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:      
  示例: 沙坡头地区,人工植被区,变化  检索词用空格隔开表示必须包含全部检索词,用“,”隔开表示只需满足任一检索词即可!
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   401篇
  免费   17篇
耳鼻咽喉   15篇
儿科学   7篇
妇产科学   9篇
基础医学   76篇
口腔科学   17篇
临床医学   40篇
内科学   87篇
皮肤病学   3篇
神经病学   50篇
特种医学   7篇
外科学   38篇
综合类   1篇
预防医学   21篇
眼科学   3篇
药学   27篇
肿瘤学   17篇
  2024年   1篇
  2023年   1篇
  2021年   9篇
  2020年   8篇
  2019年   5篇
  2018年   5篇
  2017年   5篇
  2016年   6篇
  2015年   5篇
  2014年   4篇
  2013年   15篇
  2012年   25篇
  2011年   24篇
  2010年   13篇
  2009年   19篇
  2008年   13篇
  2007年   20篇
  2006年   26篇
  2005年   16篇
  2004年   20篇
  2003年   19篇
  2002年   22篇
  2001年   11篇
  2000年   5篇
  1999年   7篇
  1998年   6篇
  1997年   9篇
  1996年   4篇
  1995年   7篇
  1994年   7篇
  1993年   5篇
  1992年   7篇
  1991年   7篇
  1990年   6篇
  1989年   9篇
  1988年   6篇
  1987年   6篇
  1986年   8篇
  1985年   5篇
  1984年   3篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1970年   2篇
  1969年   3篇
  1968年   2篇
  1966年   1篇
  1828年   2篇
排序方式: 共有418条查询结果,搜索用时 0 毫秒
81.
  总被引:1,自引:0,他引:1  
  相似文献   
82.
We show in this study the need to realize a careful selection of the color to be based on to put a single pre-fabricate guide to be outstanding the advantage and difficulties regarding to another systems. I denote the significance from the anatomic morphology of the restoration as well as the necessity of a defects control from the vision in the clinical like ceramist.  相似文献   
83.
After myocardial infarction, the renin-angiotensin system is found to be activated. While this response may be beneficial in acute failure, it could be detrimental in chronic stages. Therefore effects of captopril therapy were investigated during early and later phases after myocardial infarction in conscious rats, chronically instrumented for hemodynamic measurements. Hemodynamics were measured at baseline and after stimulating the heart by a volume load (cardiac function curve). Myocardial infarction decreased baseline cardiac output and impaired cardiac function, without effects on baseline mean arterial pressure, central venous pressure and heart rate. Captopril given 3 to 5 weeks after infarction improved cardiac function in a dose-dependent manner by increasing stroke volume, whereas stroke work was not affected. In contrast, captopril given from 1 to 21 days after infarction did not lead to improved cardiac function; instead, tachycardia together with a decreased stroke volume suggested deterioration, rather than improvement, of cardiac function. These data indicate that captopril therapy in chronically infarcted conscious rats improved cardiac function when treatment was started after completion of the healing process, but that early treatment not only failed to improve ventricular function, but may have a deleterious effect of the heart.  相似文献   
84.
In earlier experiments chemotactic responsiveness of peripheral blood monocytes obtained from patients with head and neck cancers was found to be markedly depressed. In an attempt to attribute this defect in migration to an influence excited by low molecular weight factors of less than 25,000 daltons, derived from the tumor, Amicon filtrates of head and neck cancer cells were administered sub-cutaneously to C3H mice 24 hrs. before the intraperitoneal injection of concanavelin A. Subsequent macrophage accumulation into the peritoneal cavity was quantified. A clear inhibition of macrophage infiltration was found, particularly when filtrates of poorly differentiated tumors were used. Injection of filtrates from healthy oral mucosa were negative, whereas mouse mammary carcinoma filtrates strongly inhibited accumulation.  相似文献   
85.
In 1969, 1972, 1975 and 1978 dental examinations were carried out in the City of The Hague on cohorts of about 800 children from kindergartens and elementary schools in order to test a (dental) health education program. Since 1980/1981 weekly fluoride mouthrinses have been done in kindergartens and elementary schools in areas with lower SES. In 1981, a baseline dental examination for a follow-up study was carried out on about 500 second grade schoolchildren from areas of low and medium SES. In this baseline examination in 1981 a considerable improvement in dental health was found compared with the earlier cohort examinations, especially in medium SES groups. The average D3MFS value in 1981 was 1.53 and 0.92 for second grade children of the low and medium social level respectively; the average d3fs values were 5.83 and 3.42. Over the 12-yr period (1969-1981) a respective D3MFS reduction of 57.6 and 76.2% was found for low and medium SES. The percentage d3fs reduction for the primary dentition was 55.3 and 72.9%, respectively. In 1978 and 1981 the percentage of children without gingivitis was 26.8 and 31.9%. The difference in the number of gingivitis-free children between 1978 and 1981 seemed to be due to an increase in the number of children without gingivitis in the medium SES groups. A greater use of fluoride tablets was found in low and medium socioeconomic levels between 1972 and 1975, followed by a decrease in the period between 1975 and 1978 and another increase by 1981 compared with 1978.  相似文献   
86.
