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   1199篇
  免费   64篇
  国内免费   56篇
耳鼻咽喉   1篇
儿科学   68篇
妇产科学   10篇
基础医学   138篇
口腔科学   21篇
临床医学   153篇
内科学   267篇
皮肤病学   51篇
神经病学   72篇
特种医学   300篇
外科学   49篇
综合类   23篇
预防医学   42篇
眼科学   5篇
药学   62篇
中国医学   2篇
肿瘤学   55篇
  2023年   6篇
  2022年   4篇
  2021年   8篇
  2020年   9篇
  2019年   8篇
  2018年   20篇
  2017年   5篇
  2016年   8篇
  2015年   15篇
  2014年   22篇
  2013年   47篇
  2012年   28篇
  2011年   25篇
  2010年   43篇
  2009年   58篇
  2008年   26篇
  2007年   58篇
  2006年   21篇
  2005年   28篇
  2004年   12篇
  2003年   14篇
  2002年   18篇
  2001年   13篇
  2000年   15篇
  1999年   20篇
  1998年   71篇
  1997年   81篇
  1996年   101篇
  1995年   61篇
  1994年   58篇
  1993年   52篇
  1992年   17篇
  1991年   15篇
  1990年   20篇
  1989年   37篇
  1988年   38篇
  1987年   34篇
  1986年   45篇
  1985年   41篇
  1984年   8篇
  1983年   15篇
  1982年   14篇
  1981年   9篇
  1980年   11篇
  1979年   8篇
  1978年   12篇
  1977年   9篇
  1976年   13篇
  1975年   13篇
  1973年   2篇
排序方式: 共有1319条查询结果,搜索用时 0 毫秒
941.
942.
943.
BACKGROUND: Some studies suggest that behavioral complications of cholestasis, such as fatigue and pruritus, may be associated with altered neurotransmission in the brain. Because inhaled anesthetics primarily act on ion channels and receptors on the neuronal cell membrane and alter synaptic transmission in the central nervous system,  相似文献   
944.
945.
Kitano  K; Rivas  CI; Baldwin  GC; Vera  JC; Golde  DW 《Blood》1993,82(9):2742-2748
Tumor necrosis factor (TNF) may play a central role in proviral activation and release from latency in cells infected with the human immunodeficiency virus (HIV). We studied viral production and its relation to TNF in a HL-60 cell line (J22-HL-60) infected with a monocytotropic strain of HIV-1JR-FL. Viral production was stimulated to similar levels by TNF, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), and 1,25-dihydroxyvitamin D3 (1,25[OH]2D3). Production of the virus was not suppressed by 3'-azido-3'-deoxythymidine (AZT), indicating that viral production was not caused by superinfection. Low concentrations of TNF (0.1 ng/mL) induced viral production with a short lag period of 8 hours, and this proviral activation was specifically suppressed by anti- TNF antibodies. However, induction of virus production by 1,25(OH)2D3 showed an extended lag period of 2 to 3 days. The effect of 1,25(OH)2D3 on virus production was also blocked by anti-TNF antibodies, which suggests the direct participation of TNF in this process. TNF accumulated in the culture supernatant of cells stimulated with 1,25(OH)2D3 with a kinetics consistent with its involvement in the action of 1,25(OH)2D3 on viral production. The J22-HL-60 cell line produced low levels of virus when cultured in the absence of an external stimulus; however, this basal viral production was suppressed greater than 80% in the presence of anti-TNF antibodies. Corresponding low levels of TNF were detected in the culture supernatants. Viral production decreased slowly with increasing passage of the cells, and no virus was detected in the supernatants of cells maintained in culture for several months. Concomitantly, TNF was no longer detected in the supernatant of these cells, which suggests that endogenous autocrine production of TNF drives viral production in the unstimulated cells. However, viral production was stimulated in these cells by low concentrations (0.1 ng/mL) of added TNF. These results argue for a central role for TNF in HIV proviral activation in chronically infected myeloid cells.  相似文献   
946.
Majumdar  S; Zoghbi  S; Pope  CF; Gore  JC 《Radiology》1988,169(3):653-658
The relaxation effects and organ distribution of superparamagnetic iron oxide particles for magnetic resonance imaging were measured in rats. T1 and T2 were measured for excised organs, and tissue iron levels were quantified with radiolabeling. Approximately 70% of the injected dose is present in the liver and 10% in the spleen 1 hour after injection. At 20 MHz, the doses required to reduce liver and spleen T2 to half the normal value, as measured with a Carr-Purcell-Meiboom-Gill sequence, were, respectively, 420 and 830 mumol iron injected per kilogram of rat. The transverse relaxation rates increase linearly with injected dose and showed no evidence of saturation. These results suggest that this material is less effective than previously suggested.  相似文献   
947.
Polycystic ovarian disease: US features in 104 patients   总被引:6,自引:0,他引:6  
Yeh  HC; Futterweit  W; Thornton  JC 《Radiology》1987,163(1):111-116
Ultrasonographic (US) study was performed in 25 healthy women and 104 patients with polycystic ovarian disease (PCOD). Although the average size of ovaries in the PCOD patients was much larger than that of the healthy women, 29.7% of ovaries in the PCOD patients were normal in size. The shapes of the ovaries (roundness index) in PCOD patients were not different from those of the healthy women. There was no significant correlation between the size and shape of the ovaries. Bilaterally enlarged, globular-shaped ovaries were rare and usually asymmetric in size. The most important feature of PCOD on US scans is the bilaterally increased numbers of developing follicles (0.5-0.8 cm in size), usually more than five in each ovary. Although maturing follicles (1.5-2.9 cm) are much rarer in PCOD patients (13.5%) than in healthy women (36%), the incidences of follicular cysts (greater than 3 cm) was about the same in both.  相似文献   
948.
Krinsky  NI; Scoon  KL; Hardin  JC; Levine  PH 《Blood》1977,50(4):597-602
Human platelet suspensions can be observed to produce small amounts of H2O2 (0.04 nmoles H2O2/min/2.5 X 10(5) cells/cu mm) and measurable chemiluminescence when exposed to target particles for phagocytosis, such as latex spherules. Both H2O2 production and chemiluminescence are characteristic of phagocytosing polymorphonuclear leukocytes (PMN) and analysis of the purified platelets indicates contamination by PMN at the level of 0.2%. The amount of H2O2 produced and the chemiluminescence observed can be duplicated by adding latex spheres to a preparation of PMN at a concentration equivalent to the contaminant in the platelet preparations. We conclude that the H2O2 produced and chemiluminescence observed from activated platelets is due to the presence of small amounts of contaminating PMN. These studies emphasize the importance of controlling for PMN contamination in studies of platelet biochemistry and physiology.  相似文献   
949.
950.

