全文获取类型
收费全文 | 619587篇 |
免费 | 8903篇 |
国内免费 | 2470篇 |
专业分类
电工技术 | 11198篇 |
综合类 | 847篇 |
化学工业 | 92512篇 |
金属工艺 | 22842篇 |
机械仪表 | 18071篇 |
建筑科学 | 16149篇 |
矿业工程 | 2320篇 |
能源动力 | 16066篇 |
轻工业 | 57983篇 |
水利工程 | 5748篇 |
石油天然气 | 7374篇 |
武器工业 | 56篇 |
无线电 | 77530篇 |
一般工业技术 | 118641篇 |
冶金工业 | 115800篇 |
原子能技术 | 11856篇 |
自动化技术 | 55967篇 |
出版年
2021年 | 4385篇 |
2019年 | 4086篇 |
2018年 | 6714篇 |
2017年 | 6854篇 |
2016年 | 7309篇 |
2015年 | 5387篇 |
2014年 | 9018篇 |
2013年 | 28186篇 |
2012年 | 15303篇 |
2011年 | 21764篇 |
2010年 | 16798篇 |
2009年 | 19229篇 |
2008年 | 20335篇 |
2007年 | 20701篇 |
2006年 | 18261篇 |
2005年 | 16941篇 |
2004年 | 16689篇 |
2003年 | 16253篇 |
2002年 | 15683篇 |
2001年 | 15701篇 |
2000年 | 14770篇 |
1999年 | 15484篇 |
1998年 | 36214篇 |
1997年 | 26255篇 |
1996年 | 20376篇 |
1995年 | 15901篇 |
1994年 | 14108篇 |
1993年 | 13831篇 |
1992年 | 10221篇 |
1991年 | 9819篇 |
1990年 | 9367篇 |
1989年 | 9078篇 |
1988年 | 8597篇 |
1987年 | 7509篇 |
1986年 | 7502篇 |
1985年 | 8802篇 |
1984年 | 8196篇 |
1983年 | 7278篇 |
1982年 | 6830篇 |
1981年 | 6829篇 |
1980年 | 6561篇 |
1979年 | 6324篇 |
1978年 | 6055篇 |
1977年 | 7081篇 |
1976年 | 9520篇 |
1975年 | 5146篇 |
1974年 | 4969篇 |
1973年 | 4894篇 |
1972年 | 4052篇 |
1971年 | 3544篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Kexin Jiao Laurence J. Walsh Sao Ivanovski Pingping Han 《International journal of molecular sciences》2021,22(9)
Periodontitis is a chronic complex inflammatory disease associated with a destructive host immune response to microbial dysbiosis, leading to irreversible loss of tooth-supporting tissues. Regeneration of functional periodontal soft (periodontal ligament and gingiva) and hard tissue components (cementum and alveolar bone) to replace lost tissues is the ultimate goal of periodontal treatment, but clinically predictable treatments are lacking. Similarly, the identification of biomarkers that can be used to accurately diagnose periodontitis activity is lacking. A relatively novel category of molecules found in oral tissue, circular RNAs (circRNAs) are single-stranded endogenous, long, non-coding RNA molecules, with covalently circular-closed structures without a 5’ cap and a 3’ tail via non-classic backsplicing. Emerging research indicates that circRNAs are tissue and disease-specific expressed and have crucial regulatory functions in various diseases. CircRNAs can function as microRNA or RNA binding sites or can regulate mRNA. In this review, we explore the biogenesis and function of circRNAs in the context of the emerging role of circRNAs in periodontitis pathogenesis and the differentiation of periodontal cells. CircMAP3K11, circCDK8, circCDR1as, circ_0062491, and circ_0095812 are associated with pathological periodontitis tissues. Furthermore, circRNAs are expressed in periodontal cells in a cell-specific manner. They can function as microRNA sponges and can form circRNA–miRNA–mRNA networks during osteogenic differentiation for periodontal-tissue (or dental pulp)-derived progenitor cells. 相似文献
32.
