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   1805篇
  免费   124篇
  国内免费   13篇
耳鼻咽喉   7篇
儿科学   39篇
妇产科学   40篇
基础医学   313篇
口腔科学   63篇
临床医学   217篇
内科学   318篇
皮肤病学   25篇
神经病学   176篇
特种医学   113篇
外科学   137篇
综合类   13篇
预防医学   180篇
眼科学   20篇
药学   179篇
中国医学   9篇
肿瘤学   93篇
  2024年   1篇
  2023年   24篇
  2022年   45篇
  2021年   96篇
  2020年   61篇
  2019年   75篇
  2018年   97篇
  2017年   55篇
  2016年   71篇
  2015年   78篇
  2014年   107篇
  2013年   149篇
  2012年   174篇
  2011年   187篇
  2010年   97篇
  2009年   68篇
  2008年   99篇
  2007年   99篇
  2006年   101篇
  2005年   76篇
  2004年   55篇
  2003年   41篇
  2002年   34篇
  2001年   4篇
  2000年   3篇
  1999年   4篇
  1998年   7篇
  1997年   5篇
  1996年   6篇
  1995年   3篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1988年   1篇
  1986年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1978年   2篇
  1973年   1篇
  1956年   2篇
  1954年   2篇
排序方式: 共有1942条查询结果,搜索用时 375 毫秒
21.
22.
23.
24.
The actual nature of spindle cell carcinoma has been debated extensively because of its rarity. It carries a poor prognosis, even when early-stage disease is diagnosed and resected. In view of the rarity and the significance of the histological diagnosis, we report a patient with rapidly progressing spindle cell lung carcinoma with soft tissue metastasis. Diagnosis was confirmed by immunohistochemistry finding. Analysis of the TP53 gene mutations by polymerase chain reaction and DNA sequencing revealed insertion of single thymine resulting in frameshift mutation in the exon 8. Prognosis of spindle cell lung carcinoma might be determined by the sarcoma component of the tumor and, based on that, we wonder if this type of lung carcinoma could be followed-up and treated by strategies for soft tissue sarcomas, because of its rapid, sarcomatous type of growth, beside the properly lung carcinoma oncological treatment.  相似文献   
25.
26.

Aims/hypothesis

The self-administered Michigan Neuropathy Screening Instrument (MNSI) is used to diagnose diabetic peripheral neuropathy. We examined whether the MNSI might also provide information on risk of death and cardiovascular outcomes.

Methods

In this post hoc analysis of the Aliskiren Trial in Type 2 Diabetes Using Cardio-Renal Endpoints (ALTITUDE) trial, we divided 8463 participants with type 2 diabetes and chronic kidney disease (CKD) and/or cardiovascular disease (CVD) into independent training (n = 3252) and validation (n = 5211) sets. In the training set, we identified specific questions that were independently associated with a cardiovascular composite outcome (cardiovascular death, resuscitated cardiac arrest, non-fatal myocardial infarction/stroke, heart failure hospitalisation). We then evaluated the performance of these questions in the validation set.

Results

In the training set, three questions (‘Are your legs numb?’, ‘Have you ever had an open sore on your foot?’ and ‘Do your legs hurt when you walk?’) were significantly associated with the cardiovascular composite outcome. In the validation set, after multivariable adjustment for key covariates, one or more positive responses (n = 3079, 59.1%) was associated with a higher risk of the cardiovascular composite outcome (HR 1.54 [95% CI 1.28, 1.85], p < 0.001), heart failure hospitalisation (HR 1.74 [95% CI 1.29, 2.35], p < 0.001), myocardial infarction (HR 1.81 [95% CI 1.23, 2.69], p = 0.003), stroke (HR 1.75 [95% CI 1.20, 2.56], p = 0.003) and three-point major adverse cardiovascular events (MACE) (cardiovascular death, non-fatal myocardial infarction, non-fatal stroke) (HR 1.49 [95% CI 1.20, 1.85], p < 0.001) relative to no positive responses to all questions. Associations were stronger if participants answered positively to all three questions (n = 552, 11%). The addition of the total number of affirmative responses to existing models significantly improved Harrell’s C statistic for the cardiovascular composite outcome (0.70 vs 0.71, p = 0.010), continuous net reclassification improvement (+22% [+10%, +31%], p = 0.027) and integrated discrimination improvement (+0.9% [+0.4%, +2.1%], p = 0.007).

