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   1678篇
  免费   92篇
  国内免费   3篇
耳鼻咽喉   7篇
儿科学   34篇
妇产科学   44篇
基础医学   256篇
口腔科学   114篇
临床医学   112篇
内科学   381篇
皮肤病学   68篇
神经病学   120篇
特种医学   18篇
外科学   210篇
综合类   25篇
一般理论   2篇
预防医学   171篇
眼科学   17篇
药学   110篇
中国医学   27篇
肿瘤学   57篇
  2023年   8篇
  2022年   37篇
  2021年   55篇
  2020年   34篇
  2019年   59篇
  2018年   62篇
  2017年   34篇
  2016年   51篇
  2015年   54篇
  2014年   82篇
  2013年   89篇
  2012年   132篇
  2011年   147篇
  2010年   97篇
  2009年   72篇
  2008年   104篇
  2007年   81篇
  2006年   89篇
  2005年   92篇
  2004年   70篇
  2003年   72篇
  2002年   48篇
  2001年   13篇
  2000年   20篇
  1999年   20篇
  1998年   8篇
  1997年   4篇
  1996年   3篇
  1995年   4篇
  1994年   5篇
  1993年   5篇
  1992年   14篇
  1991年   6篇
  1990年   7篇
  1989年   6篇
  1988年   6篇
  1987年   6篇
  1986年   6篇
  1985年   6篇
  1984年   6篇
  1983年   8篇
  1982年   3篇
  1981年   5篇
  1980年   5篇
  1979年   4篇
  1978年   4篇
  1970年   6篇
  1969年   7篇
  1968年   3篇
  1965年   3篇
排序方式: 共有1773条查询结果,搜索用时 15 毫秒
971.
Diabetes mellitus type II, a cause of preclinical left ventricular dysfunction that can progress to cardiac insufficiency ventricular dysfunction in diabetic patients, is attributed to systemic arterial hypertension, or ischemic cardiopathy. Diastolic ventricular dysfunction takes place during the course of diabetes mellitus. The purpose of the present article is to report on the influence of hyperglycemia on the left ventricular diastolic dysfunction independently of dyslipidemia, obesity, and systemic arterial hypertension, usually present in diabetic patients.Left ventricular diastolic function was studied by Doppler echocardiography in asymptomatic type II diabetic patients without ischemic or valvular cardiopathies, cardiomegaly, or systemic arterial hypertension. Two groups of patients were integrated: patients with and without left ventricular diastolic dysfunction, i.e., groups A and B, respectively. Glycemia, cholesterol, triglycerides, and body mass index (BMI) were determined in each subject. Bivariate statistical tests (Student t, chi-square, or Mann-Whitney U tests) were applied to study the influence of the previously mentioned variables on the ventricular diastolic function. To evaluate the influence of hyperglycemia on ventricular diastolic function separately from dyslipidemia, systemic arterial hypertension, and the influence of obesity, logistic regression, and multivariate statistical analysis were applied.Independently of dyslipidemia and obesity, a relationship was found between hyperglycemia and diastolic dysfunction of the left ventricle in patients belonging to group A (p <0.05, odds ratio [OR] 12.1). No statistical significance was found between glycemia and the diastolic function of the left ventricle in group B patients.Even in type II diabetic patients without cardiopathy, uncontrolled hyperglycemia provokes diastolic left ventricular dysfunction.  相似文献   
972.
OBJECTIVE: Previous studies have indicated varying rates of HIV infection among labor migrants to the United States of America. Most of these studies have been conducted with convenience samples of farmworkers, thus presenting limited external validity. This study sought to estimate the prevalence of HIV infection and risk factors among Mexican migrants traveling through the border region of Tijuana, Baja California, Mexico, and San Diego, California, United States. This region handles 37% of the migrant flow between Mexico and the United States and represents the natural port of entry for Mexican migrants to California. METHODS: From April to December 2002 a probability survey was conducted at key migrant crossing points in Tijuana. Mexican migrants, including ones with a history of illegal migration to the United States, completed an interview on HIV risk factors (n = 1 429) and an oral HIV antibody test (n = 1,041). RESULTS: Despite reporting risk factors for HIV infection, none of the migrants tested positive for HIV. CONCLUSIONS: Our findings contrast with previous estimates of HIV among labor migrants in the United States that were based on nonprobability samples. Our findings also underline the need for early HIV prevention interventions targeting this population of Mexican migrants.  相似文献   
973.
