全文获取类型
收费全文 | 1523篇 |
免费 | 82篇 |
国内免费 | 2篇 |
专业分类
1607篇 |
出版年
2024年 | 4篇 |
2023年 | 18篇 |
2022年 | 42篇 |
2021年 | 73篇 |
2020年 | 37篇 |
2019年 | 40篇 |
2018年 | 75篇 |
2017年 | 47篇 |
2016年 | 58篇 |
2015年 | 76篇 |
2014年 | 100篇 |
2013年 | 91篇 |
2012年 | 102篇 |
2011年 | 75篇 |
2010年 | 52篇 |
2009年 | 54篇 |
2008年 | 77篇 |
2007年 | 78篇 |
2006年 | 55篇 |
2005年 | 50篇 |
2004年 | 58篇 |
2003年 | 43篇 |
2002年 | 29篇 |
2001年 | 23篇 |
2000年 | 32篇 |
1999年 | 17篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1607条查询结果,搜索用时 0 毫秒
41.
Allergic inflammation develops in tissues that have large epithelial surface areas that are exposed to the environment, such as the lung, skin and gut. In the steady state, antigen-experienced memory T cells patrol these peripheral tissues to facilitate swift immune responses against invading pathogens. In at least two allergy-prone organs, the skin and the gut, memory T cells are programmed during the initial antigen priming to express trafficking receptors that enable them to preferentially home to these organs. In this review we propose that tissue-specific memory and inflammation-specific T cell trafficking facilitates the development of allergic disease in these organs. We thus review recent advances in our understanding of tissue-specific T cell trafficking and how regulation of T cell trafficking by the chemokine system contributes to allergic inflammation in mouse models and in human allergic diseases of the skin, lung and gut. Inflammation- and tissue-specific T lymphocyte trafficking pathways are currently being targeted as new treatments for non-allergic inflammatory diseases and may yield effective new therapeutics for allergic diseases. 相似文献
42.
Anther culture responsiveness of three H. spontaneum derived spring barley lines, RS170-47(A), RS20-1(B) and 1B-152B(C) was investigated using only one type of culture medium and treatment. The line 1B-152B was identified as highly responsive producing 22.4 total and 12.4 green regenerants per 100 anthers plated. 74% of these green regenerants were spontaneous double haploids. A genetic analysis involving F1 and F2 plants derived from crosses A × B and B × C revealed that the factor(s) determining high anther culture responsiveness in line 1B-152B was heritable and behaved as dominant in the F1. There was an indication that genotypic responsiveness in anther culture for green plant regeneration was different from total or albino plant regeneration. 相似文献
43.
The human cystatin C gene (CST3), mutated in hereditary cystatin C amyloid angiopathy,is located on chromosome 20 总被引:5,自引:4,他引:5
Magnus Abrahamson M. Quamrul Islam Josiane Szpirer Claude Szpirer Göran Levan 《Human genetics》1989,83(3):223-226
Summary Hereditary cystatin C amyloid angiopathy has recently been shown to be caused by a point mutation in the cystatin C gene. To determine the chromosomal localization of the gene, 20 human-rodent somatic cell hybrids and a fulllength cystatin C cDNA probe were used. Southern blot analysis of BamHI digested cell hybrid DNA revealed that the probe recognizes a 10.6 kb human specific fragment and that this fragment cosegregates with human chromosome 20. Therefore, the human cystatin C gene (CST3) was assigned to chromosome 20. 相似文献
44.
