全文获取类型
收费全文 | 3448篇 |
免费 | 71篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 37篇 |
综合类 | 6篇 |
化学工业 | 484篇 |
金属工艺 | 96篇 |
机械仪表 | 81篇 |
建筑科学 | 126篇 |
矿业工程 | 12篇 |
能源动力 | 60篇 |
轻工业 | 264篇 |
水利工程 | 36篇 |
石油天然气 | 4篇 |
无线电 | 349篇 |
一般工业技术 | 414篇 |
冶金工业 | 1177篇 |
原子能技术 | 17篇 |
自动化技术 | 359篇 |
出版年
2021年 | 41篇 |
2019年 | 21篇 |
2018年 | 33篇 |
2017年 | 32篇 |
2016年 | 37篇 |
2015年 | 32篇 |
2014年 | 41篇 |
2013年 | 125篇 |
2012年 | 89篇 |
2011年 | 126篇 |
2010年 | 91篇 |
2009年 | 94篇 |
2008年 | 112篇 |
2007年 | 116篇 |
2006年 | 108篇 |
2005年 | 115篇 |
2004年 | 80篇 |
2003年 | 80篇 |
2002年 | 84篇 |
2001年 | 73篇 |
2000年 | 69篇 |
1999年 | 87篇 |
1998年 | 273篇 |
1997年 | 173篇 |
1996年 | 124篇 |
1995年 | 93篇 |
1994年 | 89篇 |
1993年 | 77篇 |
1992年 | 50篇 |
1991年 | 32篇 |
1990年 | 66篇 |
1989年 | 63篇 |
1988年 | 54篇 |
1987年 | 48篇 |
1986年 | 45篇 |
1985年 | 44篇 |
1984年 | 47篇 |
1983年 | 39篇 |
1982年 | 39篇 |
1981年 | 36篇 |
1980年 | 31篇 |
1979年 | 28篇 |
1978年 | 23篇 |
1977年 | 41篇 |
1976年 | 72篇 |
1975年 | 21篇 |
1974年 | 25篇 |
1973年 | 22篇 |
1972年 | 20篇 |
1971年 | 23篇 |
排序方式: 共有3522条查询结果,搜索用时 368 毫秒
61.
F.H. Scholes S.A. Furman A.E. Hughes T. Nikpour N. Wright P.R. Curtis C.M. Macrae S. Intem A.J. Hill 《Progress in Organic Coatings》2006
Leaching and characterisation studies have been undertaken on two chromate-inhibited epoxy polyamide primers. Leaching was carried out in 5% (w/v) NaCl solutions at different pH values (1, 3, 5 and 7) and the amount of Cr released into solution was monitored over time. Cr release was initially high, but as the immersion time increased the leaching from the primers slowed. Prior to and after immersion, the primers were characterised by a number of techniques including electron microprobe analysis, X-ray microdiffraction, Raman spectroscopy, and positron annihilation lifetime spectroscopy. The unexposed primers were found to contain the inorganic phases SrCrO4, BaSO4 and TiO2 (anatase or rutile). Upon immersion, water uptake by the primers was observed, together with a decrease in the amount of SrCrO4 in the primers. These studies provide insights into the mechanism of chromate leaching from inhibited primers. 相似文献
62.
Effect of DAG on milk fat TAG crystallization 总被引:1,自引:0,他引:1
Amanda J. Wright Alejandro G. Marangoni 《Journal of the American Oil Chemists' Society》2002,79(4):395-402
The effect of milk fat and standard DAG on the crystallization behavior of milk fat TAG (MF-TAG) was investigated. When milk
fat DAG were added to MF-TAG at the 0.1 wt% level, crystallization was delayed. Racemic purity was shown to be an important
factor in the ability of DAG to influence TAG crystallization. Only sn-1,2 isomers of blends of MF-TAG with 0.1 wt% of the racemic mixtures of dipalmitin and diolein increased the activation free
energy barrier to MF-TAG nucleation (ΔG
c
) and delayed the subsequent crystallization process by increasing the crystallization induction time (τSFC) determined from solid fat content-time measurements. Although crystallization kinetics were affected, the properties of
the resulting network structures remained unchanged upon addition of milk fat minor components at the 0.1 wt% level 相似文献
63.
