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   493篇
  免费   30篇
耳鼻咽喉   13篇
儿科学   3篇
妇产科学   7篇
基础医学   68篇
口腔科学   13篇
临床医学   17篇
内科学   65篇
皮肤病学   101篇
神经病学   60篇
特种医学   5篇
外科学   73篇
综合类   5篇
一般理论   1篇
预防医学   17篇
眼科学   20篇
药学   46篇
中国医学   1篇
肿瘤学   8篇
  2023年   3篇
  2022年   1篇
  2021年   9篇
  2020年   6篇
  2019年   10篇
  2018年   16篇
  2017年   11篇
  2016年   9篇
  2015年   8篇
  2014年   22篇
  2013年   24篇
  2012年   46篇
  2011年   35篇
  2010年   25篇
  2009年   21篇
  2008年   36篇
  2007年   50篇
  2006年   37篇
  2005年   20篇
  2004年   18篇
  2003年   12篇
  2002年   13篇
  2001年   17篇
  2000年   11篇
  1999年   4篇
  1998年   1篇
  1997年   4篇
  1996年   1篇
  1995年   2篇
  1994年   3篇
  1992年   5篇
  1991年   6篇
  1990年   1篇
  1989年   2篇
  1988年   2篇
  1987年   6篇
  1986年   3篇
  1985年   4篇
  1984年   2篇
  1981年   2篇
  1980年   4篇
  1978年   1篇
  1977年   2篇
  1976年   3篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1969年   1篇
  1968年   1篇
排序方式: 共有523条查询结果,搜索用时 15 毫秒
31.
A rare case of angiokeratoma Fordyce localized on the margin of the glans penis in a 52-year-old Caucasian patient is reported. Combined treatment with Erbium: YAG and 532 nm KTP (frequency doubled Neodynium: YAG) laser led to excellent cosmetic results.  相似文献   
32.
Working memory (WM) deficits are common in HIV-seropositive (HIV+) individuals and can be amplified by manipulating a variety of task parameters, such as increasing memory load or information complexity. The authors investigated the role of timing in HIV-associated WM defects by varying the amount of time required to maintain information online while holding memory load and information complexity constant. The authors studied 50 HIV+ and 35 HIV-seronegative (HIV-) polydrug abusers abstinent at testing and well-matched on demographic variables. The HIV- group outperformed the HIV+ group across all stimulus-response time delays. HIV-associated WM defects are not critically dependent on the amount of time stimulus representations must be maintained and might be attributed to impaired encoding or retrieval of stimulus representations.  相似文献   
33.
BACKGROUND: The octogenarian patient is often perceived as too fragile to undergo cardiothoracic surgery. Our study aimed to compare postoperative complications in patients aged less than 80 versus elderly patients (80 years or more) after surgical cardiac intervention (coronary artery bypass or valve replacement). METHODS: Subjects were all patients (n = 8,361) who had an open-heart procedure, either coronary artery bypass or valve implantation or replacement, at two medical centers located in northern Virginia using the same surgical group. A computerized medical record database was reviewed to determine preoperative risk factors and postoperative outcomes. Predictors of complications were identified by univariate and multivariate logistic regression. RESULTS: A total of 3,214 complications were recorded. The most prevalent complications were prolonged ventilation time in the intensive care unit, reoperation for bleeding, and pneumonia. The overall mortality rate was 2.4% (204 of 8,361). Persons aged over 80 years had nearly double the mortality rate compared with younger patients (4.1% [18 of 444] to 2.3% [186 of 7,917]). Age greater than 80 years (odds ratio = 2.65, 95% confidence interval = 2.18 to 3.22) and male gender (odds ratio = 0.62, 95% confidence interval = 0.56 to 0.69) were the best univariate predictors of a single postoperative complication. CONCLUSIONS: Octogenarian patients manifested twice the risk of death from a cardiac intervention with an average 2-day longer hospital stay compared with their younger counterparts. Furthermore, octogenarians were at markedly higher risk of nonfatal postoperative complications.  相似文献   
34.
Aminoacetone (AA) is a threonine and glycine catabolite long known to accumulate in cri-du-chat and threoninemia syndromes and, more recently, implicated as a contributing source of methylglyoxal (MG) in diabetes mellitus. Oxidation of AA to MG, NH(4)(+), and H(2)O(2) has been reported to be catalyzed by a copper-dependent semicarbazide sensitive amine oxidase (SSAO) as well as by Cu(II) ions. We here study the mechanism of AA aerobic oxidation, in the presence and absence of iron ions, and coupled to iron release from ferritin. Aminoacetone (1-7 mM) autoxidizes in Chelex-treated phosphate buffer (pH 7.4) to yield stoichiometric amounts of MG and NH(4)(+). Superoxide radical was shown to propagate this reaction as indicated by strong inhibition of oxygen uptake by superoxide dismutase (SOD) (1-50 units/mL; up to 90%) or semicarbazide (0.5-5 