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   8378篇
  免费   564篇
  国内免费   52篇
耳鼻咽喉   43篇
儿科学   223篇
妇产科学   249篇
基础医学   1379篇
口腔科学   182篇
临床医学   901篇
内科学   1667篇
皮肤病学   181篇
神经病学   840篇
特种医学   291篇
外国民族医学   7篇
外科学   736篇
综合类   42篇
一般理论   2篇
预防医学   704篇
眼科学   86篇
药学   658篇
中国医学   19篇
肿瘤学   784篇
  2024年   11篇
  2023年   64篇
  2022年   113篇
  2021年   216篇
  2020年   153篇
  2019年   203篇
  2018年   210篇
  2017年   171篇
  2016年   237篇
  2015年   243篇
  2014年   349篇
  2013年   415篇
  2012年   674篇
  2011年   799篇
  2010年   420篇
  2009年   378篇
  2008年   605篇
  2007年   650篇
  2006年   607篇
  2005年   578篇
  2004年   493篇
  2003年   401篇
  2002年   389篇
  2001年   52篇
  2000年   43篇
  1999年   64篇
  1998年   77篇
  1997年   79篇
  1996年   62篇
  1995年   43篇
  1994年   43篇
  1993年   31篇
  1992年   29篇
  1991年   11篇
  1990年   7篇
  1989年   6篇
  1988年   5篇
  1987年   4篇
  1986年   8篇
  1985年   7篇
  1984年   6篇
  1983年   8篇
  1982年   4篇
  1981年   3篇
  1980年   4篇
  1979年   3篇
  1977年   2篇
  1973年   2篇
  1970年   4篇
  1968年   2篇
排序方式: 共有8994条查询结果,搜索用时 15 毫秒
41.
An unbalanced Y;autosome translocation leading to a male with a 45,X karyotype is rare with about 30 published cases. A male with a 45,X karyotype as a result of a unique, submicroscopic, unbalanced Y;16 translocation is presented with alpha-thalassemia/mental retardation syndrome.  相似文献   
42.
43.
ABSTRACT

We evaluated a blend of medium-chain fatty acids (MCFA), organic acids, and a polyphenol antioxidant on gut integrity. Eighty Ross Broilers were exposed to 20–22°C (control – normothermic) or to 35–39.5°C (heat stress) for eight hours a day for a period of 1 or 5 days. Birds were fed a standard diet, or a diet supplemented with the test blend. Thereafter, birds were euthanized, and intestinal sections were excised for morphological, morphometric and gene expression analyses. Blood samples were collected for glucose-6-phosphate dehydrogenase (G6PD), glutathione peroxidase (GSH-Px) activity and trolox equivalent antioxidant capacity (TEAC) determination. Heart and liver tissues were used to quantify the expression of heat shock proteins 60 and 70 (HSP60 and HSP70, respectively) and inhibitor of kappa light chain gene enhancer in B cells alpha (IKBA). The jejunum was the most sensitive intestinal section, where heat stress modulated the expression of HSP70, of the inflammatory markers IKBA, interleukin 8 (IL-8), interferon gamma (IFNγ), and toll-like receptor 4 (TLR4). Moreover, expression of tight junctions (CLDN1, ZO1 and ZO2) and nutrient transporters (PEPT1 and EAAT3) was modulated especially in the jejunum. In conclusion, the feed additive blend protected intestines during heat stress from the decrease in villus height and crypt depth, and from the increase in villus width. Especially in the jejunum, heat stress played an important role by modulating oxidative stress and inflammation, impairing gut integrity and nutrient transport, and such deleterious effects were alleviated by the feed additive blend.

RESEARCH HIGHLIGHTS
  • Jejunum is the most sensitive intestinal segment during heat stress.

  • Heat stress affects the expression of tight junctions and nutrient transporters.

  • Feed management helps to alleviate the disturbances caused by heat stress.

  • A blend of MCFA, organic acids and a polyphenol protects broilers under heat stress.

