首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   235篇
  免费   7篇
电工技术   2篇
化学工业   45篇
金属工艺   2篇
机械仪表   6篇
建筑科学   7篇
能源动力   6篇
轻工业   36篇
水利工程   1篇
石油天然气   1篇
无线电   17篇
一般工业技术   38篇
冶金工业   31篇
原子能技术   1篇
自动化技术   49篇
  2022年   8篇
  2021年   7篇
  2020年   6篇
  2019年   5篇
  2018年   5篇
  2017年   9篇
  2016年   7篇
  2015年   6篇
  2014年   6篇
  2013年   13篇
  2012年   22篇
  2011年   17篇
  2010年   15篇
  2009年   11篇
  2008年   10篇
  2007年   12篇
  2006年   6篇
  2005年   6篇
  2004年   5篇
  2003年   4篇
  2002年   3篇
  2001年   4篇
  2000年   3篇
  1999年   3篇
  1998年   8篇
  1997年   5篇
  1996年   9篇
  1995年   6篇
  1994年   2篇
  1993年   3篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1987年   2篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
  1969年   1篇
  1968年   2篇
  1967年   2篇
  1966年   1篇
排序方式: 共有242条查询结果,搜索用时 93 毫秒
51.
The problem we are stating is the discrimination of non-rigid objects capable of holding our attention in a scene. Motion allows gradually obtaining all moving objects shapes. We introduce an algorithm that fuses spots obtained by means of neuronal lateral interaction in accumulative computation.  相似文献   
52.
Traditional antimicrobial therapies for periodontitis (PD) have long focused on non-selective and direct approaches. Professional cleaning of the subgingival biofilm by instrumentation of dental root surfaces, known as scaling and root planning (SRP), is the mainstay of periodontal therapy and is indisputably effective. Non-physical approaches used as adjuncts to SRP, such as chemical and biological agents, will be the focus of this review. In this regard, traditional agents such as oral antiseptics and antibiotics, delivered either locally or systemically, were briefly reviewed as a backdrop. While generally effective in winning the “battle” against PD in the short term, by reducing its signs and symptoms, patients receiving such therapies are more susceptible to recurrence of PD. Moreover, the long-term consequences of such therapies are still in question. In particular, concern about chronic use of systemic antibiotics and their influence on the oral and gut microbiota is warranted, considering antibiotic resistance plasmids, and potential transfer between oral and non-oral microbes. In the interest of winning the “battle and the war”, new more selective and targeted antimicrobials and biologics for PD are being studied. These are principally indirect, blocking pathways involved in bacterial colonization, nutrient acquisition, inflammation or cellular invasion without directly killing the pathogens. This review will focus on current and prospective antimicrobial therapies for PD, emphasizing therapies that act indirectly on the microbiota, with clearly defined cellular and molecular targets.  相似文献   
53.
54.
55.
The SET protocol for secure electronic payments, in particular its purchasing phase, is intended for users connected to the Internet during the entire transaction. This requirement cannot be easily met in high communication costs and/or low bandwidth settings, typically found in mobile computing environments.In this paper we describe SET/A, a system that works according to the SET rules for purchasing operations without forcing the user to be connected during the entire transaction. This is achieved by sending an agent to the merchant's server carrying all the data necessary to order and pay the goods (products, services or information). The paper shows that this can be achieved safely and efficiently, providing an alternative way for Internet payments using the SET protocol. We give our first impressions on SET/A usage by describing a prototype implementation based on a mobile agent system called AgentSpace, as well as a detailed example of what we consider a realistic application of the system.  相似文献   
56.
