全文获取类型
收费全文 | 2185篇 |
免费 | 171篇 |
国内免费 | 105篇 |
出版年
2023年 | 18篇 |
2022年 | 44篇 |
2021年 | 81篇 |
2020年 | 47篇 |
2019年 | 57篇 |
2018年 | 61篇 |
2017年 | 45篇 |
2016年 | 76篇 |
2015年 | 133篇 |
2014年 | 159篇 |
2013年 | 155篇 |
2012年 | 197篇 |
2011年 | 177篇 |
2010年 | 108篇 |
2009年 | 89篇 |
2008年 | 108篇 |
2007年 | 106篇 |
2006年 | 94篇 |
2005年 | 83篇 |
2004年 | 87篇 |
2003年 | 54篇 |
2002年 | 57篇 |
2001年 | 28篇 |
2000年 | 33篇 |
1999年 | 39篇 |
1998年 | 26篇 |
1997年 | 27篇 |
1996年 | 19篇 |
1995年 | 23篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 21篇 |
1991年 | 11篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1976年 | 6篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1966年 | 3篇 |
1965年 | 6篇 |
排序方式: 共有2461条查询结果,搜索用时 15 毫秒
51.
52.
53.
Macromitrium filicaule Müll.Hal., M. pacificum var. brevisetum Thér. and M. subnitidum Müll.Hal are placed in synonymy with Macromitrium microstomum (Hook. & Grev.) Schwägr. The morphological variations of M. microstomum branch leaves, perichaetial leaves and capsules are illustrated by digital images. 相似文献
54.
Background
The association between methylenetetrahydrofolate reductase (MTHFR) 677C > T polymorphism and lung cancer risk has been studied in various populations with conflicting results. The aim of this study was to assess the association strength by a meta-analysis of published studies.Methods
We searched PubMed and Chinese Biomedical (CBM) databases for relevant literatures published by July 18, 2012. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated to assess the strength of the association.Results
A total of 20 studies comprising 11,653 cases and 12,032 controls were included in the final meta-analysis. Using the random effect model, we found that MTHFR 677TT variant genotype was associated with an increased lung cancer risk (OR = 1.26, 95% CI = 1.05–1.50, P = 0.011 for TT vs. CC; OR = 1.19, 95% CI = 1.03–1.37, P < 0.001 for TT vs. CC + CT; OR = 1.11, 95% CI = 1.02–1.22, P = 0.017 for T allele vs. C allele). In the further stratified analyses, the increased lung cancer risk was found in Asian subjects (OR = 1.31, 95% CI = 1.01–1.71, P = 0.045 for TT vs. CC; OR = 1.17, 95% CI = 1.00–1.38, P = 0.048 for TT vs. CC + CT). There were no evidences for obvious publication bias in the overall meta-analysis and Asian subjects.Conclusions
MTHFR 677TT genotype might increase the susceptibility of lung cancer, especially in Asians. 相似文献55.
56.
Zhijun Wu Yuqing Lou Wei Jin Yan Liu Lin Lu Guoping Lu 《Molecular biology reports》2013,40(4):3101-3112
The researches attempting to associate the PPARγ C161T polymorphism with coronary artery disease (CAD) yielded complicated and contradictory results. We aimed for more precise estimate of the relationship and conducted a comprehensive meta-analysis. Publications written in English or Chinese were screened in MEDLINE, Embase, CNKI, Wanfang and CBM. Data on 11 studies including 3,020 cases and 2,853 controls were extracted. A random-effects model was available to synthesize the inconsistent outcomes of the individual studies, while addressing between-study heterogeneity and publication bias. The PPARγ C161T polymorphism followed Hard-Weinberg Equilibrium for all studies (P > 0.05).Overall, there was no evidence for a significant association under all genetic models but with distinct heterogeneity (T vs. C: P = 0.29, OR = 0.91, 95 %CI 0.77–1.08, P heterogeneity = 0.004, I 2 = 61.2 %). However, in the subgroup analysis by ethnicity, the T allele carriers showed a prominent 26 % risk reduction of CAD among Chinese (dominant genetic model: P = 0.03, 95 %CI 0.57–0.97, P heterogeneity = 0.03, I 2 = 56.1 %). After dividing into population source, the significance of CAD risk reduction was strengthened in hospital-based studies (allele comparison: P = 0.04, OR = 0.82, 95 %CI 0.67–1.00, P heterogeneity = 0.04, I 2 = 52.5 %; dominant model: P = 0.01, OR = 0.73, 95 %CI 0.57–0.92, P heterogeneity = 0.05, I 2 = 50.8 %). There was no obvious publication bias verified in the method of funnel plot and Egger’s linear regression test (t = ?0.11, P = 0.913). Taken together, our results revealed the PPARγ C161T polymorphism might play a moderate protective effect on developing CAD among Chinese, but not among Caucasians. 相似文献
57.
