全文获取类型
收费全文 | 8985篇 |
免费 | 414篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 120篇 |
综合类 | 38篇 |
化学工业 | 2268篇 |
金属工艺 | 226篇 |
机械仪表 | 189篇 |
建筑科学 | 601篇 |
矿业工程 | 22篇 |
能源动力 | 281篇 |
轻工业 | 915篇 |
水利工程 | 88篇 |
石油天然气 | 43篇 |
武器工业 | 1篇 |
无线电 | 665篇 |
一般工业技术 | 1464篇 |
冶金工业 | 588篇 |
原子能技术 | 59篇 |
自动化技术 | 1842篇 |
出版年
2023年 | 85篇 |
2022年 | 203篇 |
2021年 | 334篇 |
2020年 | 185篇 |
2019年 | 202篇 |
2018年 | 273篇 |
2017年 | 236篇 |
2016年 | 317篇 |
2015年 | 235篇 |
2014年 | 338篇 |
2013年 | 630篇 |
2012年 | 486篇 |
2011年 | 616篇 |
2010年 | 430篇 |
2009年 | 498篇 |
2008年 | 455篇 |
2007年 | 413篇 |
2006年 | 345篇 |
2005年 | 295篇 |
2004年 | 275篇 |
2003年 | 260篇 |
2002年 | 194篇 |
2001年 | 138篇 |
2000年 | 137篇 |
1999年 | 114篇 |
1998年 | 140篇 |
1997年 | 139篇 |
1996年 | 107篇 |
1995年 | 79篇 |
1994年 | 84篇 |
1993年 | 84篇 |
1992年 | 61篇 |
1991年 | 61篇 |
1990年 | 62篇 |
1989年 | 70篇 |
1988年 | 49篇 |
1987年 | 51篇 |
1986年 | 56篇 |
1985年 | 57篇 |
1984年 | 62篇 |
1983年 | 50篇 |
1982年 | 44篇 |
1981年 | 39篇 |
1980年 | 44篇 |
1978年 | 38篇 |
1977年 | 35篇 |
1976年 | 44篇 |
1975年 | 40篇 |
1974年 | 36篇 |
1973年 | 37篇 |
排序方式: 共有9410条查询结果,搜索用时 15 毫秒
31.
Jan A. Derecki 《Journal of Great Lakes research》1985,11(3):201-207
Periodic man-made changes in the outlet of Lake Huron through the St. Clair River date back to the middle of the last century. These artificial channel changes have been well documented during the present century. They consist of dredging for commercial gravel removal in the upper river during 1908–25 and uncompensated navigation improvements for the 7.6-m (25-ft) and 8.2-m (27-ft) projects completed in 1933 and 1962, respectively. The total effect of these changes on the levels of Lakes Michigan and Huron (hydraulically one lake) and on the upper St. Clair River profile was determined with dynamic flow models. The ultimate effect of the above dredging was a permanent lowering of the Lake Michigan-Huron levels 0.27 m (0.89 ft), which represents a tremendous loss of freshwater resource [32 km3 (7.7 mi3)]. 相似文献
32.
33.
P. Balle H. Bockhorn B. Geiger N. Jan S. Kureti D. Reichert T. Schrder 《Chemical Engineering and Processing: Process Intensification》2006,45(12):1065-1073
This study deals with the development of a laboratory bench for the practical evaluation of catalysts that are useful for the direct conversion of NOx and soot in the exhaust of diesel engines. The employed model exhaust is generated by using a diffusion burner with additionally dosing some gaseous components to the burner gas to obtain a realistic feed composition. The produced soot is extensively characterized by employing thermogravimetry, transmission electron microscopy, N2 physisorption and temperature programmed techniques. The results of the different characterization methods show that the present soot is suitable for the intended catalytic investigations. The simultaneous conversion of NOx and soot is examined like in practice, i.e. the soot is separated from the tail gas by a diesel particulate filter (DPF) that is coated with the catalyst. The deposited soot is then catalytically converted by NOx and O2 to form N2 and CO2. The conversions of NOx and soot are measured by exclusively applying gas analysers, whereby a special experimental procedure is developed to determine the soot removal. Hence, additional soot related analytics are not required. To show the suitability of the constructed bench a Pt/Fe2O3/β-zeolite sample is taken as test catalyst that is reported to be very active in NOx/soot reaction. The measurements performed with and without catalyst clearly show the effect of the used sample in simultaneous NOx/soot conversion. We therefore consider the constructed laboratory bench to be a useful tool for testing and ranking catalytic materials. 相似文献
34.
