全文获取类型
收费全文 | 3568篇 |
免费 | 295篇 |
国内免费 | 6篇 |
专业分类
3869篇 |
出版年
2023年 | 29篇 |
2022年 | 78篇 |
2021年 | 117篇 |
2020年 | 76篇 |
2019年 | 92篇 |
2018年 | 80篇 |
2017年 | 78篇 |
2016年 | 109篇 |
2015年 | 177篇 |
2014年 | 199篇 |
2013年 | 239篇 |
2012年 | 285篇 |
2011年 | 298篇 |
2010年 | 180篇 |
2009年 | 145篇 |
2008年 | 207篇 |
2007年 | 178篇 |
2006年 | 162篇 |
2005年 | 152篇 |
2004年 | 125篇 |
2003年 | 133篇 |
2002年 | 106篇 |
2001年 | 36篇 |
2000年 | 19篇 |
1999年 | 33篇 |
1998年 | 29篇 |
1997年 | 20篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1988年 | 14篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 28篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1973年 | 13篇 |
1972年 | 14篇 |
1971年 | 9篇 |
1967年 | 8篇 |
1960年 | 8篇 |
排序方式: 共有3869条查询结果,搜索用时 15 毫秒
951.
952.
Sonya J. Elder Alice H. Lichtenstein Anastassios G. Pittas Susan B. Roberts Paul J. Fuss Andrew S. Greenberg Megan A. McCrory Thomas J. Bouchard Jr. Edward Saltzman Michael C. Neale 《Journal of lipid research》2009,50(9):1917-1926
The relative influence of genetics and the environment on factors associated with cardiovascular disease (CVD) and metabolic syndrome (MetS) remains unclear. We performed model-fitting analyses to quantify genetic, common environmental, and unique environmental variance components of factors associated with CVD and MetS [waist circumference, blood pressure, fasting plasma glucose and insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and fasting plasma lipids] in adult male and female monozygotic twins reared apart or together. We also investigated whether MetS components share common influences. Plasma cholesterol and triglyceride concentrations were highly heritable (56–77%, statistically significant). Waist circumference, plasma glucose and insulin, HOMA-IR, and blood pressure were moderately heritable (43–57%, statistically significant). Unique environmental factors contributed to the variance of all variables (20–38%, perforce statistically significant). Common environmental factors contributed 23, 30, and 42% (statistically significant) of the variance of waist circumference, systolic blood pressure, and plasma glucose, respectively. Two shared factors influenced MetS components; one influenced all components except HDL cholesterol, another influenced only lipid (triglyceride and HDL cholesterol) concentrations. These results suggest that genetic variance has a dominant influence on total variance of factors associated with CVD and MetS and support the proposal of one or more underlying pathologies of MetS. 相似文献
953.
954.
955.
Carmen D. Samuel‐Hodge Larry F. Johnston Ziya Gizlice Beverly A. Garcia Sara C. Lindsley Kathy P. Bramble Trisha E. Hardy Alice S. Ammerman Patricia A. Poindexter Julie C. Will Thomas C. Keyserling 《Obesity (Silver Spring, Md.)》2009,17(10):1891-1899
Low‐income women in the United States have the highest rates of obesity, yet they are seldom included in weight loss trials. To address this research gap, components of two evidence‐based weight loss interventions were adapted to create a 16‐week intervention for low‐income women (Weight Wise Program), which was evaluated in a randomized trial with the primary outcome of weight loss at 5‐month follow‐up. Participants were low‐income women (40–64 years) with a BMI of 25–45. Of 143 participants, 72 were randomized to the Weight Wise Program (WWP) and 71 to the Control Group (CG). Five‐month follow‐up data were obtained from 64 (89%) WWP and 62 (87%) CG participants. With baseline values carried forward for missing data, WWP participants had a weight change of ?3.7 kg compared to 0.7 kg in the CG (4.4 kg difference, 95% confidence interval (CI), 3.2–5.5, P < 0.001). For systolic blood pressure (SBP), change in the WWP was ?6.5 mm Hg compared to ?0.4 mm Hg among controls (6.2 mm Hg difference, 95% CI, 1.7–10.6, P = 0.007); for diastolic BP (DBP), changes were ?4.1 mm Hg for WWP compared to ?1.3 mm Hg for controls (2.8 mm Hg difference, 95% CI, 0.0–5.5, P = 0.05). Of the 72 WWP participants, 64, 47, and 19% lost at least 3, 5, and 7% of their initial body weight, respectively. In conclusion, the WWP was associated with statistically significant and clinically important short‐term weight loss. 相似文献
956.
