全文获取类型
收费全文 | 78497篇 |
免费 | 5219篇 |
国内免费 | 9篇 |
出版年
2023年 | 513篇 |
2022年 | 491篇 |
2021年 | 1399篇 |
2020年 | 1111篇 |
2019年 | 1294篇 |
2018年 | 2331篇 |
2017年 | 2145篇 |
2016年 | 2865篇 |
2015年 | 3785篇 |
2014年 | 3913篇 |
2013年 | 5179篇 |
2012年 | 6150篇 |
2011年 | 5636篇 |
2010年 | 3597篇 |
2009年 | 2937篇 |
2008年 | 4236篇 |
2007年 | 3985篇 |
2006年 | 3778篇 |
2005年 | 3270篇 |
2004年 | 3168篇 |
2003年 | 2838篇 |
2002年 | 2591篇 |
2001年 | 1738篇 |
2000年 | 1657篇 |
1999年 | 1329篇 |
1998年 | 690篇 |
1997年 | 507篇 |
1996年 | 499篇 |
1995年 | 458篇 |
1994年 | 366篇 |
1993年 | 345篇 |
1992年 | 679篇 |
1991年 | 601篇 |
1990年 | 533篇 |
1989年 | 538篇 |
1988年 | 500篇 |
1987年 | 461篇 |
1986年 | 425篇 |
1985年 | 415篇 |
1984年 | 431篇 |
1983年 | 288篇 |
1982年 | 276篇 |
1981年 | 216篇 |
1980年 | 224篇 |
1979年 | 270篇 |
1978年 | 249篇 |
1975年 | 228篇 |
1974年 | 255篇 |
1973年 | 256篇 |
1972年 | 215篇 |
排序方式: 共有10000条查询结果,搜索用时 856 毫秒
1.
We perform first principles total energy calculations to investigate the atomic structures of the adsorption of phenol (C6H5OH) on hexagonal boron nitride (BN) sheets. Calculations are done within the density functional theory as implemented in the
DMOL code. Electron-ion interactions are modeled according to the local-spin-density-approximation (LSDA) method with the
Perdew-Wang parametrization. Our studies take into account the hexagonal h-BN sheets and the modified by defects d-BN sheets.
The d-BN sheets are composed of one hexagon, three pentagons and three heptagons. Five different atomic structures are investigated:
parallel to the sheet, perpendicular to the sheet at the B site, perpendicular to the sheet at the N site, perpendicular to
the central hexagon and perpendicular to the B-N bond (bridge site). To determine the structural stability we apply the criteria
of minimum energy and vibration frequency. After the structural relaxation phenol molecules adsorb on both h-BN and d-BN sheets.
Results of the binding energies indicate that phenol is chemisorbed. The polarity of the system increases as a consequence
of the defects presence which induces transformation from an ionic to covalent bonding. The elastic properties on the BN structure
present similar behavior to those reported in the literature for graphene. 相似文献
2.
3.
4.
5.
6.
Sebastián Moran Miguel Vizoso Anna Martinez-Cardús Antonio Gomez Xavier Matías-Guiu Sebastián M Chiavenna Andrés G Fernandez Manel Esteller 《Epigenetics》2014,9(6):829-833
A formalin-fixed paraffin-embedded (FFPE) sample usually yields highly degraded DNA, which limits the use of techniques requiring high-quality DNA, such as Infinium Methylation microarrays. To overcome this restriction, we have applied an FFPE restoration procedure consisting of DNA repair and ligation processes in a set of paired fresh-frozen (FF) and FFPE samples. We validated the FFPE results in comparison with matched FF samples, enabling us to use FFPE samples on the Infinium HumanMethylation450 Methylation array. 相似文献
7.
8.
M del Mar Medina-Puerta A Garrido-Pertierra 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,83(1):215-220
The enzyme 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP+ oxidoreductase, decarboxylating EC 1.1.1.44) from bass liver has been purified to over 95% of homogeneity by gel filtration, affinity and ion exchange chromatographies. The apparent molecular weight was estimated by gel filtration chromatography to about 100,000. Analysis of the enzyme on sodium dodecyl sulphate polyacrylamide gel electrophoresis showed to be a dimeric protein. The effect of pH and kinetic properties were studied. 相似文献
9.
"Pertussis toxin induces tachycardia and impairs the increase in blood pressure produced by alpha 2-adrenergic agonists" 总被引:4,自引:0,他引:4
Administration of purified pertussis toxin to rats induced persistent tachycardia, (observed in conscious rats but not after pithing); as little as 0.05 microgram/100 g produced a significant effect. Pertussis toxin-treatment did not affected the pressor response produced in the pithed rats by the alpha 2-adrenergic agonist methoxamine but markedly diminished the pressor effect of the alpha 2-adrenergic agonists clonidine and azepexole. A role of adenylate cyclase inhibition in the action of postsynaptic vascular alpha 2-adrenergic receptors is suggested. 相似文献
10.