全文获取类型
收费全文 | 3476篇 |
免费 | 268篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 48篇 |
综合类 | 3篇 |
化学工业 | 1056篇 |
金属工艺 | 44篇 |
机械仪表 | 80篇 |
建筑科学 | 127篇 |
矿业工程 | 3篇 |
能源动力 | 118篇 |
轻工业 | 425篇 |
水利工程 | 19篇 |
石油天然气 | 1篇 |
无线电 | 364篇 |
一般工业技术 | 651篇 |
冶金工业 | 111篇 |
原子能技术 | 43篇 |
自动化技术 | 655篇 |
出版年
2024年 | 5篇 |
2023年 | 35篇 |
2022年 | 165篇 |
2021年 | 266篇 |
2020年 | 113篇 |
2019年 | 103篇 |
2018年 | 128篇 |
2017年 | 128篇 |
2016年 | 160篇 |
2015年 | 142篇 |
2014年 | 151篇 |
2013年 | 239篇 |
2012年 | 223篇 |
2011年 | 276篇 |
2010年 | 202篇 |
2009年 | 202篇 |
2008年 | 177篇 |
2007年 | 157篇 |
2006年 | 143篇 |
2005年 | 109篇 |
2004年 | 90篇 |
2003年 | 74篇 |
2002年 | 55篇 |
2001年 | 41篇 |
2000年 | 36篇 |
1999年 | 39篇 |
1998年 | 40篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 14篇 |
1994年 | 25篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 17篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有3748条查询结果,搜索用时 171 毫秒
131.
132.
Elisabetta Albi Giuseppina Perrella Andrea Lazzarini Samuela Cataldi Remo Lazzarini Alessandro Floridi Francesco Saverio Ambesi-Impiombato Francesco Curcio 《International journal of molecular sciences》2014,15(7):11555-11565
Proliferating thyroid cells are more sensitive to UV-C radiations than quiescent cells. The effect is mediated by nuclear phosphatidylcholine and sphingomyelin metabolism. It was demonstrated that proton beams arrest cell growth and stimulate apoptosis but until now there have been no indications in the literature about their possible mechanism of action. Here we studied the effect of protons on FRTL-5 cells in culture. We showed that proton beams stimulate slightly nuclear neutral sphingomyelinase activity and inhibit nuclear sphingomyelin-synthase activity in quiescent cells whereas stimulate strongly nuclear neutral sphingomyelinase activity and do not change nuclear sphingomyelin-synthase activity in proliferating cells. The study of neutral sphingomyelinase/sphingomyelin-synthase ratio, a marker of functional state of the cells, indicated that proton beams induce FRTL-5 cells in a proapoptotic state if the cells are quiescent and in an initial apoptotic state if the cells are proliferating. The changes of cell life are accompanied by a decrease of nuclear sphingomyelin and increase of bax protein. 相似文献
133.
Massimiliano Lanzi Francesco Paolo Di-Nicola Massimiliano Livi Luisa Paganin Fabio Cappelli Filippo Pierini 《Journal of Materials Science》2013,48(11):3877-3893
This article describes the preparation of thin films of conjugated polymers which can enhance their specific electrical conductivity by several orders of magnitude by changing their state from insulating to conducting materials. The examined polymers, i.e., a polyacetylenic and a polythiophenic derivative, are functionalized with thioalkylic side chains and are soluble in common organic solvents from which they lead to thick homogeneous films. The films can be deposited on different substrates, either rigid or flexible, and can be easily exposed to laser radiation to make them conductive. The process is irreversible, and the final conductivity is stable over time, even in the presence of high temperatures (up to 180 °C), moisture, and air. The high stability of treated samples, easy polymer synthesis and quick and inexpensive suitably tailored laser tracing procedure make these materials very promising for applications in organic electronics and in the development of new electronic circuitry. 相似文献
134.
The study investigated the improvements in strength and crack resistance induced by the introduction of wool fibres in an earthen material. Earthen samples reinforced by wool fibres of various fibre lengths at different fibre weight fractions were tested under flexural loading to examine the structural response of the material in terms of first-crack resistance, post-cracking residual strength and energy absorption capability. It was found that the fibrous reinforcement greatly improved the residual strength, the ductility and the energy absorption of the reinforced material as compared to the unreinforced soil. The results of the study also showed that fibre length had a notable influence on the post-fracture response of the material at large deformation regimes. 相似文献
135.
