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   3316篇
  免费   201篇
  国内免费   6篇
耳鼻咽喉   13篇
儿科学   170篇
妇产科学   58篇
基础医学   353篇
口腔科学   120篇
临床医学   322篇
内科学   588篇
皮肤病学   51篇
神经病学   343篇
特种医学   305篇
外国民族医学   3篇
外科学   229篇
综合类   55篇
一般理论   1篇
预防医学   260篇
眼科学   100篇
药学   188篇
中国医学   1篇
肿瘤学   363篇
  2021年   22篇
  2019年   23篇
  2018年   34篇
  2017年   21篇
  2016年   30篇
  2015年   36篇
  2014年   52篇
  2013年   78篇
  2012年   84篇
  2011年   103篇
  2010年   84篇
  2009年   84篇
  2008年   160篇
  2007年   143篇
  2006年   157篇
  2005年   141篇
  2004年   127篇
  2003年   131篇
  2002年   105篇
  2001年   97篇
  2000年   110篇
  1999年   96篇
  1998年   53篇
  1997年   67篇
  1996年   67篇
  1995年   49篇
  1994年   40篇
  1993年   65篇
  1992年   81篇
  1991年   77篇
  1990年   87篇
  1989年   84篇
  1988年   67篇
  1987年   71篇
  1986年   83篇
  1985年   65篇
  1984年   70篇
  1983年   50篇
  1982年   45篇
  1981年   29篇
  1980年   41篇
  1979年   57篇
  1978年   35篇
  1977年   28篇
  1976年   25篇
  1975年   30篇
  1973年   26篇
  1972年   23篇
  1970年   20篇
  1969年   27篇
排序方式: 共有3523条查询结果,搜索用时 0 毫秒
81.
82.
83.
BACKGROUND: The prognostic value of cardiac troponins (cTn) in patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS) and chronic kidney disease (CKD) is debated. HYPOTHESIS: We tested the performance of cTnI and cTnT for risk stratification in patients with CKD and evaluated the prognostic significance of cTnI and cTnT elevations by their magnitude across the range of CKD severity. METHODS: We examined correlations among cTn elevation, CKD, and in-hospital mortality in 31,586 high-risk patients with NSTE ACS included in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress ADverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines initiative (CRUSADE). Cardiac tropinins I and T levels were categorized as ratios of each site's upper limit of normal (ULN) for myocardial necrosis: normal (cTn ratio < or =1 x ULN), mild (cTn ratio > 1-3 x ULN), and major (cTn ratio > 3 x ULN) elevation. Estimated glomerular filtration rate (eGFR) was calculated using the abbreviated Modification of Diet in Renal Disease equation. Stages of CKD were categorized as normal to mild (eGFR > 60 mL/min), moderate (eGFR 30-60 mL/min), or severe (eGFR < 30 mL/min). RESULTS: Mortality increased more steeply across CKD stages (2.0%-12.9%) than across cTn ratio categories (2.7%-5.4%). In normal or mild CKD, mortality was low regardless of cTn elevations. In moderate CKD, mortality increased incrementally with cTnI (3.3% versus 5.4% versus 7.4%) and cTnT (3.7% versus 5.3% versus 7.3%) elevation. Among severe CKD patients, only major cTn elevations further distinguished risk (cTnI: 10.1% versus 9.7% versus 14.6%; cTnT: 7.0% versus 5.7% versus 14.0%). CONCLUSIONS: In patients with CKD, cTnI and cTnT perform equally in differentiating short-term prognosis following NSTE ACS; however, the prognostic impact of cTn is dependent upon the degree of CKD severity.  相似文献   
84.
Cardiac muscle models. An overextension of series elasticity?   总被引:1,自引:0,他引:1  
  相似文献   
85.
Salmonellosis Pacifarin Activity of Enterobactin   总被引:2,自引:0,他引:2       下载免费PDF全文
Salmonellosis pacifarin activity is detected by an increased survivorship of mice, doubly infected with avirulent and virulent Salmonella typhimurium, when heretofore unknown agents, found in certain natural foodstuffs and in the supernatants of certain bacterial cultures, are fed to the infected animals as dietary supplements. We now announce the identity of one of these agents: it is enterobactin, a cyclic trimer of 2,3-dihydroxy-N-benzoyl-L-serine. Basal diets enriched with as little as 2 mg of crystalline trimer per kg of diet show pacifarin activity to a statistically significant degree. Diets supplemented with as much as 100 mg of the monomer per kg of diet show no such activity.  相似文献   
86.
In four healthy volunteers, we analyzed in detail the immediate in vivo effects on circulating neutrophils of subcutaneous administration of 300 micrograms of granulocyte colony-stimulating factor (G-CSF). Neutrophil activation was assessed by measurement of degranulation. Mobilization of secretory vesicles was shown by a decrease in leukocyte alkaline phosphatase content of the circulating neutrophils. Furthermore, shortly postinjection, Fc gamma RIII was found to be upregulated from an intracellular pool that we identified by immunoelectron microscopy as secretory vesicles. Intravascular release of specific granules was shown by increased plasma levels of lactoferrin and by upregulation of the expression of CD66b and CD11b on circulating neutrophils. Moreover, measurement of fourfold elevated plasma levels of elastase, bound to its physiologic inhibitor alpha 1- antitrypsin, indicated mobilization of azurophil granules. However, no expression of CD63, a marker of azurophil granules, was observed on circulating neutrophils. G-CSF--induced mobilization of secretory vesicles and specific granules could be mimicked in whole blood cultures in vitro, in contrast to release of azurophil granules. Therefore, we postulate that the most activated neutrophils leave the circulation, as observed shortly postinjection, and undergo subsequent stimulation in the endothelial microenvironment, resulting in mobilization of azurophil granules. Our data demonstrate that G-CSF should be regarded as a potent immediate activator of neutrophils in vivo.  相似文献   
87.
The short-term (1 month) and long-term (6 months) safety of combination lidoflazine-propranolol therapy was investigated in an open trial of 15 patients with stable angina of effort. The possible advantages of adding lidoflazine (titrated to 360 mg daily) to patients having a therapeutic response to propranolol (80-400 mg daily) was also evaluated. Effects on non-invasive indexes of left ventricular function (echocardiography, systolic time intervals, radionuclide ventriculography) and exercise tolerance (treadmill exercise testing) were determined. There was no change in mean resting heart rate with the combination therapy, although one patient developed sinus bradycardia at a rate of 44 and had to have his propranolol dose reduced. Electrocardiographic analysis showed significant prolongation of the QTc intervals on lidoflazine-propranolol therapy compared to propranolol alone, with 3 patients having QTc interval prolongation to above .53 seconds, but there was no evidence of increased arrhythmogenesis with the combination therapy compared to propranolol alone. Left ventricular end-diastolic volume index tended to rise with combination therapy. However, lidoflazine-propranolol therapy did not produce any significant effects on resting ejection fraction determined by M-mode echocardiography or by radionuclide ventriculography. Radionuclide ventriculography determined peak exercise ejection fractions were also not significantly changed with combination therapy compared to propranolol alone. There were only small, insignificant improvements in exercise tolerance with the lidoflazine-propranolol combination treatment compared to propranolol alone. It is concluded that lidoflazine-propranolol combination therapy is generally safe but has the potential of causing serious adverse effects in certain patients, i.e. those with sick sinus disease, prolonged QTc intervals, and severe baseline left ventricular dysfunction, and that caution must be exercised in its use. Furthermore, it would appear that combination therapy provides only slight, if any, improvements in exercise tolerance in patients with chronic stable angina having a therapeutic response to oral propranolol.  相似文献   
88.

