全文获取类型
收费全文 | 2502篇 |
免费 | 272篇 |
国内免费 | 5篇 |
出版年
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 48篇 |
2020年 | 23篇 |
2019年 | 31篇 |
2018年 | 49篇 |
2017年 | 37篇 |
2016年 | 72篇 |
2015年 | 116篇 |
2014年 | 109篇 |
2013年 | 128篇 |
2012年 | 192篇 |
2011年 | 174篇 |
2010年 | 122篇 |
2009年 | 118篇 |
2008年 | 122篇 |
2007年 | 126篇 |
2006年 | 90篇 |
2005年 | 86篇 |
2004年 | 103篇 |
2003年 | 81篇 |
2002年 | 68篇 |
2001年 | 82篇 |
2000年 | 70篇 |
1999年 | 63篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 16篇 |
1993年 | 23篇 |
1992年 | 47篇 |
1991年 | 33篇 |
1990年 | 32篇 |
1989年 | 45篇 |
1988年 | 35篇 |
1987年 | 29篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 17篇 |
1980年 | 25篇 |
1979年 | 38篇 |
1978年 | 20篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1974年 | 24篇 |
1973年 | 14篇 |
排序方式: 共有2779条查询结果,搜索用时 78 毫秒
51.
Pulkit Singh Wanyi Lu Zunli Lu Adam B. Jost Kimberly Lau Aviv Bachan Bas van de Schootbrugge Jonathan L. Payne 《Geobiology》2023,21(2):175-192
The end-Triassic biodiversity crisis was one of the most severe mass extinctions in the history of animal life. However, the extent to which the loss of taxonomic diversity was coupled with a reduction in organismal abundance remains to be quantified. Further, the temporal relationship between organismal abundance and local marine redox conditions is lacking in carbonate sections. To address these questions, we measured skeletal grain abundance in shallow-marine limestones by point counting 293 thin sections from four stratigraphic sections across the Triassic/Jurassic boundary in the Lombardy Basin and Apennine Platform of western Tethys. Skeletal abundance decreased abruptly across the Triassic/Jurassic boundary in all stratigraphic sections. The abundance of skeletal organisms remained low throughout the lower-middle Hettangian strata and began to rebound during the late Hettangian and early Sinemurian. A two-way ANOVA indicates that sample age (p < .01, η2 = 0.30) explains more of the variation in skeletal abundance than the depositional environment or paleobathymetry (p < .01, η2 = 0.15). Measured I/Ca ratios, a proxy for local shallow-marine redox conditions, show this same pattern with the lowest I/Ca ratios occurring in the early Hettangian. The close correspondence between oceanic water column oxygen levels and skeletal abundance indicates a connection between redox conditions and benthic organismal abundance across the Triassic/Jurassic boundary. These findings indicate that the end-Triassic mass extinction reduced not only the biodiversity but also the carrying capacity for skeletal organisms in early Hettangian ecosystems, adding to evidence that mass extinction of species generally leads to mass rarity among survivors. 相似文献
52.
Martine de Boer Maaike te Lintel Hekkert Jiang Chang Bibi S. van Thiel Leonie Martens Maxime M. Bos Marion G. J. de Kleijnen Yanto Ridwan Yanti Octavia Elza D. van Deel Lau A. Blonden Renata M. C. Brandt Sander Barnhoorn Paula K. Bautista-Niño Ilona Krabbendam-Peters Rianne Wolswinkel Banafsheh Arshi Mohsen Ghanbari Christian Kupatt Leon J. de Windt A. H. Jan Danser Ingrid van der Pluijm Carol Ann Remme Monika Stoll Joris Pothof Anton J. M. Roks Maryam Kavousi Jeroen Essers Jolanda van der Velden Jan H. J. Hoeijmakers Dirk J. Duncker 《Aging cell》2023,22(3):e13768
53.
Lars J. S. Knutsen Jesper Lau Malcolm J. Sheardown Christian Thomsen 《Bioorganic & medicinal chemistry letters》1993,3(12):2661-2666
The synthesis and SAR of a series of novel derivatives of N-aminoadenosine is described, along with their in vitro effects in biochemical assays. The rat brain A1 adenosine receptor binding of these compounds is very dependent upon the purine 2-substituent. The novel agonist, 2-chloro-N-[4-(phenylthio)-1-piperidinyl]adenosine, exhibits a Li value for A1 receptor binding of <1 nM. 相似文献
54.
