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   4715篇
  免费   210篇
  国内免费   20篇
耳鼻咽喉   32篇
儿科学   71篇
妇产科学   66篇
基础医学   527篇
口腔科学   172篇
临床医学   308篇
内科学   1079篇
皮肤病学   135篇
神经病学   384篇
特种医学   342篇
外科学   778篇
综合类   30篇
预防医学   257篇
眼科学   46篇
药学   269篇
中国医学   2篇
肿瘤学   447篇
  2023年   38篇
  2022年   85篇
  2021年   137篇
  2020年   67篇
  2019年   63篇
  2018年   123篇
  2017年   85篇
  2016年   95篇
  2015年   108篇
  2014年   134篇
  2013年   167篇
  2012年   300篇
  2011年   274篇
  2010年   145篇
  2009年   130篇
  2008年   234篇
  2007年   257篇
  2006年   206篇
  2005年   263篇
  2004年   211篇
  2003年   214篇
  2002年   189篇
  2001年   96篇
  2000年   96篇
  1999年   100篇
  1998年   46篇
  1997年   34篇
  1996年   32篇
  1995年   34篇
  1994年   21篇
  1993年   20篇
  1992年   61篇
  1991年   59篇
  1990年   53篇
  1989年   82篇
  1988年   93篇
  1987年   56篇
  1986年   56篇
  1985年   68篇
  1984年   41篇
  1983年   43篇
  1982年   22篇
  1981年   19篇
  1980年   16篇
  1979年   39篇
  1974年   22篇
  1972年   23篇
  1971年   27篇
  1969年   23篇
  1968年   23篇
排序方式: 共有4945条查询结果,搜索用时 15 毫秒
51.
Aims/IntroductionThe evidence regarding the effects of coffee consumption on incident chronic kidney disease is inconclusive, and no studies have investigated the relationship in patients with diabetes. We aimed to prospectively investigate the relationship between coffee consumption and the decline in estimated glomerular function rate (eGFR) in patients with type 2 diabetes.Materials and MethodsA total of 3,805 patients (2,112 men, 1,693 women) with type 2 diabetes (mean age 64.2 years) and eGFR ≥60 mL/min/1.73 m2 were followed (completion of follow up, 97.6%; median 5.3 years). Coffee consumption was assessed at baseline. The end‐point was a decline in eGFR to <60 mL/min/1.73 m2 during the follow‐up period.ResultsDuring follow up, 840 participants experienced a decline in eGFR to <60 mL/min/1.73 m2. Higher coffee consumption reduced the risk of decline in eGFR. Compared with no coffee consumption, the multivariate‐adjusted hazard ratios (95% confidence intervals) were 0.77 (0.63–0.93) for less than one cup per day, 0.77 (0.62–0.95) for one cup per day and 0.75 (0.62–0.91) for two or more cups per day (P for trend 0.01). This trend was unaffected by further adjustment for baseline eGFR and albuminuria. The mean eGFR change per year was −2.16 mL/min/1.73 m2 with no coffee consumption, −1.89 mL/min/1.73 m2 with less than one cup per day, −1.80 mL/min/1.73 m2 with one cup per day and −1.78 mL/min/1.73 m2 with two or more cups per day (P for trend 0.03).ConclusionsCoffee consumption is significantly associated with a lower risk of decline in eGFR in patients with type 2 diabetes.  相似文献   
52.
This study was conducted to compare maternal plasma adiponectin concentrations and adiponectin expression in term placentas between normotensive pregnant women and pre-eclamptic women. Plasma adiponectin concentrations were assessed by a sandwich enzyme-linked immunosorbent assay in 81 normotensive pregnant women, 27 pre-eclamptic women and 15 non-pregnant healthy women. The expression of adiponectin in the placentas was assessed by immunohistochemistry. Plasma adiponectin concentrations in normotensive pregnant women did not show a significant change during pregnancy and postpartum compared with non-pregnant women. However, plasma adiponectin concentrations in pre-eclamptic women were significantly (p < 0.05) lower than in non-pregnant and normotensive pregnant women. No immunoreactive adiponectin was detected in the term placentas of normotensive pregnant women, whereas a positive immunostaining for adiponectin was observed in endothelial cells of chorionic vessels in pre-eclamptic women. Our data suggest that decreased plasma adiponectin concentrations may contribute to the pathophysiology of pre-eclampsia and that adiponectin localized in chorionic vessels may play a role in the restoring of endothelial damage in the feto-maternal units of pre-eclampsia.  相似文献   
53.
