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   5123篇
  免费   24篇
  国内免费   10篇
耳鼻咽喉   23篇
儿科学   736篇
妇产科学   208篇
基础医学   546篇
口腔科学   197篇
临床医学   165篇
内科学   1060篇
皮肤病学   207篇
神经病学   302篇
特种医学   86篇
外科学   1151篇
综合类   16篇
预防医学   96篇
眼科学   84篇
药学   156篇
中国医学   2篇
肿瘤学   122篇
  2023年   6篇
  2022年   13篇
  2021年   92篇
  2020年   12篇
  2019年   620篇
  2018年   513篇
  2017年   316篇
  2016年   14篇
  2015年   13篇
  2014年   26篇
  2013年   43篇
  2012年   24篇
  2011年   25篇
  2010年   25篇
  2009年   14篇
  2008年   18篇
  2007年   12篇
  2006年   15篇
  2005年   10篇
  2004年   6篇
  2003年   3篇
  2002年   5篇
  2001年   8篇
  2000年   3篇
  1999年   7篇
  1998年   2篇
  1997年   6篇
  1996年   3篇
  1995年   2篇
  1994年   4篇
  1993年   8篇
  1992年   4篇
  1991年   2篇
  1989年   3篇
  1987年   1篇
  1985年   264篇
  1984年   354篇
  1983年   198篇
  1982年   286篇
  1981年   280篇
  1980年   259篇
  1979年   299篇
  1978年   240篇
  1977年   218篇
  1976年   252篇
  1975年   221篇
  1974年   194篇
  1973年   211篇
  1972年   2篇
  1968年   1篇
排序方式: 共有5157条查询结果,搜索用时 15 毫秒
61.
《Pharmaceutical biology》2013,51(10):1448-1457
Abstract

Context: Convolvulus pluricaulis Chois. (Convolvulaceae), a well-known Ayurvedic “Medhya Rasayana” (nervine tonic), is extensively used for different central nervous system (CNS) disorders.

Objective: The objective of this study was to evaluate the protective effect of standardized hydro-methanol extract of C. pluricaulis (CPE) and its fractions, namely ethyl acetate (EAE), butanol (BE), and aqueous (AE), against 3-nitropropionic acid (3-NP) induced neurotoxicity in rats.

Materials and methods: The extract of the whole plant was standardized on the basis of scopoletin content (0.014%) using thin layer chromatography densitometric analysis. CPE (100 and 200?mg/kg) and its fractions, namely EAE (15 and 30?mg/kg), BE (25 and 50?mg/kg), and AE (50 and 100?mg/kg) were administered orally for 20?d. Their protective effect against 3-NP (10?mg/kg, i.p. for 14?d) was assessed by the effect on various behavioral parameters, namely body weight, locomotor activity, grip strength, gait pattern, and the effect on cognitive dysfunction. Biochemical parameters for oxidative damage were also assessed in the striatum and cortex regions of the brain.

Results: Administration of 3-NP induced HD-like symptoms that were indicated by reduced body weight, locomotor activity, memory, grip strength, and oxidative defense. CPE (200?mg/kg), EAE (30?mg/kg), and BE (50?mg/kg) significantly (p?<?0.001) attenuated 3-NP induced reduction in locomotor activity, grip strength, memory, body weight, and oxidative defense in comparison with 3-NP-treated animals on 10 and 15?d.

Conclusion: The present study suggested that CPE has a protective action against 3-NP-induced neurotoxicity and can be further explored for its efficacy against Huntington’s disease.  相似文献   
62.
63.
Abstract

Background: Huntington’s disease (HD) is a genetic, rare and progressive neurodegenerative disorder that causes motor and cognitive impairment in midlife patients. Although retinal damage was observed in animal HD models and in patients with other neurodegenerative diseases, we still need confirmation of impairment in HD patients. Optical coherence tomography (OCT) is a non-invasive methodology that analyses the retinal nerve fibre layers (RNFL) and could reflect processes of neurodegeneration.

Methods: A cross-sectional study with 14?HD patients who underwent a spectral domain OCT. Results were compared with a control group. Demographic data were also obtained.

Results: Temporal and superior RNFL sectors in HD showed a significant RNFL thinning compared with a control group. However, no differences were identified in mean total RNFL thickness between HD patients and controls.

