全文获取类型
收费全文 | 1950篇 |
免费 | 86篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 21篇 |
综合类 | 3篇 |
化学工业 | 534篇 |
金属工艺 | 66篇 |
机械仪表 | 42篇 |
建筑科学 | 90篇 |
矿业工程 | 12篇 |
能源动力 | 49篇 |
轻工业 | 127篇 |
水利工程 | 9篇 |
石油天然气 | 6篇 |
无线电 | 144篇 |
一般工业技术 | 396篇 |
冶金工业 | 235篇 |
原子能技术 | 10篇 |
自动化技术 | 296篇 |
出版年
2024年 | 6篇 |
2023年 | 22篇 |
2022年 | 88篇 |
2021年 | 83篇 |
2020年 | 46篇 |
2019年 | 49篇 |
2018年 | 47篇 |
2017年 | 63篇 |
2016年 | 72篇 |
2015年 | 51篇 |
2014年 | 75篇 |
2013年 | 122篇 |
2012年 | 113篇 |
2011年 | 110篇 |
2010年 | 109篇 |
2009年 | 81篇 |
2008年 | 100篇 |
2007年 | 91篇 |
2006年 | 66篇 |
2005年 | 61篇 |
2004年 | 46篇 |
2003年 | 37篇 |
2002年 | 42篇 |
2001年 | 27篇 |
2000年 | 37篇 |
1999年 | 15篇 |
1998年 | 54篇 |
1997年 | 26篇 |
1996年 | 35篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 18篇 |
1992年 | 10篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1971年 | 6篇 |
排序方式: 共有2040条查询结果,搜索用时 15 毫秒
71.
Fatty Acid, Tocopherol and Sterol Compositions of Canadian Prairie Fruit Seed Lipids 总被引:1,自引:1,他引:1
Farooq Anwar Roman Przybylski Magdalena Rudzinska Eliza Gruczynska John Bain 《Journal of the American Oil Chemists' Society》2008,85(10):953-959
The seeds of four prairie fruits—chokecherry (Prunus virginiana), thorny buffaloberry (Shepherdia argentea), Woods’ rose (Rosa woodsii) and hawthorn (Crataegus × mordenensis)—from Southern Alberta were investigated. The lipid contents of the seeds were found to be 10.4, 11.5, 3.7 and 3.4%, respectively.
The tested seed lipids contained mainly linoleic acid in the range from 27.9 to 65.6% and oleic acid from 19.7 to 61.9%. The
thorny buffaloberry and Woods’ rose seed lipids contained 29.2 and 30.8% of linolenic acid, respectively. The contents of
palmitic and stearic acids ranged from 3.2 to 5.4% and 1.6 to 2.2%, respectively. The contents of total tocopherols in the
chokecherry, thorny buffaloberry, Woods’ rose and hawthorn seed lipids accounted for 595, 897, 2,358 and 2,837 mg/kg, respectively.
The main sterols in the lipids were β-sitosterol, Δ5-avenasterol, cycloartenol, campesterol, stigmasterol and gramisterol. The results of the present study show that the lipids
from the seeds of the investigated prairie fruits could be a good source of valuable essential fatty acids, tocopherols and
sterols, thus suggesting their application as functional foods and nutraceuticals. 相似文献
72.
A selection of WC-Co and Cr3C2-25%NiCr coatings deposited by plasma spraying and high velocity oxygen fuel (HVOF) were tested. The microstructures of the
coatings were characterized, and their mechanical properties were assessed using Knoop microindentation procedures. The coatings
were also subjected to various wear tests. All of the coatings were at least 200 μm thick and were deposited onto stainless
steel substrates. The wear tests simulated abrasion, cavitation wear, sliding wear, and particle erosion wear.
In this first part of a two-part contribution, the microstructures of the coatings are characterized and a discussion on the
evaluation of mechanical properties from the microindentation response is presented. The nature of microhardness testing as
applied to thermal spray coatings is evaluated as a means of assessing resistance to plastic flow, elasticity, and brittleness.
In Part 2, the results of the various wear simulations are reported, and the utility of microhardness as an indicator of wear
resistance is examined. 相似文献
73.
Krzysztof M. Tokarz Wojciech Wesoowski Barbara Tokarz Wojciech Makowski Anna Wysocka Roman J. Jdrzejczyk Karolina Chrabaszcz Kamilla Malek Anna Kostecka-Gugaa 《International journal of molecular sciences》2021,22(2)
Grass pea (Lathyrus sativus) is a leguminous plant of outstanding tolerance to abiotic stress. The aim of the presented study was to describe the mechanism of grass pea (Lathyrus sativus L.) photosynthetic apparatus acclimatisation strategies to salinity stress. The seedlings were cultivated in a hydroponic system in media containing various concentrations of NaCl (0, 50, and 100 mM), imitating none, moderate, and severe salinity, respectively, for three weeks. In order to characterise the function and structure of the photosynthetic apparatus, Chl a fluorescence, gas exchange measurements, proteome analysis, and Fourier-transform infrared spectroscopy (FT-IR) analysis were done inter alia. Significant differences in the response of the leaf and stem photosynthetic apparatus to severe salt stress were observed. Leaves became the place of harmful ion (Na+) accumulation, and the efficiency of their carboxylation decreased sharply. In turn, in stems, the reconstruction of the photosynthetic apparatus (antenna and photosystem complexes) activated alternative electron transport pathways, leading to effective ATP synthesis, which is required for the efficient translocation of Na+ to leaves. These changes enabled efficient stem carboxylation and made them the main source of assimilates. The observed changes indicate the high plasticity of grass pea photosynthetic apparatus, providing an effective mechanism of tolerance to salinity stress. 相似文献
74.