mM; up to 80%) and by EPR spin trapping studies with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), which detected the formation of the DMPO-(*)OH adduct as a decomposition product from the DMPO-O(2)(*)(-) adduct. Accordingly, oxygen uptake by AA is accelerated upon addition of xanthine/xanthine oxidase, a well-known enzymatic source of O(2)(*)(-) radicals. Under Fe(II)EDTA catalysis, SOD (<50 units/mL) had little effect on the oxygen uptake curve or on the EPR spectrum of AA/DMPO, which shows intense signals of the DMPO-(*)OH adduct and of a secondary carbon-centered DMPO adduct, attributable to the AA(*) enoyl radical. In the presence of iron, simultaneous (two) electron transfer from both Fe(II) and AA to O(2), leading directly to H(2)O(2) generation followed by the Fenton reaction is thought to take place. Aminoacetone was also found to induce dose-dependent Fe(II) release from horse spleen ferritin, putatively mediated by both O(2)(*)(-) and AA(*) enoyl radicals, and the co-oxidation of added hemoglobin and myoglobin, which may be viewed as the initial step for potential further iron release. It is thus tempting to propose that AA, accumulated in the blood and other tissues of diabetics, besides being metabolized by SSAO, may release iron and undergo spontaneous and iron-catalyzed oxidation with production of reactive H(2)O(2) and O(2)(*)(-), triggering pathological responses. It is noteworthy that noninsulin-dependent diabetes has been frequently associated with iron overload and oxidative stress.  相似文献   
35.
36.
Previous evidence has shown that morphine produces positive reinforcing effects (as measured in the place conditioning paradigm) through an action in the central nervous system (CNS). The aversive conditioning effects of morphine (as measured in the place and taste conditioning paradigms) were produced when drug action was restricted to peripheral sites, particularly in the gut region. We now demonstrate that most of the aversive conditioning effects of morphine (using place and taste conditioning paradigms) are receptor mediated effects exerted through an action on peripheral opiate receptors. The conditioned taste aversions induced by intraperitoneal (IP) morphine (15 mg/kg) but not amphetamine (1 mg/kg) were attenuated by low IP doses of opiate antagonists (0.1 mg/kg of naltrexone or 1 mg/kg of the peripherally acting antagonist methynaltrexone (MN]. Morphine-, but not amphetamine-induced conditioned taste aversions were also attenuated in animals whose small sensory neurons, bearing the majority of primary afferent opiate receptors, were destroyed by neonatal treatments with capsaicin. In the place conditioning paradigm, the aversive conditioning effects produced by low IP administrations of morphine were blocked by opiate antagonists. Intraperitoneal pretreatments with 1 mg/kg of the quaternary opiate antagonist MN (which does not cross the blood-brain barrier effectively) were shown to block the conditioned place aversions produced by low IP doses of morphine (0.05 mg/kg), but not the place aversions produced by lithium chloride (75 mg/kg IP), or by high doses of naloxone (10 mg/kg SC). These results demonstrate that the aversive conditioning effects of morphine are primarily mediated through an action on peripheral opiate receptors.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
37.
38.
39.
40.

Background

Subintimal endovascular intervention has been used widely in the treatment of symptomatic superficial femoral artery (SFA) occlusion. The relative effectiveness of subintimal placement of a covered stent (CS) versus balloon-only subintimal angioplasty (SIA) remains uncertain.

Methods

We performed a retrospective cohort study of consecutive patients with symptomatic SFA occlusions (>15 cm) who underwent subintimal endovascular intervention, either CS or SIA, in a single institution. Primary patency was the primary outcome. Secondary outcomes included complication rates, freedom from re-intervention, and limb salvage rates. Patency was ascertained with followup duplex or clinically.

Results

We evaluated 57 patients in the SIA group and 31 patients in the CS group. At 1 year the SFA primary patency for the SIA and CS groups was 28% versus 75% (P < .001), whereas the primary assisted patency was 37% versus 84% (P < .001), respectively. Need for bypass was 13% versus 0% (P = .05) in the SIA and CS groups, respectively.

Conclusions

Placement of a covered stent improves patency after subintimal intervention for long SFA occlusion.  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