Conclusions: OCT is a rapid and non-invasive technique that can be investigated in larger cohorts of patients to assess its potential role as a biomarker in HD patients.  相似文献   
64.
Heart failure (HF) affects 20% of nursing home (NH) residents, causing high morbidity and mortality. The optimal approach to HF management in NHs remains elusive. We conducted a scoping review of published guidelines and HF management interventions in NHs. A search for English publications since 1990 was conducted using PubMed, EMBASE, CINAHL, and Scopus, for scientific statements, guidelines, recommendations, or intervention studies that addressed at least 1 principle of HF management. Of 2545 records retrieved, 19 articles were retained after screening, and 2 additional articles identified through reference list manual searches. Six articles represented 5 guidelines and 15 described interventions. All guidelines endorsed the applicability of general HF guidelines to NH residents, tailored to comorbidities, frailty, and advance care preferences. Four addressed quality assurance but not feasibility and sustainability. Methodological quality of the interventions was poor, although results suggest that guideline-based HF management in NHs can improve nursing staff knowledge and job satisfaction, prescribing, and reduce acute care utilization. Clinically-based education for staff, and access to specialist mentorship are important. NH physician involvement was limited, and resident/family education potentially ineffective. Concerns about feasibility, sustainability, and quality assurance were identified in most interventions, and advance care planning was rarely addressed. HF guidelines for NH support the applicability of general HF guidelines to the care of NH residents, and published interventions suggest that guideline-based HF management in NHs is effective. Future work should support greater physician and resident engagement, advance care planning, and provide robust guidelines on developing feasible and sustainable interventions.  相似文献   
65.
The purpose of this study was to determine whether myocardium salvaged by reperfusion following coronary occlusion could respond to inotropic stimulation by dopamine. Mongrel dogs underwent a 2-hour occlusion of the proximal left anterior descending coronary artery, followed by reperfusion for 5 or 28 hours. Dopamine (5 to 10 micrograms/kg/min) or dextrose was administered 1 hour or 24 hours after the onset of reperfusion. Serial, computer-assisted, two-dimensional echocardiographic determination of percentage of systolic wall thickening (%SWT) and cross-sectional ejection fraction (% delta area) were used to evaluate the response to treatment. Myocardium in the region of central ischemia contracted poorly after 1 hour of reperfusion (mean %SWT = 1.3 +/- 13.3% [mean +/- SD] compared to preocclusion value of 43.6 +/- 18.5%, p less than 0.001) and tended to thin at 24 hours of reperfusion (mean %SWT = -6.0 +/- 12.3%, p less than 0.001). After 1 hour of reperfusion, dopamine produced a greater than fourfold improvement in %SWT within the reperfused zone (to 15.3 +/- 7.3%, p less than 0.05). After 24 hours of reperfusion, dopamine again produced an improvement in %SWT (to 5.8 +/- 12.5%, p less than 0.05). There were no significant changes in %SWT with dextrose infusion. Thus, dopamine stimulates the reperfusion-salvaged but noncontracting (stunned) myocardium to contract as early as 1 hour after reperfusion.  相似文献   
66.
Seventy-nine per cent of a series of 48 patients with implanted pacemakers developed arrhythmias during exercise. There were 23 patients without known previous competition, and in 69.5 per cent of them arrhythmias developed during exercise.No serious arrhythmias developed, but there were three cases of repetitive firing or short bursts of ventricular tachycardia, five instances of pacing on the apex of the T wave, and one instance of R-on-T phenomenon. None of these cases of ventricular tachycardia was preceded by spike-on-T or R-on-T stimulation.Based on these observations, recommendations for selection of the proper pacemaker have been made.  相似文献   
67.
68.
BackgroundComputed Tomography (CT) Pulmonary Angiography is the most commonly used diagnostic study for acute pulmonary embolism (PE). Echocardiogram (ECHO) is also used for risk stratification in acute PE, however the diagnostic performance of CT versus ECHO for risk stratification remains unclear.MethodsCT and ECHO right ventricle (RV) and left ventricle (LV) diameters were measured in a retrospective cohort of patients with acute PE. RV:LV diameter ratios were calculated and correlation between CT and ECHO RV:LV ratio was assessed. Sensitivity and specificity for the composite adverse events endpoint of mortality, respiratory failure requiring intubation, cardiac arrest, or shock requiring vasopressors within 30 days of admission were assessed for CT or ECHO derived RV:LV ratio alone and in combination with biomarkers (troponin or B-type natriuretic peptide).ResultsA total of 74 subjects met the inclusion criteria and had a mean age of 62±18 years. The proportion of patients with RV:LV >1 was similar when comparing CT (37.8%) versus ECHO (33.8%) (P = 0.61). A statistically significant correlation was found between CT derived and ECHO derived RV:LV diameter ratio (r = 0.832, P < 0.001). The sensitivity and specificity to predict 30-day composite adverse events for CT versus ECHO derived RV:LV diameter ratio >1 together with positive biomarker status was similar with sensitivity and specificity of 87% and 41% versus 87% and 42%, respectively.ConclusionsIn patients with acute PE, CT and ECHO RV:LV diameter ratio correlate well and identify similar proportion of PE patients at risk for early adverse events. These findings may streamline risk stratification of patients with acute PE.  相似文献   
69.
The ability of exercise radionuclide ventriculography to detect multivessel coronary artery disease in patients who survived a single myocardial infarction was assessed. Seventy-four patients who had had myocardial infarction at least 8 weeks earlier underwent cardiac catheterization and exercise radionuclide ventriculography. Thirty-eight patients had had an inferior infarction: 25 with multivessel disease and 13 with single vessel disease of the right coronary artery. Thirty-six patients had had an anterior infarction: 26 with multivessel disease and 10 with single vessel disease of the left anterior descending coronary artery.

