全文获取类型
收费全文 | 70991篇 |
免费 | 5625篇 |
国内免费 | 2860篇 |
专业分类
电工技术 | 3571篇 |
技术理论 | 10篇 |
综合类 | 4149篇 |
化学工业 | 12432篇 |
金属工艺 | 3880篇 |
机械仪表 | 4389篇 |
建筑科学 | 6022篇 |
矿业工程 | 2049篇 |
能源动力 | 2091篇 |
轻工业 | 4381篇 |
水利工程 | 1140篇 |
石油天然气 | 4422篇 |
武器工业 | 553篇 |
无线电 | 8367篇 |
一般工业技术 | 9110篇 |
冶金工业 | 3608篇 |
原子能技术 | 790篇 |
自动化技术 | 8512篇 |
出版年
2024年 | 289篇 |
2023年 | 1206篇 |
2022年 | 1977篇 |
2021年 | 2704篇 |
2020年 | 2148篇 |
2019年 | 1853篇 |
2018年 | 2029篇 |
2017年 | 2320篇 |
2016年 | 2080篇 |
2015年 | 2736篇 |
2014年 | 3352篇 |
2013年 | 3987篇 |
2012年 | 4359篇 |
2011年 | 4567篇 |
2010年 | 3967篇 |
2009年 | 3754篇 |
2008年 | 3674篇 |
2007年 | 3655篇 |
2006年 | 3858篇 |
2005年 | 3336篇 |
2004年 | 2297篇 |
2003年 | 2003篇 |
2002年 | 1929篇 |
2001年 | 1752篇 |
2000年 | 1756篇 |
1999年 | 2027篇 |
1998年 | 1811篇 |
1997年 | 1487篇 |
1996年 | 1418篇 |
1995年 | 1082篇 |
1994年 | 1034篇 |
1993年 | 714篇 |
1992年 | 549篇 |
1991年 | 441篇 |
1990年 | 330篇 |
1989年 | 262篇 |
1988年 | 238篇 |
1987年 | 149篇 |
1986年 | 105篇 |
1985年 | 80篇 |
1984年 | 38篇 |
1983年 | 36篇 |
1982年 | 40篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
12.
Wei-Li Xie Xiao-Dong Zhang Wen-Hui Liu Qi Xie Guang-Wu Wen Xiao-Xiao Huang Jian-Dong Zhu Fei-Xiang Ma 《稀有金属(英文版)》2019,(3)
SiC nano wires were fabricated on the silicon substrate dipped with a layer of Ni catalyst at 900 ℃ by gas pressure annealing processing. The morphologies and crystal structures were determined by scanning electron microscopy(SEM), transmission electron microscopy(TEM)and X-ray diffraction(XRD). The results show that the assynthesized nanowires are β-SiC single crystalline with diameter range of 50-100 nm, and length of tens of micron by directly annealing at 900 ℃. The SiC nano wires grow along the [111] direction with highly uniform morphology. And the possible growth mechanism of SiC nano wires is proposed.The present work provides an efficient strategy for the production of high-quality SiC nano wires. 相似文献
13.
“Smart firefighting” construction as a part of the “smart city” has been a concern of the public security and fire agencies at all levels. In this study, the status, problems, and reflections of “smart firefighting” construction in China are discussed. A recent survey indicates that China has launched its smart firefighting construction and initially created a new perspective on its regional smart firefighting work based on three main aspects: intelligent disaster perception by Internet of Things (IoT) construction, intelligent disaster prevention by big data construction, and intelligent disaster disposal by emergency rescue platform construction. However, the current smart firefighting construction in China still has some prominent problems such as the data interconnectivity and normalized management of various platforms, the extensibility of smart firefighting platforms, and the intelligent level of smart firefighting researches, which need to be solved urgently. Therefore, we argue that smart firefighting construction in China should establish data interconnectivity, industrial normalized management, 2D/3D geographic information interaction and extension, high-integration fire protection theory, and many other aspects in the near future and truly realize firefighting visualization and efficient data applications for 4D time space. This study could provide valuable reference for smart firefighting and smart city construction. 相似文献
14.
15.
Tingen Zhu Wenping Li Qiqing Wang Yanbo Hu Kaifang Fan Jiafa Du 《Mine Water and the Environment》2020,39(1):57-67
A method to calculate the height of a water-conducting fractured zone (HWCFZ) was developed based on the plate and shell theory, and the development of the HWCFZ in bedrock and Q2l loess strata is discussed in detail. First, the subsidence-deflection curve equation of the overlying stratum is theoretically derived, and then the ultimate deflection and free space height of rock strata are calculated. Moreover, the strata tensile strain is calculated by using integral calculus. In addition, the failure state of the rock is analyzed by comparing the theoretically calculated tensile strain with the experimentally measured yield tensile strain, allowing one to attain the maximum value of HWCFZ. This approach was tested at the Jinjitan coal mine; the theoretically predicted, experimentally measured, and numerically computed maximum HWCFZ values were 189.5, 187.3, and 188.5 m, respectively, demonstrating the accuracy of the proposed method. These results are highly significant for safe and environment-friendly coal mining in northwest Shaanxi, China. 相似文献
16.
17.
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
18.
19.
CO2激光治疗皮肤基底细胞癌14例临床观察 总被引:4,自引:0,他引:4
目的 :探求一种简单 ,安全 ,效果好的基底细胞癌的治疗方法。方法 :对 1 4例基底细胞癌患者在局麻下用CO2 激光行基底细胞癌切除术或切除 +气化术。结果 :患者术中、术后出血少 ,伤口恢复快 ,愈合良好 ,疤痕表浅 ,随访未见复发。结论 :CO2 激光用于治疗基底细胞癌效果良好 ,无明显副作用 ,操作简单值得推广。 相似文献
20.