全文获取类型
收费全文 | 1136篇 |
免费 | 68篇 |
专业分类
电工技术 | 19篇 |
综合类 | 17篇 |
化学工业 | 309篇 |
金属工艺 | 14篇 |
机械仪表 | 13篇 |
建筑科学 | 68篇 |
矿业工程 | 12篇 |
能源动力 | 14篇 |
轻工业 | 230篇 |
水利工程 | 18篇 |
石油天然气 | 2篇 |
无线电 | 42篇 |
一般工业技术 | 191篇 |
冶金工业 | 76篇 |
原子能技术 | 10篇 |
自动化技术 | 169篇 |
出版年
2024年 | 3篇 |
2023年 | 17篇 |
2022年 | 40篇 |
2021年 | 63篇 |
2020年 | 32篇 |
2019年 | 27篇 |
2018年 | 44篇 |
2017年 | 39篇 |
2016年 | 46篇 |
2015年 | 40篇 |
2014年 | 44篇 |
2013年 | 81篇 |
2012年 | 58篇 |
2011年 | 99篇 |
2010年 | 50篇 |
2009年 | 48篇 |
2008年 | 79篇 |
2007年 | 65篇 |
2006年 | 43篇 |
2005年 | 49篇 |
2004年 | 34篇 |
2003年 | 30篇 |
2002年 | 21篇 |
2001年 | 22篇 |
2000年 | 13篇 |
1999年 | 15篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1957年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有1204条查询结果,搜索用时 15 毫秒
101.
102.
Susanne Lackner 《Water research》2009,43(14):3469-3478
Polypropylene (PP) membranes and polyethylene (PE) surfaces were modified to enhance formation and shear resistance of nitrifying biofilms for wastewater treatment applications. A combination of plasma polymerization and wet chemistry was employed to ultimately introduce poly(ethyleneglycol) (PEG) chains with two different functional groups (-PEG-NH2 and -PEG-CH3). Biofilm growth experiments using a mixed nitrifying bacterial culture revealed that the specific combination of PEG chains with amino groups resulted in most biofilm formation on both PP and PE samples. Detachment experiments showed similar trends: biofilms on -PEG-NH2 modified surfaces were much stronger compared to the other modifications and the unmodified reference surfaces. Electrostatic interactions between the protonated amino group and negatively charged bacteria as well as PEG chain density which can affect the surface structure might be possible explanations of the superiority of the -PEG-NH2 modification. The success of the-PEG-NH2 modification was independent of the original surface and might, therefore, be used in wastewater treatment bioreactors to improve reactor performance by making biofilm formation more stable and predictable. 相似文献
103.
Which kind of instruction helps children aged 9–14 years interact efficiently with a mobile phone? Due to analogies between navigation in menu structures and the natural environment, three instructions providing different forms of spatial knowledge were under study: A step-by-step instruction featuring landmark knowledge of the menu functions to be selected, a diagram of the menu structure providing survey knowledge and a free exploration of the menu, also giving the children the opportunity to develop survey knowledge. Results show a superiority of the two instructions that provide survey knowledge, except for the youngest children aged 9–10 years. This group showed to have lower spatial abilities and is therefore presumably not able to understand and integrate this type of knowledge. For those very young children, the landmark information given in traditional step-by-step instructions is more helpful. It is concluded, that simple diagrams of the menu structure can help children from 11 years on to significantly ease their interaction with small menu driven devices. 相似文献
104.
Red wine contains a diversity of polyphenolic compounds that exert beneficial health effects including anti-cancer effects. This trial evaluated the anti-proliferative potential of red muscadine (Vitis rotundifolia) and red cabernet sauvignon (Vitis vinifera) wines in cell culture. Chemical properties of wines were determined by HPLC-PDA analysis and concentrated extracts of each wine were evaluated before and after glycosidic hydrolysis in MOLT-4 leukemia cells. Cell growth and the induction of apoptosis were evaluated after exposure to various extract dilutions. Wine extracts reduced cell viability up to 68% and cell numbers up to 50% after 48 h with muscadine extracts being more effective than cabernet sauvignon. Caspase-3 activity was induced similarly by all extracts in a dose dependent manner. Cell cycle arrest in the G2/M phase was observed for both muscadine and the non-hydrolyzed cabernet sauvignon extract. Collectively, extracts from both wines exerted anti-cancer effects in leukemia cells. 相似文献
105.
This study examines the impact of university spillovers on the locational choice of firm formation. Based on a unique and hand-collected data set of high-technology start-ups publicly listed in Germany, this paper tests the propositions that geographic proximity to the university is influenced by the kind of science and type of knowledge spillover. The results provide evidence that younger high technology start-ups (less than eight years old) settle near universities with a high academic output and a high number of students in both natural and social science. Thus, spillover of tacit knowledge has an impact on the firms' geographic decision. Older firms, however, only locate closer to technical universities in order to satisfy demand for traditional German industries such as engineering and machinery. 相似文献
106.
