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   1138篇
  免费   93篇
  国内免费   3篇
耳鼻咽喉   5篇
儿科学   34篇
妇产科学   26篇
基础医学   153篇
口腔科学   27篇
临床医学   129篇
内科学   231篇
皮肤病学   14篇
神经病学   48篇
特种医学   97篇
外科学   82篇
综合类   51篇
预防医学   108篇
眼科学   8篇
药学   71篇
中国医学   8篇
肿瘤学   142篇
  2023年   9篇
  2022年   11篇
  2021年   25篇
  2020年   13篇
  2019年   13篇
  2018年   54篇
  2017年   33篇
  2016年   16篇
  2015年   26篇
  2014年   36篇
  2013年   49篇
  2012年   53篇
  2011年   47篇
  2010年   36篇
  2009年   39篇
  2008年   47篇
  2007年   41篇
  2006年   61篇
  2005年   43篇
  2004年   41篇
  2003年   34篇
  2002年   43篇
  2001年   20篇
  2000年   32篇
  1999年   33篇
  1998年   23篇
  1997年   28篇
  1996年   16篇
  1995年   16篇
  1994年   12篇
  1993年   17篇
  1992年   24篇
  1991年   34篇
  1990年   18篇
  1989年   16篇
  1988年   13篇
  1987年   18篇
  1986年   16篇
  1985年   12篇
  1984年   14篇
  1983年   15篇
  1982年   7篇
  1981年   9篇
  1978年   5篇
  1975年   6篇
  1974年   5篇
  1970年   4篇
  1969年   5篇
  1968年   6篇
  1967年   5篇
排序方式: 共有1234条查询结果,搜索用时 31 毫秒
991.
Objective : Allergic rhinitis and allergic asthma are important chronic diseases posing serious public health issues in Australia with associated medical, economic, and societal burdens. Pollen are significant sources of clinically relevant outdoor aeroallergens, recognised as both a major trigger for, and cause of, allergic respiratory diseases. This study aimed to provide a national, and indeed international, perspective on the state of Australian pollen data using a large representative sample. Methods : Atmospheric grass pollen concentration is examined over a number of years within the period 1995 to 2013 for Brisbane, Canberra, Darwin, Hobart, Melbourne, and Sydney, including determination of the ‘clinical’ grass pollen season and grass pollen peak. Results : The results of this study describe, for the first time, a striking spatial and temporal variability in grass pollen seasons in Australia, with important implications for clinicians and public health professionals, and the Australian grass pollen‐allergic community. Conclusions : These results demonstrate that static pollen calendars are of limited utility and in some cases misleading. This study also highlights significant deficiencies and limitations in the existing Australian pollen monitoring and data. Implications : Establishment of an Australian national pollen monitoring network would help facilitate advances in the clinical and public health management of the millions of Australians with asthma and allergic rhinitis.  相似文献   
992.
Successful species develop strategies to optimize their reproductive performance. This optimization likely includes the evolution of genes that specifically permit reproduction in physiologically challenging conditions. The prolactin (PRL) family gene cluster is one of 25 mouse-specific gene clusters, the majority of which are associated with reproduction. A prevailing theme characterizing the PRL family is its connection with pregnancy and mechanisms controlling viviparity. PRL-like protein A (PLP-A) is one of 26 genes located within the PRL family locus. It is a nonclassical member of the PRL family (e.g., PLP-A does not use the PRL receptor) produced by trophoblast cells of the chorioallantoic placenta and acts on uterine natural killer cells. In this report, the biology of PLP-A has been investigated by generating mice with a PLP-A null mutation. Under standardized animal husbandry conditions, PLP-A possesses modest effects on reproductive performance. However, this same gene is critical for reproduction when mice are exposed to a physiological stressor. Wild-type mice exposed to hypobaric hypoxia during gestation readily adapt and maintain their pregnancies, whereas PLP-A null mutant mice fail to adapt, resulting in pregnancy failure. PLP-A contributes to hypoxia-induced adaptations critical to hemochorial placentation and thus nutrient flow to extraembryonic and embryonic tissues. The findings provide insights into species-specific reproductive adaptations.  相似文献   
993.
994.

Background

Diabetes mellitus is a leading cause of morbidity and mortality worldwide. Studies have shown that Zinc has numerous beneficial effects in both type-1 and type-2 diabetes. We aim to evaluate the literature on the mechanisms and molecular level effects of Zinc on glycaemic control, β-cell function, pathogenesis of diabetes and its complications.

Methods

A review of published studies reporting mechanisms of action of Zinc in diabetes was undertaken in PubMed and SciVerse Scopus medical databases using the following search terms in article title, abstract or keywords; (“Zinc” or “Zn”) and (“mechanism” or “mechanism of action” or “action” or “effect” or “pathogenesis” or “pathology” or “physiology” or “metabolism”) and (“diabetes” or “prediabetes” or “sugar” or “glucose” or “insulin”).

Results

The literature search identified the following number of articles in the two databases; PubMed (n = 1799) and SciVerse Scopus (n = 1879). After removing duplicates the total number of articles included in the present review is 111. Our results show that Zinc plays an important role in β-cell function, insulin action, glucose homeostasis and the pathogenesis of diabetes and its complications.

