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   4763篇
  免费   290篇
  国内免费   51篇
耳鼻咽喉   69篇
儿科学   123篇
妇产科学   85篇
基础医学   583篇
口腔科学   342篇
临床医学   370篇
内科学   1242篇
皮肤病学   168篇
神经病学   329篇
特种医学   292篇
外科学   491篇
综合类   35篇
预防医学   424篇
眼科学   48篇
药学   340篇
中国医学   23篇
肿瘤学   140篇
  2023年   52篇
  2022年   87篇
  2021年   183篇
  2020年   105篇
  2019年   136篇
  2018年   162篇
  2017年   121篇
  2016年   132篇
  2015年   155篇
  2014年   190篇
  2013年   258篇
  2012年   286篇
  2011年   320篇
  2010年   196篇
  2009年   165篇
  2008年   231篇
  2007年   228篇
  2006年   182篇
  2005年   202篇
  2004年   118篇
  2003年   116篇
  2002年   128篇
  2001年   98篇
  2000年   71篇
  1999年   71篇
  1998年   95篇
  1997年   88篇
  1996年   93篇
  1995年   59篇
  1994年   76篇
  1993年   60篇
  1992年   29篇
  1991年   37篇
  1990年   35篇
  1989年   58篇
  1988年   52篇
  1987年   39篇
  1986年   37篇
  1985年   31篇
  1984年   30篇
  1983年   17篇
  1982年   24篇
  1981年   20篇
  1980年   14篇
  1979年   26篇
  1978年   14篇
  1977年   16篇
  1976年   18篇
  1975年   16篇
  1973年   18篇
排序方式: 共有5104条查询结果,搜索用时 31 毫秒
91.
The eyes of rhesus monkeys were exposed to argon (514.5 nm) and ruby (694.3 nm) laser irradiation using various retinal image diameters which were estimated by microphotometric techniques. The experimental design for both wavelengths produced image diameters of 40μ to 50μ for the “minimal” case and approximately 500μ to 1,000μ for the larger irradiance series employed. Extramacular retinal exposure sites were examined by ophthalmoscopic and histopathological techniques. Flat preparations of the pigmented epithelium and sensory layers of the retina were utilized in the confirmation of damage at low power levels. All data were statistically analyzed to establish trends, and results were compared for the wavelengths employed. Results indicate that retinal damage is primarily dependent on energy distribution as a function of image diameter and exposure duration.  相似文献   
92.
Adequate prenatal care provides an opportunity for counseling and reducing the complications associated with pregnancy and delivery. Our objective was to describe the demographic, behavioral, and clinical profile of the pregnant women hospitalized at public maternity hospitals and to identify factors associated with six or more prenatal consultations in Vitória, Brazil. A cross-sectional study of 1,380 women was conducted in public maternity hospitals in Vitória, Brazil. Sixty-seven percent of participants had ≥6 prenatal consultations. Reasons for hospitalization were vaginal delivery (55.7%), cesarean section (32.9%), clinical treatment (7.7%), and abortion/miscarriage (3.7%). Having ≥9 years of schooling (odds ratio, OR = 1.8; 95% confidence interval, CI: 1.1–3.1), being married (OR = 1.9; 95% CI: 1.2–2.9) and delivering at term (OR = 3.6; 95% CI: 1.6–8.2) were significantly independently associated with having ≥6 prenatal consultations. Although higher education, being married, and delivering at term were associated with ≥6 prenatal consultations in this population, the high rate of Cesarean sections demonstrates the need for ongoing educative strategies among health professionals.  相似文献   
93.
IntroductionErectile dysfunction (ED) is associated with neurological damage due to human T-lymphotropic virus 1 (HTLV-1) infection, but hormonal and psychogenic factors also cause ED.AimTo evaluate the association of psychogenic and hormonal factors with ED in men infected with HTLV-1.MethodsIn this cross-sectional study, we compared total testosterone, follicle stimulating hormone, luteinizing hormone, prolactin, anxiety symptoms, depressive symptoms, and neurologic manifestations in HTLV-1-infected men with or without ED. The International Index of Erectile Function was used to determine the degree of ED. Participants were grouped according to Osame’s Motor Disability Scale and the Expanded Disability Status Scale: HTLV-1-associated myelopathy or tropical spastic paraparesis (HAM/TSP), probable HAM/TSP, or HTLV-1 carrier. Chi-square and Fisher’s exact tests were used to compare the groups, and regression analyses were used to show predictors of ED.Main Outcome MeasureSexual hormonal levels, psychogenic factors, and neurologic disabilities were found to be associated with ED.ResultsED was associated with age older than 60 years (P < .001), degree of neurologic involvement (P < .001), depression (P = .009), and anxiety (P = .008). In the multivariate analyses, only age and degree of neurological injury remained as risk factors for ED.Clinical ImplicationsNeurological manifestations are a stronger predictor of ED than hormonal and psychogenic factors in HTLV-1-infected men.Strengths & LimitationsThe statistical power of the study was limited due to the low number of participants, but neurologic manifestations were clearly associated with ED. There was no strong association between hormonal and psychogenic factors and ED.ConclusionHormonal and psychogenic factors did not show a strong association with ED in individuals with HTLV-1, but neurological manifestations were strongly associated with ED in these individuals.de Oliveira CJV, Neto, JAC, Andrade RCP, et al. Hormonal and Psychogenic Risk Factors for Erectile Dysfunction in Men with HTLV–1. J Sex Med 2019; 16:1763–1768.  相似文献   
94.
95.
96.
97.
98.
99.
100.
Tobacco is a major Brazilian cash crop. Tobacco farmers apply large amounts of pesticides to control insect growth. Workers come into contact with green tobacco leaves during the tobacco harvest and absorb nicotine through the skin. In the present study, micronucleus frequency, cell death, and the frequency of basal cells were measured in tobacco farmers using the buccal micronucleus cytome assay (BMCyt), in parallel with measurement of blood butyrylcholinesterase (BChE) and nicotine levels. Polymorphisms in PONIGln192Arg and CYP2A6*9(?48T>G) were evaluated to verify the relationship between genetic susceptibility and the measured biomarkers. Peripheral blood and buccal cell samples were collected from 106 agricultural workers, at two different crop times (during pesticide application and leaf harvest), as well as 53 unexposed controls. BMCyt showed statistically significant increases in micronuclei, nuclear buds, and binucleated cells among exposed subjects in differentiated cells, and in micronuclei in basal cells. In addition, the exposed group showed higher values for condensed chromatin, karyorrhectic, pyknotic, and karyolitic cells, indicative of cell death, and an increase in the frequency of basal cells compared to the unexposed control group. A slight difference in mutagenicity using the BMCyt assay was found between the two different sampling times (pesticide application and leaf harvest), with higher micronucleus frequencies during pesticide application. Elevated cotinine levels were observed during the leaf harvest compared to the unexposed controls, while BChE level was similar among the farmers and controls. PONIGln192Arg and CYP2A6*9(?48T>G) polymorphisms were associated with DNA damage induced by pesticides and cell death. Environ. Mol. Mutagen., 2012. © 2012 Wiley Periodicals, Inc.  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