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   2035篇
  免费   101篇
  国内免费   7篇
耳鼻咽喉   33篇
儿科学   70篇
妇产科学   43篇
基础医学   224篇
口腔科学   25篇
临床医学   191篇
内科学   416篇
皮肤病学   25篇
神经病学   110篇
特种医学   32篇
外国民族医学   2篇
外科学   371篇
综合类   46篇
预防医学   114篇
眼科学   172篇
药学   108篇
中国医学   13篇
肿瘤学   148篇
  2023年   13篇
  2022年   13篇
  2021年   80篇
  2020年   44篇
  2019年   60篇
  2018年   69篇
  2017年   55篇
  2016年   64篇
  2015年   72篇
  2014年   88篇
  2013年   146篇
  2012年   200篇
  2011年   170篇
  2010年   80篇
  2009年   77篇
  2008年   130篇
  2007年   152篇
  2006年   139篇
  2005年   117篇
  2004年   106篇
  2003年   67篇
  2002年   56篇
  2001年   13篇
  2000年   13篇
  1999年   18篇
  1998年   11篇
  1997年   8篇
  1996年   12篇
  1995年   7篇
  1992年   6篇
  1991年   8篇
  1990年   3篇
  1989年   3篇
  1988年   2篇
  1987年   2篇
  1985年   2篇
  1984年   6篇
  1983年   3篇
  1980年   2篇
  1979年   5篇
  1978年   2篇
  1971年   2篇
  1970年   1篇
  1968年   3篇
  1967年   3篇
  1965年   1篇
  1964年   1篇
  1962年   1篇
  1961年   1篇
  1924年   1篇
排序方式: 共有2143条查询结果,搜索用时 534 毫秒
91.
92.
93.
In recent years, research and development of geopolymers has gained significant interest in the fields of repairs and restoration. This paper investigates the application of a geopolymer as a repair material by implementation of high-calcium fly ash (FA) as a main precursor, activated by a sodium hydroxide and sodium silicate solution. Three methods of concrete substrate surface preparation were cast and patched: as-cast against ordinary Portland cement concrete (OPCC), with drilled holes, wire-brushed, and left as-cast against the OPCC grade 30. This study indicated that FA-based geopolymer repair materials (GRMs) possessed very high bonding strength at early stages and that the behavior was not affected significantly by high surface treatment roughness. In addition, the investigations using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy have revealed that the geopolymer repair material became chemically bonded to the OPC concrete substrate, due to the formation of a C–A–S–H gel. Fundamentally, the geopolymer network is composed of tetrahedral anions (SiO4)4− and (AlO4)5− sharing the oxygen, which requires positive ions such as Na+, K+, Li+, Ca2+, Na+, Ba2+, NH4+, and H3O+. The availability of calcium hydroxide (Ca(OH)2) at the surface of the OPCC substrate, which was rich in calcium ions (Ca2+), reacted with the geopolymer; this compensated the electron vacancies of the framework cavities at the bonding zone between the GRM and the OPCC substrate.  相似文献   
94.

The study evaluated the hepatoprotective activity of plant extracts of cinnamon and glycyrrhizin in distinct dosage ways to minimize the oxidative stress induced by carbon tetrachloride (CCl4) in BALB/cJ inbred albino mice. Fifteen albino mice were divided into five groups, each group containing three mice. Group A was referred as positive control while group B, C, D and E were injected intraperitoneally with 1 mL/kg body weight of CCl4 twice a week for 1 month. Group C and D were treated orally with isolated extracts of cinnamon @50 mg/kg and glycyrrhizin @50 mg/kg respectively on daily basis for 1 month. However, group E was treated orally with combination dose of cinnamon @50 mg/kg + glycyrrhizin @50 mg/kg body weight. The increase in the levels of alanine transaminase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP), triglyceride (TG), malondialdehyde (MDA) and glucose were recorded in CCl4 induced liver injury in mice while there is decrease in the levels of total protein (TP), reduced glutathione (GSH), Superoxide dismutase (SOD) and catalase (CAT) in CCL4 intoxicated mice. Isolated therapy of plant extracts of cinnamon and glycyrrhizin decreased the levels of ALT, AST, ALP, MDA, TG and glucose whereas increase in TP, GSH, SOD and CAT was observed in plant extracts treated mice. The best restoration of all the above said parameters near to control was observed in group of mice treated with combination dose of cinnamon and glycyrrhizin @50 mg/kg. Therefore, the present study declared the antioxidative, anti-inflammatory and hepatoprotective activity of standardized extracts of cinnamon and glycyrrhizin and their potent defensive property.

  相似文献   
95.
Since 1939, it has been known that, silicosis and extrinsic allergic alveolitis can be seen among dental technicians. The interstitial disease caused by the exposure to complex substances used by dental technicians is classified as a special group called dental technician's pneumoconiosis. A 36-year-old man, who has no smoking history, presented with severe dyspnea. He had worked in different dental laboratories for 22 years, but he did not have respiratory symptoms until five years ago. After that date, he had hospitalized and had been examined for respiratory pathologies for many times. He had came to our clinic, because of the progression of his dyspnea. Diffuse pulmonary parenchymal infiltrates which can be related with pneumoconiosis and chronic type 1 respiratory deficiency had been diagnosed as the result of the examinations. While he has no history of smoking or any other risk factors or diseases in his medical history, the case was accepted as dental technician's pneumoconiosis. The factors related with the pathogenesis of dental technician's pneumoconiosis are; the complex compound of the substances (metal dusts, silica, plaster, wax and resins, chemical liquids, methyl methacrylate) used in this sector and their effects on the lung parenchyma. Extrinsic allergic alveolitis related with methyl methacrylate has been reported. The most important factor to acquire an occupational lung disease is a complex occupational exposure. The insufficient workplace airing and the lack of preventive measures added on this exposure, the risks become much more greater.  相似文献   
96.
