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   601篇
  免费   50篇
耳鼻咽喉   19篇
儿科学   9篇
妇产科学   11篇
基础医学   100篇
口腔科学   21篇
临床医学   39篇
内科学   87篇
皮肤病学   9篇
神经病学   14篇
特种医学   11篇
外科学   65篇
综合类   11篇
一般理论   1篇
预防医学   17篇
眼科学   7篇
药学   42篇
中国医学   2篇
肿瘤学   186篇
  2024年   1篇
  2023年   10篇
  2022年   13篇
  2021年   20篇
  2020年   16篇
  2019年   18篇
  2018年   26篇
  2017年   21篇
  2016年   25篇
  2015年   25篇
  2014年   45篇
  2013年   42篇
  2012年   55篇
  2011年   44篇
  2010年   23篇
  2009年   23篇
  2008年   43篇
  2007年   23篇
  2006年   21篇
  2005年   27篇
  2004年   20篇
  2003年   19篇
  2002年   18篇
  2001年   7篇
  2000年   8篇
  1999年   9篇
  1998年   5篇
  1997年   1篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1993年   4篇
  1992年   1篇
  1990年   5篇
  1989年   3篇
  1987年   1篇
  1986年   1篇
  1985年   3篇
  1983年   2篇
  1980年   2篇
  1979年   2篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   3篇
  1971年   4篇
  1969年   1篇
  1968年   2篇
  1966年   1篇
排序方式: 共有651条查询结果,搜索用时 15 毫秒
11.
The mosquitocidal activity of different fractions and isolated compounds from the ethyl acetate extract of Ecbolium viride root was assessed on larvae and pupae of Culex quinquefasciatus Say (Diptera: Culicidae). The larvae and pupae were exposed to concentrations of 6.125, 12.5, 25 and 50 ppm for fractions and 1, 2.5, 5 and 10 ppm for compound. Among the 12 fractions screened, fraction 6 from the ethyl acetate extract of E. viride was recorded to have the highest larvicidal and pupicidal activities against C. quinquefasciatus. The lethal concentration (LC50 and LC90) values of fraction 6 were 4.26 and 9.0 ppm against C. quinquefasciatus larvae and 6.55 and 12.19 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Fraction 7 was recorded to have moderate activity with LC50 and LC90 values of 11.25 and 25.02 ppm against C. quinquefasciatus larvae and 13.33 and 31.15 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Ecbolin A and ecbolin B were identified from fractions 7 and 6, respectively. The structure of the isolated compounds was identified on the basis of spectral data (1H NMR and 13C NMR) and compared with literature spectral data. Further, the isolated compound, ecbolin B, from fraction 6 was recorded to have strong larvicidal and pupicidal activities than ecbolin A. The LC50 and LC90 values of ecbolin B on C. quinquefasciatus larvae were 1.36 and 2.76 ppm, and on pupae, these were 1.54 and 3.51 ppm, respectively. The present results suggest that ecbolin B could be used as a mosquitocidal agent against C. quinquefasciatus.  相似文献   
12.
13.

Introduction and hypothesis

To determine if the classification of obstetric anal sphincter injuries (OASIs) affected clinical and functional outcome and to assess the need for follow-up of 3a tears in secondary care

Methods

Prospective data collection in 255 patients who sustained OASIs during repair with follow-up in a specialist clinic after 6 months.

Results

One hundred and thirty-two patients (51.7 %) sustained 3a tears, 81 (31.7 %) 3b tears, 27 (10.6 %) 3c tears and 15 (5.8 %) had 4th degree tears. Twenty-three patients (9 %) reported symptoms at 6-month follow-up. Eight patients reported anal incontinence of liquid or solid stool. Among patients who sustained 3a tears, 8 patients were symptomatic: 7 had urgency and 1 had flatus incontinence. None of the patients who sustained 3a tears reported incontinence of solid/liquid stool. There appears to be no correlation with scan findings and symptoms at follow up. Most patients are asymptomatic. Urgency of faeces is the commonest symptom.

Conclusions

The vast majority of patients are asymptomatic. The necessity of seeing all these patients in secondary care for follow-up needs to be questioned. With effective primary care follow-up, there may be a place to follow up patients with 3a tears in the community during the routine 6-week postnatal check and refer the symptomatic patients to the hospital for further review.  相似文献   
14.
Mimicking porous topography of natural extracellular matrix is advantageous for successful regeneration of damaged tissues or organs. Nanotechnology being one of the most promising and growing technology today shows an extremely huge potential in the field of tissue engineering. Nanofibrous structures that mimic the native extracellular matrix and promote the adhesion of various cells are being developed as tissue‐engineered scaffolds for skin, bone, vasculature, heart, cornea, nervous system, and other tissues. A range of novel biocomposite materials has been developed to enhance the bioactive or therapeutic properties of these nanofibrous scaffolds via surface modifications, including the immobilization of functional cell‐adhesive ligands and bioactive molecules such as drugs, enzymes, and cytokines. In skin tissue engineering, usage of allogeneic skin is avoided to reestablish physiological continuity and also to address the challenge of curing acute and chronic wounds, which remains as the area of exploration with various biomimetic approaches. Two‐dimensional, three‐dimensional scaffolds and stem cells are presently used as dermal regeneration templates for the treatment of full‐thickness skin defects resulting from injuries and severe burns. The present review elaborates specifically on the fabrication of nanofibrous structured strategies for wound dressings, wound healing, and controlled release of growth factors for skin tissue regeneration.  相似文献   
15.

