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   8734篇
  免费   974篇
  国内免费   29篇
耳鼻咽喉   86篇
儿科学   451篇
妇产科学   166篇
基础医学   1023篇
口腔科学   126篇
临床医学   989篇
内科学   1854篇
皮肤病学   206篇
神经病学   635篇
特种医学   570篇
外科学   1352篇
综合类   217篇
一般理论   2篇
预防医学   853篇
眼科学   155篇
药学   492篇
  2篇
中国医学   6篇
肿瘤学   552篇
  2023年   84篇
  2022年   51篇
  2021年   114篇
  2020年   120篇
  2019年   137篇
  2018年   189篇
  2017年   138篇
  2016年   140篇
  2015年   190篇
  2014年   280篇
  2013年   350篇
  2012年   370篇
  2011年   422篇
  2010年   284篇
  2009年   256篇
  2008年   402篇
  2007年   403篇
  2006年   386篇
  2005年   391篇
  2004年   352篇
  2003年   307篇
  2002年   295篇
  2001年   244篇
  2000年   259篇
  1999年   205篇
  1998年   139篇
  1997年   156篇
  1996年   173篇
  1995年   142篇
  1994年   117篇
  1993年   134篇
  1992年   184篇
  1991年   183篇
  1990年   172篇
  1989年   166篇
  1988年   154篇
  1987年   164篇
  1986年   139篇
  1985年   160篇
  1984年   97篇
  1983年   95篇
  1982年   82篇
  1981年   72篇
  1980年   47篇
  1979年   64篇
  1978年   48篇
  1977年   60篇
  1976年   62篇
  1975年   60篇
  1971年   45篇
排序方式: 共有9737条查询结果,搜索用时 15 毫秒
71.
Primary myxoid liposarcoma of the orbit.   总被引:1,自引:1,他引:0       下载免费PDF全文
Orbital liposarcoma is a rare and usually unsuspected neoplasm. Over a five-year period three female patients aged 22, 71, and 77 years presented with primary myxoid liposarcoma of the orbit. The management of one patient was complicated by a history of orbital decompression for suspected thyroid eye disease. The tumour infiltrates locally beyond a deceptive pseudocapsule, and surgery has to be radical to be effective.  相似文献   
72.
Gallbladder dyskinesia in chronic acalculous cholecystitis   总被引:4,自引:0,他引:4  
To test the hypothesis that there is an early stage of cholesterol gallstone formation in man characterized by symptoms of chronic cholecystitis, poor gallbladder emptying, and biliary cholesterol crystals, we studied cholecystokinin-stimulated gallbladder emptying by DISIDA scintigraphy and examined bile for cholesterol crystals in symptomatic patients with normal oral cholecystography and gallbladder sonography. Of 36 patients studied, 16 had biliary cholesterol crystals; their mean 30-min gallbladder ejection fraction was 25.9±14.8%. Among the 20 patients without crystals, the mean ejection fraction was 60.3±23.3%. Fifteen patients, 11 with crystals and four without, had cholecystectomy because of persistent symptoms. All with crystals preoperatively and three without had chronic cholecystitis histologically. One patient without crystals had normal histology. We conclude that poor gallbladder contractility, well-established as an etiologic factor in animal models of cholesterol cholelithiasis, is now linked to acalculous cholecystitis, an early stage of human cholesterol cholelithiasis.  相似文献   
73.
74.
