全文获取类型
收费全文 | 15662篇 |
免费 | 1343篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 89篇 |
综合类 | 10篇 |
化学工业 | 6361篇 |
金属工艺 | 174篇 |
机械仪表 | 346篇 |
建筑科学 | 536篇 |
矿业工程 | 23篇 |
能源动力 | 392篇 |
轻工业 | 3776篇 |
水利工程 | 126篇 |
石油天然气 | 85篇 |
无线电 | 592篇 |
一般工业技术 | 2180篇 |
冶金工业 | 677篇 |
原子能技术 | 46篇 |
自动化技术 | 1602篇 |
出版年
2024年 | 46篇 |
2023年 | 243篇 |
2022年 | 1227篇 |
2021年 | 1301篇 |
2020年 | 525篇 |
2019年 | 534篇 |
2018年 | 599篇 |
2017年 | 634篇 |
2016年 | 671篇 |
2015年 | 536篇 |
2014年 | 717篇 |
2013年 | 1059篇 |
2012年 | 1040篇 |
2011年 | 1159篇 |
2010年 | 868篇 |
2009年 | 828篇 |
2008年 | 764篇 |
2007年 | 708篇 |
2006年 | 546篇 |
2005年 | 420篇 |
2004年 | 353篇 |
2003年 | 310篇 |
2002年 | 287篇 |
2001年 | 167篇 |
2000年 | 118篇 |
1999年 | 158篇 |
1998年 | 141篇 |
1997年 | 132篇 |
1996年 | 124篇 |
1995年 | 88篇 |
1994年 | 66篇 |
1993年 | 68篇 |
1992年 | 66篇 |
1991年 | 51篇 |
1990年 | 39篇 |
1989年 | 37篇 |
1988年 | 34篇 |
1987年 | 34篇 |
1986年 | 43篇 |
1985年 | 37篇 |
1984年 | 31篇 |
1983年 | 27篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 20篇 |
1979年 | 25篇 |
1978年 | 20篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
将Al-5Mg-0.18Mn-0.2Sc-0.08Zr-0.01Fe-0.01Si(质量分数,%)合金铸锭进行多向等温锻造(应变12)或等径角挤压(应变10,325℃),再进行热轧(325℃)和冷轧(20℃),对比研究合金变形后的组织和力学行为.结果表明,对(亚)晶粒尺寸dUFG=2μm的超细晶组织合金进行多向等温锻造... 相似文献
992.
993.
Alessandro Grandini Daniela Summa Stefania Costa Raissa Buzzi Elena Tamburini Gianni Sacchetti Alessandra Guerrini 《International journal of molecular sciences》2022,23(8)
Phytopathogenic fungi are among the main causes of productivity losses in agriculture. To date, synthetic chemical pesticides, such as hydroxyanilides, anilinopyrimidines and azole derivatives, represent the main treatment tools for crop plant defence. However, the large and uncontrolled use of these substances has evidenced several side effects, namely the resistance to treatments, environmental damage and human health risks. The general trend is to replace chemicals with natural molecules in order to reduce these side effects. Moreover, the valorisation of agri-food industry by-products through biotransformation processes represents a sustainable alternative to chemical synthesis in several sectors. This research is aimed at comparing the anti-phytopathogenic activity of waste bovine and porcine bile with secosteroids obtained by biotransformation of bile acids with Rhodococcus strains. The ultimate goal is to apply these natural products on food crops affected by phytopathogenic fungi. 相似文献
994.
Clemente Neves Sousa Paulo Teles Vanessa Filipa Ferreira Dias João Luís Alves Apóstolo Maria Henriqueta Jesus Silva Figueiredo Maria Manuela Martins 《Hemodialysis international. International Symposium on Home Hemodialysis》2014,18(3):695-699
Vascular access is one of the leading causes of mobilization of financial resources in health systems for people with chronic kidney disease on hemodialysis. Physical examination of the arteriovenous fistula (AVF) has demonstrated its effectiveness in identifying complications. We decided to evaluate the influence of nurses' professional experience in the detection of complications of the AVF (venous stenosis and steal syndrome). The study took place in eight hemodialysis centers between May and September of 2011 in the north of Portugal. Sample was constituted by registered nurses. The nurses involved in the experiment were divided in two groups: those who had more than 5 years of experience and those who had less than 5 years of experience. Ninety‐two nurses participated in the study: 34 nurses had less than 5 years of professional experience and 58 had more than 5 years of professional experience. In the practices considered by nurses in the detection of venous stenosis, there were no differences observed between the groups (P > 0.05). In steal syndrome, there were no differences observed between the groups in the practices of the nurses in the detection of this complication of the AVF (P > 0.05). We concluded that professional experience does not influence the detection of venous stenosis and steal syndrome. 相似文献
995.
Pineapple Wines Obtained from Saccharification of Its Waste with Three Strains of Saccharomyces cerevisiae
下载免费PDF全文
![点击此处可从《Journal of Food Processing and Preservation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
996.
