全文获取类型
收费全文 | 2284篇 |
免费 | 178篇 |
出版年
2023年 | 11篇 |
2022年 | 16篇 |
2021年 | 22篇 |
2020年 | 9篇 |
2019年 | 27篇 |
2018年 | 31篇 |
2017年 | 23篇 |
2016年 | 58篇 |
2015年 | 82篇 |
2014年 | 91篇 |
2013年 | 138篇 |
2012年 | 158篇 |
2011年 | 169篇 |
2010年 | 112篇 |
2009年 | 93篇 |
2008年 | 137篇 |
2007年 | 132篇 |
2006年 | 123篇 |
2005年 | 99篇 |
2004年 | 115篇 |
2003年 | 102篇 |
2002年 | 96篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 30篇 |
1998年 | 32篇 |
1997年 | 18篇 |
1996年 | 31篇 |
1995年 | 22篇 |
1994年 | 28篇 |
1993年 | 15篇 |
1992年 | 25篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 11篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 20篇 |
1984年 | 22篇 |
1983年 | 16篇 |
1982年 | 26篇 |
1981年 | 24篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1976年 | 9篇 |
1974年 | 13篇 |
1973年 | 9篇 |
1971年 | 9篇 |
1968年 | 10篇 |
排序方式: 共有2462条查询结果,搜索用时 31 毫秒
101.
Helle Glud Binderup Kim Houlind Jonna Skov Madsen Claus Lohman Brasen 《Biochemistry and Biophysics Reports》2016
BackgroundIn the past few years, an increasing number of studies have reported the potential use of microRNAs (miRNA) as circulating biomarkers for diagnosis or prognosis of a wide variety of diseases. There is, however, a lack of reproducibility between studies. Due to the high miRNA content in platelets this may partly be explained by residual platelets in the plasma samples used. When collecting fresh plasma samples, it is possible to produce cell-free/platelet-poor plasma by centrifugation. In this study, we systematically investigated whether biobanked EDTA plasma samples could be processed to be suitable for miRNA analysis.Materials and methodsBlood samples were collected from ten healthy volunteers and centrifuged to produce platelet-poor-plasma (PPP) and standard biobank plasma. After one week at ?80 °C the biobanked EDTA plasma was re-centrifuged by different steps to remove residual platelets. Using RT-qPCR the levels of 14 miRNAs in the different plasma preparations were compared to that of PPP.ResultsWe were able to remove residual platelets from biobanked EDTA plasma by re-centrifugation of the thawed samples. Nevertheless, for most of the investigated miRNAs, the miRNA level was significantly higher in the re-centrifuged biobanked plasma compared to PPP, even when the platelet count was reduced to 0–1×109/L.ConclusionWe found, that pre-storage centrifugation conditions have a significant impact on the measured EDTA plasma level of miRNAs known to be present in platelets. Even for the miRNAs found to be less effected, we showed that a 1.5–3 fold change in plasma levels may possible be caused by or easily overseen due to sample preparation and/or storage. 相似文献
102.
103.
104.
Jörg Dutz Josianne G. Støttrup Claus Stenberg Peter Munk 《Marine Biology Research》2016,12(8):785-796
Shallow, near-shore water habitats on the continental shelf of the Northeast Atlantic have been productive fishing areas in the past. Here, we review the present knowledge about (i) recent trends in the abundance of plaice and cod in these habitats and (ii) hypotheses regarding the factors responsible for any trends. At present, only a few studies exist on the trends of abundance of plaice or cod, namely from the Bay of Biscay, the North Sea and the Skagerrak/Kattegat. They suggest a declining abundance in coastal, shallow areas and – at least for plaice – a latitudinal gradient with an erosion of the southern distribution boundary in the Bay of Biscay and deepening of stocks in the North Sea. In contrast, no trend in shallow water abundance of plaice similar to a decline in deep-water stocks during the 1970s and their slow recovery during the 2000s is apparent in the Skagerrak/Kattegat. Although shallow habitats fundamentally differ from deeper areas by the prevalence of juvenile stages, the declining trends coincide with decreasing abundance/landings and spatial stock relocations in the deeper areas. Whether this indicates a common trend pointing at connectivity between shallow and deep water remains open. Fundamental differences exist in the suggested causes of the trends in different geographical areas. High fishing pressure together with low local recruitment apparently prevents the recovery of overexploited plaice and cod stocks in the Skagerrak/Kattegat. In contrast, the responses of juveniles and adult fish to increasing seawater temperature are the main hypotheses for changes in distribution and abundance of both fish species in the North Sea/Bay of Biscay. However, temperature alone cannot explain the observed decline of fish in coastal areas, and the causes may be more complex, involving nutrient loading, primary productivity or food availability, although at present, knowledge of these factors is insufficient. 相似文献
105.
