全文获取类型
收费全文 | 23633篇 |
免费 | 3719篇 |
国内免费 | 761篇 |
专业分类
电工技术 | 240篇 |
综合类 | 1811篇 |
化学工业 | 2257篇 |
金属工艺 | 1213篇 |
机械仪表 | 1015篇 |
建筑科学 | 1513篇 |
矿业工程 | 6120篇 |
能源动力 | 276篇 |
轻工业 | 1094篇 |
水利工程 | 444篇 |
石油天然气 | 672篇 |
武器工业 | 149篇 |
无线电 | 804篇 |
一般工业技术 | 1768篇 |
冶金工业 | 7641篇 |
原子能技术 | 145篇 |
自动化技术 | 951篇 |
出版年
2024年 | 88篇 |
2023年 | 313篇 |
2022年 | 660篇 |
2021年 | 783篇 |
2020年 | 905篇 |
2019年 | 718篇 |
2018年 | 720篇 |
2017年 | 875篇 |
2016年 | 1138篇 |
2015年 | 1063篇 |
2014年 | 1549篇 |
2013年 | 1544篇 |
2012年 | 1713篇 |
2011年 | 1816篇 |
2010年 | 1397篇 |
2009年 | 1284篇 |
2008年 | 1009篇 |
2007年 | 1277篇 |
2006年 | 1108篇 |
2005年 | 1037篇 |
2004年 | 877篇 |
2003年 | 887篇 |
2002年 | 708篇 |
2001年 | 685篇 |
2000年 | 677篇 |
1999年 | 555篇 |
1998年 | 445篇 |
1997年 | 377篇 |
1996年 | 325篇 |
1995年 | 315篇 |
1994年 | 281篇 |
1993年 | 208篇 |
1992年 | 182篇 |
1991年 | 146篇 |
1990年 | 118篇 |
1989年 | 130篇 |
1988年 | 64篇 |
1987年 | 47篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1966年 | 2篇 |
1964年 | 4篇 |
1960年 | 4篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Stefano Mariani Antonino Amedeo La Mattina Alessandro Paghi Lucanos Strambini Giuseppe Barillaro 《Advanced functional materials》2021,31(26):2100774
Here, a fluoride-assisted route for the controlled in-situ synthesis of metal nanoparticles (NPs) (i.e., AgNPs, AuNPs) on polydimethylsiloxane (PDMS) is reported. The size and coverage of the NPs on the PDMS surface are modulated with time and over space during the synthetic process, leveraging the improved yield (10×) and faster kinetics (100×) of NP formation in the presence of F− ions, compared to fluoride-free approaches. This enables the maskless preparation of both linear and step gradients and patterns of NPs in 1D and 2D on the PDMS surface. As an application in flexible plasmonics/photonics, continuous and step-wise spatial modulations of the plasmonic features of PDMS slabs with 1D and 2D AgNP gradients on the surface are demonstrated. An excellent spatially resolved tuning of key optical parameters, namely, optical density from zero to 5 and extinction ratio up to 100 dB, is achieved with AgNP gradients prepared in AgF solution for 12 minutes; the performance are comparable to those of commercial dielectric/interference filters. When used as a rejection filter in optical fluorescence microscopy, the AgNP-PDMS slabs are able to reject the excitation laser at 405 nm and retain the green fluorescence of microbeads (100 µm) used as test cases. 相似文献
2.
本文分析了乌兰矿投产前期采矿现状及存在的主要问题,针对该矿所处蒙古国经济落后、投资风险大的现实状况,为避免生产中断、规避投资风险,早日回收前期投资考虑,采取了双斜坡道开拓、全尾胶结充填、高端壁空场嗣后充填采矿、多中段组合式连续开采等系列技术应对方案。大大降低了一次性投资规模及投资风险,前期投资得以快速回笼的同时,矿山产能也充分释放,确保了矿山的持续稳定,取得了较好的经济和社会效益。为海外地下近地表矿体开采矿山规避投资风险提供了很好的技术方案借鉴。 相似文献
3.
4.
5.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii 下载免费PDF全文
Wen Li Xiaobei Li Yan Yang Feng Zhou Yanfang Liu Shuai Zhou Hailong Yu 《International Journal of Food Science & Technology》2015,50(11):2360-2366
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels. 相似文献
6.
7.
《Ceramics International》2020,46(4):4335-4343
This study aims at assessing the influence of nanosilica on the bioactivity and mechanical properties of calcium aluminate cement. For this purpose, nanosilica was applied as a replacement for calcium aluminate cement at 0, 2, 5 and 8 wt%. The main components were analyzed by scanning electron microscope coupled with surface imaging and elemental analysis, fourier transform infrared spectroscopy and X-ray diffraction analysis. To estimate the bioactivity of specimens, hydroxyapatite formation on the surface of cement paste was investigated in the simulated body fluid solution. In addition, in vivo evaluation of calcium aluminate cement was performed in subcutaneous tissue of rats. To investigate the mechanical properties, both compressive and flexural strengths were also measured. The results revealed that by increasing nanosilica up to 8 wt%, the strength enhanced. Moreover all cement paste samples with various amounts of nanosilica represented good bioactivity because of formation of bonelike apatite layer on the surface of specimens within 28 days after soaking in simulated body fluid. In vivo experiments indicated that the cement sample was absorbed by the tissue and there was no infection at the implant site. Based on the in vitro and in vivo results, the specimen with 2 wt% nanosilica represented the highest bioactivity. 相似文献
8.
Kalai Selvan Ramalingam Karmegam Karuppiah Shiamala Devi Ramaiya Vivien How Enoch Kumar Perimal Hassan Sadeghi Naeini Sivasankar Sambasivam Kulanthayan KC Mani 《人机工程学与制造业中的人性因素》2019,29(5):426-434
Many occupations require workers to stand for long periods of time without proper interventions, which causes discomfort in the back and lower limbs. Therefore, this study aims to assess the effectiveness in alleviating body muscle discomfort during prolonged standing through the use of a calf massager. This study was conducted among male workers at a manufacturer with production line workers and the list was obtained from the HR Department and simple random sampling was done by number categorization. A total of 100 respondents (50 respondents for both the control and the experimental groups) participated in this study. The experiment took place in a room with a similar setup for the production line. Each respondent was requested to perform the simulated task for 2 hr. For the experimental group, the calf massager was turned on every 15 min. At every 15‐min interval after turning on the calf massager, respondents from both groups were required to evaluate their discomfort level on a Borg's scale CR‐10 questionnaire. The results showed that the level of body discomfort among respondents in the experimental group reduced (20–30%) compared with that of the control group. Multivariate analysis results revealed that the discomfort rating for the lower back, knees, thighs, calves, and feet was significantly lower (p < .05) among the experimental group compared with the control group. For lower body parts, the lower back region was statistically significant (p < .05) at the 90th, 105th, and 120th min; the thigh region was statistically significant (p < .05) at the 120th min; the knee region was statistically significant (p < .05) at the 105th and 120th min; the calf region was statistically significant (p < .05) at all minute intervals except the 15th and 45th min, while the feet region, was statistically significant at the 105th and 120th min. Therefore, this study indicates that calf massage treatment is capable of reducing body muscle discomfort during prolonged standing and highlights the significance of calf massage. 相似文献
9.
10.