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   9659篇
  免费   488篇
  国内免费   96篇
耳鼻咽喉   153篇
儿科学   186篇
妇产科学   171篇
基础医学   1141篇
口腔科学   231篇
临床医学   832篇
内科学   2715篇
皮肤病学   182篇
神经病学   1041篇
特种医学   286篇
外科学   1213篇
综合类   34篇
预防医学   435篇
眼科学   113篇
药学   575篇
中国医学   43篇
肿瘤学   892篇
  2023年   65篇
  2022年   136篇
  2021年   283篇
  2020年   171篇
  2019年   210篇
  2018年   273篇
  2017年   185篇
  2016年   249篇
  2015年   301篇
  2014年   341篇
  2013年   522篇
  2012年   821篇
  2011年   699篇
  2010年   441篇
  2009年   411篇
  2008年   648篇
  2007年   677篇
  2006年   601篇
  2005年   642篇
  2004年   568篇
  2003年   456篇
  2002年   452篇
  2001年   86篇
  2000年   78篇
  1999年   70篇
  1998年   83篇
  1997年   73篇
  1996年   44篇
  1995年   50篇
  1994年   45篇
  1993年   36篇
  1992年   33篇
  1991年   45篇
  1990年   32篇
  1989年   33篇
  1988年   32篇
  1987年   32篇
  1986年   27篇
  1985年   35篇
  1984年   25篇
  1983年   19篇
  1982年   19篇
  1981年   24篇
  1980年   37篇
  1979年   14篇
  1978年   10篇
  1977年   12篇
  1976年   12篇
  1975年   12篇
  1974年   6篇
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
81.
We examined the role of cell surface clustering of beta2-integrin caused by protein kinase C (PKC)-activated-cPLA2 in adhesion of eosinophilic AML14.3D10 (AML) cells. Phorbol 12-myristate 13-acetate (PMA) caused time- and concentration-dependent adhesion of AML cells to plated bovine serum albumin (BSA), which was blocked by anti-CD11b or anti-CD18 monoclonal antibodies (mAb) directed against beta2-integrin. Inhibition of PKC with Ro-31-8220 or rottlerin blocked PMA-induced cell adhesion in a concentration-dependent fashion. Inhibition of cytosolic phospholipase A2 (cPLA2) with trifluoromethyl ketone or methyl arachidonyl fluorophosphonate also blocked PMA-induced cell adhesion. PMA caused time-dependent p42/44 mitogen-activated protein kinase (MAPK) (ERK) phosphorylation in these cells. U0126, a MAPK/extracellular signal-regulated protein kinase kinase (MEK) inhibitor, at the concentrations that blocked PMA-induced ERK phosphorylation, had no effect on PMA stimulated AML cell adhesion. Neither p38 MAPK nor c-Jun N-terminal kinase (JNK) was phosphorylated by PMA. PMA also caused increased cPLA2 activity, which was inhibited by Ro-31-8220, but not U0126. Confocal immunofluorescence microscopy showed that PMA caused clustering of CD11b on the cell surface, which was blocked by either PKC or cPLA2 inhibition. PMA stimulation also caused up-regulation of CD11b on the AML cell surface. However, this up-regulation was not affected by cPLA2- or PKC-inhibition. Using the mAb, CBRM1/5, we also demonstrated that PMA does not induce the active conformation of CD11b/CD18. Our data indicate that PMA causes AML cell adhesion through beta2-integrin by PKC activation of cPLA2. This pathway is independent of MEK/ERK and does not require change of CD11b/CD18 to its active conformation. We find that avidity caused by integrin surface clustering - rather than conformational change or up-regulation of CD11b/CD18 - causes PMA stimulated adhesion of AML cells.  相似文献   
82.
Background: The restrictions taken to control the rapid spread of COVID-19 resulted in a sudden, unprecedented change in people’s lifestyle, leading to negative consequences on general health. This study aimed to estimate the impact of such changes on migraine severity during 2020 March–May lockdown. Methods: Patients affected by migraine with or without aura, diagnosed by expert physicians, completed a detailed interview comprehensive of: assessment of migraine characteristics; measure of physical activity (PA) levels; measure of the intake frequency of main Italian foods; the Insomnia Severity Index (ISI) questionnaire investigating sleep disorders. Results: We included 261 patients with a mean age of 44.5 ± 12.3 years. During social distancing, 72 patients (28%) reported a headache worsening, 86 (33%) an improvement, and 103 (39%) a stable headache frequency. A significant decrease of the PA levels during COVID-19 quarantine in the whole study sample was observed (median total metabolic equivalent task (METs) decreased from 1170 to 510; p < 0.001). Additionally, a significant difference was reported on median ISI scores (from 7 to 8; p < 0.001), which were increased in patients who presented a stable or worsening headache. Conclusions: Our study confirmed that the restrictions taken during the pandemic have affected the practice of PA levels and sleep quality in migraine. Hence, PA and sleep quality should be assessed to find strategies for an improvement in quality of life.  相似文献   
83.
