全文获取类型
收费全文 | 2118篇 |
免费 | 64篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 54篇 |
综合类 | 4篇 |
化学工业 | 254篇 |
金属工艺 | 26篇 |
机械仪表 | 20篇 |
建筑科学 | 114篇 |
矿业工程 | 3篇 |
能源动力 | 29篇 |
轻工业 | 842篇 |
水利工程 | 7篇 |
石油天然气 | 7篇 |
无线电 | 157篇 |
一般工业技术 | 223篇 |
冶金工业 | 199篇 |
原子能技术 | 9篇 |
自动化技术 | 235篇 |
出版年
2023年 | 15篇 |
2022年 | 28篇 |
2021年 | 44篇 |
2020年 | 25篇 |
2019年 | 31篇 |
2018年 | 31篇 |
2017年 | 29篇 |
2016年 | 24篇 |
2015年 | 35篇 |
2014年 | 53篇 |
2013年 | 81篇 |
2012年 | 49篇 |
2011年 | 81篇 |
2010年 | 50篇 |
2009年 | 41篇 |
2008年 | 59篇 |
2007年 | 53篇 |
2006年 | 42篇 |
2005年 | 43篇 |
2004年 | 50篇 |
2003年 | 35篇 |
2002年 | 21篇 |
1999年 | 26篇 |
1998年 | 36篇 |
1997年 | 21篇 |
1996年 | 21篇 |
1995年 | 15篇 |
1994年 | 20篇 |
1993年 | 18篇 |
1971年 | 20篇 |
1924年 | 17篇 |
1923年 | 30篇 |
1922年 | 19篇 |
1921年 | 20篇 |
1918年 | 19篇 |
1917年 | 58篇 |
1916年 | 48篇 |
1915年 | 33篇 |
1914年 | 18篇 |
1913年 | 21篇 |
1912年 | 40篇 |
1911年 | 46篇 |
1910年 | 28篇 |
1909年 | 32篇 |
1908年 | 33篇 |
1907年 | 33篇 |
1906年 | 44篇 |
1905年 | 45篇 |
1904年 | 51篇 |
1903年 | 29篇 |
排序方式: 共有2183条查询结果,搜索用时 10 毫秒
2.
Helen N. Asemota Max A. Wellington Adewale A. Odutuga Mohammed H. Ahmad 《Journal of the science of food and agriculture》1992,60(3):309-312
The effect of short-term storage on the protein, phosphorus and phenolic content as well as peroxidase and o-diphenolase activities of cut, harvested Jamaican yam (Dioscorea sp) tubers (D rotundata. D alata and D cayenensis) was studied. There was an initial increase in the total phenolic content up to the third week of storage followed by a gradual decrease to the sixth week. Phenolic content was found to be highest in D cayenensis followed by D rotundata and D alata. The activities of peroxidase (EC 1. 11. 1. 7) and o-diphenolase (EC 1. 10.3.1) increased steadily up to the third week of storage and thereafter decreased to the fifth week. The intensity and rapidity of browning in tubers when cut, correlated very closely with the tuber o-diphenolase and phenolic content levels while the onset of rotting correlated with the peroxidase activity levels in the species studied. 相似文献
3.
The total syntheses of 9(Z),12(E)- and 9(E),12(Z)-octadecadienoic acids have been carried out. A useful intermediate in both
syntheses, 8-bromo-octanoic acid, recently has become available from commercial sources. This compound has been used to expedite
the preparation of these isomers. The remaining carbon atoms were derived from propargyl alcohol along with either 1-heptyne
or acetylene and 1-bromopentane. Because the overall yield for each sequence was roughly 15% and there were no extraordinary
reaction conditions in any of the synthetic steps, the compounds could be prepared readily in multiple gram quantities. The
syntheses of the two compounds were supported by data from a variety of spectroscopic techniques. 相似文献
4.
