全文获取类型
收费全文 | 2547篇 |
免费 | 131篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 29篇 |
综合类 | 9篇 |
化学工业 | 677篇 |
金属工艺 | 37篇 |
机械仪表 | 83篇 |
建筑科学 | 115篇 |
矿业工程 | 4篇 |
能源动力 | 99篇 |
轻工业 | 310篇 |
水利工程 | 10篇 |
石油天然气 | 9篇 |
武器工业 | 1篇 |
无线电 | 223篇 |
一般工业技术 | 505篇 |
冶金工业 | 145篇 |
原子能技术 | 19篇 |
自动化技术 | 409篇 |
出版年
2023年 | 24篇 |
2022年 | 59篇 |
2021年 | 183篇 |
2020年 | 69篇 |
2019年 | 69篇 |
2018年 | 90篇 |
2017年 | 78篇 |
2016年 | 78篇 |
2015年 | 76篇 |
2014年 | 118篇 |
2013年 | 190篇 |
2012年 | 119篇 |
2011年 | 194篇 |
2010年 | 141篇 |
2009年 | 126篇 |
2008年 | 129篇 |
2007年 | 122篇 |
2006年 | 103篇 |
2005年 | 79篇 |
2004年 | 68篇 |
2003年 | 63篇 |
2002年 | 56篇 |
2001年 | 38篇 |
2000年 | 27篇 |
1999年 | 33篇 |
1998年 | 56篇 |
1997年 | 48篇 |
1996年 | 30篇 |
1995年 | 24篇 |
1994年 | 22篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1974年 | 4篇 |
1967年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有2684条查询结果,搜索用时 15 毫秒
131.
Chiara Uboldi Daniele Bonacchi Giada Lorenzi M Iris Hermanns Christine Pohl Giovanni Baldi Ronald E Unger C James Kirkpatrick 《Particle and fibre toxicology》2009,6(1):18-12
Background
During the last years engineered nanoparticles (NPs) have been extensively used in different technologies and consequently many questions have arisen about the risk and the impact on human health following exposure to nanoparticles. Nevertheless, at present knowledge about the cytotoxicity induced by NPs is still largely incomplete. In this context, we have investigated the cytotoxicity induced by gold nanoparticles (AuNPs), which differed in size and purification grade (presence or absence of sodium citrate residues on the particle surface) in vitro, in the human alveolar type-II (ATII)-like cell lines A549 and NCIH441. 相似文献132.
133.
Giovanni Bruno Alexander M. Efremov Chong P. An Bryan R. Wheaton Darren J. Hughes 《Journal of Materials Science》2012,47(8):3674-3689
Following previous study on non-microcracked porous ceramics (SiC and alumina), we studied the micro and macrostrain response
of honeycomb porous microcracked ceramics under applied uniaxial compressive stress. Cordierites of different porosities were
compared. Both macroscopic and microscopic strains were measured, by extensometry and neutron diffraction, respectively. Lattice
strains were determined using a single diffraction peak (steady-state neutron source) in both the axial and the transverse
sample directions. Complementarily, we measured the macroscopic Young’s modulus of these materials as a function of temperature,
at zero load, using high-temperature laser ultrasound spectroscopy. This allowed having a non-microcracked reference state
for all the materials investigated. Confirming our previous study, we observed that macrostrain relaxation occurs at constant
load, which is not observed in non-microcracked compounds, such as SiC. This relaxation effect increases as a function of
porosity. Moreover, we generally observed a linear dependence of the diffraction modulus on porosity. However, for low and
very high applied stress, the lattice strain behavior versus stress seems to be influenced by microcracking and shows considerable
strain release, as already observed in other porous microcracked ceramics. We extended to microcracked porous ceramics (cordierite)
the macro to microstrain and stress relations previously developed for non-microcracked ceramics, making use of the integrity
factor (IF) model. Using the whole set of data available, the IF could also be calculated as a function of applied stress.
It was confirmed that highly porous microcracked materials have great potential to become stiffer and more connected. 相似文献
134.
135.
Giovanni Bruno Alexander Efremov Bryan Wheaton Ivan Bobrikov Valeriy G. Simkin Scott Misture 《Journal of the European Ceramic Society》2010,30(12):2555-2562
The lattice expansion of aluminum titanate (AT) obtained by firing a mixture of alumina, rutile, strontium and calcium carbonate and silica was measured using neutron and laboratory X-ray diffraction. The microscopic data are compared with macroscopic measurement completed by dilatometry.A powder and a compact rod sample were compared to assess the influence of micro residual stresses locked into the solid structure at grain level, which could possibly be relieved upon grinding.Results show good correlation between neutron and X-ray diffraction techniques. They also show that a compact material behaves differently than a powder, contrary to what happens for other porous ceramics such as cordierite. The integrity factor model was used to rationalize the results and predict grain level stresses in all crystal directions and all phases (AT, Strontium aluminum silicate, alumina and residual glass). Calculation show that the AT c-axis is always under compression while all other crystal directions and phases are under tension. Those micro-stresses do not undermine the macroscopic mechanical properties of the material and confer to it its interesting properties like low thermal expansion and enhanced strain tolerance. 相似文献
136.