Current treatment recommendations for non-alcoholic fatty liver disease (NAFLD) rely heavily on lifestyle interventions. The Mediterranean diet and physical activity, aiming at weight loss, have shown good results in achieving an improvement of this liver disease. However, concerns related to compliance and food accessibility limit the feasibility of this approach, and data on the long-term effects on liver-related outcomes are lacking. Insulin resistance is a central aspect in the pathophysiology of NAFLD; therefore, interventions aiming at the improvement of insulin sensitivity may be preferable. In this literature review, we provide a comprehensive summary of the available evidence on nutritional approaches in the management of NAFLD, involving low-calorie diets, isocaloric diets, and the novel schemes of intermittent fasting. In addition, we explore the harmful role of single nutrients on liver-specific key metabolic pathways, the role of gene susceptibility and microbiota, and behavioral aspects that may impact liver disease and are often underreported in clinical setting. At present, the high variability in terms of study populations and liver-specific outcomes within nutritional studies limits the generalizability of the results and highlights the urgent need of a tailored and standardized approach, as seen in regulatory trials in Non-Alcoholic Steatohepatitis (NASH).  相似文献   
84.
Maternal and Child Health Journal - To measure the association between dental and medical insurance with the receipt of dental cleaning during pregnancy. We analyzed Pregnancy Risk Assessment...  相似文献   
85.
The determinants of the susceptibility to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection and severe coronavirus disease 2019 (COVID-19) manifestations are yet not fully understood. Amino-bisphosphonates (N-BPs) have anti-inflammatory properties and have been shown to reduce the incidence of lower respiratory infections, cardiovascular events, and cancer. We conducted a population-based retrospective observational cohort study with the primary objective of determining if oral N-BPs treatment can play a role in the susceptibility to development of severe COVID-19. Administrative International Classification of Diseases, Ninth Revision, Clinical ModificationI (ICD-9-CM) and anatomical-therapeutic chemical (ATC) code data, representative of Italian population (9% sample of the overall population), were analyzed. Oral N-BPs (mainly alendronate and risedronate) were included in the analysis, zoledronic acid was excluded because of the low number of patients at risk. Incidence of COVID-19 hospitalization was 12.32 (95% confidence interval [CI], 9.61–15.04) and 11.55 (95% CI, 8.91–14.20), of intensive care unit (ICU) utilization because of COVID-19 was 1.25 (95% CI, 0.38–2.11) and 1.42 (95% CI, 0.49–2.36), and of all-cause death was 4.06 (95% CI, 2.50–5.61) and 3.96 (95% CI, 2.41–5.51) for oral N-BPs users and nonusers, respectively. Sensitivity analyses that excluded patients with prevalent vertebral or hip fragility fractures and without concomitant glucocorticoid treatment yielded similar results. In conclusion, we found that the incidence of COVID-19 hospitalization, intensive care unit (ICU) utilization, and COVID-19 potentially related mortality were similar in N-BPs–treated and nontreated subjects. Similar results were found in N-BPs versus other anti-osteoporotic drugs. We provide real-life data on the safety of oral N-BPs in terms of severe COVID-19 risk on a population-based cohort. Our results do not support the hypothesis that oral N-BPs can prevent COVID-19 infection and/or severe COVID-19; however, they do not seem to increase the risk. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).  相似文献   
86.
87.
