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   55363篇
  免费   4577篇
  国内免费   150篇
耳鼻咽喉   511篇
儿科学   1504篇
妇产科学   1075篇
基础医学   7306篇
口腔科学   953篇
临床医学   6155篇
内科学   10541篇
皮肤病学   804篇
神经病学   4759篇
特种医学   2184篇
外科学   9311篇
综合类   773篇
一般理论   57篇
预防医学   5476篇
眼科学   1249篇
药学   4019篇
  1篇
中国医学   53篇
肿瘤学   3359篇
  2023年   291篇
  2022年   199篇
  2021年   1031篇
  2020年   654篇
  2019年   1086篇
  2018年   1305篇
  2017年   950篇
  2016年   1024篇
  2015年   1228篇
  2014年   1797篇
  2013年   2491篇
  2012年   3800篇
  2011年   3887篇
  2010年   2105篇
  2009年   1868篇
  2008年   3392篇
  2007年   3639篇
  2006年   3537篇
  2005年   3436篇
  2004年   3180篇
  2003年   3021篇
  2002年   2851篇
  2001年   873篇
  2000年   825篇
  1999年   796篇
  1998年   540篇
  1997年   454篇
  1996年   401篇
  1995年   505篇
  1994年   427篇
  1993年   394篇
  1992年   535篇
  1991年   485篇
  1990年   503篇
  1989年   465篇
  1988年   425篇
  1987年   371篇
  1986年   380篇
  1985年   426篇
  1984年   365篇
  1983年   299篇
  1982年   253篇
  1981年   230篇
  1980年   206篇
  1979年   241篇
  1978年   232篇
  1974年   210篇
  1973年   194篇
  1972年   188篇
  1968年   185篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
1.
The purpose of this study was to investigate the feasibility of two-dimensional (2D) navigated, interleaved multishot echo-planar imaging (EPI) to enhance kidney diffusion-weighted imaging (DWI) in rats at 7.0 T. Fully sampled interleaved four-shot EPI with 2D navigators was tailored for kidney DWI (Sprague–Dawley rats, n = 7) on a 7.0-T small bore preclinical scanner. The image quality of four-shot EPI was compared with T2-weighted rapid acquisition with relaxation enhancement (RARE) (reference) and single-shot EPI (ss-EPI) without and with parallel imaging (PI). The contrast-to-noise ratio (CNR) was examined to assess the image quality for the EPI approaches. The Dice similarity coefficient and the Hausdorff distance were used for evaluation of image distortion. Mean diffusivity (MD) and fractional anisotropy (FA) were calculated for renal cortex and medulla for all DWI approaches. The corticomedullary difference of MD and FA were assessed by Wilcoxon signed-rank test. Four-shot EPI showed the highest CNR among the three EPI variants and lowest geometric distortion versus T2-weighted RARE (mean Dice: 0.77 for ss-EPI without PI, 0.88 for ss-EPI with twofold undersampling, and 0.92 for four-shot EPI). The FA map derived from four-shot EPI clearly identified a highly anisotropic region corresponding to the inner stripe of the outer medulla. Four-shot EPI successfully discerned differences in both MD and FA between renal cortex and medulla. In conclusion, 2D navigated, interleaved multishot EPI facilitates high-quality rat kidney DWI with clearly depicted intralayer and interlayer structure and substantially reduced image distortion. This approach enables the anatomic integrity of DWI-MRI in small rodents and has the potential to benefit the characterization of renal microstructure in preclinical studies.  相似文献   
2.
3.
4.
Robinson  Sandra M.  Scott  Jason  Ryan  Sarah  Adams  Nicola  Hassell  Andrew  Walker  David 《Clinical rheumatology》2022,41(12):3869-3877
Clinical Rheumatology - Educating patients about methotrexate is a core role of rheumatology nurses. We have previously reported the scoring of videoed interviews of rheumatology nurses educating...  相似文献   
5.
6.
