全文获取类型
收费全文 | 927篇 |
免费 | 69篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 278篇 |
金属工艺 | 13篇 |
机械仪表 | 20篇 |
建筑科学 | 29篇 |
矿业工程 | 2篇 |
能源动力 | 51篇 |
轻工业 | 100篇 |
水利工程 | 5篇 |
石油天然气 | 4篇 |
无线电 | 60篇 |
一般工业技术 | 139篇 |
冶金工业 | 82篇 |
原子能技术 | 7篇 |
自动化技术 | 200篇 |
出版年
2023年 | 14篇 |
2022年 | 30篇 |
2021年 | 36篇 |
2020年 | 24篇 |
2019年 | 42篇 |
2018年 | 37篇 |
2017年 | 29篇 |
2016年 | 32篇 |
2015年 | 16篇 |
2014年 | 44篇 |
2013年 | 49篇 |
2012年 | 53篇 |
2011年 | 59篇 |
2010年 | 49篇 |
2009年 | 44篇 |
2008年 | 39篇 |
2007年 | 37篇 |
2006年 | 46篇 |
2005年 | 31篇 |
2004年 | 22篇 |
2003年 | 40篇 |
2002年 | 27篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 30篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 9篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有998条查询结果,搜索用时 15 毫秒
31.
32.
Moisés Frías Holmer Savastano Ernesto Villar M. Isabel Sánchez de Rojas Sergio Santos 《Cement and Concrete Composites》2012,34(9):1019-1023
The worldwide production of bamboo generates large volumes of leaf wastes, which are deposited in landfills or burned in an uncontrolled manner, with negative effects in the environment. The ash obtained by calcining of the bamboo leaf waste, shows good qualities as supplementary cementing material for the production of blended cements.The current paper shows a detailed scientific study of a Brazilian bamboo leaf ash (BLA) calcined at 600 °C in small scale condition, by using different techniques (XRF, XRD, SEM/EDX, FT–IR, TG/DTG) and technical study in order to analyse the behaviour of this ash in blended cements elaborated with 10% and 20% by mass of BLA. The results stated that this ash shows a very high pozzolanic activity, with a reaction rate constant K of the order of 10?1/h and type I CSH gel was the main hydrated phase obtained from pozzolanic reaction. The BLA blended cements (10% and 20%) complied with the physical and mechanical requirements of the existing European standards. 相似文献
33.
34.
Recent work on reactive flash sintering of powders of two oxides, bismuth and of iron oxide, into pure single phase bismuth ferrite, which was accomplished in a few seconds at low furnace temperatures, is expanded to four constituents, alumina, lithia, zirconia, and lanthana, to produce reasonably dense polycrystals of a predominantly single phase, cubic LLZO(Al). Transformation and sintering occur concurrently at a furnace temperature near 700°C, in ambient atmosphere, in just a few seconds. The process may simplify the preparation of complex ceramics with new chemistries and dopants, which are predicted from ab intio calculations to have special attributes, not only because the powders sinter quickly at low temperatures, but also because the need for stoichiometric powders as starting materials is obviated. 相似文献
35.
André Medeiros De Andrade Roberto Ferreira Machado Michel Ulisses Franz Bremer Carlos Ernesto Gonçalves Reynaud Schaefer Jefferson Cardia Simões 《International journal of remote sensing》2018,39(8):2238-2254
The aim of this work is to produce a simplified vegetation map of ice-free areas of the Fildes Peninsula (FP) and Ardley Island (AI) thought object-oriented classification using a QuickBird satellite image and to evaluate the influence of the global solar radiation (GSR) over the vegetation distribution. The vegetation data were generated from multiresolution segmentation using the panchromatic and infrared layers, and for the classification we calculated the normalized vegetative difference index (NVDI) and the green NVDI. Two classes were created – Lichen and Moss Cushion SubFormation and Moss Subformation – with 48 vegetation samples collected on surveys during the austral summers of 2008 and 2009. We used a kappa index to evaluate the classification efficiency using 100 sampled points obtained in austral summer of 2013. The GSR was estimated, and in order to evaluate the effect of meteorological phenomena and cloudless, we measured the GSR using a net radiometer model CNR4 installed in FP between 2014 and 2016. The estimate of GSR was done for seasons of 2015, in order to estimate the light compensation point and the saturation point for the plant communities in FP and AI. The kappa index was 0.73 and the global accuracy was 0.78, showing consistency between the classification and ground truth. The area was covered by vegetation in FP was 16.7% and in AI is 59.1%. The vegetation cover is distributed differently at FP and AI, and our results suggest GSR plays an important role in vegetation distribution and these tendencies could be related to greater GSR demand by mosses when compared to lichens. 相似文献
36.
37.
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
38.
Metal‐Organic Framework Surface Functionalization: GraftFast Surface Engineering to Improve MOF Nanoparticles Furtiveness (Small 40/2018)
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
39.
Andrea Ruiu Mireille Vonlanthen Pasquale Porcu Israel Gonzalez-Méndez Ernesto Rivera 《Journal of Inorganic and Organometallic Polymers and Materials》2018,28(2):448-456
In this paper, we describe the synthesis and characterization of four novel pyrene labeled compounds, some of them dendritic, which can act as potential sensors for the detection of nitro compounds in methanol solution. Methanol was selected as solvent due to its polar properties, which provide similar characteristics to water. The obtained pyrene labeled molecules (PyOH, Pytb, PyNK1OH and PyNK1tb) were studied by UV–Vis and steady state fluorescence spectroscopy. Their application as sensors has been tested with three different nitro compounds: nitrobenzene, 1-chloro-2,4-dinitrobenzene and nitromethane. PyOH and Pytb showed a detection concentration limit for the analyzed quenchers in the order of nM, making these compounds suitable for high-sensitive sensoring. PyNK1OH and PyNK1tb displayed high sensibility at µM concentration. All the sensors showed an accurate response towards quencher analytes. 相似文献
40.
Ernesto Silva M Srikanth Chakravartula S Steven S. C. Chuang 《Topics in Catalysis》2012,55(7-10):580-586
Basic catalysts for carbon?Ccarbon addition reactions were synthesized by immobilization of amine species on silica supports. Tetraethylenepentamine was impregnated and immobilized on amorphous silica (SiO2) and SBA-15 using an epoxy resin. The basicity of the catalysts was determined by adsorption?Cdesorption of CO2 and the degree of immobilization was evaluated by FTIR. The catalytic activity towards the Claisen condensation reaction of methyl benzoate and methyl ethyl ketone was evaluated by an in-situ FTIR micro-scale reactor. A mechanism is proposed to show that the catalysts promote the formation of ??-diketone and methanol; the effects of the support and amine immobilization degree are discussed. 相似文献