全文获取类型
收费全文 | 2405764篇 |
免费 | 176872篇 |
国内免费 | 4001篇 |
专业分类
耳鼻咽喉 | 35128篇 |
儿科学 | 81303篇 |
妇产科学 | 68278篇 |
基础医学 | 347526篇 |
口腔科学 | 68052篇 |
临床医学 | 206396篇 |
内科学 | 475083篇 |
皮肤病学 | 52464篇 |
神经病学 | 188973篇 |
特种医学 | 93383篇 |
外国民族医学 | 974篇 |
外科学 | 365024篇 |
综合类 | 49749篇 |
现状与发展 | 1篇 |
一般理论 | 658篇 |
预防医学 | 185756篇 |
眼科学 | 55617篇 |
药学 | 181579篇 |
3篇 | |
中国医学 | 4879篇 |
肿瘤学 | 125811篇 |
出版年
2018年 | 26436篇 |
2017年 | 19534篇 |
2016年 | 21515篇 |
2015年 | 24378篇 |
2014年 | 33233篇 |
2013年 | 50767篇 |
2012年 | 71073篇 |
2011年 | 75522篇 |
2010年 | 44159篇 |
2009年 | 41079篇 |
2008年 | 71390篇 |
2007年 | 76954篇 |
2006年 | 77290篇 |
2005年 | 75398篇 |
2004年 | 72819篇 |
2003年 | 70305篇 |
2002年 | 68929篇 |
2001年 | 108601篇 |
2000年 | 112310篇 |
1999年 | 95385篇 |
1998年 | 26731篇 |
1997年 | 23887篇 |
1996年 | 24253篇 |
1995年 | 22984篇 |
1994年 | 21733篇 |
1993年 | 20093篇 |
1992年 | 75901篇 |
1991年 | 74407篇 |
1990年 | 72962篇 |
1989年 | 70127篇 |
1988年 | 65079篇 |
1987年 | 63919篇 |
1986年 | 60280篇 |
1985年 | 57748篇 |
1984年 | 43376篇 |
1983年 | 36970篇 |
1982年 | 21891篇 |
1981年 | 19631篇 |
1979年 | 40162篇 |
1978年 | 28075篇 |
1977年 | 24208篇 |
1976年 | 22820篇 |
1975年 | 24927篇 |
1974年 | 29311篇 |
1973年 | 28312篇 |
1972年 | 26588篇 |
1971年 | 24534篇 |
1970年 | 23005篇 |
1969年 | 21657篇 |
1968年 | 20199篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Platelets are needed to prevent or arrest bleeding and aggregate at the site of injury upon vascular damage. Platelets express receptors for estrogens which might affect the function of the platelets and their hemostatic ability. The aim was to identify possible differences in platelet function related to age, gender, and phases of the menstrual cycle by use of impedance aggregometry with Multiplate. In the first part of the study, platelet function was assessed in 60 healthy individuals (30 men and 30 women) in each of three age groups (20–25, 40–45, and 60–65 years). In the second part of the study, the platelet function was analyzed on four occasions during the menstrual cycle in women without oral contraceptives (OCs) (n = 17) and compared to 19 women on OCs and 18 men of similar age (20–40 years). For the women on OCs, aggregation was analyzed once during the tablet-free week and once late during the period with OCs. The men were sampled once. Women of younger age (<45 years) had significantly higher agonist-induced aggregation response than both men and post-menopausal women (60–65 years). The agonist-induced aggregation response did not differ between phases of the menstrual cycle or OC use. The results suggest that estradiol and/or progesterone affect spontaneous aggregation since it was found to be lowest in the mid-luteal phase. Spontaneous aggregation was significantly lower in women on OCs than in both men and women without OCs. Our findings indicate that fertile age is associated with higher aggregation response capacity of the platelets, possibly to prevent excessive bleeding during menstruation, but this response capacity is not altered during the menstrual cycle or by use of OCs. 相似文献
22.
23.
24.
25.
26.
27.
Madan M. Rehani Emily R. Melick Raza M. Alvi Ruhani Doda Khera Salma Batool-Anwar Tomas G. Neilan Michael Bettmann 《European radiology》2020,30(4):1839-1846
To determine percent of patients without malignancy and ≤ 40 years of age with high cumulative radiation doses through recurrent CT exams and assess imaging appropriateness. From the cohort of patients who received cumulative effective dose (CED) of ≥ 100 mSv over a 5-year period, a sub-set was identified with non-malignant disease. The top 50 clinical indications leading to multiple CTs were determined. Clinical decision support (CDS) system scores were analyzed using a widely adopted standard of 1–3 (red) as “not usually appropriate,” 4–6 (yellow) “may or may not be appropriate,” and 7–9 (green) “usually appropriate.” Clinicians reviewed patient records to assess compliance with appropriate use criteria (AUC). 9.6% of patients in our series were with non-malignant conditions and 1.4% with age ≤ 40 years. CDS scores (rounded) were 2% red, 38% yellow, 27% green, and 33% unscored CTs. Clinical society guidelines for CT exams, wherever available, were followed in 87.5 to 100% of cases. AUCs were not available for several clinical indications as also referral guidelines for serial CT imaging. More than half of CT exams were unrelated to follow-up of a primary chronic disease. We are faced with a situation wherein patients in age ≤ 40 years require or are thought to require many CT exams over the course of a few years but the radiation risk creates concern. There is a fair number of conditions for which AUC are not available. Suggested solutions include development of CT scanners with lesser radiation dose and further development of appropriateness criteria. 相似文献
28.
29.
30.
Alexandra B. Morshed Rachel G. Tabak Cynthia D. Schwarz Debra Haire-Joshu 《Journal of nutrition education and behavior》2019,51(2):237-244