全文获取类型
收费全文 | 1849篇 |
免费 | 125篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 25篇 |
2021年 | 74篇 |
2020年 | 35篇 |
2019年 | 46篇 |
2018年 | 58篇 |
2017年 | 44篇 |
2016年 | 67篇 |
2015年 | 111篇 |
2014年 | 104篇 |
2013年 | 153篇 |
2012年 | 188篇 |
2011年 | 207篇 |
2010年 | 106篇 |
2009年 | 96篇 |
2008年 | 116篇 |
2007年 | 92篇 |
2006年 | 88篇 |
2005年 | 79篇 |
2004年 | 81篇 |
2003年 | 67篇 |
2002年 | 49篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1974条查询结果,搜索用时 203 毫秒
41.
Stefano Minguzzi Federica Terlizzi Chiara Lanzoni Carlo Poggi Pollini Claudio Ratti 《PloS one》2016,11(1)
Many efforts have been made to develop a rapid and sensitive method for phytoplasma and virus detection. Taking our cue from previous works, different rapid sample preparation methods have been tested and applied to Candidatus Phytoplasma prunorum (‘Ca. P. prunorum’) detection by RT-qPCR. A duplex RT-qPCR has been optimized using the crude sap as a template to simultaneously amplify a fragment of 16S rRNA of the pathogen and 18S rRNA of the host plant. The specific plant 18S rRNA internal control allows comparison and relative quantification of samples. A comparison between DNA and RNA contribution to qPCR detection is provided, showing higher contribution of the latter. The method presented here has been validated on more than a hundred samples of apricot, plum and peach trees. Since 2013, this method has been successfully applied to monitor ‘Ca. P. prunorum’ infections in field and nursery. A triplex RT-qPCR assay has also been optimized to simultaneously detect ‘Ca. P. prunorum’ and Plum pox virus (PPV) in Prunus. 相似文献
42.
Beatrice Sicurella Federica Musitelli Diego Rubolini Nicola Saino Roberto Ambrosini 《Population Ecology》2016,58(1):135-145
Several populations of long-distance migratory birds are currently suffering steep demographic declines. The identification of the causes of such declines is difficult because population changes may be driven by events occurring in distant geographical areas during different phases of the annual life-cycle of migrants. Furthermore, wintering areas and migration routes of populations of small-sized species are still largely unknown, with few exceptions. In this paper we identified the critical phases of the annual life-cycle that most influence the population dynamics of a small passerine, the Barn Swallow Hirundo rustica. We used information on temporal dynamics of a population breeding in Northern Italy, whose wintering range and timing of migration have been recently described by miniaturised tracking dataloggers. Our results indicated that primary productivity in the wintering grounds in the month when most individuals arrive from autumn migration and primary productivity in an area that is probably a stopover site during spring migration, influenced population dynamics more than habitat conditions at the breeding grounds. By using annual variation in primary productivity at the wintering grounds and stopover sites as predictors, we replicated the observed interannual population changes with great accuracy. However, the steep decline recently suffered by the population could be replicated only by including a constant annual decline in the model, suggesting that changes in primary productivity only predicted the interannual variation around the long-term trend. Our study therefore suggests the existence of critical periods during wintering and migration that may have large impact on population fluctuations of migrant birds. 相似文献
43.