Hans Yu Lena Hackenbroch Florian R. L. Meyer Judith Reiser Ebrahim Razzazi‐Fazeli Katharina Nbauer Urban Besenfelder Claus Vogl Gottfried Brem Corina Mayrhofer 《Proteomics》2019,19(5)
Oviductal fluid (ODF) proteins modulate and support reproductive processes in the oviduct. In the present study, proteins involved in the biological events that precede fertilization have been identified in the rabbit ODF proteome, isolated from the ampulla and isthmus of the oviduct at different time points within 8 h after intrauterine insemination. A workflow is used that integrates lectin affinity capture with stable‐isotope dimethyl labeling prior to nanoLC‐MS/MS analysis. In total, over 400 ODF proteins, including 214 lectin enriched glycoproteins, are identified and quantified. Selected data are validated by Western blot analysis. Spatiotemporal alterations in the abundance of ODF proteins in response to insemination are detected by global analysis. A subset of 63 potentially biologically relevant ODF proteins is identified, including extracellular matrix components, chaperones, oxidoreductases, and immunity proteins. Functional enrichment analysis reveals an altered peptidase regulator activity upon insemination. In addition to protein identification and abundance changes, N‐glycopeptide analysis further identifies 281 glycosites on 199 proteins. Taken together, these results show, for the first time, the evolving oviductal milieu early upon insemination. The identified proteins are likely those that modulate in vitro processes, including spermatozoa function. 相似文献
106.
107.
Winkler Alexander Claus Duncan Murray Ian Farthing Matthew William Potts Warren Mason 《Reviews in Fish Biology and Fisheries》2019,29(3):605-611
Reviews in Fish Biology and Fisheries - While otoliths are considered the most reliable structure to accurately age fish, a variety of otolith preparation techniques are available, which have... 相似文献
108.
Jezierska Sylwia Claus Silke Ledesma-Amaro Rodrigo Van Bogaert Inge 《Journal of industrial microbiology & biotechnology》2019,46(12):1697-1706
Journal of Industrial Microbiology & Biotechnology - Free fatty acids are basic oleochemicals implemented in a range of applications including surfactants, lubricants, paints, plastics, and... 相似文献
109.
Gluconobacter oxydans rapidly oxidizes many different polyhydroxy alcohols (polyols). Polyol oxidations are catalyzed by constitutively synthesized membrane-bound dehydrogenases directly linked to the electron transport chain. A polyol-oxidizing enzyme was isolated from the membranes of G. oxydans and tested for its ability to oxidize various substrates. The enzyme was composed of three subunits: a 67 kDa catalytic unit, a 46 kDa c-type cytochrome, and a 15 kDa subunit. The enzyme oxidized compounds containing three or more hydroxyl groups but did not oxidize mono-, di-, or cyclic alcohols; aldehydes; carboxylic acids; or mono- or di-saccharides. Therefore, we propose this enzyme be considered a polyol dehydrogenase. 相似文献
110.
Elena SF Wilke CO Ofria C Lenski RE 《Evolution; international journal of organic evolution》2007,61(3):666-674
It is often assumed that the efficiency of selection for mutational robustness would be proportional to mutation rate and population size, thus being inefficient in small populations. However, Krakauer and Plotkin (2002) hypothesized that selection in small populations would favor robustness mechanisms, such as redundancy, that mask the effect of deleterious mutations. In large populations, by contrast, selection is more effective at removing deleterious mutants and fitness would be improved by eliminating mechanisms that mask the effect of deleterious mutations and thus impede their removal. Here, we test whether these predictions are supported in experiments with evolving populations of digital organisms. Digital organisms are self-replicating programs that inhabit a virtual world inside a computer. Like their organic counterparts, digital organisms mutate, compete, evolve, and adapt by natural selection to their environment. In this study, 160 populations evolved at different combinations of mutation rate and population size. After 10(4) generations, we measured the mutational robustness of the most abundant genotype in each population. Mutational robustness tended to increase with mutation rate and to decline with population size, although the dependence with population size was in part mediated by a negative relationship between fitness and robustness. These results are independent of whether genomes were constrained to their original length or allowed to change in size. 相似文献