全文获取类型
收费全文 | 21398篇 |
免费 | 1575篇 |
国内免费 | 87篇 |
专业分类
耳鼻咽喉 | 188篇 |
儿科学 | 598篇 |
妇产科学 | 516篇 |
基础医学 | 2636篇 |
口腔科学 | 468篇 |
临床医学 | 2264篇 |
内科学 | 4132篇 |
皮肤病学 | 196篇 |
神经病学 | 2140篇 |
特种医学 | 723篇 |
外国民族医学 | 3篇 |
外科学 | 3564篇 |
综合类 | 290篇 |
一般理论 | 16篇 |
预防医学 | 1716篇 |
眼科学 | 477篇 |
药学 | 1745篇 |
中国医学 | 14篇 |
肿瘤学 | 1374篇 |
出版年
2023年 | 76篇 |
2022年 | 155篇 |
2021年 | 354篇 |
2020年 | 234篇 |
2019年 | 379篇 |
2018年 | 454篇 |
2017年 | 332篇 |
2016年 | 358篇 |
2015年 | 443篇 |
2014年 | 615篇 |
2013年 | 915篇 |
2012年 | 1418篇 |
2011年 | 1478篇 |
2010年 | 834篇 |
2009年 | 698篇 |
2008年 | 1395篇 |
2007年 | 1596篇 |
2006年 | 1374篇 |
2005年 | 1386篇 |
2004年 | 1430篇 |
2003年 | 1251篇 |
2002年 | 1249篇 |
2001年 | 241篇 |
2000年 | 213篇 |
1999年 | 263篇 |
1998年 | 281篇 |
1997年 | 256篇 |
1996年 | 198篇 |
1995年 | 162篇 |
1994年 | 159篇 |
1993年 | 158篇 |
1992年 | 187篇 |
1991年 | 166篇 |
1990年 | 153篇 |
1989年 | 133篇 |
1988年 | 114篇 |
1987年 | 123篇 |
1986年 | 131篇 |
1985年 | 103篇 |
1984年 | 111篇 |
1983年 | 116篇 |
1982年 | 109篇 |
1981年 | 120篇 |
1980年 | 97篇 |
1979年 | 85篇 |
1978年 | 96篇 |
1976年 | 87篇 |
1975年 | 72篇 |
1974年 | 74篇 |
1972年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Goodman MT Wu AH Tung KH McDuffie K Cramer DW Wilkens LR Terada K Reichardt JK Ng WG 《American journal of epidemiology》2002,156(8):693-701
Deficiency in the galactose-1-phosphate uridyltransferase (GALT) enzyme results in accumulation of galactose and its metabolites in the ovary (Am J Epidemiol 1989;130:904-10). Galactose may raise gonadotropin levels, resulting in proliferation of ovarian epithelium. In 1993-1999, the authors conducted a population-based case-control study of ovarian cancer in Hawaii and Los Angeles, California, to examine the hypothesis that reduced GALT activity is associated with an increased risk of ovarian cancer. A total of 239 ovarian cancer cases and 244 population controls were interviewed. A blood sample was collected to measure levels of GALT and to assay for the N314D (A940G) polymorphism of the GALT gene. Covariate-adjusted mean GALT activity was similar between cases (23.8 micro mol per hour/g hemoglobin (Hb)) and controls (23.7 micro mol per hour/g Hb) (p = 0.83). No evidence was found for a dose-response relation between the odds ratios for ovarian cancer and GALT activity or the ratio of lactose intake to GALT activity. The risk associated with the presence of at least one variant Asp314 allele was 0.77 (95% confidence interval: 0.42, 1.41). This study did not support the hypothesis that reduced galactose metabolism is a risk factor for ovarian cancer, although increased GALT activity attenuated the inverse association of oral contraceptive pill use with risk. 相似文献
992.
Knapik JJ Canham-Chervak M Hauret K Laurin MJ Hoedebecke E Craig S Montain SJ 《The Annals of occupational hygiene》2002,46(1):15-23
OBJECTIVES: Previous literature suggests that injury rates during physical activity may be higher in the summer than in the fall or winter, possibly due to the greater amount or intensity of physical activity in the summer. This study examined seasonal differences in injury incidence during US Army Basic Combat Training, where physical activity was similar at all times of the year. METHODS: Four independent groups of subjects (total n = 1543 men and 1025 women) were investigated, two training in the summer and two training in the fall. Injury data were obtained from a retrospective review of the subjects' medical records at the conclusion of the 8 week training program. RESULTS: For men, the corrected relative risk of suffering an injury or a time loss injury in the summer was, respectively, 2.0 [95% confidence interval (CI) = 1.7-2.4] and 2.5 (95% CI = 1.9-3.0) times higher than in the fall. For women, the corrected relative risk of suffering an injury or time-loss injury in the summer was, respectively, 1.4 (95% CI = 1.3-1.6) and 1.7 (95% CI = 1.5-2.0) times higher than in the fall. These risks were essentially unchanged after adjustment for subject physical characteristics (age, stature, body mass, body mass index) and physical fitness (push-ups, sit-ups and 2 mile run), indicating that the summer season was an injury risk factor independent of these variables. Linear correlations (r-values) between maximal daily temperature and injury incidence ranged from 0.92 to 0.97, indicating a strong relationship between these two variables. CONCLUSIONS: These data suggest that injury incidence among physically active individuals is higher in the summer than in the fall and that environmental temperature may provide a partial explanation for this finding. 相似文献
993.
994.
995.
Early adolescent boys (n = 587) and girls (n = 619) and a parent completed questionnaires, that assessed child dieting behaviors, body dissatisfaction and tendency to overeat, child's current and ideal size, mother and father dieting, and encouragement of the child to diet. 相似文献
996.
Trujillo KA 《Neurotoxicity research》2002,4(4):373-391
Long-term administration of opiates leads to changes in the effects of these drugs, including tolerance, sensitization and physical dependence. There is, as yet, incomplete understanding of the neural mechanisms that underlie these phenomena. Tolerance, sensitization and physical dependence can be considered adaptive processes similar to other experience-dependent changes in the brain, such as learning and neural development. There is considerable evidence demonstrating that N-methyl-D-aspartate (NMDA) receptors and downstream signaling cascades may have an important role in different forms of experience-dependent changes in the brain and behavior. This review will explore evidence indicating that NMDA receptors and downstream messengers may be involved in opiate tolerance, sensitization and physical dependence. This evidence has been used to develop a cellular model of NMDA receptor/opiate interactions. According to this model, mu opioid receptor stimulation leads to a protein kinase C-mediated activation of NMDA receptors. Activation of NMDA receptors leads to influx of calcium and activation of calcium-dependent processes. These calcium-dependent processes have the ability to produce critical changes in opioid-responsive neurons, including inhibition of opioid receptor/second messenger coupling. This model is similar to cellular models of learning and neural development in which NMDA receptors have a central role. Together, the evidence suggests that the mechanisms that underlie changes in the brain and behavior produced by long-term opiate use may be similar to other central nervous system adaptations. The experimental findings and the resulting model may have implications for the treatment of pain and addiction. 相似文献
997.
998.
999.
This paper provides an update on the Association of Postdoctoral Programs in Clinical Neuropsychology (APPCN), which was formed in 1992. The paper summarizes the historical background of APPCN, reports on contemporary influences on APPCN and its role in postdoctoral education and training in neuropsychology, and provides an update on APPCN's most recent initiatives. The paper includes a list of current members in APPCN and explains how other postdoctoral residency programs in clinical neuropsychology may apply for membership. 相似文献
1000.