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   4973篇
  免费   306篇
  国内免费   15篇
耳鼻咽喉   87篇
儿科学   122篇
妇产科学   78篇
基础医学   672篇
口腔科学   346篇
临床医学   373篇
内科学   1052篇
皮肤病学   92篇
神经病学   422篇
特种医学   103篇
外科学   605篇
综合类   25篇
一般理论   2篇
预防医学   591篇
眼科学   137篇
药学   333篇
中国医学   45篇
肿瘤学   209篇
  2023年   38篇
  2022年   73篇
  2021年   209篇
  2020年   111篇
  2019年   155篇
  2018年   199篇
  2017年   125篇
  2016年   108篇
  2015年   156篇
  2014年   221篇
  2013年   270篇
  2012年   413篇
  2011年   438篇
  2010年   226篇
  2009年   190篇
  2008年   282篇
  2007年   315篇
  2006年   239篇
  2005年   260篇
  2004年   233篇
  2003年   212篇
  2002年   161篇
  2001年   81篇
  2000年   75篇
  1999年   73篇
  1998年   34篇
  1997年   20篇
  1996年   24篇
  1995年   14篇
  1994年   11篇
  1993年   18篇
  1992年   28篇
  1991年   28篇
  1990年   17篇
  1989年   37篇
  1988年   26篇
  1987年   28篇
  1986年   17篇
  1985年   28篇
  1984年   15篇
  1983年   7篇
  1981年   5篇
  1980年   7篇
  1973年   8篇
  1972年   4篇
  1971年   6篇
  1970年   4篇
  1969年   5篇
  1968年   5篇
  1967年   7篇
排序方式: 共有5294条查询结果,搜索用时 15 毫秒
81.
We evaluated the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) protocols on the alterations in oxidative stress parameters caused by a high-fat diet (HFD), in the blood and liver of rats. The HFD enhanced thiobarbituric acid reactive substances (TBA-RS) and protein carbonyl content, while reducing total sulfhydryl content and catalase (CAT) and glutathione peroxidase (GSH-Px) activities in the blood. Both training protocols prevented an increase in TBA-RS and protein carbonyl content, and prevented a reduction in CAT. HIIT protocol enhanced SOD activity. In the liver, HFD didn’t alter TBA-RS, total sulfhydryl content or SOD, but increased protein carbonyl content and CAT and decreased GSH-Px. The exercise protocols prevented the increase in protein carbonyl content and the MICT protocol prevented an alteration in CAT. In conclusion, HFD elicits oxidative stress in the blood and liver and both protocols prevented most of the alterations in the oxidative stress parameters.  相似文献   
82.
Metals are released into freshwater ecosystems from natural and anthropogenic sources, compromising their structural and functional equilibrium. As early warning tools, cholinesterases (ChEs) are usually used to assess the effects of organophosphate and carbamate pesticides, but are also known to be inhibited by metals. The objectives of this work were to characterise the activity of ChE present in the amphipod Echinogammarus meridionalis and the shrimp Atyaephyra desmarestii and to evaluate the in vivo effects of the metals copper and zinc in their ChE activity. To achieve this, firstly the activity of ChE forms were characterised using different in vitro assays with substrates and selective inhibitors. Then, the in vivo effects of 48 h exposures to increasing concentrations of copper and zinc on ChE activity were determined. The ChE form present in both species was acetylcholinesterase (AChE) since both revealed preference for the acetylthiocholine iodide substrate, total inhibition with eserine, the inhibitor of ChEs, and with 1,5-bis(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide, the specific inhibitor of AChE, and presented insensitivity to iso-OMPA, a specific inhibitor of butyrylcholinesterase. The activity of ChEs was inhibited by zinc exposures in the amphipod species, but was not affected by copper. Exposure to copper and zinc did not affect ChEs activity in the shrimp at the concentrations tested. This work is a relevant contribution as foundation for the use of AChE in freshwater crustaceans in further studies including biomonitoring campaigns in different contamination scenarios.  相似文献   
83.
84.
85.
Ameloblastoma is a locally aggressive neoplasm with a poorly understood pathogenesis. Therefore, the aim of this study is to investigate whether COX-2 expression is associated with ameloblastoma microvascular density (MVD) and with tumor aggressiveness. Sixty-three cases of primary ameloblastomas arranged in tissue microarray were submitted to immunohistochemistry against cyclooxigenase-2 (COX-2) and CD34. Clinicopathological parameters regarding sex, age, tumour size, tumour duration, tumour location, treatment, recurrences, radiographic features, vestibular/lingual and basal cortical disruption and follow-up data were obtained from patients’ medical records and correlated with the proteins expression. The results on BRAF-V600E expression were obtained from our previous study and correlated with COX-2 and CD34 expressions. Log-rank univariate analysis and multivariate Cox regression model were done to investigate the prognostic potential of the molecular markers. Twenty-eight cases (44.4%) exhibited cytoplasmic positivity for COX-2, predominantly in the columnar peripheral cells, with a mean MVD of 2.2 vessels/mm2. COX-2 was significantly associated with recurrences (p?<?0.001) and BRAF-V600E expression (p?<?0.001), whereas lower MVD was associated with the use of conservative therapy (p?=?0.004). Using univariate and multivariate analyses, COX-2 was significantly associated with a lower 5-year disease-free survival (DFS) rate (p?<?0.001 and p?=?0.012, respectively), but not with a higher MVD (p?=?0.68). In conclusion, COX-2 expression in ameloblastomas is not associated with MVD, but it is significantly associated with recurrences and with a lower DFS.  相似文献   
86.
87.
88.
In the present work we investigated the effect of ovariectomy on acetylcholinesterase (AChE) activity and ganglioside content in cerebral cortex of female rats. We also studied the activity of butyrylcholinesterase (BuChE) in serum of these animals. Adult Wistar rats were divided into three groups: (1) naive females (control), (2) sham-operated females and (3) castrated females (ovariectomy). Thirty days after ovariectomy, rats were sacrificed by decapitation without anaesthesia. Blood was collected and the serum used for BuChE determination. Cerebral cortex was homogenized to determine AChE activity and extracted with chlorophorm:methanol for ganglioside evaluation. Results showed that rats subjected to ovariectomy presented a significant increase of AChE activity, but did not change the content and the profile of gangliosides in cerebral cortex when compared to sham or naive rats. BuChE activity was decreased in serum of rats ovariectomized. Our findings suggest that the alteration in the activity of brain AChE, as well as serum BuChE activity caused by ovariectomy may contribute to the impaired cognition and/or other neurological dysfunction found in post-menopausal women.  相似文献   
89.
90.
Rhinoentomophthoramycosis caused by Conidiobolus coronatus in a 61-year old woman was unsuccessfully treated during 8 years with all the antifungals available in the Brazilian market, including potassium iodide for 1 month, sulfamethoxazole plus trimethoprim for 2 months, amphotericin B, total dose of 1130 mg, cetoconazole, 400 mg/day for 6 months, fluconazole, 200 mg/day, for at least 2 months and, itraconazole, 400 mg/day for 2 months, followed by 200 mg/day for 4 more months. Complete clinical and mycological cure was achieved using itraconazol 400 mg/day in association with fluconazol 200 mg/day during 24 months. After cure she was submitted to plastic surgery to repair her facial deformation. Today she remains clinically and mycologically cured after 59/60 months (5 years!) without any specific antifungal. We thus suggest the use of the combination of itraconazole and fluconazole as an additional option for the treatment of this mycosis.  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