全文获取类型
收费全文 | 116083篇 |
免费 | 10794篇 |
国内免费 | 5978篇 |
专业分类
电工技术 | 4677篇 |
技术理论 | 2篇 |
综合类 | 7782篇 |
化学工业 | 26512篇 |
金属工艺 | 4811篇 |
机械仪表 | 5738篇 |
建筑科学 | 4165篇 |
矿业工程 | 5853篇 |
能源动力 | 4823篇 |
轻工业 | 15954篇 |
水利工程 | 1802篇 |
石油天然气 | 23176篇 |
武器工业 | 819篇 |
无线电 | 5529篇 |
一般工业技术 | 8619篇 |
冶金工业 | 5448篇 |
原子能技术 | 1645篇 |
自动化技术 | 5500篇 |
出版年
2024年 | 549篇 |
2023年 | 1606篇 |
2022年 | 2998篇 |
2021年 | 3745篇 |
2020年 | 4078篇 |
2019年 | 3712篇 |
2018年 | 3392篇 |
2017年 | 4260篇 |
2016年 | 4665篇 |
2015年 | 4516篇 |
2014年 | 6936篇 |
2013年 | 7660篇 |
2012年 | 8500篇 |
2011年 | 8492篇 |
2010年 | 6204篇 |
2009年 | 6005篇 |
2008年 | 5321篇 |
2007年 | 6629篇 |
2006年 | 6356篇 |
2005年 | 5630篇 |
2004年 | 4818篇 |
2003年 | 4481篇 |
2002年 | 3839篇 |
2001年 | 3237篇 |
2000年 | 2832篇 |
1999年 | 2336篇 |
1998年 | 1959篇 |
1997年 | 1659篇 |
1996年 | 1379篇 |
1995年 | 1134篇 |
1994年 | 876篇 |
1993年 | 614篇 |
1992年 | 544篇 |
1991年 | 434篇 |
1990年 | 336篇 |
1989年 | 236篇 |
1988年 | 161篇 |
1987年 | 124篇 |
1986年 | 91篇 |
1985年 | 115篇 |
1984年 | 101篇 |
1983年 | 70篇 |
1982年 | 54篇 |
1981年 | 24篇 |
1980年 | 39篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1975年 | 10篇 |
1959年 | 11篇 |
1951年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
L. Rodríguez-Liñares M.J. Lado X.A. Vila A.J. Méndez P. Cuesta 《Computer methods and programs in biomedicine》2014
In this paper, the gHRV software tool is presented. It is a simple, free and portable tool developed in python for analysing heart rate variability. It includes a graphical user interface and it can import files in multiple formats, analyse time intervals in the signal, test statistical significance and export the results. 相似文献
73.
A rapid test to measure performance,emission and wear of a diesel engine fueled with palm oil diesel
H. Masjuki A. M. Zaki S. M. Sapuan 《Journal of the American Oil Chemists' Society》1993,70(10):1021-1025
Results of performance, emission and tribological evaluations of palm oil methyl ester and its blends with conventional diesel
in an automobile diesel engine test bed are presented. Polymerization and carbon deposits on the fuel injector were monitored.
CO, CO2, O2, combustion efficiency and temperature of exhaust gases were also measured. Palm oil methyl ester and its blends have great
potential as alternative diesel fuel. Performance and exhaust gas emission for palm oil methyl ester and its blends with conventional
diesel are comparable with those of conventional diesel fuel. Palm oil methyl ester does not pose a severe environmental problem
and will not deteriorate engine and bearing components. 相似文献
74.
L. Di Giovacchino F. Angerosa L. Di Giacinto 《Journal of the American Oil Chemists' Society》1996,73(3):371-374
Variable quantities of leaves were added to ripe olives prior to extraction to determine their effect on the quality of the
resulting olive oil. The addition of 1–3% w/w leaves improved the organoleptic quality. An increase intrans-2-hexenal aldehyde content occurred, giving the pleasant flavor of “freshly cut grass.” This compound was produced by the
enzymatic breakdown of 13-L-hydroperoxide of linolenic acid in leaf homogenates. 相似文献
75.
