全文获取类型
收费全文 | 89893篇 |
免费 | 8430篇 |
国内免费 | 5157篇 |
学科分类
工业技术 | 103480篇 |
出版年
2024年 | 212篇 |
2023年 | 1015篇 |
2022年 | 1856篇 |
2021年 | 2867篇 |
2020年 | 2212篇 |
2019年 | 2043篇 |
2018年 | 2087篇 |
2017年 | 2364篇 |
2016年 | 2354篇 |
2015年 | 3219篇 |
2014年 | 4383篇 |
2013年 | 5206篇 |
2012年 | 6125篇 |
2011年 | 6686篇 |
2010年 | 6287篇 |
2009年 | 6148篇 |
2008年 | 6038篇 |
2007年 | 5797篇 |
2006年 | 5722篇 |
2005年 | 4687篇 |
2004年 | 3883篇 |
2003年 | 3591篇 |
2002年 | 4279篇 |
2001年 | 3651篇 |
2000年 | 2486篇 |
1999年 | 1872篇 |
1998年 | 1213篇 |
1997年 | 991篇 |
1996年 | 879篇 |
1995年 | 747篇 |
1994年 | 566篇 |
1993年 | 425篇 |
1992年 | 345篇 |
1991年 | 269篇 |
1990年 | 232篇 |
1989年 | 149篇 |
1988年 | 141篇 |
1987年 | 85篇 |
1986年 | 47篇 |
1985年 | 54篇 |
1984年 | 43篇 |
1983年 | 33篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
12.
Xian Suo Xili Cui Lifeng Yang Nan Xu Yuqi Huang Yi He Sheng Dai Huabin Xing 《Advanced materials (Deerfield Beach, Fla.)》2020,32(29):1907601
The design of highly stable and efficient porous materials is essential for developing breakthrough hydrocarbon separation methods based on physisorption to replace currently used energy-intensive distillation/absorption technologies. Efforts to develop advanced porous materials such as zeolites, coordination frameworks, and organic polymers have met with limited success. Here, a new class of ionic ultramicroporous polymers (IUPs) with high-density inorganic anions and narrowly distributed ultramicroporosity is reported, which are synthesized by a facile free-radical polymerization using branched and amphiphilic ionic compounds as reactive monomers. A covalent and ionic dual-crosslinking strategy is proposed to manipulate the pore structure of amorphous polymers at the ultramicroporous scale. The IUPs exhibit exceptional selectivity (286.1–474.4) for separating acetylene from ethylene along with high thermal and water stability, collaboratively demonstrated by gas adsorption isotherms and experimental breakthrough curves. Modeling studies unveil the specific binding sites for acetylene capture as well as the interconnected ultramicroporosity for size sieving. The porosity-engineering protocol used in this work can also be extended to the design of other ultramicroporous materials for the challenging separation of other key gas constituents. 相似文献
13.
14.
Su-Il Ri Song-Il Hong Jong-Chol Kim Ju-Hyok Wi 《International Journal of Hydrogen Energy》2021,46(5):3319-3328
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance. 相似文献
15.
16.
Choi Paul Santos Christian Ariane Kim Min-Kun Jung Hyunsook Hong Do-Young Koo Junemo 《Journal of Mechanical Science and Technology》2021,35(11):5007-5022
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations... 相似文献
17.
18.
Xiaohui Hu Li Cheng Yan Hong Zhaofeng Li Caiming Li Zhengbiao Gu 《International Journal of Food Science & Technology》2021,56(8):4149-4158
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%. 相似文献
19.
针对互联网中恶意域名攻击事件频发,现有域名检测方法实时性不强的问题,提出一种基于词法特征的恶意域名快速检测算法。该算法根据恶意域名的特点,首先将所有待测域名按照长度进行正则化处理后赋予权值;然后利用聚类算法将待测域名划分成多个小组,并利用改进的堆排序算法按照组内权值总和计算各域名小组优先级,根据优先级降序依次计算各域名小组中每一域名与黑名单上域名之间的编辑距离;最后依据编辑距离值快速判定恶意域名。算法运行结果表明,基于词法特征的恶意域名快速检测算法与单一使用域名语义和单一使用域名词法的恶意域名检测算法相比,准确率分别提高1.7%与2.5%,检测速率分别提高13.9%与6.8%,具有更高的准确率和实时性。 相似文献
20.