全文获取类型
收费全文 | 46410篇 |
免费 | 3422篇 |
国内免费 | 1385篇 |
专业分类
电工技术 | 2082篇 |
技术理论 | 4篇 |
综合类 | 2345篇 |
化学工业 | 7702篇 |
金属工艺 | 2255篇 |
机械仪表 | 2422篇 |
建筑科学 | 2674篇 |
矿业工程 | 1086篇 |
能源动力 | 1502篇 |
轻工业 | 2764篇 |
水利工程 | 634篇 |
石油天然气 | 1768篇 |
武器工业 | 217篇 |
无线电 | 6758篇 |
一般工业技术 | 6655篇 |
冶金工业 | 3360篇 |
原子能技术 | 504篇 |
自动化技术 | 6485篇 |
出版年
2024年 | 55篇 |
2023年 | 668篇 |
2022年 | 873篇 |
2021年 | 1587篇 |
2020年 | 1305篇 |
2019年 | 1080篇 |
2018年 | 1281篇 |
2017年 | 1345篇 |
2016年 | 1254篇 |
2015年 | 1501篇 |
2014年 | 1985篇 |
2013年 | 2779篇 |
2012年 | 2731篇 |
2011年 | 3122篇 |
2010年 | 2495篇 |
2009年 | 2542篇 |
2008年 | 2615篇 |
2007年 | 2347篇 |
2006年 | 2233篇 |
2005年 | 1867篇 |
2004年 | 1522篇 |
2003年 | 1541篇 |
2002年 | 1722篇 |
2001年 | 1399篇 |
2000年 | 1048篇 |
1999年 | 966篇 |
1998年 | 1231篇 |
1997年 | 933篇 |
1996年 | 774篇 |
1995年 | 646篇 |
1994年 | 545篇 |
1993年 | 454篇 |
1992年 | 337篇 |
1991年 | 290篇 |
1990年 | 301篇 |
1989年 | 227篇 |
1988年 | 203篇 |
1987年 | 169篇 |
1986年 | 144篇 |
1985年 | 129篇 |
1984年 | 112篇 |
1983年 | 82篇 |
1982年 | 76篇 |
1981年 | 62篇 |
1980年 | 84篇 |
1979年 | 53篇 |
1978年 | 60篇 |
1977年 | 58篇 |
1976年 | 76篇 |
1975年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
2.
3.
Cuiping Yu Shuang Sun Sihui Li Huijia Yan Henan Zou 《International Journal of Food Science & Technology》2022,57(2):1173-1185
In this study, the effect of high-intensity ultrasound (HIUS) (200 and 400 W for 0, 5, 10 and 15 min respectively) on conformational changes, physicochemical, rheological and emulsifying properties of scallop (Patinopecten yessoensis) myofibrillar protein (SMP) was investigated. HIUS-treated SMP had lower α-helix content and higher β-sheet content compared with the native SMP. HIUS treatment induced the unfolding of SMP and increased the surface hydrophobicity. The particle size of SMP decreased and the absolute zeta-potential increased after ultrasonication, which in turn increased the solubility of SMP. The conformational changes and the improvement of physicochemical properties of SMP increased the ability for SMP to lower the interfacial tension at the oil–water interface and increased the percentage of adsorbed protein. As a result, the emulsifying properties, rheological properties of SMP and storage stability of emulsions were also improved. In conclusion, HIUS treatment has future potential for improving the emulsifying properties of SMP. 相似文献
4.
5.
