全文获取类型
收费全文 | 309499篇 |
免费 | 3997篇 |
国内免费 | 713篇 |
专业分类
电工技术 | 6194篇 |
综合类 | 560篇 |
化学工业 | 46742篇 |
金属工艺 | 10324篇 |
机械仪表 | 8820篇 |
建筑科学 | 7898篇 |
矿业工程 | 862篇 |
能源动力 | 8569篇 |
轻工业 | 31085篇 |
水利工程 | 2532篇 |
石油天然气 | 3670篇 |
武器工业 | 8篇 |
无线电 | 39697篇 |
一般工业技术 | 58448篇 |
冶金工业 | 56637篇 |
原子能技术 | 5459篇 |
自动化技术 | 26704篇 |
出版年
2021年 | 2275篇 |
2019年 | 2142篇 |
2018年 | 3610篇 |
2017年 | 3450篇 |
2016年 | 3540篇 |
2015年 | 2540篇 |
2014年 | 4439篇 |
2013年 | 14275篇 |
2012年 | 7363篇 |
2011年 | 10115篇 |
2010年 | 7899篇 |
2009年 | 9132篇 |
2008年 | 9600篇 |
2007年 | 9578篇 |
2006年 | 8505篇 |
2005年 | 7888篇 |
2004年 | 7761篇 |
2003年 | 7498篇 |
2002年 | 7333篇 |
2001年 | 7543篇 |
2000年 | 7206篇 |
1999年 | 7545篇 |
1998年 | 17655篇 |
1997年 | 12832篇 |
1996年 | 10101篇 |
1995年 | 7872篇 |
1994年 | 7203篇 |
1993年 | 6903篇 |
1992年 | 5286篇 |
1991年 | 5066篇 |
1990年 | 4933篇 |
1989年 | 4781篇 |
1988年 | 4673篇 |
1987年 | 3886篇 |
1986年 | 4007篇 |
1985年 | 4717篇 |
1984年 | 4275篇 |
1983年 | 4021篇 |
1982年 | 3601篇 |
1981年 | 3761篇 |
1980年 | 3456篇 |
1979年 | 3418篇 |
1978年 | 3225篇 |
1977年 | 3814篇 |
1976年 | 4847篇 |
1975年 | 2780篇 |
1974年 | 2660篇 |
1973年 | 2675篇 |
1972年 | 2215篇 |
1971年 | 1963篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
54.
55.
56.
Geetha R. Madhusudhan V. Padmavathy T. Lallithasree A. 《Wireless Personal Communications》2019,108(3):1957-1976
Wireless Personal Communications - The majority of security systems for wireless sensor networks are based on symmetric encryption. The main open issue for these approaches concerns the... 相似文献
57.
Rachana R. Borkute Sren Woelke Gang Pei Anca Dorhoi 《International journal of molecular sciences》2021,22(9)
Neutrophils readily infiltrate infection foci, phagocytose and usually destroy microbes. In tuberculosis (TB), a chronic pulmonary infection caused by Mycobacterium tuberculosis (Mtb), neutrophils harbor bacilli, are abundant in tissue lesions, and their abundances in blood correlate with poor disease outcomes in patients. The biology of these innate immune cells in TB is complex. Neutrophils have been assigned host-beneficial as well as deleterious roles. The short lifespan of neutrophils purified from blood poses challenges to cell biology studies, leaving intracellular biological processes and the precise consequences of Mtb–neutrophil interactions ill-defined. The phenotypic heterogeneity of neutrophils, and their propensity to engage in cellular cross-talk and to exert various functions during homeostasis and disease, have recently been reported, and such observations are newly emerging in TB. Here, we review the interactions of neutrophils with Mtb, including subcellular events and cell fate upon infection, and summarize the cross-talks between neutrophils and lung-residing and -recruited cells. We highlight the roles of neutrophils in TB pathophysiology, discussing recent findings from distinct models of pulmonary TB, and emphasize technical advances that could facilitate the discovery of novel neutrophil-related disease mechanisms and enrich our knowledge of TB pathogenesis. 相似文献
58.
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
59.
60.