全文获取类型
收费全文 | 10194篇 |
免费 | 142篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 89篇 |
综合类 | 4篇 |
化学工业 | 1229篇 |
金属工艺 | 162篇 |
机械仪表 | 227篇 |
建筑科学 | 280篇 |
矿业工程 | 55篇 |
能源动力 | 164篇 |
轻工业 | 693篇 |
水利工程 | 69篇 |
石油天然气 | 20篇 |
武器工业 | 1篇 |
无线电 | 749篇 |
一般工业技术 | 1339篇 |
冶金工业 | 4418篇 |
原子能技术 | 81篇 |
自动化技术 | 766篇 |
出版年
2022年 | 48篇 |
2021年 | 54篇 |
2020年 | 40篇 |
2019年 | 55篇 |
2018年 | 78篇 |
2017年 | 73篇 |
2016年 | 84篇 |
2015年 | 78篇 |
2014年 | 99篇 |
2013年 | 354篇 |
2012年 | 193篇 |
2011年 | 250篇 |
2010年 | 254篇 |
2009年 | 236篇 |
2008年 | 254篇 |
2007年 | 251篇 |
2006年 | 213篇 |
2005年 | 238篇 |
2004年 | 175篇 |
2003年 | 193篇 |
2002年 | 189篇 |
2001年 | 158篇 |
2000年 | 172篇 |
1999年 | 206篇 |
1998年 | 1235篇 |
1997年 | 812篇 |
1996年 | 541篇 |
1995年 | 393篇 |
1994年 | 348篇 |
1993年 | 355篇 |
1992年 | 134篇 |
1991年 | 142篇 |
1990年 | 143篇 |
1989年 | 165篇 |
1988年 | 150篇 |
1987年 | 111篇 |
1986年 | 103篇 |
1985年 | 124篇 |
1984年 | 114篇 |
1983年 | 92篇 |
1982年 | 85篇 |
1981年 | 77篇 |
1980年 | 92篇 |
1979年 | 80篇 |
1978年 | 90篇 |
1977年 | 174篇 |
1976年 | 325篇 |
1975年 | 62篇 |
1974年 | 63篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Yanqing Ji Hao Ying John Yen Shizhuo Zhu Daniel C. Barth‐Jones Richard E. Miller R. Michael Massanari 《国际智能系统杂志》2007,22(8):827-845
Discovering unknown adverse drug reactions (ADRs) in postmarketing surveillance as early as possible is highly desirable. Nevertheless, current postmarketing surveillance methods largely rely on spontaneous reports that suffer from serious underreporting, latency, and inconsistent reporting. Thus these methods are not ideal for rapidly identifying rare ADRs. The multiagent systems paradigm is an emerging and effective approach to tackling distributed problems, especially when data sources and knowledge are geographically located in different places and coordination and collaboration are necessary for decision making. In this article, we propose an active, multiagent framework for early detection of ADRs by utilizing electronic patient data distributed across many different sources and locations. In this framework, intelligent agents assist a team of experts based on the well‐known human decision‐making model called Recognition‐Primed Decision (RPD). We generalize the RPD model to a fuzzy RPD model and utilize fuzzy logic technology to not only represent, interpret, and compute imprecise and subjective cues that are commonly encountered in the ADR problem but also to retrieve prior experiences by evaluating the extent of matching between the current situation and a past experience. We describe our preliminary multiagent system design and illustrate its potential benefits for assisting expert teams in early detection of previously unknown ADRs. © 2007 Wiley Periodicals, Inc. Int J Int Syst 22: 827–845, 2007. 相似文献
2.
A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
3.
4.
Nitrification kinetics are important for process design, optimization, and capacity rating of activated sludge wastewater treatment plants. A Water Environment Research Foundation (WERF) project on Methods for Wastewater Characterization in Activated Sludge Modeling (WERF, 2003) focused significantly on the development of procedures for measuring the nitrifier maximum specific growth rate, micro(AUT). In addition, the importance of (and lack of data for) the nitrifier decay rate, b(AUT), was identified. This paper describes three bench-scale methods for measuring micro(AUT): the Low F/M SBR, Washout and High F/M methods. During the WERF project, the importance of pH and temperature control was investigated briefly; this paper summarizes further experimental work performed to address these issues. A summary of micro(AUT) measurements in a number of locations and using the different measurement techniques is provided. 相似文献
5.
