全文获取类型
收费全文 | 9319篇 |
免费 | 514篇 |
国内免费 | 63篇 |
专业分类
电工技术 | 172篇 |
综合类 | 29篇 |
化学工业 | 2288篇 |
金属工艺 | 168篇 |
机械仪表 | 284篇 |
建筑科学 | 359篇 |
矿业工程 | 7篇 |
能源动力 | 584篇 |
轻工业 | 903篇 |
水利工程 | 111篇 |
石油天然气 | 151篇 |
无线电 | 950篇 |
一般工业技术 | 1632篇 |
冶金工业 | 446篇 |
原子能技术 | 100篇 |
自动化技术 | 1712篇 |
出版年
2024年 | 24篇 |
2023年 | 183篇 |
2022年 | 365篇 |
2021年 | 524篇 |
2020年 | 378篇 |
2019年 | 419篇 |
2018年 | 534篇 |
2017年 | 463篇 |
2016年 | 484篇 |
2015年 | 326篇 |
2014年 | 463篇 |
2013年 | 859篇 |
2012年 | 482篇 |
2011年 | 676篇 |
2010年 | 462篇 |
2009年 | 417篇 |
2008年 | 372篇 |
2007年 | 276篇 |
2006年 | 269篇 |
2005年 | 180篇 |
2004年 | 161篇 |
2003年 | 144篇 |
2002年 | 118篇 |
2001年 | 96篇 |
2000年 | 96篇 |
1999年 | 67篇 |
1998年 | 107篇 |
1997年 | 52篇 |
1996年 | 71篇 |
1995年 | 56篇 |
1994年 | 51篇 |
1993年 | 61篇 |
1992年 | 58篇 |
1991年 | 45篇 |
1990年 | 41篇 |
1989年 | 34篇 |
1988年 | 48篇 |
1987年 | 52篇 |
1986年 | 34篇 |
1985年 | 31篇 |
1984年 | 40篇 |
1983年 | 36篇 |
1982年 | 30篇 |
1981年 | 22篇 |
1980年 | 22篇 |
1979年 | 28篇 |
1978年 | 26篇 |
1977年 | 18篇 |
1976年 | 25篇 |
1975年 | 23篇 |
排序方式: 共有9896条查询结果,搜索用时 567 毫秒
1.
Fatemeh Norouzi Jobie Mojtaba Ranjbar Akbar Hajizadeh Moghaddam Mahmoud Kiani 《Advanced Powder Technology》2021,32(6):2043-2052
For the first time in this study, Zinc oxide nanoparticles were biosynthesized by the eco-friendly and cost-effective procedure using Amygdalus scoparia stem bark extract then used as antibacterial, antifungal, anticancer, and anti-diabetic agents. The characterization techniques confirmed the biosynthesis, crystalline nature, structure, size, elemental composition of ZnO NPs and bioactive compounds that exist in A. scoparia extract accounting for Zn2+ ion reduction, capping and stabilization of ZnO NPs. The ZnO NPs displayed remarkable inhibitory activity against E. coli, E. aerigenes, S. aureus, P. oryzae, F. thapsinum, and F. semitectum compared to antibiotic standards. The ZnO NPs showed significant inhibitory effects on cancer cell lines, while it had no toxic effect on Vero normal cell line. The ZnO NPs (30 mg/kg)-treated diabetic rats showed significantly higher levels of insulin and lower AST, ALT and blood glucose compared with the STZ induced diabetic group and other treated groups (P < 0.05). The ZnO NPs- and extract-treated rats showed significantly higher levels of IR, GluT2, and GCK expression and lower TNFα expression compared with the STZ induced diabetic rats. Our findings showed that ZnO NPs represented an outstanding performance for biological applications. 相似文献
2.
