全文获取类型
收费全文 | 328838篇 |
免费 | 3758篇 |
国内免费 | 875篇 |
专业分类
电工技术 | 6660篇 |
综合类 | 416篇 |
化学工业 | 45889篇 |
金属工艺 | 16465篇 |
机械仪表 | 13659篇 |
建筑科学 | 7402篇 |
矿业工程 | 1802篇 |
能源动力 | 7019篇 |
轻工业 | 23927篇 |
水利工程 | 3607篇 |
石油天然气 | 5185篇 |
武器工业 | 68篇 |
无线电 | 41068篇 |
一般工业技术 | 68247篇 |
冶金工业 | 51710篇 |
原子能技术 | 6397篇 |
自动化技术 | 33950篇 |
出版年
2021年 | 2037篇 |
2019年 | 2034篇 |
2018年 | 11266篇 |
2017年 | 11897篇 |
2016年 | 8177篇 |
2015年 | 2816篇 |
2014年 | 4138篇 |
2013年 | 11335篇 |
2012年 | 8997篇 |
2011年 | 16750篇 |
2010年 | 14581篇 |
2009年 | 14329篇 |
2008年 | 14867篇 |
2007年 | 16772篇 |
2006年 | 7878篇 |
2005年 | 10545篇 |
2004年 | 8763篇 |
2003年 | 8271篇 |
2002年 | 7008篇 |
2001年 | 6533篇 |
2000年 | 6299篇 |
1999年 | 6276篇 |
1998年 | 14250篇 |
1997年 | 10272篇 |
1996年 | 8125篇 |
1995年 | 6422篇 |
1994年 | 5733篇 |
1993年 | 5605篇 |
1992年 | 4565篇 |
1991年 | 4235篇 |
1990年 | 4049篇 |
1989年 | 3780篇 |
1988年 | 3631篇 |
1987年 | 3174篇 |
1986年 | 3070篇 |
1985年 | 3613篇 |
1984年 | 3387篇 |
1983年 | 3037篇 |
1982年 | 2854篇 |
1981年 | 2955篇 |
1980年 | 2761篇 |
1979年 | 2651篇 |
1978年 | 2504篇 |
1977年 | 2950篇 |
1976年 | 3557篇 |
1975年 | 2317篇 |
1974年 | 2314篇 |
1973年 | 2320篇 |
1972年 | 1850篇 |
1971年 | 1748篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
V. A. Eremenko V. N. Karpov V. V. Timonin N. G. Barnov I. O. Shakhtorin 《Journal of Mining Science》2015,51(6):1113-1125
The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed. 相似文献
73.
Hoang V. Le Phuong T. Pham Ly T. Le Anh D. Nguyen Ngoc Quang Tran Phong D. Tran 《International Journal of Hydrogen Energy》2021,46(44):22852-22863
WO3 is a potential material candidate for construction of photoanode for solar driven water splitting. In this work, μm-thick porous WO3 photoanode is prepared by depositing a stable ink made of WO3 nanoparticles and Aristoflex velvet polymer in water using the doctor blade technique, followed by a sintering in air. The nature of WO3 nanoparticles, its loading mass on F-doped tin oxide electrode as well as sintering temperature are examined in order to optimize the photocatalytic activity of the resultant WO3 photoanode. The operation of WO3 photoanode is investigated by varying the light illumination direction and light incident intensity as well as changing the nature of the electrolyte. Dissolved tungsten in electrolyte is quantified by ICP-MS providing insights into the influences of electrolyte nature and operating conditions to the corrosion of WO3. It is proposed that the H2O2 and OH. radical generated as by-products of the photo-driven water oxidation on the photoanode surface are harmful species that accelerate the dissolution of WO3. 相似文献
74.
Krutov D. A. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(4):519-527
Power Technology and Engineering - Measures for slope protection were developed and installed. The reliability of the proposed protective structures was confirmed by calculation studies using the... 相似文献
75.
Sleptsov V. V. Kukushkin D. Yu. Kulikov S. N. Diteleva A. O. 《Russian Engineering Research》2021,41(5):416-418
Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor... 相似文献
76.