Background

Supratentorial PNETs (sPNET) are uncommon embryonal malignancies of the central nervous system whose prognosis has historically been poor. We evaluated the outcome and prognostic factors of children with sPNET treated prospectively on a Children's Oncology Group trial.

Procedure

Following surgery, patients received craniospinal radiotherapy with concurrent carboplatin followed by six months of maintenance chemotherapy with cyclophosphamide and vincristine.

Results

Five‐year overall survival (OS) and progression‐free survival (PFS) for all patients was 58 ± 7% and 48 ± 7%. For patients with pineoblastoma (n = 23), five‐year OS and PFS was 81 ± 9% and 62 ± 11%. Extent of resection but not M‐stage was prognostic. Five‐year OS and PFS for 37 patients with non‐pineal tumors (NPsPNET) was 44 ± 8% and 39 ± 8%, significantly worse than for PB (P = 0.055 and 0.009 respectively). Extent of resection and major radiotherapy deviations were prognostic. Five year OS was 59 +/? 11.4% for those undergoing complete resection versus 10.4 +/? 7% for those who did not (P = 0.017). Central pathologic review called 14 (38%) “classic” sPNET, 8 (22%) “undifferentiated” and 13 (35%) “malignant gliomas.” There was no significant difference between the subgroups, although survival distributions approached significance when the combined “classic” and “undifferentiated” group was compared to the “malignant gliomas.”

Conclusions

Carboplatin during RT followed by 6 months of non‐intensive chemotherapy is a feasible treatment strategy for patients with sPNET. Aggressive surgical resection should be attempted if feasible. The classification of supratentorial small cell malignancies can be difficult. Pediatr Blood Cancer 2015;62:776–783. © 2015 Wiley Periodicals, Inc.
  相似文献   
89.

Aim

Review the literature from 1990 to 2013 to determine known anatomic sites, risk factors, treatments, and outcomes of head and neck squamous cell carcinoma (HNSCC) in sub-Saharan Africa.

Methods

Using a systematic search strategy, literature pertaining to HNSCC in sub-Saharan Africa was reviewed and patient demographics, anatomic sites, histology, stage, treatment, and outcomes were abstracted. The contributions of human immunodeficiency virus (HIV), human papillomavirus (HPV) and behavioural risk factors to HNSCC in the region were assessed.

Results

Of the 342 papers identified, 46 were utilized for review, including 8611 patients. In sub-Saharan Africa, the oropharyngeal/oral cavity was found to be the most common site, with 7750 cases (90% of all cases). Few papers distinguished oropharyngeal from oral cavity, making identification of possible HPV-associated oropharyngeal squamous cell carcinoma (SCC) difficult. SCC of the nasopharynx, nasal cavity, or paranasal sinuses was identified in 410 patients (4.8% of all cases). Laryngeal SCC was found in 385 patients (4.5% of all cases), and only 66 patients (0.8% of all cases) with hypopharyngeal SCC were identified. In 862 patients with data available, 43% used tobacco and 42% used alcohol, and reported use varied widely and was more common in laryngeal SCC than that of the oropharyngeal/oral cavity. Toombak and kola nut use was reported to be higher in patients with HNSCC. Several papers reported HIV-positive patients with HNSCC, but it was not possible to determine HNSCC prevalence in HIV-positive compared to negative patients. Reports of treatment and outcomes were rare.

Conclusions

The oropharyngeal/oral cavity was by far the most commonly reported site of HNSCC reported in sub-Saharan Africa. The roles of risk factors in HNSCC incidence in sub-Saharan Africa were difficult to delineate from the available studies, but a majority of patients did not use tobacco and alcohol.  相似文献   
90.
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