This paper presents work directed at capturing the entrepreneurial and collaborative activity of university researchers. The Triple Helix points to the emergence of the entrepreneurial university as well as to an increasing overlay of activities in universities, industry and government. This study explores ways in which patent-based metrics could be utilized in a Triple Helix context, and how hybrid indicators could be developed by combining patent with survey data. More specifically, it aims to develop indicators that connect technological inventiveness of university researchers to both funding organizations and users, as well as to entrepreneurial activities by academics. The paper develops a simplified model of the innovation process to benchmark the relevance of the indicators to the Triple Helix. An analysis of Finnish academic patents illustrates that patent data can already provide useful indicators but, on its own, cannot provide information about how academic patents are interconnected with government or industry through funding or utilization links. An exclusive analysis of patents can point to patent concentrations on certain universities, to inventors and assignees, or to potential gaps in translating applied science into industrial technology. However, the patent data had to be combined with an inventor survey in order to relate academic patents more to their Triple Helix environment. The survey indicated that most patented academic inventions are connected to (often publicly funded) scientific research by the inventors and tend to be utilized in large firms rather than in start-up companies founded by academic entrepreneurs. 相似文献
35.
36.
The Steady radial distribution of chemical species in a wire‐to‐cylinder ozone generator filled with pure oxygen has been computed by applying four different plasma chemistry models of increasing complexity. The most complete model considers ten species (e, O2 +, O2 ?, O3 ?, O?, O2, O2(1Δg), O2(1∑g +), O and O3) and 79 reactions, including ionization by electron impact, electron attachment and detachment, electron-ion recombination, charge transfer, etc. The chemical model is coupled with the electrical model through Poisson's equation. The spatially averaged ozone density has been computed as a function of the current intensity and compared with the experimental values obtained by UV spectroscopy. 相似文献
37.
van Gelderen Amos; Schoonen Rob; de Glopper Kees; Hulstijn Jan; Simis Annegien; Snellings Patrick; Stevenson Marie 《Canadian Metallurgical Quarterly》2004,96(1):19
The authors report results of a study into the role of components of first-language (L1; Dutch) and second-language (L2; English) reading comprehension. Differences in the contributions of components of L1 and L2 reading comprehension are analyzed, in particular processing speed in L1 and L2. Findings indicate that regression weights of the L1 and L2 components are different. Although correlations between most processing speed components and reading comprehension are substantial, there are no unique contributions to the explanation of either L1 or L2 reading comprehension when linguistic and metacognitive knowledge are accounted for. In addition, L1 reading comprehension is shown to have a large contribution to L2 reading comprehension, supporting theories of L1-L2 transfer of reading skills. Results are discussed from a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
Sialon ceramics are a modern type of engineering ceramics with excellent mechanical, thermal and corrosion resistant properties. This paper describes the structure characterisation of porous sialon ceramics. It is possible to significantly improve the strength and crack resistance of sialon ceramics as a result of a reduction of the volume fraction of porosity. 相似文献
39.
Jan Paca Eva Klapkova Martin Halecky Kim Jones Carlos Riccardo Soccol 《Clean Technologies and Environmental Policy》2007,9(1):69-74
The removal of a mixture of painting solvents from waste air using a biofiltration process was evaluated in this project.
The pollutants removed included hydrophobic (aromatic hydrocarbons) and hydrophilic (water soluble ketones and esters) compounds.
A trickle bed reactor with a defined immobilized mixed culture on polyethylene Pall rings was utilized in this biodegradation
study. The removal efficiencies (RE) of the individual groups of pollutants during loading experiments were determined. An
increase of the aromatic hydrocarbons loading resulted in a drop of their REAROM with no effect on the RE value of ketones. The overloading of ketones caused a rapid drop in REAROM and a small drop in REKET. To achieve a restoration of the biocatalyst degradation properties after the increase in loading, an addition of phosphate
to the aqueous medium was implemented which successfully restored the removal efficiency. 相似文献
40.
In electrophotographic printing, a periodic clustered-dot halftone pattern is preferred for a smooth and stable result. In addition, the screen frequency should be high enough to minimize the visibility of the halftone textures and to ensure good detail rendition. However, at these frequencies, the halftone cell may contain too few pixels to provide a sufficient number of distinct gray levels. This will result in contouring and posterization. The traditional solution is to grow the clusters asynchronously within a repeating block of clusters known as a supercell. The growth of each individual cluster is governed by a microscreen. The order in which the clusters grow within the supercell is determined by a macroscreen. Typically, the macroscreen is a recursive pattern due to Bayer. In highlights and shadows, this ordering results in visible artifacts. Replacing the Bayer screen by a stochastic macroscreen eliminates these artifacts, but results in new artifacts. In this paper, we propose a new composite screen architecture that employs multiple microscreens and multiple macroscreens in the highlights and shadows. These screens are jointly designed by using the direct binary search (DBS) algorithm. 相似文献