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   64649篇
  免费   4971篇
  国内免费   157篇
耳鼻咽喉   831篇
儿科学   1704篇
妇产科学   1205篇
基础医学   8295篇
口腔科学   1479篇
临床医学   6733篇
内科学   12745篇
皮肤病学   695篇
神经病学   6229篇
特种医学   2484篇
外国民族医学   3篇
外科学   9648篇
综合类   1273篇
现状与发展   1篇
一般理论   84篇
预防医学   6397篇
眼科学   1237篇
药学   4214篇
中国医学   75篇
肿瘤学   4445篇
  2022年   354篇
  2021年   924篇
  2020年   548篇
  2019年   946篇
  2018年   1134篇
  2017年   810篇
  2016年   876篇
  2015年   1035篇
  2014年   1534篇
  2013年   2446篇
  2012年   3668篇
  2011年   3792篇
  2010年   2066篇
  2009年   1940篇
  2008年   3618篇
  2007年   3856篇
  2006年   3674篇
  2005年   3847篇
  2004年   3588篇
  2003年   3327篇
  2002年   3270篇
  2001年   1289篇
  2000年   1202篇
  1999年   1148篇
  1998年   879篇
  1997年   823篇
  1996年   773篇
  1995年   741篇
  1994年   569篇
  1993年   523篇
  1992年   908篇
  1991年   821篇
  1990年   817篇
  1989年   763篇
  1988年   714篇
  1987年   692篇
  1986年   694篇
  1985年   685篇
  1984年   659篇
  1983年   582篇
  1982年   557篇
  1981年   556篇
  1980年   508篇
  1979年   537篇
  1978年   427篇
  1977年   376篇
  1976年   330篇
  1975年   308篇
  1974年   363篇
  1973年   306篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Individuals with sudden unilateral deafness offer a unique opportunity to study plasticity of the binaural auditory system in adult humans. Stimulation of the intact ear results in increased activity in the auditory cortex. However, there are no reports of changes at sub-cortical levels in humans. Therefore, the aim of the present study was to investigate changes in sub-cortical activity immediately before and after the onset of surgically induced unilateral deafness in adult humans. Click-evoked auditory brainstem responses (ABRs) to stimulation of the healthy ear were recorded from ten adults during the course of translabyrinthine surgery for the removal of a unilateral acoustic neuroma. This surgical technique always results in abrupt deafferentation of the affected ear. The results revealed a rapid (within minutes) reduction in latency of wave V (mean pre = 6.55 ms; mean post = 6.15 ms; p < 0.001). A latency reduction was also observed for wave III (mean pre = 4.40 ms; mean post = 4.13 ms; p < 0.001). These reductions in response latency are consistent with functional changes including disinhibition or/and more rapid intra-cellular signalling affecting binaurally sensitive neurons in the central auditory system. The results are highly relevant for improved understanding of putative physiological mechanisms underlying perceptual disorders such as tinnitus and hyperacusis.  相似文献   
3.
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   
4.
5.
6.
7.
8.

Background

Etomidate is frequently selected over propofol for induction of anaesthesia because of a putatively favourable haemodynamic profile, but data confirming this perception are limited.

Methods

Patients undergoing cardiac surgery were randomised to induction of anaesthesia with propofol or etomidate. Phase I (n=75) was conducted as open-label, whereas Phase II (n=75) was double blind. Mean arterial blood pressure (MAP) and boluses of vasopressor administered after induction were recorded. The primary endpoint was the area under the curve below baseline MAP (MAP-time integral) during the 10 min after induction. Secondary endpoints were the use of vasopressors over the same period, and the effect of blinding on the aforementioned endpoints. Groups were compared using regression models with phase and anaesthetist as factors.

Results

The mean difference between etomidate and propofol in the MAP-time integral below baseline was 2244 mm Hg s (95% confidence interval, 581–3906; P=0.009), representing a 34% greater reduction with propofol. Overall, vasopressors were used in 10/75 patients in the etomidate group vs 21/75 in the propofol group (P=0.38), and in 20/74 patients during the blinded phase vs 11/76 during the open-label phase (P=0.31). The interaction between randomisation and phase (open-labelled or blinded) was not significant for either primary (P=0.73) or secondary endpoints (P=0.90).

Conclusions

Propofol caused a 34% greater reduction in MAP-time integral from baseline after induction of anaesthesia than etomidate, despite more frequent use of vasopressors with propofol, confirming the superior haemodynamic profile of etomidate in this context. The proportion of patients receiving vasopressors increased slightly, albeit not significantly, in both groups in the blinded phase.

Clinical trial registration

Australian and New Zealand Clinical Trials Registry, ACTRN12614000717651.  相似文献   
9.
This paper reviews the published literature on a group of developmental disorders of the retina and retinal pigment epithelium which result in focal abnormalities in one or both eyes. They are often asymptomatic, found on routine examination and are generally non-progressive. Some are associated with other systemic abnormalities.Subject terms: Retinal diseases, Eye abnormalities  相似文献   
10.
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