  相似文献   
44.
Studies from the last decade on factors influencing reproductive planning after genetic counselling were reviewed. Increased possibilities of DNA-analysis and prenatal diagnosis might have brought about a shift in the paramountcy of factors influencing reproductive planning after genetic counselling. In contrast to the literature in the seventies, the magnitude of the genetic risk was no longer found to be one of the decisive factors in postcounselling reproductive planning. Instead, the interpretation of the risk as high or low and the desire to have children appeared to be paramount. The impact of new developments in DNA-analysis in prenatal diagnosis and presymptomatic testing will be an important subject for future studies on factors influencing reproductive planning.  相似文献   
45.
Summary Ten healthy sedentary subjects [age, 27.5 (SD 3.5) years; height, 180 (SD 5) cm; mass, 69.3 (SD 6.3) kg] performed two periods of maximal incremental graded cycle ergometer exercise in a supine position. Randomly ordered and using an open spirometric system, one exercise was carried out during normoxia [maximal oxygen consumption ( O2max)=38.6 (SD 3.5) ml·min–1·kg–1; maximal blood lactate concentration, 9.86 (SD 1.85) mmol·l–1; test duration, 22.6 (SD 2.7) min], the other during hypoxia [ O2max=33.2 (SD 3.2) ml·min–1· kg–1; maximal blood lactate concentration, 10.38 (SD 2.02) mmol·l–1; test duration, 19.7 (SD 2.8) min]. At rest, immediately (0 p) and 60 min (60 p) after exercise, counts of leucocyte subpopulations (flow cytometry), cortisol and catecholamine concentrations were determined. At 0 p in contrast to normoxia, during hypoxia there was no significant increase of granulocytes. There were no significant differences between normoxia and hypoxia in the increases from rest to 0 p in counts of monocytes, total lymphocytes and lymphocyte subpopulations [clusters of differentiation (CD), CD3+, CD4+CD45RO, CD4+CD45RO+, CD8+CD45RO, CD8+CD45RO+, CD3+HLA-DR+, CD3CD16/CD56+, CD3+CD16/CD56+, CD 19+] as well as adrenaline, noradrenaline and cortisol concentrations. The counts of CD3 CD16/CD56+-and CD8 +CD45RO+-cells increased most. At 60 p, CD3CD16/CD56+ and CD3+CD16/CD56+-cell counts were below pre-exercise levels and under hypoxia slightly but significantly lower than under normoxia. We concluded that the exercise-induced mobilization and redistribution of most leucocyte and lymphocyte subpopulations were unimpaired under acute hypoxia at sea level. Reduced increases of granulocyte counts during the study and reduced cell numbers of natural killer cells and cytotoxic, not major histocompatibility complex-restricted T-cells, only indicated marginal effects on the immune system.  相似文献   
46.
The identification of specific genetic loci that contribute to inflammatory and autoimmune diseases has proved difficult due to the contribution of multiple interacting genes, the inherent genetic heterogeneity present in human populations, and a lack of new mouse mutants. By using N-ethyl-N-nitrosourea (ENU) mutagenesis to discover new immune regulators, we identified a point mutation in the murine phospholipase Cg2 (Plcg2) gene that leads to severe spontaneous inflammation and autoimmunity. The disease is composed of an autoimmune component mediated by autoantibody immune complexes and B and T cell independent inflammation. The underlying mechanism is a gain-of-function mutation in Plcg2, which leads to hyperreactive external calcium entry in B cells and expansion of innate inflammatory cells. This mutant identifies Plcg2 as a key regulator in an autoimmune and inflammatory disease mediated by B cells and non-B, non-T haematopoietic cells and emphasizes that by distinct genetic modulation, a single point mutation can lead to a complex immunological phenotype.  相似文献   
47.
Interferon-gamma (IFN-gamma) plays a key role in the induction and maintenance of immunity against intracellular infectious agents. Compared to other species, little is known about the biology of this cytokine in the guinea pig (Cavia porcellus). We found that in contrast to humans and mice, IFN-gamma in the guinea pig did not induce the antiviral state, which in other species leads to protection of IFN-gamma -stimulated fibroblasts from the cytopathic effect (CPE) of subsequent viral infections. As an alternative strategy to detect and quantify guinea pig IFN-gamma activity in vitro, a reporter system using guinea pig fibroblasts transfected with a luciferase gene, which is regulated by an IFN-stimulated response element (ISRE), was established. With the help of the highly sensitive reporter assay system, the biologic activity of recombinant guinea pig IFN-gamma (GpIFN-gamma, from prokaryotic and eukaryotic expression systems was detected. The response to both native and recombinant GpIFN-gamma was inhibited by a rabbit antiserum directed against the recombinant cytokine expressed in Escherichia coli, demonstrating structural and functional homology of native and recombinant GpIFN-gamma. Stimulation with GpIFN-gamma, obtained from transfected cells, induced upregulation of MHC class I expression in a guinea pig fibroblast line. The restricted activity of GpIFN-gamma might have implications for this species' ability to control infections with intracellular pathogens.  相似文献   
48.
49.
Upon the discovery of numerous genes involved in the pathogenesis of neurodevelopmental disorders, several studies showed that a significant proportion of these genes converge on common pathways and protein networks. Here, we used a reversed approach, by screening the AnkyrinG protein-protein interaction network for genetic variation in a large cohort of 1009 cases with neurodevelopmental disorders. We identified a significant enrichment of de novo potentially disease-causing variants in this network, confirming that this protein network plays an important role in the emergence of several neurodevelopmental disorders.Subject terms: Genetics research, Neurological disorders  相似文献   
50.
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