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   2691篇
  免费   160篇
  国内免费   22篇
耳鼻咽喉   12篇
儿科学   43篇
妇产科学   124篇
基础医学   255篇
口腔科学   117篇
临床医学   215篇
内科学   691篇
皮肤病学   67篇
神经病学   147篇
特种医学   87篇
外国民族医学   3篇
外科学   481篇
综合类   54篇
预防医学   113篇
眼科学   73篇
药学   258篇
中国医学   13篇
肿瘤学   120篇
  2023年   38篇
  2022年   85篇
  2021年   170篇
  2020年   84篇
  2019年   119篇
  2018年   153篇
  2017年   98篇
  2016年   86篇
  2015年   71篇
  2014年   123篇
  2013年   198篇
  2012年   211篇
  2011年   222篇
  2010年   114篇
  2009年   104篇
  2008年   139篇
  2007年   147篇
  2006年   114篇
  2005年   137篇
  2004年   105篇
  2003年   82篇
  2002年   75篇
  2001年   15篇
  2000年   16篇
  1998年   11篇
  1997年   7篇
  1996年   11篇
  1995年   8篇
  1994年   4篇
  1993年   6篇
  1992年   7篇
  1991年   4篇
  1990年   10篇
  1989年   9篇
  1988年   4篇
  1987年   5篇
  1986年   7篇
  1985年   4篇
  1983年   4篇
  1982年   4篇
  1981年   4篇
  1977年   3篇
  1974年   5篇
  1973年   4篇
  1972年   3篇
  1971年   4篇
  1970年   3篇
  1969年   5篇
  1968年   6篇
  1966年   3篇
排序方式: 共有2873条查询结果,搜索用时 46 毫秒
71.
72.
The majority of follicular lymphoma and Burkitt's lymphoma are associated with reciprocal translocations involving BCL2 and cMYC, respectively. Unusual reports of aggressive lymphoma presenting with both translocations have been described as well as rare cases with a third structural alteration usually involving BCL6. The patient described here presented with aggressive high-grade lymphocytic leukemia, FAB subtype L2 (ALL-L2), and three reciprocal translocations, t(14;18)(q32;q21), t(8;14)(q24.1;q32), and t(1;2) (q22-23;p13). Despite immature morphology the leukemic blasts had a mature B-cell phenotype; they were positive for surface immunoglobulin heavy chains and negative for CD34, TdT, and CD10. Most reported dual t(14;18)/t(8;14) cases have not shown sIg and were positive for CD10. Molecular genetic analyses showed the typical rearrangements of BCL2 and cMYC as well as the FCGR2B gene on chromosome 1q23. The occurrence of a third oncogene rearrangement in association with the dual BCL2, cMYC translocations in ALL patients is very rare. To our knowledge, this is the first case where the third hit involves the FCGR2B locus. This report reiterates the poor prognosis associated with activation of cMYC together with elevated Bcl-2 expression. These data also support recent evidence that dysregulation of FCGR2B may play a role in tumor progression.  相似文献   
73.
In this article, myocardial perfusion in patients with a totally occluded left anterior descending artery reinjected by a normal right coronary artery is assessed using stress single photon emission computed tomography (SPECT). In all, 20 patients, with a totally occluded left anterior descending artery reinjected by normal right coronary artery, underwent myocardial single photon emission computed tomography imaging within 60 days of angiography. All patients had abnormal perfusion single photon emission computed tomography results and 70% had reversible defects. Perfusion defects at rest were present in 75% of patients, with perinecrotic residual ischemia in 45% of patients whereas for 30% of patients, no viable myocardium was detected in the collateral-dependent segments. In all, 25% of patients had no resting perfusion defects but all are presented with stress-induced ischemia. Collaterals are not protective against stress-induced ischemia, but they can preserve myocardial viability. This conclusion is highly supported by the presence of residual ischemia in the collateral-dependent segments.  相似文献   
74.
Background : The aim of the present systematic review is to compare the crestal bone loss (CBL) around dental implants placed in healed sites using flapped and flapless surgical techniques. Methods: The focused question was, “Does flapped and flapless surgical technique influence CBL around dental implants placed in healed sites?” Databases were searched from 1975 up to and including May 2014 using different combinations of the following keywords: “crestal bone loss”; “dental implant”; “surgery”; “flap”; and “flapless.” Unpublished data, experimental studies, letters to the editor, review articles, case reports, commentaries, and articles published in languages other than English were excluded. In all studies, the test group comprised implants placed using flapless surgery, and the control group, implants placed after reflection of a full‐thickness mucoperiosteal flap. Results: Ten clinical studies were included. In five studies, CBL around implants was comparable between the test and control groups. In four studies, implants in the test group showed significantly less CBL compared with the control group. In one study, CBL was significantly higher in the test group than the control group. Conclusion: CBL around dental implants placed in healed sites using flapped and flapless techniques is comparable.  相似文献   
75.
76.
Alzheimer’s disease (AD) is a neurodegenerative disorder with progressive degeneration of the hippocampal and cortical neurons. This study was designed to demonstrate the protective effect of caffeine on gene expression of brain derived neurotrophic factor (BDNF) and its receptor neural receptor protein-tyrosine kinase-β (TrkB) as well as glial fibrillary acidic protein (GFAP) and Ki-67 immunoreactivity in Aluminum chloride (AlCl3) induced animal model of AD. Fifty adult rats included in this study were classified into 5 group (10 rats each); negative and positive control groups (I&II), AD model group (III), group treated with caffeine from the start of AD induction (IV) and group treated with caffeine two weeks before AD induction (V). Hippocampal tissue BDNF and its receptor (TrkB) gene expression by real time RT-PCR in addition to immunohistochemical study of GFAP and Ki67 immunoreactivity were performed for all rats in the study. The results of this study revealed that caffeine has protective effect through improving the histological and immunohistochemical findings induced by AlCl3 as well as BDNF and its receptor gene expression. It could be concluded from the current study, that chronic caffeine consumption in a dose of 1.5 mg/kg body weight daily has a potentially good protective effect against AD.  相似文献   
77.
Objectives:To elucidate the risk factors for hospital admission among COVID-19 patients with type 2 diabetes mellitus (T2DM).Methods:This retrospective study was conducted at the Prince Sultan Military Medical City, Riyadh, Saudi Arabia between May 2020 and July 2020. Out of 7,260 COVID-19 patients, 920 were identified as T2DM. After the exclusion process, 806 patients with T2DM were included in this analysis. Patients’ data were extracted from electronic medical records. A logistic regression model was performed to estimate the risk factors of hospital admission.Results:Of the total of 806 COVID-19 patients with T2DM, 48% were admitted in the hospital, 52% were placed under home isolation. Older age between 70-79 years (OR [odd ratio] 2.56; p=0.017), ≥80 years (OR 6.48; p=0.001) were significantly more likely to be hospitalized compared to <40 years. Similarly, patients with higher HbA1c level of ≥9% compared to <7%; (OR 1.58; p=0.047); patients with comorbidities such as, hypertension (OR 1.43; p=0.048), cardiovascular disease (OR 1.56; p=0.033), cerebrovascular disease (OR 2.38; p=0.016), chronic pulmonary disease (OR 1.51; p=0.018), malignancy (OR 2.45; p=0.025), chronic kidney disease (CKD) IIIa, IIIb, IV (OR 2.37; p=0.008), CKD V (OR 5.07; p=0.007) were significantly more likely to be hospitalized. Likewise, insulin-treated (OR 1.46; p=0.03) were more likely to require hospital admission compared to non-insulin treated patients.Conclusion:Among COVID-19 patients with diabetes, higher age, high HbA1c level, and presence of other comorbidities were found to be significant risk factors for the hospital admission.  相似文献   
78.

