全文获取类型
收费全文 | 657篇 |
免费 | 46篇 |
国内免费 | 1篇 |
出版年
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 26篇 |
2015年 | 21篇 |
2014年 | 37篇 |
2013年 | 38篇 |
2012年 | 30篇 |
2011年 | 34篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 28篇 |
2007年 | 31篇 |
2006年 | 26篇 |
2005年 | 30篇 |
2004年 | 26篇 |
2003年 | 34篇 |
2002年 | 39篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1966年 | 4篇 |
排序方式: 共有704条查询结果,搜索用时 31 毫秒
651.
Acetylation of an equilibrated solution of d-erythrose in pyridine yields a mixture containing mainly 1,2,3-tri-O-acetyl-α- and -β-D-erythrofuranose. If D- erthyrose is dissolved in pyridine and acetic anhydride is added immediately afterwards, acetylated dimers of D-erythrose are formed as well as the triacetates. An investigation of the structure and stereochemistry of these compounds is presented. The dimerization and trimerization of 2,4-O-ethylidene-D-erythrose is also studied. 相似文献
652.
Leif Holmquist Gun Agrup Helena Anundi Olof Vesterberg 《Journal of biochemical and biophysical methods》1990,20(4):303-316
Allergies to laboratory animals, notably rats, have become an increasingly recognized occupational problem. Identification and isolation of the individual proteins causing allergic reactions, could form the basis for early recognition of sensitivity, diagnosis, control of degree of pollution of the environment and desensibilization treatments. Frequently, allergens originate from dried rat urine. Because earlier published methods were found unsatisfactory we have developed a new strategy for isolation of rat urinary proteins including a high performance technique for their mild concentration on hydroxyapatite. The concentrated allergens have been fractionated according to molecular size by high performace gel filtration and according to carbohydrate content by wheat germ lectin-Sepharose 6 MB affinity chromatography. The obtained fractions have been examined by denaturing and non-denaturing polyacrylamide gradient gel electrophoresis followed by sensitive staining procedures, and tested with respect to allergenicity by skin tests on allergic patients. 相似文献
653.
654.
Benzilic acid rearrangement of D-arabino-hexosulose (1) and O-β-D-glucopyranosyl-(1→4)-D-arabino-hexosulose (2) favours formation of mannonic acid and mannonic acid moieties, respectively. The results show that formation of aldonic acid end-groups via terminal aldosulose moieties is of little importance during oxygen-hydrogencarbonate treatment of (1→4)-linked polysaccharides. The major reaction of 1 in the absence of oxygen involves loss of C-1 as formic acid. The enediol intermediate gives rise to pentoses and pentuloses (degraded completely at high alkalinity), and 3-deoxypentonic acids. The yield of 3-deoxypentonic acids is decreased in the presence of oxygen, whereas that of arabinonic, erythronic, and glycolic acids is increased. The main reaction of 2 giving rise to aliphatic hydroxy acids is β-elimination of the glucose moiety, yielding a tricarbonyl intermediate (3) which, in sodium hydrogencarbonate, is decomposed mainly to 3,4-dihydroxybutanoic and glycolic acids. In sodium hydroxide, 3-deoxypentonic acids are among the major reaction products. In addition, a complex mixture of u.v.-absorbing solutes is formed, some of which are held irreversibly by anion exchangers. 相似文献
655.
656.
Jussi Tarkkanen Pentti Gröhn Erkki Heinonen Olof Alfthan Seppo Pyrhönen 《Cancer immunology, immunotherapy : CII》1981,10(4):251-255
Summary The effect of transfer factor (TF) immunotherapy on recurrent papillary bladder tumours (grade 0 papilloma and grade 1 and grade 2 carcinoma) has been studied. In a double blind study 27 patients received either TF derived from nonimmune normal donors or physiological saline. The follow-up period was 1 year. There was no difference between the two treatment groups with regard to clinical responses. Circulating immune complexes and responses to various skin test antigens were also analysed. Responses to skin test antigens and the level of circulating immune complexes did not correlate with clinical status, and TF had no effect on these parameters. 相似文献
657.
658.
One hundred and one pig abscesses of different localisation were examined. Bacteria were re-covered from all abscesses. In 6’8 abscesses a mixed aerobic and anaerobic flora was found. In 22 abscesses solely aerobes and in 11 solely anaerobes were found. Gorynebaoterium pyogenes and Fuso-bacterium necrophorum were found in 61 and 45 abscesses, respectively. Hemagglutination litres of G. pyogenes strains were higher with pig erythrocytes than with sheep erythrocytes. Three of 4 isolates of Staphylococcus aureus produced enterotoxin type A. 相似文献
659.
660.
Ovules of Dactylorhiza maculata , fixed in FPA50 and made transparent in Herr's clearing fluid, were investigated with confocal scanning laser microscopy. This new technique makes it possible to obtain thin optical serial sections in perfect alignment without damaging the material. It made possible an interpretation of the development of the embryo sac differing from that based on previous investigations with traditional technique. Using the new technique we found that the young embryo sac generally contains seven nuclei, two of which fuse, and the mature sac is 6-nucleate. The pollen tube does not penetrate any of the synergids when entering the embryo sac. Double fertilization takes place, and all nuclei are still alive at that moment. Four to six endosperm nuclei are formed, but later they degenerate and the growing embryo fills the entire embryo sac. 相似文献