全文获取类型
收费全文 | 923篇 |
免费 | 109篇 |
国内免费 | 26篇 |
出版年
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 21篇 |
2020年 | 16篇 |
2019年 | 15篇 |
2018年 | 26篇 |
2017年 | 9篇 |
2016年 | 31篇 |
2015年 | 47篇 |
2014年 | 42篇 |
2013年 | 79篇 |
2012年 | 72篇 |
2011年 | 74篇 |
2010年 | 45篇 |
2009年 | 37篇 |
2008年 | 41篇 |
2007年 | 31篇 |
2006年 | 30篇 |
2005年 | 29篇 |
2004年 | 28篇 |
2003年 | 20篇 |
2002年 | 23篇 |
2001年 | 25篇 |
2000年 | 24篇 |
1999年 | 25篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1983年 | 4篇 |
1979年 | 6篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1968年 | 5篇 |
1967年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有1058条查询结果,搜索用时 953 毫秒
61.
Szab Sndor Koleszr Gerg Braun Mihly Nagy Zoltn Vicei Tibor T. Peeters Edwin T. H. M. 《Ecosystems》2022,25(1):17-29
Ecosystems - Both non-rooted submerged vegetation dominated by coontail (Ceratophyllum demersum) and non-rooted floating duckweed vegetation (Lemna gibba) can maintain their stable dominance in... 相似文献
62.
Robbert A. F. van Himbeeck Willeke Huizinga Ivo Roessink Edwin T. H. M. Peeters 《Zoo biology》2019,38(4):343-354
Zoos increasingly transform their exhibitions from traditional one‐species enclosures to more natural exhibits, that is, environments that capture part of an ecosystem including a selection of animals and plants that occur there. Thus, enhancing the experience of its human visitors while also allowing its residents to possibly show more natural behavior. In 2017 Royal Burger's Zoo (Arnhem, The Netherlands) created and opened a mangrove‐like environment containing fiddler crabs. Fiddler crabs display a broad range of behaviors, and this research examines which wild‐type behavior and behavioral patterns can be observed on a seminatural mudflat. The behavior shown by Uca rapax and Uca tangeri on the mudflat was counted each hour between 07:00 and 17:00. An asymmetric tidal regime was present in the enclosure including two high water periods. Various known fiddler crab behaviors, including waving and combat, were observed but no copulation. A clear pattern in exposed crabs on the mudflat was found, with low numbers visible in the early morning and the highest numbers present in the early afternoon, while number of visitors did not have a significant effect on this pattern. Interestingly, the highest abundances were not observed around the ebbing tide (07:00–09:00), as observed in the wild, but somewhat later, possibly due to the asymmetric tidal scheme or the interaction of tidal and daily rhythms. This study shows that in captivity, fiddler crabs indeed show a range of natural behaviors which is linked to the tidal and possibly daily rhythm as well. 相似文献
63.
64.
65.
Motilin has never been isolated from rodents, the most frequently used laboratory animals, despite several attempts. We have isolated and sequenced the motilin precursor from duodenal mucosa of guinea pig (GenBank accession number AF323752) and studied its expression in several tissues. The percent homology with human motilin is the lowest yet observed due to several unique substitutions in the C-terminal end. As expected, the precursor was present in the gut mucosa with the exception of the gastric corpus. It was also present in medulla oblongata, nucleus of the solitary tract, hypophysis, spinal cord, hypothalamus, and cerebellum but not in the cerebral cortex. For the first time we demonstrated motilin expression in the thyroid. 相似文献
66.
A review of the importance of cryptosporidiosis in farm animals 总被引:20,自引:0,他引:20
de Graaf DC Vanopdenbosch E Ortega-Mora LM Abbassi H Peeters JE 《International journal for parasitology》1999,29(8):1269-1287
67.
Schaffer A Cerutti A Shah S Zan H Casali P 《Journal of immunology (Baltimore, Md. : 1950)》1999,162(9):5327-5336
68.
