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   22586篇
  免费   1434篇
  国内免费   103篇
耳鼻咽喉   224篇
儿科学   596篇
妇产科学   494篇
基础医学   3454篇
口腔科学   598篇
临床医学   2188篇
内科学   5023篇
皮肤病学   557篇
神经病学   2655篇
特种医学   662篇
外科学   2015篇
综合类   111篇
一般理论   13篇
预防医学   1876篇
眼科学   430篇
药学   1384篇
  1篇
中国医学   84篇
肿瘤学   1758篇
  2024年   89篇
  2023年   238篇
  2022年   421篇
  2021年   744篇
  2020年   519篇
  2019年   707篇
  2018年   735篇
  2017年   553篇
  2016年   671篇
  2015年   765篇
  2014年   922篇
  2013年   1150篇
  2012年   1846篇
  2011年   1954篇
  2010年   1039篇
  2009年   935篇
  2008年   1546篇
  2007年   1532篇
  2006年   1452篇
  2005年   1352篇
  2004年   1277篇
  2003年   1140篇
  2002年   966篇
  2001年   152篇
  2000年   104篇
  1999年   155篇
  1998年   190篇
  1997年   164篇
  1996年   124篇
  1995年   95篇
  1994年   75篇
  1993年   51篇
  1992年   57篇
  1991年   42篇
  1990年   53篇
  1989年   36篇
  1988年   27篇
  1987年   29篇
  1986年   18篇
  1985年   20篇
  1984年   20篇
  1983年   16篇
  1982年   15篇
  1981年   13篇
  1980年   15篇
  1979年   13篇
  1978年   10篇
  1975年   9篇
  1974年   10篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Since the mechanisms by which specific immunity destroys Her-2/neu carcinoma cells are highly undetermined, these were assessed in BALB/c mice vaccinated with plasmids encoding extracellular and transmembrane domains of the protein product (p185(neu)) of the rat Her-2/neu oncogene shot into the skin by gene gun. Vaccinated mice rejected a lethal challenge of TUBO carcinoma cells expressing p185(neu). Depletion of CD4 T cells during immunization abolished the protection, while depletion of CD8 cells during the effector phase halved it, and depletion of polymorphonuclear granulocytes abolished all protection. By contrast, Ig mu-chain gene KO mice, as well as Fcgamma receptor I/III, beta-2 microglobulin, CD1, monocyte chemoattractant protein 1 (MCP1), IFN-gamma, and perforin gene KO mice were protected. Only mice with both IFN-gamma and perforin gene KOs were not protected. Although immunization also cured all BALB/c mice bearing established TUBO carcinomas, it did not cure any of the perforin KO or perforin and IFN-gamma KO mice. Few mice were cured that had knockouts of the gene for Ig mu-chain, Fcgamma receptor I/III, IFN-gamma, or beta-2 microglobulin. Moreover, vaccination cured half of the CD1 and the majority of the MCP1 KO mice. The eradication of established p185(neu) carcinomas involves distinct mechanisms, each endowed with a different curative potential.  相似文献   
42.

Introduction and hypothesis

Ongoing debate exists about whether the rectovaginal septum (Denonvilliers’ fascia) is myth or reality. This study evaluates magnetic resonance images (MRI) of women with Müllerian agenesis for the presence of fascial layers between the rectum and the bladder to test the hypothesis that this layer exists in the absence of the vagina.

Methods

This is a secondary analysis of a study describing MRI aspects in women with vaginal agenesis before and after laparoscopic Vecchietti procedure. Study participants (n?=?16) had a multiplanar pelvic MR scan. Images were evaluated independently by two investigators (MH, JOLD) for the appearance of layers separate from the bladder and rectum in the area of interest, with characteristic anatomical features of the septum.

Results

Participants’ mean age was 19.4?±?2.6 years ± standard deviation (SD). In 12 of 16 patients (75 %) a distinct layer between rectum and bladder was identified in either the axial (4/16; 25 %) or sagittal (12/16; 75 %) scan or both. Characteristic anatomical features included lateral attachment to the levator ani muscle, cranial fusion to the cul-de-sac peritoneum, and caudal insertion into the perineal body.

Conclusions

Three quarters of women with Müllerian agenesis have a visible layer between bladder and rectum. As none of the participants had a vagina, these results support the existence of a rectovaginal septum, separate from a vaginal adventitia.  相似文献   
43.

