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   2867篇
  免费   233篇
  国内免费   26篇
耳鼻咽喉   25篇
儿科学   87篇
妇产科学   42篇
基础医学   416篇
口腔科学   31篇
临床医学   220篇
内科学   533篇
皮肤病学   353篇
神经病学   237篇
特种医学   106篇
外科学   397篇
综合类   17篇
预防医学   184篇
眼科学   123篇
药学   123篇
中国医学   8篇
肿瘤学   224篇
  2023年   24篇
  2022年   42篇
  2021年   94篇
  2020年   72篇
  2019年   74篇
  2018年   89篇
  2017年   74篇
  2016年   99篇
  2015年   72篇
  2014年   90篇
  2013年   133篇
  2012年   184篇
  2011年   218篇
  2010年   132篇
  2009年   119篇
  2008年   184篇
  2007年   160篇
  2006年   180篇
  2005年   123篇
  2004年   139篇
  2003年   135篇
  2002年   127篇
  2001年   65篇
  2000年   50篇
  1999年   43篇
  1998年   30篇
  1997年   15篇
  1996年   14篇
  1995年   17篇
  1994年   21篇
  1993年   15篇
  1992年   17篇
  1991年   14篇
  1990年   13篇
  1989年   7篇
  1988年   10篇
  1987年   15篇
  1986年   12篇
  1985年   13篇
  1984年   10篇
  1983年   8篇
  1981年   10篇
  1980年   16篇
  1979年   13篇
  1978年   16篇
  1977年   10篇
  1973年   6篇
  1972年   7篇
  1971年   13篇
  1966年   8篇
排序方式: 共有3126条查询结果,搜索用时 46 毫秒
1.
2.
Metabolomics may reveal novel insights into the etiology of prostate cancer, for which few risk factors are established. We investigated the association between patterns in baseline plasma metabolite profile and subsequent prostate cancer risk, using data from 3,057 matched case–control sets from the European Prospective Investigation into Cancer and Nutrition (EPIC). We measured 119 metabolite concentrations in plasma samples, collected on average 9.4 years before diagnosis, by mass spectrometry (AbsoluteIDQ p180 Kit, Biocrates Life Sciences AG). Metabolite patterns were identified using treelet transform, a statistical method for identification of groups of correlated metabolites. Associations of metabolite patterns with prostate cancer risk (OR1SD) were estimated by conditional logistic regression. Supplementary analyses were conducted for metabolite patterns derived using principal component analysis and for individual metabolites. Men with metabolite profiles characterized by higher concentrations of either phosphatidylcholines or hydroxysphingomyelins (OR1SD = 0.77, 95% confidence interval 0.66–0.89), acylcarnitines C18:1 and C18:2, glutamate, ornithine and taurine (OR1SD = 0.72, 0.57–0.90), or lysophosphatidylcholines (OR1SD = 0.81, 0.69–0.95) had lower risk of advanced stage prostate cancer at diagnosis, with no evidence of heterogeneity by follow-up time. Similar associations were observed for the two former patterns with aggressive disease risk (the more aggressive subset of advanced stage), while the latter pattern was inversely related to risk of prostate cancer death (OR1SD = 0.77, 0.61–0.96). No associations were observed for prostate cancer overall or less aggressive tumor subtypes. In conclusion, metabolite patterns may be related to lower risk of more aggressive prostate tumors and prostate cancer death, and might be relevant to etiology of advanced stage prostate cancer.  相似文献   
3.

Background  

For patients suffering of recurrent breast cancer within the irradiated breast, generally mastectomy is recommended. The normal tissue tolerance does not permit a second full-dose course of radiotherapy to the entire breast after a second breast-conserving surgery (BCS). A novel option is to treat these patients with partial breast irradiation (PBI). This approach is based on the hypothesis that re-irradiation of a limited volume will be effective and result in an acceptable frequency of side effects. The following report presents a single center experience with intraoperative radiotherapy (IORT) during excision of recurrent breast cancer in the previously irradiated breast.  相似文献   
4.
Thirteen children with acute lymphoblastic leukemia (ALL) were investigated before and during cytotoxic therapy. EEG findings were correlated with the clinical course and the therapy protocol and compared with normal data obtained from 295 healthy children. Frequency analysis of the background activity of the EEG revealed an initial slowing of the background activity prior to therapy and further slowing each time a combination of vincristine (VCR), daunorubicine (DAU) or adriblastine (ADR), prednisone (FRED), and L-asparaginase (L-ASP) was administered. The slowing of the background activity correlated only with the administration of these drugs. DAU, ADR, and FRED are not known to influence the EEG; therefore, VCR and L-ASP remain the primary candidates responsible for the central nervous system alteration.  相似文献   
5.
