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   3172303篇
  免费   297580篇
  国内免费   40351篇
耳鼻咽喉   41663篇
儿科学   91196篇
妇产科学   74559篇
基础医学   506600篇
口腔科学   82967篇
临床医学   302181篇
内科学   537145篇
皮肤病学   86495篇
神经病学   264781篇
特种医学   122279篇
外国民族医学   333篇
外科学   479179篇
综合类   157145篇
现状与发展   108篇
一般理论   2095篇
预防医学   255092篇
眼科学   74727篇
药学   234211篇
  453篇
中国医学   34241篇
肿瘤学   162784篇
  2022年   36296篇
  2021年   71743篇
  2020年   50575篇
  2019年   73018篇
  2018年   83996篇
  2017年   67951篇
  2016年   72461篇
  2015年   92864篇
  2014年   130562篇
  2013年   193594篇
  2012年   102161篇
  2011年   101622篇
  2010年   134089篇
  2009年   134901篇
  2008年   78324篇
  2007年   77512篇
  2006年   88181篇
  2005年   82720篇
  2004年   78244篇
  2003年   69043篇
  2002年   57273篇
  2001年   86742篇
  2000年   78431篇
  1999年   83068篇
  1998年   66638篇
  1997年   64768篇
  1996年   61200篇
  1995年   56559篇
  1994年   50187篇
  1993年   46402篇
  1992年   51715篇
  1991年   47999篇
  1990年   44535篇
  1989年   44811篇
  1988年   41256篇
  1987年   39953篇
  1986年   37544篇
  1985年   38107篇
  1984年   37399篇
  1983年   35024篇
  1982年   37712篇
  1981年   35824篇
  1980年   33781篇
  1979年   28267篇
  1978年   27484篇
  1977年   26231篇
  1976年   23308篇
  1975年   21306篇
  1974年   20262篇
  1973年   19306篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.

Background

Rosacea is a chronic inflammatory skin condition whose etiology has been linked to mast cells and the antimicrobial peptide cathelicidin LL-37. Individuals with refractory disease have demonstrated clinical benefit with periodic injections of onabotulinum toxin, but the mechanism of action is unknown.

Objectives

To investigate the molecular mechanism by which botulinum toxin improves rosacea lesions.

Methods

Primary human and murine mast cells were pretreated with onabotulinum toxin A or B or control. Mast cell degranulation was evaluated by β-hexosaminidase activity. Expression of botulinum toxin receptor Sv2 was measured by qPCR. The presence of SNAP-25 and VAMP2 was established by immunofluorescence. In vivo rosacea model was established by intradermally injecting LL-37 with or without onabotulinum toxin A pretreatment. Mast cell degranulation was assessed in vivo by histologic counts. Rosacea biomarkers were analyzed by qPCR of mouse skin sections.

Results

Onabotulinum toxin A and B inhibited compound 48/80-induced degranulation of both human and murine mast cells. Expression of Sv2 was established in mouse mast cells. Onabotulinum toxin A and B increased cleaved SNAP-25 and decreased VAMP2 staining in mast cells respectively. In mice, injection of onabotulinum toxin A significantly reduced LL-37-induced skin erythema, mast cell degranulation, and mRNA expression of rosacea biomarkers.

Conclusions

These findings suggest that onabotulinum toxin reduces rosacea-associated skin inflammation by directly inhibiting mast cell degranulation. Periodic applications of onabotulinum toxin may be an effective therapy for refractory rosacea and deserves further study.  相似文献   
922.
923.
924.
Phang  P. Terry 《Abdominal imaging》2019,44(11):3740-3742
Abdominal Radiology -  相似文献   
925.
926.
Patients with active cancer are at an increased risk of arterial and venous thromboembolism (VTE) and bleeding events. Historically, in patients with cancer, low molecular weight heparins have been preferred for treatment of VTE, whereas warfarin has been the standard anticoagulant for stroke prevention in patients with atrial fibrillation (AF). More recently, direct oral anticoagulants (DOACs) have been demonstrated to reduce the risk of venous and arterial thromboembolism in large randomized clinical trials of patients with VTE and AF, respectively, thus providing an attractive oral dosing option that does not require routine laboratory monitoring. In this review, we summarize available clinical trial data and guideline recommendations, and outline a practical approach to anticoagulation management of VTE and AF in cancer.  相似文献   
927.
928.
Purpose: To study, with computational models, the utility of power modulation to reduce tissue temperature heterogeneity for variable nanoparticle distributions in magnetic nanoparticle hyperthermia.

Methods: Tumour and surrounding tissue were modeled by elliptical two- and three-dimensional computational phantoms having six different nanoparticle distributions. Nanoparticles were modeled as point heat sources having amplitude-dependent loss power. The total number of nanoparticles was fixed, and their spatial distribution and heat output were varied. Heat transfer was computed by solving the Pennes’ bioheat equation using finite element methods (FEM) with temperature-dependent blood perfusion. Local temperature was regulated using a proportional-integral-derivative (PID) controller. Tissue temperature, thermal dose and tissue damage were calculated. The required minimum thermal dose delivered to the tumor was kept constant, and heating power was adjusted for comparison of both the heating methods.

Results: Modulated power heating produced lower and more homogeneous temperature distributions than did constant power heating for all studied nanoparticle distributions. For a concentrated nanoparticle distribution, located off-center within the tumor, the maximum temperatures inside the tumor were 16% lower for modulated power heating when compared to constant power heating. This resulted in less damage to surrounding normal tissue. Modulated power heating reached target thermal doses up to nine-fold more rapidly when compared to constant power heating.

Conclusions: Controlling the temperature at the tumor-healthy tissue boundary by modulating the heating power of magnetic nanoparticles demonstrably compensates for a variable nanoparticle distribution to deliver effective treatment.  相似文献   

929.
Using data on waterfowl band recoveries, we identified spatially explicit hotspots of concentrated waterfowl movement to predict occurrence and spatial spread of a novel influenza A virus (clade 2.3.4.4) introduced from Asia by waterfowl from an initial outbreak in North America in November 2014. In response to the outbreak, the hotspots of waterfowl movement were used to help guide sampling for clade 2.3.4.4 viruses in waterfowl as an early warning for the US poultry industry during the outbreak . After surveillance sampling of waterfowl, we tested whether there was greater detection of clade 2.3.4.4 viruses inside hotspots. We found that hotspots defined using kernel density estimates of waterfowl band recoveries worked well in predicting areas with higher prevalence of the viruses in waterfowl. This approach exemplifies the value of ecological knowledge in predicting risk to agricultural security.  相似文献   
930.
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