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   4656篇
  免费   342篇
  国内免费   29篇
耳鼻咽喉   122篇
儿科学   121篇
妇产科学   115篇
基础医学   714篇
口腔科学   151篇
临床医学   410篇
内科学   905篇
皮肤病学   51篇
神经病学   266篇
特种医学   123篇
外国民族医学   3篇
外科学   781篇
综合类   98篇
一般理论   4篇
预防医学   280篇
眼科学   121篇
药学   403篇
中国医学   49篇
肿瘤学   310篇
  2024年   4篇
  2023年   43篇
  2022年   50篇
  2021年   214篇
  2020年   133篇
  2019年   175篇
  2018年   230篇
  2017年   141篇
  2016年   157篇
  2015年   176篇
  2014年   238篇
  2013年   280篇
  2012年   492篇
  2011年   432篇
  2010年   224篇
  2009年   174篇
  2008年   248篇
  2007年   255篇
  2006年   231篇
  2005年   199篇
  2004年   163篇
  2003年   160篇
  2002年   138篇
  2001年   48篇
  2000年   48篇
  1999年   38篇
  1998年   36篇
  1997年   22篇
  1996年   20篇
  1995年   10篇
  1994年   18篇
  1993年   15篇
  1992年   21篇
  1991年   22篇
  1990年   14篇
  1989年   15篇
  1988年   20篇
  1987年   20篇
  1986年   7篇
  1985年   13篇
  1984年   7篇
  1983年   4篇
  1980年   6篇
  1978年   4篇
  1977年   5篇
  1975年   3篇
  1974年   8篇
  1973年   10篇
  1972年   3篇
  1971年   4篇
排序方式: 共有5027条查询结果,搜索用时 15 毫秒
131.
Cyclophosphamide is an antineoplastic medicine that causes disorder in functions of the body systems. Thus, the purpose of this study is to investigate the effect of hydroalcoholic extract of saffron on improving the complications of cyclophosphamide on sex hormones. Fifty-six adult female Wistar rats were randomly divided into seven groups; control, sham (received distilled water, solvent extract, and drug), experimental groups 1, 2, and 3 (received cyclophosphamide (5 mg/kg/bw) + hydroalcoholic extract of saffron (2, 1, and 0.5 g/kg/bw), experimental group 4 (saffron 2 g/kg/bw), and experimental group 5 (cyclophosphamide 5 mg/kg/bw). Cyclophosphamide was given intraperitoneally, and extract by gavage was prescribed for 21 days. At the end of the experiment, after blood and preparation of serum, ELISA method was used for measuring the estrogen, progesterone, FSH, and LH hormones. Data and LSD test were analyzed with SPSS software (version 18). Results show that the concurrent use of low-dose cyclophosphamide and saffron extract can reduce toxic effect of cyclophosphamide on pituitary-gonadal axis and cause estrogen to be produced.  相似文献   
132.

Background:

Dentistry equipment are exposed to different types of pathogenic microorganisms. The aim of this study was to investigate the effect of spraying three different types of disinfectants on condensational silicones after 5 and 10 min.

Materials and Methods:

Totally, 66 circular samples of condensational silicone impression materials of 1 cm diameter and 2 mm thickness were contaminated by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans fungus. Except for control samples, all of them were disinfected with sodium hypochlorite (NaOCl) 0.525%, Deconex and Epimax by spraying method. Afterward, they kept in plastic bags with humid rolled cotton for 5 and 10 min. In order to isolate microbiotas, the samples were immersed in 2% trypsin for 1 h and diluted with normal saline in a portion of 1, 1/2, and 1/4. The trypsin suspensions were transferred to culture plates for incubation and colony-forming unit assay. The data were analyzed by Mann–Whitney test and SPSS software version 16 at a significant level of 0.05.

Results:

There was a meaningful difference between disinfection effects of Epimax-Deconex for all mentioned microorganisms after 5 min (P = 0.034), and between disinfection effects of NaOCl 0.525%-Epimax for S. aureus (P = 0.043) and P. aeruginosa (P = 0.046) after 5 min. Furthermore, there was a meaningful difference between disinfection effects of Epimax-Deconex (P = 0.034) and NaOCl 0.525%-Epimax (P = 0.034) for P. aeruginosa after 10 min.

