全文获取类型
收费全文 | 92346篇 |
免费 | 6444篇 |
国内免费 | 11篇 |
专业分类
98801篇 |
出版年
2023年 | 482篇 |
2021年 | 866篇 |
2020年 | 781篇 |
2019年 | 795篇 |
2018年 | 2169篇 |
2017年 | 2045篇 |
2016年 | 2612篇 |
2015年 | 3140篇 |
2014年 | 3288篇 |
2013年 | 4897篇 |
2012年 | 6529篇 |
2011年 | 6507篇 |
2010年 | 3749篇 |
2009年 | 2665篇 |
2008年 | 5229篇 |
2007年 | 5236篇 |
2006年 | 5030篇 |
2005年 | 4390篇 |
2004年 | 4226篇 |
2003年 | 3887篇 |
2002年 | 3802篇 |
2001年 | 2630篇 |
2000年 | 2808篇 |
1999年 | 1774篇 |
1998年 | 781篇 |
1997年 | 596篇 |
1996年 | 667篇 |
1995年 | 622篇 |
1994年 | 584篇 |
1993年 | 522篇 |
1992年 | 902篇 |
1991年 | 769篇 |
1990年 | 725篇 |
1989年 | 717篇 |
1988年 | 653篇 |
1987年 | 637篇 |
1986年 | 585篇 |
1985年 | 677篇 |
1984年 | 640篇 |
1983年 | 580篇 |
1982年 | 509篇 |
1981年 | 467篇 |
1980年 | 419篇 |
1979年 | 574篇 |
1978年 | 445篇 |
1977年 | 421篇 |
1976年 | 404篇 |
1975年 | 470篇 |
1974年 | 462篇 |
1973年 | 441篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Y. Salas A. Márquez J. Canelón Y. Perazzo V. Colmenárez J. A. López 《Mycopathologia》2012,174(5-6):511-517
Pythium insidiosum is a pathogenic oomycete known since 1890 that causes pythiosis in mammals. In this report, seven P. insidiosum isolates were recovered from Venezuelan horses and were characterized. The strains were recovered from biopsied tissues and kunkers collected from granulomatous masses located on the hind limb and from a nodular lesion in the left upper eyelid, which decrease the ability of the horses to be used for working purposes. The methods used to identify P. insidiosum isolates were based on the production of sporangia and zoospores, histopathology and PCR assay. To further characterize these strains, portions of the 18S rRNA genes of the seven isolates were sequenced. The sequences showed high homology to previously described P. insidiosum DNA sequences available in GenBank. Similar studies based on the morphological, histological and molecular data identified the etiological agent in samples of granulomatous lesions in these equines as P. insidiosum. In America, the infection has been diagnosed more frequently in equines of Brazil, Colombia, Costa Rica and the United States of America. 相似文献
3.
4.
5.
Bodil Kjær Yean-Sung Jung Lian Yu John H. Golbeck Henrik Vibe Scheller 《Photosynthesis research》1994,41(1):105-114
The photosynthetic reaction center complex from the green sulfur bacteriumChlorobium vibrioforme has been isolated under anaerobic conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals polypeptides with apparent molecular masses of 80, 40, 30, 18, 15, and 9 kDa. The 80- and 18-kDa polypeptides are identified as the reaction center polypeptide and the secondary donor cytochromec
551 encoded by thepscA andpscC genes, respectively. N-terminal amino acid sequences identify the 40-kDa polypeptide as the bacteriochlorophylla-protein of the baseplate (the Fenna-Matthews-Olson protein) and the 30-kDa polypeptide as the putative 2[4Fe-4S] protein encoded bypscB. Electron paramagnetic resonance (EPR) analysis shows the presence of an iron-sulfur cluster which is irreversibly photoreduced at 9K. Photoaccumulation at higher temperature shows the presence of an additional photoreduced cluster. The EPR spectra of the two iron-sulfur clusters resemble those of FA and FB of Photosystem I, but also show significantly differentg-values, lineshapes, and temperature and power dependencies. We suggest that the two centers are designated Center I (with calculatedg-values of 2.085, 1.898, 1.841), and Center II (with calculatedg-values of 2.083, 1.941, 1.878). The data suggest that Centers I and II are bound to thepscB polypeptide. 相似文献
6.
7.
In a section of the Liassic southwest of the village of Préjano (Prov. Logroño) Sinemurian Dasyclad algae were found for the first time in the “Bankkalk-Series” of the “Carniolas-Formation” which is not dated up to that time. Six species,Dissocladella lucasi (Cros & Lemoine),Dissocladella iberica nov. sp.,Dissocladella ebroensis nov. sp.,Sestrosphaera liasina Pia,Gyroporella retica (Zanin) andMacroporella nov. sp. aff. sturi Bystricky are described. 相似文献
8.
9.
10.