Conclusion

Numerous in-vitro and in-vivo studies have shown that Zinc has beneficial effects in both type-1 and type-2 diabetes. However further randomized double-blinded placebo-controlled clinical trials conducted for an adequate duration, are required to establish therapeutic safety in humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s40199-015-0127-4) contains supplementary material, which is available to authorized users.  相似文献   
995.
Ascorbic acid in the human stomach   总被引:13,自引:0,他引:13  
Ascorbic acid, the reduced form of vitamin C, may protect against gastric cancer. Accordingly, this study assessed the variability of ascorbic acid and vitamin C in the gastric juice of 77 patients with dyspepsia. There was a vitamin C concentration gradient from gastric juice down to plasma in subjects with normal gastric mucosa, but not in those with chronic gastritis. Patients with chronic gastritis had significantly lower gastric concentrations of vitamin C and ascorbic acid, and ascorbic acid concentrations were especially low in subjects with hypochlorhydria. The presence of the concentration gradient suggests that a mechanism for the secretion of vitamin C into the stomach exists. This is compromised by chronic gastritis. The very low ascorbic acid concentrations in hypochlorhydria may be a consequence of oxidation by bacterial nitrite. Those patients who by the Correa model are at greatest risk for gastric cancer have the lowest gastric levels of ascorbic acid.  相似文献   
996.
The ability to use a vital cell marker to study mouse embryogenesis will open new avenues of experimental research. Recently, the use of transgenic mice, containing multiple copies of the jellyfish gene encoding the green fluorescent protein (GFP), has begun to realize this potential. Here, we show that the fluorescent signals produced by single-copy, targeted GFP in-frame fusions with two different murine Hox genes, Hoxa1 and Hoxc13, are readily detectable by using confocal microscopy. Since Hoxa1 is expressed early and Hoxc13 is expressed late in mouse embryogenesis, this study shows that single-copy GFP gene fusions can be used through most of mouse embryogenesis. Previously, targeted lacZ gene fusions have been very useful for analyzing mouse mutants. Use of GFP gene fusions extends the benefits of targeted lacZ gene fusions by providing the additional utility of a vital marker. Our analysis of the Hoxc13GFPneo embryos reveals GFP expression in each of the sites expected from analysis of Hoxc13lacZneo embryos. Similarly, Hoxa1GFPneo expression was detected in all of the sites predicted from RNA in situ analysis. GFP expression in the foregut pocket of Hoxa1GFPneo embryos suggests a role for Hoxa1 in foregut-mediated differentiation of the cardiogenic mesoderm.  相似文献   
997.
In an attempt to preserve proximal femoral bone stock and achieve a better fit in smaller femora, especially in the Asian population, several new shorter stem designs have become available. We investigated the torque to periprosthetic femoral fracture of the Exeter short stem compared with the conventional length Exeter stem in a Sawbone model. Forty-two stems; 21 shorter and 21 conventional stems both with three different offsets were cemented in a composite Sawbone model and torqued to fracture. Results showed that Sawbone femurs break at a statistically significantly lower torque to failure with a shorter compared to conventional-length Exeter stem of the same offset. Both standard and short-stem designs are safe to use as the torque to failure is 7–10 times that seen in activities of daily living.  相似文献   
998.
999.
CardioVascular and Interventional Radiology - Obesity is a worldwide public health epidemic that leads to increased morbidity, mortality, and cost burden to health care. Although bariatric surgery...  相似文献   
1000.

Purpose

The role of T2*-based MR imaging in intracranial germ cell tumors (GCTs) has not been fully elucidated. The aim of this study was to evaluate the susceptibility-weighted imaging (SWI) or T2* gradient echo (GRE) features of germinomas and non-germinomatous germ cell tumors (NGGCTs) in midline and off-midline locations.

Methods

We retrospectively evaluated all consecutive pediatric patients referred to our institution between 2005 and 2016, for newly diagnosed, treatment-naïve intracranial GCT, who underwent MRI, including T2*-based MR imaging (T2* GRE sequences or SWI). Standard pre- and post-contrast T1- and T2-weighted imaging characteristics along with T2*-based MR imaging features of all lesions were evaluated. Diagnosis was performed in accordance with the SIOP CNS GCT protocol criteria.

Results

Twenty-four subjects met the inclusion criteria (17 males and 7 females). There were 17 patients with germinomas, including 5 basal ganglia primaries, and 7 patients with secreting NGGCT.All off-midline germinomas presented with SWI or GRE hypointensity; among midline GCT, all NGGCTs showed SWI or GRE hypointensity whereas all but one pure germinoma were isointense or hyperintense to normal parenchyma. A significant difference emerged on T2*-based MR imaging among midline germinomas, NGGCTs, and off-midline germinomas (p?<?0.001).

Conclusion

Assessment of the SWI or GRE characteristics of intracranial GCT may potentially assist in differentiating pure germinomas from NGGCT and in the characterization of basal ganglia involvement. T2*-based MR imaging is recommended in case of suspected intracranial GCT.
  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