Chinese chive (Allium tuberosum) is a medicinal food that is cultivated and consumed mainly in Asian countries. Its various phytochemicals and physiological effects have been reported, but only a few phytochemicals are available for skeletal muscle cell proliferation. Herein, we isolated a new compound, kaempferol-3-O-(6″-feruloyl)-sophoroside (1), along with one known flavonoid glycoside (2) and six amino acid (3–8) compounds from the water-soluble fraction of the shoot of the Chinese chive. The isolated compounds were identified using extensive spectroscopic methods, including 1D and 2D NMR, and evaluated for their proliferation activity on skeletal muscle cells. Among the tested compounds, newly isolated flavonoid (1) and 5-aminouridine (7) up-regulated PI3K/Akt/mTOR pathways, which implies a positive effect on skeletal muscle growth and differentiation. In particular, compound 1 down-regulated the Smad pathways, which are negative regulators of skeletal muscle growth. Collectively, we suggest that major constituents of Chinese chive, flavonoids and amino acids, might be used in dietary supplements that aid skeletal muscle growth.  相似文献   
57.
Fuzzy beat labeling for intelligent arrhythmia monitoring   总被引:3,自引:0,他引:3  
  相似文献   
58.
Microglia cells represent the immune system of the central nervous system. They become activated by ATP released from damaged and inflamed tissue via purinergic receptors. Ionotropic purinergic P2X4 and P2X7 receptors have been shown to be involved in neurological inflammation and pain sensation. Whether the two receptors assemble exclusively as homotrimers or also as heterotrimers is still a matter of debate. We investigated the expression of P2X receptors in BV-2 microglia cells applying the whole-cell voltage-clamp technique. We dissected P2X4 and P2X7 receptor-mediated current components by using specific P2X4 and P2X7 receptor blockers and by their characteristic current kinetics. We found that P2X4 and P2X7 receptors are activated independently from each other, indicating that P2X4/P2X7 heteromers are not of functional significance in these cells. The pro-inflammatory mediators lipopolysaccharide and interferon γ, if applied in combination, upregulated P2X4, but not P2X7 receptor-dependent current components also arguing against phenotypically relevant heteromerization of P2X4 and P2X7 receptor subunits.  相似文献   
59.
Fine particles of Gd2CuO4 were prepared by a sol-gel reaction of an aqueous solution of metal nitrates in the presence of urea, which leads to high-homogeneity polycrystalline powders of Gd2CuO4. We have studied the synthesis conditions, demonstrating the existence of a relationship between the calcination temperature and the heating time needed to attain the pure phase. Gd2CuO4 was obtained at temperatures of the order of 650°C, lower than temperatures employed in the conventional ceramic technique. The influence of the [urea]/[salts] ratio and an excess of Cu(II) in the starting solution was also studied and discussed. X-ray powder diffraction, inductively coupled plasma atomic emission spectroscopy (ICPAES), photon correlation spectroscopy (PCS), and transmission electron microscopy (TEM) were used to characterize the Gd2CuO4 samples obtained.  相似文献   
60.
Soybean (Glycine max) is an economically important crop which is very susceptible to salt stress. Tolerance to Na2SO4 stress was evaluated in soybean plants overexpressing or suppressing the phytoglobin GmPgb1. Salt stress depressed several gas exchange parameters, including the photosynthetic rate, caused leaf damage, and reduced the water content and dry weights. Lower expression of respiratory burst oxidase homologs (RBOHB and D), as well as enhanced antioxidant activity, resulting from GmPgb1 overexpression, limited ROS-induced damage in salt-stressed leaf tissue. The leaves also exhibited higher activities of the H2O2-quenching enzymes, catalase (CAT) and ascorbate peroxidase (APX), as well as enhanced levels of ascorbic acid. Relative to WT and GmPgb1-suppressing plants, overexpression of GmPgb1 attenuated the accumulation of foliar Na+ and exhibited a lower Na+/K+ ratio. These changes were attributed to the induction of the Na+ efflux transporter SALT OVERLY SENSITIVE 1 (SOS1) limiting Na+ intake and transport and the inward rectifying K+ channel POTASSIUM TRANSPORTER 1 (AKT1) required for the maintenance of the Na+/K+ balance.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号