  2010年   68篇
  2009年   74篇
  2008年   61篇
  2007年   65篇
  2006年   62篇
  2005年   48篇
  2004年   48篇
  2003年   38篇
  2002年   36篇
  2001年   19篇
  2000年   17篇
  1999年   15篇
  1998年   26篇
  1997年   27篇
  1996年   13篇
  1995年   18篇
  1994年   18篇
  1993年   12篇
  1992年   10篇
  1991年   7篇
  1990年   6篇
  1989年   5篇
  1988年   8篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1984年   5篇
  1983年   9篇
  1982年   2篇
  1980年   2篇
  1979年   3篇
  1977年   2篇
  1976年   2篇
  1973年   2篇
  1970年   2篇
  1963年   1篇
  1903年   1篇
排序方式: 共有1392条查询结果,搜索用时 31 毫秒
51.
52.
National policies may have heterogeneous effects at the regional level. When coming to programmes aimed at increasing human capital, worker mobility from poorer to richer regions can reduce the benefits of the policy for the former areas. We focus on Italy and estimate the impact of education on the probability of migrating from a lagging area to a leading one. Endogeneity is addressed by exploiting an increase in the minimum school-leaving age in an instrumental variable framework. We find that one additional year of education increases the probability to migrate by 1.7 percentage points (9% of the average migration rate).  相似文献   
53.
Background: Autophagy is a highly conserved catabolic homeostatic process, crucial for cell survival. It has been shown that autophagy can modulate different cardiovascular pathologies, including vascular calcification (VCN). Objective: To assess how modulation of autophagy, either through induction or inhibition, affects vascular and valvular calcification and to determine the therapeutic applicability of inducing autophagy. Data sources: A systematic review of English language articles using MEDLINE/PubMed, Web of Science (WoS) and the Cochrane library. The search terms included autophagy, autolysosome, mitophagy, endoplasmic reticulum (ER)-phagy, lysosomal, calcification and calcinosis. Study characteristics: Thirty-seven articles were selected based on pre-defined eligibility criteria. Thirty-three studies (89%) studied vascular smooth muscle cell (VSMC) calcification of which 27 (82%) studies investigated autophagy and six (18%) studies lysosomal function in VCN. Four studies (11%) studied aortic valve calcification (AVCN). Thirty-four studies were published in the time period 2015–2020 (92%). Conclusion: There is compelling evidence that both autophagy and lysosomal function are critical regulators of VCN, which opens new perspectives for treatment strategies. However, there are still challenges to overcome, such as the development of more selective pharmacological agents and standardization of methods to measure autophagic flux.  相似文献   
54.
55.
This paper describes two novel algorithms based on the time-modulo reconstruction method intended for detection of the parametric faults in analogue-to-digital converters (ADC). In both algorithms, a pulse signal, in its slightly adapted form to allow sufficient time for converter settling, is taken as the test stimulus relieving the burden placed on the accuracy requirement of the excitation source. Instead of calculating the accurate conventional dynamic and static parameters, a signature result is obtained through the analysis of the output data in the time domain. The basic concept of the algorithms is the evaluation on the performance of ADCs by the comparison of the similarity of the output waveforms. The multi-site test is expensive for traditional specification-based tests of ADCs, as high quality analogue data generators are required. Based on these two algorithms, this paper proposes a solution for this problem. The objective of the test scheme is not to completely replace traditional specification-based tests, but to provide a reliable method for early identification of excessive parameter variations in production test that allows quickly discarding of most of the faulty circuits before performing a conventional test. The efficiency of the methods is validated on an industrial 12-bit pipelined ADC both in simulations and in measurements.  相似文献   
56.
In this paper, we sketch some of the challenges that should be addressed in future research efforts for model-based decision support in manufacturing and service networks. This includes integration issues, taking into account the autonomy of the decision-making entities in face of information asymmetry, the modeling of preferences of the decision-makers, efficiently determining robust solutions, i.e. solutions that are insensitive with respect to changes in the problem data, and a reduction of the time needed for model building and usage. The problem solution cycle includes problem analysis, the design of appropriate algorithms and their performance assessment. We are interested in a prototypical integration of the proposed methods within application systems, which can be followed up with field tests of the extended application systems. We argue that the described research agenda requires the interdisciplinary collaboration of business and information systems engineering researchers with colleagues from management science, computer science, and operations research. In addition, we present some exemplifying, illustrative examples of relevant research results.  相似文献   
57.
