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   580篇
  免费   34篇
  国内免费   9篇
耳鼻咽喉   3篇
儿科学   30篇
妇产科学   17篇
基础医学   77篇
口腔科学   5篇
临床医学   34篇
内科学   184篇
皮肤病学   19篇
神经病学   39篇
特种医学   11篇
外科学   80篇
预防医学   43篇
眼科学   11篇
药学   25篇
中国医学   1篇
肿瘤学   44篇
  2024年   2篇
  2023年   6篇
  2022年   15篇
  2021年   18篇
  2020年   24篇
  2019年   23篇
  2018年   13篇
  2017年   21篇
  2016年   25篇
  2015年   22篇
  2014年   29篇
  2013年   29篇
  2012年   47篇
  2011年   51篇
  2010年   34篇
  2009年   17篇
  2008年   34篇
  2007年   44篇
  2006年   44篇
  2005年   45篇
  2004年   23篇
  2003年   20篇
  2002年   20篇
  2001年   2篇
  2000年   1篇
  1999年   6篇
  1998年   3篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   1篇
排序方式: 共有623条查询结果,搜索用时 31 毫秒
11.
Between July 1990 and June 1996, 284 exposures to infectious material were reported by 247 health care workers (HCWs) at AHEPA University Hospital, Thessaloniki, Greece, representing an overall rate of 2.4% reported injuries per 100 HCWs/year. Nurses reported the highest rates of incidents (3.0%) and in all but one working group women exhibited higher injury rates per year than male HCWs. Young workers (21-30 years old) were primarily affected in incidents (P < 0.001). Needles were the most common implement causing injury (60.6%) and resheathing of used needles as well as garbage collection were common causes of injury. None of the HCWs seroconverted in exposures where immune status to blood-borne pathogens was estimated. Efforts by the infection control committee need to be more intense, in order to increase the rate of reported staff injuries. This will facilitate identification of unsafe practices and provide more adequate preventive measures.  相似文献   
12.
13.
Lung - A correction to this paper has been published: https://doi.org/10.1007/s00408-021-00428-8  相似文献   
14.
15.
16.
Oxidized organic aerosol (OOA) is a major component of ambient particulate matter, substantially impacting climate, human health, and ecosystems. OOA is readily produced in the presence of sunlight, and requires days of photooxidation to reach the levels observed in the atmosphere. High concentrations of OOA are thus expected in the summer; however, our current mechanistic understanding fails to explain elevated OOA during wintertime periods of low photochemical activity that coincide with periods of intense biomass burning. As a result, atmospheric models underpredict OOA concentrations by a factor of 3 to 5. Here we show that fresh emissions from biomass burning exposed to NO2 and O3 (precursors to the NO3 radical) rapidly form OOA in the laboratory over a few hours and without any sunlight. The extent of oxidation is sensitive to relative humidity. The resulting OOA chemical composition is consistent with the observed OOA in field studies in major urban areas. Additionally, this dark chemical processing leads to significant enhancements in secondary nitrate aerosol, of which 50 to 60% is estimated to be organic. Simulations that include this understanding of dark chemical processing show that over 70% of organic aerosol from biomass burning is substantially influenced by dark oxidation. This rapid and extensive dark oxidation elevates the importance of nocturnal chemistry and biomass burning as a global source of OOA.

Highly oxidized organic aerosol (OOA) is a dominant component of particulate matter air pollution globally (13); however, sources of OOA remain uncertain, limiting the ability of models to accurately represent OOA and thus predict the associated climate, ecosystem, and health implications (4, 5). The current conceptual model of OOA formation suggests that anthropogenic OOA predominantly originates from the oxidation of volatile (VOCs), intermediate volatility (IVOCs), and semivolatile (SVOCs) organic compounds by the OH radical, resulting in lower-volatility products that condense to the particle phase (6). As the OH radical is formed through photolysis and has a very short atmospheric lifetime [less than a second (7)], this oxidation mechanism only occurs in the presence of sunlight. Further, the time scale for OOA formation through oxidation with OH in models is on the order of a few days (8). While this understanding is sufficient in explaining OOA concentrations in summer or periods with high solar radiation, atmospheric models fail to reproduce the observed concentration of OOA in the ambient atmosphere during winter and low-light conditions (9, 10). Fountoukis et al. (9) found simulated OOA concentrations significantly underestimated in wintertime Paris. Tsimpidi et al. (10) also reported an underprediction of simulated OOA globally in winter, suggesting missing sources of both primary OA (POA) and secondary formation pathways. This underproduction suggests a possible overlooked conversion pathway of organic vapors or particles to OOA that is not accounted for in current chemical transport and climate models.As stricter controls on fossil fuel combustion are implemented, residential biomass burning (BB) as a source of heating or cooking is becoming an increasingly important source of OA in urban environments (1, 11, 12). Further, increasing rates of wildfires from climate change are increasing the frequency of smoke-impacted days in urban areas (1214). BB emissions include high concentrations of POA, SVOCs, IVOCs, and VOCs (15, 16), thus making BB a key source of OOA. Previous research has focused on quantifying the concentration of OOA formed through photochemical oxidation reactions (i.e., OH) with BB emissions (17, 18). However, oxidation of BB emissions in low or no sunlight is less well understood and is not included in chemical transport models. As opposed to OH, the NO3 radical is formed through reactions with NO2 and O3 and is rapidly lost in the presence of sunlight (19). Thus, the NO3 radical is only available in significant concentrations at night or other low-light conditions (20, 21). Previous research has established that biogenic VOCs may undergo oxidation at night when mixed with anthropogenic emissions containing NO2 and O3 (19, 2227). There have been only a few studies that consider that nighttime oxidation of residential wood combustion may proceed through similar pathways (2831); however, the magnitude and relevance to observed OOA in the ambient atmosphere has not yet been established. By combining laboratory experiments and ambient observations to inform a chemical transport model, we present strong evidence that nighttime oxidation of BB plumes (proceeding through reactions with O3 and the NO3 radical) is an important source of OOA.  相似文献   
17.
