全文获取类型
收费全文 | 49912篇 |
免费 | 5286篇 |
国内免费 | 2794篇 |
专业分类
电工技术 | 3805篇 |
技术理论 | 4篇 |
综合类 | 3794篇 |
化学工业 | 7624篇 |
金属工艺 | 2725篇 |
机械仪表 | 3417篇 |
建筑科学 | 3994篇 |
矿业工程 | 1697篇 |
能源动力 | 1394篇 |
轻工业 | 3828篇 |
水利工程 | 1070篇 |
石油天然气 | 2381篇 |
武器工业 | 509篇 |
无线电 | 6184篇 |
一般工业技术 | 5719篇 |
冶金工业 | 1963篇 |
原子能技术 | 578篇 |
自动化技术 | 7306篇 |
出版年
2024年 | 256篇 |
2023年 | 898篇 |
2022年 | 1783篇 |
2021年 | 2350篇 |
2020年 | 1802篇 |
2019年 | 1431篇 |
2018年 | 1648篇 |
2017年 | 1823篇 |
2016年 | 1653篇 |
2015年 | 2554篇 |
2014年 | 3039篇 |
2013年 | 3344篇 |
2012年 | 3809篇 |
2011年 | 4017篇 |
2010年 | 3532篇 |
2009年 | 3226篇 |
2008年 | 3091篇 |
2007年 | 2863篇 |
2006年 | 2722篇 |
2005年 | 2266篇 |
2004年 | 1581篇 |
2003年 | 1200篇 |
2002年 | 1045篇 |
2001年 | 867篇 |
2000年 | 850篇 |
1999年 | 764篇 |
1998年 | 614篇 |
1997年 | 551篇 |
1996年 | 511篇 |
1995年 | 441篇 |
1994年 | 315篇 |
1993年 | 257篇 |
1992年 | 216篇 |
1991年 | 125篇 |
1990年 | 131篇 |
1989年 | 142篇 |
1988年 | 84篇 |
1987年 | 41篇 |
1986年 | 31篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 21篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1966年 | 1篇 |
1959年 | 5篇 |
1951年 | 3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.
15.
16.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
17.
Bin Zhang Xuesong Jiang Fei Shen Xueming He Yong Fang Qiuhui Hu 《International Journal of Food Science & Technology》2021,56(6):2588-2595
This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s−1 on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg−1 as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing. 相似文献
18.
19.
为提高稀疏表示跟踪模型性能,提出一种分段加权的反向稀疏跟踪算法,将跟踪问题转化为在贝叶斯框架下寻找概率最高的候选对象问题,构造不同的分段权重函数来分别度量候选目标与正负模板的判别特征系数。通过池化来降低跟踪结果的不确定性干扰,选择正负模板加权系数差值最大的候选表示作为跟踪结果。实验表明,在光照变化、遮挡、快速运动、运动模糊情况下,所提出的算法可以确保跟踪结果的准确性和鲁棒性。 相似文献
20.