全文获取类型
收费全文 | 5656篇 |
免费 | 163篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 81篇 |
综合类 | 28篇 |
化学工业 | 1121篇 |
金属工艺 | 190篇 |
机械仪表 | 133篇 |
建筑科学 | 242篇 |
矿业工程 | 1篇 |
能源动力 | 89篇 |
轻工业 | 769篇 |
水利工程 | 15篇 |
石油天然气 | 8篇 |
无线电 | 450篇 |
一般工业技术 | 954篇 |
冶金工业 | 1118篇 |
原子能技术 | 84篇 |
自动化技术 | 537篇 |
出版年
2021年 | 76篇 |
2020年 | 58篇 |
2019年 | 71篇 |
2018年 | 81篇 |
2017年 | 60篇 |
2016年 | 101篇 |
2015年 | 73篇 |
2014年 | 111篇 |
2013年 | 187篇 |
2012年 | 162篇 |
2011年 | 215篇 |
2010年 | 164篇 |
2009年 | 159篇 |
2008年 | 161篇 |
2007年 | 177篇 |
2006年 | 167篇 |
2005年 | 157篇 |
2004年 | 150篇 |
2003年 | 118篇 |
2002年 | 127篇 |
2001年 | 91篇 |
2000年 | 130篇 |
1999年 | 143篇 |
1998年 | 317篇 |
1997年 | 220篇 |
1996年 | 179篇 |
1995年 | 128篇 |
1994年 | 107篇 |
1993年 | 108篇 |
1992年 | 73篇 |
1991年 | 62篇 |
1990年 | 63篇 |
1989年 | 62篇 |
1988年 | 63篇 |
1987年 | 72篇 |
1986年 | 63篇 |
1985年 | 70篇 |
1984年 | 72篇 |
1983年 | 47篇 |
1981年 | 45篇 |
1980年 | 61篇 |
1979年 | 53篇 |
1978年 | 63篇 |
1977年 | 91篇 |
1976年 | 113篇 |
1975年 | 42篇 |
1974年 | 70篇 |
1973年 | 47篇 |
1970年 | 43篇 |
1967年 | 39篇 |
排序方式: 共有5820条查询结果,搜索用时 15 毫秒
1.
Bernette Maria Oosterlaken Heiner Friedrich Gijsbertus de With 《Microscopy research and technique》2022,85(1):412-417
Transmission electron microscopy (TEM) is an important analysis technique to visualize (bio)macromolecules and their assemblies, including collagen fibers. Many protocols for TEM sample preparation of collagen involve one or more washing steps to remove excess salts from the dispersion that could hamper analysis when dried on a TEM grid. Such protocols are not standardized and washing times as well as washing solvents vary from procedure to procedure, with each research group typically having their own protocol. Here, we investigate the influence of washing with water, ethanol, but also methanol and 2-propanol, for both mineralized and unmineralized collagen samples via a protocol based on centrifugation. Washing with water maintains the hydrated collagen structure and the characteristic banding pattern can be clearly observed. Conversely, washing with ethanol results in dehydration of the fibrils, often leading to aggregation of the fibers and a less obvious banding pattern, already within 1 min of ethanol exposure. As we show, this process is fully reversible. Similar observations were made for methanol and propanol. Based on these results, a standardized washing protocol for collagenous samples is proposed. 相似文献
2.
Daniela Fogli Antonio Piccinno Stefan Carmien Gerhard Fischer 《Behaviour & Information Technology》2020,39(1):27-46
ABSTRACTThe digital age of the future is ‘not out there to be discovered’, but it needs to be ‘designed’. The design challenge has to address questions about how we want to live, work, and learn (as individuals and as communities) and what we value and appreciate, e.g.: reflecting on quality of life and creating inclusive societies. An overriding design trade-off for the digital age is whether new developments will increase the digital divide or will create more inclusive societies. Sustaining inclusive societies means allowing people of all ages and all abilities to exploit information technologies for personally meaningful activities. Meta-design fosters the design of socio-technical environments that end-user developers can modify and evolve at use time to improve their quality of life and favour their inclusion in the society. This paper describes three case studies in the domain of assistive technologies in which end users themselves cannot act as end-user developers, but someone else (e.g.: a caregiver or a clinician) must accept this role requiring multi-tiered architectures. The design trade-offs and requirements for meta-design identified in the context of the case studies and other researchers’ projects are described to inform the development of future socio-technical environments focused on social inclusion. 相似文献
3.
Gökelma Mertol Einarsrud Kristian Etienne Tranell Gabriella Friedrich Bernd 《Metallurgical and Materials Transactions B》2020,51(2):850-860
Metallurgical and Materials Transactions B - The quality requirements of aluminum products are steadily increasing, and the presence of non-metallic inclusions have a large impact on the quality of... 相似文献
4.
Kazuo Tsubota Stephen C. Pflugfelder Zuguo Liu Christophe Baudouin Hyo Myung Kim Elisabeth M. Messmer Friedrich Kruse Lingyi Liang Jimena Tatiana Carreno-Galeano Maurizio Rolando Norihiko Yokoi Shigeru Kinoshita Reza Dana 《International journal of molecular sciences》2020,21(23)
Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint. 相似文献
5.
Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant. 相似文献
6.
Annika Jahn Anton Hoffmann Luisa Blaesing Fabian Kunde Martin Bertau Martina Bremer Steffen Fischer 《化学,工程师,技术》2020,92(11):1733-1740
The enzymatic conversion of lignins, possibly in combination with electrochemical oxidation, makes aromatics such as syringol, guaiacol, vanillin and catechol available in the qualities required by the fragrance industry. The lignins were obtained by soda digestion from wheat straw and Miscanthus, characterized and then converted with laccases. The overall yield amounted up to 9 wt % with a product spectrum confined to four substances. Catechol was the major product, with a fraction of ≈75 %. It can easily be isolated by extraction with acetone. 相似文献
7.
8.
9.
Fischer B. Ghetti A. Selmi L. Bet R. Sangiorgi E. 《Electron Devices, IEEE Transactions on》1997,44(2):288-296
In this paper, new homogeneous hot-electron injection data at 300 K and 77 K is provided covering applied voltages from well below to well above the Si-SiO2 barrier height, and a wide range of oxide fields. We found that, in contrast to the MOSFET case, homogeneous injection shows two different regimes for accelerating voltages below and above the barrier height. A simple interpretation of the data is proposed, and supported by Monte Carlo (MC) simulations of the injection experiment. Essentially, the two regimes are the signature of a marked transition between an electron population mostly heated by the electric field, and a tail population created by additional but less efficient energy gain mechanisms, leading to a sharp transition in the carrier distribution function. The details of the bias and temperature dependence of injection are then interpreted as the combined effect of tunneling and carrier distribution. Furthermore, possible implications on MOSFET gate currents are briefly discussed 相似文献
10.