全文获取类型
收费全文 | 26738篇 |
免费 | 2260篇 |
国内免费 | 958篇 |
专业分类
电工技术 | 1441篇 |
技术理论 | 1篇 |
综合类 | 1447篇 |
化学工业 | 4811篇 |
金属工艺 | 1475篇 |
机械仪表 | 1469篇 |
建筑科学 | 2049篇 |
矿业工程 | 648篇 |
能源动力 | 936篇 |
轻工业 | 1715篇 |
水利工程 | 374篇 |
石油天然气 | 1460篇 |
武器工业 | 135篇 |
无线电 | 3271篇 |
一般工业技术 | 3407篇 |
冶金工业 | 1533篇 |
原子能技术 | 333篇 |
自动化技术 | 3451篇 |
出版年
2024年 | 93篇 |
2023年 | 447篇 |
2022年 | 767篇 |
2021年 | 1147篇 |
2020年 | 796篇 |
2019年 | 743篇 |
2018年 | 761篇 |
2017年 | 862篇 |
2016年 | 815篇 |
2015年 | 1011篇 |
2014年 | 1357篇 |
2013年 | 1702篇 |
2012年 | 1688篇 |
2011年 | 1855篇 |
2010年 | 1515篇 |
2009年 | 1552篇 |
2008年 | 1420篇 |
2007年 | 1306篇 |
2006年 | 1421篇 |
2005年 | 1242篇 |
2004年 | 882篇 |
2003年 | 794篇 |
2002年 | 792篇 |
2001年 | 579篇 |
2000年 | 562篇 |
1999年 | 636篇 |
1998年 | 596篇 |
1997年 | 488篇 |
1996年 | 452篇 |
1995年 | 358篇 |
1994年 | 292篇 |
1993年 | 197篇 |
1992年 | 178篇 |
1991年 | 120篇 |
1990年 | 94篇 |
1989年 | 73篇 |
1988年 | 90篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 25篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Following up on recent studies of the Zn-rich corners of the Zn-Fe-Ni and Zn-Fe-Si ternary systems, a 450 °C isothermal section
of the Zn-Fe-Ni-Si quaternary phase diagram with the Zn composition being fixed at 93 at.% was determined experimentally using
optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS), and x-ray
diffractometry (XRD). FeSi was found to be in equilibrium with almost all phases in the section, including the T, ζ, Ni-δ,
NiSi2, and FeSi2 phases, as well as the liquid phase (L). Silicon solubilities in the T, ζ, and Ni-δ phases were rather limited. However,
the solubilities of Fe and Zn in the NiSi2 phase, at 4.5 at.% and 7.2 at.%, respectively, were appreciable. The existence of the (L+NiSi2+Ni-δ) three-phase equilibrium state apparently prevents other Ni-Si compounds from entering equilibrium with the liquid at
450 °C. No true quaternary compound was found in the study. 相似文献
53.
ABSTRACT: :
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献
54.
统计调查是统计工作的最基本环节,统计工作的质量在很大程度上取决于统计调查的质量。我国原有的统计调查方法体系已不再适应社会主义市场经济的新形势。鉴于面临着改革的新问题,论述了统计调查方法体制改革的目标模式和原则,提出了科学合理的统计调查体系,使统计工作更发适应社会主义市场经济体制的需求。 相似文献
55.
56.
57.
钻井液用BDY-1便携式堵漏仪 总被引:3,自引:2,他引:1
在堵漏过程中,对堵漏材料和堵漏浆配方的优选是决定堵漏成功的关键。为了能在现场对堵漏进行评价,研制出BDY-1便携式堵漏仪,该堵漏仪主要由不锈钢钢柱圈钢,压力表等加工而成,该堵漏仪体积小,重量轻,价格低,仅为国产堵漏仪的1/20。试验结果表明BDY-1便携式堵漏仪操作简便,可快速对堵漏材料进行评价并筛选出堵漏配方;数据重复性好,准确可靠,能达到进口或国产堵漏仪的水平;在模拟漏层选定后,可采用多套压力梯度,对堵漏浆封堵效果进行评价,在压力梯度选定后,可评价堵漏浆对不同类型漏层的封堵效果;如果扩大压力范围,可对封堵后的漏层进行破裂试验,从而确定合理的钻井施工参数;适用现场操作和应用。 相似文献
58.
苏金华 《石油化工腐蚀与防护》2002,19(3):33-34
对换热站容积式加热器管束失效原因进行了分析 ,指出主要是由于汽蚀和电化学腐蚀所致。从操作工艺和采用 12Cr2AlMoV材质两方面进行改进 ,可使管束的使用寿命由 4个月延长到 2年 相似文献
59.
This paper proposes a robust pilot-assisted channel estimation method for orthogonal frequency division multiplexing (OFDM) signals in Rayleigh fading. Our estimation method is based on nonlinear regression channel models. Unlike the linear minimum mean-squared error (LMMSE) channel estimate, the method proposed does not have to know or estimate channel statistics like the channel correlation matrix and the average signal-to-noise ratio (SNR) per bit. Numerical results indicate that the performance of the proposed channel estimator is very close to the theoretical bit error propagation lower bound that is obtained by a receiver with perfect channel response information 相似文献
60.