全文获取类型
收费全文 | 32275篇 |
免费 | 3242篇 |
国内免费 | 1623篇 |
专业分类
电工技术 | 2212篇 |
技术理论 | 3篇 |
综合类 | 2202篇 |
化学工业 | 5359篇 |
金属工艺 | 1615篇 |
机械仪表 | 2081篇 |
建筑科学 | 3194篇 |
矿业工程 | 860篇 |
能源动力 | 896篇 |
轻工业 | 2827篇 |
水利工程 | 613篇 |
石油天然气 | 1465篇 |
武器工业 | 243篇 |
无线电 | 3870篇 |
一般工业技术 | 3821篇 |
冶金工业 | 1191篇 |
原子能技术 | 427篇 |
自动化技术 | 4261篇 |
出版年
2024年 | 151篇 |
2023年 | 650篇 |
2022年 | 1272篇 |
2021年 | 1690篇 |
2020年 | 1223篇 |
2019年 | 980篇 |
2018年 | 1065篇 |
2017年 | 1165篇 |
2016年 | 1070篇 |
2015年 | 1355篇 |
2014年 | 1717篇 |
2013年 | 1961篇 |
2012年 | 2197篇 |
2011年 | 2297篇 |
2010年 | 2110篇 |
2009年 | 1983篇 |
2008年 | 1803篇 |
2007年 | 1684篇 |
2006年 | 1635篇 |
2005年 | 1372篇 |
2004年 | 909篇 |
2003年 | 838篇 |
2002年 | 821篇 |
2001年 | 744篇 |
2000年 | 673篇 |
1999年 | 699篇 |
1998年 | 493篇 |
1997年 | 477篇 |
1996年 | 464篇 |
1995年 | 370篇 |
1994年 | 312篇 |
1993年 | 205篇 |
1992年 | 158篇 |
1991年 | 110篇 |
1990年 | 83篇 |
1989年 | 80篇 |
1988年 | 62篇 |
1987年 | 40篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1962年 | 42篇 |
1961年 | 39篇 |
1960年 | 16篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Shanshan Zhuang Wenxiong Zheng Yunong Na Naiyi Chen Fan Gong Bingxuan Huang Stephen Brennan Charles Congyi Liu Jian Cheng Lukai Ma Huifan Liu 《International Journal of Food Science & Technology》2022,57(2):1093-1103
The β-Carotene (BC), an important precursor of vitamin A (VA), possesses antioxidant activity but is fat-soluble and has low bioavailability. In previous in-vitro assays evaluating antioxidant and 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) free radical scavenging, both BC and VA showed a strong ability to scavenge radicals and protected cells from oxidative stress. Here, we used artificially simulated gastrointestinal digestion and Caco-2 cell absorption models to evaluate the bioavailability of the BC during gastrointestinal digestion and absorption using high-performance liquid chromatography (HPLC) analysis. We observed high absorptive and transfer rates of BC and detected retinol metabolites (Vitamin A). Therefore, BC can be detected in the acidic gastrointestinal environment using HPLC. Optimised method provided better separation of BC and VA in the column, improving the accuracy of the test results. 相似文献
2.
3.
5.
6.
Telecommunication Systems - Machine to Machine technology has a broad application prospect in the 5G network, but there is a bottleneck in the energy consumption of intelligent devices powered by... 相似文献
7.
The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO2 inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO2 inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO2-NaOH-H2O system, CO2 inleakage saturation was derived to quantify the amount of the dissolved CO2 in GICW. This parameter can be directly calculated with the measured conductivity and the [Na+] of GICW. The influence of CO2 inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO2 inleakage and the NaOH dosage. This study provides insights into the influence of CO2 inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO2 inleakage occurs. 相似文献
8.
9.
Shanshan Li Bing Zhang Xuxiang Feng Yewei Wu 《International journal of remote sensing》2019,40(14):5635-5650
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6. 相似文献
10.