全文获取类型
收费全文 | 63781篇 |
免费 | 5433篇 |
国内免费 | 1984篇 |
专业分类
电工技术 | 4556篇 |
技术理论 | 6篇 |
综合类 | 4221篇 |
化学工业 | 9450篇 |
金属工艺 | 3740篇 |
机械仪表 | 3701篇 |
建筑科学 | 5266篇 |
矿业工程 | 1592篇 |
能源动力 | 1949篇 |
轻工业 | 3996篇 |
水利工程 | 1091篇 |
石油天然气 | 3216篇 |
武器工业 | 502篇 |
无线电 | 7859篇 |
一般工业技术 | 7945篇 |
冶金工业 | 2588篇 |
原子能技术 | 839篇 |
自动化技术 | 8681篇 |
出版年
2025年 | 238篇 |
2024年 | 1576篇 |
2023年 | 1440篇 |
2022年 | 1927篇 |
2021年 | 2725篇 |
2020年 | 2147篇 |
2019年 | 1849篇 |
2018年 | 1817篇 |
2017年 | 2008篇 |
2016年 | 1863篇 |
2015年 | 2400篇 |
2014年 | 2873篇 |
2013年 | 3491篇 |
2012年 | 3749篇 |
2011年 | 3980篇 |
2010年 | 3593篇 |
2009年 | 3340篇 |
2008年 | 3468篇 |
2007年 | 3322篇 |
2006年 | 3325篇 |
2005年 | 2817篇 |
2004年 | 1992篇 |
2003年 | 1806篇 |
2002年 | 1894篇 |
2001年 | 1682篇 |
2000年 | 1456篇 |
1999年 | 1565篇 |
1998年 | 1157篇 |
1997年 | 1018篇 |
1996年 | 995篇 |
1995年 | 811篇 |
1994年 | 666篇 |
1993年 | 488篇 |
1992年 | 440篇 |
1991年 | 327篇 |
1990年 | 213篇 |
1989年 | 181篇 |
1988年 | 159篇 |
1987年 | 99篇 |
1986年 | 68篇 |
1985年 | 62篇 |
1984年 | 40篇 |
1983年 | 24篇 |
1982年 | 34篇 |
1981年 | 19篇 |
1980年 | 20篇 |
1979年 | 8篇 |
1955年 | 2篇 |
1953年 | 3篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Keng Chen Zeming Wang Liang Wang Xiuzhen Wu Bingjie Hu Zheng Liu Minghong Wu 《纳微快报(英文)》2021,(10):1-13
High-efficiency electrochemical hydrogen evolution reaction (HER) offers a promising strategy to address energy and environmental crisis. Platinum is the most e... 相似文献
92.
Xu Li Bingyang Dai Jiaxin Guo Lizhen Zheng Quanyi Guo Jiang Peng Jiankun Xu Ling Qin 《纳微快报(英文)》2021,(10):29-76
Osteoarthritis is the most prevalent chronic and debilitating joint disease, resulting in huge medical and socioeconomic burdens. Intra-articular administration... 相似文献
93.
94.
With further exploration and development of oil and gas fields both at home and abroad,complicated geological conditions,poor quality of reserves and abominable working environment,drilling business,the largest of upstream petroleum 相似文献
95.
The formation and distribution of dioxin-like polychlorinated biphenyls (dl-PCBs) during cooking was investigated. Concentrations of dl-PCBs in liquid residues, cooked beef, and oil fumes generated during heating were determined by isotope dilution HRGC/HRMS. Although the levels of dl-PCBs in well-done beef were lower compared with those of raw beef, relatively high concentrations of dl-PCBs were detected in the oil fumes produced during heating. This suggests that dl-PCBs in raw beef may have volatilized into the oil fumes during the cooking process. Sucralose and chloropropanols contained in raw materials may have resulted in increased dl-PCB concentrations and the level of toxic equivalents (TEQ) in the oil fumes produced under high temperature during cooking. Concentrations of dl-PCBs did not vary greatly in cooked beef, except when higher levels of chloropropanols were presented in the uncooked raw materials. Results indicate that sucralose and chloropropanols may promote the formation of dl-PCBs during the cooking process. The newly produced dl-PCBs from raw beef cooking were mainly present in oil fumes, which gave rise to high levels of TEQ in oil fumes. 相似文献
96.
97.
Most of proposed models available so far associated with the evaluation of design embedded length of fiber reinforced polymer (FRP) rods in concrete are not reliability-based. This paper made an attempt, from the probabilistic standpoint, to determine the design embedded length of a glass fiber reinforced polymer (GFRP) rod in the case of splitting bond failure from concrete. The mathematical model put forward by Orangun et al. for evaluating the average bond strength of reinforcing bars in concrete for splitting failure has been adopted to develop the nonlinear limit state function corresponding to GFRP’s splitting bond failure in which five independent random variables, i.e. concrete strength, GFRP tensile strength, embedded length, GFRP diameter and computational uncertainty factor, are included. As the result of the probabilistic calibration procedures using the Rackwitz–Fiessler method, a non-dimensional factor K associated closely with the design embedded length of a GFRP rod in concrete is proposed to be 0.0306 with the suggested additional target reliability index of 1.10. The effects of some factors on GFRP’s design embedded length have been identified through the following parametric study. Although the calibration process is case-dependent to some extent, the proposed formula is thought to be acceptable for general bond design purposes of GFRP-reinforced concrete components. 相似文献
98.
文化产业往往作用于城市个性的培育、城市形象的树立、城市魅力的增加和城市品味的塑造,发展文化产业已成为城市竞争的新焦点。作为城市发展重要纲领的城市规划,要如何应对并促进文化产业发展,是规划创新与改革的新课题。山西省在编制城市规划时,基于文化产业发展构思,对文化产业的空间布局、品牌塑造、文化创新、政策配套方面进行了思考与规划,取得了一定效果。 相似文献
99.
在城市核心区进行群坑施工时,降水、临时封堵墙拆除等施工是关键,也是上海外滩地区综合改造工程中的难题。因此,针对“共墙”结构特点,采用了分幅施工技术,不权成功地解决了施工难题,又确保了施工中的安全与进度。 相似文献
100.