全文获取类型
收费全文 | 19785篇 |
免费 | 1295篇 |
国内免费 | 601篇 |
专业分类
电工技术 | 1578篇 |
技术理论 | 2篇 |
综合类 | 2222篇 |
化学工业 | 1072篇 |
金属工艺 | 500篇 |
机械仪表 | 1695篇 |
建筑科学 | 3038篇 |
矿业工程 | 720篇 |
能源动力 | 602篇 |
轻工业 | 560篇 |
水利工程 | 348篇 |
石油天然气 | 524篇 |
武器工业 | 112篇 |
无线电 | 2759篇 |
一般工业技术 | 968篇 |
冶金工业 | 403篇 |
原子能技术 | 278篇 |
自动化技术 | 4300篇 |
出版年
2024年 | 40篇 |
2023年 | 188篇 |
2022年 | 346篇 |
2021年 | 403篇 |
2020年 | 404篇 |
2019年 | 266篇 |
2018年 | 284篇 |
2017年 | 394篇 |
2016年 | 567篇 |
2015年 | 666篇 |
2014年 | 1789篇 |
2013年 | 1193篇 |
2012年 | 1441篇 |
2011年 | 1518篇 |
2010年 | 1167篇 |
2009年 | 1069篇 |
2008年 | 1061篇 |
2007年 | 1516篇 |
2006年 | 1322篇 |
2005年 | 1193篇 |
2004年 | 965篇 |
2003年 | 750篇 |
2002年 | 530篇 |
2001年 | 442篇 |
2000年 | 351篇 |
1999年 | 307篇 |
1998年 | 225篇 |
1997年 | 196篇 |
1996年 | 200篇 |
1995年 | 191篇 |
1994年 | 141篇 |
1993年 | 107篇 |
1992年 | 70篇 |
1991年 | 85篇 |
1990年 | 44篇 |
1989年 | 64篇 |
1988年 | 52篇 |
1987年 | 20篇 |
1986年 | 21篇 |
1985年 | 18篇 |
1984年 | 26篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1963年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
2.
《Advanced Powder Technology》2022,33(12):103879
Heat transfer within ceramic feedstock powders is still unclear, which impedes optimization of the thermal and mechanical properties of the thermal sprayed coatings. The microspheres (yttria-stabilized zirconia YSZ and lanthanum zirconate LZO) were prepared via the electro-spraying assisted phase inversion method (ESP). The thermal properties of the two ESP microspheres and a commercial hollow spherical powder (HOSP) were investigated by using theoretical, experimental, and simulation methods. Thermal conductivity of the single microsphere was estimated via a novel nest model that was derived from the Maxwell-Eucken 1 and the EMT model. Thermal conductivity of a single YSZ/LZO-ESP microsphere prepared at 1100–1200 °C was within 0.36–0.75 W/m K, which was ~ 20 % lower than that of a single YSZ-HOSP microsphere with a similar porosity. Heat flux simulation showed that high tortuosity around the multi-scaled voids of the ESP microsphere led to a more efficient decrease in thermal conductivity compared with total porosity. 相似文献
3.
5.
《International Journal of Hydrogen Energy》2021,46(65):32882-32892
In this work, we explore the application potential of AsP/M2CO2 (M = Sc, Zr) van der Waals heterostructures in photocatalytic water splitting through the first-principles calculations. The calculated results show that AsP/Zr2CO2 heterostructure possesses an unfavorable type-Ⅰ band alignment, whereas AsP/Sc2CO2 exhibits a desirable type-Ⅱ band alignment, which is beneficial for separating the photogenerated electron-hole pairs. Also, the band edge positions of AsP/Sc2CO2 heterostructure stride the redox potential of water, ensuring favorable reaction kinetics. Besides, the strong optical absorption of AsP/Sc2CO2 heterostructure in both visible and ultraviolet regions (especially up to 10−6 cm−1 at about 250 nm) makes it possible to utilize solar energy effectively. Meanwhile, AsP/Sc2CO2 heterostructure has an exciton binding energy as low as 0.09 eV, which quantitatively illustrates the high separation efficiency of photogenerated charge carrier. Thus, the type-Ⅱ band alignment, suitable band edge position, strong light absorption, and low exciton binding energy together indicate that AsP/Sc2CO2 heterostructure is a potential photocatalytic material. In addition, the obvious redshift phenomenon in the optical spectrum of AsP/Sc2CO2 heterostructure shows that biaxial strain can improve its light capture capability. Also, the interconversion between type-Ⅱ and type-Ⅰ can be achieved by applying different strains. All these findings suggest that the novel AsP/Sc2CO2 heterostructure has significant application prospects in next-generation photovoltaic and photocatalytic devices. 相似文献
6.
