全文获取类型
收费全文 | 52317篇 |
免费 | 2185篇 |
国内免费 | 5933篇 |
专业分类
电工技术 | 3119篇 |
技术理论 | 4篇 |
综合类 | 6260篇 |
化学工业 | 6196篇 |
金属工艺 | 6094篇 |
机械仪表 | 3165篇 |
建筑科学 | 2877篇 |
矿业工程 | 1364篇 |
能源动力 | 1143篇 |
轻工业 | 2991篇 |
水利工程 | 1131篇 |
石油天然气 | 4977篇 |
武器工业 | 459篇 |
无线电 | 5831篇 |
一般工业技术 | 4746篇 |
冶金工业 | 1876篇 |
原子能技术 | 1626篇 |
自动化技术 | 6576篇 |
出版年
2024年 | 28篇 |
2023年 | 301篇 |
2022年 | 419篇 |
2021年 | 720篇 |
2020年 | 574篇 |
2019年 | 500篇 |
2018年 | 548篇 |
2017年 | 623篇 |
2016年 | 518篇 |
2015年 | 700篇 |
2014年 | 1232篇 |
2013年 | 1516篇 |
2012年 | 1671篇 |
2011年 | 5261篇 |
2010年 | 2962篇 |
2009年 | 2134篇 |
2008年 | 2152篇 |
2007年 | 1777篇 |
2006年 | 2029篇 |
2005年 | 2134篇 |
2004年 | 4848篇 |
2003年 | 3240篇 |
2002年 | 3071篇 |
2001年 | 2066篇 |
2000年 | 1566篇 |
1999年 | 2358篇 |
1998年 | 1781篇 |
1997年 | 1725篇 |
1996年 | 1105篇 |
1995年 | 874篇 |
1994年 | 746篇 |
1993年 | 2143篇 |
1992年 | 1675篇 |
1991年 | 1198篇 |
1990年 | 1164篇 |
1989年 | 880篇 |
1988年 | 622篇 |
1987年 | 353篇 |
1986年 | 273篇 |
1985年 | 147篇 |
1984年 | 99篇 |
1983年 | 64篇 |
1982年 | 72篇 |
1981年 | 53篇 |
1980年 | 88篇 |
1979年 | 71篇 |
1977年 | 28篇 |
1965年 | 62篇 |
1958年 | 26篇 |
1957年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
1.
Ningyu Chen Jintang Zhou Zhengjun Yao Yiming Lei Ruiyang Tan Yuxin Zuo Wenjian Zheng Zibao Jiao 《Ceramics International》2021,47(8):10545-10554
The electromagnetic materials are featured by good magnetic permeability and dielectric constant characteristics, which are of significant importance in solving the pollution problem of electromagnetic. In this study, after the complete of the use of sol-gel method, argon gas was then introduced for calcination, and eventually a new type of MWCNTs/Ni0.5Zn0.5Nd0.04Fe1.96O4 composites was synthesized after the above mentioned procedures. The synthesized MWCNTs were able to be adsorbed on the surface of Ni0.5Zn0.5Nd0.04Fe1.96O4 and could form a good conductive work of 3D. Also, the effect of additional MWCNTs on microwave absorption properties of MWCNTs/Ni0.5Zn0.5Nd0.04Fe1.96O4 composites were also observed in this study. The results indicate that the additional MWCNTs function to significantly improve the microwave absorption property of MWCNTs/Ni0.5Zn0.5Nd0.04Fe1.96O4. Through altering the amount of MWCNTs, the microwave attenuation performance and impedance matching coefficient of this electromagnetic materials can be effectively improved. The S2 sample presented a minimum reflection loss of ?35.05 dB when its thickness reached 1.6 mm, meanwhile, the effective absorption bandwidth achieved 4.55 GHz. The prepared composites perform well in microwave absorption, which can attribute to the reasonable ratio of composites as well as its interaction with both of the magnetic and dielectric components. This research paved the way for novel ideas to be put in the electromagnetic absorption materials with high-efficient. 相似文献
2.
Wan-Li Tan Dr. Chun Zhang Yang Li Dr. Kai Guo Dr. Xiao-Wei Gao Dr. Jun Wei Dr. Dong Yi Prof. Lin Pu Prof. Dr. Qin Wang 《ChemMedChem》2021,16(23):3569-3575
Forty samples of optically active falcarindiol analogues are synthesized by using the easily available C2 symmetric (R)- and (S)-1,1’-binaphth-2-ol (BINOL) in combination with Ti(OiPr)4, Zn powder and EtI. Their anticancer activities on Hccc-9810, HepG2, MDA-MB-231, Hela, MG-63 and H460 cells are assayed to elucidate their structure-activity relationships. These results showed that the falcarindiol analogue (3R,8S)- 2 i with the terminal double bond has the most potent anti-proliferation effect on Hccc-9810 cells with IC50 value of 0.46 μM. The falcarindiol analogue (3R,8S)- 2 i can induce obvious Hccc-9810 cell apoptosis in a concentration-dependent manner by Hoechst staining and flow cytometry analysis. The proposed mechanism suggests that the falcarindiol analogue (3R,8S)- 2 i increases LDH release and MDA content, and reduces the levels of SOD activity, which lead to the accumulation of oxidative stress and induce apoptosis in Hccc-9810 cells. 相似文献
3.