Xiahui Ge Chong Bai Jianming Yang Guoliang Lou Qiang Li Ruohua Chen 《Journal of cellular biochemistry》2013,114(7):1595-1605
Previous studies proved that bone marrow‐derived mesenchymal stem cells (BMSCs) could improve a variety of immune‐mediated disease by its immunomodulatory properties. In this study, we investigated the effect on airway remodeling and airway inflammation by administrating BMSCs in chronic asthmatic mice. Forty‐eight female BALB/c mice were randomly distributed into PBS group, BMSCs treatment group, BMSCs control group, and asthmatic group. The levels of cytokine and immunoglobulin in serum and bronchoalveolar lavage fluid were detected by enzyme‐linked immunosorbent assay. The number of CD4+CD25+regulatory T cells and morphometric analysis was determined by flow cytometry, hematoxylin‐eosin, immunofluorescence staining, periodic‐acid Schiff, and masson staining, respectively. We found that airway remodeling and airway inflammation were evident in asthmatic mice. Moreover, low level of IL‐12 and high levels of IL‐13, IL‐4, OVA‐specific IgG1, IgE, and IgG2a and the fewer number of CD4+CD25+regulatory T cells were present in asthmatic group. However, transplantation of BMSCs significantly decreased airway inflammation and airway remodeling and level of IL‐4, OVA‐specific IgE, and OVA‐specific IgG1, but elevated level of IL‐12 and the number of CD4 + CD25 + regulatory T cells in asthma (P < 0.05). However, BMSCs did not contribute to lung regeneration and had no significant effect on levels of IL‐10, IFN‐Y, and IL‐13. In our study, BMSCs engraftment prohibited airway inflammation and airway remodeling in chronic asthmatic group. The beneficial effect of BMSCs might involved the modulation imbalance cytokine toward a new balance Th1–Th2 profiles and up‐regulation of protective CD4 + CD25 + regulatory T cells in asthma, but not contribution to lung regeneration. J. Cell. Biochem. 114: 1595–1605, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
58.
59.
Yifeng Wu Yuanheng Cai Yi Sun Ruixue Xu Haina Yu Xiaojuan Han Hongxiang Lou Aixia Cheng 《FEBS letters》2013
Alkenal double bond reductases (DBRs) catalyze the NADPH-dependent reduction of the α,β-unsaturated double bond of many secondary metabolites. Two alkenal double bond reductase genes PaDBR1 and PaDBR2 were isolated from the liverwort species Plagiochasma appendiculatum. Recombinant PaDBR2 protein had a higher catalytic activity than PaDBR1 with respect to the reduction of the double bond present in hydroxycinnamyl aldehydes. The residue at position 56 appeared to be responsible for this difference in enzyme activity. The functionality of a C56 to Y56 mutation in PaDBR1 was similar to that of PaDBR2. Further site-directed mutagenesis and structural modeling suggested that the phenol ring stacking between this residue and the substrate was an important determinant of catalytic efficiency. 相似文献
60.