The group birefringence and chromatic dispersion of a polarisation maintaining bow-tie erbium-doped silica fibre have been measured in the wavelength range 1.2-1.68 mu m by an interferometric measurement technique without any polarisers. The group birefringence is lower than that of a conventional bow-tie fibre and the zero dispersion wavelengths of the two polarisation modes are shifted to 1.613 and 1.630 mu m.<> 相似文献
107.
108.
Andrea Nolte Susanne Hossfeld Marcell Post Jan Niederlaender Tobias Walker Christian Schlensak Hans Peter Wendel 《Journal of materials science. Materials in medicine》2014,25(9):2121-2130
Chitosan is used in several pharmaceutical and medical applications, owing to its good cytocompatibility and hemocompatibility. However, there are conflicting reports regarding the biological activities of chitosan with some studies reporting anti-inflammatory properties while others report pro-inflammatory properties. In this regards we analyzed the endotoxin content in five different chitosans and examined these chitosans with their different deacetylation degrees for their hemocompatibility and cytocompatibility. Therefore, we incubated primary human endothelial cells or whole blood with different chitosan concentrations and studied the protein and mRNA expression of different inflammatory markers or cytokines. Our data indicate a correlation of the endotoxin content and cytokine up-regulation in whole blood for Poly-Morpho-Nuclear (PMN)-Elastase, soluble terminal complement complex SC5b-9, complement component C5/C5a, granulocyte colony-stimulating factor, Interleukin-8 (IL), IL-10, IL-13, IL-17E, Il-32α and monocyte chemotactic protein-1. In contrast, the incubation of low endotoxin containing chitosans with primary endothelial cells resulted in increased expression of E-selectin, intercellular adhesion molecule-1, vascular cell adhesion protein-1, IL-1β, IL-6 and IL-8 in endothelial cells. We suggest that the endotoxin content in chitosan plays a major role in the biological activity of chitosan. Therefore, we strongly recommend analysis of the endotoxin concentration in chitosan, before further determining if it has pro- or anti-inflammatory properties or if it is applicable for pharmaceutical and medical fields. 相似文献
109.
Dirk Oliver Schmidt Susanne Hoffmann‐Eifert Hehe Zhang Camilla La Torre Astrid Besmehn Michael Noyong Rainer Waser Ulrich Simon 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(48):6444-6456
Resistively switching devices are considered promising for next‐generation nonvolatile random‐access memories. Today, such memories are fabricated by means of “top–down approaches” applying thin films sandwiched between nanoscaled electrodes. In contrast, this work presents a “bottom–up approach” disclosing for the first time the resistive switching (RS) of individual TiO2 nanoparticles (NPs). The NPs, which have sizes of 80 and 350 nm, respectively, are obtained by wet chemical synthesis and thermally treated under oxidizing or vacuum conditions for crystallization, respectively. These NPs are deposited on a Pt/Ir bottom electrode and individual NPs are electrically characterized by means of a nanomanipulator system in situ, in a scanning electron microscope. While amorphous NPs and calcined NPs reveal no switching hysteresis, a very interesting behavior is found for the vacuum‐annealed, crystalline TiO2–x NPs. These NPs reveal forming‐free RS behavior, dominantly complementary switching (CS) and, to a small degree, bipolar switching (BS) characteristics. In contrast, similarly vacuum‐annealed TiO2 thin films grown by atomic layer deposition show standard BS behavior under the same conditions. The interesting CS behavior of the TiO2–x NPs is attributed to the formation of a core–shell‐like structure by re‐oxidation of the reduced NPs as a unique feature. 相似文献
110.
Ralf Rettig Susanne Steuer Robert F. Singer 《Journal of Phase Equilibria and Diffusion》2011,32(3):198-205
Interdiffusion and impurity diffusion of Ge is studied in Ni and multicomponent alloys over the temperature range of 1150-1250 °C.
The diffusion is investigated using diffusion couples, which are evaluated using microprobe measurements. The interdiffusion
coefficients are calculated with the den Broeder method, while the impurity diffusion coefficients are determined with the
Hall method. A model for the diffusion simulation software DICTRA is developed by mobility assessments. Further on, the diffusion
of Ge in the multicomponent superalloys PWA1483 and René N5 is investigated. The Ge diffusion coefficient in René N5 is 4.5 × 10−14 m2/s at 1180 °C which is similar to other alloying elements such as Co, Cr, Mo or Ta. 相似文献