全文获取类型
收费全文 | 62412篇 |
免费 | 1793篇 |
国内免费 | 327篇 |
专业分类
电工技术 | 867篇 |
综合类 | 662篇 |
化学工业 | 8903篇 |
金属工艺 | 1180篇 |
机械仪表 | 1516篇 |
建筑科学 | 1212篇 |
矿业工程 | 436篇 |
能源动力 | 1829篇 |
轻工业 | 3238篇 |
水利工程 | 761篇 |
石油天然气 | 139篇 |
武器工业 | 5篇 |
无线电 | 4274篇 |
一般工业技术 | 7868篇 |
冶金工业 | 22863篇 |
原子能技术 | 364篇 |
自动化技术 | 8415篇 |
出版年
2024年 | 160篇 |
2023年 | 620篇 |
2022年 | 1145篇 |
2021年 | 1291篇 |
2020年 | 958篇 |
2019年 | 1010篇 |
2018年 | 1702篇 |
2017年 | 1656篇 |
2016年 | 1977篇 |
2015年 | 1396篇 |
2014年 | 1300篇 |
2013年 | 1997篇 |
2012年 | 3056篇 |
2011年 | 3544篇 |
2010年 | 1556篇 |
2009年 | 1605篇 |
2008年 | 1357篇 |
2007年 | 1231篇 |
2006年 | 1057篇 |
2005年 | 3716篇 |
2004年 | 2842篇 |
2003年 | 2289篇 |
2002年 | 1043篇 |
2001年 | 920篇 |
2000年 | 448篇 |
1999年 | 787篇 |
1998年 | 6440篇 |
1997年 | 4045篇 |
1996年 | 2718篇 |
1995年 | 1619篇 |
1994年 | 1230篇 |
1993年 | 1246篇 |
1992年 | 350篇 |
1991年 | 431篇 |
1990年 | 402篇 |
1989年 | 369篇 |
1988年 | 369篇 |
1987年 | 309篇 |
1986年 | 271篇 |
1985年 | 252篇 |
1984年 | 142篇 |
1983年 | 151篇 |
1982年 | 187篇 |
1981年 | 247篇 |
1980年 | 238篇 |
1979年 | 92篇 |
1978年 | 125篇 |
1977年 | 634篇 |
1976年 | 1354篇 |
1975年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Klimis?S.?NtalianisEmail author Anastasios?D.?Doulamis Nikolaos?D.?Doulamis Nikos?E.?Mastorakis Athanasios?S.?Drigas 《Journal of Signal Processing Systems》2015,80(2):153-161
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation. 相似文献
3.
Klaus Reinhardt Hans Georg Breunig Aisada Uchugonova Karsten K?nig 《Journal of the Royal Society Interface》2015,12(110)
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype. 相似文献
4.
5.
6.
7.
8.
9.
Valence M. K. Ndesendo Yahya E. Choonara Leith C. R. Meyer Pradeep Kumar Lomas K. Tomar Charu Tyagi 《Drug development and industrial pharmacy》2015,41(8):1274-1287
Context and objective: The aim of this study was to develop, characterize and evaluate a mucoadhesive caplet resulting from a polymeric blend (polymeric caplet) for intravaginal anti-HIV-1 delivery.Materials and methods: Poly(lactic-co-glycolic) acid, ethylcellulose, poly(vinylalcohol), polyacrylic acid and modified polyamide 6, 10 polymers were blended and compressed to a caplet-shaped device, with and without two model drugs 3′-azido-3′-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Thermal analysis, infrared spectroscopy and microscopic analysis were carried out on the caplets employing temperature-modulated DSC (TMDSC), Fourier transform infra-red (FTIR) spectrometer and scanning electron microscope, respectively. In vitro and in vivo drug release analyses as well as the histopathological toxicity studies were carried out on the drug-loaded caplets. Furthermore, molecular mechanics (MM) simulations were carried out on the drug-loaded caplets to corroborate the experimental findings.Results and discussion: There was a big deviation between the Tg of the polymeric caplet from the Tg's of the constituent polymers indicating a strong interaction between constituent polymers. FTIR spectroscopy confirmed the presence of specific ionic and non-ionic interactions within the caplet. A controlled near zero-order drug release was obtained for AZT (20 d) and PSS (28 d). In vivo results, i.e. the drug concentration in plasma ranged between 0.012–0.332?mg/mL and 0.009–0.256?mg/mL for AZT and PSS over 1–28 d.Conclusion: The obtained results, which were corroborated by MM simulations, attested that the developed system has the potential for effective delivery of anti-HIV-agents. 相似文献
10.
From an experimental and theoretical investigation of the continuity of influent inorganic suspended solids (ISS) along the links connecting the primary settling tank (PST), fully aerobic or N removal activated sludge (AS) and anaerobic and aerobic sludge digestion unit operations, it was found that the influent wastewater (fixed) ISS concentration is conserved through primary sludge anaerobic digestion, activated sludge and aerobic digestion unit operations. However, the measured ISS flux at different stages through a series of wastewater treatment plant (WWTP) unit operations is not equal to the influent ISS flux, because the ordinary heterotrophic organisms (OHO) biomass contributes to the ISS flux by differing amounts depending on the active fraction of the VSS solids at that stage. 相似文献