In fungi, vegetative incompatibility is a conspecific non-self recognition mechanism that restricts formation of viable heterokaryons when incompatible alleles of specific het loci interact. In Podospora anserina, three non-allelic incompatibility systems have been genetically defined involving interactions between het-c and het-d, het-c and het-e, het-r and het-v. het-d and het-e are paralogues belonging to the HNWD gene family that encode proteins of the STAND class. HET-D and HET-E proteins comprise an N-terminal HET effector domain, a central GTP binding site and a C-terminal WD repeat domain constituted of tandem repeats of highly conserved WD40 repeat units that define the specificity of alleles during incompatibility. The WD40 repeat units of the members of this HNWD family are undergoing concerted evolution. By combining genetic analysis and gain of function experiments, we demonstrate that an additional member of this family, HNWD2, corresponds to the het-r non-allelic incompatibility gene. As for het-d and het-e, allele specificity at the het-r locus is determined by the WD repeat domain. Natural isolates show allelic variation for het-r. Sequence data reported here are available in the Genbank database under accession numbers FJ269240 and FJ269239 for het-r and het-R, respectively.  相似文献   
87.
Tumor-specific receptors may provide effective tools for anti-tumor immunogene therapy. However, the functional analysis of primary human T cells engrafted with tumor-specific receptors is laborious and emphasizes the need for a fast and sensitive method to validate such receptors. To this end, we have set up a Jurkat T cell-based reporter gene assay, and tested receptors with various formats, i.e., receptors based on either a monoclonal antibody (mAb), a full-length T cell receptor (fl-TCR)β or a chimeric (ch-)TCRβ, and various antigen specificities for their ability to mediate tumor-specific activation of nuclear factor of activated T cells (NFAT). The mAb-based receptor specifically mediates NFAT activation after stimulation with tumor antigen-positive target cells. The observed receptor-mediated NFAT responses were validated by the use of ligand- and receptor-specific mAbs, as well as cyclosporin A (CsA) and a dominant negative mutant of NFAT. Furthermore, anti-TCR mAbs, peptide-loaded tumor cells and antigen-positive tumor cells all resulted in specific NFAT activation in TCR/CD8 co-transduced Jurkat T cells, irrespective of the TCR format used. Importantly, receptor-mediated NFAT responses parallel tumor-specific cytolysis and TNF production of receptor-transduced primary human T lymphocytes. In fact, inhibition of NFAT activation compromises the immune responses of primary human T lymphocytes, pointing to a central involvement of NFAT in anti-tumor T cell responses. Taken together, receptor-mediated activation of NFAT constitutes a representative measure of anti-tumor T cell responses, and the genetically modified Jurkat T cells provide a flexible and sensitive tool with which to select rapidly tumor-specific (chimeric) receptors for immunogene therapy.  相似文献   
88.
With uniparental inheritance of mitochondria, there seems little reason for homologous recombination in mitochondria, but the machinery for mitochondrial recombination is quite well-conserved in many eukaryote species. In fungi and yeasts heteroplasmons may be formed when strains fuse and transfer of organelles takes place, making it possible to study mitochondrial recombination when introduced mitochondria contain different markers. A survey of wild-type isolates from a local population of the filamentous fungus Podospora anserina for the presence of seven optional mitochondrial introns indicated that mitochondrial recombination does take place in nature. Moreover the recombination frequency appeared to be correlated with age: the more rapidly ageing fraction of the population had a significantly lower linkage disequilibrium indicating more recombination. Direct confrontation experiments with heterokaryon incompatible strains with different mitochondrial markers at different (relative) age confirmed that mitochondrial recombination increases with age. We propose that with increasing mitochondrial damage over time, mitochondrial recombination - even within a homoplasmic population of mitochondria - is a mechanism that may restore mitochondrial function.  相似文献   
89.
Proprotein convertases are serine endoproteases implicated in the proteolytic processing of a large variety of regulatory proteins. An important role of proprotein convertases in tumorigenic processes has been suggested by various studies. In this study, the role of the proprotein convertase furin in PLAG1 proto-oncogene-induced salivary gland tumorigenesis was investigated. PLAG1 overexpression in salivary glands has previously been shown to result in salivary gland tumors in 100% of mice within 5 weeks after birth. MMTV-cre-mediated inactivation of fur without over-expression of PLAG1 caused smaller but histologically normal salivary glands. Moreover, the lymph nodes close to the salivary glands were enlarged, and histology showed that they had activated follicles. When genetic ablation of 1 or 2 alleles of fur and overexpression of the PLAG1 transgene were simultaneously achieved, a significant delay in tumorigenesis was observed. Collectively, these results suggest an important role for furin in PLAG1-induced salivary gland tumorigenesis in mice.  相似文献   
90.
Germ line mutations of the BRCA1 gene confer a high risk of breast cancer and ovarian cancer to female mutation carriers. The BRCA1 protein is involved in the regulation of DNA repair. How specific tumor-associated mutations affect the molecular function of BRCA1, however, awaits further elucidation. Cell lines that harbor BRCA1 gene mutations are invaluable tools for such functional studies. Up to now, the HCC1937 cell line was the only human breast cancer cell line with an identified BRCA1 mutation. In this study, we identified three other BRCA1 mutants from among 41 human breast cancer cell lines by sequencing of the complete coding sequence of BRCA1. Cell line MDA-MB-436 had the 5396 + 1G>A mutation in the splice donor site of exon 20. Cell line SUM149PT carried the 2288delT mutation and SUM1315MO2 carried the 185delAG mutation. All three mutations were accompanied by loss of the other BRCA1 allele. The 185delAG and 5396 + 1G>A mutations are both classified as pathogenic mutations. In contrast with wild-type cell lines, none of the BRCA1 mutants expressed nuclear BRCA1 proteins as detected with Ab-1 and Ab-2 anti-BRCA1 monoclonal antibodies. These three new human BRCA1 mutant cell lines thus seem to be representative breast cancer models that could aid in further unraveling of the function of BRCA1.  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