Conclusion:

Condensational silicone can be effectively disinfected by spraying tested three disinfecting agents. More specifically, Deconex showed the best results compared to the other agents.Key Words: Condensational silicone, disinfection, impression materials, spray  相似文献   
133.
134.
The level set approach to segmentation of medical images has received considerable attention in recent years. Evolving an initial contour to converge to anatomical boundaries of an organ or tumor is a very appealing method, especially when it is based on a well-defined mathematical foundation. However, one drawback of such evolving method is its high computation time. It is desirable to design and implement algorithms that are not only accurate and robust but also fast in execution. Bresson et al. have proposed a variational model using both boundary and region information as well as shape priors. The latter can be a significant factor in medical image analysis. In this work, we combine the variational model of level set with a multi-resolution approach to accelerate the processing. The question is whether a multi-resolution context can make the segmentation faster without affecting the accuracy. As well, we investigate the question whether a premature convergence, which happens in a much shorter time, would reduce accuracy. We examine multiple semiautomated configurations to segment the prostate gland in T2W MR images. Comprehensive experimentation is conducted using a data set of a 100 patients (1,235 images) to verify the effectiveness of the multi-resolution level set with shape priors. The results show that the convergence speed can be increased by a factor of ≈?2.5 without affecting the segmentation accuracy. Furthermore, a premature convergence approach drastically increases the segmentation speed by a factor of ≈?17.9.  相似文献   
135.
Objective: To determine epidemiologic and metabolic characteristics of renal stone in the northern Iran. Methods: We prospectively analyzed demographic, clinical and metabolic findings in children less than 16 years old with renal stone revealed by ultrasonography from September 2003 to May 2012. Evaluations included serum and urine measurement of main elements predisposing patients to stone formation. Findings : 271 children (160 males) aged 2 months to 16-years (mean 30 months) were evaluated. 91 (33.6%) had a positive family history, abdominal discomfort (18.8%), UTI (11.8%) and hematuria (11.4%) were main presenting features. 45 children were diagnosed accidentally without any specific compliant. Nearly all (99%) stones lay in kidney., 35.1% had metabolic, 10% infective and 4.1% obstructive trends, 110 children had no definable etiology. Hypercalciuria (25.5%) hyperoxaluria (18.4%) and hypocitraturia (18.1%) were more frequent than uricosuria (8.5%) and cystinuria (3.1%) Conclusion: Metabolic derangement plays significant role in stone formation in our area. Patients should be carefully evaluated considering this point of view.Key Words: Nephrolithiasis, Kidney Stone, Hypercalciuria, Hyperoxaluria, Cystinuria, Hypocitraturia  相似文献   
136.
Metformin, an oral anti-diabetic agent in the biguanide class is a widely prescribed drug to treat high blood glucose in patients with type 2 diabetes mellitus. Metformin has three different roles, including blood glucose regulatory effect, protection of kidney tubular cell by acting as an effective antioxidant and finally ameliorative effect on diabetic kidney disease through saving the podocytes. Therefore, diabetic patients may benefit from all of these three distinct ameliorative effects.Key Words: Metformin, Kidney Disease, Diabetes, Anti-diabetic Agents  相似文献   
137.
Despite major insecticide-based vector control programs, dengue continues to be a major threat to public health in urban areas. The reasons for this failure include the emergence of insecticide resistance and the narrowing of the spectrum of efficient products. Cigarette butts (CBs), the most commonly discarded piece of waste, also represent a major health hazard to human and animal life. CBs are impregnated with thousands of chemical compounds, many of which are highly toxic and none of which has history of resistance in mosquitoes. This study was performed to examine whether exposure to CB alters various biological parameters of parents and their progeny. We examined whether the mosquito changes its ovipositional behaviors, egg hatching, reproductive capacity, longevity and fecundity in response to CB exposure at three different concentrations. Females tended to prefer microcosms containing CBs for egg deposition than those with water only. There were equivalent rates of eclosion success among larvae from eggs that matured in CB and water environments. We also observed decreased life span among adults that survived CB exposure. Extracts of CB waste have detrimental effects on the fecundity and longevity of its offspring, while being attractive to its gravid females. These results altogether indicate that CB waste indirectly affect key adult life traits of Aedes aegypti and could conceivably be developed as a novel dengue vector control strategy, referring to previously documented direct toxicity on the larval stage. But this will require further research on CB waste effects on non-target organisms including humans.  相似文献   
138.
Ecotoxicology - Contamination of environment with heavy metals is increasingly becoming an issue of major concern across the globe. Heavy metals are highly toxic to humans as well as other...  相似文献   
139.
140.
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