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   1744篇
  免费   125篇
  国内免费   2篇
耳鼻咽喉   5篇
儿科学   36篇
妇产科学   8篇
基础医学   264篇
口腔科学   26篇
临床医学   140篇
内科学   389篇
皮肤病学   10篇
神经病学   263篇
特种医学   50篇
外科学   179篇
综合类   15篇
一般理论   2篇
预防医学   93篇
眼科学   20篇
药学   184篇
肿瘤学   187篇
  2021年   24篇
  2019年   19篇
  2018年   18篇
  2017年   15篇
  2016年   20篇
  2015年   21篇
  2014年   28篇
  2013年   37篇
  2012年   60篇
  2011年   70篇
  2010年   44篇
  2009年   54篇
  2008年   67篇
  2007年   76篇
  2006年   89篇
  2005年   70篇
  2004年   73篇
  2003年   72篇
  2002年   67篇
  2001年   71篇
  2000年   93篇
  1999年   72篇
  1998年   17篇
  1997年   18篇
  1996年   18篇
  1995年   25篇
  1994年   12篇
  1993年   12篇
  1992年   36篇
  1991年   45篇
  1990年   51篇
  1989年   33篇
  1988年   46篇
  1987年   38篇
  1986年   44篇
  1985年   54篇
  1984年   20篇
  1983年   18篇
  1982年   13篇
  1980年   10篇
  1979年   20篇
  1978年   15篇
  1977年   19篇
  1976年   13篇
  1975年   17篇
  1974年   14篇
  1973年   13篇
  1972年   11篇
  1970年   11篇
  1968年   12篇
排序方式: 共有1871条查询结果,搜索用时 15 毫秒
1.
We documented the risks associated with windsurfing on sewage polluted water. Seventy-nine windsurfers and 41 controls were studied over a nine-day period for occurrence of symptoms of gastroenteritis, otitis, conjunctivitis, and skin infection. Relative risks were 2.9 for occurrence of one or more of these symptoms and 5.5 for symptoms of gastroenteritis. Relative risk increased with the reported number of falls into the water.  相似文献   
2.
3.
A 34-year-old woman with no family history of orthochromatic leukodystrophy (OLD) developed progressive intellectual deterioration, a frontal syndrome and spastic tetraparesis. She died four years after the onset of the clinical illness. Neuropathological studies included light and electron microscopy of cerebral and nerve biopsies, and a complete postmortem examination. Light microscopy demonstrated OLD with pigmented macrophages and glial cells. Electron microscopy showed electron-dense, membrane-bound intracytoplasmic lamellar inclusions with curved or straight parallel arrangement, or fingerprint pattern, in white matter macrophages, astrocytes and oligodendrocytes. Cortical cells contained lipofuscin which was normal in type and amount. This suggests that the material in white matter glial cells and macrophages is ceroid pigment, however, the distribution is not that seen in ceroid-lipofuscinosis. Similar inclusions have been found in oligodendrocytes in other forms of OLD. Biochemical study did not show evidence of demyelination. Galactolipids were normal. Polyunsaturated fatty acids were decreased. The most striking feature was an increase in plasmalogens.  相似文献   
4.
5.
Poly(ADP-ribose) (polymer) is enzymatically synthesized on nuclearproteins in response to DNA strand breaks. NAD+ is the substratefor this reaction, which is catalyzed by Poly(ADP-ribose)polymerase.This post-translational modification occurs in response to DNAstrand breaks and is thought to play an important role in DNArepair. Polymer synthesis resulting from DNA damage has beendescribed in cultured cells, but measurement is more difficultin animal tissues. In this study, modifications were made toan earlier method to measure carcinogen-induced increases inpolymer levels in vivo. RNase I was added to the enzyme mixtureused to digest polymer to ribosyladenosine (RAdo). This preventedthe inhibition of snake venom phosphodiesterase by RNA. TheHPLC analysis was improved, allowing elimination of the secondboronate affinity chromatography step traditionally used topurify  相似文献   
6.
7.