The rat ErbB2 tyrosine kinase receptor produced in plants is immunogenic in mice and confers protective immunity against ErbB2+ mammary cancer 下载免费PDF全文
Slavica Matić Elena Quaglino Lucia Arata Federica Riccardo Mattia Pegoraro Marta Vallino Federica Cavallo Emanuela Noris 《Plant biotechnology journal》2016,14(1):153-159
The rat ErbB2 (rErbB2) protein is a 185‐kDa glycoprotein belonging to the epidermal growth factor‐related proteins (ErbB) of receptor tyrosine kinases. Overexpression and mutations of ErbB proteins lead to several malignancies including breast, lung, pancreatic, bladder and ovary carcinomas. ErbB2 is immunogenic and is an ideal candidate for cancer immunotherapy. We investigated the possibility of expressing the extracellular (EC) domain of rErbB2 (653 amino acids, aa) in Nicotiana benthamiana plants, testing the influence of the 23 aa transmembrane (TM) sequence on protein accumulation. Synthetic variants of the rErbB2 gene portion encoding the EC domain, optimized with a human codon usage and either linked to the full TM domain (rErbB2_TM, 676 aa), to a portion of it (rErbB2‐pTM, 662 aa), or deprived of it (rErbB2_noTM, 653 aa) were cloned in the pEAQ‐HT expression vector as 6X His tag fusions. All rErbB2 variants (72–74.5 kDa) were transiently expressed, but the TM was detrimental for rErbB2 EC accumulation. rERbB2_noTM was the most expressed protein; it was solubilized and purified with Nickel affinity resin. When crude soluble extracts expressing rErbB2_noTM were administered to BALB/c mice, specific rErbB2 immune responses were triggered. A potent antitumour activity was induced when vaccinated mice were challenged with syngeneic transplantable ErbB2+ mammary carcinoma cells. To our knowledge, this is the first report of expression of rErbB2 in plants and of its efficacy in inducing a protective antitumour immune response, opening interesting perspectives for further immunological testing. 相似文献
44.
45.
Marie-Pierre Piccinni Letizia Lombardelli Federica Logiodice Ornela Kullolli Paola Parronchi Sergio Romagnani 《Clinical and molecular allergy : CMA》2016,14(1):11
Autoimmune disorders are characterized by tissue damage, caused by self-reactivity of different effectors mechanisms of the immune system, namely antibodies and T cells. Their occurrence may be associated with genetic and/or environmental predisposition and to some extent, have implications for fertility and obstetrics. The relationship between autoimmunity and reproduction is bidirectional. This review only addresses the impact of pregnancy on autoimmune diseases and not the influence of autoimmunity on pregnancy development. Th17/Th1-type cells are aggressive and pathogenic in many autoimmune disorders and inflammatory diseases. The immunology of pregnancy underlies the role of Th2-type cytokines to maintain the tolerance of the mother towards the fetal semi-allograft. Non-specific factors, including hormonal changes, favor a switch to Th2-type cytokine profile. In pregnancy Th2, Th17/Th2 and Treg cells accumulate in the decidua but may also be present in the mother’s circulation and can regulate autoimmune responses influencing the progression of autoimmune diseases. 相似文献
46.
47.
48.
Gaetano M. Gargiulo Federica Gemelli Giuseppe Cambrea Giusy Bonanno Ferraro Alice Crosca 《Phycological Research》2019,67(1):72-76
This study focused on a method based on the capacity of cationic dyes to stain only the nucleus and chromosomes in cells subjected to either acid or alkaline hydrolysis. The method and the squash were optimized for the Characeae and were described in detail. Nuclei from vegetative shoot apices and antheridial filament cells of unfixed, fixed and herbarium material of Nitella opaca were investigated using the Azure A or Toulidine Blue stains. Comparisons with some other staining methods, used in the previous studies, were also reported. The Azure A/Toulidine Blue method is useful to obtain clear images of chromosome morphology comparable or higher to that obtained with Feulgen or Aceto‐Orcein. It requires little time and a less complicated procedure in comparison with other staining methods. 相似文献
49.
50.
Turin L Invernizzi P Woodcock M Grati FR Riva F Tribbioli G Laible G 《Biotechnology journal》2007,2(4):486-491
Fetal cells and DNA have been detected in the maternal circulation during and after pregnancy in a few mammalian species. The incidence of similar microchimerism in cattle could have repercussion for the application of modern biotechnologies such as the transfer of transgenic embryos. To determine if feto-maternal leakage can occur in pregnant cows, we have analyzed maternal blood samples for the presence of fetal DNA during gestation and post-partum periods. Y chromosome-specific DNA was detected in up to 73% of blood samples from naturally mated heifers carrying conventional bull calves and a transgene-specific sequence in up to 50% of recipient cows carrying transgenic fetuses. These findings document for the first time that transplacental leakage of fetal DNA into the maternal circulation can occur in cattle despite the epitheliochorial placenta of ruminants, with potential implications for the utilization of recipient cows in the food chain. 相似文献