全文获取类型
收费全文 | 78255篇 |
免费 | 18063篇 |
国内免费 | 1806篇 |
专业分类
电工技术 | 3013篇 |
技术理论 | 3篇 |
综合类 | 2836篇 |
化学工业 | 24005篇 |
金属工艺 | 2811篇 |
机械仪表 | 3043篇 |
建筑科学 | 4888篇 |
矿业工程 | 1327篇 |
能源动力 | 1867篇 |
轻工业 | 9591篇 |
水利工程 | 959篇 |
石油天然气 | 2990篇 |
武器工业 | 273篇 |
无线电 | 11474篇 |
一般工业技术 | 16085篇 |
冶金工业 | 2719篇 |
原子能技术 | 553篇 |
自动化技术 | 9687篇 |
出版年
2024年 | 192篇 |
2023年 | 690篇 |
2022年 | 1249篇 |
2021年 | 1898篇 |
2020年 | 2697篇 |
2019年 | 4144篇 |
2018年 | 4242篇 |
2017年 | 4725篇 |
2016年 | 4932篇 |
2015年 | 5441篇 |
2014年 | 5759篇 |
2013年 | 7319篇 |
2012年 | 5167篇 |
2011年 | 5020篇 |
2010年 | 4981篇 |
2009年 | 4648篇 |
2008年 | 4145篇 |
2007年 | 3858篇 |
2006年 | 3761篇 |
2005年 | 3250篇 |
2004年 | 2744篇 |
2003年 | 2616篇 |
2002年 | 2689篇 |
2001年 | 2329篇 |
2000年 | 2149篇 |
1999年 | 1651篇 |
1998年 | 989篇 |
1997年 | 838篇 |
1996年 | 777篇 |
1995年 | 638篇 |
1994年 | 528篇 |
1993年 | 421篇 |
1992年 | 318篇 |
1991年 | 240篇 |
1990年 | 180篇 |
1989年 | 149篇 |
1988年 | 130篇 |
1987年 | 100篇 |
1986年 | 75篇 |
1985年 | 56篇 |
1984年 | 34篇 |
1983年 | 40篇 |
1982年 | 48篇 |
1981年 | 38篇 |
1980年 | 31篇 |
1978年 | 19篇 |
1977年 | 39篇 |
1976年 | 25篇 |
1974年 | 19篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Baofeng Hou Hong He Ruixiu Jia Meilong Fu Yanbin Cao Shaoqun He Liwen Luo Youqing Huang 《应用聚合物科学杂志》2019,136(10):47161
The synthesis and performance of a novel temperature-tolerant foamed resin for enhanced oil recovery were investigated using various methods, including infrared, NMR, scanning electron microscopy (SEM), and displacement experiments. Polycondensation of furfuryl alcohol prepolymers was confirmed by the infrared and NMR results. The poor temperature tolerance of furfuryl alcohol prepolymers after gelation at high temperatures is mainly due to the fracture of furan rings. The addition of ester additives is an effective method of increasing the temperature tolerance of the prepared foamed resins and can effectively reduce the weight-loss rate of the polycondensation products. The SEM results show that the skeleton structure of the foamed resin remains intact after high-temperature treatment. Thus, the novel plugging agent system has excellent thermal stability and still has a high strength (>0.8 MPa) after high-temperature aging treatment for 40 days, giving the prepared foamed resin a good plugging performance (plugging rate > 91%) at 250 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47161. 相似文献
42.
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
43.
44.
45.
Jincy Joy Jessica Pereira Rachida Aid‐Launais Graciela Pavon‐Djavid Alok R Ray Didier Letourneur Anne Meddahi‐Pell Bhuvanesh Gupta 《Polymer International》2019,68(7):1367-1377
The work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry 相似文献
46.
基于目前中国改进型三环路压水堆(CPR1000)部分机组存在因中间量程电流饱和导致无法在48%额定功率(Pn)完成定值标定及核电厂大修经济性考虑,采用MCNP程序及核设计软件包SCIENCE,研究分析中间量程保护定值标定的新方法。分析结果表明,中间量程保护定值标定调整至30%Pn功率平台实施,采用改进方法标定的保护定值更接近于设计值。 相似文献
47.
48.
Joon‐Young Jun Sosuke Nakajima Koji Yamazaki Yuji Kawai Hajime Yasui Yasuyuki Konishi 《International Journal of Food Science & Technology》2015,50(4):871-877
Cystoseira hakodatensis is an unutilised brown algae belonging to family Sargassaceae. A crude methanol extract from the algae showed inhibitory effects on the growths of Bacillus cereus and Bacillus licheniformis. To isolate the major antimicrobial agent, a sequential active‐guided isolation procedure was applied: liquid–liquid extraction, column chromatography and bio‐autography. A marked antimicrobial agent (active α) was isolated in hydrophobic fraction and was determined to phenolics without carbohydrates and proteins by phytochemical test. Regarding the antimicrobial potential, the isolated active α showed better inhibitory effects against B. cereus and B. licheniformis at 2 and 4 times of lower concentrations (62.5 and 31.3 μg mL?1) in comparison with epigallocatechin gallate. These results showed that C. hakodatensis is a potential source of antimicrobial agent capable of preventing the growth of the two bacteria. 相似文献
49.
50.