全文获取类型
收费全文 | 343178篇 |
免费 | 8182篇 |
国内免费 | 2117篇 |
专业分类
电工技术 | 6357篇 |
技术理论 | 5篇 |
综合类 | 2037篇 |
化学工业 | 55674篇 |
金属工艺 | 12511篇 |
机械仪表 | 9474篇 |
建筑科学 | 8966篇 |
矿业工程 | 2169篇 |
能源动力 | 7444篇 |
轻工业 | 35400篇 |
水利工程 | 3828篇 |
石油天然气 | 6272篇 |
武器工业 | 256篇 |
无线电 | 32264篇 |
一般工业技术 | 58869篇 |
冶金工业 | 73432篇 |
原子能技术 | 6076篇 |
自动化技术 | 32443篇 |
出版年
2022年 | 2299篇 |
2021年 | 4066篇 |
2020年 | 2723篇 |
2019年 | 3394篇 |
2018年 | 5240篇 |
2017年 | 5395篇 |
2016年 | 6132篇 |
2015年 | 4678篇 |
2014年 | 6646篇 |
2013年 | 14774篇 |
2012年 | 12019篇 |
2011年 | 15227篇 |
2010年 | 10980篇 |
2009年 | 11520篇 |
2008年 | 11911篇 |
2007年 | 11780篇 |
2006年 | 10281篇 |
2005年 | 11644篇 |
2004年 | 10186篇 |
2003年 | 9242篇 |
2002年 | 8090篇 |
2001年 | 7906篇 |
2000年 | 6868篇 |
1999年 | 7108篇 |
1998年 | 20608篇 |
1997年 | 14456篇 |
1996年 | 10595篇 |
1995年 | 7548篇 |
1994年 | 6614篇 |
1993年 | 6543篇 |
1992年 | 4412篇 |
1991年 | 4301篇 |
1990年 | 4299篇 |
1989年 | 4239篇 |
1988年 | 4017篇 |
1987年 | 3408篇 |
1986年 | 3410篇 |
1985年 | 3769篇 |
1984年 | 3524篇 |
1983年 | 3252篇 |
1982年 | 2967篇 |
1981年 | 3216篇 |
1980年 | 2969篇 |
1979年 | 3007篇 |
1978年 | 2914篇 |
1977年 | 3590篇 |
1976年 | 5209篇 |
1975年 | 2622篇 |
1974年 | 2383篇 |
1973年 | 2426篇 |
排序方式: 共有10000条查询结果,搜索用时 436 毫秒
121.
Gabriel Rodrigues de Almeida Neto Cesar Augusto Gonçalves Beatrice Daniel Rodrigo Leiva Luiz Antonio Pessan 《International Journal of Hydrogen Energy》2021,46(46):23767-23778
This study investigates the preparation of polyetherimide (PEI) – LaNi5 composites films for hydrogen storage. Prior to the polymer addition, LaNi5 was ball-milled at different conditions (250, 350, and 450 RPM) and annealed at 500 °C for 1 h under vacuum. The composites were produced with BM-LaNi5-350 (PEI/LaNi5-350) and annealed BM-LaNi5-350 (PEI/LaNi5-350-TT). Membranes were successfully produced through solvent casting assisted by an ultrasonic bath. The particles dispersion and the film morphology did not change after hydrogenation cycles. In the H2 sorption experiments at 43 °C and 20 bar, the films stored H2 without incubation time; both samples reached a capacity of ~0.6 wt%. The H2 sorption kinetics of PEI/LaNi5-350 was comparable to that of BM-LaNi5-350, whereas PEI/LaNi5-350-TT presented significantly slower kinetics. LaNi5 oxidation was hindered by PEI, showing that it can be explored to improve metal hydrides air resistance. The results demonstrated that PEI films filled with LaNi5 are promising materials for hydrogen storage. 相似文献
122.
123.