In previous studies, we have demonstrated that chronic administration of morphine or cocaine produces some common biochemical adaptations in the ventral tegmental area (VTA) and nucleus accumbens (NAc), components of the mesolimbic dopamine system implicated in the reinforcing actions of these and other drugs of abuse. Since this neural pathway is also implicated in the reinforcing actions of ethanol, it was of interest to determine whether chronic ethanol exposure results in similar biochemical adaptations. Indeed, as seen for chronic morphine and cocaine treatments, we show here that chronic ethanol treatment increased levels of tyrosine hydroxylase and glial fibrillary acidic protein immunoreactivity, and decreases levels of neurofilament protein immunoreactivity, in the VTA. Also like morphine and cocaine, ethanol increases levels of cyclic AMP-dependent protein kinase activity in the NAc. These actions of ethanol required long-term exposure to the drug, and were in most cases not seen in the substantia nigra or caudate-putamen, components of the nigrostriatal dopamine system studied for comparison. Altered levels of tyrosine hydroxylase in catecholaminergic cells frequently reflect altered states of activation of the cells. Moreover, increasing evidence indicates that ethanol produces many of its acute effects on the brain by regulating NMDA glutamate and GABA receptors. We therefore examined the influence of chronic ethanol treatment on levels of expression of specific glutamate and GABA receptor subunits in the VTA. It was found that long-term, but not short-term, ethanol exposure increased levels of immunoreactivity of the NMDARl subunit, an obligatory component of NMDA glutamate receptors, and of the Glu Rl subunit, a component of many AMPA glutamate receptors; but at the same time, long-term ethanol exposure decreased immunoreactivity levels of the α1 subunit of the GABAA receptor complex. These changes are consistent with an increased state of activation of VTA neurons inferred from the observed increase intyrosine hydroxylase (TH) expression. These results demonstrate that chronic ethanol exposure results in several biochemical adaptations in the mesolimbic dopamine system, which may underlie prominent changes in the structural and functional properties of this neural pathway related to alcohol abuse and alcoholism. © 1995 Wiley-Liss, Inc.  相似文献   
75.
This paper examines medical malpractice law as it applies to medically necessary oral health care. The basic legal concepts and reported cases involving medically necessary oral health care are reviewed. It is concluded that dental professionals and consumer advocates must advance their educational and legislative advocacy efforts so that health professional colleagues and the public will become aware of the importance of these services and insurers will routinely include coverage of medically necessary oral health care in their medical and dental policies. While failure to provide medically necessary oral health care can be violative of patient rights and legally actionable, medical malpractice litigation should always be the behavior modifier of last resort.  相似文献   
76.
This study investigated the attitudes of medical students towards psychiatry, both as a subject on the medical curriculum and as a career choice. Three separate questionnaires previously validated on medical student populations were administered prior to and immediately following an 8-week clinical training programme. The results indicate that the perception of psychiatry was positive prior to clerkship and became even more so on completion of training. On completion of the clerkship, there was a rise in the proportion of students who indicated that they might choose a career in psychiatry. Attitudes toward psychiatry correlated positively with the psychiatry examination results. Those that intended to specialise in psychiatry achieved significantly higher examination scores in the psychiatry examination.  相似文献   
77.
Objectives. The management of intractable urinary incontinence in the patient with cloacal or bladder exstrophy/epispadias, failed bladder neck plasty, or failed augmentation cystoplasty remains a surgical challenge. The myofascial wrap, a modification of the rectus fascial wrap, was developed to treat intractable urinary incontinence due to sphincteric incompetence in these problematic cases. A full-thickness, vascularized pedicle of anterior rectus sheath, rectus abdominis muscle, and posterior rector sheath is incorporated into a bladder neck wrap to provide support, mucosal coaptation, and active muscular tone.Methods. Eight patients (5 females and 3 males) with total urinary incontinence due to sphincteric incompetence underwent the myofascial wrap. Urinary tract pathology included cloacal exstrophy (2), female epispadias (2), classic bladder exstrophy (1), male epispadias (1), myelomeningocele (1), and a pelvic tumor (1). The procedure is performed by harvesting a full-thickness strip of pedicled rectus muscle along with the anterior and posterior fascial sheaths. The strip is passed underneath and then over the bladder neck in a near 360° wrap. The free end of the wrap is anchored into the pubic bone in an ipsilateral subperiosteal pouch.Results. Six of the 8 patients are completely continent, and 2 patients void spontaneously without the need for catheterization.Conclusions. The myofascial wrap provides support, mucosal coaptation, and muscular tone to an incompetent sphincter and bladder neck. Favorable results in a very difficult population of pediatric patients warrant its continued use.  相似文献   
78.
