全文获取类型
收费全文 | 873篇 |
免费 | 19篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 158篇 |
金属工艺 | 19篇 |
机械仪表 | 18篇 |
建筑科学 | 40篇 |
矿业工程 | 15篇 |
能源动力 | 31篇 |
轻工业 | 77篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 118篇 |
一般工业技术 | 122篇 |
冶金工业 | 85篇 |
原子能技术 | 4篇 |
自动化技术 | 186篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 11篇 |
2019年 | 17篇 |
2018年 | 23篇 |
2017年 | 7篇 |
2016年 | 23篇 |
2015年 | 18篇 |
2014年 | 26篇 |
2013年 | 65篇 |
2012年 | 39篇 |
2011年 | 55篇 |
2010年 | 49篇 |
2009年 | 50篇 |
2008年 | 43篇 |
2007年 | 43篇 |
2006年 | 55篇 |
2005年 | 40篇 |
2004年 | 37篇 |
2003年 | 23篇 |
2002年 | 23篇 |
2001年 | 16篇 |
2000年 | 13篇 |
1999年 | 17篇 |
1998年 | 23篇 |
1997年 | 14篇 |
1996年 | 4篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有900条查询结果,搜索用时 15 毫秒
61.
Dave Carr Audrey Mendoza 《电子产品世界》2005,(17):88-89
用户对激动人心的全新网络服务的需求,正在推动网络带宽和数据流量的增长.作为回应,网络正在向更有效的以包为基础的模式发展,这种模式使网络能够为用户提供其需要的服务,并开发出额外的收入来源.网络设备制造商必须掌握包处理技术,才能提供新的服务,从而应对不断增加的网络复杂性及适应不同网速的要求. 相似文献
62.
Yiping He Qiang Zhang Nurmikko A.V. Slaughter J. Dave R.W. Tehrani S. 《Electronics letters》2001,37(24):1459-1460
A hybrid magneto-optoelectronic device is demonstrated, composed of a magnetic tunnel junction and a vertical cavity surface emitting diode laser. External magnetic field changes are translated into amplitude modulation of the laser output power with sensitivity that suggests applications in wireless and remote sensing of magnetic fields 相似文献
63.
64.
José A. Amador David Sotomayor-Ramírez Gustavo Martínez Lixian Chen Dave Bachoon 《Lakes & Reservoirs: Research and Management》2008,13(4):301-317
Using a combination of chemical and microbiological (culture-dependent and -independent) approaches, sources of human faecal contamination were identified in two water reservoirs in Puerto Rico – Guajataca and La Plata. Fluorescence from optical brighteners (OB) – commonly found in laundry detergents – was used as an indicator of contamination from septic systems and other household discharges. Traditional indicators of faecal contamination (e.g. Escherichia coli; faecal enterococci) were enumerated, and human faecal contamination was confirmed through detection of Bifidobacterium adolescentis utilizing polymerase chain reaction (PCR)-based analyses. For Guajataca Reservoir, four of 19 sampling sites (21%) were positive for the presence of B. adolescentis under baseflow conditions. The OB fluorescence data suggested that the most likely source for three of these sites was residential, whereas the source of contamination at the remaining site, although of human origin, was probably non-residential. B. adolescentis was present in 83% (19 of 23) of the sampling sites in La Plata. The La Plata sources were more difficult to identify because samples were taken under stormflow conditions, although the presence of OB fluorescence suggested a residential origin in a number of instances. OB fluorescence and traditional bacterial indicators of faecal contamination produced a number of false positive and negative findings for both reservoirs, pointing to the importance of understanding the limitations of these tools for tropical freshwater systems. The results of this study should be useful in developing a weight-of-evidence approach for the identification of potential sources and extent of human faecal contamination in similar tropical reservoirs, a necessary step in the development of management plans to reduce or eliminate these sources. 相似文献
65.
由运算放大器构成的反馈系统常用于使系统保持稳定。但是在一些情况下也有意外发生。比如太阳能船的玩具,当有时打开开关时,玩具甚至会发出“噗噗”的声响。这种情况有可能是由于运算放大器发生了意外正反馈(inadvertent positive feedback)导致的。 相似文献
66.
