全文获取类型
收费全文 | 197690篇 |
免费 | 2258篇 |
国内免费 | 632篇 |
专业分类
电工技术 | 4062篇 |
综合类 | 123篇 |
化学工业 | 26703篇 |
金属工艺 | 7507篇 |
机械仪表 | 5462篇 |
建筑科学 | 4040篇 |
矿业工程 | 747篇 |
能源动力 | 4659篇 |
轻工业 | 14384篇 |
水利工程 | 1696篇 |
石油天然气 | 2842篇 |
武器工业 | 7篇 |
无线电 | 27291篇 |
一般工业技术 | 37388篇 |
冶金工业 | 45389篇 |
原子能技术 | 3563篇 |
自动化技术 | 14717篇 |
出版年
2021年 | 1245篇 |
2019年 | 1282篇 |
2018年 | 2124篇 |
2017年 | 2106篇 |
2016年 | 2175篇 |
2015年 | 1489篇 |
2014年 | 2618篇 |
2013年 | 7950篇 |
2012年 | 4461篇 |
2011年 | 6110篇 |
2010年 | 4933篇 |
2009年 | 5772篇 |
2008年 | 6147篇 |
2007年 | 6197篇 |
2006年 | 5636篇 |
2005年 | 5303篇 |
2004年 | 5250篇 |
2003年 | 5089篇 |
2002年 | 4899篇 |
2001年 | 5307篇 |
2000年 | 4917篇 |
1999年 | 5437篇 |
1998年 | 15622篇 |
1997年 | 10314篇 |
1996年 | 7931篇 |
1995年 | 5784篇 |
1994年 | 5014篇 |
1993年 | 5022篇 |
1992年 | 3386篇 |
1991年 | 3260篇 |
1990年 | 3218篇 |
1989年 | 3039篇 |
1988年 | 2784篇 |
1987年 | 2234篇 |
1986年 | 2301篇 |
1985年 | 2606篇 |
1984年 | 2312篇 |
1983年 | 2063篇 |
1982年 | 1901篇 |
1981年 | 2044篇 |
1980年 | 1790篇 |
1979年 | 1659篇 |
1978年 | 1656篇 |
1977年 | 2022篇 |
1976年 | 2702篇 |
1975年 | 1422篇 |
1974年 | 1369篇 |
1973年 | 1316篇 |
1972年 | 1124篇 |
1971年 | 956篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
A. Nakano T. Shimazaki M. Sekiya H. Shiozawa K. Ohtsuka A. Aoyagi T. Iwakiri Z. Mikami M. Sato Y. Sugino K. Kinoshita T. Matsuoka T. Imamura Y. Takayama K. Yamamoto 《International Journal of Hydrogen Energy》2021,46(29):15649-15659
Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa. 相似文献
2.
Castro Mateus B. Souza Raphael R. N. Junior Agord M. P. Lima Eduardo R. Manera Leandro T. 《Analog Integrated Circuits and Signal Processing》2021,109(3):647-656
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The... 相似文献
3.
4.
Wireless Personal Communications - This paper summarizes the ongoing research initiatives based on the advanced multiple access techniques towards the fifth generation (5G) wireless communication... 相似文献
5.
Multicomponent Diamond-Like Semiconductors Based on the InBV–CdS System: Bulk and Surface Properties
Semiconductors - According to developed methods, in the fields of the mutual solubility of initial binary compounds (InP, InSb, and CdS), solid solutions of the InP–CdS and InSb–CdS... 相似文献
6.
7.
8.
The role of the following factors in the selection of technological bases for manufacturing is considered: the accessibility of the machined surfaces; their parameters and dimensional relationships; their position relative to the forces acting; and the uniformity of the margin distribution. 相似文献
9.
Puneet Parmar Nicolas Lopez-Villalobos John T. Tobin Eoin Murphy Frank Buckley Shane V. Crowley Alan L. Kelly Laurence Shalloo 《International Journal of Food Science & Technology》2021,56(5):2415-2422
The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T2 (R2 = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T2 (R2 = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm−3, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm−3 at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally. 相似文献
10.