Circulating monocytes from hypertensive patients show elevated secretion patterns of pro-inflammatory cytokines, an increased expression of adhesion molecules, and an increased adhesion to vascular endothelial cells. We tested the hypothesis that telmisartan, an angiotensin II type 1 (AT(1)) receptor antagonist, reduces the activation of circulating monocytes from hypertensive patients and diminishes the monocyte-endothelial cell adhesion. Monocytes of 20 hypertensive patients and 20 normotensive controls were isolated by density gradient centrifugation and Dynabeads, and the monocyte adhesion to human aortic endothelial cell monolayers was measured by adhesion assays. To characterize monocyte activation we assessed the expression of activity-related cell surface markers that are also involved in monocyte adhesion to endothelial cells, such as CD11a/b and CD54, as well as the chemokine receptors CCR1, CCR2 and CCR5 before and after telmisartan therapy using flow cytometry. Spontaneous adhesion of monocytes from hypertensive patients and the adhesion after stimulation with angiotensin II were significantly increased compared with those in normotensive controls (p<0.05). Treatment of hypertensive patients with the AT(1) receptor antagonist telmisartan significantly diminished the adhesion of circulating monocytes to human endothelial cells (p=0.02) despite the increase in the expressions of CD11b, CD54 and CCR5 after telmisartan therapy. Reducing monocyte adhesion may be a novel beneficial effect of the AT(1) receptor antagonist telmisartan helping to prevent vascular alterations in hypertension. The mechanism of action remains to be elucidated, since reduction in monocyte adhesion was not attributable to changes in adhesion molecule expression.  相似文献   
6.
7.
Cyclic nucleotides are important second messengers that mediate a number of cellular responses to external signals. Cyclic nucleotide phosphodiesterases play a role in signal transduction by regulating the cellular concentrations of these messengers. Here, we have applied Southern analyses of somatic cell hybrid lines and of recombinant inbred (RI) mouse strains as well as fluorescence chromosomal in situ hybridization (FISH) to chromosomally localize five cAMP-specific nucleotide phosphodiesterase genes in human and mouse. GenesDPDE1, DPDE2, DPDE3, andDPDE4 that share sequence homology with theDrosophila dunce gene were assigned to human chromosomes 19 (DPDE1 andDPDE2), 5q12 (DPDE3), and 1p31 (DPDE4) and to mouse chromosomes 8, 9, 13, and 4, respectively. The high-affinity cAMP-specific phosphodiesterase gene (HCP1) was mapped to human chromosome 8q13-q22. Since these genes are potential candidates for involvement in psychiatric or behavioral disorders, knowledge of their chromosomal localizations will facilitate the discovery of their association with disease genes as they are being mapped by linkage studies.  相似文献   
8.
9.
AIM: The aim of this study is to compare the Lich-Gregoir procedure and antireflux ureterocystoneostomy at the vertex of the bladder (AUVB) based on 20 years' clinical experience. METHODS: Over a period of 20 years (1978 - 1998) 1280 children were operated on, 368 bilaterally, which resulted in 1648 antireflux ureterocystoneostomies being performed. Of the total of 1648 antireflux ureterocystoneostomies, AUVB was performed in 1032 ureteric units and the Lich-Gregoir procedure in 616 ureteric units. Between 1978 and 1992 we performed only AUVB, and from 1992, both AUVB and the Lich-Gregoir procedure. RESULTS: The final result was evaluated 2 years after the operation. Satisfactory results were achieved in 93.5 % with AUVB and in 96 % with the Lich-Gregoir procedure. The postoperative failure rate was 6.5 % for the AUVB and 4 % for the Lich-Gregoir operations. The recurrence rate was higher with AUVB (5 %) than with the Lich-Gregoir procedure (1.5 %), but postoperative stenosis was more frequent with the Lich-Gregoir procedure (2.5 %). CONCLUSIVE: Today, as the first operative method we prefer to employ the Lich-Gregoir procedure. If the result of the Lich-Gregoir procedure is unsatisfactory, we recommend the AUVB for the first and second recurrence operation. Finally, in cases of repeated VUR recurrence of postoperative stenosis, as the last operation we perform antireflux ureteroileocystoplasty with an intussuscepted segment of the ileum.  相似文献   
10.
Endothelial selectins are crucial for the recruitment of leukocytes into sites of inflammation. On T cells, ligands for selectins become induced upon differentiation into the effector/memory stage. Initial in vitro studies suggested a correlation between the Th1 phenotype and ligand expression, but whether this also holds true in vivo remained uncertain. We here analyzed selectin ligands on CD4+ T cells producing IFN-gamma, IL-4 or IL-10, prototypic cytokines of the Th1, Th2 and Tr1 subset, respectively. We analyzed mice infected with influenza virus, the bacterium Listeria, and the parasites Toxoplasma (all Th1 models) or Nippostrongylus (Th2 model). A link between the Th1 phenotype and ligand expression was not found in vivo. Surprisingly, the potentially regulatory IL-10-producing T cells displayed the highest frequency of ligand-positive cells in general. Within the inflamed tissues, the frequencies of P-selectin-binding cells increased in the dominant subset, either Th1 or Th2. Up-regulation was also found for E-selectin ligands during influenza, but not Nippostrongylus infection. In conclusion, conditions driving T cell polarization into either Th1 or Th2 in vivo do not affect the expression of selectin ligands, but acquisition of P-selectin binding and hence migration into inflamed tissues is boosted by an inflammatory milieu.  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