Daniel Lepek Jose Manuel Valverde Robert Pfeffer Rajesh N. Dave 《American Institute of Chemical Engineers》2010,56(1):54-65
We show experimental results on a proposed technique to enhance the fluidization of nanoparticle beds. This technique consists of the application of an alternating electric field to the nanofluidized bed. Three different field configurations have been tested: co‐flow field, cross‐flow field, and variable field configurations. Nanoparticle agglomerates are naturally charged by contact and tribo charging mechanisms and therefore are agitated by the action of the externally applied field, which enhance fluidization. According to our observations, the best results are obtained for the variable field configuration. In this configuration, the electric field strength is higher at the bottom of the bed, whereas it is almost negligible at the free surface. Thus, the larger agglomerates, which tend to sink at the bottom of the bed due to stratification, and usually impede uniform fluidization, are strongly agitated. It is thought that the strong agitation of the bigger agglomerates that usually sink to the bottom of the bed contributes to further homogenize the distribution of the gas flow within the bed by destabilizing the development of gas channels close to the gas distributor. On the other hand, the smaller agglomerates at the vicinity of the free surface are just weakly excited. Consequently, fluidization is greatly enhanced, whereas at the same time excessive elutriation is avoided. It is demonstrated that this technique is even suitable to achieve highly expanded fluidization of unsieved nanopowder samples even though the fluidization state returns to be heterogeneous upon the electric field being turned off. © 2009 American Institute of Chemical Engineers AIChE J, 2010 相似文献
67.
Isabel M. N. Sousa John R. Mitchell Dave A. Ledward Sandra E. Hill M. Luisa Beir?o da Costa 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1995,201(6):566-569
Differential scanning calorimetry (DSC) was used to study the 7S and 11S globulin fractions extracted from lupin seed (Lupinus luteus) flour. In agreement with previous work on other lupin species, the isolate showed three denaturation peaks compared to the two observed with soy. By comparison with the isolated globulin fractions, the denaturation peaks at the two higher temperatures in the lupin isolate were assigned to the 11S and 7S globulins. The denaturation temperature of the lupin 7S globulin was about 10 K higher than that for the corresponding soy globulin, whereas the values for the 11S globulin were similar. All globulins displayed increasing thermal stability with decreasing moisture contents. Possible reasons for the differences in behaviour of soy and lupin protein isolates are discussed. 相似文献
68.
Ruth Tunnell Mark Ashcroft Roz Dale Dave Tod William G. Proud 《Propellants, Explosives, Pyrotechnics》2014,39(5):707-713
In part 1 of this paper, it was demonstrated that a nitroglycerine and polyethylene glycol based propellant containing ammonium perchlorate degraded at a slower rate at temperatures of 80 °C or less compared with the other two energetic materials studied which did not have this oxidizer present. It was suggested that ammonium perchlorate might act as an oxygen inhibitor reducing the oxidation rate of the polyethylene glycol binder which decreases the rate of propellant decomposition. In part 2, the specific interaction between ammonium perchlorate, nitroglycerine and polyethylene glycol is reported. It has been shown that at temperatures lower than 90 °C, if there is any uncured and unstabilised PEG present, nitroglycerine rapidly degrades in the presence of ammonium perchlorate but this is prevented if stabiliser is added. In addition, ammonium perchlorate initially appears to hinder acid hydrolysis of nitroglycerine which also slows down the degradation of polyethylene glycol based propellants. However, in the long term at low temperatures, or short term at higher temperatures, AP accelerates the decomposition of NG. 相似文献
69.
The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit. 相似文献
70.
Didier Bardon Dick Berry Carolyn Bjerke Dave Roberts 《International journal of human-computer interaction》2013,29(3-4):535-558
This article provides an introduction to the usage of software engineering approaches and tools for the design of user experience (UE). This approach was developed for three main reasons: (a) to provide UE design teams a rigorous, methodical, encompassing method that can be applied throughout the entire product development cycle; (b) to provide designers a way to work with abstract concepts to establish the conceptual design of the system before progressing to the realization of the design to the appropriate platform; and (c) to communicate the intended design to the implementation team in a manner that is concise, complete, and familiar. The approach is the application of Unified Modeling Language concepts to describe users and the UE design rather than the technical architecture. It is believed that designing the UE design separately from the technical architecture will help ensure teams deliver a usable and delightful UE. The methods in this article have been applied to a handful of real-world projects in the last year and a half. Thus far, the application of software engineering approaches and tools have been found to be very powerful aids that have enabled the creation of highly useful Web experiences as well as software applications. Our intent is to address the full gamut of issues involved in creating a total user experience (UE)-from discovery of users needs through high-level and low-level design, ensuring fidelity during development, and deployment, with a full assessment of how well the design meets users' needs. We believe that through a concerted use of such a rigorous approach we can greatly improve not only the UE of products we create, but also the experience of designing and developing them. We are not the only team taking this direction in UE design. It has become clear to many in our field that a more rigorous, thorough, and accurate approach to UE design is not only possible-it is necessary, for many of the same reasons that software engineers long ago embraced such practices. As we are evolving our approaches in other phases, this article focuses on the discovery and design phase activities. 相似文献