Bioceramics, such as silica-based glasses, are widely used in bone and teeth restoration. Nowadays, the association between nanotechnology and pharmacology is one of the most promising research fields in cancer therapy. The advanced processing methods and new chemical strategies allow the incorporation of drugs within them or on their functionalized surfaces. Bioceramics can act as local drug delivery systems to treat bone and teeth diseases. The present paper reports data related to the development of a pH-stimuli responsive bioactive glass. The glass conjugation with 5-aminofluorescein (5-AF), through a pH-sensitive organic spacer, allows to produce a pH-responsive bioactive biomaterial: when it is exposed to specific pH changes, it can favour the release of 5-AF directly at the target site. 5-AF has been chosen as a simple, low cost, non toxic model to simulate doxorubicin, an anticancer drug. As doxorubicin, 5-AF contains an amino group in its structure in order to form an amide bond with the carboxylic functionalities of the glass. Raman spectroscopy and thermal analysis confirm the glass conjugation of 5-AF by means of an amide bond; the amount of 5-AF loaded was very high (≈65 and 44 wt%). The release tests at two different pH (4.2 and 7.4) show that the amount of released 5-AF is higher at acid pH with respect to physiological one. This preliminary datum evidenced that a pH-sensitive drug delivery system has been developed. The low amount of 5-AF released (<1 wt% of the total 5-AF) is due to the very low solubility of 5-AF in aqueous medium. This disadvantage, may be overcome in a dynamic environment (physiological conditions), where it is possible to obtain a drug release system ensuring an effective therapeutic dose for long times and, at the same time, avoiding the drug toxicity.  相似文献   
58.
Direct metallization of plastics by high powerimpulse magnetron sputtering Even if polymers are today industrially used for decades the direct metallization of plastics is still a hot topic for research and development. Especially in light of the ban of hexavalent chromium an increasing demand for well‐adhering plastic metallization arises. High power impulse magnetron sputtering HIPIMS is a recent technology that can offer a high potential for successfully solving this challenge. This article focuses on the direct metallization of plastics by HIPIMS. In the frame of the investigations any pretreatment was ignored and the different polymers were directly under vacuum metallized. Compared to conventional mid‐frequency sputtering a significant improvement in adhesion was shown for different polymers. In detail the metallization of Plexiglas (PMMA) was investigated, since this polymer is highly challenging with respect to plasma processes. Due to the UV radiation damage of PMMA during plasma deposition direct metallization is usually not possible. Using ionized deposition it was possible to directly metallize the substrates with excellent adhering films without any interface layers or special pretreatments. The characterization of the substrate‐coating interface showed that for the well adhering films a cohesive fracture, i.e. a fracture within the polymer occurred.  相似文献   
59.
The concepts of both duality and fuzzy uncertainty in linear programming have been theoretically analyzed and comprehensively and practically applied in an abundance of cases. Consequently, their joint application is highly appealing for both scholars and practitioners. However, the literature contributions on duality in fuzzy linear programming (FLP) are neither complete nor consistent. For example, there are no consistent concepts of weak duality and strong duality. The contributions of this survey are (1) to provide the first comprehensive overview of literature results on duality in FLP, (2) to analyze these results in terms of research gaps in FLP duality theory, and (3) to show avenues for further research. We systematically analyze duality in fuzzy linear programming along potential fuzzifications of linear programs (fuzzy classes) and along fuzzy order operators. Our results show that research on FLP duality is fragmented along both dimensions; more specifically, duality approaches and related results vary in terms of homogeneity, completeness, consistency with crisp duality, and complexity. Fuzzy linear programming is still far away from a unifying theory as we know it from crisp linear programming. We suggest further research directions, including the suggestion of comprehensive duality theories for specific fuzzy classes while dispensing with restrictive mathematical assumptions, the development of consistent duality theories for specific fuzzy order operators, and the proposition of a unifying fuzzy duality theory.  相似文献   
60.
ABSTRACT

This paper explores the case of the historic harbour area of Naples, considered highly significant, due to its physical and cultural characteristics, with the aim of reflecting on the contemporary need for building renewed and synergic city–port relations in a sustainable perspective. Focusing on the physical and functional city–port integration, the study investigates Naples harbour planning policy between twentieth and twenty-first centuries in order to identify the limitations of older instruments and to exam the current proposal, finally suggesting perspectives for the future. The analysis highlights the fact that, in the port of Naples, with a landlord governance, the main obstacles to a more inclusive planning policy have been related to land use conflict between on one hand the public interest of the Port Authority and Municipality and the private interest of port operators on the other. In conclusion, the need for city–port plan integration is outlined as a central planning issue so as to combine the economic development of the harbour with social, cultural and ecological themes and to overcome the conflicts between the different actors involved in the complex planning process.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号