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   603篇
  免费   33篇
耳鼻咽喉   20篇
儿科学   10篇
妇产科学   14篇
基础医学   72篇
口腔科学   57篇
临床医学   78篇
内科学   80篇
皮肤病学   25篇
神经病学   43篇
特种医学   9篇
外科学   29篇
综合类   7篇
预防医学   114篇
眼科学   6篇
药学   33篇
中国医学   1篇
肿瘤学   38篇
  2023年   9篇
  2022年   8篇
  2021年   16篇
  2020年   10篇
  2019年   12篇
  2018年   15篇
  2017年   10篇
  2016年   14篇
  2015年   12篇
  2014年   16篇
  2013年   26篇
  2012年   43篇
  2011年   40篇
  2010年   35篇
  2009年   27篇
  2008年   36篇
  2007年   46篇
  2006年   27篇
  2005年   30篇
  2004年   36篇
  2003年   37篇
  2002年   34篇
  2001年   3篇
  2000年   4篇
  1999年   6篇
  1998年   7篇
  1997年   10篇
  1996年   4篇
  1995年   2篇
  1994年   6篇
  1993年   3篇
  1992年   3篇
  1991年   3篇
  1990年   3篇
  1989年   4篇
  1988年   6篇
  1987年   3篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1983年   2篇
  1977年   2篇
  1976年   1篇
  1975年   3篇
  1974年   3篇
  1973年   1篇
  1972年   1篇
  1971年   3篇
  1969年   1篇
  1962年   1篇
排序方式: 共有636条查询结果,搜索用时 31 毫秒
1.
2.
3.
Rh incompatibility disease (ie Rh hemolytic disease of the fetus and newborn) has been implicated as a risk factor for schizophrenia. Here, we extend the maternal-fetal genotype incompatibility (MFG) test used in an earlier case-parent trio study that found significant evidence for an increased risk of schizophrenia in RHD MFG-incompatible children. We modify the MFG test for case-parent trios to include any number of siblings. This modified test enables us to use more of the available data from the earlier study. The increased sample size not only gives us greater power to test for MFG incompatibility but it also enables us to model the impact of previous RHD MFG-incompatible pregnancies on the relative risk of RHD MFG incompatibility in later-born siblings. This modeling is important, because RHD MFG incompatibility is a proxy for Rh incompatibility disease, and the risk of Rh incompatibility disease increases with the number of previous RHD MFG-incompatible pregnancies. The best-fitting models are consistent with the hypothesized effect that previous incompatible pregnancies increase the risk of schizophrenia due to RHD MFG incompatibility. There was significant evidence that the relative risk of schizophrenia in the second- and later-born RHD MFG-incompatible children is 1.7, consistent with earlier estimates. Our extension of the MFG test has general application to family-based studies of maternal-genotype and MFG interaction effects.  相似文献   
4.
BACKGROUND: We assessed the prevalence of mood disturbance among women with prospectively documented polycystic ovary syndrome (PCOS). METHODS: Thirty-two women with PCOS completed the Center for Epidemiological Studies-Depression Rating Scale (CES-D). Clinical and biochemical characteristics were assessed. RESULTS: Sixteen women had CES-D scores indicative of depression. Depression was associated with greater insulin resistance (P=0.02) and higher body mass index (P=0.05). Women receiving oral contraceptives for the treatment of PCOS were less depressed than patients not receiving treatment (P=0.03). LIMITATIONS: Possible selection bias, use of a screening tool alone without further diagnostic evaluation of depression, small samples size and lack of direct comparison with an age matched control group, should be considered in interpretation of these results. CONCLUSION: Findings suggest a high prevalence of depression among women with PCOS, and an association between depression and PCOS markers.  相似文献   
5.
We evaluated the usefulness of a fluorometric method for determining serum retinol (Futterman et al., Invest Ophthalmol Vis Sci 1975;14:125-30) in which fluorescence (excitation 335 nm; emission 460 nm) of retinol is directly measured in unextracted, diluted serum. Using serum from 466 individual donors, we compared values so obtained with those by a "high-performance" liquid-chromatographic method. The correlation coefficient (r) was 0.74. When we compared fluorometric retinol values with retinol-binding protein values for the 466 samples, r was 0.71. About 1% of the 466 samples had markedly higher values by fluorometry than by chromatography, the result of positive interferences. For two serum pools, we obtained CVs of 1.58% (n = 57) and 1.79% (n = 57) in long-term precision studies lasting 60 days. Although the fluorometric method of Futterman et al. has not been widely adopted, we find that it is simple to perform and that results compare favorably with the chromatographic method in precision and accuracy. It is unique among commonly used serum retinol methods in that the serum need not be extracted with organic solvents.  相似文献   
6.
