全文获取类型
收费全文 | 165726篇 |
免费 | 6775篇 |
国内免费 | 3991篇 |
专业分类
电工技术 | 5528篇 |
技术理论 | 7篇 |
综合类 | 4365篇 |
化学工业 | 21355篇 |
金属工艺 | 8895篇 |
机械仪表 | 7061篇 |
建筑科学 | 7461篇 |
矿业工程 | 2013篇 |
能源动力 | 4801篇 |
轻工业 | 10035篇 |
水利工程 | 1857篇 |
石油天然气 | 5156篇 |
武器工业 | 465篇 |
无线电 | 22901篇 |
一般工业技术 | 29340篇 |
冶金工业 | 28205篇 |
原子能技术 | 2082篇 |
自动化技术 | 14965篇 |
出版年
2024年 | 280篇 |
2023年 | 1265篇 |
2022年 | 2170篇 |
2021年 | 3103篇 |
2020年 | 2398篇 |
2019年 | 2295篇 |
2018年 | 2958篇 |
2017年 | 3149篇 |
2016年 | 3050篇 |
2015年 | 3268篇 |
2014年 | 4660篇 |
2013年 | 8263篇 |
2012年 | 6594篇 |
2011年 | 8177篇 |
2010年 | 6910篇 |
2009年 | 7344篇 |
2008年 | 7434篇 |
2007年 | 7525篇 |
2006年 | 7186篇 |
2005年 | 6367篇 |
2004年 | 5213篇 |
2003年 | 4856篇 |
2002年 | 4291篇 |
2001年 | 4541篇 |
2000年 | 4336篇 |
1999年 | 4818篇 |
1998年 | 10759篇 |
1997年 | 7298篇 |
1996年 | 5770篇 |
1995年 | 4079篇 |
1994年 | 3539篇 |
1993年 | 3266篇 |
1992年 | 2055篇 |
1991年 | 1919篇 |
1990年 | 1821篇 |
1989年 | 1545篇 |
1988年 | 1339篇 |
1987年 | 967篇 |
1986年 | 991篇 |
1985年 | 974篇 |
1984年 | 842篇 |
1983年 | 722篇 |
1982年 | 731篇 |
1981年 | 703篇 |
1980年 | 579篇 |
1979年 | 479篇 |
1978年 | 415篇 |
1977年 | 533篇 |
1976年 | 959篇 |
1975年 | 300篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Functional expression and synergistic cooperation of xylan‐degrading enzymes from Hypocrea orientalis and Aspergillus niger
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
72.
73.
Ugur Gezer Ebru E. Y?rüker Metin Keskin Cemil Burak Kulle Yoganiranjana Dharuman Stefan Holdenrieder 《International journal of molecular sciences》2015,16(12):29654-29662
Circulating nucleic acids (CNAs) are under investigation as a liquid biopsy in cancer as potential non-invasive biomarkers, as stable structure in circulation nucleosomes could be valuable sources for detection of cancer-specific alterations in histone modifications. Our interest is in histone methylation marks with a focus on colorectal cancer, one of the leading cancers respective the incidence and mortality. Our previous work included the analysis of trimethylations of lysine 9 on histone 3 (H3K9me3) and of lysine 20 on histone 4 (H4K20me3) by chromatin immuno- precipitation-related PCR in circulating nucleosomes. Here we asked whether global immunologic measurement of histone marks in circulation could be a suitable approach to show their potential as biomarkers. In addition to H3K9me3 and H4K20me3 we also measured H3K27me3 in plasma samples from CRC patients (n = 63) and cancer free individuals (n = 40) by ELISA-based methylation assays. Our results show that of three marks, the amounts of H3K27me3 (p = 0.04) and H4K20me3 (p < 0.001) were significantly lower in CRC patients than in healthy controls. For H3K9me3 similar amounts were measured in both groups. Areas under the curve (AUC) in receiver operating characteristic (ROC) curves indicating the power of CRC detection were 0.620 for H3K27me3, 0.715 for H4K20me3 and 0.769 for the combination of both markers. In conclusion, findings of this preliminary study reveal the potential of blood-based detection of CRC by quantification of histone methylation marks and the additive effect of the marker combination. 相似文献
74.
Chuang Yu Yu Yang Ze-xiang Wu Ji-fang Jiang Rao-ping Liao Yong-feng Deng 《Geotextiles and Geomembranes》2021,49(2):413-419
Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb2+) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values < 3 and concentrations of Pb2+ >40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement. 相似文献
75.
Zhuo Shi Ningning Dong Dingfeng Zhang Xiaofang Jiang Guanxin Du Shichao Lv Jiejie Chen Jun Wang Shifeng Zhou 《Journal of the American Ceramic Society》2019,102(7):3965-3971
The construction of nonlinear optical materials featuring asymmetric transmission of light is of great technological importance for various applications, including optical switching and optical power limiting. A significant challenge is the scalable fabrication of material candidates with good photochemical stability, high optical transmittance, and excellent optical limiting performance. Here, we present a nanocrystallization avenue for constructing hybrid optical limiting materials that exhibit ultrafast and robust optical limiting performance. The experimental results show that the controllable relaxation of a niobate glass may lead to the clustering of Nb-O units and contracting of the bandgap. It results in the notable improvement in nonlinear optical properties, including the enhanced saturation irradiance (380 GW/cm2), doubly increased nonlinear coefficient, and decreased limiting threshold (200 GW/cm2). Our results suggest a promising material that exhibits promising applications for protecting eyes and sensitive components from laser-induced damage. 相似文献
76.
77.
78.
Longzhi Li Xiaowei Jiang Zhiguo Bian Jianwei Wang Fumao Wang Zhanlong Song 《Drying Technology》2019,37(2):173-185
Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading. 相似文献
79.
80.