The Water Framework Directive (WFD) defines common objectives for water resources throughout the European Union (EU). Given this general approach to water preservation and water policy, the objective of this paper is to analyse whether common patterns of water consumption exist within Europe. In particular, our study uses two methods to reveal the reasons behind sectoral water use in all EU countries. The first method is based on an accounting indicator that calculates the water intensity of an economy as the sum of sectoral water intensities. The second method is a subsystem input-output model that divides total water use into different income channels within the production system. The application uses data for the years 2005 and 2009 on water consumption in the production system of the 27 countries of the EU. From our analysis it emerges that EU countries are characterized by very different patterns of water consumption. In particular water consumption by the agriculture sector is extremely high in Central/Eastern Europe, relative to the rest of Europe. In most countries, the water used by the fuel, power and water sector is consumed to satisfy domestic final demand. However, our analysis shows that for some countries exports from this sector are an important driver of water consumption. Focusing on the agricultural sector, the decomposition analysis suggests that water usage in Mediterranean countries is mainly driven by final demand for, and exports of, agricultural products. In Central/Eastern Europe domestic final demand is the main driver of water consumption, but in this region the proportion of water use driven by demand for exports is increasing over time. Given these heterogeneous water consumption patterns, our analysis suggests that Mediterranean and Central/Eastern European countries should adopt specific water policies in order to achieve efficient levels of water consumption in the European Union. 相似文献
997.
Boris F. Belokopytov Kestutis S. Laurinavichius Tatyana V. Laurinavichene Maria L. Ghirardi Michael Seibert Anatoly A. Tsygankov 《International Journal of Hydrogen Energy》2009
Eight natural microbial consortia collected from different sites were tested for dark, hydrogen production during starch degradation. The most active consortium was from silo pit liquid under mesophilic (37 °C) conditions. The fermentation medium for this consortium was optimized (Fe, NH4+, phosphates, peptone, and starch content) for both dark fermentation and for subsequent purple photosynthetic bacterial H2 photoproduction [Laurinavichene TV, Tekucheva DN, Laurinavichius KS, Ghirardi ML, Seibert M, Tsygankov AA. Towards the integration of dark and photo fermentative waste treatment. 1. Hydrogen photoproduction by purple bacterium Rhodobacter capsulatus using potential products of starch fermentation. Int J Hydrogen Energy 2008;33(23):7020–26], in the presence of the spent dark, fermentation effluent. The addition of Zn (10 mg L−1), as a methanogenesis inhibitor that does not inhibit purple bacteria at this concentration, also did not inhibit dark, fermentative H2 production. The influence of various fermentation end products at different concentrations (up to 30 g L−1) on dark, H2 production was also examined. Added lactate stimulated, but added isobutyrate and butanol strongly inhibited gas production. Under optimal conditions the fermentation of starch (30 g L−1) resulted in 5.7 L H2 L−1 of culture (1.6 mol H2 per mole of hexose) with the co-production mainly of butyrate and acetate. 相似文献
998.
Maria Albareda-Sambola Elena Fernández Gilbert Laporte 《Computers & Operations Research》2009,36(2):597-611
This article introduces a new problem called the Capacity and Distance Constrained Plant Location Problem. It is an extension of the discrete capacitated plant location problem, where the customers assigned to each plant have to be packed in groups that will be served by one vehicle each. The constraints include two types of capacity. On the one hand plants are capacitated, and the demands of the customers are indivisible. On the other hand, the total distance traveled by each vehicle to serve its assigned customers in round trips plant–customer–plant is also limited. The paper addresses different modeling aspects of the problem. It describes a tabu search algorithm for its solution. Extensive computational tests indicate that the proposed heuristic consistently yields optimal or near-optimal solutions. 相似文献
999.
Francisco Collazo-Reyes Maria Elena Luna-Morales Evelia Luna-Morales 《Scientometrics》2017,110(2):695-709
This study addresses an early case of an association between a local journal and a commercial publisher in Latin America striving to improve quality. The two journals examined are Archivos de Investigación Médica (AIM), 1970–1991 and its continuation as Archives of Medical Research (AMR), 1992–2014. The aim is to characterize and compare the publishing policies and patterns of scientific communication and bibliometric indicators developed under the two different types of publication: AIM as a source of local dissemination and the commercially circulated AMR. Publishing policies, production, and citations were identified in accordance with coverage by the Web of Science and Scopus indexes. The papers and citations were grouped into three categories according to the author´s affiliation: local, regional, and external. This categorization resulted in different combinations of correlations between cited and citing papers, in addition to a distribution of collaborative production and citations by country organized by continent. The comparison of results reveals two successful publishing projects; however, editorial practices pose an irreconcilable situation between the AIM objectives as a regional journal and AMR objectives as a mainstream journal, according with dominant indicators of international competition. Some implications of this situation are discussed in the context of Latin American and Caribbean journals. 相似文献
1000.
Multi‐criteria algorithm‐based methodology used to select suitable domes for compressed air energy storage
下载免费PDF全文
![点击此处可从《国际能源研究杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Storing energy allows both the efficiency and availability of renewable energy to be increased, thus dissociating actual from expected generation and from consumption demands. Compressed air energy storage (hereinafter ‘CAES’) enables the efficient and cost‐effective storage of large amounts of energy, achieving a capacity of over 100 MWh. There are several geological structures that can be used as CAES, among which the use and construction of salt domes are particularly noteworthy. However, there is a high exploration risk associated with subsurface exploration. To this end, it is advisable to establish a detailed schedule to select and characterize structures, with the purpose of minimizing the aforementioned risk. Multi‐criteria algorithms can be used to establish a hierarchy of the alternatives and to identify the structures with the greatest potential with an objective approach. The analytic hierarchy process method is used in this paper as the selection algorithm, which is based on identifying and assessing criteria and weighting each criterion. In accordance with the analytic hierarchy process method, the goal was divided into a series of different level criteria, defining a breakdown structure of the problem to select salt domes. This paper defines a structure hierarchization method that allows the objective establishment of the areas with the highest potential for CAES, considering both technical and socioeconomic factors. Therefore, a supporting decision‐making method may be established to reduce the exploration risk associated with underground structures. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献