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   1229篇
  免费   108篇
  国内免费   5篇
耳鼻咽喉   12篇
儿科学   16篇
妇产科学   23篇
基础医学   165篇
口腔科学   45篇
临床医学   119篇
内科学   239篇
皮肤病学   21篇
神经病学   110篇
特种医学   31篇
外科学   179篇
综合类   28篇
预防医学   124篇
眼科学   30篇
药学   108篇
中国医学   17篇
肿瘤学   75篇
  2024年   4篇
  2023年   16篇
  2022年   39篇
  2021年   65篇
  2020年   37篇
  2019年   72篇
  2018年   67篇
  2017年   51篇
  2016年   68篇
  2015年   46篇
  2014年   71篇
  2013年   66篇
  2012年   127篇
  2011年   121篇
  2010年   62篇
  2009年   48篇
  2008年   61篇
  2007年   79篇
  2006年   59篇
  2005年   49篇
  2004年   33篇
  2003年   27篇
  2002年   17篇
  2001年   7篇
  2000年   13篇
  1999年   3篇
  1998年   4篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   4篇
  1992年   3篇
  1991年   1篇
  1990年   3篇
  1989年   2篇
  1987年   1篇
  1986年   2篇
  1983年   1篇
  1979年   2篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1969年   1篇
排序方式: 共有1342条查询结果,搜索用时 15 毫秒
1.
2.
In 1998, the New York City Department of Health and the Mayor’s Office of Emergency Management began monitoring the volume of ambulance dispatch calls as a surveillance tool for biologic terrorism. We adapted statistical techniques designed to measure excess influenza mortality and applied them to outbreak detection using ambulance dispatch data. Since 1999, we have been performing serial daily regressions to determine the alarm threshold for the current day. In this article, we evaluate this approach by simulating a series of 2,200 daily regressions. In the influenza detection implementation of this model, there were 71 (3.2%) alarms at the 99% level. Of these alarms, 64 (90%) occurred shortly before or during a period of peak influenza in each of six influenza seasons. In the bioterrorism detection implementation of this methodology, after accounting for current influenza activity, there were 24 (1.1%) alarms at the 99% level. Two occurred during a large snowstorm, 1 is unexplained, and 21 occurred shortly before or during a period of peak influenza activity in each of six influenza seasons. Our findings suggest that this surveillance system is sensitive to communitywide respiratory outbreaks with relatively few false alarms. More work needs to be done to evaluate the sensitivity of this approach for detecting nonrespiratory illness and more localized outbreaks.  相似文献   
3.
A rapid and sensitive enzyme immunoassay (ELISA) was developed for the quantitation of anti-tetanus antibodies. This technique was used to measure antibody levels in the plasma of immunized donors, in human anti-tetanus IgG preparations and in human and mouse hybridomas producing monoclonal antibodies to tetanus toxoid. The assay was capable of detecting antibody levels as low as 5 X 10(-4) IU/ml. By inclusion of an extra step involving antibodies to mouse Ig isotypes, a sandwich enzyme immunoassay (SEI) was developed which permitted determination of the Ig isotype of mouse anti-tetanus antibodies including tetanus-specific mouse monoclonal antibodies. SEI confirmed Protein A-Sepharose fractionation of mouse ascites fluid containing anti-tetanus antibody. The tetanus toxoid-coated plates have a shelf life of at least 1 year.  相似文献   
4.
Hereditary hearing loss (HHL) is a very common disorder. When inherited in an autosomal recessive manner, it typically presents as an isolated finding. Interestingly and unexpectedly, in spite of extreme heterogeneity, mutations in one gene, GJB2, are the most common cause of congenital severe-to-profound deafness in many different populations. In this study, we assessed the contributions made by GJB2 mutations and chromosome 13 g.1777179_2085947del (the deletion more commonly known as del (GJB6-D13S1830) that includes a portion of GJB6 and is hereafter called Delta(GJB6-D13S1830)) to the autosomal recessive non-syndromic deafness (ARNSD) genetic load in Iran. Probands from 664 different nuclear families were investigated. GJB2-related deafness was found in 111 families (16.7%). The carrier frequency of the 35delG mutation showed a geographic variation that is supported by studies in neighboring countries. Delta(GJB6-D13S1830) was not found. Our prevalence data for GJB2-related deafness reveal a geographic pattern that mirrors the south-to-north European gradient and supports a founder effect in southeastern Europe.  相似文献   
5.
6.
Induction of oxidative stress during the sperm preparation process for assisted reproductive techniques (ART) in men can weaken sperm parameters. Vitamin E (VE) is considered a factor in boosting male fertility. This experimental study (in vitro) aimed to assess the impact of VE supplementation on sperm quality and lipid peroxidation during sperm sampling at different times. For this mention, semen samples were collected from 50 asthenoteratozoospermic men. Samples were divided into control and test groups for 2, 4 and 6 hr that the test group was incubated with VE (2 mM). In two groups, total motility, progressive motility and viability based on the WHO 2010 criteria were assessed. Moreover, malondialdehyde (MDA) levels were evaluated in each group. In the control group, total and progressive motility and sperm viability were decreased significantly after 2 hr; however, MDA levels were increased significantly after 6 hr. Also, in the test group, sperm parameters were increased significantly after 2 hr, and MDA levels were decreased significantly after 6 hr compared to the control group. In outcome, in vitro VE supplementation may protect spermatozoa from the adverse effect of oxidative stress during sperm preparation via preservation antioxidant processes in normal condition.  相似文献   
7.
