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   1335篇
  免费   100篇
  国内免费   10篇
耳鼻咽喉   11篇
儿科学   20篇
妇产科学   50篇
基础医学   149篇
口腔科学   26篇
临床医学   156篇
内科学   365篇
皮肤病学   61篇
神经病学   103篇
特种医学   89篇
外科学   215篇
综合类   8篇
一般理论   1篇
预防医学   57篇
眼科学   13篇
药学   55篇
中国医学   2篇
肿瘤学   64篇
  2023年   4篇
  2022年   10篇
  2021年   34篇
  2020年   15篇
  2019年   28篇
  2018年   30篇
  2017年   26篇
  2016年   24篇
  2015年   28篇
  2014年   40篇
  2013年   60篇
  2012年   91篇
  2011年   82篇
  2010年   66篇
  2009年   67篇
  2008年   103篇
  2007年   101篇
  2006年   98篇
  2005年   103篇
  2004年   81篇
  2003年   69篇
  2002年   67篇
  2001年   38篇
  2000年   31篇
  1999年   27篇
  1998年   21篇
  1997年   13篇
  1996年   4篇
  1995年   11篇
  1994年   11篇
  1993年   2篇
  1991年   7篇
  1987年   3篇
  1984年   2篇
  1982年   2篇
  1980年   2篇
  1979年   3篇
  1975年   2篇
  1974年   4篇
  1973年   3篇
  1972年   3篇
  1970年   2篇
  1969年   2篇
  1965年   3篇
  1964年   1篇
  1963年   2篇
  1962年   3篇
  1961年   2篇
  1960年   1篇
  1959年   1篇
排序方式: 共有1445条查询结果,搜索用时 15 毫秒
1.
In Australia there is currently no consistent approach to collecting breast cancer specific data. The National Health Data Dictionary (NHDD) recommends a core set of generic data items for clinical cancer registration. However this list does not include the more detailed items required by specific tumour streams. The NBCC has developed a supplementary set of Breast Specific Data Items and definitions to serve as a guide for specialist breast cancer data collection in Australia. A multidisciplinary Working Group comprising clinical and consumer representation, including three breast surgeons, identified 16 breast specific data items for collection. The items are designed to align with items collected through the RACS National Breast Cancer Audit and leading cancer centres. A range of items from patient data (menopausal status), diagnostic data (HER2 status, sentinel lymph node), treatment (surgical margin clearance and involvement), and breast reconstruction are included. The data items are recommended as best practice for breast cancer specific data collection and aim to facilitate national consistency in defining, recording, and monitoring information about patients with breast cancer. This national approach will contribute to improved patient outcomes by informing planning, quality improvement and evaluation strategies for cancer services. The items are currently being piloted in two sites in NSW and will be available nationally in late 2007.  相似文献   
2.
Serum total IgE levels in a representative sample of a Greek population   总被引:1,自引:1,他引:1  
The distribution of IgE in a large randomly stratified Greek population sample was determined in 1187 subjects (793 men and 394 women) aged between 20 and 60 years. Skin prick testing was performed and serum total IgE expressed in iu/ml was measured by Phadebas PRIST: the data are presented as the geometric mean. Subjects were classified as atopic (257 men, 118 women) and nonatopic (536 men, 276 women) according to the results of skin testing with various aeroallergens. At any age, atopic males (120.5 vs 38 iu/ml) and females (99.8 vs 29.3 iu/ml) had higher mean IgE levels, as compared to nonatopic subjects ( P <0.0001). In our adult nonatopic sample, IgE levels did not differ with age ( P >0.05). At any age, nonatopic males had higher (38 iu/ml) mean IgE levels than nonatopic females (29.3 iu/ml) ( P <0.05). The comparison of normal IgE values (nonatopic subjects) from this study with those reported by other investigators revealed that Greek adult males and females had higher IgE levels than populations from other nations. Our results represent the first report on reference values regarding serum total IgE in Greek adults.  相似文献   
3.