Objectives

The optimal strategy for the reconstruction of the pancreas following pancreaticoduodenectomy (PD) is still debated. The aim of this study was to compare the outcomes of isolated Roux loop pancreaticojejunostomy (IRPJ) with those of pancreaticogastrostomy (PG) after PD.

Methods

Consecutive patients submitted to PD were randomized to either method of reconstruction. The primary outcome measure was the rate of postoperative pancreatic fistula (POPF). Secondary outcomes included operative time, day to resumption of oral feeding, postoperative morbidity and mortality, and exocrine and endocrine pancreatic functions.

Results

Ninety patients treated by PD were included in the study. The median total operative time was significantly longer in the IRPJ group (320 min versus 300 min; P = 0.047). Postoperative pancreatic fistula developed in nine of 45 patients in the IRPJ group and 10 of 45 patients in the PG group (P = 0.796). Seven IRPJ patients and four PG patients had POPF of type B or C (P = 0.710). Time to resumption of oral feeding was shorter in the IRPJ group (P = 0.03). Steatorrhea at 1 year was reported in nine of 42 IRPJ patients and 18 of 41 PG patients (P = 0.029). Albumin levels at 1 year were 3.6 g/dl in the IRPJ group and 3.3 g/dl in the PG group (P = 0.001).

Conclusions

Isolated Roux loop PJ was not associated with a lower rate of POPF, but was associated with a decrease in the incidence of postoperative steatorrhea. The technique allowed for early oral feeding and the maintenance of oral feeding even if POPF developed.  相似文献   
79.
80.
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