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   50322篇
  免费   2729篇
  国内免费   400篇
耳鼻咽喉   434篇
儿科学   1032篇
妇产科学   970篇
基础医学   5378篇
口腔科学   1197篇
临床医学   3801篇
内科学   13865篇
皮肤病学   806篇
神经病学   5058篇
特种医学   1732篇
外科学   8365篇
综合类   92篇
一般理论   10篇
预防医学   2087篇
眼科学   907篇
药学   2950篇
中国医学   83篇
肿瘤学   4684篇
  2024年   54篇
  2023年   418篇
  2022年   925篇
  2021年   1661篇
  2020年   963篇
  2019年   1355篇
  2018年   1585篇
  2017年   1182篇
  2016年   1399篇
  2015年   1490篇
  2014年   2088篇
  2013年   2599篇
  2012年   4017篇
  2011年   3895篇
  2010年   2242篇
  2009年   2139篇
  2008年   3410篇
  2007年   3405篇
  2006年   3162篇
  2005年   3141篇
  2004年   3015篇
  2003年   2530篇
  2002年   2369篇
  2001年   299篇
  2000年   224篇
  1999年   304篇
  1998年   434篇
  1997年   357篇
  1996年   326篇
  1995年   300篇
  1994年   242篇
  1993年   228篇
  1992年   193篇
  1991年   139篇
  1990年   142篇
  1989年   101篇
  1988年   102篇
  1987年   94篇
  1986年   94篇
  1985年   92篇
  1984年   108篇
  1983年   73篇
  1982年   94篇
  1981年   72篇
  1980年   57篇
  1979年   35篇
  1978年   27篇
  1977年   35篇
  1976年   25篇
  1974年   25篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
991.
992.
Abstract: This paper reviews the genetic variants of alpha-1-antitrypsin (AAT) which have been sequenced with special emphasis on the s.c. deficiency variants. These result in AAT low plasma levels via three main mechanisms: 1) intracellular storage; 2) intracellular degradation; 3) lack of synthesis. Intracellular storage occurs with the classical Z variant and with a few variants called M-like, because of their isoelectric focusing (IF) pattern. The storage phenomen causes liver damage and can be demonstrated at both light and electron microscopic level with the help of immuno-histochemistry. We report a new deficiency variant of AAT (M-Cagliari) characterized by very low plasma levels, massive storage of AAT and liver cirrhosis. By using immunohistochemical techniques and DNA analysis we could demonstrate that M-Cagliari has antigenic and genetic properties other than the Z AAT.  相似文献   
993.
Myocardial bridging, a systolic compression of an intramyocardial segment of an epicardial coronary artery, may be an incidental finding during coronary angiography or autopsy. However, some investigators reported a variety of acute coronary syndromes associated with this condition. We describe the case of a relatively young male patient (43 years old) referred to our emergency department for cardiac arrest and subsequent evidence of significant myocardial bridging at coronary angiography. The patient has been treated with an implantable cardioverter-defibrillator to prevent possible subsequent arrhythmic events associated with the myocardial bridging.  相似文献   
994.
BACKGROUND: Periodic evaluation of serum thyroglobulin (Tg) and whole body 131I imaging (131I-WBS) are essential in the follow-up of differentiated thyroid carcinoma (DTC); both diagnostic modalities require stimulation by high levels of TSH. Administration of recombinant human TSH (rhTSH) is an alternative to the withdrawal of thyroid hormone therapy. OBJECTIVE: The aim of this study was to report our experience in the use of rhTSH for the management of patients with DTC. PATIENTS: One hundred and four patients were enrolled in the study. A dose of 10 U of rhTSH therapy was injected intramuscularly for 2 consecutive days; 24 h after the second dose of rhTSH the patients were administered 4--5 mCi of 131I and, 48 h later, WBS was performed. RESULTS: In all patients, baseline mean serum Tg and TSH levels were 2.4 +/- 1.9 ng/ml and 0.0153 +/- 0.0232 mIU/l, respectively. Basal Tg levels were detectable in 58 out of 104 patients. After rhTSH injection, mean serum TSH levels rose to 122.67 +/- 47.36 mIU/l. Stimulated serum Tg levels increased to greater-than-or-equal 5 ng/ml and the 131I-WBS showed an uptake in 18 patients (17.4%). Among them there were three with bone metastases and one with brain metastases, who reported violent skeletal pain and a severe headache, respectively. These were caused by the growth of tumour mass of metastases induced by rhTSH administration. CONCLUSIONS: The use of rhTSH avoids the debilitating effects of hypothyroidism and its use successfully promotes iodine uptake and increases the sensitivity of serum Tg testing. The risk of causing serious side-effects recommends performing skull magnetic resonance and radionuclide bone scan in cases of suspected brain or skeletal metastases.  相似文献   
995.
