全文获取类型
收费全文 | 2349篇 |
免费 | 114篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 17篇 |
综合类 | 4篇 |
化学工业 | 525篇 |
金属工艺 | 40篇 |
机械仪表 | 53篇 |
建筑科学 | 215篇 |
矿业工程 | 1篇 |
能源动力 | 114篇 |
轻工业 | 262篇 |
水利工程 | 40篇 |
石油天然气 | 5篇 |
无线电 | 148篇 |
一般工业技术 | 436篇 |
冶金工业 | 121篇 |
原子能技术 | 18篇 |
自动化技术 | 465篇 |
出版年
2023年 | 25篇 |
2022年 | 43篇 |
2021年 | 54篇 |
2020年 | 43篇 |
2019年 | 52篇 |
2018年 | 63篇 |
2017年 | 53篇 |
2016年 | 67篇 |
2015年 | 61篇 |
2014年 | 89篇 |
2013年 | 169篇 |
2012年 | 142篇 |
2011年 | 158篇 |
2010年 | 137篇 |
2009年 | 117篇 |
2008年 | 145篇 |
2007年 | 123篇 |
2006年 | 114篇 |
2005年 | 104篇 |
2004年 | 94篇 |
2003年 | 73篇 |
2002年 | 79篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 34篇 |
1998年 | 38篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 18篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1978年 | 7篇 |
1943年 | 16篇 |
1942年 | 12篇 |
1941年 | 8篇 |
1940年 | 8篇 |
1939年 | 7篇 |
1938年 | 5篇 |
1937年 | 5篇 |
排序方式: 共有2464条查询结果,搜索用时 46 毫秒
71.
72.
73.
Berend Denkena Jan Brüning Lars Windels Dirk Euhus Stefan Kirsch Daniel Overbeck Thomas Lepper 《Production Engineering》2017,11(6):715-722
Today, machining of large, integral constructed structural parts requires expensive machining centers. In contrast, modern industrial robots are suitable for a wide field of applications and are characterized large working spaces and low capital investment. Therefore, they provide high economical potential for machining applications in aerospace industry, especially for the machining of near to shape pre-products like extruded profiles. However, their constructive characteristics like low stiffness and high sensitivity to vibrations lead to disadvantages compared with conventional machining centers and have to be considered during process planning. Therefore, several methods for offline and online optimization of robot machining processes were developed and integrated in a new process chain for manufacturing of structural fuselage parts. Thereby, the conventional CAD–CAM process planning chain was extended with simulation based analysis and optimization methods and a load-depending trajectory planning. These methods for offline process optimization within this novel process chain are presented in this paper. 相似文献
74.
Henrik Peisker Lars Heepe Alexander E. Kovalev Stanislav N. Gorb 《Journal of the Royal Society Interface》2014,11(99)
Wet adhesive systems of insects strongly rely for their function on the formation of capillary bridges with the substrate. Studies on the chemical composition and evaporation dynamics of tarsal secretions strongly suggest a difference in chemistry of secretion in beetles and flies, both possessing hairy attachment devices. This difference is assumed to influence the viscosity of the secretion. Here, we applied a microrheological technique, based on the immersion of nanometric beads in the collected tarsal footprints, to estimate secretion viscosity in a beetle (Coccinella septempunctata) and a fly (Calliphora vicina). Both species studied possess distinct differences in viscosity, the median of which was calculated as 21.8 and 10.9 mPa s, respectively. We further present an approximate theoretical model to calculate the contact formation time of spatula-like terminal contact elements using the viscosity data of the covering fluid. The estimated contact formation time is proportional to the tarsal secretion viscosity and to the square of the contact radius of the contact element. 相似文献
75.
Housing preweaned dairy calves in pairs rather than individually has been found to positively affect behavioral responses in novel social and environmental situations, but concerns have been raised that close contact among very young animals may impair their health. In previous studies, the level of social contact permitted in individual housing has been auditory, visual, or physical contact. It is unclear how these various levels of social contact compare with each other and to pair housing, when their effects on behavior and health are considered, and whether the timing of pair housing has an effect. To investigate this, 110 Holstein calves (50 males, 60 females) in 11 blocks were paired according to birth date. Within 60 h of birth, each pair of calves was allocated to 1 of 5 treatments: individual housing with auditory contact (I), individual housing with auditory and visual contact (V), individual housing with auditory, visual, and tactile contact (T), pair housing (P), or individual housing with auditory and visual contact the first 2 wk followed by pair housing (VP). At 6 wk of age, calves were subjected to a social test and a novel environment test. In the social test, all pair-housed calves (P and VP) had a shorter latency to sniff an unfamiliar calf than did individually housed calves (I, V, and T), whereas calves with physical contact (T, P, and VP) sniffed the unfamiliar calf for longer than calves on the remaining treatments (I and V). In the novel environment test, calves with physical contact (T, P, and VP) had a lower heart rate, and more of these calves vocalized during the test compared with calves without physical contact (I and V). No effect of treatment was found for clinical scores, levels of the 5 most common pathogens in feces, or in development of serum antibodies against the 3 most common respiratory pathogens. Calves housed individually are more fearful of unfamiliar calves than are pair-housed calves. Contrary to common belief, the allowance of physical contact and pair housing had no effects on the health of the calves. 相似文献
76.
77.
78.
It is of high technical importance to consider the loading and unloading dynamics of hydride-based hydrogen storage tanks, which are mainly influenced by the heat and gas transfer properties inside the reaction bed. In this regard, hydride-graphite composites offer improved heat transfer properties and higher volumetric storage capacities compared to commonly used powder beds. 相似文献
79.
In this paper, we develop models for capacity planning within the framework of stochastic processing times and stochastic demand for different process outcomes in high-flexibility environments. We particularly address stochastic interdependencies between processing times for different processes (inter-process correlation), interdependencies between the capacity consumption (task times) of different executions of the same task in a given production stage (intra-process correlation) as well as interdependencies between the demand for different process outcomes. After presenting the base model, we conduct extensive sensitivity analyses and analyze the main relationships between different model variables. We use process and demand data from the financial industry to demonstrate the applicability and relevance of our findings. 相似文献
80.
The development and cultivation of genetically modified crops is still increasing globally. Food and feed imports from outside the European Union (EU) will subsequently require more effort from the responsible authorities in monitoring the compliance with effective labelling regulations. The aim of this study was the development of the GMOfinder, a database for collection and interpretation of information related to the screening for genetically modified organisms (GMOs). Different genetic elements (e.g. promoters, terminators, structural genes) are artificially introduced into plants to establish new genetic modifications. The introduced elements may vary between GMO events, depending on the intended trait(s). Screening for such inserted elements with (real-time) polymerase chain reaction is a common first step to analyse samples for the presence of any genetical modification. From the pattern of detectable and nondetectable elements, valuable conclusions about the identity of putative present GMO event(s) can be drawn with the GMOfinder. Information about selected genetic elements from the literature, applications for authorisation and other (web) sources were systematically integrated in a tabular matrix format. Special care was taken to additionally record the sources of the information, thus facilitating evaluation of screening results, and tracing of possible errors in the matrix. The GMOfinder accesses data from the element matrix with implemented algorithms and facilitates to interpret the outcome of screenings. Such a preselection helps to systematically narrow down the candidates for subsequent identification reactions. Optional display of events with potentially masked elements completes the included features. 相似文献