The recent death of our colleague and friend Professor Sir Michael Rutter has quite rightly been greeted by an outpouring of gratitude and respect from distinguished commentators across the globe working in diverse fields of the basic, social and clinical sciences as well as from clinicians and policy makers. These have without exception highlighted his seminal role as a pioneer, perhaps The Pioneer, of the application of the scientific method to the study of child and adolescent mental health and disorder – the father of evidence-based Child Psychiatry and the most influential voice in the new field of Developmental Psychopathology (Stevenson, 2022). In this editorial, we will attempt to build on these commentaries. We will parse Mike’s scientific contributions to our field, in order to identify the personal characteristics and intellectual modus operandi that made him such a uniquely important figure, whose influence will resonate through the many fields he influenced for decades to come. We will also attempt something of a reframing of that contribution. Our thesis being that, although he never agitated for it politically or even stated it as a goal explicitly, Mike’s work was motivated by a desire for social reform and created the scientific catalyst for such reform to occur.  相似文献   
7.
BackgroundThe American Radium Society (ARS) Appropriate Use Criteria brain malignancies panel systematically reviewed (PRISMA [Preferred Reporting Items for Systematic Reviews and Meta-Analyses]) published literature on neurocognitive outcomes after stereotactic radiosurgery (SRS) for patients with multiple brain metastases (BM) to generate consensus guidelines.MethodsThe panel developed 4 key questions (KQs) to guide systematic review. From 11 614 original articles, 12 were selected. The panel developed model cases addressing KQs and potentially controversial scenarios not addressed in the systematic review (which might inform future ARS projects). Based upon quality of evidence, the panel confidentially voted on treatment options using a 9-point scale of appropriateness.ResultsThe panel agreed that SRS alone is usually appropriate for those with good performance status and 2–10 asymptomatic BM, and usually not appropriate for >20 BM. For 11–15 and 16–20 BM there was (between 2 case variants) agreement that SRS alone may be appropriate or disagreement on the appropriateness of SRS alone. There was no scenario (among 6 case variants) in which conventional whole-brain radiotherapy (WBRT) was considered usually appropriate by most panelists. There were several areas of disagreement, including: hippocampal sparing WBRT for 2–4 asymptomatic BM; WBRT for resected BM amenable to SRS; fractionated versus single-fraction SRS for resected BM, larger targets, and/or brainstem metastases; optimal treatment (WBRT, hippocampal sparing WBRT, SRS alone to all or select lesions) for patients with progressive extracranial disease, poor performance status, and no systemic options.ConclusionsFor patients with 2–10 BM, SRS alone is an appropriate treatment option for well-selected patients with good performance status. Future study is needed for those scenarios in which there was disagreement among panelists.  相似文献   
8.
9.
Lung and female breast cancers are highly prevalent worldwide. Although the association between exposure to ambient fine particulate matter (PM2.5) and lung cancer has been recognized, there is less evidence for associations with other common air pollutants such as nitrogen dioxide (NO2) and ozone (O3). Even less is known about potential associations between these pollutants and breast cancer. We conducted a population-based cohort study to investigate the associations of chronic exposure to PM2.5, NO2, O3 and redox-weighted average of NO2 and O3 (Ox) with incident lung and breast cancer, using the Ontario Population Health and Environment Cohort (ONPHEC), which includes all long-term residents aged 35–85 years who lived in Ontario, Canada, 2001–2015. Incident lung and breast cancers were ascertained using the Ontario Cancer Registry. Annual estimates of exposures were assigned to the residential postal codes of subjects for each year during follow-up. We used Cox proportional-hazards models adjusting for personal- and neighborhood-level covariates. Our cohorts for lung and breast cancer analyses included ~4.9 million individuals and ~2.5 million women, respectively. During follow-up, 100,146 incident cases of lung cancer and 91,146 incident cases of breast cancer were diagnosed. The fully adjusted analyses showed positive associations of lung cancer incidence with PM2.5 (hazard ratio [HR] = 1.02 [95% CI: 1.01–1.05] per 5.3 μg/m3) and NO2 (HR = 1.05 [95% CI: 1.03–1.07] per 14 ppb). No associations with lung cancer were observed for O3 or Ox. Relationships between PM2.5 and NO2 with lung cancer exhibited a sublinear shape. We did not find compelling evidence linking air pollution to breast cancer.  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