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   9010篇
  免费   567篇
  国内免费   44篇
耳鼻咽喉   144篇
儿科学   246篇
妇产科学   346篇
基础医学   1380篇
口腔科学   187篇
临床医学   799篇
内科学   1689篇
皮肤病学   105篇
神经病学   799篇
特种医学   447篇
外科学   937篇
综合类   84篇
一般理论   3篇
预防医学   824篇
眼科学   94篇
药学   816篇
中国医学   15篇
肿瘤学   706篇
  2021年   89篇
  2020年   60篇
  2019年   101篇
  2018年   136篇
  2017年   75篇
  2016年   107篇
  2015年   136篇
  2014年   194篇
  2013年   290篇
  2012年   395篇
  2011年   463篇
  2010年   244篇
  2009年   234篇
  2008年   422篇
  2007年   448篇
  2006年   438篇
  2005年   457篇
  2004年   448篇
  2003年   422篇
  2002年   364篇
  2001年   209篇
  2000年   172篇
  1999年   185篇
  1998年   130篇
  1997年   145篇
  1996年   148篇
  1995年   124篇
  1994年   118篇
  1993年   124篇
  1992年   157篇
  1991年   191篇
  1990年   149篇
  1989年   137篇
  1988年   145篇
  1987年   112篇
  1986年   114篇
  1985年   119篇
  1984年   121篇
  1983年   112篇
  1982年   83篇
  1981年   86篇
  1980年   88篇
  1979年   86篇
  1978年   69篇
  1977年   58篇
  1976年   73篇
  1975年   63篇
  1974年   81篇
  1973年   78篇
  1972年   55篇
排序方式: 共有9621条查询结果,搜索用时 15 毫秒
61.
OBJECTIVE: To evaluate an enriched prenatal intervention program designed to reduce the risk of low birth weight. STUDY SETTING: Freestanding community-based prenatal intervention project located in a poor inner-city community, serving mostly African American women. STUDY DESIGN: All women less than 29 weeks pregnant were eligible to participate. They were compared to women who lived in neighborhoods with similar rates of poverty. DATA COLLECTION: The birth certificate was the source of data on maternal age, education, marital status, timing and frequency of prenatal care attendance, parity, gravidity, prior pregnancy terminations, fetal and child deaths, and birth weight. PRINCIPAL FINDINGS: Thirty-eight percent of the women who delivered live-born infants in the study area participated in the program. There were no differences in low- and very low birthweight rates in the study and comparison groups. In a secondary analysis comparing participants and nonparticipants in the study census tracts, participants were at higher risk for low and very low birth weight, and they adhered more closely to the schedule of prenatal visits than nonparticipants. Low- and very low birthweight rates were lower among participants than among nonparticipants and comparison women. CONCLUSION: The Better Babies Project did not have an effect on the overall low- and very low birthweight rates in the study census tracts. This was probably due to the low participation rates and the high population mobility.  相似文献   
62.
A 62-yr-old woman was evaluated for a 2-wk history of regurgitation and weight loss. Radiologic studies demonstrated a stenotic region in the distal third of the esophagus. Multiple endoscopic biopsies were nondiagnostic. Esophagectomy and esophagogastrostomy revealed a diffusely infiltrating adenocarcinoma ("linitis plastica") of the distal esophagus, sparing the gastroesophageal junction and stomach. Despite the absence of metastatic disease at laparotomy, the patient developed metastases unresponsive to chemotherapy. The pathologic, radiographic, and endoscopic findings are consistent with primary linitis plastica of the esophagus.  相似文献   
63.
Sonography detected a paraaortic pulsatile tubular mass in a patient 10 years after “stump” nephrectomy, which was subsequently confirmed as a renal artery-renal vein fistula by computed tomography, angiography, and laparotomy.  相似文献   
64.
Over a period of two years, five patients with sleep paralysis referred themselves to four family practices in Israel serving a population of 6800. None of the patients suffered from daytime sleep attacks or cataplexy and all were from the oriental (sephardi) community. The two who were tissue typed had HLA haplotypes different from those which are exclusively associated with narcolepsy and one of them who also underwent polysomnography had a normal tracing. There was considerable delay in consulting a physician despite the physical and mental anguish caused by the disorder and some improvement was noted once the diagnosis was explained. The serious nature of the components of the differential diagnosis - myocardial infarction, seizure disorder, cardiac arrest, anaesthetic accident - makes it important that sleep paralysis be more widely recognized.  相似文献   
65.
African tick-bite fever, caused by Rickettsia africae, is the most common tick-borne rickettsiosis in sub-Saharan Africa. Mediterranean spotted fever due to Rickettsia conorii also occurs in the region but is more prevalent in Mediterranean countries. Using microimmunofluorescence, we compared the development of immunoglobulin G (IgG) and IgM titers in 48 patients with African tick-bite fever and 48 patients with Mediterranean spotted fever. Doxycycline treatment within 7 days from the onset of disease significantly prevented the development of antibodies to R. africae. In patients with African tick-bite fever, the median times to seroconversion with IgG and IgM were 28 and 25 days, respectively, after the onset of symptoms. These were significantly longer by a median of 6 days for IgG and 9 days for IgM than the times for seroconversion in patients with Mediterranean spotted fever (P < 10−2). We recommend that sera collected 4 weeks after the onset of signs of patients with suspected African tick-bite fever should be used for the definitive serological diagnosis of R. africae infections.  相似文献   
66.
We report on an8-month-old girl with a de novo 5q/6q autosomal translocation with loss of the distal part of the long arm of chromosome 6 (6q23.3→6qter); clinical manifestations are peculiar craniofacial stigmata, truncal obesity and persisting hypotonia. The similarity with a previously reported patient with 6q interstitial deletion is discussed.  相似文献   
67.
A boy aged 8 years, 10 months presented with refractory anemia. Bone marrow investigation revealed monolobular megakaryocytes. Cytogenetic analysis showed a clonal abnormality: 46, XY, del(5)(q14q32). This is the youngest individual ever reported with this disorder. A year after diagnosis, while on treatment with human recombinant erythropoietin, the bone marrow showed an excess of blasts. No bone marrow donor could be found. Transformation to acute myelomonocytic leukemia occurred 3 months later. In spite of intensive chemotherapy, the child died of progressive disease with massive splenomegaly and jaundice. The case illustrates that the 5q- syndrome can occur de novo in children. The outcome in this child was poor, which may reflect a difference from the adult 5q- syndrome or may possibly be related to the erythropoietin the child received.  相似文献   
68.
Microbial infections,immunomodulation, and drugs of abuse   总被引:12,自引:0,他引:12  
The use of recreational drugs of abuse has generated serious health concerns. There is a long-recognized relationship between addictive drugs and increased levels of infections. Studies of the mechanisms of actions of these drugs became more urgent with the advent of AIDS and its correlation with abused substances. The nature and mechanisms of immunomodulation by marijuana, opiates, cocaine, nicotine, and alcohol are described in this review. Recent studies of the effects of opiates or marijuana on the immune system have demonstrated that they are receptor mediated, occurring both directly via specific receptors on immune cells and indirectly through similar receptors on cells of the nervous system. Findings are also discussed that demonstrate that cocaine and nicotine have similar immunomodulatory effects, which are also apparently receptor mediated. Finally, the nature and mechanisms of immunomodulation by alcohol are described. Although no specific alcohol receptors have been identified, it is widely recognized that alcohol enhances susceptibility to opportunistic microbes. The review covers recent studies of the effects of these drugs on immunity and on increased susceptibility to infectious diseases, including AIDS.  相似文献   
69.
Advances in genetics create increasing possibilities of diagnosing and preventing genetic disease. In most countries, the community is poorly informed about the role of genetic factors in human disease and about genetic testing and its social, emotional, and ethical implications. School education about genetics may improve this situation. Students are, of course, the adults of the future and the potential users of the new genetic tests. To gain further insight into the perception of genetic risk of adolescents and their perception of the new genetic techniques and as a starting point for setting up an adequate information campaign in Flanders, we assessed the opinions and beliefs of students with regard to health, genetic diseases, genetic risk, and genetic testing.

