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   641篇
  免费   25篇
  国内免费   12篇
耳鼻咽喉   2篇
儿科学   10篇
妇产科学   47篇
基础医学   55篇
口腔科学   37篇
临床医学   36篇
内科学   140篇
皮肤病学   8篇
神经病学   65篇
特种医学   44篇
外科学   174篇
预防医学   15篇
眼科学   13篇
药学   11篇
中国医学   4篇
肿瘤学   17篇
  2023年   9篇
  2022年   14篇
  2021年   27篇
  2020年   11篇
  2019年   11篇
  2018年   22篇
  2017年   11篇
  2016年   19篇
  2015年   25篇
  2014年   32篇
  2013年   31篇
  2012年   43篇
  2011年   51篇
  2010年   22篇
  2009年   15篇
  2008年   39篇
  2007年   48篇
  2006年   31篇
  2005年   37篇
  2004年   32篇
  2003年   25篇
  2002年   13篇
  2001年   7篇
  2000年   10篇
  1999年   12篇
  1998年   3篇
  1997年   10篇
  1996年   5篇
  1995年   4篇
  1994年   5篇
  1993年   2篇
  1992年   5篇
  1991年   5篇
  1990年   7篇
  1989年   5篇
  1988年   4篇
  1987年   5篇
  1986年   2篇
  1982年   4篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1973年   2篇
  1971年   1篇
  1969年   1篇
  1966年   1篇
  1954年   1篇
  1933年   2篇
排序方式: 共有678条查询结果,搜索用时 15 毫秒
101.
The aim of the present article was to investigate the oogenic cycle of Mytilus galloprovincialis sampled in the Bay of Naples, and to immunolocalize 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD), and P450 aromatase, enzymes involved in the synthesis of two sex hormones: testosterone and 17β-estradiol. We demonstrate that the oogenic cycle starts in late summer-early fall and continues in early winter when the first event of spawning occurs; other spawning events take place until June, when the ovary is spent and contains a few empty ovarian follicles and numerous somatic cells, that is, adipogranular cells and vesicular connective tissue cells. During the oogenic cycle, apoptotic events occur at the level of oogonia, previtellogenic oocytes, as well as follicle cells; by contrast, necrosis events probably take place in vitellogenic oocytes, which, once degenerated, transfer their content to healthy oocytes. Finally, the present data demonstrate that 3β-HSD, 17β-HSD, and P450 aromatase are present in the ovary both during the reproductive and nonreproductive phases. The possible role of these enzymes during the Mytilus galloprovincialis reproductive cycle is discussed. Anat Rec, 302:1039–1049, 2019. © 2019 Wiley Periodicals, Inc.  相似文献   
102.
BACKGROUND: Little information is available about the relationships between Helicobacter pylori cytotoxin-associated protein (CagA) and clinicopathologic features in children. The purpose of this study was to test whether determining serum IgG antibodies to CagA is a useful tool for detecting more severe disease. METHODS: One hundred twenty-seven consecutive children (age range, 0.75-17.8 years; median, 9.4 years) referred for gastroscopy were included in the study. Antral and corpus biopsies were taken for gastric histology and H. pylori detection. Major symptoms and endoscopic findings were recorded. A serum sample was drawn from each child and assayed for IgG antibodies CagA by a commercial enzyme-linked immunosorbent assay. RESULTS: Sixty-three (50%) children had no evidence of H. pylori infection, 28 (22%) were H. pylori positive/CagA positive, and 36 (28%) were H. pylori positive/CagA negative. There were no differences in clinical diagnosis and occurrence of any predominant symptom according to H. pylori and CagA status. Findings of antral nodularity were more frequent (p = 0.003) in H. pylori-positive/CagA-positive children than in H. pylori-positive/CagA-negative children. The gastritis score was significantly higher in H. pylori-positive/CagA-positive children than in H. pylori-positive/CagA-negative children (5.7 +/- 1.9 vs. 3.8 +/- 1.6, respectively; p = 0.0003), either in the antral (p = 0.0002) or in the corpus (p = 0.001) mucosa. Inflammation (p = 0.0001) and activity (p = 0.0001) scores were both higher in H. pylori-positive/CagA-positive children than in H. pylori-positive/CagA-negative children, but the H. pylori density score was not significantly different (p = NS). In no case was normal gastric mucosa found in H. pylori-positive/ CagA-positive children. Lymphocytic gastritis (p = 0.0008) and lymphoid follicles (p = 0.000003) were a more frequent finding in H. pylori-positive children than in H. pylori negative children, irrespective of CagA status. CONCLUSION: Testing for serum IgG to CagA detects higher grades of gastric inflammation among children with H. pylori infection. It may be useful in targeting H. pylori-positive/ CagA-positive children for antimicrobial therapy while reducing the need for endoscopy and gastric biopsy.  相似文献   
103.
AIM: To examine neuroretinal function by using the multifocal electroretinography (mfERG) test in patients with neurofibromatosis type 1 (NF1) without optic pathway gliomas (OPGs). METHODS: This study was conducted on 35 patients (35 eyes) with NF1 and 30 healthy subjects (30 eyes) for the control group. Each subject underwent a complete ophthalmological examination including spectral domain-optical coherence tomography (SD-OCT) and mfERG. The 1.5-Tesla magnetic resonance imaging (MRI) scan of the brain was performed in NF1 patients to assess the presence of OPGs. All participants were recruited having a best corrected visual acuity (BCVA) of no less than 20/20 in each eye. The amplitude and implicit time of the P1 wave (first-order Kernel component) were evaluated on mfERG. Data analysis was carried out in the two central degrees and in the four quadrants from two to 25 degrees of visual field. RESULTS: Statistically significant results were obtained for the P1 wave amplitudes in the 4 quadrants in NF1 patients compared to healthy controls, while the reduction was not significant in the 2 central degrees between the groups. A statistically significant difference was observed among the P1 wave amplitudes as recorded in the 4 quadrants within the NF1 group, with lower amplitudes detected in the nasal quadrants. No differences in the implicit times were recorded in the 2 central degrees and in the 4 quadrants as compared between NF1 patients and controls. CONCLUSION: Impaired neuroretinal function in NF1 patients is expressed in a decreased amplitude of the P1-wave between 2 and 25 central retinal degrees on mfERG. Altered intracellular signal transduction due to abnormal neurofibromin-mediated cyclic adenosine monophosphate (cAMP) generation, can be involved. The possible use of mfERG as subclinical retinal damage indicator has a potential utility in clinical practice for the follow-up of NF1 patients.  相似文献   
104.

