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   2432728篇
  免费   185227篇
  国内免费   3736篇
耳鼻咽喉   33981篇
儿科学   79365篇
妇产科学   68480篇
基础医学   345660篇
口腔科学   71554篇
临床医学   215840篇
内科学   467589篇
皮肤病学   53256篇
神经病学   192409篇
特种医学   97457篇
外国民族医学   665篇
外科学   370429篇
综合类   56635篇
现状与发展   4篇
一般理论   772篇
预防医学   182262篇
眼科学   56180篇
药学   188080篇
  9篇
中国医学   5175篇
肿瘤学   135889篇
  2018年   23524篇
  2016年   20791篇
  2015年   23713篇
  2014年   32603篇
  2013年   49003篇
  2012年   66527篇
  2011年   70234篇
  2010年   41525篇
  2009年   39403篇
  2008年   66696篇
  2007年   70503篇
  2006年   71844篇
  2005年   69208篇
  2004年   67634篇
  2003年   64774篇
  2002年   63150篇
  2001年   119730篇
  2000年   123523篇
  1999年   104064篇
  1998年   27608篇
  1997年   24703篇
  1996年   24593篇
  1995年   23706篇
  1994年   21995篇
  1993年   20773篇
  1992年   83172篇
  1991年   80502篇
  1990年   79045篇
  1989年   76403篇
  1988年   70398篇
  1987年   69180篇
  1986年   65648篇
  1985年   62944篇
  1984年   46481篇
  1983年   39846篇
  1982年   22870篇
  1981年   20229篇
  1980年   19058篇
  1979年   43557篇
  1978年   29938篇
  1977年   25796篇
  1976年   23630篇
  1975年   25590篇
  1974年   30785篇
  1973年   29676篇
  1972年   27697篇
  1971年   26095篇
  1970年   23937篇
  1969年   22710篇
  1968年   20608篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
Evidence continues to grow on potential environmental health hazards associated with engineered nanomaterials (ENMs). While the geno- and cytotoxic effects of ENMs have been investigated, their potential to target the epigenome remains largely unknown. The aim of this study is two-fold: 1) determining whether or not industry relevant ENMs can affect the epigenome in vivo and 2) validating a recently developed in vitro epigenetic screening platform for inhaled ENMs. Laser printer-emitted engineered nanoparticles (PEPs) released from nano-enabled toners during consumer use and copper oxide (CuO) were chosen since these particles induced significant epigenetic changes in a recent in vitro companion study. In this study, the epigenetic alterations in lung tissue, alveolar macrophages and peripheral blood from intratracheally instilled mice were evaluated. The methylation of global DNA and transposable elements (TEs), the expression of the DNA methylation machinery and TEs, in addition to general toxicological effects in the lung were assessed. CuO exhibited higher cell-damaging potential to the lung, while PEPs showed a greater ability to target the epigenome. Alterations in the methylation status of global DNA and TEs, and expression of TEs and DNA machinery in mouse lung were observed after exposure to CuO and PEPs. Additionally, epigenetic changes were detected in the peripheral blood after PEPs exposure. Altogether, CuO and PEPs can induce epigenetic alterations in a mouse experimental model, which in turn confirms that the recently developed in vitro epigenetic platform using macrophage and epithelial cell lines can be successfully utilized in the epigenetic screening of ENMs.  相似文献   
103.
104.
105.
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   
106.
107.
108.
109.
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   
110.
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