A case of Macrozamia riedlei seed poisoning is described in a young Dachshund. Vomiting and depression commenced within 6 h of ingestion; other signs that developed included severe hepatopathy, jaundice, abdominal pain that was unresponsive to analgesics, severe gastro-intestinal haemorrhage and thrombocytopenia as well as crystalluria and marrow dyserythropoiesis. The dog was euthanased 6 days after ingestion of the seeds. 相似文献
5.
6.
Matthias Max 《突发事故与危机管理杂志》2021,29(1):2-11
Digitalization and the trend towards more short‐term and project‐oriented social engagement have had a direct impact on traditional crisis management. This societal change has supported the evolution of new types of volunteers who use low‐threshold potentials to organize and maintain support independently. Traditional institutions like the German Red Cross are challenged to deal with these rapid changes regarding their own organizational culture in relation to the new phenomenon of so‐called unaffiliated volunteers. This paper investigates how unaffiliated volunteers influence and change the organizational culture of German disaster management by analysing and reflecting organizational adaptation processes in the aftermath of the German floods in 2013, the storm events in the west of Germany in 2014 and the refugee relief mission in 2015–2016. Therefore, semi‐structured interviews with experts of the German Red Cross were held to analyse their reactions towards unaffiliated Volunteers during the Floods in 2013 and the refugee relief missions, and further focus group interviews were conducted to validate the extracted results. Findings suggest that among professionals and leading entities in the German Red Cross, a process of rethinking has emerged, recognizing the importance and necessity to open up organizational structures for the collaboration and coordination of unaffiliated volunteers. 相似文献
7.
Said Ghaout Alain Louveaux Anne Marie Mainguet Max Deschamps Youssef Rahal 《Journal of chemical ecology》1991,17(8):1499-1515
A field study of the food eaten by solitary desert locusts was carried out in a winter breeding area in Mauritania. The food eaten, determined by the plant epidermis found in fecal pellets, was compared to the plant's availability in the habitat.Schouwia purpurea, well represented in the diets, was dominant at the study site. Adults had a preference forTribulus terrester. Growth and feeding on these two plants were compared. The high water content ofS. purpurea leaves limited the dry matter eaten and slowed down growth. Glucosinolates were separated and quantified by gas chromatography. There are 132mol/g dry matter in green leaves. In multiple choice tests, with paper disks, glucosinolate extracts were phagostimulant at a low concentration (21mol/g dry matter) and repulsive at a higher one (214mol/ g dry matter). Biting behavior onS. purpurea was recorded and analyzed on video. The importance ofSchouwia purpurea in desert locust habitats and its defenses is discussed. 相似文献
8.
Autonomy for Mars Rovers: Past, Present, and Future 总被引:1,自引:0,他引:1
The vehicles used to explore the Martian surface require a high degree of autonomy to navigate challenging and unknown terrain, investigate targets, and detect scientific events. Increased autonomy will be critical to the success of future missions. 相似文献
9.
Sliding Mode Control with Adaptive Fuzzy Dead-Zone Compensation of an Electro-hydraulic Servo-System 总被引:2,自引:0,他引:2
Wallace M. Bessa Max S. Dutra Edwin Kreuzer 《Journal of Intelligent and Robotic Systems》2010,58(1):3-16
Electro-hydraulic servo-systems are widely employed in industrial applications such as robotic manipulators, active suspensions,
precision machine tools and aerospace systems. They provide many advantages over electric motors, including high force to
weight ratio, fast response time and compact size. However, precise control of electro-hydraulic systems, due to their inherent
nonlinear characteristics, cannot be easily obtained with conventional linear controllers. Most flow control valves can also
exhibit some hard nonlinearities such as dead-zone due to valve spool overlap. This work describes the development of an adaptive
fuzzy sliding mode controller for an electro-hydraulic system with unknown dead-zone. The boundedness and convergence properties
of the closed-loop signals are proven using Lyapunov stability theory and Barbalat’s lemma. Numerical results are presented
in order to demonstrate the control system performance. 相似文献
10.