A standardised interview and questionnaire were administered within the scope of the two yearly medical check up of 166 fifth grade students. They were randomly selected from the group of all fifth grade high school students in seven different schools.

This paper focuses on the attitudes of adolescents towards obtaining genetic information, towards prenatal diagnosis and pregnancy termination. Adolescents in Flanders are interested in being informed about genetic risks and genetic diseases and in making use of prenatal diagnosis because they want to make informed reproductive decisions in the future and to be emotionally prepared for the birth of an affected child. They adopt a critical attitude towards pregnancy termination. The association between these attitudes and several relevant factors was investigated. This showed significant correlations between some attitudes and general health related prevention, perceived burden of genetic diseases, the importance of the value “own health”, the perceived role of society, and the regularity of religious practice. Some points for special attention were formulated with regard to information campaigns for adolescents.

  相似文献   
70.
Intima formation in vessels, spontaneous or experimentally induced, is generally characterized by the presence of longitudinally orientated smooth muscle cells (LSMC). During an experiment of neo-intima induction in carotid arteries in rabbits, by application of a nonconstrictive silastic cuff, a study was performed to investigate the presence of LSMC in the systemic and pulmonary circulations, in both elastic and muscular arteries. Three patterns could be distinguished: intimai cushions in muscular arteries, single or small groups of LSMC in the intima in elastic and larger muscular arteries, and intra-medially located layers or columns of LSMC in the aorta, the pulmonary artery, at the bifurcation of the aorta and around orifices of branches. In order to understand this peculiar orientation a biomechanical approach was used: this showed that near the lumen the circumferential stress is 4.5 times higher than the longitudinal. Because the cell surface of the smooth muscle cells exposed to this stress per unit vessel length is much less in the longitudinal than in the circular direction we conclude that the LSMC align in the direction which allows them to cope most effectively with the mechanical stresses.  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