Cytomegalovirus (CMV) antigenemia was directly detected in polymorphonuclear leukocytes (PMNLs) from transplant recipients by using flow cytometry (FC). Two fixation and permeabilization methods and seven anti-CMV monoclonal antibodies (MAbs) were evaluated. 1C3, SL20, and NEA-9221 MAbs were more efficacious. The antigenemia detection threshold of FC was 0.05% positive PMNLs, and percentages correlated well with DNA viral load and the appearance of clinical symptoms.  相似文献   
8.
Liver homogenates from rats fed tamoxifen (TAM) in the diet were shared among four different laboratories. TAM-DNA adducts were assayed by high pressure liquid chromatography-electrospray tandem mass spectrometry (HPLC-ES-MS/MS), TAM-DNA chemiluminescence immunoassay (TAM-DNA CIA), and (32)P-postlabeling with either thin layer ((32)P-P-TLC) or liquid chromatography ((32)P-P-HPLC) separation. In the first study, rats were fed a diet containing 500 p.p.m. TAM for 2 months, and the values for measurements of the (E)-alpha-(deoxyguanosin-N(2)-yl)-tamoxifen (dG-N(2)-TAM) adduct in replicate rat livers varied by 3.5-fold when quantified using 'in house' TAM-DNA standards, or other approaches where appropriate. In the second study, rats were fed 0, 50, 250 or 500 p.p.m. TAM for 2 months, and TAM-DNA values were quantified using both 'in house' approaches as well as a newly synthesized [N-methyl-(3)H]TAM-DNA standard that was shared among all the participating groups. In the second study, the total TAM-DNA adduct values varied by 2-fold, while values for the dG-N(2)-TAM varied by 2.5-fold. Ratios of dG-N(2)-TAM:(E)-alpha-(deoxyguanosin-N(2)-yl)-N-desmethyltamoxifen (dG-N(2)-N-desmethyl-TAM) in the second study were approximately 1:1 over the range of doses examined. The study demonstrated a remarkably good agreement for TAM-DNA adduct measurements among the diverse methods employed.  相似文献   
9.
A novel HLA-B*39 variant, found in an African patient with sickle cell anemia undergoing bone marrow transplantation is described. Initially suspected by inconsistent serological typing (B-blank, Bw6), then recognized by PCR-SSP, and finally characterized by nucleotide sequencing, this novel allele is designated HLA-B*3916. It differs from HLA-B*3910 by a point mutation (G to C) at position 17 of exon 3 causing glutamine to histidine change at codon 96 of alpha(2) domain, a conserved position among HLA class I alleles. cDNA sequence analysis further revealed the presence of both normally and abnormally spliced mRNA species in established cell lines. The abnormal species correspond to partial truncation of exon 3 presumably due to the nucleotide change in exon 3, which constitutes a new consensus acceptor splice site within this exon. We postulate that the observed blank is essentially the consequence of qualitative change in a critical region of this novel antigen as abnormal mRNA species are relatively less abundant than normal species. Because the residue 96 of the HLA class I heavy chain is directly involved in interaction with alpha(2)m, another interesting possibility is that an aminoacid change in this position would perturb such interaction and consequently could affect the serological specificity of B*3916, or its expression or both.  相似文献   
10.
Hepatitis A virus (HAV) is a worldwide disease; in most cases, it causes an acute self-limited illness that does not lead to a chronic state. The course of HAV viremia in a homosexual male with human immunodeficiency virus type 1 (HIV-1) and the correlation between HIV and HAV viral load, alanine aminotranferase (ALT) level, and CD4(+) lymphocyte count were investigated during the course of the infection. HAV RNA was detected quantitatively up to 256 days after clinical onset. To our knowledge, this specific case is the first report of a prolonged infection with hepatitis A in a male with HIV-1. The ALT levels decreased gradually; however, 286 days after clinical onset of hepatitis, ALT levels were three times higher than normal values. HIV viral load was not affected by the infection with HAV and CD4(+) cell count was stable during the course of the co-infection. The duration and the high-titer viremia of hepatitis A virus in an immunodeficient patient constitute a serious risk of the spread of hepatitis A within this population. As inactivated HAV vaccine is safe in HIV-positive subjects, it would be wise to establish a strategy of preventive vaccination in this high-risk group.  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