Mitochondria are frequently observed in the vicinity of chloroplasts in photosynthesizing cells, and this association is considered necessary for their metabolic interactions. We previously reported that, in leaf palisade cells of Arabidopsis thaliana, mitochondria exhibit blue‐light‐dependent redistribution together with chloroplasts, which conduct accumulation and avoidance responses under the control of blue‐light receptor phototropins. In this study, precise motility analyses by fluorescent microscopy revealed that the individual mitochondria in palisade cells, labeled with green fluorescent protein, exhibit typical stop‐and‐go movement. When exposed to blue light, the velocity of moving mitochondria increased in 30 min, whereas after 4 h, the frequency of stoppage of mitochondrial movement markedly increased. Using different mutant plants, we concluded that the presence of both phototropin1 and phototropin2 is necessary for the early acceleration of mitochondrial movement. On the contrary, the late enhancement of stoppage of mitochondrial movement occurs only in the presence of phototropin2 and only when intact photosynthesis takes place. A plasma‐membrane ghost assay suggested that the stopped mitochondria are firmly adhered to chloroplasts. These results indicate that the physical interaction between mitochondria and chloroplasts is cooperatively mediated by phototropin2‐ and photosynthesis‐dependent signals. The present study might add novel regulatory mechanism for light‐dependent plant organelle interactions. 相似文献
45.
46.
Erukainure Ochuko L. Salau Veronica F. Atolani Olubunmi Ravichandran Rahul Banerjee Priyanka Preissner Robert Koorbanally Neil A. Islam Md. Shahidul 《Amino acids》2021,53(7):1135-1151
Amino Acids - The antidiabetic effect of l-leucine has been attributed to its modulatory effect on glucose uptake and lipid metabolism in muscles. However, there is a dearth on its effect on... 相似文献
47.
Jagar?JasemEmail author Kawa?Marof Adnan?Nawar Yosra?Khalaf Sirwan?Aswad Faisal?Hamdani Monirul?Islam Andre?Kalil 《BMC neurology》2013,13(1):195
Background
Guillain-Barré syndrome (GBS) is the most common cause of acute flaccid paralysis (AFP) in the post-poliomyelitis eradication era. This is the first study done to identify the epidemiology, clinical features, and outcome of GBS in Iraqi children over 15 years.Methods
The surveillance database about AFP cases?<?15 years reported during January 1997-December 2011 was used.Results
GBS represented 52.5% of AFP cases, with an incidence of 1.33 case/100,000 population?<?15 years/year. There was a higher incidence in the Southern provinces, age group 1–4 years, males, and outside the capital city of province, with no significant seasonal variations (p?=?.22). Survival probability after the 1 year of onset for those with respiratory muscle involvement was .76 (95% CI: .60-.86), versus .97 (95% Cl: .96-.98) for those who did not develop it (p?<?.001); and .97 (95% CI: .96-.98) for those living inside the capital city, versus .94 (.93-.95) for those living outside (p?=?.001). Cumulative incidence of residual paralysis for patients living inside the capital city was .21 (95% CI: .18-.24), versus .27 (95% CI: .25-.29) for those living outside (p?<?.001).Conclusions
The incidence, age and gender distribution, and seasonality of GBS among Iraqi children is similar to those reported from other previous studies. It is the most important cause of AFP, especially in those between the age of 1 to 4 years living in rural areas.48.
49.
Renske Hijbeek Nico Koedam Md Nabiul Islam Khan James Gitundu Kairo Johan Schoukens Farid Dahdouh-Guebas 《PloS one》2013,8(6)
In vegetation science and forest management, tree density is often used as a variable. To determine the value of this variable, reliable field methods are necessary. When vegetation is sparse or not easily accessible, the use of sample plots is not feasible in the field. Therefore, plotless methods, like the Point Centred Quarter Method, are often used as an alternative. In this study we investigate the accuracy of different plotless sampling methods. To this end, tree densities of a mangrove forest were determined and compared with estimates provided by several plotless methods. None of these methods proved accurate across all field sites with mean underestimations up to 97% and mean overestimations up to 53% in the field. Applying the methods to different vegetation patterns shows that when random spatial distributions were used the true density was included within the 95% confidence limits of all the plotless methods tested. It was also found that, besides aggregation and regularity, density trends often found in mangroves contribute to the unreliability. This outcome raises questions about the use of plotless sampling in forest monitoring and management, as well as for estimates of density-based carbon sequestration. We give recommendations to minimize errors in vegetation surveys and recommendations for further in-depth research. 相似文献
50.