Identification of a new simian immunodeficiency virus lineage with a vpu gene present among different cercopithecus monkeys (C. mona, C. cephus, and C. nictitans) from Cameroon 下载免费PDF全文
Courgnaud V Abela B Pourrut X Mpoudi-Ngole E Loul S Delaporte E Peeters M 《Journal of virology》2003,77(23):12523-12534
During a large serosurvey of wild-caught primates from Cameroon, we found 2 mona monkeys (Cercopithecus mona) out of 8 and 47 mustached monkeys (Cercopithecus cephus) out of 302 with human immunodeficiency virus (HIV)-simian immunodeficiency virus (SIV) cross-reactive antibodies. In this report, we describe the full-length genome sequences of two novel SIVs, designated SIVmon-99CMCML1 and SIVmus-01CM1085, isolated from one mona (CML1) and one mustached (1085) monkey, respectively. Interestingly, these viruses displayed the same genetic organization (i.e., presence of a vpu homologue) as members of the SIVcpz-HIV type 1 lineage and SIVgsn isolated from greater spot-nosed monkeys (Cercopithecus nictitans). Phylogenetic analyses of SIVmon and SIVmus revealed that these viruses were genetically distinct from other known primate lentiviruses but were more closely related to SIVgsn all across their genomes, thus forming a monophyletic lineage within the primate lentivirus family, which we designated the SIVgsn lineage. Interestingly, mona, mustached, and greater spot-nosed monkeys are phylogenetically related species belonging to three different groups of the genus Cercopithecus, the C. mona, C. cephus, and Cercopithecus mitis groups, respectively. The presence of new viruses closely related to SIVgsn in two other species reinforces the hypothesis that a recombination event between ancestral SIVs from the family Cercopithecinae is the origin of the present SIVcpz that is widespread among the chimpanzee population. 相似文献
69.
Partial molecular characterization of two simian immunodeficiency viruses (SIV) from African colobids: SIVwrc from Western red colobus (Piliocolobus badius) and SIVolc from olive colobus (Procolobus verus) 下载免费PDF全文
Courgnaud V Formenty P Akoua-Koffi C Noe R Boesch C Delaporte E Peeters M 《Journal of virology》2003,77(1):744-748
In order to study primate lentivirus evolution in the Colobinae subfamily, in which only one simian immunodeficiency virus (SIV) has been described to date, we screened additional species from the three different genera of African colobus monkeys for SIV infection. Blood was obtained from 13 West African colobids, and HIV cross-reactive antibodies were observed in 5 of 10 Piliocolobus badius, 1 of 2 Procolobus verus, and 0 of 1 Colobus polykomos specimens. Phylogenetic analyses of partial pol sequences revealed that the new SIVs were more closely related to each other than to the other SIVs and especially did not cluster with the previously described SIVcol from Colobus guereza. This study presents evidence that the three genera of African colobus monkeys are naturally infected with an SIV and indicates also that there was no coevolution between virus and hosts at the level of the Colobinae subfamily. 相似文献
70.
Three-dimensional fluorescence recovery after photobleaching with the confocal scanning laser microscope 下载免费PDF全文
Confocal scanning laser microscopes (CSLMs) are equipped with the feature to photobleach user-defined regions. This makes them a handy tool to perform fluorescence recovery after photobleaching (FRAP) measurements. To allow quantification of such FRAP experiments, a three-dimensional model has been developed that describes the fluorescence recovery process for a disk-shaped geometry that is photobleached by the scanning beam of a CSLM. First the general mathematical basis is outlined describing the bleaching process for an arbitrary geometry bleached by a scanning laser beam. Next, these general expressions are applied to the bleaching by a CSLM of a disk-shaped geometry and an analytical solution is derived that describes three-dimensional fluorescence recovery in the bleached area as observed by the CSLM. The FRAP model is validated through both the Stokes-Einstein relation and the comparison of the measured diffusion coefficients with their theoretical estimates. Finally, the FRAP model is used to characterize the transport of FITC-dextrans through bulk three-dimensional biological materials: vitreous body isolated from bovine eyes, and lung sputum expectorated by cystic fibrosis patients. The decrease in the diffusion coefficient relative to its value in solution was dependent on the size of the FITC-dextrans in vitreous, whereas it was size-independent in cystic fibrosis sputum. 相似文献