Phuong-Anh Ngoc Doan Tzyi-Horng Tan Lee Fong Siow Beng Ti Tey Eng Seng Chan Teck-Kim Tang Nur Azwani Abdul Karim Eng-Tong Phuah Yee-Ying Lee 《Journal of the American Oil Chemists' Society》2021,98(6):609-620
Palm fatty acid distillate (PFAD) is a rich source of vitamin E. As compared to other vegetable oil, PFAD has higher tocotrienol (70–80%) over tocopherol content, which makes it a valuable source for vitamin E extraction. Current vitamin E extraction methods are not sustainable due to the intensive usage of chemical and high operational cost. Hence, the present study investigated for the first time using dry fractionation process as a green and economical pretreatment method for separating solid fraction (stearin) and liquid fraction (olein) in order to concentrate vitamin E from PFAD in olein fraction. We examined the dry fractionation conditions: crystallization ending temperature (36–44 °C), cooling rate (0.3 and 1.5°C min−1), stirring speed (20–125 rpm), and holding time (0–60 min) on the composition of unsaturated and saturated fatty acids as well as vitamin E content in liquid fraction (olein) and solid fraction (stearin) using gas chromatography and high performance liquid chromatography, respectively. In most of these conditions, vitamin E was ultimately higher in olein fraction as compared to stearin fraction, which is correlated with the high degree of unsaturation. Under a cooling rate of 0.3°C min−1, 90 rpm stirring speed, and ending crystallization of 38 °C, the highest vitamin E rich olein fraction was attained with 1479 ± 10.51 ppm in 50 g olein fraction as compared to 1366 ± 7.94 ppm in 500 g of unfractionated PFAD. 相似文献
4.
针对重型针对重型燃气轮机控制系统传感器解析余度的构建问题,提出了一种机理数据协同驱动的控制系统 参数解析余度构建方法。首先基于重型燃气轮机工作原理,建立参数的机理模型;然后引人网络架构搜索法 得到最优前馈神经网络结构,通过前馈神经网络训练机理模型的误差,得到数据驱动模型,将其作为机理模 型的补偿部分,补偿部分提高了参数解析的精度。仿真结果表明本文提出的参数解析方法的有效性,用该方 法可获得精准的解析模型。
燃气轮机控制系统传感器解析余度的构建问题,提出了一种机理数据协同驱动的控制系统 参数解析余度构建方法。首先基于重型燃气轮机工作原理,建立参数的机理模型;然后引人网络架构搜索法 得到最优前馈神经网络结构,通过前馈神经网络训练机理模型的误差,得到数据驱动模型,将其作为机理模 型的补偿部分,补偿部分提高了参数解析的精度。仿真结果表明本文提出的参数解析方法的有效性,用该方 法可获得精准的解析模型。 相似文献
5.
6.
Buhari Adamu Muhammad Ooi Chee-Pun Baskaran Vishnu Monn Phan Raphael CW Wong KokSheik Tan Wooi-Haw 《Multimedia Tools and Applications》2022,81(7):9151-9176
Multimedia Tools and Applications - The interest in real-time micro-expression recognition has increased with the current trend in human-computer interaction applications. Presently, there are... 相似文献
7.
Da-Wang Tan Zhen-Yong Lao Zhan Zhang Wei-Ming Guo Shi-Kuan Sun Hua-Tay Lin 《Journal of the American Ceramic Society》2021,104(6):2860-2867
B4C-TiB2 ceramics (TiB2 ranging 5~70 vol%) with Mo-Co-WC as the sintering additive were prepared by spark plasma sintering. In comparison with B4C-TiB2 without additive, the enhanced densification was evident in the sintered specimen with Mo-Co-WC additive. Core-rim structured grain was observed around TiB2 grains. The interface of the rim between TiB2 and B4C phases demonstrated different feature: the inner borderline of the rim exhibited a smooth feature, whereas a sharp curved grain boundary was observed between the rim and the B4C grain. The formation mechanism is discussed: the epitaxial growth of (Ti,Mo,W)B2 rim around the TiB2 core may occur as a result of the solid solution and dissolution-precipitation between TiB2 phase and the sintering additive. It was revealed that the fracture toughness increased as the content of TiB2 content increased, alongside the decreased hardness. B4C-30 vol% TiB2 specimen demonstrated the optimal combination of mechanical properties, reaching Vickers hardness of 24.3 GPa and fracture toughness of 3.33 MPa·m1/2. 相似文献
8.
Qian Wu Xiangmei Liu Bo Li Lei Tan Yong Han Zhaoyang Li Yanqin Liang Zhenduo Cui Shengli Zhu Shuilin Wu Yufeng Zheng 《材料科学技术学报》2021,67(8):70-79
Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection. 相似文献
9.
10.
The pH-responsive microgels (MGs) consisting of methacrylic acid-ethyl acrylate (MAA-EA), methacrylic acid-butyl methacrylate (MAA-BMA) or methacrylic acid-methyl methacrylate (MAA-MMA) crosslinked with di-allyl phthalate (DAP) were synthesized via emulsion polymerization. It was found that the energy required to extract a proton from MGs with higher glass-transition temperature (Tg) was greater than at a lower Tg. Procaine hydrochloride (PrHy) was used to study the release of a model hydrophobic drug from MGs with different Tgs. A drug selective electrode (DSE) was used to monitor the release as a function of pHs and Tgs. With increasing pH or decreasing Tg, the swelling of MGs was enhanced, leading to greater release of the drug. From the Berens and Hopfenberg model, the contributions of chain relaxation and diffusion processes during a release process were determined. The drug release from lower Tg MGs and at high pH is dominated by diffusion rather than chain relaxation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47284. 相似文献