全文获取类型
收费全文 | 95123篇 |
免费 | 10752篇 |
国内免费 | 7177篇 |
专业分类
电工技术 | 9191篇 |
技术理论 | 2篇 |
综合类 | 9086篇 |
化学工业 | 12236篇 |
金属工艺 | 6113篇 |
机械仪表 | 6855篇 |
建筑科学 | 8198篇 |
矿业工程 | 3135篇 |
能源动力 | 2774篇 |
轻工业 | 8340篇 |
水利工程 | 2709篇 |
石油天然气 | 3857篇 |
武器工业 | 1319篇 |
无线电 | 10823篇 |
一般工业技术 | 8732篇 |
冶金工业 | 3866篇 |
原子能技术 | 1376篇 |
自动化技术 | 14440篇 |
出版年
2024年 | 530篇 |
2023年 | 1521篇 |
2022年 | 3150篇 |
2021年 | 4099篇 |
2020年 | 3096篇 |
2019年 | 2252篇 |
2018年 | 2673篇 |
2017年 | 2969篇 |
2016年 | 2696篇 |
2015年 | 4109篇 |
2014年 | 5219篇 |
2013年 | 5811篇 |
2012年 | 7059篇 |
2011年 | 7399篇 |
2010年 | 6949篇 |
2009年 | 6858篇 |
2008年 | 7076篇 |
2007年 | 6451篇 |
2006年 | 6182篇 |
2005年 | 4958篇 |
2004年 | 3925篇 |
2003年 | 3434篇 |
2002年 | 4134篇 |
2001年 | 3494篇 |
2000年 | 2227篇 |
1999年 | 1337篇 |
1998年 | 688篇 |
1997年 | 560篇 |
1996年 | 471篇 |
1995年 | 397篇 |
1994年 | 328篇 |
1993年 | 205篇 |
1992年 | 170篇 |
1991年 | 140篇 |
1990年 | 100篇 |
1989年 | 95篇 |
1988年 | 52篇 |
1987年 | 49篇 |
1986年 | 40篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 14篇 |
1978年 | 2篇 |
1960年 | 1篇 |
1959年 | 21篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
21.
Among various carbon materials, diamond stands out due to excellent physical and chemical properties. In this work, we designed Dia@SiO2@Ag composites combining diamond micropowder and Ag nanoparticles by a simple chemical method and obtained stable substrate for surface enhanced Raman scattering (SERS) owing to its high surface-to-volume ratio, low density, as well as close bond between diamond and Ag. As-prepared Dia@SiO2@Ag presented high activity to detect crystal violet and rhodamine 6G molecules, which was demonstrated by significantly enhanced SERS spectra and high enhancement factor values (108-109). Moreover, Dia@SiO2@Ag also showed desired sensitivity, which was investigated by detection limit. Therefore, our study provided more theoretical support and broadened the functional applications of diamond, particularly in Raman detection. 相似文献
22.
Basins with various mineral resources coexisting and enriching often occupy an important strategic position. The exploration of various mineral resources is repetitive at present due to unshared data and imperfect management mechanism. This situation greatly increases the cost of energy exploitation in the country. Traditional data-sharing mode has several disadvantages, such as high cost, difficulty in confirming the right of data, and lack of incentive mechanism, which make achieving real data sharing difficult. In this paper, we propose a data-sharing mechanism based on blockchain and provide implementation suggestions and technical key points. Compared with traditional data-sharing methods, the proposed data-sharing mechanism can realize data sharing, ensure data quality, and protect intellectual property. Moreover, key points in the construction are stated in the case study section to verify the feasibility of the data-sharing system based on blockchain proposed in this paper. 相似文献
23.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes. 相似文献
24.
Yao Dajie Liu Xiaofei Wu Jian 《International Journal of Control, Automation and Systems》2020,18(9):2251-2258
International Journal of Control, Automation and Systems - In this paper, the tracking problem for a class of uncertain nonlinearly parameterized systems with input delay based the adaptive... 相似文献
25.
