全文获取类型
收费全文 | 1390篇 |
免费 | 166篇 |
专业分类
1556篇 |
出版年
2022年 | 16篇 |
2021年 | 20篇 |
2020年 | 15篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 22篇 |
2015年 | 45篇 |
2014年 | 52篇 |
2013年 | 50篇 |
2012年 | 74篇 |
2011年 | 80篇 |
2010年 | 49篇 |
2009年 | 38篇 |
2008年 | 71篇 |
2007年 | 58篇 |
2006年 | 47篇 |
2005年 | 46篇 |
2004年 | 57篇 |
2003年 | 61篇 |
2002年 | 48篇 |
2001年 | 47篇 |
2000年 | 56篇 |
1999年 | 42篇 |
1998年 | 25篇 |
1997年 | 21篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1992年 | 19篇 |
1991年 | 20篇 |
1990年 | 27篇 |
1989年 | 28篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 15篇 |
1972年 | 10篇 |
1970年 | 12篇 |
排序方式: 共有1556条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
165.
166.
167.
JG Hansen W Gao J Dupuis GT O’Connor W Tang M Kowgier A Sood SA Gharib LJ Palmer M Fornage SR Heckbert BM Psaty SL Booth SUNLIGHT Consortium Patricia A Cassano 《Respiratory research》2015,16(1)
Background
Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.Methods
We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV1) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV1 in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV1 in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.Results
We found a positive cross-sectional association between 25(OH)D and FEV1 in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV1 in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV1 (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV1 in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).Conclusions
Serum 25(OH)D status was associated with cross-sectional FEV1, but not longitudinal change in FEV1. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV1 and is a promising candidate gene for further studies.Electronic supplementary material
The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users. 相似文献168.
Chang LL Yang GX McCauley E Mumford RA Schmidt JA Hagmann WK 《Bioorganic & medicinal chemistry letters》2008,18(5):1688-1691
The integrin VLA-4 is implicated in several inflammatory disease states. In search of non-peptidic antagonists of VLA-4, rotational constraints were imposed on the amide bond of prototypical N-sulfonylated dipeptide VLA-4 antagonists. By judicious structural modification of the side chains, trisubstituted imidazoles with moderate binding potencies were obtained, for example, 19, VLA-4 IC(50)=237 nM. 相似文献
169.
Ginger R. Zipperer Sridhar Arumugam Sharon R. Chirgwin Sharon U. Coleman Krishna P. Shakya Thomas R. Klei 《Experimental parasitology》2013
Previous studies have shown that intradermally (ID) injected Brugia pahangi L3s migrate through various tissues and into the lymphatics of gerbils in a distinct pattern. Excretory/secretory products (ES) produced at the time of invasion of B. pahangi are likely to be important in this early migration phase of the parasite life cycle in their rodent host. Hence, early L3 ES was collected from 24 h in vitro cultures of B. pahangi L3 larvae and used in immunization experiments to investigate the effect of immunity to early L3 ES on worm migration, survival and development of B. pahangi. Immunization of gerbils with ES in RIBI adjuvant produced antibodies to numerous ES proteins eliciting a strong humoral response to ES and indirect fluorescent antibody (IFA) assay using anti-ES serum recognized the ES proteins on the surface of B. pahangi L3 larvae. Following ES immunization, gerbils were challenged either ID or intraperitoneally (IP) with 100 L3s of B. pahangi and euthanized at 3 or 106 days post inoculation (DPI). Immunization with early ES slowed the migration of ID inoculated L3 at 3 DPI and significantly altered the locations of adult worms at 106 DPI. Immunization did not induce protection in any treatment group. However, immunized animals had significantly fewer microfilariae per female worm suggesting the antigens in ES are important in microfilariae development or survival in the host. The number of lymphatic granulomas was also significantly reduced in ES immunized animals. It is important to note that microfilariae serve as a nidus in these granulomas. Our results shows immunization with early Brugia malayi L3 ES alters the worm migration, affects circulating microfilarial numbers and reduces lymphatic granulomas associated with B. pahangi infection in gerbils. 相似文献
170.