Purpose

Syncope is a common condition that affects individuals of all ages and is responsible for 1–3% of all emergency department (ED) visits. Prospective studies on syncope are often limited by the exiguous number of subjects enrolled. A possible alternative approach would be to use of hospital discharge diagnoses from administrative databases to identify syncope subjects in epidemiological observational studies. We assessed the accuracy of the International Classification of Diseases, Ninth Revision (ICD-9) code 780.2 “syncope and collapse” to identify patients with syncope.

Methods

Patients in two teaching hospitals in Milan, Italy with a triage assessment for ED access that was possibly related to syncope were recruited in this study. We considered the index test to be the attribution of the ICD-9 code 780.2 at ED discharge and the reference standard to be the diagnosis of syncope by the ED physician.

Results

The sensitivity, specificity, positive and negative predictive values of the ICD-9 code 780.2 to identify patients with syncope were 0.63 (95% confidence interval [CI] 0.58–0.67), 0.98 (95% CI 0.98–0.99), 0.83 (95% CI 0.79–0.87) and 0.95 (95% CI 0.94–0.95), respectively.

Conclusions

The moderate sensitivity of ICD-9 code 780.2 should be considered when the code is used to identify patients with syncope through administrative databases.
  相似文献   
105.
106.
BackgroundWhile sleeve gastrectomy (SG) has lower perioperative risk compared with Roux-en-Y gastric bypass (RYGB), long-term data about their differential impact on overall health are unclear. Hospital use after bariatric surgery is an important parameter for improving peri- and postoperative care.ObjectiveThis present study was aimed to compare SG and RYGB in terms of their effect on long-term hospital-based healthcare utilization.SettingMulticenter, statewide database.MethodsA retrospective cohort study of adult patients who underwent SG and RYGB between 2009 and 2011, with follow-up until 2015 and 2-year presurgery information. Propensity score–matched SG and RYGB groups were created using preoperative demographic characteristics, co-morbidities, and presurgery hospital use, measured by cumulative length of stay (LOS) and frequency of emergency department visits. Postsurgery yearly LOS, incidence of hospital visits, and the reason for the visit were compared. Primary outcomes included postoperative hospital visits during years 1 to 4 after bariatric surgery and cumulative LOS. Secondary outcomes included specific reasons for hospital use.ResultsThere were 3540 SG and 13,587 RYGB patients, whose mean (95% confidence interval [CI]) LOS was 1.3 (1.3–1.4), .9 (.8–1), 1 (.9–1.1), and 1.2 (1–1.3) days at years 1 through 4, respectively. Postoperative yearly LOS was similar between the 2 propensity-matched groups. The risk of hospitalizations (odd ratio .73, 95% CI .64–.84, P < .0001) and emergency department visits (odds ratio .84, 95% CI .75–.95, P = .005) was significantly lower for SG, during the first postoperative year. The reverse was seen at the fourth postoperative year, with higher risk of emergency department use after SG (odds ratio 1.16, 95% CI 1.01–1.33, P = .035).ConclusionPostoperative 4-year hospital utilization remains low for both SG and RYGB. The previously established lower early perioperative risk of SG was not appreciated for longer-term hospital use compared with RYGB.  相似文献   
107.
Bacterial infections directly affect the world's population, and this situation has been aggravated by indiscriminate use of antimicrobial agents, which can generate resistant microorganisms. In this report, an initial screening of proteins with antibacterial activity from corms of 15 species of the Xanthosoma genus was conducted. Since Xanthosoma blandum corms showed enhanced activity toward bacteria, a novel protein with bactericidal activity was isolated from this particular species. Edman degradation was used for protein N-termini determination; the primary structure showed similarities with Kunitz inhibitors, and this protein was named Xb-KTI. This protein was further challenged against serine proteinases from different sources, showing clear inhibitory activities. Otherwise, no hemolytic activity was observed for Xb-KTI. The results demonstrate the biotechnological potential of Xb-KTI, the first proteinase inhibitor with antimicrobial activity described in the Xanthosoma genus.  相似文献   
