全文获取类型
收费全文 | 29808篇 |
免费 | 1572篇 |
国内免费 | 140篇 |
专业分类
电工技术 | 484篇 |
综合类 | 238篇 |
化学工业 | 5249篇 |
金属工艺 | 866篇 |
机械仪表 | 666篇 |
建筑科学 | 787篇 |
矿业工程 | 147篇 |
能源动力 | 522篇 |
轻工业 | 4119篇 |
水利工程 | 213篇 |
石油天然气 | 168篇 |
武器工业 | 10篇 |
无线电 | 1639篇 |
一般工业技术 | 5470篇 |
冶金工业 | 7253篇 |
原子能技术 | 170篇 |
自动化技术 | 3519篇 |
出版年
2023年 | 320篇 |
2022年 | 317篇 |
2021年 | 683篇 |
2020年 | 558篇 |
2019年 | 488篇 |
2018年 | 976篇 |
2017年 | 845篇 |
2016年 | 945篇 |
2015年 | 822篇 |
2014年 | 973篇 |
2013年 | 1838篇 |
2012年 | 1373篇 |
2011年 | 1390篇 |
2010年 | 1175篇 |
2009年 | 1106篇 |
2008年 | 1234篇 |
2007年 | 1153篇 |
2006年 | 832篇 |
2005年 | 666篇 |
2004年 | 505篇 |
2003年 | 471篇 |
2002年 | 426篇 |
2001年 | 341篇 |
2000年 | 328篇 |
1999年 | 458篇 |
1998年 | 2278篇 |
1997年 | 1384篇 |
1996年 | 959篇 |
1995年 | 591篇 |
1994年 | 478篇 |
1993年 | 431篇 |
1992年 | 184篇 |
1991年 | 187篇 |
1990年 | 158篇 |
1989年 | 164篇 |
1988年 | 154篇 |
1987年 | 171篇 |
1986年 | 151篇 |
1985年 | 229篇 |
1984年 | 189篇 |
1983年 | 171篇 |
1982年 | 132篇 |
1981年 | 178篇 |
1980年 | 176篇 |
1979年 | 123篇 |
1978年 | 111篇 |
1977年 | 222篇 |
1976年 | 485篇 |
1974年 | 91篇 |
1973年 | 117篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
World Wide Web - Rule mechanism has been widely used in many areas, such as databases, artificial intelligent and pervasive computing. In a rule mechanism, rule activation decides which rules are... 相似文献
12.
Christoph Gottschalk Aiko Huckauf Arne Dübecke Florian Kaltner Matthias Zimmermann Ines Rahaus 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(7):1366-1383
The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment. 相似文献
13.
14.
Nurullah Bulut Bahar Atmaca Gülsün Akdemir Evrendilek Sibel Uzuner 《Journal of Food Safety》2020,40(6):e12855
Seed processing technologies are essential for seed safety and functionality through protection of physicochemical quality, pathogen inactivation, aflatoxin detoxification and alleviation of mutagenicity. Design of a pilot-scale unit of pulsed electric fields (PEF) to treat sesame seeds with respect to quality parameters, Aspergillus parasiticus inactivation and aflatoxin reduction as well as alleviation of aflatoxin mutagenicity were prompted in this study. PEF energy ranged from 0.97 to 17.28 J achieved maximum reductions of peroxide value and acidity number of 67.4 and 85.7%, respectively, and did not change color L*, a*, b* and hue values. A 60% reduction of A. parasiticus counts occurred at the maximum PEF energy. Aflatoxins G1, G2, B1, and B2 contents decreased by 94.7, 92.7, 86.9, and 98.7%, respectively. Except for the samples treated by 2.16 J with 100 μg/plate and by 6.80 J with 10 μg/plate, PEF treatment provided elimination of aflatoxin mutagenity. It is concluded that PEF treatment can be used to treat sesame seeds with preservation of physicochemical properties, inactivation of A. parasiticus and decomposition of aflatoxins with reduced mutagenicity. 相似文献
15.
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the... 相似文献
16.
17.
18.
19.