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   1479篇
  免费   199篇
  国内免费   12篇
耳鼻咽喉   21篇
儿科学   113篇
妇产科学   28篇
基础医学   161篇
口腔科学   64篇
临床医学   195篇
内科学   310篇
皮肤病学   45篇
神经病学   68篇
特种医学   179篇
外科学   244篇
综合类   50篇
一般理论   1篇
预防医学   66篇
眼科学   28篇
药学   27篇
中国医学   5篇
肿瘤学   85篇
  2023年   4篇
  2022年   9篇
  2021年   25篇
  2020年   9篇
  2019年   21篇
  2018年   51篇
  2017年   55篇
  2016年   46篇
  2015年   42篇
  2014年   54篇
  2013年   79篇
  2012年   56篇
  2011年   57篇
  2010年   77篇
  2009年   69篇
  2008年   50篇
  2007年   62篇
  2006年   47篇
  2005年   39篇
  2004年   23篇
  2003年   17篇
  2002年   26篇
  2001年   32篇
  2000年   24篇
  1999年   21篇
  1998年   64篇
  1997年   57篇
  1996年   57篇
  1995年   54篇
  1994年   32篇
  1993年   44篇
  1992年   32篇
  1991年   37篇
  1990年   34篇
  1989年   24篇
  1988年   46篇
  1987年   34篇
  1986年   26篇
  1985年   20篇
  1984年   21篇
  1983年   21篇
  1982年   9篇
  1981年   18篇
  1980年   10篇
  1979年   9篇
  1978年   4篇
  1977年   12篇
  1976年   10篇
  1975年   6篇
  1974年   5篇
排序方式: 共有1690条查询结果,搜索用时 15 毫秒
101.
The pathology was reviewed of the early deaths identified from the first 50 neonates treated with extracorporeal membrane oxygenation (ECMO) during its introduction to the UK. Fifteen neonates died during or shortly after ECMO between August 1989 and June 1992. Data on 12 are presented (three did not have a postmortem examination). The clinical diagnoses at referral for ECMO were as follows: persistent pulmonary hypertension of the newborn (six infants), primary congenital pneumonia (one infant), community acquired pneumonia (two infants), birth asphyxia (one infant), respiratory distress syndrome (one infant), and meconium aspiration syndrome (one infant). In our group, at necropsy, five had significant haemorrhage (three intracranial, one pulmonary, one pericardial and intraventricular). Three of five infants with evidence of haemorrhage also had signs of sepsis. Six infants had evidence at necropsy of systemic sepsis, five showed evidence of severe anoxic brain injury, and four infants had cerebellar haemorrhages. Three infants had evidence of myocardial ischaemia. It is difficult to discriminate between the relative influence of the primary diagnosis, the mode of treatment, and the severity of presentation in the genesis of this pathology. It is likely that the extent and severity of some of the findings represent a pathological progression that would have been interrupted by the death of the patient, had ECMO not been instituted.  相似文献   
102.
BACKGROUND: Several studies have reported positive associations between environmental tobacco smoke (ETS) and increased risk of breast cancer. However, studies of active smoking and risk of breast cancer are equivocal and in general do not support a positive association. To try to resolve this paradox, we examined the association between breast cancer mortality and potential ETS exposure from spousal smoking in an American Cancer Society prospective study of U.S. adult women. METHODS: We assessed breast cancer death rates in a cohort of 146 488 never-smoking, single-marriage women who were cancer free at enrollment in 1982. Breast cancer death rates among women whose husbands smoked were compared with those among women married to men who had never smoked. Cox proportional hazards modeling was used to control for potential risk factors other than ETS exposure. RESULTS: After 12 years of follow-up, 669 cases of fatal breast cancer were observed in the cohort. Overall, we saw no association between exposure to ETS and death from breast cancer (rate ratio [RR] = 1.0; 95% confidence interval [CI] = 0.8-1.2). We did, however, find a small, not statistically significant increased risk of breast cancer mortality among women who were married before age 20 years to smokers (RR = 1. 2; 95% CI = 0.8-1.8). CONCLUSIONS: In contrast to the results of previous studies, this study found no association between exposure to ETS and female breast cancer mortality. The results of our study are particularly compelling because of its prospective design as compared with most earlier studies, the relatively large number of exposed women with breast cancer deaths, and the reporting of exposure by the spouse rather than by proxy.  相似文献   
103.
104.
Summary Forty three patients, admitted to the department of Neurological Surgery for management of central nervous system tumours, were studied pre-operatively for serum myelin basic protein immunoreactivity as a marker of central nervous system lesion and for circulating immunoglobulins and complement (C3) levels. Myelin basic protein concentration did not appear to correlate with tumour type or grade. Serum immunoglobulin levels were found to be within the normal range but the mean IgM level was significantly higher in the glioma group when compared with meningiomas.  相似文献   
105.
106.
