全文获取类型
收费全文 | 222702篇 |
免费 | 18498篇 |
国内免费 | 12367篇 |
专业分类
电工技术 | 34602篇 |
技术理论 | 23篇 |
综合类 | 25014篇 |
化学工业 | 10990篇 |
金属工艺 | 7669篇 |
机械仪表 | 18922篇 |
建筑科学 | 18749篇 |
矿业工程 | 8888篇 |
能源动力 | 8819篇 |
轻工业 | 4804篇 |
水利工程 | 6471篇 |
石油天然气 | 6602篇 |
武器工业 | 3821篇 |
无线电 | 22242篇 |
一般工业技术 | 12133篇 |
冶金工业 | 6715篇 |
原子能技术 | 2349篇 |
自动化技术 | 54754篇 |
出版年
2024年 | 289篇 |
2023年 | 1929篇 |
2022年 | 3677篇 |
2021年 | 4961篇 |
2020年 | 5328篇 |
2019年 | 3904篇 |
2018年 | 3591篇 |
2017年 | 5184篇 |
2016年 | 6243篇 |
2015年 | 7358篇 |
2014年 | 14035篇 |
2013年 | 11942篇 |
2012年 | 16475篇 |
2011年 | 17694篇 |
2010年 | 13370篇 |
2009年 | 13452篇 |
2008年 | 13758篇 |
2007年 | 17530篇 |
2006年 | 15710篇 |
2005年 | 14036篇 |
2004年 | 11476篇 |
2003年 | 10411篇 |
2002年 | 7874篇 |
2001年 | 6555篇 |
2000年 | 5377篇 |
1999年 | 4334篇 |
1998年 | 3244篇 |
1997年 | 2612篇 |
1996年 | 2354篇 |
1995年 | 2023篇 |
1994年 | 1670篇 |
1993年 | 1127篇 |
1992年 | 953篇 |
1991年 | 689篇 |
1990年 | 559篇 |
1989年 | 463篇 |
1988年 | 327篇 |
1987年 | 187篇 |
1986年 | 113篇 |
1985年 | 121篇 |
1984年 | 103篇 |
1983年 | 92篇 |
1982年 | 70篇 |
1981年 | 65篇 |
1980年 | 52篇 |
1979年 | 45篇 |
1978年 | 34篇 |
1977年 | 28篇 |
1976年 | 24篇 |
1959年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
1.
Xiao-Lei Qiu Zi-Rui Fan Yang-Yang Liu Ding-Fu Wang Shi-Xin Wang Chun-Xia Li 《International journal of molecular sciences》2021,22(8)
A self-nanoemulsifying drug delivery system (SNEDDS) was developed to enhance the absorption of heparin after oral administration, in which heparin was compounded with phospholipids to achieve better fat solubility in the form of heparin-phospholipid (HEP-Pc) complex. HEP-Pc complex was prepared using the solvent evaporation method, which increased the solubility of heparin in n-octanol. The successful preparation of HEP-Pc complex was confirmed by differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR) spectroscopy, NMR, and SEM. A heparin lipid microemulsion (HEP-LM) was prepared by high-pressure homogenization and characterized. HEP-LM can enhance the absorption of heparin after oral administration, significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) in mice, and reduce fibrinogen (FIB) content. All these outcomes indicate that HEP-LM has great potential as an oral heparin formulation. 相似文献
2.
3.
本文在环氧涂料中添加玄武岩鳞片,提高其防腐蚀性能。针对玄武岩鳞片的团聚问题,通过机械力化学改性工艺,采用正硅酸四乙酯、HY-311型钛酸酯偶联剂、E-44型环氧树脂对玄武岩鳞片进行杂化包覆,结果表明,杂化包覆后玄武岩鳞片的沉降时间从2h提高至96 h。杂化包覆玄武岩鳞片添加量为20%涂层的性能最优,附着力为13.40 MPa,耐盐雾时间为2000 h,在3.5%NaCl溶液中浸泡2000 h后,0.01 Hz的阻抗模值仍然有5.15×109 Ω·cm2。 相似文献
4.