BackgroundWe aim to evaluate the impact of multiparametric magnetic resonance imaging and fusion-target biopsy for early reclassification of patients with low-risk Prostate Cancer in a randomized trial.Materials and methodsBetween 2015 and 2018, patients diagnosed with Prostate Cancer after random biopsy fulfilling PRIAS criteria were enrolled and centrally randomized (1:1 ratio) to study group or control group. Patients randomized to study group underwent multiparametric magnetic resonance imaging at 3 months from enrollment: patients with positive findings (PIRADS-v2>2) underwent fusion-target biopsy; patients with negative multiparametric magnetic resonance imaging or confirmed ISUP - Grade Group 1 at fusion-target biopsy were managed according to PRIAS schedule and 12-core random biopsy was performed at 12 months. Patients in control group underwent PRIAS protocol, including a confirmatory 12-core random biopsy at 12 months. Primary endpoint was a reduction of reclassification rate at 12-month random biopsy in study group at least 20% less than controls. Reclassification was defined as biopsy ISUP Grade Group 1 in >2 biopsy cores or disease upgrading.ResultsA total of 124 patients were randomized to study group (n = 62) or control group (n = 62). Around 21 of 62 patients (34%) in study group had a positive multiparametric magnetic resonance imaging, and underwent fusion-target biopsy, with 11 (17.7%) reclassifications. Considering the intention-to-treat population, reclassification rate at 12-month random biopsy was 6.5% for study group and 29% for control group, respectively (P < 0.001).ConclusionsThe early employment of multiparametric magnetic resonance imaging for active surveillance patients enrolled after random biopsy consents to significantly reduce reclassifications at 12-month random biopsy.  相似文献   
88.

Since the emergence of the COVID-19 pandemic, there has been an increasing body of research focused on the effects that measures like stay-at-home orders and social distancing are having on other aspects of health, including mental health and sexual health. Currently, there are limited extant data on the effects of the pandemic on sexual and gender minorities. Between April 15, 2020, and May 15, 2020, we invited participants in an ongoing U.S. national cohort study (Together 5000) to complete a cross-sectional online survey about the pandemic, and its effects on mental and sexual health and well-being (n?=?3991). Nearly all (97.7%) were living in an area where they were told they should only leave their homes for essentials. Most (70.1%) reported reducing their number of sex partners as a result of the pandemic. Among the 789 participants prescribed HIV pre-exposure prophylaxis (PrEP), 29.9% said they stopped taking their PrEP entirely, and 14.2% started selectively skipping doses. For those who had been taking PrEP, discontinuing PrEP was associated with having no new sex partners (β?=?0.90, 95% CI 0.40–1.40). Among the 152 HIV-positive participants, 30.9% said they were unable to maintain an HIV-related medical appointment because of the pandemic and 13.8% said they had been unable to retrieve HIV medications. Additionally, 35.3% of participants were experiencing moderate to severe anxiety because of the pandemic and 36.7% reported symptoms of depression. In a multivariable logistic regression, reporting a new sex partner in the prior 30 days was significantly associated with being aged 30 or older (vs. not, AOR?=?1.21), being Black (AOR?=?1.79) or Latinx (AOR?=?1.40, vs. white), and being unsure if they had been in close contact with someone diagnosed with COVID-19 (AOR?=?1.32, vs. no contact). It was unassociated with COVID-19-induced anxiety, depression, or knowing someone hospitalized with COVID-19. The pandemic has caused disruptions in sexual behavior (partner reduction) as well as difficulties navigating PrEP and HIV care continua. Findings will guide more comprehensive public health responses to optimize HIV prevention and treatment in the era of COVID-19.

  相似文献   
89.
Dendritic cells (DC) are key components of innate and adaptive immune responses. Plasmacytoid DC (PDC) are a specialized DC subset that produce high amounts of type I interferons in response to microbes. High mobility group box 1 protein (HMGB1) is an abundant nuclear protein, which acts as a potent pro-inflammatory factor when released extracellularly. We show that HMGB1 leaves the nucleus of maturing PDC following TLR9 activation, and that PDC express on the plasma membrane the best-characterized receptor for HMGB1, RAGE. Maturation and type I IFN secretion of PDC is hindered when the HMGB1/RAGE pathway is disrupted. These results reveal HMGB1 and RAGE as the first known autocrine loop modulating the maturation of PDC, and suggest that antagonists of HMGB1/RAGE might have therapeutic potential for the treatment of systemic human diseases.  相似文献   
90.
The spin-echo procedure is the basic technique in a magnetic resonance (MR) study (the magnetization vector is flipped by 90° onto the ortogonal plane to the main magnetic field). Very soon after the MR procedure was developed, it was pointed out how important it is to achieve the needed contrast with shorter repetition times (TRs) to reduce the imaging time. Recently, fast imaging techniques have been introduced (partial flip angles, short TRs, and the lack of 180° radiofrequency pulses to refocus the spins are their main characteristics; the spins are refocused by the application of a gradient reversal technique). These techniques are particularly needed in pediatric neuroradiology, where the examination time must be as short as possible. At present, partial flip-angle techniques are almost completely replacing the conventional spin-echo procedure, but the variations in flip angle could result in a change in contrast. For these reasons, conventional spin-echo techniques may still be useful in a routine MR study.Presented at the 11th Meeting of the European Society for Paediatric Neurosurgery, Naples 1988  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