Background  

The aim of this study, conducted in 2006, was to find out whether changes in sedation management in German intensive care units took place in comparison with our survey from 2002.  相似文献   
44.
45.
Cortical superficial siderosis (cSS) is a magnetic resonance imaging marker of cerebral amyloid angiopathy (CAA) and can be its sole imaging sign. cSS has further been identified as a risk marker for future intracranial hemorrhage. Although uncommon in the general population, cSS may be much more prevalent in high risk populations for amyloid pathology. We aimed to determine the frequency of cSS in patients with cognitive impairment presenting to a memory clinic. We prospectively evaluated consecutive patients presenting to our memory clinic between April 2011 and April 2013. Subjects received neuropsychological testing using the Consortium to Establish a Registry for Alzheimer’s Disease battery (CERAD-NP). Two hundred and twelve patients with documented cognitive impairment further underwent a standardized 3T-MR-imaging protocol with T2*-weighted gradient-echo sequences for detection of cSS. Thirteen of 212 patients (6.1 %) displayed cSS. In seven of them (54 %) cSS was the only imaging sign of CAA. Patients with cSS did not differ from patients without cSS with regard to medical history, age or cardiovascular risk profile. Subjects with cSS performed worse in the mini-mental state examination (p = 0.001), showed more white matter hyperintensities (p = 0.005) and more often had microbleeds (p = 0.001) compared to those without cSS. cSS is common in patients with cognitive impairment. It is associated with lower cognitive scores, white matter hyperintensities and microbleeds and can be the only imaging sign for CAA in this patient group.  相似文献   
46.
Cognitive impairments are central to schizophrenia, but their clinical utility for tagging heterogeneity in lifetime outcome and response to treatment is not conclusive. By exploiting four cognitive domains consistently showing large deficits in studies, we tested whether cluster analysis would define separate subsets of patients and then whether the disease heterogeneity marked by these clusters would be related to lifetime outcome and response to treatment. A total of 112 schizophrenia patients completed a neuropsychological evaluation. The PANSS, GAF-S and GAF-F were rated at the onset and endpoint of the illness trajectory. A blind judgment of the lifetime response to treatment was made. The first cluster presented near-normal cognitive performance. Two other clusters of severely impaired patients were identified: one generally impaired in the four cognitive domains and another selectively impaired in visual episodic memory and processing speed, each relating to a different lifetime evolution of disease and treatment response. Although the two impaired clusters were clinically indistinguishable in symptom severity and functioning at disease onset, patients with selective cognitive impairments demonstrated better improvement at outcome, whereas the generally impaired patients were more likely to be treatment refractory. The findings have implications for the management of patients and for clinical trials since particular combinations of cognitive deficits in patients would influence their treatment response.  相似文献   
47.
Selective attention mechanisms allow us to focus on information that is relevant to the current behavior and, equally important, ignore irrelevant information. An influential model proposes that oscillatory neural activity in the alpha band serves as an active functional inhibitory mechanism. Recent studies have shown that, in the same way that attention can be selectively oriented to bias sensory processing in favor of relevant stimuli in perceptual tasks, it is also possible to retrospectively orient attention to internal representations held in working memory. However, these studies have not explored the associated oscillatory phenomena. In the current study, we analysed the patterns of neural oscillatory activity recorded with magnetoencephalography while participants performed a change detection task, in which a spatial retro‐cue was presented during the maintenance period, indicating which item or items were relevant for subsequent retrieval. Participants benefited from retro‐cues in terms of accuracy and reaction time. Retro‐cues also modulated oscillatory activity in the alpha and gamma frequency bands. We observed greater alpha activity in a ventral visual region ipsilateral to the attended hemifield, thus supporting its suppressive role, i.e. a functional disengagement of task‐irrelevant regions. Accompanying this modulation, we found an increase in gamma activity contralateral to the attended hemifield, which could reflect attentional orienting and selective processing. These findings suggest that the oscillatory mechanisms underlying attentional orienting to representations held in working memory are similar to those engaged when attention is oriented in the perceptual space.  相似文献   
48.
There has been much fanfare, and rightly so, heralding a revolution in the treatment of autoimmune disease using biologic agents-antibodies or other molecules that specifically target known mediators of disease. But not all patients respond to even the most successful biologic agent, which may provide clues about alternate disease mechanisms. Studies aimed at understanding the mechanism of action of biologic agents will yield significant benefits for experimental medicine.  相似文献   
49.
50.
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