Thiamine Deficiency Complex (TDC) is an ongoing problem impacting salmonine health in various waterbodies, including Lake Ontario. The prevalence of TDC has been variable and explanations for differences are limited. In the current study, thiamine concentrations were measured in eggs, liver tissue, and muscle tissue sampled from brown trout (Salmo trutta), Chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), lake trout (Salvelinus namaycush), and steelhead trout (O. mykiss) that were collected from Lake Ontario and its surrounding tributaries. The occurrence of TDC was measured for each species based on TDC-induced offspring mortality rates under laboratory conditions. TDC-induced offspring mortality was observed for all species except brown trout. For affected species, egg free thiamine (Th) was consistently low compared to lake trout collected from Lake Superior that are considered thiamine replete. In addition, species with the lowest percentages of Th in their eggs were the most susceptible to TDC, suggesting that limited thiamine reserves in the form of Th may cause TDC-induced offspring mortality. Lastly, our results show that egg thiamine concentrations have yearly variation and increased for all species throughout the study. Reasons for such variation are undetermined; but, if egg thiamine concentrations continue to increase, the impacts of TDC on these salmonine species may lessen. Future monitoring is needed for determining if thiamine concentrations are increasing and the potential impacts that may have on the entire Lake Ontario fishery. 相似文献
7.
8.
《International Journal of Hydrogen Energy》2019,44(30):16015-16027
Urban development has an important influence on the energy consumption of transportation. To develop public transportation is one of the important ways to decrease the energy consumption of urban transportation. It is very urgent to upgrade technology to reduce the energy consumption and emissions of the vehicles constantly. The popularization of hydrogen fuel cell vehicles is the trend of the future automobile industry, which can effectively reduce traffic energy consumption and alleviate urban pollution. This article analyzes the impact of urban development on public transport and private transportation energy consumption from 2013 to 2015; and uses hydrogen fuel cell vehicles alternatives in urban public transport as a scenario. It shows that urban economic development can effectively reduce public transport. Population growth will increase greatly energy consumption of public transport, while larger cities with reasonable spatial density can reduce traffic energy consumption. Moreover, hydrogen fuel cell vehicles can effectively reduce the energy consumption and pollution emissions of urban transportation during operating. Based on the above conclusions, this article will eventually provide targeted recommendations for the development of Chinese cities, public transport, and hydrogen fuel cell vehicles. 相似文献
9.
This paper focuses on the unconditional stability and convergence of characteristics type methods for the time-dependent incompressible MHD equations. For this purpose, we introduce a new characteristics time-discrete system. The optimal error estimates in and norms for the typical modified characteristics finite element method unconditionally can be deduced, while the whole previous works require certain time-step restrictions. Some numerical experiments document performance of the characteristics type methods for the time-dependent incompressible MHD equations. 相似文献
10.
针对谱聚类融合模糊C-means(FCM)聚类的蛋白质相互作用(PPI)网络功能模块挖掘方法准确率不高、执行效率较低和易受假阳性影响的问题,提出一种基于模糊谱聚类的不确定PPI网络功能模块挖掘(FSC-FM)方法。首先,构建一个不确定PPI网络模型,使用边聚集系数给每一条蛋白质交互作用赋予一个存在概率测度,克服假阳性对实验结果的影响;第二,利用基于边聚集系数流行距离(FEC)策略改进谱聚类中的相似度计算,解决谱聚类算法对尺度参数敏感的问题,进而利用谱聚类算法对不确定PPI网络数据进行预处理,降低数据的维数,提高聚类的准确率;第三,设计基于密度的概率中心选取策略(DPCS)解决模糊C-means算法对初始聚类中心和聚类数目敏感的问题,并对预处理后的PPI数据进行FCM聚类,提高聚类的执行效率以及灵敏度;最后,采用改进的边期望稠密度(EED)对挖掘出的蛋白质功能模块进行过滤。在酵母菌DIP数据集上运行各个算法可知,FSC-FM与基于不确定图模型的检测蛋白质复合物(DCU)算法相比,F-measure值提高了27.92%,执行效率提高了27.92%;与在动态蛋白质相互作用网络中识别复合物的方法(CDUN)、演化算法(EA)、医学基因或蛋白质预测算法(MGPPA)相比也有更高的F-measure值和执行效率。实验结果表明,在不确定PPI网络中,FSC-FM适合用于功能模块的挖掘。 相似文献