Glass and Ceramics - An analysis of the specific mechanisms of the influence of the state of the grain structure on the thermoelectric properties (electrical resistivity and total thermal... 相似文献
33.
Wireless Networks - Orthogonal frequency-division multiplexing with random multiple access (OFDRMA) is discussed for down-link communications, whereby a single base-station transmits information... 相似文献
34.
Tallison O. Abreu Roterdan F. Abreu Felipe F. do Carmo Wellington V. de Sousa Helenilson de O. Barros José E.V. de Morais João P.C. do Nascimento Marcelo A.S. da Silva Sergei Trukhanov Alex Trukhanov Larissa Panina Charanjeet Singh Antonio S.B. Sombra 《Ceramics International》2021,47(11):15424-15432
This work presents the dielectric properties of YNbO4 (YNO)–TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO2. Moreover, the addition of TiO2 results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO2 composites are interesting candidates for microwave operating devices. 相似文献
35.
Cybernetics and Systems Analysis - The authors propose a method for solving the problem of approach of controlled objects in dynamic game problems with a terminal payoff function. The method is... 相似文献
36.
Radchenko P. A. Batuev S. P. Radchenko A. V. 《Journal of Engineering Physics and Thermophysics》2022,95(1):90-96
Journal of Engineering Physics and Thermophysics - A numerical investigation has been made into the interaction of slender (5–20 calibers) steel cylinder strikers with orthotropic compost... 相似文献
37.
Rudenko A. I. Nishchik A. P. Otrokh E. A. Terekh A. M. 《Journal of Engineering Physics and Thermophysics》2022,95(1):206-212
Journal of Engineering Physics and Thermophysics - Results of investigation into the influence of a corrosion process on thermotechnical characteristics of heat pipes of low-temperature range are... 相似文献
38.
Radiochemistry - Magnetically modified waste bark of the Aegle marmelos tree was prepared by using green synthesis method and was used in a batch system for U(VI) removal from aqueous solution. The... 相似文献
39.
Bilal Alashkar Alhamwe Daniel P. Potaczek Sarah Miethe Fahd Alhamdan Lukas Hintz Arslan Magomedov Holger Garn 《International journal of molecular sciences》2021,22(9)
Extracellular vesicles (EVs) are membranous structures, which are secreted by almost every cell type analyzed so far. In addition to their importance for cell-cell communication under physiological conditions, EVs are also released during pathogenesis and mechanistically contribute to this process. Here we summarize their functional relevance in asthma, one of the most common chronic non-communicable diseases. Asthma is a complex persistent inflammatory disorder of the airways characterized by reversible airflow obstruction and, from a long-term perspective, airway remodeling. Overall, mechanistic studies summarized here indicate the importance of different subtypes of EVs and their variable cargoes in the functioning of the pathways underlying asthma, and show some interesting potential for the development of future therapeutic interventions. Association studies in turn demonstrate a good diagnostic potential of EVs in asthma. 相似文献
40.
Ib Holzmeister Jan Weichhold Jürgen Groll Hala Zreiqat Uwe Gbureck 《Journal of the American Ceramic Society》2021,104(7):3554-3561
In this study, the hydraulic reactivity and cement formation of baghdadite (Ca3ZrSi2O9) was investigated. The material was synthesized by sintering a mixture of CaCO3, SiO2, and ZrO2 and then mechanically activated using a planetary mill. This leads to a decrease in particle and crystallite size and a partial amorphization of baghdadite as shown by X-ray powder diffraction (XRD) and laser diffraction measurements. Baghdadite cements were formed by the addition of water at a powder to liquid ratio of 2.0 g/ml. Maximum compressive strengths were found to be ~2 MPa after 3-day setting for a 24-h ground material. Inductively coupled plasma mass spectrometry (ICP-MS) measurements showed an incongruent dissolution profile of set cements with a preferred dissolution of calcium and only marginal release of zirconium ions. Cement formation occurs under alkaline conditions, whereas the unground raw powder leads to a pH of 11.9 during setting, while prolonged grinding increased pH values to approximately 12.3. 相似文献