全文获取类型
收费全文 | 322618篇 |
免费 | 26362篇 |
国内免费 | 16571篇 |
专业分类
电工技术 | 19246篇 |
技术理论 | 52篇 |
综合类 | 41381篇 |
化学工业 | 47078篇 |
金属工艺 | 14196篇 |
机械仪表 | 17089篇 |
建筑科学 | 40199篇 |
矿业工程 | 16229篇 |
能源动力 | 10179篇 |
轻工业 | 23156篇 |
水利工程 | 14824篇 |
石油天然气 | 14466篇 |
武器工业 | 2980篇 |
无线电 | 20218篇 |
一般工业技术 | 25669篇 |
冶金工业 | 17731篇 |
原子能技术 | 3755篇 |
自动化技术 | 37103篇 |
出版年
2024年 | 893篇 |
2023年 | 3239篇 |
2022年 | 6008篇 |
2021年 | 7750篇 |
2020年 | 7954篇 |
2019年 | 7045篇 |
2018年 | 6463篇 |
2017年 | 7723篇 |
2016年 | 9164篇 |
2015年 | 10051篇 |
2014年 | 17885篇 |
2013年 | 17171篇 |
2012年 | 21789篇 |
2011年 | 22940篇 |
2010年 | 17877篇 |
2009年 | 18696篇 |
2008年 | 17201篇 |
2007年 | 22574篇 |
2006年 | 21424篇 |
2005年 | 18664篇 |
2004年 | 15945篇 |
2003年 | 14421篇 |
2002年 | 11928篇 |
2001年 | 10139篇 |
2000年 | 8527篇 |
1999年 | 7038篇 |
1998年 | 5407篇 |
1997年 | 4741篇 |
1996年 | 4301篇 |
1995年 | 3699篇 |
1994年 | 3243篇 |
1993年 | 2444篇 |
1992年 | 2156篇 |
1991年 | 1627篇 |
1990年 | 1409篇 |
1989年 | 1206篇 |
1988年 | 971篇 |
1987年 | 654篇 |
1986年 | 469篇 |
1985年 | 447篇 |
1984年 | 417篇 |
1983年 | 301篇 |
1982年 | 275篇 |
1981年 | 194篇 |
1980年 | 156篇 |
1979年 | 125篇 |
1978年 | 69篇 |
1977年 | 77篇 |
1976年 | 62篇 |
1975年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Bijan Nasri‐Nasrabadi Akif Kaynak Shayan Seyedin Zahra Komeily‐Nia Abbas Z Kouzani 《Polymer International》2019,68(5):922-928
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry 相似文献
22.
目的建立超高效液相色谱-串联质谱法同时测定糕点中6种常用合成甜味剂的分析方法。方法选用超纯水作为提取溶剂,涡旋和超声提取后,低温离心,取部分上清液加入正己烷除脂,Waters Atlantis■T3色谱柱、甲醇-5 mmol/L甲酸铵(含0.1%甲酸)作为流动相、亲水亲脂平衡型固相萃取柱HLB(hydrophile-lipophile balance)净化。结果6种甜味剂在质量浓度为10~200 ng/mL的曲线范围内呈良好线性关系,相关系数r均大于0.999,平均加标回收率在85.0%-98.2%之间,相对平均偏差(relative standard deviation,RSD)为1.3%~6.7%。结论该方法具有前处理简单、灵敏度高、检测速度快等优点,适合糖精钠、甜蜜素、三氯蔗糖、阿斯巴甜、阿力甜、纽甜的检测,但不适用于安赛蜜的检测。 相似文献
23.
Elli Ntakou Ralph Masiello Farnaz Farzan Shay Bahramirad Aleksi Paaso M.A. Nayeem Maigha Maigha Daniel Kushner 《The Electricity Journal》2019,32(4):45-49
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal. 相似文献
24.
25.
26.
An electrolyte Equation of State is presented by combining the Cubic Plus Association Equation of State,Mean Spherical Approximation and the Born equation.This new model uses experimental relative static permittivity,intend to predict well the activity coefficients of individual ions (ACI) and liquid densities of aqueous solutions.This new model is applied to model water + NaCl binary system and water + gas +NaCl ternary systems.The cation/anion-water interaction parameters of are obtained by fitting the exper-imental data of ACI,mean ionic activity coefficients (MIAC) and liquid densities of water + NaCl binary system.The cation/anion-gas interaction parameters are obtained by fitting the experimental data of gas solubilities in aqueous NaCl solutions.The modeling results show that this new model can correlate well with the phase equilibrium and volumetric properties.Without gas,predictions for ACI,MIAC,and liquid densities present relative average deviations of 1.3%,3.6% and 1.4% compared to experimental ref-erence values.For most gas-containing systems,predictions for gas solubilities present relative average deviations lower than 7.0%.Further,the contributions of ACI,and salting effects of NaCl on gases are ana-lyzed and discussed. 相似文献
27.
The effect of the emergency perception of bystanders of cyberbullying victims on helping behaviors is often neglected in research on cyberbullying. In this study, we explored the influence of this cognitive factor on cyber-bystanders’ helping tendencies as well as elucidated possible underlying processes. The results of two studies were reported. In Study 1, 150 undergraduates read a true case of a girl experiencing cyberbullying. The results indicated that when the participants perceived the victim’s situation to be more critical (i.e., higher emergency perception), their helping tendencies were stronger, partly through increased state empathy followed by feelings of responsibility to help. In Study 2, we randomly assigned 300 undergraduates to two groups. The low emergency group read the same cyberbullying case as Study 1, whereas the cyberbullying case read by the high emergency group contained additional emergency information of the victim. The results indicated that the high emergency group expressed stronger helping tendencies than did the low emergency group. This effect was caused by a stronger perception that the victim was in an emergency situation, which not only strengthened the participants’ helping tendencies directly but also indirectly through increasing their state empathy and feelings of responsibility to help. 相似文献
28.
29.
Zachary Zander Deirdre Newton Heather Scaglione Averie Reiber Parminder Agarwal 《Polymer Engineering and Science》2021,61(12):3029-3036
The incursion of microbial growth on polymeric products can deteriorate their performance and lead to the development of undesirable staining and odors. A growing trend in the industry has aimed to reduce microbial populations on high-touch surfaces via the use of antimicrobials to protect material aesthetics and durability or to prevent the spread of pathogenic microorganisms. In this study, a variety of plastic substrates (30 unique polymer compounds), including poly(acrylonitrile-co-butadiene-co-styrene), poly(butylene terephthalate), poly(etherimide), various thermoplastic elastomers (TPEs), poly(carbonates), and poly(amides), were screened for susceptibility to microbial attack using American Society for Testing and Materials (ASTM) G21 (fungi susceptibility), Japanese Industrial Standard (JIS) Z2801, and modified ASTM E1428-15a (bacterial susceptibility) test standards. TPEs were determined to be most susceptible to microbial attack under the appropriate environmental conditions. Subsequent studies assessed the use of an antimicrobial additive, zinc pyrithione (ZPT), for potential efficacy in a variety of TPE blends for diverse target market applications. ZPT proved to be very effective in protecting TPEs, reducing Staphylococcus aureus and Escherichia coli populations by 99.9% or more in JIS Z2801 testing and inhibiting fungal growth (rating = 0) according to the ASTM G21 standard. 相似文献