D. Kherifi H. Belhouchet S. Ramesh K.Y. Sara Lee A. Kenzour S. Djoualah M.K.G. Abbas Y.H. Wong S. Ramesh 《Ceramics International》2021,47(12):16483-16490
In this work, the sintering behaviour of fluorapatite (FAp)–silicate composites prepared by mixing variable amounts of natural quartz (2.5 wt% to 20 wt%) and FAp was studied. The composites were pressureless sintered in air at temperatures from 1000 °C to 1350 °C. The effects of temperatures on the densification, phase formation, chemical bonding and Vickers hardness of the composites were evaluated. All the samples exhibited mixed phase, comprising FAp and francolite as the major constituents along with some minor phases of cristobalite, wollastonite, dicalcium silicate and/or whitlockite dependent on the quartz content and sintering temperature. The composite containing 2.5 wt% quartz exhibited the best sintering properties. The highest bulk density of 3 g/cm3 and a Vickers hardness of >4.2 GPa were obtained for the 2.5 wt% quartz–FAp composite when sintered at 1100 °C. The addition of quartz was found to alter the microstructure of the composites, where it exhibited a rod-like morphology when sintered at 1000 °C and a regular rounded grain structure when sintered at 1350 °C. A wetted grain surface was observed for composites containing high quartz content and was believed to be associated with a transient liquid phase sintering. 相似文献
77.
V.A. Dekhtyarenko T.V. Pryadko D.G. Savvakin V.I. Bondarchuk G.S. Mogylnyy 《International Journal of Hydrogen Energy》2021,46(11):8040-8047
The influence of phase composition and microstructure of Ti42.75Zr27Mn20.25V10 alloy on its hydrogenation kinetic and phase composition of hydrogenated product was studied. It is established that the process of dissociation of hydrogen molecules begins on the surface of Laves phase crystallites. The dissolution of atomic hydrogen in the material volume leads to the formation of cracks in the intermetallic crystallites, which further appear as additional centers of dissociation of hydrogen molecules and noticeably accelerate the diffusion of hydrogen into the bulk material. It was shown that the Laves phase acts as a donor of atomic hydrogen for the BCC solid solution during hydrogenation of two-phase structure, initiating intensive hydrogenation of the BCC phase at room temperature. 相似文献
78.
Do T. Hue Rebel Skirving Tong Chen John L. Williams Cynthia D.K. Bottema Kiro Petrovski 《Journal of dairy science》2021,104(7):8164-8176
Colostrum is essential for good neonate health; however, it is not known whether different calves absorb the nutrients from colostrum equally well. In this study, the absorption of protein, IgG, and γ-glutamyl transferase was compared in newborn dairy bull calves for 1 wk after feeding colostrum from different sources. Thirty-five Holstein-Friesian bull calves were randomly allocated into 3 groups and fed colostrum within 4 h after birth. Group A calves (n = 12) were bottle fed colostrum from their own dam for 3 d. Colostrum from these group A cows was also used as foster cow colostrum for the group B calves (n = 12), such that each group A and B calf pair received identical colostrum from each milking of the respective group A dam (10% of birth weight per day). The group C calves (n = 11) were fed 1 bottle (2 L) of pooled colostrum and transition milk (referred to as pooled colostrum), as was the standard practice on the dairy farm. The pooled colostrum was collected from the other dairy cows on the farm 0 to 4 d postpartum and stored at 4°C for less than 12 h. Blood was sampled from calves before the first feeding and at 1, 2, 3, and 7 d after birth. Levels of total solids, total protein, and IgG were higher in the dam colostrum than in the pooled colostrum. At birth, there were no differences between the calf groups for any measurements, and all calves had very low IgG levels. After receiving colostrum, the glucose, plasma γ-glutamyl transferase, serum total protein, and IgG concentrations increased significantly in all calves. There were no differences in any blood measurements at any time point between the pairs of group A and group B calves that received colostrum from the same cow except for the IgG concentration 2 d after birth. However, the group A calves had a higher total serum protein level and IgG concentration than the group C calves for all the time points after the first feeding. The group B calves had a higher IgG concentration than the group C calves on d 1, 2, and 7 after birth. Compared with groups A and B, there was no difference in the proportion of calves in group C that failed to have passive immunity transferred adequately based on the IgG threshold (<10 g/L). Thus, the calves receiving identical colostrum from the same cow had the same levels of IgG, and even the pooled colostrum provided sufficient transfer of IgG as the calves were fed within 4 h after birth. 相似文献
79.