全文获取类型
收费全文 | 54418篇 |
免费 | 4451篇 |
国内免费 | 4篇 |
出版年
2023年 | 253篇 |
2021年 | 468篇 |
2020年 | 384篇 |
2019年 | 383篇 |
2018年 | 977篇 |
2017年 | 1025篇 |
2016年 | 1162篇 |
2015年 | 1261篇 |
2014年 | 1406篇 |
2013年 | 2300篇 |
2012年 | 3579篇 |
2011年 | 3849篇 |
2010年 | 2036篇 |
2009年 | 1464篇 |
2008年 | 3153篇 |
2007年 | 3301篇 |
2006年 | 3022篇 |
2005年 | 2718篇 |
2004年 | 2595篇 |
2003年 | 2487篇 |
2002年 | 2442篇 |
2001年 | 1746篇 |
2000年 | 1957篇 |
1999年 | 1142篇 |
1998年 | 540篇 |
1997年 | 438篇 |
1996年 | 522篇 |
1995年 | 447篇 |
1994年 | 471篇 |
1993年 | 432篇 |
1992年 | 551篇 |
1991年 | 489篇 |
1990年 | 435篇 |
1989年 | 419篇 |
1988年 | 408篇 |
1987年 | 392篇 |
1986年 | 337篇 |
1985年 | 435篇 |
1984年 | 502篇 |
1983年 | 432篇 |
1982年 | 385篇 |
1981年 | 367篇 |
1980年 | 313篇 |
1979年 | 344篇 |
1978年 | 338篇 |
1977年 | 316篇 |
1976年 | 297篇 |
1975年 | 339篇 |
1974年 | 299篇 |
1973年 | 262篇 |
排序方式: 共有10000条查询结果,搜索用时 875 毫秒
61.
62.
In the mesenterium of rats it was found that an overacidity of the blood flowing in the area of microcirculation and caused by irrigation with acid media may be objectively represented in the clearing of venols measurable by means of video technique. The cause of this clearing process is the swelling of erythrocytes setting in at lower pH-values. According to in-vitro findings this swelling of erythrocytes will lead to an increase of the apparent viscosity of the blood fluid or blood cell suspension respectively in conformity with the increase of hematocrit connected with it. 相似文献
63.
Ildikó Vidra Kálmán Simon László Institóris Ingeborg Csöregh Mátyás Czugler 《Carbohydrate research》1982,111(1):41-57
After hydrolysis of 1,6-dibromo-1,6-dideoxygalactitol (1) and 1,2:5,6-dianhydrogalactitol (2), 11 compounds were isolated, three of them as tritylated derivatives. Their structures were established on the basis of chemical evidence and, for four compounds, by X-ray diffraction. The main product of the hydrolysis of 1 was 3,6-anhydro-1-bromo-1-deoxy-dl-galactitol; the end-products of the hydrolysis of 2 were 1,5-anhydro-dl-galactitol, 2,5-anhydro-dl-altritol, and galactitol. 相似文献
64.
65.
Summary The specificity of interaction of amino acids with triplets in the acceptor helix stem of tRNA was investigated by means of a statistical analysis of 1400 tRNA sequences. The imprint of a prototypic genetic code at position 3–5 of the acceptor helix was detected, but only for those major amino acids, glycine, alanine, aspartic acid, and valine, that are formed by spark discharges of simple gases in the laboratory. Although remnants of the code at position 3–5 are typical for tRNAs of archaebacteria, eubacteria, and chloroplasts, eukaryotes do not seem to contain this code, and mitochondria take up an intermediary position. A duplication mechanism for the transposition of the original 3–5 code toward its present position in the anticodon stern of tRNA is proposed. From this viewpoint, the mode of evolution of mRNA and functional ribosomes becomes more understandable.Offprint requests to: W. Moller 相似文献
66.
Karl-D. Entian Kai-U. Fröhlich Dieter Mecke 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,799(2):181-186
An electrophoretic method has been devised to investigate the changes in the enzymes and isoenzymes of carbohydrate metabolism, upon adding glucose to derepressed yeast cell. (i) Of the glycolytic enzymes tested, enolase II, pyruvate kinase and pyruvate decarboxylase were markedly increased. This increase was accompanied by an overall increase in glycolytic activity and was prevented by cycloheximide, an inhibitor of protein synthesis. (ii) In contrast, respiratory activity decreased after adding glucose. This decrease was clearly shown to be the result of repression of respiratory enzymes. A rapid decrease within a few minutes of adding glucose, by analogy with the so-called ‘Crabtree effect’, was not observed in yeast. (iii) The gluconeogenic enzymes, fructose-1,6-bisphosphatase and malate dehydrogenase, which are inactivated after adding glucose, showed no significant changes in electrophoretic mobilities. Hence, there was no evidence of enzyme modifications, which were postulated as initiating degradation. However, it was possible to investigate cytoplasmic and mitochondrial malate dehydrogenase isoenzymes separately. Synthesis of the mitochondrial isoenzyme was repressed, whereas only cytoplasmic malate hydrogenase was subject to glucose inactivation. 相似文献
67.
Planta - Kulturen vonAspergillus niger, in denen dem Pilz gleichzeitig gestaffelte Mengen von Kali und Phosphat geboten wurden, ergaben, daß dasMitscherlich-Baulesche Wirkungsgesetz der... 相似文献
68.
Prof. Dr. J. von Gelei 《Zoomorphology》1930,18(4):786-798
Ohne Zusammenfassung 相似文献
69.
Lars Terenius Björn Johansson 《Biochemical and biophysical research communications》2010,396(1):140-142
This mini-review outlines the opioid systems and their roles primarily as related to reward and compulsive drug/alcohol intake. The central role is taken by the mu-opioid receptor, target for opiate analgesics and also a central target in compulsive alcohol abuse, alcoholism. The mu-opioid receptor and the cognate opioid neuropeptides from proenkephalin and proopiomelancortin are members of a superfamily of opioid systems, each with unique and still to be defined roles in the central nervous system. 相似文献
70.
Barna Györffy 《Planta》1941,32(1):15-37
Zusammenfassung In der Mehrzahl der untersuchten Fälle (insgesamt über 1000 Einzelmessungen) wurden die osmotischen Werte der Tetraploiden niedriger gefunden als die der Diploiden, doch sind die Unterschiede im allgemeinen gering. Junge Pflanzen hatten immer niedrigere 4n-Werte; bei alten Pflanzen und bei Pflanzen unter extremen Kulturbedingungen waren aber vielfach die Werte der 4n höher. Es wird die Hypothese aufgestellt, daß niedrigere osmotische Werte der Tetraploiden den Normalzustand darstellen, daß aber die Polyploiden wie in anderen Eigenschaften, so auch in ihrer Osmotik variabler sind und unter dem Einfluß von Außen-bedingungen ihre osmotischen Werte stärker modifizieren.Unter physiologischen Zwangsbedingungen (Trockenkultur, Pfropfungen) wurde an den Tetraploiden eine unter den gegebenen Verhältnissen zweckmäßige Erhöhung ihrer osmotischen Werte über das Niveau der 2n beobachtet. Gegen Trockenklima erwiesen sich die untersuchten Tetraploiden im Vergleich mit den Diploiden resistenter.Irgendwelche artspezifischen Eigentümlichkeiten konnten im Rahmen der untersuchten Pflanzen nicht festgestellt werden.Mit 6 Textabbildungen. 相似文献