Sandor Kasas Ksenja Radotic Giovanni Longo Bashkar Saha Livan Alonso‐Sarduy Giovanni Dietler Charles Roduit 《Microscopy research and technique》2013,76(4):357-363
Recently, atomic force microscope (AFM) manufacturers have begun producing instruments specifically designed to image biological specimens. In most instances, they are integrated with an inverted optical microscope, which permits concurrent optical and AFM imaging. An important component of the set‐up is the imaging chamber, whose design determines the nature of the experiments that can be conducted. Many different imaging chamber designs are available, usually designed to optimize a single parameter, such as the dimensions of the substrate or the volume of fluid that can be used throughout the experiment. In this report, we present a universal fluid cell, which simultaneously optimizes all of the parameters that are important for the imaging of biological specimens in the AFM. This novel imaging chamber has been successfully tested using mammalian, plant, and microbial cells. Microsc. Res. Tech. 76:357–363, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
137.
Daniela Erriquez Giovanni Perini Alessandra Ferlini 《International journal of molecular sciences》2013,14(10):19681-19704
ncRNAs are the most recently identified class of regulatory RNAs with vital functions in gene expression regulation and cell development. Among the variety of roles they play, their involvement in human diseases has opened new avenues of research towards the discovery and development of novel therapeutic approaches. Important data come from the field of hereditary muscle dystrophies, like Duchenne muscle dystrophy and Myotonic dystrophies, rare diseases affecting 1 in 7000–15,000 newborns and is characterized by severe to mild muscle weakness associated with cardiac involvement. Novel therapeutic approaches are now ongoing for these diseases, also based on splicing modulation. In this review we provide an overview about ncRNAs and their behavior in muscular dystrophy and explore their links with diagnosis, prognosis and treatments, highlighting the role of regulatory RNAs in these pathologies. 相似文献
138.
Sara Alouf Giovanni Neglia Iacopo Carreras Daniele Miorandi Álvaro Fialho 《Computer Networks》2010,54(18):3402-3420
In this work, we introduce a framework for enabling the on-line evolution of network protocols. The proposed approach is based on the use of techniques and tools drawn from evolutionary computing research, and it enables embedding evolutionary features in the operation of network protocols. In this way, it becomes possible to build a system in which the operation of the network changes at run-time to adapt to the current conditions. As a case study, we apply the proposed framework to the evolution of forwarding schemes in intermittently connected wireless networks. Simulation results are reported to validate the ability of the proposed scheme to converge to the optimal operating point and to explore the various trade-offs deriving from its design and implementation. 相似文献
139.
Changes of the main physical and technological properties of talc due to mechanical strain 总被引:2,自引:0,他引:2
A commercial talc was treated by planetary ball milling to evaluate the changes of the main physical and technological properties due to induced progressive mechanical stress.Firstly, a high orientation of talc platelets was obtained, secondly a progressive structural disorder of the talc and finally a re-aggregation of the particles during prolonged grinding was observed. Delamination during the initial and intermediate stages cannot be excluded.Mechanical grinding reduced the particles size and increased the specific surface area leading to enhanced absorption and cation exchange capacity during the initial and intermediate stages of grinding. The reduced lightness and brightness for prolonged grinding were attributed to the agglomeration of the particles. The mechanical treatment does not induce significant amorphization, thus preserving the main properties of talc even after prolonged grinding. 相似文献
140.
Giovanni Garberoglio Allan H. Harvey 《Journal of research of the National Institute of Standards and Technology》2009,114(5):249-262
Knowledge of the pair and three-body potential-energy surfaces of helium is now sufficient to allow calculation of the third density virial coefficient, C(T), with significantly smaller uncertainty than that of existing experimental data. In this work, we employ the best available pair and three-body potentials for helium and calculate C(T) with path-integral Monte Carlo (PIMC) calculations supplemented by semiclassical calculations. The values of C(T) presented extend from 24.5561 K to 10 000 K. In the important metrological range of temperatures near 273.16 K, our uncertainties are smaller than the best experimental results by approximately an order of magnitude, and the reduction in uncertainty at other temperatures is at least as great. For convenience in calculation of C(T) and its derivatives, a simple correlating equation is presented. 相似文献