全文获取类型
收费全文 | 435篇 |
免费 | 8篇 |
国内免费 | 34篇 |
专业分类
儿科学 | 16篇 |
妇产科学 | 1篇 |
基础医学 | 39篇 |
口腔科学 | 8篇 |
临床医学 | 42篇 |
内科学 | 50篇 |
皮肤病学 | 6篇 |
神经病学 | 3篇 |
特种医学 | 170篇 |
外科学 | 36篇 |
综合类 | 19篇 |
预防医学 | 34篇 |
眼科学 | 11篇 |
药学 | 23篇 |
中国医学 | 1篇 |
肿瘤学 | 18篇 |
出版年
2022年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 10篇 |
2014年 | 10篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 19篇 |
2009年 | 37篇 |
2008年 | 20篇 |
2007年 | 29篇 |
2006年 | 29篇 |
2005年 | 28篇 |
2004年 | 13篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 15篇 |
2000年 | 3篇 |
1999年 | 16篇 |
1998年 | 26篇 |
1997年 | 33篇 |
1996年 | 20篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1988年 | 18篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 3篇 |
排序方式: 共有477条查询结果,搜索用时 0 毫秒
471.
目的:观察航天应急返回过程中高正加速度( Gx)对肝脏细胞c-fos基因表达的影响.方法:选用♂猕猴(共9只)为对象,随机分为4组,对照组承受 1Gx,300 s的超重作用;实验组根据承受过载峰值的大小分为3个亚组,其承受过载峰值分别为 15Gx,200 s; 18Gx, 165 s; 21Gx,140 s.观察高 Gx对猴肝脏细胞c-fos基因表达的影响.结果:实验组肝脏细胞胞质呈现不同程度的水肿及泡状变性,c-fos基因表达明显增强,呈弥漫性细胞质内棕黄色着色;肝细胞c-fos基因表达程度随超重剂量的增加有增强趋势.对照组肝脏组织病理学改变程度明显较实验组轻微,c-fos基因表达亦明显减弱.结论: Gx可引起猴肝脏组织细胞c-fos基因表达增强,提示有早期肝脏组织损伤. 相似文献
472.
473.
Murine thymocytes proliferate in direct response to interleukin-7 总被引:22,自引:2,他引:22
Conlon PJ; Morrissey PJ; Nordan RP; Grabstein KH; Prickett KS; Reed SG; Goodwin R; Cosman D; Namen AE 《Blood》1989,74(4):1368-1373
The ability of interleukin-7 (IL-7) to stimulate murine thymocyte proliferation was investigated. IL-7, either alone or in concert with lectin, induced proliferation of adult thymocytes as well as day 13 fetal and adult CD4-/CD8-thymocytes. The IL-7-induced proliferative response of unfractionated thymocytes could not be inhibited by antibodies to IL-2, or IL-4, IL-6, or the IL-2 receptor. In addition, IL-2, IL-4, and IL-6 were not produced by thymocytes activated with IL- 7, as judged by the absence of biologically active cytokine in IL-7- stimulated culture supernatants. IL-7 could act in concert with IL-2 and IL-4 or with IL-4 to enhance the proliferative response of thymocyte cultures. Thus, IL-7 may cause proliferation of thymocytes directly, not indirectly, through production of IL-2, IL-4, or IL-6. IL- 7 may then play a significant role in differentiation of T lymphocytes. 相似文献
474.
Ofer S; Fibach E; Kessel M; Bauminger ER; Cohen SG; Eikelboom J; Rachmilewitz EA 《Blood》1981,58(2):255-262
Hemoglobin and ferritin iron content have been followed during differentiation in tissue cultures of murine erythroleukemia cells (MELC) using the techniques of Mossbauer spectroscopy and electron microscopy. In undifferentiated cells grown without DMSO, only iron stored in ferritin was detected. The amount of iron in a cell grown in the presence of iron citrate is approximately 1.2 X 10(-14) g, whereas in a cell grown in the presence of transferrin the amount is approximately 0.28 X 10(-14) g. These quantities do not depend on the iron concentration in the nutrition medium in a range from 0.3 to 2.0 microgram Fe/ml and are the same for growth times between 8 hr and 7 days. Cells grown with DMSO contain, in addition to ferritin, increasing concentrations of hemoglobin. Chase experiments prove that ferritin iron participates in hemoglobin synthesis. The amount of ferritin iron reaches saturation within less than 8 hr in MELC grown with or without DMSO. In differentiating cells grown with iron citrate there is a decrease with time in ferritin iron content concomitant with the increase in hemoglobin. Cells grown with transferrin incorporate additional amounts of iron, which are approximately equal to the amounts used for hemoglobin synthesis maintaining a constant ferritin iron level. In the electron microscope, iron is seen only as ferritin within lysosomes. The density of the ferritin in lysosomes correlates with the ferritin iron concentrations determined by Mossbauer spectroscopy. 相似文献
475.