The objective of this study was to determine how the fracture of adhesive joints depends on elastic beam parameters describing the adherends and the applied loads. The basic specimen geometry was the cracked lap shear joint constructed of aluminium alloy with various adherend and bondline thicknesses. Loads were applied in different combinations of bending, tension and shear to generate a failure envelope for each adhesive and specimen geometry. It was found that crack propagation for precracked specimens occured at a critical strain energy release rate but was also a function of the GI/GII ratio and the bondline thickness. The experiments also showed that the loads required to propagate a crack in a precracked specimen were always lower than the loads required to break the fillet. Hence, by treating uncracked joints as being cracked, where the fictitious crack tip is assumed to coincide with the location of the fillet, a conservative estimate of the failure load is obtained. 相似文献
76.
77.
R. Baixauli A. Salvador S. M. Fiszman C. Calvo 《Journal of the American Oil Chemists' Society》2002,79(11):1127-1131
Oil degradation caused by the number of fryings performed and the effect of oil degradation on the color of fried battered
squid rings were studied. Spectrophotometric techniques with absorbance in the UV and visible ranges, and iodine, peroxide,
and acid values were used to determine oil degradation. Determination of various CIELAB parameters in order to study the external
color of the fried battered squid rings revealed no differences in color due to the number of fryings. A study of the color
of the battered squid rings at various frying times and temperatures showed significant differences for both variables. Although
there was some degradation in the oil after 20 fryings, appearing as a slight darkening, it did not affect the final color
of the fried, battered squid rings. 相似文献
78.
Bleached and unbleached forms of a rosemary oleoresin (RO) in stripped and nonstripped soybean oil behave both as antioxidant
and prooxidant in a light-induced oxidative system. At 0.02 and 0.05% levels, RO had the greatest antioxidant activity, while
at 0.01 and 0.5% levels it had the highest prooxidant activity in both stripped and nonstripped soybean oil. Treatment of
both soybean oil systems with tertiary butylhydroquinone controlled light-induced oxidation of the oil better than did the
oleoresin treatments. The prooxidant activity of the 0.5% RO level was probably due to an excess of prooxidant components
being carried into the oil at that level, whereas the reduced antioxidant activity at 0.01% was probably due to the low initial
level of active antioxidant components being added to the oil.
Published as Journal Series No. 10072, Nebraska Agricultural Research Division, Department of Food Science and Technology,
University of Nebraska, Lincoln, NE 68583-0919. 相似文献
79.
A brown coal, peat and oil shale were subjected to a rapid pyrolysis process and medium-heat-value gases together with tar were collected. The char residue was of high activity and suitable for gasification to create a two-stage gasification system. The coal-tar is used for manufacturing liquid fuels and chemicals. 相似文献
80.
A monitoring program was performed to investigate heavy metal content alteration due to exploratory drilling for oil using non-aqueous fluids (NAFs) in Brazilian offshore, 900 m deep. Fourteen elements were monitored in 54 sites and it was verified that after drilling activities the average Ba concentration was remarkably increased with respect to background level, even 1 year after the activity. A minor increase in Mn and a moderate increase in Al concentrations were verified. The Cd, Cr, Ni, As, Co, Cu, Pb, V, and Zn concentrations were at the background levels, ca. 1 year after the NAFs drilling materials deposition on the seafloor. The Al, Ba, Cd, Cr, Cu, Ni and Zn mean concentrations were significantly different (P<0.05) between the three sampling operations (cruises) performed, while As, Cd, Fe and Pb presented different mean values according to the distance of the oil well, independent of the sampling operation. Interaction between sampling operation and distance was observed for Mn. In all sediment samples the Hg concentration was below the detection limit (0.07 μg g−1). 相似文献