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   3763篇
  免费   198篇
  国内免费   20篇
耳鼻咽喉   20篇
儿科学   128篇
妇产科学   77篇
基础医学   538篇
口腔科学   130篇
临床医学   298篇
内科学   862篇
皮肤病学   36篇
神经病学   353篇
特种医学   136篇
外科学   699篇
综合类   16篇
预防医学   144篇
眼科学   25篇
药学   299篇
中国医学   18篇
肿瘤学   202篇
  2023年   20篇
  2022年   43篇
  2021年   84篇
  2020年   55篇
  2019年   79篇
  2018年   101篇
  2017年   74篇
  2016年   82篇
  2015年   87篇
  2014年   124篇
  2013年   190篇
  2012年   257篇
  2011年   249篇
  2010年   120篇
  2009年   125篇
  2008年   200篇
  2007年   247篇
  2006年   239篇
  2005年   169篇
  2004年   164篇
  2003年   164篇
  2002年   147篇
  2001年   120篇
  2000年   125篇
  1999年   87篇
  1998年   32篇
  1997年   30篇
  1996年   23篇
  1995年   22篇
  1994年   15篇
  1992年   37篇
  1991年   45篇
  1990年   48篇
  1989年   36篇
  1988年   35篇
  1987年   39篇
  1986年   24篇
  1985年   28篇
  1984年   22篇
  1983年   22篇
  1981年   10篇
  1980年   10篇
  1979年   17篇
  1978年   10篇
  1977年   13篇
  1976年   11篇
  1974年   12篇
  1973年   9篇
  1972年   11篇
  1965年   10篇
排序方式: 共有3981条查询结果,搜索用时 15 毫秒
81.
Intramyocardial dissecting hematoma is an uncommon complication of myocardial infarction potentially leading to cardiac rupture. The aim of the present study was to investigate coronary reperfusion results, left ventricular (LV) function recovery and remodeling and clinical outcomes in patients with anterior STEMI complicated by intramyocardial hematoma. We prospectively studied 87 patients (mean age 59?±?10 years; 88% male) with anterior STEMI (42 with intramyocardial hematoma) in order to evaluate coronary reperfusion results, LV remodeling (≥15% increase in end-systolic volume) and clinical outcomes (cardiac death, non-fatal reinfarction, and hospitalization for congestive heart failure) at 24 months. Thrombolysis in myocardial infarction (TIMI) flow score and myocardial blush grade (MBG) were assessed both pre- and post-percutaneous coronary intervention (PCI) and speckle-tracking echocardiography was performed post PCI and at 6-month follow-up. Patients with hematoma had lower post-PCI TIMI score and MBG, higher heart rate, worse LV ejection fraction and longitudinal or rotational function than their counterparts. LV remodeling occurred in 33 (78.6%) patients with hematoma and 11 (24.4%) patients without (p?<?0.001). Independent predictors of LV remodeling were heart rate (p?=?0.018), MBG (p?=?0.036) and presence of hematoma (p?<?0.001). Hematoma (log-rank test, χ2?=?9.849; p?=?0.002) and LV remodeling (log-rank test, χ2?=?13.770; p?<?0.001) were associated to a higher rate of adverse events. Cox analysis identified LV remodeling as the only independent predictor of adverse events (hazard ratio?=?3.912; 95% confidence interval, 1.429–10.714; p?=?0.008). Intramyocardial dissecting hematoma complicating anterior STEMI is an independent determinant of LV remodeling and is associated to poor prognosis.  相似文献   
82.

Purpose

Diffuse remodeling of myocardial extra-cellular matrix is largely responsible for left ventricle (LV) dysfunction and arrhythmias. Our hypothesis is that the texture analysis of late iodine enhancement (LIE) cardiac computed tomography (cCT) images may improve characterization of the diffuse extra-cellular matrix changes. Our aim was to extract volumetric extracellular volume (ECV) and LIE texture features of non-scarred (remote) myocardium from cCT of patients with recurrent ventricular tachycardia (rVT), and to compare these radiomic features with LV-function, LV-remodeling, and underlying cardiac disease.

Procedures

Forty-eight patients suffering from rVT were prospectively enrolled: 5/48 with idiopathic VT (IVT), 23/48 with post-ischemic dilated cardiomyopathy (ICM), 9/48 with idiopathic dilated cardiomyopathy (IDCM), and 11/48 with scars from a previous healed myocarditis (MYO). All patients underwent echocardiography to assess LV systolic and diastolic function and cCT with pre-contrast, angiographic, and LIE scan to obtain end-diastolic volume (EDV), ECV, and first-order texture parameters of Hounsfield Unit (HU) of remote myocardium in LIE [energy, entropy, HU-mean, HU-median, standard deviation (SD), and mean absolute deviation (MAD)].