Zaidatul Akmal Othman Zaida Zakaria Joseph Bagi Suleiman Victor Udo Nna Aminah Che Romli Wan Syaheedah Wan Ghazali Mahaneem Mohamed 《International journal of molecular sciences》2021,22(8)
Obesity and hyperlipidemia are major risk factors for developing vascular diseases. Bee bread (BB) has been reported to exhibit some biological actions, including anti-obesity and anti-hyperlipidemic. This study aims to investigate whether bee bread can ameliorate vascular inflammation and impaired vasorelaxation activity through eNOS/NO/cGMP pathway in obese rats. Forty male Sprague-Dawley rats were randomly divided into four groups (n = 10/group), namely: control (normal group), obese rats (OB group), obese rats treated with bee bread (0.5 g/kg/day, OB/BB group) and obese rats treated with orlistat (10 mg/kg/day, OB/OR group). The latter three groups were given a high-fat diet (HFD) for 6 weeks to induced obesity before being administered with their respective treatments for another 6 weeks. After 12 weeks of the total experimental period, rats in the OB group demonstrated significantly higher Lee obesity index, lipid profile (total cholesterol, triglyceride, low-density lipoprotein), aortic proinflammatory markers (tumor necrosis factor-α, nuclear factor-κβ), aortic structural damage and impairment in vasorelaxation response to acetylcholine (ACh). Bee bread significantly ameliorated the obesity-induced vascular damage manifested by improvements in the lipid profile, aortic inflammatory markers, and the impaired vasorelaxation activity by significantly enhancing nitric oxide release, promoting endothelial nitric oxide synthase (eNOS) and cyclic guanosine monophosphate (cGMP) immunoexpression. These findings suggest that the administration of bee bread ameliorates the impaired vasorelaxation response to ACh by improving eNOS/NO/cGMP-signaling pathway in obese rats, suggesting its vascular therapeutic role. 相似文献
3.
Heiba Zein K. Mohamed Mohamed Bakr Farag Noura M. Badawi Ali 《Journal of Materials Science: Materials in Electronics》2022,33(13):10388-10398
Journal of Materials Science: Materials in Electronics - Nano Mn0.95M0.05S (M ≡ Cu, Mg) samples were produced using molten salt solid state reaction method. Rietveld analysis of X-ray... 相似文献
4.
5.
6.
Mahmoud Elsisi 《国际智能系统杂志》2020,35(11):1857-1878
The controller design for the robotic manipulator faces different challenges such as the system's nonlinearities and the uncertainties of the parameters. Furthermore, the tracking of different linear and nonlinear trajectories represents a vital role by the manipulator. This paper suggests an optimal design for the nonlinear model predictive control (NLMPC) based on a new improved intelligent technique and it is named modified multitracker optimization algorithm (MMTOA). The proposed modification of the MTOA is carried out based on opposition-based learning (OBL) and quasi OBL approaches. This modification improves the exploration behavior of the MTOA to prevent it from becoming trapped in a local optimum. The proposed method is applied on the robotic manipulator to track different linear and nonlinear trajectories. The NLMPC parameters are tuned by the MMTOA rather than the trial and error method of the designer. The proposed NLMPC based on MMTOA is compared with the original MTOA, genetic algorithm, and cuckoo search algorithm in literature. The superiority and effectiveness of the proposed controller are confirmed to track different linear and nonlinear trajectories. Furthermore, the robustness of the proposed method is emphasized against the uncertainties of the parameters. 相似文献
7.
Yasoub Eghbali Mahmoud Ferdosizade Naeiny 《International Journal of Communication Systems》2020,33(14)
In this paper, an off‐grid direction of arrival (DoA) estimation method is proposed for wideband signals. This method is based on the sparse representation (SR) of the array covariance matrix. Similar to the time domain DoA estimation methods, the correlation function of the sources was assumed to be the same and known. A new measurement vector is obtained using the lower‐left triangular elements of the covariance matrix. The DoAs are estimated by quantizing the entire range of continuous angle space into discrete grid points. However, the exact DoAs may be located between two grid points; therefore, this estimation has errors. The accuracy of DoA estimation is improved by the minimization of the difference between the new measurement vector and its estimated values. Simulation results revealed that the proposed method can enhance the DoA estimation accuracy of wideband signals. 相似文献
8.
Efficacy of Crude and Purified Chitinases (SsChi50) Extracted from Offal Red Scorpion Fish in Biological Control of Chickpea Weevil (Callosobruchus maculatus L.) 下载免费PDF全文
9.
10.