The benefits of combined deferoxamine (DFO) and deferiprone (L1) chelation therapy, focusing on reducing myocardial iron loading, have been widely reported. Herein, we present the efficacy of combined chelation and its effects on iron load indices. Five thalassemia major (TM) patients who were undergoing chelation monotherapy with DFO were enrolled. Inclusion criteria were magnetic resonance imaging (MRI) T2* values, indicating serious heart and/or liver transfusional hemosiderosis. Combined therapy was started with the same dose of DFO and the addition of L1. The MRI T2* studies were repeated 18 months later. An Echo-Doppler study was performed in order to further evaluate the left ventricular (LV) systolic function. Within the 18 months' follow-up period, there was a significant statical decrease in mean serum ferritin levels. All patients increased their MRI T2* liver values, while two patients with very low MRI T2* also increased their myocardial values. The MRI ejection fraction (EF) and Echo-Doppler study measurements confirmed the improvement of systolic function. No adverse effects were reported. Combined L1 and DFO therapy seems to be effective in reducing iron excess in organ iron overloaded thalassemic patients. Magnetic resonance imaging can accurately quantify iron load, while echocardiography remains a reliable monitoring technology.  相似文献   
18.
We describe a 36-year-old man with advanced multiple myeloma (Salmon and Durie stage III) who developed jaundice and severe cholestasis after a first cure with systemic chemotherapy of vincristine, doxorubicin, and oral dexamethasone (VAD). Serology for hepatitis A, B, and C and for CMV was negative. A liver ultrasound and CT scan showed mild hepatomegaly without evidence of extrahepatic or intrahepatic biliary tree dilatation. A percutaneous liver biopsy revealed perisinusoidal deposits of an abundant slightly eosinophilic, PAS-positive amorphous substance. Immunohistochemistry showed positivity for kappa-light chains and was negative for lambda-light chains, for IgA, IgG, IgM, and IgD immunoglobulins as well as for AA and AL proteins and for amyloid P component. A diagnosis of light chain deposition disease (LCDD) of the liver was made. The patient developed rapid deterioration of liver function, leading to a multisystem dysfunction and death. The occurrence of LCDD in multiple myeloma is close to 5% and myeloma is the underlying disease in two thirds of patients with LCDD. The kidneys are involved in almost all cases of LCDD and renal dysfunction usually reveals the disease. Only three patients with LCDD of the liver without overt renal involvement have been reported so far. This is the first observation of LCDD presenting with jaundice and severe cholestasis shortly after the diagnosis of high tumor mass myeloma, without overt renal involvement, leading rapidly to the patient's death.  相似文献   
19.
Pollen grains from the plant cover of a given area participate largely in the composition of aeroflora (pollen and molds) of this area. Association of allergic respiratory disorders with concentration of allergenic particles in the atmosphere is well documented, and aerobiologic studies are of great relevance. A 10-year volumetric aerobiologic study was conducted in the city of Heraklion, located in the center of the north-shore of the island of Crete, Greece. Main allergenic families and genera encountered were, in descending order of frequency Oleaceae, Quercus, Platanaceae, Cupressaceae, Pinaceae, Populus, Moraceae, and Corylaceae. Concentrations noted for most of these aeroallergens were much lower than those reported from other European regions. In parallel, an atopic population of 576 individuals, exhibiting allergic symptoms mainly of the respiratory tract were subjected to a battery of skin-prick tests. A fair degree of agreement between total pollen counts and positive skin-prick test frequencies for the families of Oleaceae, Platanaceae, and Cupressaceae was noted. On the contrary a poor degree of concordance was noted for the rest of the families and genera.  相似文献   
20.
Reliable predictors of outcomes after treatment discontinuation in HBeAg‐negative chronic hepatitis B (CHB) patients have not been established. We investigated the role of hepatitis B surface antigen (HBsAg), interferon‐inducible protein‐10 (IP10) and hepatitis B core‐related antigen (HBcrAg) serum levels as predictors of HBsAg loss, relapse and retreatment in noncirrhotic HBeAg‐negative CHB patients who discontinued long‐term antiviral therapy. All HBsAg‐positive (n = 57) patients of the prospective DARING‐B study were included and followed monthly for 3 months, every 2/3 months until month‐12 and every 3/6 months thereafter. HBsAg, IP10 and HBcrAg levels were measured by enzyme immunoassays, and SCALE‐B score was calculated. Twelve patients achieved HBsAg loss before retreatment with 18‐month cumulative incidence of 25%. Independent predictors of HBsAg loss were baseline HBsAg and month‐1 IP10 levels. Of 10 patients with baseline HBsAg ≤100 IU/mL, 70% cleared HBsAg and 10% required retreatment. Of 23 patients with baseline HBsAg >1000 IU/mL, 4% cleared HBsAg and 43% required retreatment. Of 24 patients with intermediate baseline HBsAg (100‐1000 IU/mL), 17% cleared HBsAg and 21% required retreatment; in this subgroup, month‐1 IP10 was significantly associated with HBsAg loss, which occurred in 30% and 7% of cases with IP10 >150 and ≤150 pg/mL, respectively. Baseline HBcrAg was undetectable in all patients who cleared HBsAg and was associated with retreatment. SCALE‐B was associated with HBsAg loss but not with relapse or retreatment. In conclusion, HBsAg, IP10 and HBcrAg serum levels can be useful for the decisions and management of treatment discontinuation in noncirrhotic Caucasian patients with HBeAg‐negative CHB.  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