全文获取类型
收费全文 | 1588篇 |
免费 | 25篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 84篇 |
综合类 | 2篇 |
化学工业 | 444篇 |
金属工艺 | 46篇 |
机械仪表 | 39篇 |
建筑科学 | 21篇 |
能源动力 | 113篇 |
轻工业 | 133篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 140篇 |
一般工业技术 | 284篇 |
冶金工业 | 93篇 |
原子能技术 | 48篇 |
自动化技术 | 158篇 |
出版年
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 21篇 |
2020年 | 13篇 |
2019年 | 25篇 |
2018年 | 17篇 |
2017年 | 15篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 51篇 |
2013年 | 108篇 |
2012年 | 87篇 |
2011年 | 87篇 |
2010年 | 74篇 |
2009年 | 96篇 |
2008年 | 87篇 |
2007年 | 70篇 |
2006年 | 55篇 |
2005年 | 55篇 |
2004年 | 41篇 |
2003年 | 51篇 |
2002年 | 50篇 |
2001年 | 26篇 |
2000年 | 34篇 |
1999年 | 42篇 |
1998年 | 52篇 |
1997年 | 31篇 |
1996年 | 36篇 |
1995年 | 23篇 |
1994年 | 19篇 |
1993年 | 31篇 |
1992年 | 25篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有1616条查询结果,搜索用时 15 毫秒
951.
Effect of lubrication on impact drive mechanism 总被引:2,自引:0,他引:2
Katsushi Furutani Toshiro Higuchi Yutaka Yamagata Naotake Mohri 《Precision Engineering》1998,22(2):78-86
The impact drive mechanism (IDM) device moves utilizing impulsive force caused by rapid deformations of piezoelectric elements and friction. Most of the devices utilizing impulsive force and frictional force are used on only a dry base. In this paper, the movement performance of the IDM on fluid lubricated surfaces is investigated. The movement on fluid lubricated surfaces and that in oil are as minute as that on a dry base. In experiments, the movement of the device of the IDM on a fluid lubricated surface is the same as the calculated movement by assuming a dry surface. The standard deviation of movement on a fluid lubricated surface is smaller than that on a dry surface. Considering the small distribution of the movement and the antirust of the devices, the devices utilizing impulsive force should be driven under the boundary lubrication. 相似文献
952.
Suzuki T Ohashi R Yokogawa Y Nishizawa K Nagata F Kawamoto Y Kameyama T Toriyama M 《Journal of Bioscience and Bioengineering》1999,87(3):320-327
Calcium phosphate ceramics constructed from beta-tricalcium phosphate (TCP) and hydroxyapatite (HAP) have been successfully used as implant materials. However, there is a possibility that these materials are responsible for an unwanted inflammatory response during wound healing. Since TCP is soluble in the body, the instability of this material may contribute to this inflammatory response. Using composite ceramics of TCP and HAP that possessed Ca/P molar ratios of 1.50, 1.55, 1.60, 1.64, and 1.67, the effect of surface instability on fibroblast L-929 cells was investigated. The time-dependent variation of the initial anchoring ratio, cell density, and cell viability were measured. In general, the cells were severely damaged and ruptured on the highly soluble thin surface layer of the TCP-HAP ceramics. The initial anchoring ratio for TCP-HAP ceramics was as high as that for the polystyrene dish (Lux, control). However, viability at 6 h decreased to less than 50% of the initial cell density on ceramics with a Ca/P molar ratio of 1.64 (20% TCP-80% HAP), while 85% of the cells were viable on Lux. The viability on 100% TCP, whose surface is the most highly soluble among the TCP-HAP ceramics used in this study, was reduced to 20%. Morphological observation showed that the anchored cells were ruptured when grown in culture medium on the 100% TCP. Although the high solubility of the thin surface layer on the TCP-HAP ceramics of the carrier was found to be the dominant factor in the decreasing cell viability, the initial viability was enhanced by the stabilization of the surface of the TCP-HAP ceramics by pre-incubating the scaffolds in a culture medium containing 10% fetal bovine serum for 3 d. 相似文献
953.
Yutaka Yano 《Propellants, Explosives, Pyrotechnics》1989,14(5):187-189
The reaction process of boron (B) and potassium nitrate (PN) was examined with a thermochemical analysis. The process consists of a three-stage gasification reaction. A significant heat is produced in the first-stage process which is caused by the reaction B + KNO3 → KBO2 + NO. In the second-stage process, the remaining unreacted PN decomposes to produce gaseous oxidizing fragments. The KBO2 produced in the first-stage process decomposes in the third-stage process. Thc heat produced in the first-stage process is correlated with the mass fraction of B mixed within the B/PN mixture. 相似文献
954.
955.
Asai T Itagaki M Shiroki Y Yamada M Tokoro M Kojima A Ishihara K Esaki H Tamura Y Takahashi T 《Journal of food protection》2006,69(1):214-216
Salmonella enterica subsp. enterica serotype Infantis isolates from retail raw chicken meat (n = 98) and broiler chickens on farms (n = 70) were examined for antimicrobial susceptibility and antimicrobial resistance genes. A total of 15 antimicrobial resistance types, 14 in meat and 10 in broiler isolates, were identified, and 9 of the 15 types were indistinguishable between meat and broiler isolates. Resistance to both oxytetracycline and dihydrostreptomycin accounted for 94.0% of the resistance types in meat and broiler isolates, and each type harbored aadA1 within 1.0 kb of class 1 integron and tetA. Of nalidixic acid resistance types, point mutations at 87Asp (GAC) to Tyr (TAC) in the quinolone resistance-determining region of gyrA was detected in 10 of 13 meat isolates and at 87Asp to Asn (AAC) in four of seven broiler isolates. These findings suggest that the antimicrobial resistance of Salmonella Infantis in retail chicken meat predominantly originates from broiler chickens. 相似文献
956.