Results

Energy, HU mean, and HU median by cCT texture analysis correlated with ECV (rho?=?0.5650, rho?=?0.5741, rho?=?0.5068; p?<?0.0005). cCT-derived ECV, HU-mean, HU-median, SD, and MAD correlated directly to EDV by cCT and inversely to ejection fraction by echocardiography (p?<?0.05). SD and MAD correlated with diastolic function by echocardiography (rho?=?0.3837, p?=?0.0071; rho?=?0.3330, p?=?0.0208). MYO and IVT patients were characterized by significantly lower values of SD and MAD when compared with ICM and IDCM patients, independently of LV-volume systolic and diastolic function.

Conclusions

Texture analysis of LIE may expand cCT capability of myocardial characterization. Myocardial heterogeneity (SD and MAD) was associated with LV dilatation, systolic and diastolic function, and is able to potentially identify the different patterns of structural remodeling characterizing patients with rVT of different etiology.
  相似文献   
83.
The use of cranial and caudal angulated views in the angiographic evaluation of the right coronary artery (RCA) was assessed in 61 patients. Each patient had a standard LAO and RAO view, followed by one or more angled views. The standard LAO view showed the area about the origin of the posterior descending artery (PD0) adequately in 33 of 46 patients (72% ), and the mid and distal portions of the posterior descending artery (PDm&d) adequately in 26/46 (56% ). The standard RAO view showed the PD0 adequately in only 17/46 (37% ) and the PDm&d adequately in 41/46 (89% ). With the LAO cranial view, however, the PD0 was seen well in 45/46 (98% ), and PDm&d was seen well in 44/46 (96% ). The RAO angled views, although of more limited utility, also afforded improved visualization of the distal segments of the RCA. We recommend the use of angled views in the evaluation of the right coronary artery, as these views, particularly the LAO cranial view, afford improved visualization of the distal segments of the RCA.  相似文献   
84.
In the present study we have tested the direct effects of transforming growth factor-beta 1 (TGF beta 1) on lactate production by Sertoli cells isolated from immature porcine testes. In Sertoli cells cultured in a defined medium, TGF beta 1 was shown to stimulate lactate production in a time- and dose-dependent manner. The maximal and half-maximal effects of TGF beta 1 on lactate production were obtained in the picomolar concentration range, respectively 24 and 8 pM TGF beta 1. TGF beta 1 action was found closely related to that of insulin since 1) both TGF beta 1 (40 pM) and insulin (1 microgram/ml) induced the secretion of similar and nonadditive amounts of lactate; and 2) TGF beta 1 and insulin induced comparable increases in lactate production in FSH (1 microgram/ml)-treated Sertoli cells. Because lactate is derived from glucose, 2-deoxy-D-glucose (2-DOG) was used to investigate the hexose transport system of Sertoli cells after insulin, FSH, and TGF beta 1 treatments. Insulin (1 microgram/ml) and FSH (1 microgram/ml) were found to stimulate 2-DOG transport with a similar time course, with an effect detected up to 30 min and maximal at 150 min. In contrast, although TGF beta 1 also enhanced 2-DOG uptake by Sertoli cells, the increase in glucose transport was delayed, since the TGF beta 1 effect was first detected at 150 min and was maximal at 360 min. These effects of TGF beta 1 action on Sertoli cell activity are exerted through specific membrane TGF beta 1 receptors. Scatchard analysis of the binding of TGF beta 1 to cultured Sertoli cells revealed the presence of both a high affinity (Kd, approximately 180 pM) and a low affinity binding site systems for TGF beta 1. Affinity labeling of these receptors by covalent attachment to [125I] TGF beta 1 with disuccinimidyl suberate and subsequent electrophoretic analysis of the labeled complexes revealed the specific binding of [125I] TGF beta 1 to three predominant molecules of 260, 130, and 70 kDa. In conclusion, the present study demonstrates that testicular Sertoli cells are targets for TGF beta 1 action. In view of the importance of lactate as a substrate for germ cells, it is suggested that TGF beta 1 might also be involved in the development of normal germinal epithelium.  相似文献   
85.
86.
BACKGROUND & AIMS: Celiac disease (CD) has been associated with several genetic disorders, but has not been associated with hereditary fructose intolerance (HFI). METHODS: We identified CD in 4 female patients affected by HFI from among 38 Italian HFI patients. RESULTS: Three of these patients were children in whom the CD-associated signs were hypertransaminasemia, failure to thrive, low weight, and short stature, whereas the adult patient had protracted diarrhea notwithstanding a fructose-free diet. The incidence of CD in our group of HFI patients was higher (>10%) than in the general population (1%-3%) (P<.02). CONCLUSIONS: The possibility of an association between these 2 gastrointestinal disorders is important, particularly in the management of HFI patients with persisting symptoms.  相似文献   
87.
OBJECTIVES: This study was designed to compare the three-year survival after percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery (CABG) in physician-directed and patient-choice registries with the Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) randomized trial results. BACKGROUND: The AWESOME multicenter randomized trial and registry compared the long-term survival after PCI and CABG for the treatment of patients with medically refractory myocardial ischemia and at least one additional risk factor for adverse outcome with CABG. The randomized trial demonstrated comparable three-year survival. METHODS: Over a five-year period (1995 to 2000), 2,431 patients with medically refractory myocardial ischemia and at least one of five risk factors (prior heart surgery, myocardial infarction within seven days, left ventricular ejection fraction <0.35, age >70 years, intra-aortic balloon required to stabilize) were identified. By physician consensus, 1,650 patients formed a physician-directed registry assigned to CABG (692), PCI (651) or further medical therapy (307), and 781 were angiographically eligible for random allocation; 454 of these patients constitute the randomized trial, and the remaining 327 constitute a patient choice registry. Survival for CABG and PCI was compared using Kaplan-Meier curves and log-rank tests. RESULTS: The CABG and PCI 36-month survival rates for randomized patients were 79% and 80%, respectively. The CABG and PCI 36-month survival rates were both 76% for the physician-directed subgroup; comparable survival rates for the patient-choice subgroup were 80% and 89%, respectively. None of the global log-rank tests for survival demonstrated significant differences. CONCLUSIONS: Both registries support the randomized trial conclusion: PCI is an alternative to CABG for some medically refractory high-risk patients.  相似文献   
88.

