全文获取类型
收费全文 | 54435篇 |
免费 | 3393篇 |
国内免费 | 7篇 |
出版年
2023年 | 345篇 |
2022年 | 416篇 |
2021年 | 909篇 |
2020年 | 728篇 |
2019年 | 776篇 |
2018年 | 1673篇 |
2017年 | 1415篇 |
2016年 | 1977篇 |
2015年 | 2620篇 |
2014年 | 2715篇 |
2013年 | 3559篇 |
2012年 | 4028篇 |
2011年 | 3742篇 |
2010年 | 2375篇 |
2009年 | 1842篇 |
2008年 | 2787篇 |
2007年 | 2754篇 |
2006年 | 2675篇 |
2005年 | 2185篇 |
2004年 | 2146篇 |
2003年 | 1898篇 |
2002年 | 1778篇 |
2001年 | 1302篇 |
2000年 | 1249篇 |
1999年 | 972篇 |
1998年 | 411篇 |
1997年 | 270篇 |
1996年 | 282篇 |
1995年 | 291篇 |
1994年 | 225篇 |
1993年 | 195篇 |
1992年 | 564篇 |
1991年 | 495篇 |
1990年 | 460篇 |
1989年 | 438篇 |
1988年 | 396篇 |
1987年 | 381篇 |
1986年 | 353篇 |
1985年 | 337篇 |
1984年 | 276篇 |
1983年 | 247篇 |
1982年 | 196篇 |
1979年 | 298篇 |
1978年 | 188篇 |
1975年 | 187篇 |
1974年 | 210篇 |
1973年 | 194篇 |
1972年 | 183篇 |
1970年 | 178篇 |
1969年 | 176篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
992.
A benzene extract of the trunk of an Aniba species (Lauraceae) contained benzyl benzoate, benzyl salicylate, sitosterol and the neolignans (2S,3S,3aR)-3a-allyl-5-methoxy-3-methyl-2-piperonyl-2,3,3a,6-tetrahydro-6-oxobenzofuran (burchellin); (2S,3S,3aR)-3a-allyl-5-methoxy-3-methyl-2-veratryl-2,3,3a,6-tetrahydro-6-oxobenzofuran; (2S,3S,3aR)-3a-allyl-5,7-dimethoxy-3-methyl-2-veratryl-2,3,3a,6-tetrahydro-6-oxobenzofuran; (2S,3S,5S)-5-allyl-5-methoxy-3-methyl-2-veratryl-2,3,5,6-tetrahydro-6-oxo-benzofuran; (2R,3R)-7-methoxy-3-methyl-5-propenyl-2-veratryl-2,3-dihydrobenzofuran; rel-(1R,5R,6R,7R,8S)-1-allyl-8-hydroxy-3-methoxy-7-methyl-4-oxo-6-piperonylbicyclo[3,2,1]oct-2-ene (guianin); rel-(1S,5S,6S,7R,8R)-1-allyl-8-hydroxy-3,5-dimethoxy-7-methyl-4-oxo-6-piperonylbicyclo[3,2,1]oct-2-ene; rel-(1S,5S,6S,7R,8R)-8-acetoxy-1-allyl-3-hydroxy-5-methoxy-7-methyl-4-oxo-6-piperonyl-bicyclo[3,2,1]oct-2-ene; rel-1S,5S,6S,7R,8R)-8-acetoxy-3,5-dimethoxy-7-methyl-4-oxo-6-piperonylbicyclo[3,2,1]oct-2-ene; rel-(1R,5S,6R,7R)-1-allyl-3-methoxy-7-methyl-4,8-dioxo-6-piperonylbicyclo[3,2,1]oct-2-ene. 相似文献
993.
The post-exercise glycogen recovery in myocardium, liver, diaphragm muscle and musculus biceps femoris was compared in untrained and trained rats. The glycogen level in myocardium of the trained rats was significantly higher than that in the untrained ones only immediately after the exercise-test and on the second day after the exercise. The liver glycogen levels on each of the examined post-exercise days were similar in both groups and did not differ from the control values. The post-exercise glycogen recovery in the diapraghm muscle of the untrained rats was also similar to that in the trained animals. In musculus bicpes femoris similar post-exercise supercompensation was found in both groups except on the second day when the glycogen level in the trained animals was significantly higher than that in the untrained ones. The results suggest that it is necessary to separate the effects of training from those of the last bout of exercise in the training program when the effect of training is examined. 相似文献
994.
995.
996.
Leonard R. Brand 《Animal behaviour》1976,24(2):319-335
A study of the vocalizations of chipmunks was conducted in the field and laboratory, utilizing sonagrams made from tape recordings, and observational data. Most observations were made on Eutamias townsendii, but interspecific variation in alarm calls was studied in all ten California species of Eutamias. The vocal repertoire of Eutamias includes several alarm calls: the chip, chuck, chippering, and in some species also the trill, and in others the whistle. Other calls include the agonistic chatter, courtship chatter, growl, and squeal. The chip is the most common call. There is consistent interspecific variation in structure and temporal arrangement of chips. Most of this variation correlates with body size. 相似文献
997.
998.
I M Szabó M Marton G Kulcsár I Buti 《Acta microbiologica Academiae Scientiarum Hungaricae》1976,23(4):371-376
Strain FBUA 1274 (=strain 28/650707, Hungarian National Collection of Medical Bacteria, National Institute of Public Health, Budapest) is designated the type strain of Thermonospora galeriensis (Vályi-Nagy et al.) comb. nov., and the morphological characteristics of this strain are described. 相似文献
999.
P Sótonyi E Somogyi A Nemes S Juhász-Nagy 《Acta morphologica Academiae Scientiarum Hungaricae》1976,24(3):279-284
Authors have observed abnormalities of glycogen localization in cardiac muscle, after normothermic cardiac arrest. The identification of these intramitrochondrial particles as glycogen was confirmed by selective staining with periodic acid-lead citrat, periodic acid-thiosemicarbazide protein methods and by their selective removal from tissue sections by alfa-amylase. The intramitochondrial glycogen particles were of beta-type. Some intramitochondrial particles were surrounded by paired membranes which resulted from protrusion of parts of mitochondrial membrane. 相似文献
1000.
Mireille Bruschi E.Claude Hatchikian Jean Le Gall JoséJ.G. Moura António V. Xavier 《BBA》1976,449(2):275-284
Three forms of ferredoxin FdI, FdI′, and FdII have been isolated from Desulfovibrio gigas, a sulfate reducer. They are separated by a combination of DEAE-cellulose and gel filtration chromatographic procedures. FdI and FdI′ present a slight difference in isoelectric point which enables the separation of the two forms over DEAE-cellulose, while FdII is easily separated from the two other forms by gel filtration. The three forms have the same amino acid composition and are isolated in different aggregation states. Molecular weight determinations by gel filtration gave values of 18 000 for FdI and FdI′ and 24 000 for FdII, whereas a value of 6000 is determined when dissociation is accomplished with sodium dodecyl sulfate. The electronic spectra are different and their ultraviolet-visible absorbance rations are 0.77, 0.87 and 0.68 respectively for FdI, FdI′ and FdII. Despite these differences, the physiological activities of the three forms are similar as far as the reduction of sulfite by molecular hydrogen is concerned. 相似文献