The feasibility of a centralized menu and the effectiveness of an "offer vs. serve" option within a self-serve, choice menu lunch program at the elementary school level were determined. Student trays (no. = 370/day) were visually evaluated for foods chosen and consumed. The same 1-week menu was served at two urban Southern schools. One represented a high-poverty-area, all-black-student school and the other represented a middle-income-area school with a white to black student ratio of 3:1. Students were able to choose the required USDA minimal number of three foods, and 66% of the foods selected were similar at the two schools, demonstrating that a centralized menu was feasible. Three-fourths of the students were able to choose more than 75% of one-third of the RDA for all nutrients except pyridoxine and ascorbic acid at both schools and iron at the high-poverty school. Twenty-five percent or more of the students did not consume 75% of one-third the Recommended Dietary Allowance for thiamin, vitamin B-6, ascorbic acid, iron, and magnesium at either school or of niacin and vitamin A at the middle-income school. Overall plate waste was 12.9%, with younger children wasting more food than older children and more waste in the middle-income than the high-poverty school. In general, the "offer vs. serve" was an effective option.  相似文献   
79.
Impaired conditioned taste aversion learning in APP transgenic mice   总被引:8,自引:0,他引:8  
Cognition in transgenic mouse models of Alzheimer's disease (AD) has been predominantly characterized in explicit spatial orientation tasks. However, dementia in AD encompasses also implicit memory systems. In the present study a line of transgenic mice (TgCRND8) encoding a double mutated allele of the human amyloid precursor protein (APP) genes was evaluated in an implicit associative learning task of conditioned taste aversion (CTA). CTA is a form of Pavlovian classical conditioning, in which a mouse learns to avoid a novel taste of saccharine (conditioned stimulus) paired with an experimentally induced (systemic injection of lithium chloride) nausea (unconditioned stimulus). In contrast to conditioned non-Tg mice, TgCRND8 APP mice developed weaker aversion against saccharine and quickly increased its consumption in repeated tests. These results indicate that TgCRND8 mice show a significant impairment not only in explicit spatial memory, as has been previously shown [Nature 408 (2000) 979], but also in implicit memory. Control experiments confirmed that TgCRND8 and non-Tg mice had comparable taste sensitivities in response to appetitive as well as aversive tastes. The study suggests that the CTA paradigm can be a sensitive tool to evaluate deficits in implicit associative learning in APP transgenic mouse models of AD.  相似文献   
80.
The presence of p24 core antigen in the serum of individuals with human acquired immunodeficiency syndrome has been used as one of the important prognostic markers of HIV-1 infection and also as an end point in evaluating antiviral drugs and vaccines. Unfortunately the majority of p24 antigen present in serum exists as an antigenantibody complex and is not detected with the commercial kits currently available to measure p24 antigen. In this study, we report a simple procedure utilizing treatment of serum samples with glycine buffer (pH 1.85) to dissociate antigen-antibody complexes prior to assaying for p24 antigen. A 300% increase in the number of p24-reactive samples and a 3- to 12-fold increase in the quantity of antigen detected were observed when samples were pretreated with 1.5M glycine buffer (pH 1.85) for 1 hr. Glycine treatment of samples did not result in nonspecific positive tests and samples previously shown to be reactive remained positive. In reconstruction experiments the release of antigen was found to be inversely proportional to the amount of p24 antibody present in the serum. The percentage of HIV-1-infected patients positive for p24 antigen was clearly a function of CD4 count. Forty-nine percent of patients with more than 500 CD4 cells and 100% of patients with less than 200 CD4 were p24 positive. The improved sensitivity for detection of p24 provided by this procedure enhances our understanding of the pathogenesis of AIDS by showing that the majority of patients with HIV-1 infection is p24 positive and facilitates the analysis of data obtained in clinical trials involving anti-HIV compounds.  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