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   8093篇
  免费   330篇
  国内免费   50篇
耳鼻咽喉   82篇
儿科学   1186篇
妇产科学   79篇
基础医学   982篇
口腔科学   34篇
临床医学   723篇
内科学   1559篇
皮肤病学   76篇
神经病学   510篇
特种医学   277篇
外科学   1005篇
综合类   110篇
预防医学   658篇
眼科学   96篇
药学   429篇
中国医学   30篇
肿瘤学   637篇
  2023年   44篇
  2022年   57篇
  2021年   130篇
  2020年   93篇
  2019年   198篇
  2018年   326篇
  2017年   281篇
  2016年   279篇
  2015年   162篇
  2014年   224篇
  2013年   265篇
  2012年   560篇
  2011年   2214篇
  2010年   888篇
  2009年   463篇
  2008年   359篇
  2007年   290篇
  2006年   242篇
  2005年   222篇
  2004年   194篇
  2003年   185篇
  2002年   167篇
  2001年   22篇
  2000年   13篇
  1999年   36篇
  1998年   60篇
  1997年   40篇
  1996年   61篇
  1995年   56篇
  1994年   52篇
  1993年   35篇
  1992年   18篇
  1991年   12篇
  1990年   13篇
  1989年   7篇
  1988年   6篇
  1986年   8篇
  1985年   9篇
  1984年   6篇
  1983年   9篇
  1982年   6篇
  1981年   7篇
  1980年   9篇
  1975年   13篇
  1973年   8篇
  1964年   12篇
  1962年   5篇
  1961年   12篇
  1960年   5篇
  1959年   7篇
排序方式: 共有8473条查询结果,搜索用时 15 毫秒
81.
Respiratory mortality and morbidity has been associated with exposure to particulate matter (PM). Experimental evidence suggests involvement of cytotoxicity, oxidative stress, and inflammation in the development of PM‐associated pathological states; however, the exact mechanisms remain unclear. In the current study, we analyzed short‐term epigenetic response to PM10 (particles with aerodynamic diameter less than 10 μm) exposure in mouse ascitic RAW264.7 macrophages (BALB/C Abelson murine leukemia virus‐induced tumor). Ambient PM10 was collected using a high volume sampler in Little Rock, AR. Analysis revealed that PM10 was composed mainly of Al and Fe, and the water soluble organic fraction was dominated by aliphatic and carbohydrate fragments and minor quantities of aromatic components. Exposure to PM10 compromised the cellular epigenome at concentrations 10–200 µg/ml. Specifically, epigenetic alterations were evident as changes in the methylation and expression of repetitive element‐associated DNA and associated DNA methylation machinery. These results suggest that epigenetic alterations, in concert with cytotoxicity, oxidative stress, and inflammation, might contribute to the pathogenesis of PM‐associated respiratory diseases. Environ. Mol. Mutagen. 55:428–435, 2014. © 2014 Wiley Periodicals, Inc.  相似文献   
82.

Introduction

The impact of the dose and fractionation of thoracic radiotherapy on the risk of developing brain metastasis (BM) has not been evaluated prospectively in limited stage SCLC patients receiving prophylactic cerebral irradiation (PCI).

Methods

Data from patients treated with PCI from the CONVERT trial were analyzed.

Results

Four hundred forty-nine of 547 patients (82%) received PCI after completion of chemoradiotherapy. Baseline brain imaging consisted of computed tomographic scans in 356 of 449 patients (79%) and magnetic resonance imaging in 83 of 449 (18%) patients. PCI was delivered to 220 of 273 participants (81%) in the twice-daily (BD) group and 229 of 270 in the once-daily (OD) group (85%; p = 0.49). Total median PCI dose was 25 Gy in both the BD and OD groups (p = 0.74). In patients who received PCI, 75 (17%) developed BM (35 [8%] in OD and 40 [9%] in BD) and 173 (39%) other extracranial progression. In the univariate analysis, gross tumor volume (GTV) was associated with an increased risk of BM (p = 0.007) or other radiological progression events (p = 0.006), whereas in a multivariate analysis both thoracic GTV (tGTV) and ECOG performance score were associated with either progression type. The median overall survival (OS) of patients treated with PCI was 29 months. In the univariate analysis of OS, PCI timing from end of chemotherapy, weight loss of more than 10%, and tGTV were prognostic factors associated with OS. In the multivariate analysis, only tGTV was associated with OS. Delay between end of chemotherapy and PCI was not associated with OS.