Michael Stacey Peter Thygesen Lesley Stanley Nada Matas Angela Risch Edith Sim 《Biomarkers》1996,1(1):55-61
Arylamine N-acetyltransferase isoenzymes NAT1 and NAT2 are encoded at two polymorphic loci on human chromosome 8p22. The two loci have previously been identified using chimeric Yeast Artificial Chromosome (YAC) clones encoding either NAT1 or NAT2 as probes for metaphase chromosomes using fluorescent in situ hybridization. The 8p22 region has been demonstrated to be deleted in highly invasive bladder tumours and since NAT isoenzymes participate in the metabolism of arylamine bladder carcinogens, it is important to determine whether NAT1 and NAT2 gene loci are included in the region of deletion. We describe here the application of a cosmid clone for NAT2 as a biomarker for Fluorescent In Situ Hybridization (FISH) on interphase nuclei of exfoliated bladder cells. We also describe a 70kb probe for NAT1 which is a candidate for a suitable biomarker for use in similar FISH studies. lmmunohistochemical staining of bladder tumour sections with a polyclonal anti-peptide antibody specific for the NATl isoenzyme as a biomarker for NAT1 protein expression is also shown. 相似文献
55.
Dall'Olio Fabio; Mariani Erminia; Tarozzi Andrea; Meneghetti Alessandra; Chiricolo Mariella; Lau Joseph T. Y.; Facchini Andrea 《Glycobiology》1997,7(4):507-513
The extent of processing of N-linked oligosaccharides and thesialylation of the target cell membranes has been positivelycorrelated with resistance to lysis mediated by NK cells, buta conclusive evidence has never been reached. Colon cancer tissuesexpress an increased activity of ß-ga-lactoside 相似文献
56.
57.
Some pharmacological actions of prostaglandin E1 (PGE1), 6-oxo-PGE1 and PGI2 have been studied. 6-oxo-PGE1 and PGE1 relaxed guinea-pig tracheal muscle in vitro and increased nasal patency in normal volunteers and in subjects with vasomotor rhinitis whereas PGI2 produced opposite effects. All three compounds produced bronchodilatation in the anaesthetised guinea-pig and relaxed human respiratory tract muscle in vitro. PGI2 was several times more potent than either 6-oxo-PGE1 or PGE1 against ADP-induced aggregation of human and baboon platelets in vitro. Intravenous 6-oxo-PGE1 in the baboon caused an ex vivo inhibition of platelet aggregation, but the EC50 was 7.7 times that of PGI2. As a vasodepressor in the baboon 6-oxo-PGE1 and PGI2 were equipotent. Thus with the exception of the vasodepressor effect, the actions of 6-oxo-PGE1 qualitatively and quantitatively resembled those of the structurally related PGE1 rather than those of PGI2. 相似文献
58.
Formation of trichothecenes by Fusarium solani var. coeruleum and Fusarium sambucinum in potatoes. 总被引:3,自引:3,他引:0
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A A el-Banna P M Scott P Y Lau T Sakuma H W Platt V Campbell 《Applied microbiology》1984,47(5):1169-1171
Fusarium solani var. coeruleum can form deoxynivalenol in potato tubers and in liquid medium, although concentrations observed in the rot were highly variable; acetyldeoxynivalenol and HT-2 toxin were detected in 1 to 3 tubers only (of 57). Trichothecenes were also detected in a very few (3 of 20) cultures of Fusarium sambucinum in potato tubers. 相似文献
59.
60.
A male-specific DNA probe detects heterochromatin sequences in a familial Yq- chromosome. 总被引:2,自引:1,他引:1
Using a recombinant DNA probe, we have demonstrated the presence of residual 3.4-kilobase (kb) repeat sequences in a family with a Yq- chromosome. The heterochromatin of this Y variant was not readily detectable with conventional chromosome-banding techniques. These data suggest that the breakpoint of the deletion occurs at the heterochromatin region proximal to the euchromatin/heterochromatin junction. 相似文献