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   1677825篇
  免费   125934篇
  国内免费   2983篇
耳鼻咽喉   24426篇
儿科学   46072篇
妇产科学   45292篇
基础医学   240600篇
口腔科学   50893篇
临床医学   146395篇
内科学   323039篇
皮肤病学   34265篇
神经病学   132264篇
特种医学   66628篇
外国民族医学   246篇
外科学   268464篇
综合类   39795篇
现状与发展   3篇
一般理论   477篇
预防医学   121659篇
眼科学   39502篇
药学   128492篇
  3篇
中国医学   3446篇
肿瘤学   94781篇
  2018年   15232篇
  2016年   13277篇
  2015年   15386篇
  2014年   21523篇
  2013年   32134篇
  2012年   43747篇
  2011年   45756篇
  2010年   26944篇
  2009年   25553篇
  2008年   44035篇
  2007年   47040篇
  2006年   47685篇
  2005年   46238篇
  2004年   45113篇
  2003年   43460篇
  2002年   42258篇
  2001年   82923篇
  2000年   85400篇
  1999年   71659篇
  1998年   18699篇
  1997年   16765篇
  1996年   16769篇
  1995年   15759篇
  1994年   14801篇
  1993年   13744篇
  1992年   57360篇
  1991年   55458篇
  1990年   54092篇
  1989年   52659篇
  1988年   48675篇
  1987年   47611篇
  1986年   44721篇
  1985年   43120篇
  1984年   32022篇
  1983年   27296篇
  1982年   15675篇
  1981年   14067篇
  1979年   30571篇
  1978年   21285篇
  1977年   18118篇
  1976年   16190篇
  1975年   17739篇
  1974年   21834篇
  1973年   20793篇
  1972年   19752篇
  1971年   18542篇
  1970年   17678篇
  1969年   17034篇
  1968年   15332篇
  1967年   14049篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
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   
32.
33.
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system.  相似文献   
34.
We present a patient with both dynamic left ventricular outflow tract obstruction and valvular aortic stenosis. The aortic valve was calcified, and velocities and gradients measured by continuous‐wave Doppler met standard criteria for severe aortic stenosis. The increased subvalvular velocities invalidated assumptions of the simplified Bernoulli equation; correction using the longer form of the Bernoulli equation suggested a lower but still significant gradient. The complex shape of the subvalvular spectral Doppler envelope indicated supranormal systolic function and dynamic left ventricular outflow obstruction. Left heart catheterization with an end‐hole catheter was required to determine the subvalvular and valvular components of the obstruction.  相似文献   
35.
Abstract

Objective: To understand the origin of extremely high gonadotropin levels in a perimenopausal woman.

Methods: A 52-year-old woman with a 2?months of amenorrhea followed spontaneous menstrual cycles recovery was referred to our outpatient clinic with elevated follicle-stimulating hormone (FSH, 483 mUI/ml), luteinizing hormone (LH, 475 mUI/ml) and prolactin (PRL, 173?ng/ml). She was known to take levosulpiride. The gonadotropin levels did not fit with the clinical features.

Results: A gonadotroph tumor was ruled out. Further analysis confirmed constantly high FSH, LH and PRL levels. The measurements were repeated using different analytical platforms with different results. After serial dilutions, nonlinearity was present suggesting an immunoassay interference. After post-polyethylene glycol recovery, hormone levels appeared in the normal range. Anti-goat antibodies were recognized in the serum of the patient.

Conclusions: This case report shows a case of falsely abnormal high gonadotropin and PRL levels in a woman during menopause transition. In the clinical practice the evaluation of gonadotropin profile is not recommended at this age, but the abnormal levels stimulated further evaluation. An interference in the assay due to anti-goat antibodies resulted in abnormally high level of FSH and LH. A strict collaboration between clinicians and the laboratory is needed, when laboratory findings do not correspond to clinical findings.  相似文献   
36.
37.
38.
39.
40.
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