全文获取类型
收费全文 | 169篇 |
免费 | 9篇 |
专业分类
化学工业 | 61篇 |
金属工艺 | 1篇 |
机械仪表 | 2篇 |
建筑科学 | 10篇 |
能源动力 | 8篇 |
轻工业 | 16篇 |
石油天然气 | 12篇 |
无线电 | 4篇 |
一般工业技术 | 13篇 |
冶金工业 | 24篇 |
自动化技术 | 27篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 8篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 14篇 |
2008年 | 6篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 2篇 |
2004年 | 6篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1933年 | 2篇 |
排序方式: 共有178条查询结果,搜索用时 12 毫秒
31.
Simon Ivar Andersen 《Petroleum Science and Technology》2013,31(11-12):1551-1577
ABSTRACT Solid petroleum asphaltenes have been fractionated according to solubility in toluene/n-heptane mixtures of increasing toluene content. A large hysteresis was observed between this dissolution and the precipitation from the crude oil. In order to shed light on the solution mechanism, the fractions obtained have been analyzed using size exclusion chromatography (SEC-HPLC-UV-vis), VPO, elemental analysis, UV-vis adsorption spectroscopy and phenol interaction values and methylene content by FTir. Less polar non-associating low molecular weight species are dissolved and a specific extraction of porphyrins is observed. An increased association in the insolubles is indicated. More basic interaction sites are available on the asphaltenes in both fractions relative to the native asphaltene. From the SEC chromatograms it was seen that the soluble fractions did not associate as the insoluble fractions even when making up more than 60 % of the total asphaltenes. 相似文献
32.
Artur Noole Maksim Oeka Tnis Pehk Mario
eren Ivar Jrving Mark R. J. Elsegood Andrei V. Malkov Margus Lopp Tnis Kanger 《Advanced Synthesis \u0026amp; Catalysis》2013,355(5):829-835
3‐Chlorooxoindoles have emerged as versatile precursors in the synthesis of spirocyclopropyl oxindoles. High enantio‐ and diastereoselectivity was attained under conditions of both iminium/enamine and H‐bonding catalysis. 相似文献
33.
Ivar Kruusenberg 《Carbon》2009,47(3):651-280
The pH-dependence of oxygen electroreduction has been investigated on multi-walled carbon nanotube (MWCNT) modified glassy carbon (GC) electrodes. Various surfactants were used in the electrode modification: dihexadecyl hydrogen phosphate, cetyltrimethylammonium bromide, sodium dodecyl sulfate and Triton X-100. Electrochemical experiments were carried out in 0.5 M H2SO4 solution, acetate buffer (pH 5), phosphate buffers (pH 6, 7 and 8), borate buffer (pH 10), 0.01 M KOH, 0.1 M KOH and in 1 M KOH solution, using the rotating disk electrode (RDE) method. The oxygen reduction behaviour of MWCNT-modified GC electrodes at different pHs was compared. The RDE results revealed that the half-wave potential (E1/2) of oxygen reduction was higher in solutions of high pH. At lower pHs (pH < 10) the value of E1/2 did not essentially depend on the solution pH. A comparison with previous studies on bare GC showed that the pH-dependence of the half-wave potential of oxygen reduction on MWCNT-modified GC electrodes follows a similar trend to that observed for bare GC. 相似文献
34.
Mechanical and optical properties in precipitated regions of alumina‐rich magnesium aluminate spinel 下载免费PDF全文
Jesse Miller Ivar Reimanis Weiguo Miao Jonathan Salem 《International Journal of Applied Ceramic Technology》2017,14(2):236-244
The toughening and strengthening of transparent ceramics is challenging because microstructural alterations typically lead to light scattering. Here, controlled precipitation of α‐Al2O3 from nonstoichiometric spinel is explored to demonstrate unique control over the evolution of second phase Al2O3 and how the microstructure might be altered to enhance fracture toughness while minimizing light scatter. Alumina‐rich magnesium aluminate spinel, MgO·nAl2O3, where n=2, was hot pressed and HIPed to produce fully dense, single‐phase material. The material was then heat treated in air at 1573 K for up to 20 hours to create a two‐phase spinel‐Al2O3 composite. The fracture toughness varies from 0.88 to 2.47 MPa√m depending on the microstructure; enhanced toughness at the surface was due to increased crack tortuosity at phase boundaries, but residual tensile stresses were observed in the interior of the material. Precipitation causes local volume contraction and the formation of porosity, decreasing optical transmission, especially for heat treatment times longer than 5 hours. 相似文献
35.
Prashant S. Salimath Ivar S. Ertesvåg 《International Journal of Hydrogen Energy》2021,46(52):26616-26630
Premixed H2-air flames are studied in a one-dimensional wall-bounded configuration. The laminar flame propagates towards and quenches at a wall that is either solid or permeable. Entropy generation by each of 19 elementary reactions is evaluated. Their total contribution remains the most important up to the quenching instance. Close to quenching, the conduction entropy generation grows considerable. Mass diffusion has a modest contribution, which decreases towards quenching. Viscous forces are negligible as a source of entropy. Effects of unburnt-mixture temperature and fuel-air ratio are investigated, and also dilution with nitrogen (inert) and water vapour. The diffusive entropy flux changed direction away from the permeating wall compared that of the solid wall. A major finding is that fuel permeation through the wall tends to decrease the entropy generation per unit of converted fuel, in particular for initially lean mixtures. 相似文献
36.