Intestinal membrane permeability is an important factor affecting the bioavailability of drugs. As a strategy to improve membrane permeability, membrane transporters are useful targets since essential nutrients are absorbed efficiently via specific transporters. For example, there are reports that intestinal hexose transporters could be used as a tool to improve permeability; however, there has been no direct evidence that the transporter protein, sodium/glucose cotransporter 1 (SGLT1), is involved in the transport of hexose analogs. Accordingly, we examined directly whether the intestinal membrane permeability of hexose analogs can be improved by utilizing SGLT1. Three hexose-quinoline derivatives were synthesized and their interactions with SGLT1 were evaluated. Among the three derivatives, the glucose-quinoline molecule exhibited an inhibitory effect on D-glucose uptake by both rat intestinal brush-border membrane vesicles (BBMVs) and Xenopus oocytes expressing SGLT1. In addition, significant uptake of the glucose-quinoline derivative by Xenopus oocytes expressing SGLT1 was observed by both an electrophysiological assay and direct measurement of the uptake of the compound, while the galactose-quinoline derivative did not show significant uptake via SGLT1. Thus, it was directly demonstrated that SGLT1 could be used as a tool for the improvement of intestinal membrane permeability of drugs by modification to the glucose analogs.  相似文献   
54.
A zinc balance study was conducted on low birth weight infants (670 to 2420 g) fed unsupplemented human milk (the mother's or pooled) (group 1, n = 17) or human milk with zinc supplementation (group 2, n = 17). The mean zinc concentrations of the diets in groups 1 and 2 were 2.2 +/- 1.1 mg/L and 8.4 +/- 0.8 mg/L, respectively, and the mean copper concentration of the diets in both groups was 0.45 +/- 0.12 mg/L. The studies were performed 7 to 128 days after birth, which corresponded to 29 to 43 weeks postconceptional age. The turning point of zinc balance from negative to positive appeared to be greatly influenced by the postconceptional age, being approximately 36 weeks in both group 1 and group 2, rather than other factors such as the zinc intake and the postnatal age. The calculated minimal requirement of dietary zinc during the period from 36 to 40 weeks postconceptional age, for an adequate amount of zinc retention in infants (250 micrograms/kg/d), was 0.8 mg/kg/d. Zinc supplementation did not appear to interfere with copper retention.  相似文献   
55.
56.
57.
58.
Immune checkpoint inhibitors (ICIs), which have anti-tumor effects, are currently approved for treatment of several kinds of advanced malignancies. However, with their increasing use, a variety of immune-related adverse events (irAEs) in administered patients have been reported. We herein report a rare case of the simultaneous onset of acute pancreatitis and colitis as irAEs during nivolumab treatment given to a patient with renal cell carcinoma, who then shown marked improvement with corticosteroid therapy.  相似文献   
59.
Two cases of primary malignant lymphoma of the intestine were examined by ultrasonography. In the first case, the lymphoma originated from the terminal ileum and caused intussusception. The tumor was significantly hypoechoic. In the second case, the tumor showed pseudokidney sign. The echo level of the tumor was low and the size of the tumor was over 10 cm.  相似文献   
60.
Regulatory T cells (Tregs) have been reported to play a pivotal role in the vascular remodeling of pulmonary arterial hypertension (PAH). Recent studies have revealed that Tregs are heterogeneous and can be characterized by three phenotypically and functionally different subsets. In this study, we investigated the roles of Treg subsets in the pathogenesis of PAH in eight patients with PAH and 14 healthy controls. Tregs and their subsets in peripheral blood samples were analyzed by flow cytometry. Treg subsets were defined as CD4+CD45RA+FoxP3low resting Tregs (rTregs), CD4+CD45RA?FoxP3high activated Tregs (aTregs), and CD4+CD45RA?FoxP3low non-suppressive Tregs (non-Tregs). The proportion of Tregs among CD4+ T cells was significantly higher in PAH patients than in controls (6.54 ± 1.10 vs. 3.81 ± 0.28 %, p < 0.05). Of the three subsets, the proportion of non-Tregs was significantly elevated in PAH patients compared with controls (4.06 ± 0.40 vs. 2.79 ± 0.14 %, p < 0.01), whereas those of rTregs and aTregs were not different between the two groups. Moreover, the expression levels of cytotoxic T lymphocyte antigen 4, a functional cell surface molecule, in aTregs (p < 0.05) and non-Tregs (p < 0.05) were significantly higher in PAH patients compared with controls. These results suggested the non-Treg subset was expanded and functionally activated in peripheral lymphocytes obtained from IPAH patients. We hypothesize that immunoreactions involving the specific activation of the non-Treg subset might play a role in the vascular remodeling of PAH.  相似文献   
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