全文获取类型
收费全文 | 136137篇 |
免费 | 9549篇 |
国内免费 | 6048篇 |
出版年
2024年 | 300篇 |
2023年 | 2155篇 |
2022年 | 3241篇 |
2021年 | 4407篇 |
2020年 | 4238篇 |
2019年 | 5380篇 |
2018年 | 4799篇 |
2017年 | 3609篇 |
2016年 | 3583篇 |
2015年 | 4476篇 |
2014年 | 8077篇 |
2013年 | 10406篇 |
2012年 | 6230篇 |
2011年 | 8260篇 |
2010年 | 6267篇 |
2009年 | 6970篇 |
2008年 | 7195篇 |
2007年 | 7290篇 |
2006年 | 6541篇 |
2005年 | 5754篇 |
2004年 | 5186篇 |
2003年 | 4262篇 |
2002年 | 3827篇 |
2001年 | 2576篇 |
2000年 | 2169篇 |
1999年 | 2182篇 |
1998年 | 2082篇 |
1997年 | 1762篇 |
1996年 | 1627篇 |
1995年 | 1504篇 |
1994年 | 1374篇 |
1993年 | 1177篇 |
1992年 | 1104篇 |
1991年 | 991篇 |
1990年 | 793篇 |
1989年 | 711篇 |
1988年 | 635篇 |
1987年 | 587篇 |
1986年 | 509篇 |
1985年 | 798篇 |
1984年 | 1065篇 |
1983年 | 806篇 |
1982年 | 898篇 |
1981年 | 704篇 |
1980年 | 657篇 |
1979年 | 542篇 |
1978年 | 431篇 |
1977年 | 364篇 |
1976年 | 349篇 |
1975年 | 284篇 |
排序方式: 共有10000条查询结果,搜索用时 1 毫秒
181.
182.
183.
For some foodstuffs, determination of the mycotoxin ochratoxin A (OTA) requires time consuming clean up by means of solid
phase extraction (SPE). Therefore a system for automated SPE was tested for cleaning up roasted coffee as a possible way of
shortening preparation time. Validation of the method in accordance to the so called “Concept '98” led to a LOD of 0.2 μg/kg
and a recovery rate of 92%. By using the described procedure with samples of roasted coffee the OTA contents varied between
the LOD and 3.4 μg/kg. This method was also used to determine ochratoxin A in liquorice roots, ginger and valerian.
Presented at the 26th Mykotoxin Workshop in Herrsching, Germany, May 17–19, 2004 相似文献
184.
185.
《Current biology : CB》2020,30(24):4826-4836.e7
186.
Origin of bombesin-like peptides in human fetal lung 总被引:2,自引:0,他引:2
Four different forms of bombesin-like immunoreactive peaks were detected in extracts of human fetal lung by the use of reversed-phase high performance liquid chromatography (HPLC). Peaks I, II, III and IV, (increasing retention time), were eluted using a 14-38% of acetonitrile gradient containing 0.1% trifluoroacetic acid (TFA). Peak II was the major material found in the extract of human fetal lung obtained at 16-20 weeks gestation. None of the four compounds contained in the eluted peaks had the same retention time as amphibian bombesin or porcine gastrin releasing peptide (GRP). On reversed-phase HPLC using two different solvent systems TFA or heptafluorobutyric acid (HFBA) as a hydrophobic counter ion, and in gel filtration chromatography, the chromatographic behavior of the main peak (peak II) was the same as that of the carboxyl terminal fragments of GRP, GRP18-27 or GRP19-27. This suggested that the peptide(s) in peak II resembled in composition the carboxy terminal 9 or 10 amino acids of porcine GRP. Following tryptic digestion the material in peak IV was converted to the more polar compound present in peak II. Two other peptide peaks were eluted close to peak II and these were presumed to be a modification of this main peak. One of the possible biosynthetic steps in the formation of bombesin-like peptides in human fetal lung could be a tryptic conversion of a less polar peptide to a more polar form (peak IV to II). 相似文献
187.
Peter J. Meloncelli 《Carbohydrate research》2010,345(16):2305-2322
The ABO histo-blood group system is one of the most clinically important antigen families. As part of our overall goal to prepare the entire set of the A, B and H type I-VI antigens for a range of biochemical investigations, we report herein the synthesis of the type I and II antigens with a 7-octen-1-yl aglycone. This linker was chosen to facilitate not only the future conjugation of the antigens to a protein or solid support but also the synthesis of the H type I and II octyl glycosides for enzyme kinetic studies. 相似文献
188.
《Bioorganic & medicinal chemistry letters》2020,30(12):127198
Monoacylglycerol lipase (MAGL) has emerged as an attractive drug target because of its important role in regulating the endocannabinoid 2-arachidonoylglycerol (2-AG) and its hydrolysis product arachidonic acid (AA) in the brain. Herein, we report the discovery of a novel series of diazetidinyl diamide compounds 6 and 10 as potent reversible MAGL inhibitors. In addition to demonstrating potent MAGL inhibitory activity in the enzyme assay, the thiazole substituted diazetidinyl diamides 6d–l and compounds 10 were also effective at increasing 2-AG levels in a brain 2-AG accumulation assay in homogenized rat brain. Furthermore, selected compounds have been shown to achieve good brain penetration after oral administration in an animal study. 相似文献
189.
190.