全文获取类型
收费全文 | 440篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
耳鼻咽喉 | 18篇 |
儿科学 | 37篇 |
妇产科学 | 5篇 |
基础医学 | 73篇 |
口腔科学 | 9篇 |
临床医学 | 62篇 |
内科学 | 39篇 |
皮肤病学 | 14篇 |
神经病学 | 25篇 |
特种医学 | 40篇 |
外科学 | 49篇 |
综合类 | 26篇 |
预防医学 | 23篇 |
眼科学 | 1篇 |
药学 | 16篇 |
中国医学 | 4篇 |
肿瘤学 | 21篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2015年 | 9篇 |
2014年 | 26篇 |
2013年 | 25篇 |
2012年 | 21篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 5篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 19篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1969年 | 3篇 |
1957年 | 2篇 |
1956年 | 2篇 |
1954年 | 2篇 |
1952年 | 16篇 |
1951年 | 23篇 |
1950年 | 2篇 |
排序方式: 共有462条查询结果,搜索用时 437 毫秒
1.
用体外培养的人的伪表皮作为模型,进行药物毒理学作用的研究,观察了二甲亚砜(DMSO)在不同浓度和不同接触时间条件下,对人的伪表皮细胞脱氧核糖核酸(DNA)、核糖核酸(RNA)和蛋白质合成的影响:随着接触时间的延长,DNA、RNA和蛋白质合成均受抑制。低浓度条件下(1%),DNA、RNA和蛋白质合成增加;在15~50%浓度下,DNA和蛋白质合成抑制,而RNA合成仍增加;在高浓度条件下(70%~100%),DNA、RNA和蛋白质合成均明显抑制。 相似文献
2.
3.
4.
5.
Telfer JF; Thomson AJ; Cameron IT; Greer IA; Norman JE 《Human reproduction (Oxford, England)》1997,12(10):2306-2312
Superoxide, an agent which attenuates the half-life of nitric oxide, is
metabolized and synthesized by superoxide dismutase (SOD) and xanthine
oxidase, respectively. Over the last few years much work has focused on the
role of nitric oxide in human parturition. The aim of this study was to
determine whether the onset of human parturition is associated with a
change in the expression of copper/zinc superoxide dismutase (Cu/Zn SOD),
manganese superoxide dismutase (Mn SOD) or xanthine oxidase within the
uterus. Samples of myometrium, placenta, decidua and fetal membranes were
obtained from women before and after the onset of labour at term.
Immunocytochemistry was used to localize Cu/Zn SOD, Mn SOD and xanthine
oxidase and measure SOD enzyme activity. Cu/Zn and Mn SOD-like
immunoreactivity was detected in syncytiotrophoblast cells, villous stromal
cells and endothelial cells of blood vessels in the placenta. In the
myometrium Cu/Zn and Mn SOD were localized to myocytes and endothelial
cells and to some vascular smooth muscle cells. In the fetal membranes we
observed staining for Cu/Zn SOD and Mn SOD in the amnion, chorion,
extravillous trophoblast and decidua. There was no difference in SOD enzyme
activity or staining intensity for SOD between different cell types before
and during labour. Xanthine oxidase immunoreactivity was identified in each
of the tissues examined and again there was no difference in immunostaining
in tissues obtained from women delivered before or after the onset of
labour. These results show that the pregnant uterus is capable of both
synthesizing and degrading superoxide and suggest that superoxide dismutase
and xanthine oxidase may play a role in the maintenance of uterine
quiescence during pregnancy, but not in the initiation of parturition.
相似文献
6.
Pre-eclampsia, one of the most significant health problems inhuman pregnancy, complicates 6-7% of all gestations and is theleading cause of fetal growth retardation, infant morbidityand mortality, premature birth and maternal death. Recent researchimplicates free radicals in the pathophysiology of pre-eclampsia.This review covers the biochemistry of nitric oxide (NO) andpossible interactions with other free radicals. Studies in therat show that pregnancy is associated with enhanced productionand responsiveness to NO in both reproductive tissues and bloodvessels. Rats infused with NG-nitro-L-arginine methyl ester(L-NAME, a NO synthase inhibitor) have been used as an animalmodel of pre-eclampsia, and the effects of steroid hormoneson blood pressure in this model have been tested. Results suggestthat pre-eclampsia may be a state of NO deficiency. However,in humans there seem to be contradictions regarding the involvementof NO in maternal adaptation to pregnancy. It is suggested thatNO may be one of several systems that act in concert to maintaina symbiotic relationship between mother and fetus. However,the input of each system may be genetically determined. 相似文献
7.