We have used genomic probes which specifically recognize DNA rearrangements of the RAR-alpha locus on chromosome 17q21 in patients with acute promyelocytic leukaemia (APL) and acute myeloid leukaemia (AML) subtypes. Molecular data were examined in comparison with morphological and immunophenotypic characterization at diagnosis in 20 hypergranular FAB M3 cases, five microgranular APL (M3v), 51 non-M3 AML and 12 myeloid CML blast crises. Rearrangements of the RAR-alpha locus were only detected in 23/25 APL cases and in none of the other FAB subtypes analysed. Surface marker characterization showed a consistent immunophenotypic profile--HLADR negative, CD9 and CD13/33 positive--in all M3 and M3v cases. Neither HLADR negativity nor CD9 positivity were associated with RAR-alpha rearrangements in non M3 AML. Our data indicate that RAR-alpha gene rearrangements are relevant diagnostic features of both M3 and M3v, and may prove useful molecular marker for follow-up analysis in APL patients.  相似文献   
996.
Our aim was to evaluate incidence and riskfactors of liver involvement in obese Italian childrenas assessed by both ultrasonographic and biochemicalparameters. In seventy-five consecutive obese children (age 9.5 ± 2.9 years, males/females41/34), serum levels of enzymes and ultrasonography ofthe liver were evaluated. Tests were repeated one,three, and six months after starting a moderatehypocaloric diet and an exercise program. Three obese childrenwho were found to have chronic viral hepatitis wereexcluded from the study. Thirty-eight of 72 (53%) obesechildren had an ultrasonographic image of bright liver consistent with liver steatosis. Thelatter was severe in nine children, moderate in 16, andmild in 13. Eighteen obese children (25%) had elevatedtransaminase levels. Bright liver andhypertransaminasemia were not due to any of the most common causesof liver disease. Both were rapidly responsive to lossof weight, confirming that liver involvement wassecondary to obesity and that steatosis orsteatohepatitis rather than fibrosis were involved. Obesityduration not more than three years (odds ratio = 4.77),a higher degree of obesity (odds ratio = 2.09), andhypertransaminasemia (odds ratio = 2.15) appeared asimportant predictive factors of liver involvement atultrasonography. Incidence of liver involvement assessedby means of ultrasonography is significantly higher thanthat revealed by measurement of serum liver enzymes. A short duration of obesity emerged as apotentially new risk factor of liver involvement in thepediatric obese population and needs to be confirmed infuture studies.  相似文献   
997.
A 37-year-old splenectomized man affected by beta-thalassemia and chronic hepatitis, recently treated with pegylated interferon-alpha (Peg-IFN), was admitted because of elevated fever lasting 3 months and unresponsiveness to broad-spectrum antibiotics. Laboratory studies showed white blood cell and platelet counts within the normal range but lower than observed before Peg-IFN treatment and an elevated erythrocyte sedimentation rate. The blood transfusion rate was reported to be increased compared with the period preceding Peg-IFN treatment. A diagnosis of visceral leishmaniasis (VL) was made after Leishmania amastigotes were identified from Giemsa-stained smears of bone marrow aspirates. Cure occurred after liposomal amphotericin B was administered. Symptoms of VL may be difficult to distinguish from the manifestations of Peg-IFN intolerance. We suggest that VL must be suspected in any immunodepressed patient with an unexplained fever and a history of exposure in an endemic area.  相似文献   
998.
