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   2229537篇
  免费   182918篇
  国内免费   4127篇
耳鼻咽喉   31687篇
儿科学   71016篇
妇产科学   64528篇
基础医学   318838篇
口腔科学   66314篇
临床医学   197018篇
内科学   430831篇
皮肤病学   47060篇
神经病学   181483篇
特种医学   89618篇
外国民族医学   632篇
外科学   341555篇
综合类   58596篇
现状与发展   5篇
一般理论   765篇
预防医学   174202篇
眼科学   52297篇
药学   168186篇
  3篇
中国医学   4257篇
肿瘤学   117691篇
  2018年   20486篇
  2015年   20978篇
  2014年   29254篇
  2013年   44678篇
  2012年   60297篇
  2011年   63516篇
  2010年   37407篇
  2009年   35545篇
  2008年   60527篇
  2007年   64639篇
  2006年   65090篇
  2005年   63546篇
  2004年   62538篇
  2003年   59941篇
  2002年   58396篇
  2001年   99563篇
  2000年   102573篇
  1999年   87127篇
  1998年   24696篇
  1997年   22590篇
  1996年   22456篇
  1995年   21679篇
  1994年   20482篇
  1993年   19264篇
  1992年   72661篇
  1991年   70583篇
  1990年   69100篇
  1989年   66757篇
  1988年   62453篇
  1987年   61461篇
  1986年   58464篇
  1985年   56578篇
  1984年   42908篇
  1983年   36901篇
  1982年   22502篇
  1981年   20312篇
  1980年   18976篇
  1979年   41984篇
  1978年   29633篇
  1977年   24958篇
  1976年   23290篇
  1975年   24849篇
  1974年   30638篇
  1973年   29383篇
  1972年   27282篇
  1971年   25709篇
  1970年   23874篇
  1969年   22735篇
  1968年   20643篇
  1967年   18846篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.  相似文献   
92.
We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.  相似文献   
93.
Background A high Mandard score implies a non-response to chemotherapy in oesophageal adenocarcinoma. However, some patients exhibit tumour volume reduction and a nodal response despite a high score. This study examines survival and recurrence patterns in these patients.Methods Clinicopathological factors were analysed using multivariable Cox regression assessing time to death and recurrence. Computed tomography-estimated tumour volume change was examined in a subgroup of consecutive patients.Results Five hundred and fifty-five patients were included. Median survival was 55 months (Mandard 1–3) and 21 months (Mandard 4 and 5). In the Mandard 4 and 5 group (332 patients), comparison between complete nodal responders and persistent nodal disease showed improved survival (90 vs 18 months), recurrence rates (locoregional 14.75 vs 28.74%, systemic 24.59 vs 48.42%) and circumferential resection margin positivity (22.95 vs 68.11%). Complete nodal response independently predicted improved survival (hazard ratio 0.34 (0.16–0.74). Post-chemotherapy tumour volume reduction was greater in patients with a complete nodal response (−16.3 vs −7.7 cm3, p = 0.033) with no significant difference between Mandard groups.Conclusion Patients with a complete nodal response to chemotherapy have significantly improved outcomes despite a poor Mandard score. High Mandard score does not correspond with a non-response to chemotherapy in all cases and patients with nodal downstaging may still benefit from adjuvant chemotherapy.Subject terms: Oesophageal cancer, Surgical oncology  相似文献   
94.
95.
96.
Abstract

Objective: To understand the origin of extremely high gonadotropin levels in a perimenopausal woman.

Methods: A 52-year-old woman with a 2?months of amenorrhea followed spontaneous menstrual cycles recovery was referred to our outpatient clinic with elevated follicle-stimulating hormone (FSH, 483 mUI/ml), luteinizing hormone (LH, 475 mUI/ml) and prolactin (PRL, 173?ng/ml). She was known to take levosulpiride. The gonadotropin levels did not fit with the clinical features.

Results: A gonadotroph tumor was ruled out. Further analysis confirmed constantly high FSH, LH and PRL levels. The measurements were repeated using different analytical platforms with different results. After serial dilutions, nonlinearity was present suggesting an immunoassay interference. After post-polyethylene glycol recovery, hormone levels appeared in the normal range. Anti-goat antibodies were recognized in the serum of the patient.

Conclusions: This case report shows a case of falsely abnormal high gonadotropin and PRL levels in a woman during menopause transition. In the clinical practice the evaluation of gonadotropin profile is not recommended at this age, but the abnormal levels stimulated further evaluation. An interference in the assay due to anti-goat antibodies resulted in abnormally high level of FSH and LH. A strict collaboration between clinicians and the laboratory is needed, when laboratory findings do not correspond to clinical findings.  相似文献   
97.
98.
99.
100.
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