Yinjuan Cao Shunzhong He Qunli Yu Ling Han Wei Zhang Xiaohong Zou 《International Journal of Food Science & Technology》2022,57(5):3001-3011
This study investigated the effect of 5 freeze–thaw cycles (freezing at −18°C for 12 h and then thawing at 4°C for approximately 12 h) on the meat quality, proximate composition, water distribution and microstructure of bovine rumen smooth muscle (BSM). As the number of freeze–thaw cycles increased, BSM pH, shear force, water content and protein content decreased by 3.06%, 35.50%, 14.49% and 21.11%, respectively, whereas BSM thawing loss, cooking loss, pressing loss, total aerobic count (TAC), ash content and fat content increased by 108.12%, 47.75%, 78.33%, 90.99%, 105% and 35.20%, respectively. The freeze–thaw cycles resulted in greater protein and lipid oxidation, as evidenced by a 36.46% reduction in the sulfhydryl content and a 209.06% and 338.46% increase in the carbonyl and malondialdehyde contents, respectively. Ice crystal formation disrupted the structural integrity of the muscle tissue. Low-field nuclear magnetic resonance results showed that the freeze–thaw cycles prolonged the relaxation times (T2b, T21 and T22), indicating that immobile water shifted to free water, and consequently, free water mobility increased. After 3 freeze–thaw cycles, the decline in shear force slowed, the increase in thawing loss became accelerated, and the TAC approached the domain value (6 log colony-forming units/g). Therefore, the number of freeze–thaw cycles of smooth muscle during transport, storage and distribution should be controlled to 3 or fewer. The current results provide a theoretical basis and data support for the further utilisation and culinary processing of smooth muscle. 相似文献
6.
7.
8.
Jinming Wang Meng Yang Guodong Zou Di Liu Qiuming Peng 《Advanced functional materials》2021,31(21):2101180
Lithium (Li) metal, as an appealing candidate for the next-generation of high-energy-density batteries, is plagued by its safety issue mainly caused by uncontrolled dendrite growth and infinite volume expansion. Developing new materials that can improve the performance of Li-metal anode is one of the urgent tasks. Herein, a new MXene derivative containing pure rutile TiO2 and N-doped carbon prepared by heat-treating MXene under a mixing gas, exhibiting high chemical activity in molten Li, is reported. The lithiation MXene derivative with a hybrid of LiTiO2-Li3N-C and Li offers outstanding electrochemical properties. The symmetrical cell assembling lithiation MXene derivative hybrid anode exhibits an ultra-long cycle lifespan of 2000 h with an overpotential of ≈30 mV at 1 mA cm−2, which overwhelms Li-based anodes reported so far. Additionally, long-term operations of 34, 350, and 500 h at 10 mA cm−2 can be achieved in symmetrical cells at temperatures of −10, 25, and 50 °C, respectively. Both experimental tests and density functional theory calculations confirm that the LiTiO2-Li3N-C skeleton serves as a promising host for Li infusion by alleviating volume variation. Simultaneously, the superlithiophilic interphase of Li3N guides Li deposition along the LiTiO2-Li3N-C skeleton to avoid dendrite growth. 相似文献
9.
Yanqing Zhao Yingli Su Wangcai Zou Gang Chen Yiqing Deng Jun Cheng Haisheng Ren Qiang Zhao 《应用聚合物科学杂志》2021,138(38):50971
In order to prepare waterborne polyurethane with excellent water resistance and thermodynamic properties, a series of side chain fluorinated waterborne polyurethane-urea (FWPU-UA) was synthesized with polytetramethylene ether glycol, N-(2-methyl-1,3-propanediol-2′-)-perfluoro-1-butanesulfonyl amine (NPBA), isophorone diisocyanate, and isophoronediamine. With the increase of NPBA content, the weight loss temperature, glass transition temperature, and tensile strength of FWPU-UA were all improved. Gaussian fitting analysis of infrared data and density functional theory simulation proved that the introduction of fluorine side chains increased the interaction of hydrogen bonding in the FWPU-UA. X-ray photoelectron spectroscopy analysis indicated that the aggregation of fluorine atoms on the surface of film were caused by the migration and enrichment of fluorine side chains. Furthermore, the water resistance of polyurethane-urea film could be significantly improved by adding a small amount of NPBA, and the seven-day water absorption rate of polyurethane-urea film was reduced from 30.13% to 12.55%. 相似文献
10.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献