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   171287篇
  免费   9752篇
  国内免费   429篇
耳鼻咽喉   2232篇
儿科学   5532篇
妇产科学   3592篇
基础医学   23212篇
口腔科学   7567篇
临床医学   12535篇
内科学   38343篇
皮肤病学   4337篇
神经病学   14327篇
特种医学   5291篇
外国民族医学   26篇
外科学   21041篇
综合类   1392篇
现状与发展   1篇
一般理论   61篇
预防医学   17891篇
眼科学   3176篇
药学   10456篇
中国医学   693篇
肿瘤学   9763篇
  2023年   885篇
  2022年   1947篇
  2021年   3625篇
  2020年   2434篇
  2019年   3442篇
  2018年   4837篇
  2017年   3629篇
  2016年   3375篇
  2015年   3946篇
  2014年   5418篇
  2013年   6861篇
  2012年   10678篇
  2011年   11171篇
  2010年   5642篇
  2009年   5076篇
  2008年   8640篇
  2007年   9266篇
  2006年   8563篇
  2005年   8856篇
  2004年   8339篇
  2003年   7628篇
  2002年   5676篇
  2001年   4975篇
  2000年   4979篇
  1999年   4363篇
  1998年   1543篇
  1997年   1283篇
  1996年   1271篇
  1995年   1078篇
  1994年   1073篇
  1993年   978篇
  1992年   2667篇
  1991年   2572篇
  1990年   2353篇
  1989年   2342篇
  1988年   2118篇
  1987年   1960篇
  1986年   1838篇
  1985年   1766篇
  1984年   1265篇
  1983年   1017篇
  1982年   572篇
  1981年   516篇
  1980年   497篇
  1979年   930篇
  1978年   614篇
  1977年   485篇
  1975年   548篇
  1974年   550篇
  1973年   545篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Objective: Polyunsaturated fatty acids n-3 (PUFA n-3) have shown effects in reducing tumor growth, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) abundantly present in fish oil (FO). When these fatty acids are provided in the diet, they alter the functions of the cells, particularly in tumor and immune cells. However, the effects of α-linolenic fatty acid (ALA), which is the precursor of EPA and DHA, are controversial. Thus, our objective was to test the effect of this parental fatty acid. Methods: Non-tumor-bearing and tumor-bearing Wistar rats (70 days) were supplemented with 1 g/kg body weight of FO or Oro Inca® (OI) oil (rich in ALA). Immune cells function, proliferation, cytokine production, and subpopulation profile were evaluated. Results: We have shown that innate immune cells enhanced phagocytosis capacity, and increased processing and elimination of antigens. Moreover, there was a decrease in production of pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6)) by macrophages. Lymphocytes showed decreased proliferation capacity, increased cluster of differentiation 8 (CD8+) subpopulation, and increased TNF-α production. Conclusions: Oil rich in ALA caused similar immune modulation in cancer when compared with FO.  相似文献   
5.
6.
7.
8.
9.
Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital condition. It responds well to early diagnosis and treatment, but otherwise the prognosis is poor. We present our case series of 12 patients (mean age, 2 ± 2.58 yr; age range, 2 mo–8 yr), emphasizing the diagnostic process and discussing our surgical results. The diagnosis of ALCAPA should be suspected in infants who have dilated cardiomyopathy with electrocardiographic changes that suggest ischemia, and in older children who have isolated mitral regurgitation. When clinical suspicion is high, the results of 2-dimensional echocardiography combined with color-flow Doppler studies in expert hands can establish the diagnosis, thus avoiding angiography in critically ill infants. The treatment of choice in our patients was transfer and reimplantation of the left coronary artery onto the ascending aorta. There were 2 deaths: both were infants in extremis who underwent emergency surgery. An older child with severe ventricular dysfunction was given mechanical ventricular assistance and then heart transplantation. As of this report, all 10 survivors remained well and asymptomatic.  相似文献   
10.
Melatonin, the main hormone produced by the pineal gland, is secreted in a circadian manner (24‐hr period), and its oscillation influences several circadian biological rhythms, such as the regulation of clock genes expression (chronobiotic effect) and the modulation of several endocrine functions in peripheral tissues. Assuming that the circadian synchronization of clock genes can play a role in the regulation of energy metabolism and it is influenced by melatonin, our study was designed to assess possible alterations as a consequence of melatonin absence on the circadian expression of clock genes in the epididymal adipose tissue of male Wistar rats and the possible metabolic repercussions to this tissue. Our data show that pinealectomy indeed has impacts on molecular events: it abolishes the daily pattern of the expression of Clock, Per2, and Cry1 clock genes and Pparγ expression, significantly increases the amplitude of daily expression of Rev‐erbα, and affects the pattern of and impairs adipokine production, leading to a decrease in leptin levels. However, regarding some metabolic aspects of adipocyte functions, such as its ability to synthesize triacylglycerols from glucose along 24 hr, was not compromised by pinealectomy, although the daily profile of the lipogenic enzymes expression (ATP‐citrate lyase, malic enzyme, fatty acid synthase, and glucose‐6‐phosphate dehydrogenase) was abolished in pinealectomized animals.  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