Summary— With respect to the heart, the prolonged existence of hypertension, both in man and in experimental animals is predominantly characterized by an increase in left ventricular myocardial mass. In this process, the autonomic nervous system plays an important role. Although endogenous catecholamine stimulation of the heart is mainly exerted via the β-adrenoceptors, in several mammalian species, the stimulation of cardiac α-adrenoceptors also mediates positive inotropic actions. We investigated the functional responses of isolated hypertrophied hearts taken from spontaneously hypertensive rats (SHR) and rats with an induced aortic stenosis (ASR) to various α1-adrenoceptor agonists and compared them with those from age matched Wistar Kyoto (WKY) and "sham" operated controls. Accordingly, we studied the functional response to: methoxamine (α1), cirazoline (α1) and phenylephrine (α1 > β1). The inotropic response to the α1-adrenoceptor agonists cirazoline and methoxamine proved to be significantly weaker in hypertrophied hearts from SHR and ASR than in non-hypertrophied hearts from WHY and "sham" operated controls ( p < 0.05). The inotropic response to phenylephrine remained intact in hypertrophied myocardial tissue. However, it was significantly reduced when the hearts were pre-treated with the intracellular Ca2+-antagonists ryanodine and TMB-8. These findings show that the mechanism of sarcolemmal Ca2+ release, activated by phenylephrine, is still intact in the hypertrophied myocardial cell. In conclusion, these data show that cardiac hypertrophy, be it of genetical or mechanical origin, leads to a reduced response of the isolated heart to α1-adrenoceptor stimulation.  相似文献   
107.
There is disagreement among authors as to what criteria are most reliable in assessing postnatal fetal age. A comparison–for objectivity, accuracy, and frequency of use– of specific criteria was made using three independent examiners at different educational levels: a second-year medical student, a perinatal nurse practitioner, and a pediatrics resident. It was shown that trained examiners develop favorite criteria which differ among examiners and thus sacrifice accuracy; however, accurate assessment of fetal age can be accomplished by an examiner with minimum clinical knowledge.  相似文献   
108.
We have developed an improved semiconductor recording probe for monitoring motility of the upper small intestine in humans. The probe consists of six ultraminiature silicon pressure sensors spaced 10 cm apart and encased in a flexible polyurethane sheath. The probe is small [2.67 mm (8F) diameter], is easily passed transnasally, and is tolerated by patients for prolonged recording periods (24–36 hr) with a minimum of discomfort. The initial semiconductor and catheter material were those designed for use in the cardiovascular system, but they proved to be easily damaged by gastric acid and enzymes. After improvement of this probe, we now have recordings from more than 100 patients for an approximate total of 6000 hr of recording time. The improved probe is a durable recording device that facilitates the investigation of motility of the small intestine in humans in health and disease.This study was supported by funds from the Medical Research Service of the Veterans Administration and by National Institutes of Health Clinical Research Center grant RR-82.  相似文献   
109.
Lally BE  Haffty BG  Moran MS  Colasanto JM  Higgins SA 《Cancer》2005,103(11):2236-2240
BACKGROUND: The current study was undertaken to determine the potential advantage associated with complete removal of suspicious or indeterminate calcifications (SIC) before the initiation of irradiation as part of breast conservation therapy (BCT). METHODS: Of 2045 patients treated with BCT at Yale University School of Medicine (New Haven, Connecticut) and satellite facilities before 2002, 111 women, included 3 patients with bilateral disease, had a postexcision preirradiation mammogram (PREMAMMO) to evaluate residual SIC. Thus, 114 breasts were at risk for local disease recurrence. Seventy-five breasts at risk had no residual SIC and proceeded to undergo radiotherapy (XRT) without further surgery or mammography. Of the remaining 39 breasts at risk, only 3 underwent a PREMAMMO with documented removal of all calcifications (DRC). Thirty-six breasts at risk proceeded to XRT with either known SIC or with nondocumented removal of calcifications (NDRC) after another excision. RESULTS: Of the 78 breasts at risk with DRC via PREMAMMO, there were 7 local failures (LF) and 1 distant failure. Of the 36 breasts with NDRC via PREMAMMO, there were 7 LF and 1 regional failure. Of the 34 breasts who underwent reexcision after detection of SIC by PREMAMMO, 20 (59%) were found to have residual disease. CONCLUSIONS: Patients with DRC were found to have better local control than patients with NDRC. In addition, the presence of SIC on a PREMAMMO was associated with a high probability of detecting residual disease.  相似文献   
110.
Previous studies have shown decreased immunoreactive glial fibrillary acidic protein (GFAP) in the supraoptic nucleus (SON) when magnocellular neuroendocrine cells (MNCs) are activated by lactation or dehydration. This is thought to underlie structural plasticity of glial processes that occurs during these times. Here, we investigated how this apparent reduction in protein relates to GFAP mRNA expression in the dehydrated rat as visualized by in situ hybridization. Densitometry of silver grains in the SON revealed low levels of mRNA expression in control, 2-day dehydrated and 21-day rehydrated (R21) animals. Conversely, the SON from 7-day dehydrated (D7) subjects displayed significantly more silver grains. Thus, the pattern of GFAP mRNA expression is the inverse of what we previously observed for GFAP immunoreactivity in tissue sections of the SON. No differences in mRNA levels due to hydration state were seen in the lateral hypothalamic area, suggesting that increases in GFAP mRNA at D7 were specifically related to MNC activation. These data indicate a divergence in GFAP mRNA and protein expression in the SON.  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