In a registry of volunteer bone marrow donors, the relation between registry size and probability of finding an exact or partial match for a random recipient cannot be theoretically derived because it depends on specifics of the human leukocyte antigen (HLA) haplotype frequencies in the donor and recipient populations. The relation must be explicitly calculated using empirically determined HLA haplotype frequency data for all possible pairings between a donor and a recipient population. This report describes a general solution to this problem. The method shows that the relation of the probability of matching to registry size is sigmoidal, with small increases in probability at the extremes of registry size and a middle range of registry size within which the probability of matching increases most sharply. This range determines the approximate size of the most cost-effective registry. In addition, for any pairing of donor and recipient populations, there is a maximum probability of identifying a match of a given quality for a random recipient, which cannot be exceeded even if registry size were infinite. This upper limit is a function of the frequency of blank (or unknown) alleles in the donor and recipient populations; the higher that frequency, the lower the maximum probability of achieving any given quality of match. The determinants of the probability of achieving a given quality of match with a given registry size are (1) the genetic heterogeneity within the recipient and donor populations, which increases the registry size required to achieve a given probability of matching, and (2) the degree of genetic homology between the donor and recipient populations, which increases the maximum probability of matching and also lowers registry size requirements. The method described here can be used to estimate donor pool size requirements using any donor and recipient populations for which HLA frequency data are available. 相似文献
476.
SH Hejazi SG Hoseini SH Javanmard SH Zarkesh A Khamesipour 《Iranian Journal of Parasitology》2012,7(2):53-60
Background
Cutaneous leishmaniasis is a neglected parasitic disease, which imposes massive human distress and financial costs to the endemic countries. Better understanding of host immune response to the parasite leads to helpful strategies for disease control. Interleukin (IL)-10 and transforming growth factor (TGF)-β are important immune regulatory cytokines, which appear to develop non-healing forms of leishmaniasis. However, there is little information about the function of IL-10 and TGF-β in old world cutaneous leismaniasis. The aim of this study was to analyze the role of IL-10 and TGF-β in human cutaneous leishmaniasis due to Leishmania major infection.Methods
Biopsies were obtained from lesions of twenty proven cases of L. major induced cutaneous leishmaniasis. IL-10 and TGF-β positive cells were detected by immunofluorescence staining of frozen sections and compared between two groups of patients with early and late lesions.Results
The mean percentage of IL-10 positive cells were significantly (P= 0.035) higher in late lesions (0.51±0.24) than early ones (0.15±0.07). Similar results were obtained for TGF-β with mean percentages of 0.16±0.05 and 0.53±0.28 in early and late lesions respectively (P= 0.008).Conclusion
IL-10 and TGF-β are present in lesions of L. major induced cutaneous leishmaniasis and contribute to the pathogenesis of long lasting disease forms. 相似文献477.
BACKGROUND: In the United States, there is a shortage of blood group phenotype-matched red cells (RBCs) for patients with sickle cell disease (SCD). A protocol designed to supply phenotype-matched RBCs for these patients by combining the recruitment of African American blood donors and automated testing of RBCs for these patients for the presumptive Fy(a-b-) phenotype using monoclonal anti-Fy3 was evaluated. STUDY DESIGN AND METHODS: African American donors were recruited, to increase the likelihood of phenotype matches in the donor population. Samples of RBCs were tested for the presumptive Fy(a-b-) phenotype by using monoclonal anti-Fy3 and an automated blood typing analyzer. RBCs confirmed to be Fy(a-b-) were retyped for selected Rh, MNS, Kell, Duffy, and Kidd blood system antigens. The extended phenotypes were matched with those of 41 SCD patients requiring transfusions. RESULTS: Of 8323 blood donations during the study, approximately 40 percent (3329) were made by African Americans. Approximately 22 percent (737) of African Americans were identified as Fy(a-b-) by this protocol and 12 percent (410) were phenotype matches for the 41 SCD patients. CONCLUSION: Combining the recruitment of African American blood donors and automated phenotyping using monoclonal anti-Fy3 offers a practical, relatively low-cost strategy for supplying phenotype-matched RBCs for SCD patients. This protocol increases the options for addressing the shortage of phenotype-matched RBCs for SCD patients. 相似文献