Antibodies to tumor necrosis factor (TNF)-α have been recently proposed as effective treatment for patients with Crohn's disease. Here, we analyze the functional role of TNF-α in a mouse model of chronic intestinal inflammation induced by the hapten reagent 2,4,6,-trinitrobenzene sulfonic acid (TNBS) that mimics some characteristics of Crohn's disease in humans. Macrophage-enriched lamina propria (LP) mononuclear cells from mice with TNBS-induced colitis produced 10–30-fold higher levels of TNF-α mRNA and protein than cells from control mice. When mice with chronic colitis were treated by intraperitoneal injection of antibodies to TNF-α, an improvement of both the clinical and histopathologic signs of disease was found. Isolated macrophage-enriched LP cells from anti-TNF-α-treated mice produced strikingly less pro-inflammatory cytokines such as interleukin (IL)-1 and IL-6 in cell culture. The predominant role of TNF-α in the mouse TNBS-induced colitis model was further underlined by the finding that striking colonic inflammation and lethal pancolitis was induced in TNF-α-transgenic mice upon TNBS treatment. Conversely, no significant TNBS-induced colitis could be induced in mice in which the TNF-α gene had been inactivated by homologous recombination. Complementation of TNF-α function in TNF?/? mice by the expression of a mouse TNF-α transgene was sufficient to reverse this effect. Taken together, the data provide direct evidence for a predominant role of TNF-α in a mouse model of chronic intestinal inflammation and encourage further clinical trials with antibodies to TNF-α for the treatment of patients with Crohn's disease.  相似文献   
4.

The disposal of lignite spoil and tailings poses a major environmental problem in lignite mining sites which is associated with the oxidation of sulfide minerals contained in the primary ore. This process renders acidic effluents. Lignite mining in the Oropos Neogene basin, North Attica, Greece operated since the last century and ceased in the late 1960s. Piles of complex waste material are dispersed close to the mining sites. The high sulfur content and low Net Neutralization Potential, i.e. values < − 20 CaCO3 kg/t in most analyzed waste samples, indicate that the waste is prone to acid generation. The leachates (EN12457) from the lignite spoils showed high concentrations in Ni and Zn exceeding the EU regulatory limits for the non-hazardous wastes. GIS-based geochemical maps of the topsoil showed enrichment in Ni (Cr, V) associated with the regional geogenic enrichment but also local accumulation around the hot spot sites of lignite spoil heaps.

  相似文献   
5.
This study reports our experience with low-dose prostaglandin E1 (PGE1) treatment of 91 newborns with ductus dependent congenital heart disease (CHD). PGE1 efficacy, side-effects as well as the cardiovascular and respiratory profile of the patients were analysed. PGE1 doses > 0.02 g/kg per minute were used for only 5.3% of the total 23 656 h of treatment. The mean systolic blood pressures did not differ from the normal mean for patients with cyanotic CHD, while the diastolic values were lowered. Respiratory support was required only during 13.7% of the total treatment time. Apnoeas occurred in 21 (38%) of the 55 spontaneously breathing infants, who all had a cyanotic CHD. The incidence of apnoeas was lower during treatment with doses < 0.01 g/kg per minute.  相似文献   
6.
Alkadhi H  Kollias SS 《Neuroradiology》2000,42(10):753-755
The tick-borne encephalitis (TBE) virus gives rise to epidemic encephalitis. Mild forms usually manifest as influenza-like episodes or are clinically silent. MRI is usually normal in TBE. We describe severe TBE in a patient who presented with fever and altered mental status after a tick bite and a specific antibody response to TBE. MRI revealed pronounced signal abnormalities in the basal ganglia and thalamus, without contrast enhancement. These findings coincide well with neuropathological studies of severe nerve cell degeneration with inflammatory cell infiltrates, neuronophagia and reactive astrocytosis in the deep grey matter. We review the literature and discuss the relevant differential diagnosis. Received: 10 November 1999/Accepted: 4 February 2000  相似文献   
7.
