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   195468篇
  免费   4134篇
  国内免费   461篇
耳鼻咽喉   2781篇
儿科学   7513篇
妇产科学   5974篇
基础医学   25168篇
口腔科学   5859篇
临床医学   15200篇
内科学   35075篇
皮肤病学   4559篇
神经病学   11543篇
特种医学   10674篇
外国民族医学   99篇
外科学   29441篇
综合类   1148篇
一般理论   4篇
预防医学   16371篇
眼科学   4349篇
药学   13675篇
  2篇
中国医学   155篇
肿瘤学   10473篇
  2018年   3652篇
  2017年   3945篇
  2016年   3252篇
  2015年   4915篇
  2014年   4335篇
  2013年   3492篇
  2012年   9907篇
  2011年   4820篇
  2010年   2241篇
  2009年   3867篇
  2008年   2079篇
  2007年   2753篇
  2006年   3016篇
  2005年   11107篇
  2004年   12605篇
  2003年   8173篇
  2002年   3392篇
  2001年   4337篇
  2000年   1682篇
  1999年   5830篇
  1998年   520篇
  1995年   375篇
  1992年   6865篇
  1991年   7111篇
  1990年   7352篇
  1989年   6947篇
  1988年   6472篇
  1987年   6241篇
  1986年   5951篇
  1985年   5250篇
  1984年   3607篇
  1983年   2919篇
  1982年   1009篇
  1981年   774篇
  1980年   840篇
  1979年   3833篇
  1978年   2367篇
  1977年   1784篇
  1976年   1570篇
  1975年   2476篇
  1974年   3111篇
  1973年   2742篇
  1972年   2761篇
  1971年   2743篇
  1970年   2558篇
  1969年   2466篇
  1968年   2238篇
  1967年   2166篇
  1966年   1903篇
  1965年   1133篇
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
1.
The aim of this safety study in mice was to determine in vivo toxicity and biodistribution potential of a single and multiple doses of L-glutamic acid-g-p(HEMA) polymeric nanoparticles as a drug delivery system. The single dose did not cause any lethal effect, and its acute oral LD50 was >2.000 mg/kg body weight (bw). Multiple doses (25, 50, or 100 mg/kg bw) given over 28 days resulted in no significant differences in body and relative organ weights compared to control. These results are supported by biochemical and histological findings. Moreover, nanoparticle exposure did not result in statistically significant differences in micronucleus counts in bone marrow cells compared to control. Nanoparticle distribution was time-dependent, and they reached the organs and even bone marrow by hour 6, as established by ex vivo imaging with the IVIS® spectrum imaging system. In conclusion, L-glutamic acid-g-p(HEMA) polymeric nanoparticles appear biocompatible and have a potential use as a drug delivery system.KEY WORDS: biocompatibility, blood biochemistry, genotoxicity, histology, in vivo toxicity, micronucleus test, polymers  相似文献   
2.
3.
4.
5.
Introduction: Diabetes mellitus (DM) affects many patients all over the world. It involves different parts of the body, such as brain, eyes, kidneys, vessels, and so on. The lack of balance between free radicals and antioxidants is a possible mechanism involved in the pathogenesis of diabetes. Antioxidant treatment, especially natural forms, can be a beneficial solution. Therefore, we evaluated the effects of Pistacia atlantica oleoresin (PAO) on oxidative stress markers and antioxidant enzymes expression in diabetic rats.

Method: Fifty adult male Wistar rats were allotted randomly into five groups as follow: control group, diabetic control group, glibenclamide control group, diabetic glibenclamide group, diabetic treated group with 200?mg/kg PAO. Then PAO was prepared and analyzed by gas chromatography/mass spectroscopy (GC/MS). LD50 was also estimated for essential oil. Oxidative stress markers and antioxidant enzyme including malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD) were also measured. The expression of GPx, CAT, and SOD genes was investigated using real-time polymerase chain reaction (PCR).