Lovaas (see record 1987-16420-001) has been criticized for overstating the outcome of an intensive behavioral intervention for young autistic children. Part of the criticism reflects skepticism of Lovaas's view that it is possible to overcome autistic children's deficits. However, Lovaas's study built on a substantial body of research that has suggested just such a possibility. It also contained a number of methodological features that provide evidence supporting his interpretation of the outcome, notably, unbiased control groups and multiple pretreatment and follow-up measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
37.
Ivar E. Reimanis John J. Petrovic Hisayuki Suematsu Terrence E. Mitchell 《Journal of the American Ceramic Society》1996,79(2):395-400
A composite consisting of elongated α-Si3 N4 crystallites (5–50 (Am in diameter) embedded in an amorphous Si3 N4 matrix was synthesized by chemical vapor deposition. The hardness and indentation fracture toughness of the amorphous matrix and of the composite have been evaluated at temperatures from ambient to 1200°C. It was found that the crystallites have relatively little influence on the hardness and indentation fracture toughness when the surrounding matrix is amorphous. However, a 1400°C heat treatment of the material results in a matrix consisting of small crystals (100 nm in diameter) surrounded by carbon-containing regions which appear to be amorphous in the TEM; TEM and EELS in nearby triple points revealed the presence of amorphous carbon. After heat treatment, the indentation fracture toughness at ambient and at 1200°C is increased due to extensive microcracking. The Vickers hardness at 1200°C also increased significantly as a result of the heat treatment. The relationship between the mechanical properties and the microstructure is discussed. 相似文献
38.
Plant availability of inorganic and organic selenium fertiliser as influenced by soil organic matter content and pH 总被引:11,自引:0,他引:11
Susanne Eich-Greatorex Trine A. Sogn Anne Falk Øgaard Ivar Aasen 《Nutrient Cycling in Agroecosystems》2007,79(3):221-231
The objective of the present study was to investigate the influence of soil organic matter content and pH on plant availability
of both inorganic and organic selenium (Se) fertilisers. Further, the risk of Se leaching after application of inorganic Se
fertiliser was evaluated. A new interpretation of an older field study at different sites in Southern Norway showed that organic
C was correlated with grain Se concentration in wheat, barley and oats, explaining up to 60% of the variation in Se concentration.
Pot experiments with a peat soil, a loam soil and a peat/loam soil mixture were conducted for the present study at a range
of pH values between pH 5 and 7. Below pH 6, Se uptake from added Se fertiliser was higher in the soil types with high organic
matter content than in the loam. The opposite occurred at a soil pH above 6, where Se uptake was higher in the loam than in
the peat soil. A simple leaching experiment after one growing season confirmed the findings of the pot experiments that Se
availability in the loam soil with a relatively low organic matter content increased with increasing pH, whereas it decreased
in the peat soil. Neither Se yeast, nor pure Se methionine, used as organic Se fertiliser, resulted in any significant uptake
of Se when added at concentrations similar to the inorganic Se applications. 相似文献
39.
Ivar Sagefors Per-Anders Daerga 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1996,11(3):279-285
Construction of underground storage chambers in rock has traditionally adopted a construction-oriented approach; the cavern design and the method of excavation have been governed by the capabilities of the equipment available. One example is oil storage in unlined horizontal caverns. Today, however, equipment is no longer a limiting factor. The time has come to integrate the construction and operational aspects in the design process. This paper presents a construction concept developed for large vertical rock caverns with a circular or elliptical horizontal cross-section. The method of excavation, called PBM (Pillar Blasting Method), is condensed into a few main operations which are geometrically separated but overlapping in time. PBM is characterized by two main working sites per cavern, and by long-hole bench-drilling, massive blasting rounds, continuous loading and easy ventilation. Recent developments in drilling and blasting techniques are incorporated, such as the water-driven in-the-hole hammer and the electronic ignition system. PBM enables a high rate of excavation and provides a satisfactory working environment with respect to labour safety and human health (a limited exposure to large openings, no exposure to oil mist and to combustion and explosive fumes, etc). Considerable construction cost savings and time savings may thus be achieved compared to conventional methods of excavation for vertical and horizontal caverns of equal storage volume. A preliminary PCT patent (application No PCT/SE95/00324) has been granted. Examples of applications are fresh-water reservoirs, natural gas reservoirs, subsurface hydroelectric pump power plants, and similar objects which require a large underground storage space in preferably unlined rock caverns. 相似文献
40.
Simon Ivar Andersen Carlos Lira-Galeana Erling H. Stenby 《Petroleum Science and Technology》2001,19(3):457-467
In the evaluation of experimental data as well as in calculation of phase equilibria the necessity of the application of mass balances is obvious. In the case of asphaltenes the colloidal nature of these compounds may highly affect the mass balance. In the present paper several experiments are performed in order to check the consistency of mass balances within asphaltene precipitation. Asphaltenes are precipitated in two step processes either by changing temperature or by changes in precipitant with increasing precipitation power. This has been performed for three different oils. The data indicates that in temperature experiments as well as in solvent series experiments the precipitation of heavy asphaltenes affects the following precipitation of lighter asphaltenes. In both cases the mass balance using standard separation techniques cannot be closed, as less material is precipitated in a two step process than in the direct process either at low temperature or by direct precipitation with one precipitant. The different fractions were subject to HPLC size exclusion chromtagraphy showing that the material remaining in solution in the stepwise process was of low molecular weight, and that the material in the second precipitation step was often of higher apparent molecular weight and had an increased overall absorbance coefficient. 相似文献