75.
Konstantin V. Pochivalov Alexander N. Shilov Tatyana N. Lebedeva Anna N. Ilyasova Roman Yu. Golovanov Andrey V. Basko Yaroslav V. Kudryavtsev 《应用聚合物科学杂志》2021,138(15):50196
A detailed study of butyl rubber-based vibration damping formulations linking their composition, morphology, phase structure, viscosity, mechanical loss factor, and other characteristics is presented for the first time. High performance of the compositions including aromatic petroleum oil is explained by limited solubility of the plasticizer that leads to the formation of a highly-viscous emulsion (η20°C ≈ 1000 Pa·s) consisting of a swollen butyl rubber matrix and dispersed oil droplets in the broad composition range. Chalk is found to be the best inorganic filler as its spherical particles provide strong adhesion to the reinforcing layer of aluminum foil. Aiming to eliminate ecologically unfriendly aromatic compounds, a new low-cost binding agent formulation based on butyl rubber mixed with polyisobutylene and highly refined mineral oil is suggested. Being environmentally safe, it possesses high viscosity of 1000–3000 Pa·s, cohesion strength of 3.5–5.0 N/cm, penetration of 4.5–6.0 mm, and mechanical loss factor up to 0.34 at room temperature, which are as good as, or even better than, the properties of currently produced vibration damping materials containing aromatic compounds. New materials can be used in car and aircraft parts for effective vibration isolation. 相似文献
76.
Microstructure,Phase Occurrence,and Corrosion Behavior of As-Solidified and As-Annealed Al-Pd Alloys
Libor Ďuriška Marián Palcut Martin Špoták Ivona Černičková Ján Gondek Pavol Priputen Roman Čička Dušan Janičkovič Jozef Janovec 《Journal of Materials Engineering and Performance》2018,27(4):1601-1613
In the present work, we studied the microstructure, phase constitution, and corrosion performance of Al88Pd12, Al77Pd23, Al72Pd28, and Al67Pd33 alloys (metal concentrations are given in at.%). The alloys were prepared by repeated arc melting of Al and Pd granules in argon atmosphere. The as-solidified samples were further annealed at 700 °C for 500 h. The microstructure and phase constitution of the as-solidified and as-annealed alloys were studied by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. The alloys were found to consist of (Al), ε n (~ Al3Pd), and δ (Al3Pd2) in various fractions. The corrosion testing of the alloys was performed in aqueous NaCl (0.6 M) using a standard 3-electrode cell monitored by potentiostat. The corrosion current densities and corrosion potentials were determined by Tafel extrapolation. The corrosion potentials of the alloys were found between ? 763 and ? 841 mV versus Ag/AgCl. An active alloy dissolution has been observed, and it has been found that (Al) was excavated, whereas Al in ε n was de-alloyed. The effects of bulk chemical composition, phase occurrence and microstructure on the corrosion behavior are evaluated. The local nobilities of ε n and δ are discussed. Finally, the conclusions about the alloy’s corrosion resistance in saline solutions are provided. 相似文献
77.
Lyudmila L. Lyubimova Roman N. Fisenko Alexander A. Tashlykov Roman B. Tabakaev 《Metals and Materials International》2018,24(1):121-129
This work deals with the problems of structural regeneration by thermal restoration treatment (TRT). These include the lack of a structural sign showing that TRT is possible, a consensus on TRT modes, the data on the necessary relaxation depth of residual stresses, or criteria of structural restoration. Performing a TRT without solving these problems may deteriorate the properties of steel or even accelerate its destruction. With this in view, the purpose of this work is to determine experimentally how the residual stress state changes under thermal and mechanical loads in order to specify the signs of the restoration of structure and structural stability. The object of this research is unused 12Cr1MoV steel that has been aged naturally for 13 years. Using X-ray dosimetry with X-ray spectral analysis, we study the distribution of internal residual stresses of the first kind during the repeated hot deformation. After repeated thermal deformation, the sample under study transforms from a viscoelastic Maxwell material into a Kelvin-Voigt material, which facilitates structural stabilization. A sign of this is the relaxation limit increase, prevention of continuous decay of an α-solid solution of iron and restoration of the lattice parameter. 相似文献
78.
Summary The IIW method is shown to be one of the most precise and that it may be programmed to advantage. 相似文献
79.
80.