Results: The main constituents of essential oil gum were beta-pinene (29.38%), followed by alpha-pinene (18.15%), myrcene (7.36%), trans-pinocarveol (7.15%), and camphene (4.12%). Diabetes induced an increased level of MDA (69.92?±?3.92 vs. 43.76?±?3.73) and decreased levels of GSH (2.57?±?0.40 vs. 7.05?±?1.59), GPx (11.66?±?2.2 vs. 16.38?±?2.1), CAT (12.17?±?3.38 vs. 18.7?±?2.66), and SOD (0.78?±?0.67 vs. 2.41?±?0.46). In contrast, PAO treatment significantly decreased MDA (54.59?±?12.54 vs. 69.92?±?3.92) and increased GSH (4.5?±?0.89 vs. 2.57?±?0.40), GPx (25.86?±?5.37 vs. 11.66?±?2.2), CAT (22.69?±?0.36 vs. 12.17?±?3.38), and SOD (3.65?±?1.08 vs. 0.78?±?0.67) (p?<?0.05). Moreover, our results indicated that both GPx and CAT mRNA levels significantly increased approximately 4.46 and 6.23 times in rats fed with 200?mg/kg of PAO, more than that of the healthy control group, respectively (p?<?0.01 and p?<?0.001, respectively). Also, the average expression level of SOD was also significantly 1.57 higher in rats fed with 200?mg/kg of PAO in comparison to the diabetic control group (p?<?0.05).

Conclusion: The results indicated that PAO could be propose as an agent that protects the body against diseases that are associated with oxidative stress.  相似文献   

6.
<正>what is the rationale for immunotherapies in Parkinsonian syndromes(PS)? PS are neurodegenerative diseases which are clinically characterized by a hypokinetic phenotype in combination with additional motor and non-motor symptoms. One major patholog-  相似文献   
7.
International Urology and Nephrology - Many attempts are being made to find an association between varicocele characteristics and sperm parameters. In this study, we investigated the association...  相似文献   
8.
9.
Background: Making progressin treatment of all branches of cancers has increasedthe percent of patients that never experience the event of interest. These cases are called immune or cure and models for handling the data included cure fraction rate, are referred to as cure model or long-term survival models. Methods:The data for this historical cohort study, were collected from leukemia patients diagnosed between 2007 to 2014 and followed up until 2016 in Taleghani hospital and received BMT (Bone Marrow Transplant). Some data had to be excluded because of incomplete information. Using recorded files mostly and phone calls rarely, were made to confirm whether the patients were still alive or not. Death due to leukemia was regarded as interested event. Analysis were performed by R version 3.4.1and Stata version 14. Results: Number of recurrents after receiving BMT, pre-transplant Hb and age at diagnosis were found as significant prognostics of survival time. HD patients had the highest 5-years overall survival in category of diagnosis type with 81.3%. Cure fraction was estimated to be 64.1%. Conclusion: According to high percentage of censoring, using long-term model had better fit.  相似文献   
10.
The uniform multidrug therapy clinical trial, Brazil (U-MDT/CT-BR), database was used to describe and report the performance of available tools to classify 830 leprosy patients as paucibacillary (PB) and multibacillary (MB) at baseline. In a modified Ridley and Jopling (R&J) classification, considering clinical features, histopathological results of skin biopsies and the slit-skin smear bacterial load results were used as the gold standard method for classification. Anti-phenolic glycolipid-I (PGL-I) serology by ML Flow test, the slit skin smear bacterial load, and the number of skin lesions were evaluated. Considering the R&J classification system as gold standard, ML Flow tests correctly allocated 70% patients in the PB group and 87% in the MB group. The classification based on counting the number of skin lesions correctly allocated 46% PB patients and 99% MB leprosy cases. Slit skin smears properly classified 91% and 97% of PB and MB patients, respectively. Based on U-MDT/CT-BR results, classification of leprosy patients for treatment purposes is unnecessary because it does not impact clinical and laboratories outcomes. In this context, the identification of new biomarkers to detect patients at a higher risk to develop leprosy reactions or relapse remains an important research challenge.  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