Samuel L. Manzello Richard G. Gann Scott R. Kukuck Kuldeep Prasad Walter W. Jones 《火与材料》2007,31(5):297-310
A gypsum wall assembly was exposed to an intense real‐scale compartment fire. For the wall assembly, temperatures were measured at the exposed face, within the stud cavity, and at the unexposed face during the fire exposure. Total heat flux gauges were used to measure the temporal variation of the energy incident on the walls, and cameras, both visual and infrared, were used to image the unexposed face of the wall assembly during the fire exposure. The behaviour of the wall assembly under the fire load is discussed as are current model results for a simulation of the fire test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
6.
V. Elliott Smith John M. Spurr John C. Filkins Jody J. Jones 《Journal of Great Lakes research》1985,11(3):231-246
Organochlorine analysis was performed on carcasses of 13 diving ducks from a 1981 wintering population that foraged on contaminated sediments in the lower Detroit River. Mean total PCB concentrations were 10 mg/kg for seven lesser scaups (Aythya affinis), 11 mg/kg for three greater scaups (A. marila), and 7.6 mg/kg for three goldeneyes (Bucephala clangula). Highest mean levels of other residues were measured for hexachlorobenzene (1.7 mg/kg) in goldeneyes, and transnonachlor (0.33 mg/kg) and 4,4’-DDE (1.3 mg/kg) in greater scaup. Quantitative analysis of 72 PCB congeners also was applied to water, seston, sediment, benthie oligochaetes, and carp from the same site. Principal congeners in most of the samples included some of the more toxic and persistent PCBs. Results of a multivariate analysis indicated that ratios of more conservative to less conservative PCBs did not vary significantly among ducks (α = .05), but differed from those in carp, oligochaetes, and sediment. For the February through March period of fat mobilization, concentrations of total PCB in lipid were inversely correlated with percent lipid (r = 0.76) in ducks. The percentage of conservative PCBs increased slightly. The distribution and partitioning of organochlorines, including toxic PCB congeners, varied considerably within this water column-sediment-fauna ecosystem. Estimates of toxic exposure based on total PCB values may be unreliable. 相似文献
7.
Research on over 18 years of software projects reveals that developing large systems involves substantially more activities and a greater variety of specialized personnel than developing smaller systems. Perhaps the most significant observation is that good quality control is the best overall indicator of a successful project. Schedule delays and cost overruns most often occur when you discover during testing that the application has so many bugs that it doesn't work. Projects using QA teams, formal design and code inspections, and pretest defect tracking always had shorter testing cycles and therefore were more likely to be deliverable on schedule. 相似文献
8.
9.
P M Reid A E Wilkinson K C Leung M N Jones 《Computer applications in the biosciences》1989,5(2):133-135
Analytical ultracentrifugation is commonly used for the determination of molecular weights (sedimentation equilibrium) and sedimentation coefficients (sedimentation rate) of biological macromolecules in solution. A Turbo Pascal program for the analysis of sedimentation equilibrium centrifugation data produced by absorbance optical systems is described. The user may enter data from a scan of absorbance versus distance from the centre of rotation, via a graphics tablet (or ASCII file). This is subsequently manipulated to yield an apparent weight average molecular weight for the given sample. Plots of ln (absorbance) versus (radius2) may also be produced. The method described uses readily available computational equipment requiring only a graphics tablet in addition to an IBM PC compatible computer. This technique and the software developed have been used to investigate the molecular weight range of two International Humic Substances Society (IHSS) reference samples from the Suwannee River. 相似文献
10.
A card survey was sent to 340 veterinarians in the Urban, Delta, Highland and Coastal Plain regions of Arkansas. Veterinarians were asked to indicate numbers of dogs tested, confirmed Dirofilaria immitis positive, diagnostic techniques, frequency and period tested. A significantly greater percentage of dogs tested D. immitis positive in the Delta region as compared with the Urban region. There were no significant differences in the percentage of treated dogs on prophylaxis or the types of diagnostic tests among regions. 相似文献