Purpose of Review

MDR-Gram-negative bacteria are a great concern in the neonatal population, with a worldwide rise in the reported incidence and with very limited therapeutic options. Acinetobacter baumannii is responsible for many infections in neonates and outbreaks in neonatal intensive care unit (NICU); also, outbreaks caused by other Acinetobacter species have been reported. The aim of this review is to document the epidemiology of Acinetobacter spp. infections in neonates and risk factors for acquisition of Acinetobacter spp. in the NICU using data from published studies.

Recent Findings

Acinetobacter spp. infections are increasing in neonates in NICU. Outbreak caused by multidrug resistant (MDR) or extensively drug resistant (XDR) A. baumannii but also outbreak caused by susceptible A. soli and A. septicus sp. nov., were reported in neonates. Acinetobacter spp. were responsible for bloodstream infections and respiratory tract infections in neonates. Risk factors for A. baumannii acquisition in neonates were low birthweight, length of NICU stay, umbilical catheterization, central-venous catheterization, assisted ventilation, and prior antibiotic use.

Summary

This review highlights the importance of surveillance of risk factors for healthcare-associated infections in NICU to control MDR and XDR A. baumannii infections in neonates.
  相似文献   
89.
Digoxin was administered to normal CD-1 mice (4 micrograms/kg per 24 hr), and the mice were inoculated intratracheally with Streptococcus pneumoniae in order to assess the effects of the cardiac glycoside on pulmonary antibacterial mechanisms. Digoxin-treated animals experienced a worse survival rate than did controls (19 of 50 versus 33 of 50; P less than .01). When challenged with a high inoculum (1 X 10(6) cfu), animals given the glycoside demonstrated a significant impairment in their capacity to clear viable pneumococci from the lungs; the depression in pulmonary clearance was associated with a marked attenuation in the ability of digoxin-treated mice to recruit granulocytes and macrophages into the bronchoalveolar spaces. Following low inoculum challenge (1 X 10(5) cfu), animals treated with the cardiac glycoside exhibited an inefficient pulmonary clearance and a blunted macrophage influx. At clinically relevant concentrations, digoxin demonstrated no effect on the in vitro pneumococcidal activity of resident murine alveolar macrophages. We conclude that digoxin can disrupt host defense against pneumococcus by impeding the normal inflammatory response to organisms deposited into the lower respiratory tract.  相似文献   
90.
Both nonreciprocal and reciprocal mitotic recombination are enhanced by the recessive mutant spo11-1, which was previously shown to affect meiosis by decreasing recombination and increasing nondisjunction. The mitotic effects are not distributed equally in all chromosomal regions. The genotypes of mitotic recombinants in spo11-1/spo11-1 diploid cells provide further evidence that widely spaced chromosomal markers undergo coincident conversion in mitosis.  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