全文获取类型
收费全文 | 814篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 21篇 |
化学工业 | 149篇 |
金属工艺 | 30篇 |
机械仪表 | 11篇 |
建筑科学 | 20篇 |
能源动力 | 28篇 |
轻工业 | 23篇 |
水利工程 | 3篇 |
无线电 | 119篇 |
一般工业技术 | 164篇 |
冶金工业 | 158篇 |
原子能技术 | 6篇 |
自动化技术 | 115篇 |
出版年
2023年 | 4篇 |
2022年 | 13篇 |
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 31篇 |
2017年 | 23篇 |
2016年 | 21篇 |
2015年 | 10篇 |
2014年 | 25篇 |
2013年 | 49篇 |
2012年 | 50篇 |
2011年 | 39篇 |
2010年 | 29篇 |
2009年 | 34篇 |
2008年 | 33篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 23篇 |
2004年 | 23篇 |
2003年 | 13篇 |
2002年 | 19篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 29篇 |
1997年 | 14篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 22篇 |
1993年 | 18篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1970年 | 2篇 |
排序方式: 共有847条查询结果,搜索用时 343 毫秒
1.
2.
Animesh Chakravorty 《Israel journal of chemistry》1985,25(2):99-105
Model complexes of nickel(III) and nickel(IV) are furnished by hexadentate and tridentate oxime-imine-amine ligands derived by the condensation of biacetyl monoxime with amines. The synthesis, characterisation, structure, redox equilibria and reactivity of these complexes are critically reviewed. Correlations and generalisations pertaining to oxidation state stability, electroprotic equilibria and reaction mechanisms are examined. The possible significance of the present complexes in the context of the nickel-containing methanogenic enzymes is noted. 相似文献
3.
Sintering and grain growth of nano-crystalline undoped ZnO has been studied in detail over a wide range of temperature and holding time. Below 800 °C, sintering of over 70% theoretical density is not observed, irrespective of particle size. At 900 °C for 6 h, the nano-crystalline sample sinters to 99% of theoretical density whereas the density for as received sample is 93% of theoretical density. However, at 1300 °C or higher, the densification is found to be much faster and after a few hours becomes independent of holding time. Grain growth studies reveal a similar feature of attaining saturation over holding time. The average saturated grain size is found to be ∼1.5 and ∼2.2 μm at 800 and 900 °C, respectively, while at 1300 °C or higher, it is in between 12 and 13 μm. 相似文献
4.
5.
C Wang ME Nicol MK Chakrabarti A Holdcroft JG Whitwam 《Canadian Metallurgical Quarterly》1993,16(6):354-357
We compared high frequency ventilation (HFV) to conventional mechanical ventilation (CMV) under normoxic and normocapnic condition in surfactant depleted rabbits with bilateral pneumothoraces. We hypothesized that lower airway pressures would be required with HFV under these conditions. We applied CMV and HFV in 8 anaesthetized rabbits with a prototype ventilator at frequencies of 30, 100, 200, and 300 cycles/min. A positive end-expiratory pressure (PEEP) just below the pressure sufficient to open the air leak from the pneumothoraces was applied at all frequencies. Airway pressures, gas exchange, heart rate, and mean arterial pressure were recorded. Peak airway pressure decreased significantly from 2.50 to 2.10 kPa when the frequency of ventilation was increased from 30 to 300 cycles/min. There were no significant changes in mean airway pressure, PaO2, arterial pH, heart rate, and mean arterial pressure when HFV was compared to CMV. In conclusion, during HFV peak airway pressures measured at the mouth were decreased. Our ability to maintain adequate gas exchange in the face of ongoing pulmonary air leaks may reflect lower alveolar pressures. 相似文献
6.
Animesh Chakrabarti Man Mohan Sharma 《Journal of the American Oil Chemists' Society》1992,69(12):1251-1253
Anhydrous esterification of myristic acid with propylene was carried out in the temperature range of 110–145°C and pressure
from 190–195 psig in the presence of Amberlyst-15 (cation exchange resin) and Filtrol-24 (acid-treated clay) as catalysts.
The product ester, isopropyl myristate finds use in cosmetic and topical medicinal preparations where good absorption through
the skin is desired. Filtrol-24 is the catalyst of choice, and the recommended operating temperature is 130°C with a pressure
of 190 psig. 相似文献
7.
8.
9.
10.
An analysis of the geometry of metal binding by carboxylic andcarboxamide groups in proteins is presented. Most of the ligandsare from aspartic and glutamic acid side chains. Water moleculesbound to carboxylate anions are known to interact with oxygenlone-pairs. However, metal ions are also found to approach thecarboxylate group along the C - O direction. More metal ionsare found to be along the syn than the anti lone-pair direction.This seems to be the result of the stability of the five-memberedring that is formed by the carboxylate anion hydrogen bondedto a ligand water molecule and the metal ion in the syn position.Ligand residues are usually from the helix, turn or regionswith no regular secondary structure. Because of the steric interactionsassociated with bringing all the ligands around a metal center,a calcium ion can bind only near the ends of a helix; a metal,like zinc, with a low coordination number, can bind anywherein the helix. Based on the analysis of the positions of watermolecules in the metal coordination sphere, the sequence ofthe EF hand (a calcium-binding structure) is discussed. 相似文献