全文获取类型
收费全文 | 7277篇 |
免费 | 979篇 |
国内免费 | 1篇 |
出版年
2021年 | 67篇 |
2019年 | 67篇 |
2018年 | 66篇 |
2017年 | 63篇 |
2016年 | 111篇 |
2015年 | 180篇 |
2014年 | 165篇 |
2013年 | 246篇 |
2012年 | 298篇 |
2011年 | 262篇 |
2010年 | 158篇 |
2009年 | 180篇 |
2008年 | 267篇 |
2007年 | 277篇 |
2006年 | 254篇 |
2005年 | 253篇 |
2004年 | 246篇 |
2003年 | 229篇 |
2002年 | 210篇 |
2001年 | 217篇 |
2000年 | 235篇 |
1999年 | 205篇 |
1998年 | 98篇 |
1997年 | 110篇 |
1996年 | 111篇 |
1995年 | 102篇 |
1994年 | 104篇 |
1993年 | 87篇 |
1992年 | 199篇 |
1991年 | 204篇 |
1990年 | 165篇 |
1989年 | 162篇 |
1988年 | 165篇 |
1987年 | 153篇 |
1986年 | 158篇 |
1985年 | 163篇 |
1984年 | 136篇 |
1983年 | 110篇 |
1982年 | 116篇 |
1981年 | 65篇 |
1980年 | 80篇 |
1979年 | 118篇 |
1978年 | 102篇 |
1977年 | 85篇 |
1976年 | 92篇 |
1975年 | 77篇 |
1974年 | 87篇 |
1973年 | 94篇 |
1972年 | 71篇 |
1971年 | 68篇 |
排序方式: 共有8257条查询结果,搜索用时 15 毫秒
181.
182.
Inositol Metabolism in Plants. IV. Biosynthesis of Apiose in Lemna and Petroselinum 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The biosynthesis of apiose was investigated in cell wall polysaccharide of Lemna gibba G3 (duckweed) and in detached leaves of Petroselinum crispum (parsley). Lemna grown either in short days or in continuous light incorporated 14C from a medium containing myo-inositol-2-14C into d-apiosyl and d-xylosyl units of cell wall polysaccharides. Labeled d-apiose was characterized by paper chromatography, by formation of labeled crystalline di-O-isopropylidene d-apiose, and by gas chromatography of trimethylsilyl derivatives of apiose and of its sodium borohydride reduction product, apiitol. Periodate oxidation of labeled apiose revealed 86 to 94% of the 14C was located in formaldehyde fragments corresponding to C3′ and C4. Comparison of this result with work reported by Grisebach and Doebereiner and by Beck and Kandler supports the conclusion that myo-inositol-2-14C was converted to d-apiose labeled specifically at C4. 相似文献
183.
1. The uptake of dilute neutral hypochlorite by epithelial mucopolysaccharides has been compared with that of proteins, polysaccharides, amino acids and sugars. The uptake has been shown to be related to the protein content of the mucopolysaccharides rather than their polysaccharide content. 2. The destruction of the components of epithelial mucopolysaccharides, certain sugars and polysaccharides after oxidation with dilute neutral hypochlorite at 0-4 degrees has been studied. Very little destruction of the sugar components occurred and in epithelial mucopolysaccharides the only amino acid destroyed specifically was arginine. 3. Oxidation of bovine submaxillary-gland mucoprotein and ovalbumin caused very little destruction of hexosamine and no detectable liberation of this residue as a free reducing group, indicating that the O-seryl galactosaminide and the N-acyl-glycosylamine linkages reported to be present in these compounds were relatively stable to hypochlorite. 4. Depolymerization of epithelial mucopolysaccharides by neutral hypochlorite has been studied by using gel-filtration columns and compared with the depolymerization of polysaccharides and proteins under similar conditions. The polysaccharides examined were relatively resistant to oxidation whereas the proteins were extensively broken down. It is inferred that the extensive depolymerization of epithelial mucopolysaccharides by hypochlorite is related to their protein content rather than their polysaccharide content. 5. Fractionation of the products of oxidation of epithelial mucopolysaccharides by column procedures has revealed that the relative proportions of components in all fractions were similar to those in the original material. 6. Though this study does not provide unequivocal evidence from which the overall structure of this type of epithelial mucopolysaccharide may be deduced, the balance of probabilities now appears to favour a long polypeptide chain to which a large number of oligosaccharide side chains are attached via O-seryl and O-threonyl glycosidic linkages. The results, however, are also consistent with an alternating sequence of short polysaccharide and polypeptide chains and further evidence is necessary before this structure can be ruled out. 相似文献
184.
A Tandem Duplication That Lowers Recombination Throughout a Chromosome Arm of DROSOPHILA MELANOGASTER 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Paul A. Roberts 《Genetics》1966,54(4):969-979
185.
186.
187.
From I131-albumin studies and previously defined mathematical formulations, rates of breakdown were estimated for native plasma albumin in rabbits. These rates of catabolism per unit weight of animal were remarkably constant and were independent of variations in the steady state values of albumin concentration in the plasma. These results imply that, at least between animals, the breakdown of plasma albumin follows a kinetic process of approximately zero order. It seems plausible that the process operates similarly in individual animals, and hence that albumin is maintained at normal steady state levels in the healthy animal primarily by means of a regulated rate of synthesis. 相似文献
188.
189.
Sporulation of Mesophilic Clostridia 总被引:3,自引:3,他引:0
T. A. Roberts 《Journal of applied microbiology》1967,30(3):430-443
190.