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   4887篇
  免费   233篇
  国内免费   22篇
耳鼻咽喉   40篇
儿科学   169篇
妇产科学   238篇
基础医学   554篇
口腔科学   144篇
临床医学   409篇
内科学   1138篇
皮肤病学   72篇
神经病学   332篇
特种医学   161篇
外科学   625篇
综合类   21篇
一般理论   2篇
预防医学   248篇
眼科学   33篇
药学   366篇
中国医学   11篇
肿瘤学   579篇
  2023年   21篇
  2022年   74篇
  2021年   126篇
  2020年   64篇
  2019年   104篇
  2018年   132篇
  2017年   88篇
  2016年   92篇
  2015年   110篇
  2014年   142篇
  2013年   195篇
  2012年   303篇
  2011年   301篇
  2010年   163篇
  2009年   129篇
  2008年   238篇
  2007年   254篇
  2006年   230篇
  2005年   264篇
  2004年   222篇
  2003年   255篇
  2002年   177篇
  2001年   123篇
  2000年   154篇
  1999年   143篇
  1998年   60篇
  1997年   34篇
  1996年   33篇
  1995年   31篇
  1994年   30篇
  1993年   26篇
  1992年   74篇
  1991年   78篇
  1990年   70篇
  1989年   64篇
  1988年   67篇
  1987年   68篇
  1986年   65篇
  1985年   61篇
  1984年   43篇
  1983年   42篇
  1982年   16篇
  1981年   19篇
  1980年   14篇
  1979年   30篇
  1978年   20篇
  1976年   9篇
  1975年   15篇
  1973年   13篇
  1972年   8篇
排序方式: 共有5142条查询结果,搜索用时 125 毫秒
81.
The levels of 2 arachidonic acid metabolites formed either by enzymatic activity of cyclooxygenase, i.e. prostaglandin E2 (PGE2), or by free radical-catalyzed peroxidation, i.e. F2-isoprostane 8-epi-prostaglandin F2alpha (8-epi-PGF2alpha), were measured in the CSF of subjects with sporadic and familial Creutzfeldt-Jakob disease (CJD) and in brain homogenates of scrapie-infected mice. The CSF levels of both metabolites were increased in sporadic CJD (n = 52) and familial CJD (n = 10) patients when compared with a group of patients with noninflammatory disorders. Similarly, PGE2 and 8-epi-PGF2alpha levels were higher in brain homogenates obtained from C57BL/6J mice infected with the ME7 scrapie strain than in brain homogenates from control animals. As PGE2 is 1 of the most abundant prostaglandins released during inflammation and 8-epi-PGF2alpha is a quantitative marker of lipid peroxidation, our results provide in vivo biochemical evidence for the occurrence of inflammation and oxidative stress in human and experimental transmissible spongiform encephalopathies (TSEs), a concept so far based mainly on histopathological and in vitro evidence. Interestingly, in sporadic CJD patients, high CSF levels of PGE2, but not 8-epi-PGF2alpha, correlated with short survival time, suggesting that the inflammatory response correlates with the clinical duration of disease.  相似文献   
82.
OBJECTIVE. We evaluated the extent to which hepatic lesion characterization and detection is improved by using gadobenate dimeglumine for enhancement of MR images. MATERIALS AND METHODS. Eighty-six patients were imaged before gadobenate dimeglumine administration, immediately after the 2 mL/sec bolus administration of a 0.05 mmol/kg dose (dynamic imaging), and at 60-120 min after the IV infusion at 10 mL/min of a further 0.05 nmol/kg dose (delayed imaging). The accuracy for lesion characterization was assessed for a total of 107 lesions. Sensitivity for lesion detection was assessed for a total of 149 lesions detected on either intra-operative sonography, iodized oil CT, CT during arterial portography, or follow-up contrast-enhanced CT as the gold standard. RESULTS. The accuracy in differentiating benign from malignant liver lesions increased from 75% and 82% (the findings of two observers) on unenhanced images alone, to 89% and 80% on dynamic images alone (p<0.001, p = 0.8), and to 90.7% when combining the unenhanced and dynamic image sets (p<0.001, p = 0.023). Delayed images did not further improve accuracy (90% and 91%; p = 0.002, p< 0.05). A similar trend was apparent in terms of accuracy for specific diagnosis: values ranged from 49% and 62% on unenhanced images alone, to 76% and 70% on combined unenhanced and dynamic images (p<0.001, p = 0.06), and to 75% and 70% on inclusion of delayed images (p<0.001, p = 0.12). The sensitivity for lesion detection increased from 77% and 81% on unenhanced images alone, to 87% and 85% on combined unenhanced and dynamic images (p = 0.001, p = 0.267), and to 92% and 89% when all images were considered (p<0.001, p = 0.01). CONCLUSION. Contrast-enhanced dynamic MR imaging with gadobenate dimeglumine significantly increases sensitivity and accuracy over unenhanced imaging for the characterization of focal hepatic lesions, and delayed MR imaging contributes to the improved detection of lesions.  相似文献   
83.