Conclusions/interpretation

We identified three questions from the MNSI that provide additional prognostic information for individuals with type 2 diabetes and CKD and/or CVD. If externally validated, these questions may be integrated into the clinical history to augment prediction of CV events in high-risk individuals with type 2 diabetes.
  相似文献   
27.
Purpose: The purpose of this study was to investigate in vivo antitumor activity of newly synthesized N-sulfonylpyrimidine derivatives 1-(p-toluenesulfonyl)cytosine (4H), 1-(p-toluenesulfonyl)cytosine hydrochloride (4H×HCl) and zinc(II) complex of 1-(p-toluenesulfonyl)cytosine (4K). Materials and methods: In order to do that we have used mouse anaplastic mammary carcinoma (AMCa). Tumor cells (106) in a volume of 0.02 ml were transplanted into the thigh of the right hind leg of CBA mice. All compounds were dissolved in distilled water immediately before injecting to animals. Results: Antitumor effect of these compounds depends on drug doses and time interval between tumor transplantation and drug application. Further the efficacy of these compounds depends on number of drug injections, i. e. whether drug was given in single or in multiple doses. Multiple doses of 400 mg/kg of 1-(p-toluenesulfonyl)cytosine (4H) showed good antitumor effect when applied on day 1, 3, 5, 7 and 9 after tumor transplantation. Still good but slightly lower antitumor effect was also achieved when that compound was given in a single dose (1,200 mg/kg) on day 1 after tumor transplantation. The longest period of tumor growth time was obtained after application of 1-(p-toluenesulfonyl)cytosine hydrochloride (4H×HCl) given as a single dose (300 mg/kg) on day 1 or on day 6 after tumor implantation. However, antitumor effect of zinc(II) complex of 1-(p-toluenesulfonyl)cytosine (4K) was very strong when 300 mg/kg was given on day 1 or day 6, while this effect was slightly lower when drug (200 mg/kg/inj) was given on day 1, 3, 5, 7 and 9 or on day 6, 8, 10, 12 and 14. Conclusion: In this work it has been found that N-1-sulfonylcytosine derivatives have strong antitumor activity against mouse mammary carcinoma which is a good reason for further research of these compounds both in experimental and preclinical studies.  相似文献   
28.
29.
Migraine shares a complex and poorly understood relationship with sleep. Patients consistently report poor sleep prior to migraine attacks and during them, identifying poor sleep as a migraine trigger. However, anecdotally, sleep is reported to serve a therapeutic role in terminating headache. Are the associations between migraine and sleep simply the result of various bidirectional relationships? A growing body of evidence suggests there may be a common underlying etiology as well. Our objective was to review studies of sleep and migraine from the last 2 decades utilizing validated subjective and objective measures of sleep and to explore potential mechanisms underlying this complex relationship by incorporating recent advances in neuroscience. We specifically focus on insomnia, obstructive sleep apnea, parasomnias, sleep related movement disorders, and REM sleep related disorders and their relationship to migraine. Parts of brainstem‐cortical networks involved in sleep physiology are unintentionally being identified as important factors in the common migraine pathway. Recent discoveries on anatomic localization (the hypothalamus as a key and early mediator in the pathophysiology of migraine), common mediating signaling molecules (such as serotonin and dopamine), and the discovery of a new CNS waste removal system, the glymphatic system, all point to a common pathophysiology manifesting in migraine and sleep problems.  相似文献   
30.
MgTiO3 nanoparticles doped with Mn4+, with homogeneous size ranging about 63.1 ± 9.8 nm, were synthesized by a molten salt assisted sol gel method. These nanoparticles have been investigated as optical thermal sensors. The luminescence of tetravalent manganese ion in octahedral environment within the perovskite host presents drastic variations with temperature. Three different thermometry approaches have been proposed and characterized. Two luminescence intensity ratios are studied. Firstly between the two R-lines of Mn4+ emission at low temperature (−250 °C and −90 °C) with a maximal sensitivity of 0.9% °C−1, but also secondly between 2E → 4A2 (R-line) and the 4T24A2 transitions. This allows studying the temperature variation within a larger temperature range (−200 °C to 50 °C) with a sensitivity between 0.6% °C−1 and 1.2% °C−1 over this range. The last proposed method is the study of the lifetime variation versus temperature. The effective lifetime value corresponds to a combination of transitions from two excited energy levels of the tetravalent manganese (2E and 4T2) in thermal equilibrium toward the fundamental 4A2 state. Since the more energetic transition (4T24A2) is spin-allowed, contrary to the 2E → 4A2 one, the lifetime drastically decreases with the increase in temperature leading to an impressive high sensitivity value of 4.1% °C−1 at 4 °C and an exceptional temperature resolution of 0.025 °C. According to their optical features, MgTiO3:Mn4+ nanoparticles are indeed suitable candidates for the luminescence temperature probes at the nanoscale over several temperature ranges.

Luminescence properties of MgTiO3 nanoparticles doped with Mn4+ ions are investigated for precise temperature determination.  相似文献   
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