R. F. N. Hutchins O. R. W. Sutherland C. Gnanasunderam W. J. Greenfield E. M. Williams H. J. Wright 《Journal of chemical ecology》1984,10(1):81-93
Crude extracts of root of the forage legumesLotus pedunculatus andCoronilla varia (crownvetch) were toxic when administered orally to 3rd instarCostelytra zealandica larvae. A group of 3-nitropropanoyl-d-glucopyranoses was isolated from active fractions of the crude extracts. These toxins, some of which were already known fromC. varia, have not previously been reported fromL. pedunculatus. The compounds were present in root tissue of this species at a concentration of about 1% dry weight. They include the triester karakin and the diesters coronarian and cibarian, all of which were toxic to larvae ofC. zealandica at levels which could account fully for the activity of the crude extracts. 相似文献
64.
The early stages in the formation of a continuous anodic layer of bismuth oxide on a solid bismuth electrode, in the pH range 5–14, were studied. The oxide covered the surface by the simultaneous thickening and spreading of patches. The metal surface was classified into two different areas with different overvoltage for oxide nucleation. The ratio of the two areas varied according to the history of the surface.The thickening of the newly formed layer (final thickness ~20 nm) followed the high-field growth law i = exp(B) where is the field in the oxide layer, with B = (2.0 ± 0.5) × 10?6 V?1 cm. This value of B gives an activation distance for high-field ion transport of 0.2 nm, comparable to the radius of a lattice site and much smaller than that obtained previously, for much thicker films.Dissolution of the film, giving breakdown of the oxide layer and pitting of the metal, occurred for pH<8. The thickness of the anodic film was thus limited to only 4 nm at pH 5.Cathodic reduction of the anodic oxide resulted in a porous metal surface. The current—voltage curve for the reduction often had a complex shape, which was related to the morphology of the original anodic layer. 相似文献
65.
T. S. Wilson J. P. Bearinger J. L. Herberg J. E. Marion III W. J. Wright C. L. Evans D. J. Maitland 《应用聚合物科学杂志》2007,106(1):540-551
Aliphatic urethane polymers have been synthesized and characterized, using monomers with high molecular symmetry, to form amorphous networks with very uniform supermolecular structures, which can be used as photo‐thermally actuable shape memory polymers (SMPs). The monomers used include hexamethylene diisocyanate (HDI), trimethylhexamethylenediamine (TMHDI), N,N,N′,N′‐tetrakis(hydroxypropyl)ethylenediamine (HPED), triethanolamine (TEA), and 1,3‐butanediol (BD). The new polymers were characterized by solvent extraction, NMR, XPS, UV/VIS, DSC, DMTA, and tensile testing. The resulting polymers were found to be single phase amorphous networks with very high gel fraction, excellent optical clarity, and extremely sharp single glass transitions in the range of 34–153°C. Thermomechanical testing of these materials confirms their excellent shape memory behavior, high recovery force, and low mechanical hysteresis (especially on multiple cycles), effectively behaving as ideal elastomers above Tg. We believe these materials represent a new and potentially important class of SMPs, and should be especially useful in applications such as biomedical microdevices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
66.
Sharks are the most dangerous predators of people in the sea, resulting in people being mauled and killed each year. A shark
repellent could help to diminish this danger. The aglycone of the shark repellent pavoninin-5, (25R)-cholest-5-en-3β,15α,26-triol (5a), was synthesized from diosgenin (9). Removing mercury from the Clemmensen reduction of 9 gave a higher yield of (25R)-cholest-5-en-3β,16β,26-triol, 10a, and was also more environmentally friendly. Attempted methods for the transposition of the C-16β hydroxyl to the 15α position
are described. A successful method for this transposition via the 15α-hydroxy-16-ketone, 8a, using the Barton deoxygenation reaction on the 16-alcohol 14b, is reported. 相似文献
67.