Coronary artery aneurysms are defined as coronary dilatations which exceed the diameter of normal adjacent segments by 1.5 times. Left main coronary artery (LMCA) is the least frequently involved artery with a prevalence of 0.1%. Majority of coronary artery aneurysms are atherosclerotic in origin. Their size and clinical presentation is variable. A number of complications have been reported to occur during the course of the disease including thrombosis and distal embolization, myocardial ischemia and/or infarction, dissection, vasospasm, calcification, fistulization and very rarely rupture. Large aneurysms of LMCA represent a potentially fatal condition even without concomitant atherosclerotic coronary disease. Because of rarity of coronary artery aneurysms, it is difficult to standardize treatment. In this article, we presented 4 cases of large LMCA aneurysms with various clinical and angiographic features.  相似文献   
97.
This study is aimed to evaluate the incidence of silicosis and the relation of it with personal and work-related factors among workers exposed to silica in ceramic factory. Workers were evaluated by respiratory symptoms, physical examination, pulmonary function and radiological findings. Occupational and Enviromental Pulmonary Disease Evaluation Questionnaire of the Turkish Thoracic Society Enviromental and Occupational Pulmonary Diseases Working Group was used. 365 of 626 workers had exposure to silica and the rest 261 were concerned as control group. There was no difference between mean age, duration of work and smoking pack year among the groups (p> 0.05). Cough and sputum rates were higher in silicosis group FEV1 and FVC values were lower in silica group but this was not statistically significant. When the two subgroups of silica group (the workers in high dust concentration and the ones in low concentration) were compared, the high concentrated group had significantly more sputum but the other symptoms and pulmonary functional parameters were not different significantly. 24 workers had parenchymal densities adjusted with pneumoconiosis. The workers with the pneumoconistic finding, had a higher mean age and longer duration of work. As a conclusion, ceramic industry has risk for silicosis. And the risk increase by time and age.  相似文献   
98.
Child marriage (before 18 years) is prevalent in Pakistan, which disproportionately affects young girls in rural, low income and low education households. Our study aims to determine the association between early marriage and high fertility and poor fertility health indicators among young women in Pakistan beyond those attributed to social vulnerabilities. Nationally representative data from Pakistan Demographic and Health Survey, 2006–2007, a cross-sectional observational survey, were limited to ever-married women aged 20–24 years (n = 1,560; 15 % of 10,023) to identify differences in poor fertility outcomes [high fertility (three or more childbirths); rapid repeat childbirth (<24 months between births); unwanted pregnancy (any ever); pregnancy termination (any stillbirth, miscarriage or abortion ever)] by early (<18) versus adult (≥18) age at marriage. Associations between child marriage and fertility outcomes were assessed by calculating adjusted odds ratios (AORs) using logistic regression models after controlling for demographics, social equity indicators (education, wealth index, rural residence), contraception use, marriage duration and culture-specific factors (husband’s desire for more children, son preference). Overall, 50 % of ever-married women aged 20–24 years in Pakistan were married before the age of 18 years. Girl child marriage was significantly (p < 0.001) associated with low social equity indicators (poverty, rural residence, and no formal education). Adjusted logistic regression models showed that girl child marriage was significantly associated with high fertility (AOR 6.62; 95 % CI 3.53–12.43), rapid repeat childbirth (AOR 2.88; 95 % CI 1.83–4.54), unwanted pregnancy (AOR 2.90; 95 % CI 1.75–4.79), and pregnancy termination (AOR 1.75; 95 % CI 1.10–2.78). Girl child marriage affects half of all ever-married women aged 20–24 years in Pakistan, and increases their risk for high fertility and poor fertility health indicators, highlighting the need of increasing the age of marriage among women in Pakistan. Efforts to eliminate girl child marriage by strict law enforcement, promoting civil, sexual and reproductive health rights for women can help eliminate girl child marriage in Pakistan.  相似文献   
99.
The aim of this study was to determine the effects of hesperidin (HP) on neuronal damage in brain tissue caused by global cerebral ischemia/reperfusion (I/R) in C57BL/J6 mice. For this purpose, a total of 40 mice were divided equally into four groups: (1) sham-operated (SH), (2) global cerebral I/R, (3) HP, and (4) HP+I/R. The SH group was used as a control. In the I/R group, the bilateral carotid arteries were clipped for 15 min, and the mice were treated with vehicle for 10 days. In the HP group, mice were administered HP (100 mg/kg) for 10 days without carotid occlusion. In the HP+I/R group, the I/R model was applied to the mice exactly as in the I/R group, and they were then treated with 100 mg/kg HP for 10 days. Cerebral I/R significantly induced oxidative stress via an increase in lipid peroxidation and a decrease in the components of the antioxidant defense system. Furthermore, cerebral I/R increased the incidence of histopathological damage and apoptosis in brain tissue. HP treatment significantly reversed the oxidative effects of I/R and inhibited the development of neurodegenerative histopathology. Therefore, the current study demonstrates that HP treatment effectively prevents oxidative and histological damage in the brain caused by global I/R. In this context, the beneficial effects of HP are likely a result of its strong antioxidant and free radical-scavenging properties. HP may be an useful treatment to attenuate the negative effects of global cerebral I/R.  相似文献   
100.
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