全文获取类型
收费全文 | 405255篇 |
免费 | 5661篇 |
国内免费 | 1350篇 |
专业分类
电工技术 | 7596篇 |
综合类 | 311篇 |
化学工业 | 60050篇 |
金属工艺 | 16546篇 |
机械仪表 | 13569篇 |
建筑科学 | 8418篇 |
矿业工程 | 2170篇 |
能源动力 | 11661篇 |
轻工业 | 29054篇 |
水利工程 | 4274篇 |
石油天然气 | 7920篇 |
武器工业 | 17篇 |
无线电 | 49362篇 |
一般工业技术 | 83529篇 |
冶金工业 | 75001篇 |
原子能技术 | 9189篇 |
自动化技术 | 33599篇 |
出版年
2021年 | 3991篇 |
2020年 | 3049篇 |
2019年 | 3928篇 |
2018年 | 6681篇 |
2017年 | 6665篇 |
2016年 | 7135篇 |
2015年 | 4490篇 |
2014年 | 7360篇 |
2013年 | 20404篇 |
2012年 | 11603篇 |
2011年 | 15394篇 |
2010年 | 12275篇 |
2009年 | 13866篇 |
2008年 | 14161篇 |
2007年 | 13899篇 |
2006年 | 12473篇 |
2005年 | 11143篇 |
2004年 | 10548篇 |
2003年 | 10454篇 |
2002年 | 9858篇 |
2001年 | 9744篇 |
2000年 | 9158篇 |
1999年 | 9533篇 |
1998年 | 24337篇 |
1997年 | 16716篇 |
1996年 | 12802篇 |
1995年 | 9525篇 |
1994年 | 8371篇 |
1993年 | 8384篇 |
1992年 | 6061篇 |
1991年 | 5697篇 |
1990年 | 5691篇 |
1989年 | 5321篇 |
1988年 | 5049篇 |
1987年 | 4427篇 |
1986年 | 4307篇 |
1985年 | 4829篇 |
1984年 | 4446篇 |
1983年 | 4023篇 |
1982年 | 3670篇 |
1981年 | 3748篇 |
1980年 | 3446篇 |
1979年 | 3341篇 |
1978年 | 3338篇 |
1977年 | 3757篇 |
1976年 | 4853篇 |
1975年 | 2858篇 |
1974年 | 2668篇 |
1973年 | 2737篇 |
1972年 | 2286篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Dr. Tomasz Ratajczyk Prof. Dr. Gerd Buntkowsky Dr. Torsten Gutmann Dr. Bartłomiej Fedorczyk Dr. Adam Mames Dr. Mariusz Pietrzak Zuzanna Puzio Piotr Grzegorz Szkudlarek 《Chembiochem : a European journal of chemical biology》2021,22(5):855-860
The biorelevant PyFALGEA oligopeptide ligand, which is selective towards the epidermal growth factor receptor (EGFR), has been successfully employed as a substrate in magnetic resonance signal amplification by reversible exchange (SABRE) experiments. It is demonstrated that PyFALGEA and the iridium catalyst IMes form a PyFALGEA:IMes molecular complex. The interaction between PyFALGEA:IMes and H2 results in a ternary SABRE complex. Selective 1D EXSY experiments reveal that this complex is labile, which is an essential condition for successful hyperpolarization by SABRE. Polarization transfer from parahydrogen to PyFALGEA is observed leading to significant enhancement of the 1H NMR signals of PyFALGEA. Different iridium catalysts and peptides are inspected to discuss the influence of their molecular structures on the efficiency of hyperpolarization. It is observed that PyFALGEA oligopeptide hyperpolarization is more efficient when an iridium catalyst with a sterically less demanding NHC ligand system such as IMesBn is employed. Experiments with shorter analogues of PyFALGEA, that is, PyLGEA and PyEA, show that the bulky phenylalanine from the PyFALGEA oligopeptide causes steric hindrance in the SABRE complex, which hampers hyperpolarization with IMes. Finally, a single-scan 1H NMR SABRE experiment of PyFALGEA with IMesBn revealed a unique pattern of NMR lines in the hydride region, which can be treated as a fingerprint of this important oligopeptide. 相似文献
92.
93.
Angelico Mendy Nervana Metwali Sarah S. Perry Elizabeth A. Chrischilles Kai Wang Peter S. Thorne 《Indoor air》2020,30(1):88-97
Endotoxin exacerbates asthma. We designed the Louisa Environmental Intervention Project (LEIP) and assessed its effectiveness in reducing household endotoxin and improving asthma symptoms in rural Iowa children. Asthmatic school children (N = 104 from 89 homes) of Louisa and Keokuk counties in Iowa (aged 5-14 years) were recruited and block-randomized to receive extensive (education + professional cleaning) or educational interventions. Environmental sampling collection and respiratory survey administration were done at baseline and during three follow-up visits. Mixed-model analyses were used to assess the effect of the intervention on endotoxin levels and asthma symptoms in the main analysis and of endotoxin reduction on asthma symptoms in exploratory analysis. In the extensive intervention group, dust endotoxin load was significantly reduced in post-intervention visits. The extensive compared with the educational intervention was associated with significantly decreased dust endotoxin load in farm homes and less frequent nighttime asthma symptoms. In exploratory analysis, dust endotoxin load reduction from baseline was associated with lower total asthma symptoms score (Odds ratio: 0.52, 95% confidence interval: 0.29-0.92). In conclusion, the LEIP intervention reduced household dust endotoxin and improved asthma symptoms. However, endotoxin reductions were not sustained post-intervention by residents. 相似文献
94.
95.
96.
97.
98.
99.
100.