全文获取类型
收费全文 | 77667篇 |
免费 | 7978篇 |
国内免费 | 4550篇 |
专业分类
电工技术 | 4854篇 |
技术理论 | 2篇 |
综合类 | 6169篇 |
化学工业 | 12605篇 |
金属工艺 | 4545篇 |
机械仪表 | 4981篇 |
建筑科学 | 5789篇 |
矿业工程 | 2099篇 |
能源动力 | 1939篇 |
轻工业 | 7418篇 |
水利工程 | 1700篇 |
石油天然气 | 3388篇 |
武器工业 | 733篇 |
无线电 | 8904篇 |
一般工业技术 | 8941篇 |
冶金工业 | 3219篇 |
原子能技术 | 832篇 |
自动化技术 | 12077篇 |
出版年
2024年 | 393篇 |
2023年 | 1211篇 |
2022年 | 2220篇 |
2021年 | 3032篇 |
2020年 | 2281篇 |
2019年 | 2052篇 |
2018年 | 2287篇 |
2017年 | 2439篇 |
2016年 | 2286篇 |
2015年 | 3222篇 |
2014年 | 3934篇 |
2013年 | 4768篇 |
2012年 | 5465篇 |
2011年 | 6005篇 |
2010年 | 5478篇 |
2009年 | 5479篇 |
2008年 | 5208篇 |
2007年 | 4923篇 |
2006年 | 4817篇 |
2005年 | 3972篇 |
2004年 | 2920篇 |
2003年 | 2577篇 |
2002年 | 2740篇 |
2001年 | 2312篇 |
2000年 | 1629篇 |
1999年 | 1436篇 |
1998年 | 955篇 |
1997年 | 774篇 |
1996年 | 723篇 |
1995年 | 603篇 |
1994年 | 459篇 |
1993年 | 389篇 |
1992年 | 288篇 |
1991年 | 205篇 |
1990年 | 155篇 |
1989年 | 132篇 |
1988年 | 103篇 |
1987年 | 72篇 |
1986年 | 39篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 30篇 |
1981年 | 8篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
为了避免回收单一钕铁硼废料中有价元素带来的操作复杂和资源浪费等问题,本研究采用共沉淀法共沉淀出钕铁硼废料中的有价元素Me(Nd,Pr,Co,Fe),制备可用于生产再生钕铁硼的原料;根据质量守恒和同时平衡原理,采用MATLAB软件建立Me(Nd,Pr,Co,Fe)-OH--NH3热力学模型,绘制lg[Me]-p H曲线模拟共沉淀工艺,并根据模拟结果确立了共沉淀工艺;模拟和实验的结果表明:根据lg[Me]-p H模拟结果可以确立一步共沉淀法的p H:6~10,Fe3+比Fe2+更易于沉淀完全;在上述条件下获得的共沉淀粉末主相均为Nd,Pr,Co,Fe的化合物,且有价元素的百分比含量均大于99.4%;其中,当p H值在8左右时回收率最高,在该条件下金属元素Me(Nd,Pr,Co,Fe)的沉淀效率分别为:98.7%,99.9%,93.6%,99.9%。该结果也表明共沉淀法工艺不仅高效,而且所制备的共沉淀粉末可以满足制备二次钕铁硼的需要。 相似文献
4.
Yao‐Min Hung Neng‐Chyan Huang Jyh‐Seng Wang Shue‐Ren Wann 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(2):344-346
Cases of isolated hepatic tuberculosis (TB) are rare. The diagnosis is often delayed or missed because of nonspecific symptoms and laboratory findings. Besides, the disease is extremely rare even in a country where TB is an alarming public health problem. This report demonstrates the difficulty in correctly diagnosing local hepatic TB. We report the case of a 62‐year‐old male patient with end‐stage renal disease treated with hemodialysis, who developed 2 months of abdominal distension and general anorexia, with hyperechoic hepatic lesions on ultrasound. Computed tomography suspected multiple liver tumors. The liver biopsy finally led to the diagnosis of TB of the liver without other involvements. We conclude that isolated hepatic TB is one of the rare forms of extrapulmonary TB in dialysis patients. A greater awareness of this rare clinical entity may prevent needless surgical interventions. 相似文献
5.
Wenli Yao Huajun Zhang Shengwen Zhong Jiwen Li Lingshun Wang 《Journal of Electroceramics》2019,43(1):84-91
Li2ZrO3-modified LiNi0.5Mn0.5O2 materials with improved electrochemical performance were directly synthesized by a simple mechanical milling route with ZrO2, Li2CO3 and Ni0.5Mn0.5(OH)2 precursors... 相似文献
6.
Harshavardhan Mohan Jeong-Muk Lim Se-Won Lee Min Cho Yool-Jin Park Kamala-Kannan Seralathan Byung-Taek Oh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(1):297-307
The cover image is based on the Research Article V2O5/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification by Mohan, H et al., DOI: 10.1002/jctb.6238 .
7.
Abiodun B. Ogbesejana Zhong Ningning Oluwadayo O. Sonibare 《Petroleum Science and Technology》2019,37(18):1969-1977
The occurrence and distributions of dibenzofurans (DBFs) and benzo[b]naphthofurans were investigated in crude oils from Niger Delta, Nigeria, by gas chromatography-mass spectrometry-mass spectrometry. The distribution of DBFs was characterized by the predominance of C2-dibenzofurans. 4-Methyldibenzofuran was the most abundant among the methyldibenzofurans isomers while dimethyldibenzofuran-2 (DMDBF-2), ethyldibenzofuran-1, DMDBF-3, and DMDBF-6 occurred in higher amounts when compared with other DMDBFs. Among the benzonaphthofurans, the abundance of benzo[b]naphtho[2,1-d]furan was higher than other isomers. The DBFs distributions in the oils were not affected by source facies and depositional environments. However, the DBFs concentrations increased with increasing maturity in oils from ADL and MJO oilfields. 相似文献
8.
Zhang Huawei Yang Zhi Wu Zhaoyu Hong Xiaoyu Li Zhong Xu Yulai Li Jun Ni Gaojin Xiao Xueshan 《Oxidation of Metals》2019,92(1-2):49-65
Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally... 相似文献
9.
Based on the phase transformation theories, especially the T0 concept of bainite transformation, alloy optimisation of bainitic steel with carbides has been carried out aiming at the produce of plastic mould with large cross-section. The effect of manganese and silicon on proeutectoid ferrite and bainite transformation is explored by dilatometric analysis, XRD and different microscopy techniques. The results show that after the alloy optimisation, the transformation of proeutectoid ferrite is suppressed and when the cooling rate is lower than 0·1°C?s??1, the new lower bainite transformation appears by decreasing carbon capacity of austenite and promoting carbide precipitation. Industrial production proves that the optimised alloy SDP1 can meet the demand for the plastic mould with the thickness of 1050?mm. 相似文献
10.