首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2599266篇
  免费   190325篇
  国内免费   7683篇
耳鼻咽喉   34537篇
儿科学   85786篇
妇产科学   72038篇
基础医学   365216篇
口腔科学   70186篇
临床医学   235730篇
内科学   518632篇
皮肤病学   62802篇
神经病学   214222篇
特种医学   100480篇
外国民族医学   744篇
外科学   389768篇
综合类   50740篇
现状与发展   6篇
一般理论   989篇
预防医学   197139篇
眼科学   57128篇
药学   189435篇
  8篇
中国医学   5445篇
肿瘤学   146243篇
  2021年   21017篇
  2019年   21320篇
  2018年   30219篇
  2017年   23171篇
  2016年   26797篇
  2015年   30161篇
  2014年   41276篇
  2013年   61456篇
  2012年   81698篇
  2011年   85966篇
  2010年   51758篇
  2009年   49785篇
  2008年   79965篇
  2007年   84832篇
  2006年   86422篇
  2005年   82498篇
  2004年   79437篇
  2003年   76622篇
  2002年   73863篇
  2001年   128577篇
  2000年   131493篇
  1999年   110657篇
  1998年   31361篇
  1997年   28000篇
  1996年   28291篇
  1995年   27448篇
  1994年   25108篇
  1993年   23452篇
  1992年   85228篇
  1991年   81628篇
  1990年   78848篇
  1989年   76115篇
  1988年   69524篇
  1987年   68050篇
  1986年   63597篇
  1985年   60568篇
  1984年   44981篇
  1983年   37994篇
  1982年   22490篇
  1981年   20016篇
  1979年   39000篇
  1978年   27460篇
  1977年   23282篇
  1976年   21512篇
  1975年   22835篇
  1974年   26804篇
  1973年   25383篇
  1972年   23762篇
  1971年   21969篇
  1970年   20195篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
G. Berlin  M. Hammar  L. Tapper 《Platelets》2019,30(4):473-479
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   
52.
53.
Introduction: In men, lower urinary tract symptoms (LUTS) are primarily attributed to benign prostatic hyperplasia (BPH). Therapeutic options are targeted to relax prostate smooth muscle and/or reduce prostate enlargement.

Areas covered: This article reviews the major preclinical and clinical data on PDE5 inhibitors with a specific focus on tadalafil. It includes details of the role of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) – PDE5 pathway in the LUT organs (bladder and prostate) in addition to the available data on tadalafil in patients with LUTS secondary to BPH with or without erectile dysfunction (ED).

Expert opinion: Preclinical and clinical data have clearly demonstrated that PDE5 inhibitors induce bladder and prostate relaxation, which contributes to the improvement seen in storage symptoms in both animal models of bladder and prostate hypercontractility. Tadalafil is effective both as a monotherapy and add-on therapy in patients with LUTS secondary to BPH. Furthermore, as LUTS-BPH and ED are urological disorders that commonly coexist in aging men, tadalafil is more advantageous than α1-adrenoceptors and should be used as the first option. Tadalafil is a safe and tolerable therapy and unlike α1- adrenoceptors and 5-alpha reductase inhibitors, which can cause sexual dysfunctions, tadalafil improves sexual function.  相似文献   

54.
55.
56.
57.
58.
Pharmaceutical Chemistry Journal - An HPLC-MS method for simultaneous quantitative determination of a novel gestagenic pharmaceutical and two of its metabolites in rat and rabbit blood sera was...  相似文献   
59.

Purpose

Endovascular treatment with mechanical thrombectomy devices demonstrated high recanalization rates but functional outcome did not correlate with high rates of recanalization obtained. Patient selection prior to the endovascular treatment is very important in the final outcome of the patient. The primary aim of our study was to evaluate the prognostic value of posterior circulation Alberta Stroke Program Early CT Score (pc-ASPECTS) and Pons-Midbrain Index (PMI) scores in patients with Basilar Artery Occlusion (BAO) treated with successful angiographic recanalization after mechanical thrombectomy.

Methods

Retrospective single-center study including 18 patients between 2008 and 2013 who had acute basilar artery occlusion managed with endovascular treatment within 24 hours from symptoms onset and with successful angiographic recanalization. The patients were initially classified into two groups according to clinical outcome and mortality at 90 days. For analysis we also divided patients into groups based on pc-ASPECTS (≥8vs.< 8) and PMI (≥3vs.< 3) on non-contrast CT (NCCT) and CT Angiography Source Images (CTASI). Imaging data were correlated to clinical outcome and mortality rate.

Results

CTASI pc-ASPECTS, dichotomized at < 8 versus≥8, was associated with a favorable outcome (RR: 2.6; 95% CI: 1.3-5.2) and a reduced risk of death (RR: 6.5: 95% CI: 7.8-23.3). All patients that survived and were functionally independent had pc-ASPECTS score≥8. None of the 5 patients with CTASI pc-ASPECTS score less than 8 survived.

Conclusion

PC-ASPECTS on CTASI is helpful for predicting functional outcome after BAO recanalization with endovascular treatment. These results should be validated in a randomized controlled trial in order to decide whether or not to treat a patient with BAO.  相似文献   
60.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号