全文获取类型
收费全文 | 22605篇 |
免费 | 1725篇 |
国内免费 | 887篇 |
专业分类
电工技术 | 1169篇 |
技术理论 | 4篇 |
综合类 | 1192篇 |
化学工业 | 4105篇 |
金属工艺 | 1037篇 |
机械仪表 | 1331篇 |
建筑科学 | 1517篇 |
矿业工程 | 570篇 |
能源动力 | 626篇 |
轻工业 | 1487篇 |
水利工程 | 343篇 |
石油天然气 | 1278篇 |
武器工业 | 147篇 |
无线电 | 2903篇 |
一般工业技术 | 2953篇 |
冶金工业 | 1123篇 |
原子能技术 | 184篇 |
自动化技术 | 3248篇 |
出版年
2024年 | 39篇 |
2023年 | 343篇 |
2022年 | 528篇 |
2021年 | 945篇 |
2020年 | 681篇 |
2019年 | 606篇 |
2018年 | 696篇 |
2017年 | 724篇 |
2016年 | 668篇 |
2015年 | 841篇 |
2014年 | 1108篇 |
2013年 | 1428篇 |
2012年 | 1386篇 |
2011年 | 1531篇 |
2010年 | 1227篇 |
2009年 | 1227篇 |
2008年 | 1193篇 |
2007年 | 1134篇 |
2006年 | 1161篇 |
2005年 | 1023篇 |
2004年 | 691篇 |
2003年 | 658篇 |
2002年 | 555篇 |
2001年 | 477篇 |
2000年 | 543篇 |
1999年 | 590篇 |
1998年 | 532篇 |
1997年 | 467篇 |
1996年 | 445篇 |
1995年 | 326篇 |
1994年 | 303篇 |
1993年 | 216篇 |
1992年 | 175篇 |
1991年 | 141篇 |
1990年 | 125篇 |
1989年 | 94篇 |
1988年 | 77篇 |
1987年 | 49篇 |
1986年 | 45篇 |
1985年 | 36篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 31篇 |
1981年 | 22篇 |
1980年 | 16篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
<正>为集中资源优势,打造顶级期刊,助力学科行业发展,《园林》学刊编辑部与同济大学建筑与城市规划学院景观学系于2022年起正式联合办刊。2022年1月4日,《园林》学刊同济大学编辑部揭牌仪式暨学刊发展交流会在同济大学建筑与城市规划学院C1会议室顺利举行。 相似文献
2.
Journal of Materials Science - Silicon is getting much attention as the promising next-generation negative electrode materials for lithium-ion batteries with the advantages of abundance, high... 相似文献
3.
摘 要:为了提高码索引调制(code index modulation,CIM)系统的传输效率,提出了一种具有更低复杂度的单输入单输出(single input single output,SISO)的广义正交码索引调制(generalized orthogonal code index modulation,GQCIM)系统。CIM 系统使用扩频码和星座符号传输信息,但只能激活两个扩频码索引和一个调制符号。而 GQCIM 系统以一种新颖的方式克服了只激活一个调制符号的限制,同时充分利用了调制符号的正交性,增加扩频码索引以传输更多的额外信息位,提高了系统的传输效率。此外,分析了GQCIM系统的理论性能,推导了误码率性能的上界。通过蒙特卡罗仿真验证了GQCIM系统的性能,对比发现GQCIM系统的理论和仿真性能一致。而且在相同的传输效率下,结果显示GQCIM系统的性能优于同样具有正交性的调制系统,如广义码索引调制(generalized code index modulation,GCIM)系统、CIM系统、码索引调制-正交空间调制(code index modulation aided quadrature spatial modulation,CIM-QSM)系统、码索引调制-正交空间调制(code index modulation aided spatial modulation,CIM-SM)系统、脉冲索引调制(pulse index modulation,PIM)系统。 相似文献
4.
5.
Milad Abdalrhman Hussein Sadaam Hadee Khekan Ahlam R. Rashid Mohammed Al-Msari Haitham Tran Tan Huy 《Engineering with Computers》2022,38(4):3625-3637
Engineering with Computers - Over the past few decades, it has been observed a remarkable progression in the development of computer aid models in the field of civil engineering. Machine learning... 相似文献
6.
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.
Fluorinated completely condensed polyhedral oligomeric silsesquioxanes (F-CC-POSSs) are widely utilized as surface modifiers for polymeric materials because of their polyhedral and fluorine-rich structures, which generate polymers with lower surface energies under molecular-level control. In contrast, their derivatives, fluorinated incompletely condensed or open-cage POSSs (F-IC-POSSs), have similarly intriguing structures, but their utilization for polymer synthesis remains undeveloped. Herein, fluorinated network polymers were prepared based on a 3,3,3-trifluoropropyl-substituted IC-POSSs via hydrosilylation polymerization with isobutyl- and phenyl-substituted IC-POSS under optimized conditions. In addition to their good thermal stability and tunable refractive indices, these polymers exhibited solution processability and their casting films showed excellent optical transparency, indicating their potential for constructing fluorinated polymers. Their utilization as surface modifiers was examined by addition to poly(methylmethacrylate) (PMMA) films. Intriguingly, modified PMMA films with 2.0 and 0.5 wt% addition showed similar hydrophobicity and surface energies to the films prepared with only fluorinated network polymers. 相似文献
9.
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
10.
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