针对电牵引采煤机渐开线行走轮在ANSYS分析中存在的问题,提出运用APDL语言命令直接建模,并通过VB与ANSYS的交互运行途径,设计了基于VB界面和程序的软件,实现了利用VB界面直接输入参数并调用ANSYS对行走轮自动建模、加载和计算的有限元分析。验证结果表明,该软件减少了设计人员的重复劳动,提高了行走轮的设计效率和水平,具有一定的工程实用价值。 相似文献
26.
The red grape berry pigments, anthocyanins, were characterized in the early 20th century, but investigations of wine pigments were stymied during that era. The question of their identity was a major challenge for wine chemists. A number of techniques showed that the pigments were polymeric in nature. Some structures were postulated by mid-century based on reactions between anthocyanins and condensed tannin, and later postulated wine pigments were observed in model reactions. Some related compounds were then observed in wine. By the end of the 20th century, the ionization of non-volatiles for mass spectrometry opened the door to these compounds. In addition, a new class of compounds was observed, the pyranoanthocyanins, a product of fermentation and aging metabolites with anthocyanins. These compounds possess the pigment stability to SO2 and pH change that is characteristic of aged red wine. Aging experiments show a dynamic situation with shifts in the population of pigment classes over time. The very large number of diverse pigments explains why it has been so difficult to answer the century-old question of the structure of wine pigments. Our current understanding is founded on the use of mass spectral analysis using electrospray and related ionization techniques over the last 25 years. Future progress will rely on more sophisticated analysis of this very complex mixture of substances. © 2019 Society of Chemical Industry 相似文献
27.
Xueliang Wang Huiqin Yin Wenguan Liu Guojun Yu Jian He Zhongfeng Tang Long Yan 《工业材料与腐蚀》2020,71(6):931-937
Understanding the corrosion of molten ZnCl2 on metal surfaces is significant for the corrosion protection of metals, sustainable use of molten salts, preparation of ZnO coatings, and so on. In this paper, surfaces of pure Ni, Cr, and Fe corroded by molten ZnCl2 were investigated. The results show that Ni suffered very slight corrosion, while Cr experienced more serious corrosion than Ni, but lighter corrosion than Fe. The morphology of the corrosion of Cr and Fe, respectively, presented pitting and intergranular corrosion characteristics. Furthermore, nanostructured ZnO coatings were obtained on the surfaces of Ni and Fe, but not on the surface of Cr. The ZnO coating on the Ni surface was doped with a small amount of Zn5(OH)8Cl2, and the ZnO coating on the Fe surface was doped with ZnFe2O4 and Zn2OCl2. The coatings on the Ni and Fe surfaces had an average thickness of 1.5 and 50 μm, respectively. 相似文献
28.
29.
四川盆地上三叠统划分对比研究 总被引:36,自引:6,他引:30
四川盆地上三叠统对比长期存在混乱,给盆地整体评价带来困难。通过岩石地层、地震地层、事件地层及高分辨率旋回地层等多种方法讨论了须家河组与香溪群各岩性段的对比关系,得出了全盆地上三叠统的对比关系;指出须四段底可近似看成等时界面;须家河组下部地层自西向东、向南逐层超覆在雷口坡组之上,上部地层在盆地西北部自东南向西北方向剥蚀层位渐次变老。文章建议四川盆地上三叠统废除“香溪群”,统一使用“须家河组”,以利于对全盆地上三叠统进行油气资源整体评价与深化研究。 相似文献
30.
P(DBF-VA)型柴油低温流动性改进剂的研制 总被引:1,自引:1,他引:0
针对新疆地产柴油蜡含量较高的特点,以游离基聚合法合成了富马酸双链混合酯和醋酸乙烯酯共聚物型[P(DBF-VA)]柴油低温流动改进剂,利用正交实验研究了单体配比,引发剂用量,溶剂用量,聚合温度对聚合物降冷滤效果的影响。共聚物用IR进行表征,利用XRD初步探讨了该降凝剂的降凝机理。结果表明:该剂能使吐哈—10~#、0~#柴油冷滤点降低10℃和7℃;使独山子0~#柴油冷滤点下降12℃;使石化0~#柴油冷滤点下降8℃;使克拉玛依0~#柴油的冷滤点下降8℃。 相似文献