Background:

Oxidative stress has been implicated in various disorders including epilepsy. We studied the antioxidant status in patients with epilepsy and aimed at determining whether there was any difference in the antioxidant levels between patients and controls, patients who are not on antiepileptic drugs (AEDs), and on treatment, between individual AEDs and patients on monotherapy and polytherapy.

Materials and Methods:

Antioxidant levels like catalase, glutathione peroxidase (GPx), vitamin E, glutathione (GSH), thiol group (SH), uric acid, and total antioxidant capacity (TAC) were compared between 100 patients with epilepsy and equal number of controls. Twenty-five patients who were not on AEDs were compared with patients on AEDs and the control group. Patients were divided into monotherapy and polytherapy group and antioxidant status was compared between the two groups and between individual drugs.

Results:

Catalase, SH, vitamin E, and TAC were significantly low in patients with epilepsy than those in the control group (P < 0.001). GSH and uric acid did not show any difference; GPx in patients was significantly higher than those in the control group There were no differences in the antioxidant levels between the treated and the untreated groups; however, it was lower in untreated patients than controls (P < 0.001), suggesting that AEDs do not modify the oxidative stress. Patients on Valproate (VPA) showed higher catalase and GPx levels. Catalase was higher in the monotherapy than polytherapy group (P < 0.04).

Conclusion:

Our study found significantly low levels of antioxidant in patients as compared to controls. AED did not influence the antioxidant status suggesting that seizures induce oxidative stress.  相似文献   
16.
Conclusion: Cochlear implant electrode position has an impact on the rate of tinnitus suppression and generation. Objective: Suppression of pre-operative tinnitus or a generation of a new tinnitus in cochlear implantees is a known effect of cochlear implantation. The aim of the current study was to evaluate different cochlear implant electrode positions and their relationship with tinnitus suppression and tinnitus generation. Method: This study retrospectively evaluated four groups of CI recipients with radiologically evaluated electrode positions in relation to their subjective tinnitus quality, as evaluated by an analogue loudness scale (ALS) and a questionnaire. Group 1 consisted of 19 patients with a scalar change of the electrode position. Group 2 consisted of 18 patients with a scala tympani position and a perimodiolar electrode. Group 3 consisted of 10 patients with a scala tympani position and a lateral wall electrode. Group 4 consisted of eight patients with a scala vestibuli position. Results: An overall tinnitus suppression rate of 45.9% and a generation of a new tinnitus or the deterioration of an existing one of 5.6% were observed. A significant difference in tinnitus suppression was found between groups 1 and groups 2, 3, and 4 in tinnitus suppression and tinnitus generation.  相似文献   
17.
18.
Insulin, a pancreatic hormone, is best known for its peripheral effects on the metabolism of glucose, fats and proteins. There is a growing body of evidence linking insulin action in the brain to neurodegenerative diseases. Insulin present in central nervous system is a regulator of central glucose metabolism nevertheless this glucoregulation is not the main function of insulin in the brain. Brain is known to be specifically vulnerable to oxidative products relative to other organs and altered brain insulin signaling may cause or promote neurodegenerative diseases which invalidates and reduces the quality of life. Insulin located within the brain is mostly of pancreatic origin or is produced in the brain itself crosses the blood-brain barrier and enters the brain via a receptor-mediated active transport system. Brain Insulin, insulin receptor and insulin receptor substrate-mediated signaling pathways play important roles in the regulation of peripheral metabolism, feeding behavior, memory and maintenance of neural functions such as neuronal growth and differentiation, neuromodulation and neuroprotection. In the present review, we would like to summarize the novel biological and pathophysiological roles of neuronal insulin in neurodegenerative diseases and describe the main signaling pathways in use for therapeutic strategies in the use of insulin to the cerebral tissues and their biological applications to neurodegenerative diseases.  相似文献   
19.
Bronchogenic carcinoma, the commonest lung tumor occurs more frequently in the elderly with typical symptoms of cough, haemoptysis, weight loss, dyspnoea or chest pain. These symptoms mimic common respiratory infections in en-demic areas like pulmonary tuberculosis. Also, metastasis at presentation itself is common, the favoured sites being liver, contra-lateral lungs, bones, brain, etc., although unusual and rare sites like heart also are known. We herein report a rare association of both carcinoma with active pulmonary tuberculosis in the same lobe associated with intracardiac metastasis. Very few cases have been published describing lung carcinoma with intracardiac metastasis. We hope the documentation of this rare case will shed further light into the subject area and improve clinical education.  相似文献   
20.
Though a century old hypothesis, infection as a cause for atherosclerosis is still a debatable issue. Epidemiological and clinical studies had shown a possible association but inhomogeneity in the study population and study methods along with potential confounders have yielded conflicting results. Infection triggers a chronic inflammatory state which along with other mechanisms such as dyslipidemia, hyper-homocysteinemia, hypercoagulability, impaired glucose metabolism and endothelial dysfunction, contribute in pathogenesis of atherosclerosis. Studies have shown a positive relations between Cytotoxic associated gene-A positive strains of Helicobacter pylori and vascular diseases such as coronary artery disease and stroke. Infection mediated genetic modulation is a new emerging theory in this regard. Further large scale studies on infection and atherosclerosis focusing on multiple pathogenetic mechanisms may help in refining our knowledge in this aspect.  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