INTRODUCTION

Clinical practice guidelines recommend dietary sodium restriction in chronic kidney disease (CKD) patients. Compliance with this recommendation in a multiethnic Asian population is not clear. This study assessed the urinary sodium excretion profile of a multiethnic Asian population to estimate the population’s dietary sodium intake.

METHODS

Data on the urinary sodium excretion of 335 participants were obtained from the Asian Kidney Disease Study and Singapore Kidney Function Study. Standard statistical tests and linear regression were used to assess the association between various continuous variables and sodium excretion.

RESULTS

Our study cohort consisted of 335 participants (232 with CKD, 103 healthy) – 51.0% were male; 38.5% were Chinese, 29.6% were Malay, 23.6% were Indian; and 57.3% were hypertensive. The mean age was 53.5 ± 15.1 years and mean urinary sodium excretion was 124.9 ± 68.3 mmol/day. The mean blood pressure of the healthy participants was lower than that of the patients with CKD (p < 0.001). Patients with CKD stages 1–3 excreted an average of > 100 mmol sodium/day. Overall, 40.1% patients with CKD excreted < 100 mmol sodium/day. Indians had higher urinary sodium excretion than the Chinese (p = 0.016) and Malays (p = 0.002). The distribution of urinary sodium excretion in the healthy participants (37.9% excreted < 100 mmol sodium/day) was similar to that seen in the patients with CKD.

CONCLUSION

Although patients with CKD stages 4–5 achieved sodium restriction, healthy persons and patients with early-stage CKD need to increase their efforts in reducing their sodium intake, especially for patients of Indian ethnicity.  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