全文获取类型
收费全文 | 61199篇 |
免费 | 1835篇 |
国内免费 | 314篇 |
专业分类
电工技术 | 842篇 |
综合类 | 661篇 |
化学工业 | 8599篇 |
金属工艺 | 1159篇 |
机械仪表 | 1479篇 |
建筑科学 | 1186篇 |
矿业工程 | 436篇 |
能源动力 | 1751篇 |
轻工业 | 3175篇 |
水利工程 | 734篇 |
石油天然气 | 132篇 |
武器工业 | 5篇 |
无线电 | 4147篇 |
一般工业技术 | 7596篇 |
冶金工业 | 22814篇 |
原子能技术 | 355篇 |
自动化技术 | 8277篇 |
出版年
2024年 | 114篇 |
2023年 | 601篇 |
2022年 | 1057篇 |
2021年 | 1234篇 |
2020年 | 916篇 |
2019年 | 979篇 |
2018年 | 1651篇 |
2017年 | 1613篇 |
2016年 | 1948篇 |
2015年 | 1368篇 |
2014年 | 1246篇 |
2013年 | 1894篇 |
2012年 | 3002篇 |
2011年 | 3467篇 |
2010年 | 1506篇 |
2009年 | 1544篇 |
2008年 | 1294篇 |
2007年 | 1181篇 |
2006年 | 1021篇 |
2005年 | 3673篇 |
2004年 | 2811篇 |
2003年 | 2274篇 |
2002年 | 1022篇 |
2001年 | 904篇 |
2000年 | 440篇 |
1999年 | 780篇 |
1998年 | 6428篇 |
1997年 | 4035篇 |
1996年 | 2715篇 |
1995年 | 1612篇 |
1994年 | 1221篇 |
1993年 | 1245篇 |
1992年 | 344篇 |
1991年 | 431篇 |
1990年 | 400篇 |
1989年 | 368篇 |
1988年 | 369篇 |
1987年 | 307篇 |
1986年 | 271篇 |
1985年 | 251篇 |
1984年 | 141篇 |
1983年 | 151篇 |
1982年 | 187篇 |
1981年 | 245篇 |
1980年 | 238篇 |
1979年 | 90篇 |
1978年 | 124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 31 毫秒
51.
A flower‐shaped ultra‐wideband fractal antenna is presented. It comprises a fourth iterative flower‐shaped radiator, asymmetrical stub‐loaded feeding line, and coplanar quarter elliptical ground planes. A wide operating band of 12.12 GHz (4.58‐16.7 GHz) for S 11 ≤ ? 10 dB is achieved along with an overall antenna footprint of 15.7 × 11.4 mm2. In addition, other desirable characteristics, that is, omnidirectional radiation patterns, peak gain upto 5 dB, and fidelity factor more than 75% are achieved. A good agreement exists between the simulation and measured results. The obtained results illustrate that this antenna has wide operating range and compact dimensions than available structures. 相似文献
52.
Yang Chao-Tung Chen Shuo-Tsung Liu Jung-Chun Chan Yu-Wei Chen Chien-Chih Verma Vinod Kumar 《The Journal of supercomputing》2019,75(8):4408-4429
The Journal of Supercomputing - In the last decade, cloud computing has brought enormous changes to people’s lives. Cloud computing gives a client-driven computational model. In this case,... 相似文献
53.
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
54.
Neural Computing and Applications - We propose “Deep Autoencoders for Feature Learning in Recommender Systems,” a novel discriminative model based on the incorporation of features from... 相似文献
55.
Chandel Narendra Singh Chakraborty Subir Kumar Rajwade Yogesh Anand Dubey Kumkum Tiwari Mukesh K. Jat Dilip 《Neural computing & applications》2021,33(10):5353-5367
Neural Computing and Applications - The identification of water stress is a major challenge for timely and effective irrigation to ensure global food security and sustainable agriculture. Several... 相似文献
56.
Patel Sapna Kumar Dushyant Chaurasiya Nitesh Kumar Tripathi Shweta 《Semiconductors》2019,53(13):1797-1803
Semiconductors - In the present paper, analytical modeling of surface potential and drain current for hetero-dielectric double gate tunnel FET (HDG-TFET) has been done. The two dimensional (2D)... 相似文献
57.
Ugur Gezer Ebru E. Y?rüker Metin Keskin Cemil Burak Kulle Yoganiranjana Dharuman Stefan Holdenrieder 《International journal of molecular sciences》2015,16(12):29654-29662
Circulating nucleic acids (CNAs) are under investigation as a liquid biopsy in cancer as potential non-invasive biomarkers, as stable structure in circulation nucleosomes could be valuable sources for detection of cancer-specific alterations in histone modifications. Our interest is in histone methylation marks with a focus on colorectal cancer, one of the leading cancers respective the incidence and mortality. Our previous work included the analysis of trimethylations of lysine 9 on histone 3 (H3K9me3) and of lysine 20 on histone 4 (H4K20me3) by chromatin immuno- precipitation-related PCR in circulating nucleosomes. Here we asked whether global immunologic measurement of histone marks in circulation could be a suitable approach to show their potential as biomarkers. In addition to H3K9me3 and H4K20me3 we also measured H3K27me3 in plasma samples from CRC patients (n = 63) and cancer free individuals (n = 40) by ELISA-based methylation assays. Our results show that of three marks, the amounts of H3K27me3 (p = 0.04) and H4K20me3 (p < 0.001) were significantly lower in CRC patients than in healthy controls. For H3K9me3 similar amounts were measured in both groups. Areas under the curve (AUC) in receiver operating characteristic (ROC) curves indicating the power of CRC detection were 0.620 for H3K27me3, 0.715 for H4K20me3 and 0.769 for the combination of both markers. In conclusion, findings of this preliminary study reveal the potential of blood-based detection of CRC by quantification of histone methylation marks and the additive effect of the marker combination. 相似文献
58.
59.
60.
Silicon - In this paper, we propose and develop an analytical model of a Triple material double gate Tunnel Field Effect Transistor (TM-DG TFET) with hetero-dielectric gate oxide stack comprising... 相似文献