Francesco Delogu 《Journal of Materials Science》2012,47(11):4757-4762
Fe powders were mechanically processed by ball milling. The average size of coherent diffraction domains and the average strain
content were determined by X-ray diffraction. A mathematical model was developed to describe the microstructural refinement
process as a function of the number of collisions and to estimate the amount of powder effectively processed at individual
collisions. The density of dislocations was also estimated. The obtained values suggest that Fe powders can locally undergo
extremely severe deformation conditions. 相似文献
136.
Antonio Abate Annamaria Petrozza Vittoria Roiati Simone Guarnera Henry Snaith Francesco Matteucci Guglielmo Lanzani Pierangelo Metrangolo Giuseppe Resnati 《Organic Electronics》2012,13(11):2474-2478
We report on the use of a fluorinated imidazolium ionic liquid as a source of iodide ions in solvent-based electrolytes for DSSCs. Efficient dye regeneration and fast charge transport in the fluorinated electrolyte result in an overall improvement of the device performances compared to conventional hydrogenated ionic liquids. 相似文献
137.
Marta Di Pasquale Stefano Aliberti Marco Mantero Sonia Bianchini Francesco Blasi 《International journal of molecular sciences》2016,17(3)
Hospital-acquired pneumonia (HAP) is a frequent cause of nosocomial infections, responsible for great morbidity and mortality worldwide. The majority of studies on HAP have been conducted in patients hospitalized in the intensive care unit (ICU), as mechanical ventilation represents a major risk factor for nosocomial pneumonia and specifically for ventilator-associated pneumonia. However, epidemiological data seem to be different between patients acquiring HAP in the ICU vs. general wards, suggesting the importance of identifying non ICU-acquired pneumonia (NIAP) as a clinical distinct entity in terms of both etiology and management. Early detection of NIAP, along with an individualized management, is needed to reduce antibiotic use and side effects, bacterial resistance and mortality. The present article reviews the pathophysiology, diagnosis, treatment and prevention of NIAP. 相似文献
138.
Francesco Losurdo Alessandro Marra Ernesto Cassetta Umberto Monarca Ivano Dileo Vittorio Carlei 《Papers in Regional Science》2019,98(2):737-753
In order to overcome the limitations of defining industrial specializations in digital industries through SIC codes, this paper suggests measuring the specializations and competences of these industries on the basis of the degree of digital technologies present in the products and services supplied. Metadata from CrunchBase are employed, as proxies of firms' specializations and competences which are defined as the fields of activity in which firms are involved. Applying a network analysis, these specializations and competences are linked to the recognition of emerging digital technologies and the strongest combinations of products and services. We tested the proposed methodology on London, a leading centre for the digital economy. 相似文献
139.
Francesco Mirizzi 《Fusion Engineering and Design》2013,88(6-8):887-890
Future fusion reactors are asked to deliver large amount of energy in a continuative way to electrical power grids. In this frame it is very important to care the availability of the reactors since the preliminary phases of the design. Techniques to assure high levels of reliability must be extensively used and accurate programmes of maintenance must be studied, caring in the same time the training of maintenance personnel. Finally the layout of the reactor and of all its auxiliary systems must be carefully examined in order to assure an easy inspectability and a fast recovery of the power station after unavoidable failures. All the previously listed activities are summarized by the acronym RAMI (reliability, availability, maintainability and inspectability). The basics of the RAMI analysis for a conceptual LHCD system for DEMO are given in the paper. 相似文献
140.
Accurate measurement of institutional research productivity should account for the real contribution of the research staff to the output produced in collaboration with other organizations. In the framework of bibliometric measurement, this implies accounting for both the number of co-authors and each individual’s real contribution to scientific publications. Common practice in the life sciences is to indicate such contribution through the order of author names in the byline. In this work, we measure the distortion introduced to university-level bibliometric productivity rankings when the number of co-authors or their position in the byline is ignored. The field of observation consists of all Italian universities active in the life sciences (Biology and Medicine). The analysis is based on the research output of the university staff over the period 2004–2008. Based on the results, we recommend against the use of bibliometric indicators that ignore co-authorship and real contribution of each author to research outputs. 相似文献