The influences of gender, ethnicity, and sport of varsity athletes on their vitamin/mineral supplementation habits were examined. Subjects included 145 females and 266 males from 22 varsity teams; 80% were Caucasian; 12% African American; and 8% Combined-Other. Over half of the subjects took supplements. Males were more likely than females to give "too expensive" as a reason for not taking supplements, and "improve athletic performance" and "build muscle" as reasons for taking supplements. The most common supplement was multivitamins plus minerals. Females were more likely to take calcium and iron, and males vitamins B12 and A. African Americans were the most likely to take vitamin A. Males were more likely to get supplement information from nutritionists/dietitians and self, and females from family members or friends and physicians or pharmacists. Football players were more likely to get supplement information from nutritionists/dietitians, and males in other sports from coaches/trainers. There were some differences in vitamin/mineral supplement habits of the athletes by gender, ethnicity, and sport.  相似文献   
7.
Pesticides are used on a massive scale in the United States. The widespread use of these pesticides has made it virtually impossible for the average person to avoid exposure at some level. Generally, it is believed that low-level exposure to these pesticides does not produce acute toxic effects; however, various cancers and other noncancer health endpoints have been associated with chronic exposure to several groups of pesticides. Therefore, it is imperative that well-designed studies investigate the potential relationship between contemporary pesticide exposure and health effects. For these studies to be accurate, reliable methods for determining individual exposure must be used. Biological monitoring is a useful tool for assessing exposure to some contemporary pesticides. As with any analytical method, biological monitoring entails many difficulties, but, in many instances, they can be overcome by the logical use of available information and information acquired in carefully designed studies. At the Centers for Disease Control and Prevention (CDC), we have acquired extensive experience in the development and application of specific techniques for biological monitoring of a variety of toxicants, including many of the contemporary-use pesticides. We have used these methods to measure the internal dose of pesticides received by people in acute and chronic incidents resulting from both environmental and industrial exposure. Additionally, we have established normative values, or reference ranges, of several pesticides based on measurements of their metabolites in the urine of randomly selected adults in the US population. These data have been successfully used to distinguish overt exposures from 'background' exposure. In this paper, we present several examples of the usefulness of biological monitoring in urine and blood and describe the difficulties involved with developing methods in these matrices. We also present a general strategy, considerations, and recommendations for developing biological monitoring techniques for measuring the internal dose of contemporary-use pesticides.  相似文献   
8.
9.
Plasma triglycerides and cholesterol concentrations were determined for 18 young women using the same brand of oral contraceptives (OCs) at 2 different estrogen levels and for 10 women never having used the pill. Dietary intakes of lipids and calories were similar for all subects. OC brands used Ortho-Novum and Norinyl 1/50) contained either .05 or .08 mg of mestranol plus 1 mg of norethindrone. Test subjects had taken the OCs for at least 1 year. A 12-hour fasting blood sample was taken on Days 20-25 of a menstrual cycle. Plasma samples were frozen for later analysis. Samples were analyzed for simultaneous determinations of triglycerides and cholesterol with a Technicon Auto Analyzer 2 system by the Rush et al. procedure. OC users, particularly those taking the higher estrogen dose, had elevated plasma triglycerides which were significantly higher than controls. Plasma cholesterol levels of OC users were similar to controls.  相似文献   
10.
OBJECTIVE: To investigate the effect of changes within the spiral ligament and stria vascularis on hearing in cochlear otosclerosis, we examined spiral ligament hyalinization, stria vascularis atrophy, and sensory hearing loss in cochlear otosclerosis and described changes in ion transport molecule expression. STUDY DESIGN: Retrospective. SETTING: Tertiary referral center. PATIENTS: Thirty-two cochleae from 24 temporal bone donors with histologic evidence of cochlear otosclerosis, including spiral ligament hyalinization. INTERVENTION: Audiography. MAIN OUTCOME MEASURES: Measurements of spiral ligament width, stria vascularis, and bone-conduction thresholds were compared by the amount of hyalinization. Expression of the ion transport molecules Na,K-ATPase, connexin 26, and carbonic anhydrase II were assessed by immunohistochemical techniques. RESULTS: Hyalinization most often involved the posterior basal turn (88%) and the posterior middle turn (27%). Spiral ligament hyalinization correlated significantly with stria vascularis atrophy in the posterior middle turn of the cochlea (rho = -0.63, p < 0.01). There was a trend toward a significant association in the posterior basal turn (rho = -0.31, p < 0.08). Bone-conduction thresholds at 2,000 and 4,000 Hz were significantly associated with the amount of stria vascularis atrophy (rho = -0.44, -0.40, p < 0.05). In addition, we observed decreased immunostaining for both carbonic anhydrase II with Type I fibrocytes and Na,K-ATPase with stria vascularis and Type II and Type IV fibrocytes of the spiral ligament in cochlear otosclerosis sections compared with normal cochlea. Na,K-ATPase staining within the stria vascularis was further decreased in the presence of spiral ligament hyalinization. No significant differences were seen with connexin 26 immunostaining. However, immunostaining results were somewhat inconsistent. CONCLUSION: These data suggest that spiral ligament structure and function are essential for stria vascularis survival. In addition, dampened expression of ion transport molecules within the spiral ligament and stria vascularis may disrupt potassium ion recycling, resulting in loss of endocochlear potential and sensory hearing loss.  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