Michelle Greenough Zeyu Zhao Luiz G. Jacobsohn Jianhua Tong Rajendra K. Bordia 《Journal of the European Ceramic Society》2021,41(12):5882-5889
This study focuses on the chemistry, thermal stability, and electrical conductivity of low/intermediate pyrolysis temperature (700?900 °C) polysiloxane derived ceramics. These ceramics were modified with additional carbon derived from divinylbenzene (DVB) added to the precursor. Their electrical properties were investigated for potential uses in micro-electrical mechanical systems (MEMS) and anodes for lithium batteries. The microstructure and chemical composition was investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS); thermogravimetric analysis (TGA) provided insight into the thermal stability; and electrochemical impedance spectroscopy (EIS) into the electrical properties of the material. The increase of pyrolysis temperature and carbon content lead to an enhancement of the electrical conductivity, higher than previously reported values for intermediate pyrolysis temperature SiOC polymer derived ceramics. A limit of the amount of DVB that can be added to PHMS to produce a hybrid precursor has also been obtained. 相似文献
5.
Power conversion efficiency (PCE) and stability are two important properties of perovskite solar cells (PSCs). Particularly, defects in the perovskite films could cause the generation of trap states, thereby increasing the nonradiative recombination. To address this issue, suitable dopants can be incorporated to react with non-bonded atoms or surface dangling bonds to passivate the defects. Herein, we introduced TiI4 into CH3NH3PbI3 (MAPbI3) film and obtained a dense and uniform morphology with large crystal grains and low defect density. The champion cell based on 0.5% TiI4-doped MAPbI3 achieved a PCE as high as 20.55%, which is superior to those based on pristine MAPbI3 (17.64%). Moreover, the optimal solar cell showed remarkable stability without encapsulation. It retained 88.03% of its initial PCE after 300 h of storage in ambient. This work demonstrates TiI4 as a new and effective passivator for MAPbI3 film. 相似文献
6.
《Ceramics International》2021,47(23):32610-32618
AA7075 + 6%B4C+3%ZrC nano hybrid composite was successfully fabricated, with nano reinforcements composition in AA7075 alloy selected based on previous investigation, to achieve better mechanical performance. Two different sintering techniques, namely conventional and microwave, were implemented to determine the effect on microstructural and mechanical properties. Microstructural investigation was performed with the help of W-SEM. Tensile, compression, and hardness were measured with the help of UTM and Vickers microhardness machine. Porosity was calculated by using Archimedes principle. It was observed that the added nano ZrC particles formed agglomerates and the B4C particles were distributed homogenously. Composites processed by microwave sintering showed excellent mechanical properties compared to the conventionally sintered composites. No intermetallic compounds were detected in microwave sintered composites through XRD analysis, indicating strong and clean interface bonds between matrix and reinforcement particles. High strain to fracture value of 12.24% was noted in microwave sintered nano hybrid composite, while it was 6.12% for conventional sintered one. Fractography revealed no peeling action of reinforcements from the matrix material, and the mode of failure was brittle. It was concluded that, while fabricating nano range hybrid composites, the implementation of advanced sintering technique (microwave sintering) with low sintering temperatures and low sintering times with internal heat generations, helps in eliminating defects that may develop because of high surface energies of nano range reinforcements. 相似文献
7.
邓乐善 《中国水能及电气化》2021,(1):56-58
针对民乐县农村人饮机井水位自动供水系统控制中存在的可靠性低、成本高等问题,文章结合深井泵提取地下水进行供水的实际情况,提出了软启动控制柜+浮球开关+微电脑时间控制器改进的思路和方法,运用效果良好。 相似文献
8.
谭金军 《自动化技术与应用》2021,40(1):181-183
为进一步提升企业思想政治教育工作的信息化水平,本文详细介绍了企业思想政治教育系统的数据库设计方案,以便更加充分地发挥各种多媒体教学设备在企业思想政治教育工作方面的优势。 相似文献
9.
10.