108.
Granulin is a soluble cofactor for toll-like receptor 9 signaling   总被引:1,自引:0,他引:1  
Toll-like receptor (TLR) signaling plays a critical role in innate and adaptive immune responses and must be tightly controlled. TLR4 uses LPS binding protein, MD-2, and CD14 as accessories to respond to LPS. We therefore investigated the presence of an analagous soluble cofactor that might assist in the recruitment of CpG oligonucleotides (CpG-ODNs) to TLR9. We report the identification of granulin as?an essential secreted cofactor that potentiates TLR9-driven responses to CpG-ODNs. Granulin, an unusual cysteine-rich protein, bound to CpG-ODNs and interacted with TLR9. Macrophages from granulin-deficient mice showed not only impaired delivery of CpG-ODNs to endolysosomal compartments, but?also decreased interaction of TLR9 with CpG-ODNs. As a consequence, granulin-deficient macrophages showed reduced responses to stimulation with CpG-ODNs, a trait corrected by provision of exogenous granulin. Thus, we propose that granulin contributes to innate immunity as a critical soluble cofactor for TLR9 signaling.  相似文献   
109.
Carpal tunnel syndrome (CTS) is one of the most common upper limb compression neuropathies. In only 50% of cases it is possible to identify a cause. Our objective was to determine the role of glucose metabolism abnormalities in idiopathic CTS. We identified 117 patients with idiopathic moderate or severe CTS and 128 controls. In all we evaluated glucose and insulin levels at fasting and after 2-h oral glucose tolerance test (2h-OGTT). In addition we determined insulin resistance (IR). Following OGTT the prevalence of glucose metabolism abnormalities was significantly higher in the CTS group (p = 0.001). IR was documented in 80% of patients, of whom 45% had impaired glucose tolerance, 14% newly diagnosed diabetes mellitus, and 20% IR only. Waist circumference and body mass index were also significantly increased in the CTS group. In this study, we focused on evidence that pre-diabetes may represent a risk factor for CTS. We proposed to determine IR as a rule in all patients with idiopathic CTS.  相似文献   
110.
Brain near-infrared spectroscopy (NIRS) is an emerging neurophysiological tool that combines straightforward activity localization with cost-economy, portability and patient compatibility. NIRS is proving its empirical utility across specific cognitive and emotional paradigms. However, a potential limitation is that it is not only sensitive to haemodynamic changes taking place in the cortex, and task-related cardiovascular responses expressed in the perfusion of extracranial layers may be confounding. Existing literature reports correlations between brain NIRS and systemic blood pressure, yet it falls short of establishing whether in normal participants the blood pressure changes encountered in experimental settings can have confounding effects. Here, we tested this hypothesis by performing two experimental manipulations while recording from superficial occipital cortex, encompassing striate and extrastriate regions. Visual stimulation with reversing chequerboards evoked cortical haemodynamic responses. Simultaneously and independently, transient systemic blood pressure changes were generated through rapid arm-raising. Shallow-penetration NIRS recordings, probing only extra-cerebral tissues, highlighted close haemodynamic coupling with blood pressure. A different coupling pattern was observed in deep-penetration recordings directed at haemodynamic signals from visual cortex. In absence of blood-pressure changes, NIRS signals tracked differences in visual stimulus duration. However when blood pressure was actively manipulated, this effect was absent and replaced by a very large pressure-related response. Our observations demonstrate that blood pressure fluctuations can exert confounding effects on brain NIRS, through expression in extracranial tissues and within the brain itself. We highlight the necessity for continuous blood pressure monitoring alongside brain NIRS, and for further research on methods to correct for physiological confounds.  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