974.
A brief summary is presented of the epidemiological, embryological, clinical, and etiological aspects of myelomeningocele. The natural history of this disease is reviewed, as are the implications of present-day treatment. An analysis is made of the cost of overall treatment, including neurological, orthopedic and urological surgery, as well as physical and psychological rehabilitation and specialized educational therapy. The costs are high, both monetarily and from the viewpoint of social handicaps. The author's personal experience is analyzed. The outcome of treatment is poor, probably due to the economic limits which do not allow full treatment. Several questions are asked: Should these children be operated upon? Which children should be operated upon? Who must bear the costs of treatment? The author gives his point of view concerning these questions.  相似文献   
975.
976.
977.
978.
Despite tuberculosis resurgence and extensive dendritic cell (DC) research, there are no in vivo studies evaluating DC within regional lymphoid tissue during airways infection with virulent Mycobacterium tuberculosis (Mtb) H37Rv. Using DC-specific antibodies, immunocytochemistry, flow cytometry and Ziehl-Neelsen (ZN) for bacilli staining, we searched for Mtb and DC changes within mediastinal lymph nodes, after intratracheal (ITT) inoculation of virulent Mtb. ZN and immunocytochemistry in frozen and paraffin sections of mediastinal lymph nodes identified Mtb until day 14 after ITT inoculation, associated with CD11c(+) and Dec205(+) DC. Analysing CD11c, MHC-CII, and Dec205 combinations by flow cytometry in MLN suspensions revealed that CD11c(+)/MHC-CII(+) and CD11c(+)/Dec205(+) DC did not increase until day 14, peaked on day 21, and sharply declined by day 28. No changes were seen in control, saline-inoculated animals. The costimulatory molecules evaluated in CD11c(+) DCs followed a similar trend; the CD80 increase was negligible, slightly surpassed by CD40. CD86 increased earlier and the three markers peaked at day 21, declining by day 28. While antigen-specific proliferation was not evident for MLN CD4(+) T cells at 2 weeks postinfection, delayed-type hypersensitivity responses upon ITT inoculation revealed that, as early as day 3 and 7, both the priming and peripheral systemic immune responses were clearly established, persisting until days 14-21. While airways infection with virulent Mtb triggers an early, systemic peripheral response maintained for three weeks, this seems dissociated from regional events within mediastinal lymph nodes, such as antigen-specific T-cell reactivity and a delay in the influx and local activation of DC.  相似文献   
979.
Lack of physical activity is a known determinant of obesity. Unfortunately, children become less and less active as they reach and progress through adolescence. This behavior leads to detrimental effects on body composition and other components of health-related physical fitness. Various types of exercise and activities have different effects on fitness, body composition, and metabolic state. For a physician to recommend activities or sports and exercise type, he or she should examine and discuss the patients fitness and physique goals to maintain their enthusiasm and promote lifelong physical activity benefits.  相似文献   
980.
Jalap, a pre-Hispanic herbal remedy still considered a useful laxative, is an ingredient in some over-the-counter products sold by herbalists in contemporary Mexico. The purgative crude drugs are prepared from the roots of several morning glories species which all have been identified as members of the Ipomoea genus (Convolvulaceae). Their incorporation as therapeutical agents into Europe is an outstanding example of the assimilation of botanical drugs from the Americas as substitutes for traditional Old World remedies. Phytochemical investigations on the resin glycosides, main constituents of these drugs, were initiated during the second half of the XIX century; however, the structures of their active ingredients had remained poorly known, and still are for some members of these purgative root species. Modern analytical techniques with higher resolution capabilities (HPLC) for the isolation of the active principles of these crude drugs used in conjunction with powerful spectroscopic methods (high field NMR) have facilitated the investigation of these relevant, to the herbal product market, convolvulaceous species during the last decade. The advantages and limitations of theses techniques will be discussed. This review will also describe the ethnobotanical information associated with the Mexican morning glory species and how the traditional usages of these plants have played an important role in the selection of these materials for chemical studies. Little is as yet known about either the mechanism of purge action caused by the resin glycosides or the ecological significance of these same compounds for the producing plants. Over the five centuries of Mexican herbal medicine, one hundred years of phytochemistry has only partially elucidated the active ingredients of the jalap roots but has exemplified how to further contemporary drug discoveries through the investigation of those plants traditionally held to be economically and medicinally important in developing countries.  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