Conclusions

Patients receiving OD or BD thoracic radiotherapy have the same risk of developing BM. Larger tumors are associated with a higher risk of BM.  相似文献   
83.
84.
??Airway mucus hypersecretion is an important feature of chronic respiratory diseases. Viral infection is a common factor inducing airway mucus hypersecretion. Understanding the relationship between the viral infection and airway mucus hypersecretion and mechanism is very important to preventing and reducing airway mucus hypersecretion??decreasing the mortality of chronic respiratory diseases. The increase of MUC5AC expression is the major pathological basis of airway mucus hypersecretion??so it is necessary to discuss the signal transduction pathway of MUC5AC secretion caused by common respiratory virus infection.  相似文献   
85.
This study aimed to examine the associations of lifetime traumatic experience with presurgery and postsurgery eating pathology and postoperative weight loss in a sample of adult bariatric surgery patients using electronic medical record (EMR) data. Presurgery lifetime exposure to traumatic event, presurgery and postsurgery dysfunctional eating patterns, and post‐operative total and excess weight losses were extracted from electronic medical records of 200 adult bariatric surgery patients in 2013 and 2014. Logistic regression analyses were conducted. During their lifetime, 60.5% of the patients (81.5% women, age = 44.4 ± 11.5 years; BMIpre = 44.9 ± 5.5 kg/m2) reported that they were exposed to a traumatic event. Before surgery, trauma exposure was associated with impulsive, compulsive, or restrictive eating patterns (OR = 2.40), overeating or disturbed eating (OR = 1.55), and grazing or night eating behaviours (OR = 1.72). After surgery, trauma exposure was associated with lower total weight loss at 6 (OR = 2.06) and 24 months (OR = 2.06), and to overeating or disturbed eating (OR = 1.53) 12 months after surgery. Bariatric surgery candidates with a history of trauma exposure could benefit from closer medical, dietetic, and/or psychological follow‐up care to avoid insufficient postoperative weight loss as well as reappearance of dysfunctional eating patterns after surgery.  相似文献   
86.
??Objective To compare pbp2b??ply and lytA genes PCR with cerebral spinal fluid culture in diagnosis of Streptococcus pneumoniae meningitis and prediction of its susceptibility. Methods A nested PCR targeting pbp2b and another two S.pneumoniae specific PCR targeting the genes of pneumolysin??ply?? and autolysin??lytA?? were developed for detection of S.pneumoniae in cerebral spinal fluid from bacterial meningitis patients. The three PCR results and culture were compared. The consistency of penicillin susceptibility PCR ??using resistant and susceptible primers respectively????sequencing and culture-based phenotypic penicillin resistant results were compared. Results Of the 161 specimens studied??there were 25 cases of S.pneumoniae infection confirmed by different methods??16 by pbp2b PCR??16 by lytA PCR??14 by ply PCR and 9 by cerebrospinal fluid culture??. Of the 16 pbp2b positive specimens??penicillin sensitive and resistant sequence types accounted for half??respectively. Four of the 16 pbp2b positive specimens had culture-based phenotypic penicillin-resistant result. Three of 4 were consistent with penicillin susceptibility PCR result. The results of susceptibility PCR targeting pbp2b was consistent with sequencing result. New sequence types were found but there were no new point mutations in these strains when compared with GenBank ??http??//blast.ncbi.nlm.nih.gov/Blast.cgi??. Penicillin resistance in pneumococcal meningitis was 66.67%??6/9?? by culture phenotype and 50%??8/16?? by PCR and sequencing when culture was negative. Conclusion Pbp2b can serve as a good target gene to detect S.pneumoniae and predict its penicillin susceptibility??which is especially important when culture is negative.  相似文献   
87.
88.
89.
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