Abe Y Mutsuga M Hirahara Y Kawamura Y 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2011,52(5):309-313
A test method for 6 phthalates, bis(2-ethylhexyl)phthalate, dibutyl phthalate, benzyl butyl phthalate, diisononyl phthalate, diisodecyl phthalate and di-n-octyl phthalate, in polyvinyl chloride (PVC) was developed. GC/MS was used in the SIM mode for the separation and detection of phthalates. For preparation of the test solution, the extraction method with acetone-hexane mixture (3 : 7) and the dissolution method with tetrahydrofuran and ethanol were compared and it was confirmed that each method gave good recoveries. Dilution of the test solution was effective to reduce the influence of PVC. In a collaborative study with nine laboratories, the intra-laboratory variations showed good repeatability, but the measurements at some laboratories deviated widely. It appears that this method is unsuitable for the judgment of acceptability, but it may be suitable for the determination of phthalate content in PVC products. 相似文献
957.
Yoshida E Shibuya T Kurokawa C Inoue Y Yamamoto Y Miyazaki M 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2011,52(1):59-65
Development of rapid and high accuracy analysis, and tightening of regulations for veterinary drugs are required because many examples of detection of veterinary drugs in many kinds of processed food have been reported. In this study, we constructed an improved method for simultaneous determination of veterinary drugs, based on the glass bead homogenization method with EDTA-2Na and batch purification for QuEChERS analysis. Our extraction procedure is suitable for handling multiple samples quickly and easily. Furthermore, our improved extraction solvent allowed simultaneous determination of tetracyclines in processed food. In a test of 69 veterinary drugs, recovery of over 60 ranged from 70 to 120%, with a coefficient of variation of less than 25% and with quantification limits of 0.01 μg/g (S/N≥10 ). This improved method is expected to be useful for quick simultaneous determination of multiple residues. 相似文献
958.
Mikhail Vyssotski Kirill Lagutin Andrew MacKenzie Yutaka Itabashi 《Journal of the American Oil Chemists' Society》2015,92(3):383-391
γ‐Stearidonic acid, 18:4n‐6, a potential product of β‐oxidation of arachidonic acid (20:4n‐6), was only recently positively identified in a living organism—a thermophilic cyanobacterium Tolypothrix sp., albeit at low levels, whilst some indirect evidence suggests its wider presence, e.g. in a unicellular marine alga. We have prepared 18:4n‐6 using an iodolactonisation chain‐shortening approach from 22:5n‐6 and obtained its 1H‐, 13C‐, COSY‐ and HSQC NMR spectra, with 18:5n‐3 spectra also recorded for a comparison. The GC and GC‐MS behaviour of its methyl ester was also studied. Like another Δ3 polyunsaturated acid, octadecapentaenoic (18:5n‐3), 18:4n‐6 rapidly yields 2‐trans isomer upon formation of dimethyloxazoline derivative. On a polar ionic liquid phase (SLB‐IL100, 200 °C) the methyl ester could be mistaken for 18:3n‐3, while on methylsilicone phase (BP1, 210 °C) it eluted ahead of 18:3n‐6 and 18:4n‐3, suggesting that when present it may be easily misidentified during GC analysis of fatty acids. 相似文献
959.
Microstructures of ZrB2 ceramics consolidated by hot-pressing and spark plasma sintering were investigated by transmission electron microscopy (TEM), combining energy dispersive X-ray spectroscopy (EDX). The microstructures of both ceramics were compared. Amount of impurities was lower for ZrB2 consolidated by spark plasma sintering than for hot-pressed ZrB2. In particular, oxygen impurity was not detected even at the grain-boundaries in ZrB2 consolidated by spark plasma sintering. The cleaning effect generated on the powder surfaces during spark plasma sintering cycle was displayed. In addition, dislocations were present only in the spark plasma sintered ZrB2 ceramic, as a result of localized high stresses. 相似文献
960.
High performance liquid chromatographic separations of two enantiomeric pairs of 1-alkyl-2-acyl-rac-glycerol (1-alkyl-2-acyl- and 3-alkyl-2-acyl-sn-glycerols) and 1-alkyl-3-acyl-rac-glycerol (1-alkyl-3-acyl- and 3-alkyl-1-acyl-sn-glycerols) as 3,5-dinitrophenylurethanes (3,5-DNPUs) were carried out on a chiral stationary phase, N-(R)-1-(α-naphthyl)ethylaminocarbonyl-(S)-valine chemically bonded to γ-aminopropyl silanized silica (Sumipax OA-4100). Good separation of the enantiomers of 1-hexadecyl-2-hexadecanoyl-rac-glycerol was easily achieved within 10 min using hexane/ethylene dichloride/ethanol (80∶20∶1, v/v/v) as a mobile phase. Separation
of the enantiomers of 1-hexadecyl-3-hexadecanoyl-rac-glycerol was more difficult and required about 80 min to achieve satisfactory peak resolution (0.8) using hexane/ethylene
dichloride/ethanol (250∶20∶1, v/v/v) as a mobile phase.
Presented at the American Oil Chemists' Society 79th Annual Meeting, Phoenix, AZ, May, 1988. 相似文献