John Paul SanGiovanni Dan E. Arking Sudha K. Iyengar Michael Elashoff Traci E. Clemons George F. Reed Alice K. Henning Theru A. Sivakumaran Xuming Xu Andrew DeWan Elvira Agrón Elena Rochtchina Carolyn M. Sue Jie Jin Wang Paul Mitchell Josephine Hoh Peter J. Francis Michael L. Klein Emily Y. Chew Aravinda Chakravarti 《PloS one》2009,4(5)
Background
Age-related macular degeneration (AMD), a chronic neurodegenerative and neovascular retinal disease, is the leading cause of blindness in elderly people of western European origin. While structural and functional alterations in mitochondria (mt) and their metabolites have been implicated in the pathogenesis of chronic neurodegenerative and vascular diseases, the relationship of inherited variants in the mitochondrial genome and mt haplogroup subtypes with advanced AMD has not been reported in large prospective cohorts.Methodology/Prinicipal Findings
We examined the relationship of inherited mtDNA variants with advanced AMD in 1168 people using a three-stage design on samples from 12-year and 10-year prospective studies on the natural history of age-related eye disease. In Stage I we resequenced the entire genome in 99 elderly AMD-free controls and 215 people with advanced AMD from the 12-year study. A consistent association with AMD in 14 of 17 SNPs characterizing the mtDNA T haplogroup emerged. Further analysis revealed these associations were driven entirely by the T2 haplogroup, and characterized by two variants in Complex I genes (A11812G of MT-ND4 and A14233G of MT-ND6). We genotyped T haplogroups in an independent sample of 490 cases and 61 controls from the same study (Stage II) and in 56 cases and 246 controls from the 10-year study (Stage III). People in the T2 haplogroup were approximately 2.5 times more likely to have advanced AMD than their peers (odds ratio [OR] = 2.54, 95%CI 1.36–4.80, P≤0.004) after considering the totality of evidence. Findings persisted after considering the impact of AMD-associated variants A69S and Y402H (OR = 5.19, 95%CI 1.19–22.69, P≤0.029).Conclusion
Loci defining the mtDNA T2 haplogroup and Complex I are reasonable targets for novel functional analyses and therapeutic research in AMD. 相似文献957.
Xiao-Feng Li James S. Kinsey-Jones Yewsong Cheng Alice M. I. Knox Yuanshao Lin Nikoletta A. Petrou Antonia Roseweir Stafford L. Lightman Stuart R. Milligan Robert P. Millar Kevin T. O'Byrne 《PloS one》2009,4(12)
Background
Kisspeptin and its G protein-coupled receptor (GPR) 54 are essential for activation of the hypothalamo-pituitary-gonadal axis. In the rat, the kisspeptin neurons critical for gonadotropin secretion are located in the hypothalamic arcuate (ARC) and anteroventral periventricular (AVPV) nuclei. As the ARC is known to be the site of the gonadotropin-releasing hormone (GnRH) pulse generator we explored whether kisspeptin-GPR54 signalling in the ARC regulates GnRH pulses.Methodology/Principal Findings
We examined the effects of kisspeptin-10 or a selective kisspeptin antagonist administration intra-ARC or intra-medial preoptic area (mPOA), (which includes the AVPV), on pulsatile luteinizing hormone (LH) secretion in the rat. Ovariectomized rats with subcutaneous 17β-estradiol capsules were chronically implanted with bilateral intra-ARC or intra-mPOA cannulae, or intra-cerebroventricular (icv) cannulae and intravenous catheters. Blood samples were collected every 5 min for 5–8 h for LH measurement. After 2 h of control blood sampling, kisspeptin-10 or kisspeptin antagonist was administered via pre-implanted cannulae. Intranuclear administration of kisspeptin-10 resulted in a dose-dependent increase in circulating levels of LH lasting approximately 1 h, before recovering to a normal pulsatile pattern of circulating LH. Both icv and intra-ARC administration of kisspeptin antagonist suppressed LH pulse frequency profoundly. However, intra-mPOA administration of kisspeptin antagonist did not affect pulsatile LH secretion.Conclusions/Significance
These data are the first to identify the arcuate nucleus as a key site for kisspeptin modulation of LH pulse frequency, supporting the notion that kisspeptin-GPR54 signalling in this region of the mediobasal hypothalamus is a critical neural component of the hypothalamic GnRH pulse generator. 相似文献958.
959.
Ashley M. Vaughan Matthew T. O'Neill Alice S. Tarun Nelly Camargo Thuan M. Phuong Ahmed S. I. Aly Alan F. Cowman Stefan H. I. Kappe 《Cellular microbiology》2009,11(3):506-520
Intracellular malaria parasites require lipids for growth and replication. They possess a prokaryotic type II fatty acid synthesis (FAS II) pathway that localizes to the apicoplast plastid organelle and is assumed to be necessary for pathogenic blood stage replication. However, the importance of FAS II throughout the complex parasite life cycle remains unknown. We show in a rodent malaria model that FAS II enzymes localize to the sporozoite and liver stage apicoplast. Targeted deletion of FabB/F , a critical enzyme in fatty acid synthesis, did not affect parasite blood stage replication, mosquito stage development and initial infection in the liver. This was confirmed by knockout of FabZ , another critical FAS II enzyme. However, FAS II-deficient Plasmodium yoelii liver stages failed to form exo-erythrocytic merozoites, the invasive stage that first initiates blood stage infection. Furthermore, deletion of FabI in the human malaria parasite Plasmodium falciparum did not show a reduction in asexual blood stage replication in vitro . Malaria parasites therefore depend on the intrinsic FAS II pathway only at one specific life cycle transition point, from liver to blood. 相似文献
960.