In the last 10 years, four patients with aneurysms of the supraaortic trunks and the internal carotid artery have been operated in emergency at Department of Vascular Surgery of University of Bari. The first case was a mycotic aneurysm of the carotid bifurcation, the second an aneurysm of internal carotid artery interesting the retropharynx, the third a post-operatory pseudoaneurysm of common carotid in a patient affected by Takayasu's disease and the last an atherosclerotic aneurysm of the innominate artery. Clinical picture suggested an immediate surgical treatment in all patients. Different procedure were used depending on size and localization of each lesion. Results in all cases have been satisfactory. The aneurysms of supraaortic trunks and of internal carotid artery are very rare; therefore when clinical picture is dramatic or quickly worsening, emergency treatment is mandatory in order to reduce mortality risk and minimize complications.  相似文献   
84.
85.
Xerophilic fungal species of the genus Aspergillus are economically highly relevant due to their ability to grow on low water activity substrates causing spoilage of stored goods and animal feeds. These fungi can synthesize a variety of secondary metabolites, many of which show animal toxicity, creating a health risk for food production animals and to humans as final consumers, respectively. Animal feeds used for rabbit, chinchilla and rainbow trout production in Argentina were analysed for the presence of xerophilic Aspergillus section Aspergillus species. High isolation frequencies (>60%) were detected in all the studied rabbit and chinchilla feeds, while the rainbow trout feeds showed lower fungal charge (25%). These section Aspergillus contaminations comprised predominantly five taxa. Twenty isolates were subjected to taxonomic characterization using both ascospore SEM micromorphology and two independent DNA loci sequencing. The secondary metabolite profiles of the isolates were determined qualitatively by HPLC-MS. All the isolates produced neoechinulin A, 17 isolates were positive for cladosporin and echinulin, and 18 were positive for neoechinulin B. Physcion and preechinulin were detected in a minor proportion of the isolates. This is the first report describing the detailed species composition and the secondary metabolite profiles of Aspergillus section Aspergillus contaminating animal feeds.  相似文献   
86.
This work is aimed to present an innovative technology for the reinforcement of beams for urban furniture, produced by in-mold extrusion of plastics from solid urban waste. This material, which is usually referred to as “recycled plastic lumber”, is characterized by very poor mechanical properties, which results in high deflections under flexural loads, particularly under creep conditions. The Prowaste project, founded by the EACI (European Agency for Competitiveness and Innovation) in the framework of the Eco-Innovation measure, was finalized to develop an innovative technology for selective reinforcement of recycled plastic lumber. Selective reinforcement was carried out by the addition of pultruded glass rods in specific positions with respect to the cross section of the beam, which allowed optimizing the reinforcing efficiency. The reinforcement of the plastic lumber beams with pultruded rods was tested at industrial scale plant, at Solteco SL (Alfaro, Spain). The beams obtained, characterized by low cost and weight, were commercialized by the Spanish company. The present paper presents the most relevant results of the Prowaste project. Initially, an evaluation of the different materials candidates for the reinforcement of recycled plastic lumber is presented. Plastic lumber beams produced in the industrial plant were characterized in terms of flexural properties. The results obtained are interpreted by means of beam theory, which allows for extrapolation of the characteristic features of beams produced by different reinforcing elements. Finally, a theoretical comparison with other approaches which can be used for the reinforcement of plastic lumber is presented, highlighting that, among others, the Prowaste concept maximizes the stiffening efficiency, allowing to significantly reduce the weight of the components.  相似文献   
87.
88.
ObjectivesThe objective of our study was to review our current knowledge of the aetiopathogenesis of Cogan's syndrome, including viral infection and autoimmunity, and to discuss disease pathogenesis with relevance to pharmacotherapy.Systematic review methodologyRelevant publications on the aetiopathogenesis and pharmacotherapy of Cogan's syndrome from 1945 to 2012 were analysed.Results and conclusionsCogan's syndrome is a rare autoimmune vasculitis, and its pathogenesis is unknown. Infection, but primarily autoimmunity, may play contributing roles in the pathogenesis of this disease. It is characterised by ocular and audiovestibular symptoms similar to those of Meniere's syndrome. Approximately 70% of patients have systemic disease, of which vasculitis is considered the pathological mechanism. The immunologic theory is based on the release of auto-antibodies against corneal, inner ear and endothelial antigens, and of anti-nuclear cytoplasmic auto-antibodies (ANCA).Corticosteroids are the first line of treatment, and multiple immunosuppressive drugs have been tried with varying degrees of success. Tumour necrosis factor (TNF)-alpha blockers are a category of immunosuppressive agents representing a recent novel therapeutic option in Cogan's syndrome.  相似文献   
89.
90.
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