Maria A. Ospina Monica Pizarro Thierry Tran Julien Ricci John Belalcazar Jorge L. Luna Luis F. Londoño Sandra Salazar Hernan Ceballos Dominique Dufour Luis A. Becerra Lopez-Lavalle 《International Journal of Food Science & Technology》2021,56(3):1343-1353
The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field-based collection represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all-trans-β-carotene and lutein concentrations in cassava leaves ranged from 346 to 7484 ppm dry basis (db), from 174–547 μg g−1 db and 15–181 μg g−1 db, respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g 100 g−1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes. 相似文献
124.
The phase shift characteristics reflect the state change of electromagnetic wave in plasma sheath and can be used to reveal deeply the action mechanism between electromagnetic wave and plasma sheath. In this paper, the phase shift characteristics of electromagnetic wave propagation in plasma were investigated. Firstly, the impact factors of phase shift including electron density,collision frequency and incident frequency were discussed. Then, the plasma with different electron density distribution profiles were employed to investigate the influence on the phase shift characteristics. In a real case, the plasma sheath around the hypersonic vehicle will affect and even break down the communication. Based on the hypersonic vehicle model, we studied the electromagnetic wave phase shift under different flight altitude, speed, and attack angle. The results indicate that the phase shift is inversely proportional to the flight altitude and positively proportional to the flight speed and attack angle. Our work provides a theoretical guidance for the further research of phase shift characteristics and parameters inversion in plasma. 相似文献
125.
Chinh Ngo Radhika Mehta Kanchan Aggarwal Audrey G. Fikes Dr. Ines C. Santos Dr. Sylvester M. Greer Prof. Dr. Emily L. Que 《Chembiochem : a European journal of chemical biology》2019,20(8):1003-1007
One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+-containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated. 相似文献
126.
Kozhitov L. V. Kiselev B. G. Raykova T. B. Popkova A. V. Kostishin V. G. Muratov D. G. Yakushko E. V. Kosushkin V. G. Bebenin V. G. 《Russian Microelectronics》2019,48(8):599-612
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical... 相似文献
127.
Iratxe Perez-Arnedo María J. Cantalejo Alba Martínez-Laorden Elena Gonzalez-Fandos 《International Journal of Food Science & Technology》2021,56(4):1855-1864
Microbiological contamination of chicken meat depends on the conditions under which the animals are reared, slaughtered and processed. The aim of this study was to determine the influence of farm origin and processing stages at slaughterhouse on the microbial safety and quality of chicken. Samples of chicken carcasses from three different farms were taken from a slaughterhouse. Mesophiles, Escherichia coli, coagulase positive Staphylococcci counts, presence of Listeria monocytogenes,Campylobacter and Salmonella were determined at five sampling points: after defeathering, after evisceration, after washing, after chilling and after cutting. Chilling reduced log numbers of mesophiles, coagulase positive Staphylococci and E. coli by 0.85, 1.52 and 2.2 log units, respectively. Salmonella was not detected after chilling. High prevalence of Campylobacter spp was observed at all the stages ranging between 84% and 100%. L. monocytogenes was not detected in chicken carcasses after defeathering. However, it was detected after evisceration and after washing and chilling. The most critical stage for L. monocytogenes contamination was the portioning operation, the prevalence in breast and legs being 88% and 84%, respectively. 相似文献
128.
Spiridonova E. A. Rotko V. O. Samonin V. V. Podvyaznikov M. L. 《Protection of Metals and Physical Chemistry of Surfaces》2021,57(1):45-51
Protection of Metals and Physical Chemistry of Surfaces - In this work, a universal sorbent has been obtained that works according to the mechanisms of chemisorption and adsorption by impregnating... 相似文献
129.
Water Resources Management - Public awareness of water quality concerns has increased since the Flint, MI crisis, but knowledge about water resources management remains low. Consequently,... 相似文献
130.
Microsystem Technologies - The strategy for analysis of noise generated in the analog circuit is presented here. Further, methodology for optimization of noise to improve the performance of the... 相似文献