AIM: The effects of post-operative left ventricular mass regression (LVMR) on clinical outcome after aortic valve surgery remains to be established. This study was intended to establish the impact of patient characteristics on post-operative survival in patients referred for aortic valve replacement (AVR), with particular regard to LVMR. METHODS AND RESULTS: Two hundred and sixty consecutive cases submitted to aortic valve replacement for valvular stenosis were prospectively followed for a mean of 28+/-9 months. Baseline, characteristics and extent of LVMR were tested for association with survival by uni- and multivariable analysis. Ten deaths occurred during hospital stay and 52 during out-of-hospital follow-up. Mean left ventricular mass decreased from 190+/-43 to 158+/-70 g/m2 (P<0.001). Older age, advanced functional class, hypertension, reduced left ventricle ejection fraction, and high pre-operative left ventricular mass index were associated with reduced survival. Overall the extent of LVMR did not influence the clinical results, while only early (<6 months) LVMR was weakly associated with mid-term outcome. CONCLUSION: Survival after aortic valve surgery is mainly determined by the pre-operative functional cardiac and systemic status. The extent of LVMR does not correlate with clinical outcome, whereas aggressive treatment of hypertension may improve post-operative survival.  相似文献   
999.
HIV-hepatitis C virus (HCV) coinfection is common and affects more than one-third of all HIV infected persons worldwide. Prevalence among risk categories varies according to shared risk factors for transmission, mainly intravenous drug use (IDU) and hemophiliacs. Chronic HCV infection seems to accelerate the course of HIV disease, resulting in a worsened clinical and immunological progression. At the same time, several studies suggest that HIV disease modifies the natural history of HCV infection, leading to a faster course of progression from active hepatitis to cirrhosis, to end stage liver disease and death. HCV infection mimics opportunistic diseases because its natural history is significantly accelerated in HIV patients. Since highly active antiretroviral therapy (HAART) has slowed the progression of HIV disease and decreased the rate of HIV associated mortality, the prognosis of HIV disease has been modified, and the need to treat HCV coinfection become a significant issue. Because of the poor response rate obtained by either interferon alone or interferon thrice weekly plus ribavirin, the combination of pegylated interferon and ribavirin will probably become the standard of care, although the clinicians should be aware of the overlapping toxicity of nucleoside analogues and ribavirin. Many selected categories of patients pose particular challenges to physicians treating HCV infection: nonresponders to interferon, cirrhotic patients, and patients infected with both HCV and HBV. Liver transplantation in HIV patients is currently under evaluation, but should become the rescue therapy for HIV patients with end stage liver disease.  相似文献   
1000.
We evaluated the clinical effect of selective use of sirolimus-eluting stents (SESs) in real-world, high-risk patients. A total of 4,237 consecutive patients who underwent percutaneous coronary intervention (SES, n = 872, bare metal stents [BMSs], n = 3,365) was enrolled in a prospective regional survey. A prespecified high-risk subset of patients was selected on the basis of clinical and angiographic characteristics. A propensity score analysis was performed to compare patients who received SESs with those who received BMSs. Patients in the SES group more often had diabetes and more frequently had previous myocardial infarction or coronary revascularization, type C lesions, and multivessel procedures. Patients who presented with acute myocardial infarction were treated more often with BMSs. At 9 months, the use of SESs was associated with fewer major adverse cardiac events (death, myocardial infarction, or target lesion revascularization; hazard ratio 0.56, 95% confidence interval 0.37 to 0.85) and target lesion revascularizations (hazard ratio 0.43, 95% confidence interval 0.20 to 0.91). This decrease was more evident in a prespecified high-risk subgroup of patients (major adverse cardiac events, 8.0% SES vs 15.6% BMS, hazard ratio 0.45, 95% confidence interval 0.29 to 0.72). We conclude that selective SES use in real-world patients who have high-risk clinical and angiographic characteristics is associated with significant decreases in major adverse cardiac events and repeat revascularizations compared with BMS use.  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