全文获取类型
收费全文 | 322689篇 |
免费 | 3327篇 |
国内免费 | 916篇 |
专业分类
电工技术 | 6432篇 |
综合类 | 274篇 |
化学工业 | 44964篇 |
金属工艺 | 15797篇 |
机械仪表 | 12954篇 |
建筑科学 | 7378篇 |
矿业工程 | 1610篇 |
能源动力 | 7826篇 |
轻工业 | 22169篇 |
水利工程 | 3221篇 |
石油天然气 | 4602篇 |
武器工业 | 15篇 |
无线电 | 40777篇 |
一般工业技术 | 68106篇 |
冶金工业 | 53915篇 |
原子能技术 | 6084篇 |
自动化技术 | 30808篇 |
出版年
2021年 | 2166篇 |
2020年 | 1562篇 |
2019年 | 1915篇 |
2018年 | 11290篇 |
2017年 | 11908篇 |
2016年 | 7926篇 |
2015年 | 2723篇 |
2014年 | 4040篇 |
2013年 | 11521篇 |
2012年 | 8738篇 |
2011年 | 16566篇 |
2010年 | 14513篇 |
2009年 | 14442篇 |
2008年 | 14606篇 |
2007年 | 16554篇 |
2006年 | 7428篇 |
2005年 | 10017篇 |
2004年 | 8188篇 |
2003年 | 8080篇 |
2002年 | 6640篇 |
2001年 | 6573篇 |
2000年 | 6101篇 |
1999年 | 6406篇 |
1998年 | 16485篇 |
1997年 | 11410篇 |
1996年 | 8807篇 |
1995年 | 6615篇 |
1994年 | 5930篇 |
1993年 | 5869篇 |
1992年 | 4145篇 |
1991年 | 4042篇 |
1990年 | 3857篇 |
1989年 | 3648篇 |
1988年 | 3566篇 |
1987年 | 3017篇 |
1986年 | 2941篇 |
1985年 | 3206篇 |
1984年 | 2926篇 |
1983年 | 2828篇 |
1982年 | 2636篇 |
1981年 | 2542篇 |
1980年 | 2461篇 |
1979年 | 2305篇 |
1978年 | 2107篇 |
1977年 | 2604篇 |
1976年 | 3562篇 |
1975年 | 1764篇 |
1974年 | 1729篇 |
1973年 | 1665篇 |
1972年 | 1465篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
62.
63.
64.
65.
66.
67.
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
68.
69.
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
70.
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