Among patients with anterior infarction there was no significant difference between patients with single vessel disease and patients with multivessel disease with regard to resting ejection fraction, exercise ejection fraction, and the mean change from rest to exercise. Patients with single vessel disease had a decrease in ejection fraction from rest to exercise of 2.2 ± 2.7% units (mean) ± standard error [SE]), compared with a decrease of 5.4 ±1.3% units in those with multivessel disease (p = not significant [NS]). Seventeen of 26 (65%) patients with multivessel disease and 6 of 10 (60%) with single vessel disease had a decrease in ejection fraction of at least 5 percentage units (p = NS).

In patients with inferior infarction there was no difference in the mean resting ejection fraction in those with single vessel disease (53 ± 2%) compared with those with multivessel disease (50 ±2%); however, the mean exercise ejection fraction in patients with single vessel disease (57 ± 3%) was significantly higher (p < 0.005) than that in patients with multivessel disease (45 ± 2%). Sixteen of the 25 patients with multivessel disease (64%) but only 1 patient with single vessel disease (7.7%) had a decrease in ejection fraction of at least 5 percentage units (p < 0.001).

A new wall motion abnormality developed in 8 patients with anterior infarction and 11 with inferior infarction with multivessel disease and none with single vessel disease. The sensitivity and specificity in predicting multivessel disease using the criteria of the development of a new wall motion abnormality or a decrease in ejection fraction with exercise of at least 5 percentage units were 80 and 92% for the patients with inferior infarction, but only 69 and 40% for the patients with anterior infarction.

These results suggest that exercise radionuclide angiography can be used to discriminate between single and multivessel disease after inferior myocardial infarction. For patients with anterior infarction, only a new abnormality in wall motion accurately predicts multivessel disease, but this occurred in only one third of such patients.  相似文献   

70.
We observed that renal transplant recipients with good graft function (mean serum creatinine level 1.5 mg/dl ± 0.5 SD, N = 68) had dietary salt intakes (estimated from serial measurements of 24-hour sodium excretion rate) which averaged 43 percent higher than that of a comparable group of healthy subjects. There was no correlation between blood pressure levels and salt intake and, despite the high dietary salt intake, hypertension was present in only 29 patients and was usually mild; mean systolic and diastolic blood pressures were 132 ± 10 mm Hg and 89 ± 7 mm Hg, respectively white the patients were receiving ant (hypertensive medication (median number of standard doses of antihypertensive medication was 1.0 doses/ patient per day). These observations suggest that high dietary salt intake does not exert a powerful blood pressure elevating effect, since any effect of high dietary salt intake to raise blood pressure should have been magnified In the renal transplant recipients because of their reduced renal mass and their chronic glucocorticoid therapy.  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