通过使用墙体杀菌清洁与非杀菌清洁后涂料干膜的性能比较,评价了杀菌清洗对提高涂料干膜性能的有效性,揭示了怎样用杀菌清洁提高杀菌系统的特性。同时,比较了传统杀菌剂和新式杀菌剂的性能差别。 相似文献
68.
Poly(l-lactic acid) with 4% d-lactic acid comonomer has been drawn in the amorphous state at 80, 90, 100, 110 and 120 °C at an extension rate of 4 s−1 while simultaneously recording WAXS and SAXS patterns at intervals of 0.12 s. At 80, 90 and 100 °C, crystallisation is very rapid (1-4 s−1) and follows a first order transformation process to give highly oriented crystals. SAXS patterns were barely detectable at these temperatures despite fractional crystallinity of ∼0.2. At 110 and 120 °C, crystallisation was very slow (∼0.01 s−1) and gave rise to crystals with a lower degree of orientation. After eventual crystallisation at 120 °C, a two-point SAXS pattern develops with narrow lateral spread, suggesting ‘shish kebab’ morphology. When the 80 °C drawn sample was annealed at 120 °C, a strong four point SAXS pattern develops. The change in drawing and crystallisation behaviour at higher draw temperature is attributed to the onset of chain retraction relaxation processes. The WAXS fibre pattern after annealing shows sampling on intermediate layer lines that is consistent with the α crystal form with a 103 helix. However, prior to annealing, sampling indicates a different, less defined helical configuration. 相似文献
69.
Julia A. King Ibrahim Miskioglu Debra D. Wright‐Charlesworth Charles D. Van Karsen 《应用聚合物科学杂志》2007,103(1):328-335
In a composite material, the degree of adhesion between the fiber and the matrix plays an important role in the overall performance of the material. Because the load between the fiber and the matrix is realized throughout the interphase region material, a lot of effort has gone into characterizing the strength of the interphase. In this study, nanoscratch tests on the composite samples were used to provide a relative measure of adhesion in different composite materials. Carbon‐filled nylon 6,6 and polycarbonate resins were evaluated with this method. The carbon fillers we used were polyacrylonitrile‐based carbon fibers sized and surface‐treated for the respective matrix and pitch‐based carbon fibers without any sizing or surface treatment. Tensile and X‐ray photoelectron spectroscopy data for the composites we considered are also presented to compare to the nanoscratch results. It is shown that nanoscratch testing on the composites, with the proposed data analysis, can be an effective tool for determining the relative degree of adhesion between different composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 328–335, 2007 相似文献
70.
Andrew J. Wright Chuying Huang Michael J. Walock Anindya Ghoshal Muthuvel Murugan Jian Luo 《Journal of the American Ceramic Society》2021,104(1):448-462
Sand corrosion, thermal expansion, and ablation properties of a new class of medium- and high-entropy compositionally complex fluorite oxides (CCFOs) are examined as potential protective coating materials. Five binary oxides were mixed and sintered into dense, single-phase CCFOs of the general formula: [Hf(1-2x)/3Zr(1-2x)/3Ce(1-2x)/3YxYbx]O2-δ (x = 0.2, 0.074, and 0.029). These CCFOs exhibit decreased molten sand infiltration and interaction at intermediate temperatures (1200-1300°C) in comparison with a cubic yttria-stabilized zirconia (YSZ) reference; however, at higher temperatures, the trend is reversed due to the increased chemical reactivity. The equimolar high-entropy (Hf0.2Zr0.2Ce0.2Y0.2Yb0.2)O2-δ exhibits no grain boundary penetration by molten sand at all examined temperatures (1200°C-1500°C), although reaction and precipitation are significant. Moreover, these CCFOs exhibit higher intrinsic thermal expansion coefficients (CTE) than the YSZ reference, thereby being more compatible with Ni-based superalloys. The 8YSZ-like (Hf0.284Zr0.284Ce0.284Y0.074Yb0.074)O2-δ exhibits the highest CTE in this series of CCFOs due to oxygen clustering effects. Finally, these CCFOs also exhibit lower emissivities and form unique faceted microstructures in ablative environments. 相似文献