BACKGROUND: Assessment of axillary lymph node status is necessary for patients with invasive breast cancer. Sentinel node biopsy is a new minimally invasive technique that may provide accurate assessment of regional lymph node status while limiting the morbidity associated with axillary clearance. METHODS: A workshop conducted in Adelaide in November 1998 aimed to assess current sentinel node mapping and biopsy techniques, and make recommendations regarding its application in the surgical management of early breast cancer in Australia and New Zealand. RESULTS: At the conclusion of the workshop, a consensus was reached regarding indications, exclusions, sentinel node mapping/biopsy technique, nuclear medicine requirements, pathology and safety of sentinel node biopsy in breast cancer. It was agreed that a feasibility study according to an agreed prospective protocol was necessary to validate the technique by breast surgeons. Surgeons that satisfied validation criteria for the feasibility study could then consider a prospective randomized study comparing sentinel node biopsy with standard axillary dissection. CONCLUSIONS: Sentinel node biopsy in breast cancer involves close cooperation between members of a multidisciplinary team including surgeons, nuclear physicians, pathologists and radiologists. Although the technique has the potential to reduce morbidity associated with axillary surgery, surgical performance in this area will need to be closely monitored to ensure that the technique does not fall into disrepute by adversely affecting breast cancer prognosis.  相似文献   
8.
In the current work, a novel complex concentrated aluminum alloy is designed and studied. In order to investigate the unknown region of the multicomponent phase diagrams, thermo-physical parameters and the CALPHAD method were used to understand the phase formation of the Al58Mg18Zn12Cu5Si7 at.% (Al47.4Mg13.3Zn23.8Cu9.6Si6wt.%) alloy with a low-density of 2.63 g/cm3. The CALPHAD methodology showed good agreement with both the investigated microstructure and the thermodynamic parameters. The designed alloy was manufactured using an induction furnace and pour mold casting process. This study avoids the use of expensive, dangerous or scarce alloying elements and focuses instead on the utilization of widely available relatively cheaper elements. The microstructural evolution as a function of the heat-treatment was studied by means of different microstructural characterization techniques. The hardness, compressive strength and electrical conductivity of the as-cast and heat-treated alloy at room temperature were studied and correlated with the previously characterized microstructure. The alloy is characterized by a multiphase microstructure with major α-Al matrix reinforced with various secondary phases. In terms of mechanical properties, the developed alloy exhibited a high hardness value of 249 Vickers and compressive strength of 588 MPa. The present work provides a valuable insight for researchers, who aim to design and produce industry-like Aluminum based complex concentrated alloys (CCAs).  相似文献   
9.
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   
10.
According to the established validation protocols, a typical validation study of a blood pressure (BP) monitor includes general population adults with normal or elevated BP. It is recognized, however, that the automated (oscillometric) BP monitors may have different accuracy or uses in some special populations compared with adults in the general population. Thus, an automated BP monitor with proven accuracy in a general population of adults may not be accurate in a special population, and therefore separate validation is needed. Recognized special populations deserving separate validation are those for which there is theoretical, and also clinical evidence, that the accuracy of BP monitors in these groups differs from that in the general population. Young children, pregnant women (including those with preeclampsia), individuals with arm circumference >42 cm, and patients with atrial fibrillation are regarded as special populations. Adolescents, individuals older than 80 years, and patients with end‐stage renal disease or diabetes mellitus have also been considered as possible special groups, but there is still inadequate evidence of altered accuracy of BP monitors in these subjects. Validation studies should be performed in special populations and evaluated separately after the BP‐measuring device has successfully undergone a validation study in a general population (unless the test device is intended only for a special population). This article discusses issues relating to the measurement of BP and the diagnosis of hypertension in selected special populations, as well as in low‐resource settings, where a simplified yet efficient evaluation strategy is necessary.  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