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   3189篇
  免费   226篇
  国内免费   31篇
耳鼻咽喉   37篇
儿科学   114篇
妇产科学   36篇
基础医学   599篇
口腔科学   95篇
临床医学   362篇
内科学   840篇
皮肤病学   130篇
神经病学   86篇
特种医学   299篇
外科学   325篇
综合类   56篇
预防医学   137篇
眼科学   43篇
药学   193篇
中国医学   2篇
肿瘤学   92篇
  2021年   36篇
  2019年   30篇
  2018年   41篇
  2017年   39篇
  2016年   55篇
  2015年   57篇
  2014年   60篇
  2013年   126篇
  2012年   88篇
  2011年   85篇
  2010年   90篇
  2009年   63篇
  2008年   65篇
  2007年   81篇
  2006年   89篇
  2005年   64篇
  2004年   75篇
  2003年   82篇
  2002年   64篇
  2001年   60篇
  2000年   58篇
  1999年   70篇
  1998年   102篇
  1997年   108篇
  1996年   114篇
  1995年   82篇
  1994年   84篇
  1993年   81篇
  1992年   51篇
  1991年   48篇
  1990年   51篇
  1989年   82篇
  1988年   69篇
  1987年   60篇
  1986年   63篇
  1985年   48篇
  1984年   64篇
  1983年   35篇
  1982年   34篇
  1981年   39篇
  1980年   49篇
  1977年   36篇
  1976年   38篇
  1975年   37篇
  1965年   50篇
  1964年   51篇
  1963年   48篇
  1962年   41篇
  1961年   40篇
  1960年   66篇
排序方式: 共有3446条查询结果,搜索用时 15 毫秒
81.
82.
We have developed a non-invasive method utilizing feces, containing sloughed colonocytes, as a sensitive technique for detecting diagnostic colonic biomarkers. In this study, we used the rat colon carcinogenesis model to determine if changes in fecal protein kinase C (PKC) expression have predictive value in monitoring the neoplastic process. Weanling rats were injected with saline or azoxymethane (AOM) and 36 weeks later fecal samples and mucosa were collected, poly A+ RNA isolated, and quantitative RT-PCR performed using primers to PKC betaII and zeta. Fecal PKC betaII and zeta mRNA levels were altered by the presence of a tumor, with tumor-bearing animals having a 3-fold higher (P < 0.05) PKC betaII expression as compared with animals without tumors. In addition, AOM-injection increased mucosal PKC betaII mRNA expression compared with saline controls. No effect of tumor incidence on mucosal PKC betaII expression was observed. In contrast, fecal PKC zeta expression was 2.5-fold lower (P < 0.05) in animals injected with azoxymethane versus saline. Since tumor incidence exerts a reciprocal effect on fecal PKC betaII and zeta mRNA expression, data were also expressed as the ratio between PKC betaII and zeta. The isozyme ratio was strongly related to tumor incidence, i.e. ratio for animals with tumors was 2.18 +/- 1.25, animals without tumors was 0.50 +/- 0.16, P = 0.025. We demonstrate that the expression of fecal PKC betaII and zeta may serve as a noninvasive marker for development of colon tumors. A sensitive technique for the detection of colon cancer is of importance since early diagnosis can substantially reduce mortality.   相似文献   
83.
Epilepsy surgery has emerged as an important option in the treatment of children with epilepsy that is refractory to antiepileptic drug management. The cornerstone of successful surgery is accurate localization of the brain region of seizure onset. Traditional techniques of seizure onset localization, e.g. surface electroencephalography (EEG) recording and magnetic resonance imaging (MRI), allow accurate localization in a significant number of patients. When the focus of seizure onset is not apparent from these non-invasive techniques, other methods of localization, e.g. intracranial EEG recording, may be needed before resection of the focus. Single-photon emission computed tomography (SPECT) is a nuclear medicine blood-flow technique that has been used to identify a region of epileptogenic brain associated with low blood flow in the resting state (interictal SPECT) or increased blood flow at the time of seizure activity (ictal SPECT). This report describes the validation and utility of a computer-assisted method of subtracting the interictal from the ictal SPECT scans and co-registering the difference image on the MRI. This method, called subtraction ictal SPECT co-registered on MRI (SISCOM), is used in guiding the location and the extent of intracranial electrode implantation, or in obviating the need for the implantation in some cases.  相似文献   
84.
We aim to study the SCN5A gene in a cohort of Brugada syndrome (BS) patients and evaluate the genotype–phenotype correlation. BS is caused by mutations in up to 10 different genes, SCN5A being the most frequently involved. Large genomic rearrangements in SCN5A have been associated with conduction disease, but its prevalence in BS is unknown. Seventy‐six non‐related patients with BS were studied. Clinical characteristics and family risk profile were recorded. Direct sequencing and multiplex ligation‐dependent probe amplification (MLPA) of the SCN5A gene for identification of mutations and larger rearrangements were performed, respectively. Eight patients (10.5%) had point mutations (R27H, E901K, G1743R (detected in three families), V728I, N1443S and E1152X). Patients with mutations had a trend toward a higher proportion of spontaneous type I Brugada electrocardiogram (ECG) (87.5% vs 52.9%, p = 0.06) and had evidence of familial disease (62.5%, vs 23.5%, p = 0.03). The symptoms and risk profile of the carriers were not different from wild‐type probands. There were non‐significant differences in the prevalence of type I ECG, syncope and history of arrhythmia in carriers of selected polymorphisms. None of the patients had any deletion/duplication in the SCN5A gene. In conclusion, 10.5% of our patients had mutations in the SCN5A gene. Patients with mutations seemed to have more spontaneous type I ECG, but no differences in syncope or arrhythmic events compared with patients without mutations. Larger studies are needed to evaluate the role of polymorphisms in the SCN5A in the expression of the phenotype and prognosis. Large rearrangements were not identified in the SCN5A gene using the MLPA technique.  相似文献   
85.
86.
87.
88.
89.
90.
One of the most common craniofacial malformations observed in newborn babies is cleft lip and palate (CLP). This syndrome presents with some anatomic variations. The aim of this study was to understand an anatomic variation of the crista galli that had not been reported previously in patients with CLP. A 17-year-old boy with CLP was referred to an orthodontic clinic for cone-beam computed tomography (CBCT) imaging before treatment. Axial and coronal sections and three-dimensional images showed that the crista galli had bifid heads that were attached to each other. Incomplete ossification had resulted in a bifid crista galli and the appearance of a suture in the anterior coronal section of the CBCT images. This anatomic variation could allow penetration of the anterior fossa during endoscopic surgery, which could be dangerous for the patient.  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