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   969678篇
  免费   78720篇
  国内免费   2333篇
耳鼻咽喉   13977篇
儿科学   27930篇
妇产科学   26983篇
基础医学   138683篇
口腔科学   27384篇
临床医学   86046篇
内科学   187080篇
皮肤病学   18340篇
神经病学   80715篇
特种医学   38607篇
外国民族医学   172篇
外科学   151709篇
综合类   26075篇
现状与发展   3篇
一般理论   413篇
预防医学   76496篇
眼科学   23545篇
药学   72431篇
  1篇
中国医学   1841篇
肿瘤学   52300篇
  2018年   9855篇
  2016年   8654篇
  2015年   10138篇
  2014年   14583篇
  2013年   21789篇
  2012年   30211篇
  2011年   31889篇
  2010年   18250篇
  2009年   17168篇
  2008年   29676篇
  2007年   32101篇
  2006年   31629篇
  2005年   31285篇
  2004年   30445篇
  2003年   29123篇
  2002年   27956篇
  2001年   36868篇
  2000年   37250篇
  1999年   32000篇
  1998年   10509篇
  1997年   9631篇
  1996年   9311篇
  1995年   8847篇
  1994年   8444篇
  1992年   27251篇
  1991年   26626篇
  1990年   26073篇
  1989年   25120篇
  1988年   23670篇
  1987年   23315篇
  1986年   22097篇
  1985年   21531篇
  1984年   16876篇
  1983年   14462篇
  1982年   9480篇
  1981年   8742篇
  1980年   8153篇
  1979年   17057篇
  1978年   12425篇
  1977年   10478篇
  1976年   9583篇
  1975年   10381篇
  1974年   12885篇
  1973年   12367篇
  1972年   11710篇
  1971年   10823篇
  1970年   10340篇
  1969年   10028篇
  1968年   9010篇
  1967年   8332篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
A pathological feature in atherosclerosis is the dysfunction and death of vascular endothelial cells (EC). Oxidized low‐density lipoprotein (LDL), known to accumulate in the atherosclerotic arterial walls, impairs endothelium‐dependent relaxation and causes EC apoptosis. A major bioactive ingredient of the oxidized LDL is lysophosphatidylcholine (LPC), which at higher concentrations causes apoptosis and necrosis in various EC. There is hitherto no report on LPC‐induced cytotoxicity in brain EC. In this work, we found that LPC caused cytosolic Ca2+ overload, mitochondrial membrane potential decrease, p38 activation, caspase 3 activation and eventually apoptotic death in mouse cerebral bEND.3 EC. In contrast to reported reactive oxygen species (ROS) generation by LPC in other EC, LPC did not trigger ROS formation in bEND.3 cells. Pharmacological inhibition of p38 alleviated LPC‐inflicted cell death. We examined whether heparin could be cytoprotective: although it could not suppress LPC‐triggered Ca2+ signal, p38 activation and mitochondrial membrane potential drop, it did suppress LPC‐induced caspase 3 activation and alleviate LPC‐inflicted cytotoxicity. Our data suggest LPC apoptotic death mechanisms in bEND.3 might involve mitochondrial membrane potential decrease and p38 activation. Heparin is protective against LPC cytotoxicity and might intervene steps between mitochondrial membrane potential drop/p38 activation and caspase 3 activation.  相似文献   
73.
74.
75.
Dynamic contrast-enhanced ultrasound (DCE-US) has been proposed as a powerful tool for cancer diagnosis by estimation of perfusion and dispersion parameters reflecting angiogenic vascular changes. This work was aimed at identifying which vascular features are reflected by the estimated perfusion and dispersion parameters through comparison with acoustic angiography (AA). AA is a high-resolution technique that allows quantification of vascular morphology. Three-dimensional AA and 2-D DCE-US bolus acquisitions were used to monitor the growth of fibrosarcoma tumors in nine rats. AA-derived vascular properties were analyzed along with DCE-US perfusion and dispersion to investigate the differences between tumor and control and their evolution in time. AA-derived microvascular density and DCE-US perfusion exhibited good agreement, confirmed by their spatial distributions. No vascular feature was correlated with dispersion. Yet, dispersion provided better cancer classification than perfusion. We therefore hypothesize that dispersion characterizes vessels that are smaller than those visible with AA.  相似文献   
76.
77.
First described in 1955 in New Jersey, epizootic haemorrhagic disease (EHD) causes a severe clinical disease in wild and domestic ruminants worldwide. Epizootic haemorrhagic disease outbreaks occur in deer populations each year from summer to late autumn. The etiological agent is EHD virus (EHDV) which is a double‐stranded segmented icosahedral RNA virus. EHD virus utilizes point mutations and reassortment strategies to maintain viral fitness during infection. In 2018, EHDV serotype 2 was predominantly detected in deer in Illinois. Whole genome sequencing was conducted for two 2018 EHDV2 isolates (IL41747 and IL42218) and the sequence analyses indicated that IL42218 was a reassortant between different serotypes whereas IL41747 was a genetically stable strain. Our data suggest that multiple strains contribute to outbreaks each year.  相似文献   
78.
79.
80.
The aim of this study was to analyse the effect of body mass index (BMI), both low and high values, on the perioperative complication rate in patients with oral squamous cell carcinoma (OSCC). The medical records of 259 patients operated between 2014 and 2017 for OSCC were reviewed. Univariate and multivariate analyses were performed. Sixty of the 259 patients developed 87 complications. Low or high BMI was not associated with the perioperative complication rate. A longer operating time and increased blood loss were associated with a higher perioperative complication rate and higher Clavien–Dindo grade. Low BMI, American Society of Anesthesiologists score 2 and 3, a longer operating time, and increased blood loss were associated with a longer hospital stay. Low BMI was associated with a longer hospital stay. Neither low nor high BMI was associated with the perioperative complication rate. A longer operating time and increased blood loss were associated with a higher perioperative complication rate and higher Clavien–Dindo grade.  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