In cultured cells, KP544 [2‐amino‐5‐(4‐chlorophenylethynyl)‐4‐(4‐trans‐hydroxycyclohexyl amino) pyrimidine] amplifies differentiation initiated by nerve growth factor (NGF) or cAMP. This report describes the pharmacokinetics, safety, and neuroprotective efficacy of KP544 in rats. After an oral dose of 10 mg/kg KP544 was 25% bioavailable with a plasma half‐life of 1.3 h and brain levels 6‐fold higher than plasma levels at 4 and 8 h post‐dose. In a safety study, daily oral dosing for 30 days at 10 and 100 mg/kg was well tolerated. The favorable pharmacokinetic and safety profiles, together with its amplification of NGF in vitro, prompted evaluation of KP544 in two models involving NGF deficiencies. In the first model, brains were lesioned with intrastriatal injections of quinolinic acid. KP544 at oral doses of 0.02 to 1.0 mg/kg/day almost completely prevented the resulting learning deficits as evaluated using a radial‐arm‐water maze. At the lowest dose, there was a slower onset of functional improvement. These effects were accompanied by reductions (16–34%) in the striatal lesion size that were greatest at the highest dose and comparable to those seen with NGF therapy. The second model involved a peripheral neuropathy induced by taxol that is associated with decreases in NGF. KP544 at oral doses of 0.1–10 mg/kg/day decreased the severity of the neuropathy as measured by caudal nerve conduction velocities (30–70% return to control values). In both models, KP544 had a large therapeutic index suggesting its potential as a new approach for treating clinical disorders involving deficiencies in NGF. Drug Dev. Res. 62:60–70, 2004. © 2004 Wiley‐Liss, Inc.  相似文献   
8.
To inform New York City’s (NYC’s) tobacco control program, we identified the neighborhoods with the highest smoking rates, estimated the burden of second-band smoke exposure, assessed the early response to state taxation, and examined cessation practices. We used a stratified random design to conduct a digit-dialed telephone survey in 2002 among 9,674 New York City adults. Our main outcome measures included prevalence of cigarette smoking, exposure to second-hand smoke, the response of smokers to state tax increases, and cessation practices. Even after controlling for sociodemographic factors (age, racelethnicity, income, education, marital status, employment status, and foreign-born status) smoking rates were highest in Central Harlem and in the South Bronx. Sixteen percent of nonsmokers reported frequent exposure to second-hand smoke at home or in a workplace. Among smokers with a child with asthma, only 33% reported having a no-smoking policy in their homes. More than one fifth of smokers reported reducing the number of cigarettes they smoked in response to the state tax increase. Of current smokers who tried to quit, 65% used no cessation aid. These data were used to inform New York City’s smoke-free legislation, taxation, public education, and a free nicotine patch give-away program. In conclusion, large, local surveys can provide essential data to effectively advocate for, plan, implement, and evaluate a comprehensive tobacco control program. Dr. Mostashari (the guarantor) made substantial contributions to the conception, design, and supervision of this paper, the analysis and interpretation of data, the drafting of the paper, critical revisions of the paper for important intellectual content, and the acquisition of data and funding for this research. Dr. Kerker made substantial contributions to the analysis and interpretation of data, the drafting of the paper and critical revisions of the paper for important intellectual content. Ms. Hajat made substantial contributions to the acquisition of data and critical revisions of the paper for important intellectual content. Dr. Miller made substantial contributions to the conception of this paper and critical revisions of the paper for important intellectual content. Dr. Frieden made substantial contributions to the conception, design, and supervision of this paper and critical revisions of the paper for important intellectual content.  相似文献   
9.
ObjectiveThis study aimed to assess the effect of peer education on the quality of life and self-care behaviors of patients with myocardial infarction.MethodsIn this clinical trial, 70 patients with myocardial infarction meeting the inclusion criteria were assigned to experimental (n = 35) or control (n = 35) groups using block randomization. Patients in the intervention group received two one-hour training sessions on the third day after myocardial infarction during the CCU stay along with routine care. Education intervention was performed by peers. The control group will follow routine care. All patients selected were assessed using McNews' quality of life questionnaire and Miller self-care questionnaire, respectively before the intervention and also one month after discharge. Chi-square and t-test were used to analyze the data.ResultsAfter the intervention, the mean of quality of life and the mean score of self-care behaviors in the experimental group were significantly higher compared to the control group.ConclusionsAccording to the results, to improve the quality of life and promote the self-care behaviors in such patients, using peer education along with healthcare professionals is recommended.Practice ImplicationThis patient education approach had a significant impact on quality of life and self-care behavior.  相似文献   
10.
Many multiple sclerosis (MS) patients with normal pure tone threshold suffer from difficulties in their hearing especially speech perception in background noise, which is possibly because of incompetence of central auditory processing in this group. Three audiologic tests including gap in noise test (GIN), duration pattern sequence test (DPST) and word discrimination score (WDS) were used for comparing a number of aspects of central auditory processing between patients with MS and normal subjects. Approximate threshold and percent of correct answers in GIN test, percent of correct answers in DPST test and monosyllabic discrimination in WDS test were obtained through cross-sectional non-invasive study conducted on 26 subjects with relapsing-remitting multiple sclerosis who had mean age of 28.9 (SD 4.1) years, and 26 18–40-year-old ones with normal hearing and mean age of 27.7 (SD 5.2). Results of this study demonstrate increased approximate threshold and reduction of percent of correct answers obtained from GIN test in patients with multiple sclerosis (Pv = 0.0001). Furthermore in patients with MS, the average of correct answers in DPST was lower than normal subjects and finally performance of MS subjects in WDS test in quiet environment was correlated with GIN threshold (r = ?/624, Pr = /003). Results of the present study showed that patients with MS had defect in aspects of central auditory processing consisting of temporal resolution, auditory pattern and the memory for auditory task and difficulty in discrimination of speech in noisy environment that are related to the involvement of central nervous system.  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