Matrix Metalloproteinase and Cytokine Profiles in Monocytes over the Course of Stroke 总被引:14,自引:0,他引:14
Mathilde Kouwenhoven Christian Carlstrõm Volkan Õzenci Hans Link 《Journal of clinical immunology》2001,21(5):365-375
Stroke is a common cause of death and disability in our society. Stroke is associated with changes in immune responses within the central nervous system as well as systemically. The cells contributing to such changes as well as the factors contributing to formation of the inflammatory infiltrate observed in stroke remain to be clarified. In this study, blood monocytes and corresponding mononuclear cells (MNC) were separated and examined in parallel within 4 days and 1–3 months after onset of ischemic stroke. Numbers of TNF--, IL-12-, IL-6-, and IL-10-secreting cells and of cells expressing mRNA for matrix metalloproteinase (MMP)-1, -2, -7, -9 and tissue inhibitor of MMP (TIMP)-1 were studied. The TNF--, IL-12-, and IL-6-secreting monocytes and MNC were elevated during the acute phase compared to healthy controls. Such differences were not observed when stroke patients were examined during convalescence. The IL-10-secreting monocytes did not change over the course of stroke. Levels of monocytes expressing MMP-1, MMP-7 and TIMP-1 mRNA were elevated in the acute phase of stroke patients compared to convalescence and healthy controls, as were levels of MMP-1, -2, -7, -9 and TIMP-1 mRNA expressing blood MNC. The MMP-2 and -9 activity as measured by zymography also was higher in MNC supernatants in the acute phase of stroke compared to convalescence. The high levels of proinflammatory cytokines and MMPs in blood monocytes and MNC further demonstrate the presence of systemic aberrations in the acute phase of stroke. Such changes may contribute to the influx of blood-borne cells into the ischemic lesions during the acute phase of stroke. 相似文献
8.
Summary Biochemical investigation of the fluid surrounding the sporocysts in the oocysts (oocyst fluid) showed the presence of the common amino acids, -isoaminobutyric acid, glycerol, an unidentified carbohydrate and proteins.Incubation experiments with D-glucose-14C (U) revealed the presence of enzymes able to convert glucose into lactic acid and other acids. Inside the sporocysts the common amino acids, glycerol and the unidentified carbohydrate were also present, but -isoaminobutyric acid did not occur. The carbohydrate binding protein carboglutelin, carbohydrate phosphate and small amounts of glucose and fructose were mainly found inside the sporocysts.Incubation experiments of oocyst fluid mixed with sporocysts with D-glucose-C14 (U) demonstrated an interchange between the fluid and the sporocysts. In the oocyst fluid lactic acid was formed, but inside the sporocysts the conversion appeared to stop mainly with formation of carbohydrate phosphate.Incubation experiments of intestinal pieces both from immunized and not-immunized birds with oocyst fluid, sporocysts and labelled glucose showed that a stronger reaction took place in immunized birds than in not-immunized ones.Similar experiments were performed with not-immunized birds at different days after a primary infection. The reaction of the intestinal wall, which seemed quite normal again since day 19 after infection, was comparable with that observed in immunized birds.Finally the hypothesis is given, that in the first part of the intestine of immunized birds compounds are present originating from the first infection. These compounds might enhance the reaction between the oocyst fluid and the present feed to such an extent that the pH decreases and much epithelial cells are pushed off possibly together with the sporocysts. Then leakage of serum proteins might occur. 相似文献
9.
Debelenko LV; Brambilla E; Agarwal SK; Swalwell JI; Kester MB; Lubensky IA; Zhuang Z; Guru SC; Manickam P; Olufemi SE; Chandrasekharappa SC; Crabtree JS; Kim YS; Heppner C; Burns AL; Spiegel AM; Marx SJ; Liotta LA; Collins FS; Travis WD; Emmert-Buck MR 《Human molecular genetics》1997,6(13):2285-2290
Lung carcinoids occur sporadically and rarely in association with multiple
endocrine neoplasia type 1 (MEN1). There are no well defined genetic
abnormalities known to occur in these tumors. We studied 11 sporadic lung
carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene
on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy
fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was
studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene
were inactivated. All four tumors showed the presence of a MEN1 gene
mutation and loss of the other allele. Observed mutations included a 1 bp
insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide
substitution affecting a donor splice site. Each mutation predicts
truncation or potentially complete loss of menin. The remaining seven
tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH.
The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a
complex germline MEN1 gene mutation. The data implicate the MEN1 gene in
the pathogenesis of sporadic lung carcinoids, representing the first
defined genetic alteration in these tumors.
相似文献
10.
散发内淋巴囊瘤VHL基因位点微卫星标志杂合性丢失的研究 总被引:1,自引:0,他引:1
目的 探讨散发内淋巴囊瘤发病与VHL基因异常之间的关系。方法 采用组织微切割技术和多聚酶链式反应等方法对3例散发内淋巴囊瘤肿瘤细胞VHL基因位点染色体微卫星标志的杂合性丢失进行分析。结果 3例散发内淋巴囊瘤中有2例发生VHL基因位点微卫星标志的杂合性丢失,进一步的研究证实,该两例肿瘤细胞中分别存在着VHL基因第二外显子的异常。结论 VHL基因的异常导致其功能改变不但是VHL的致病原因,而且是散发性内淋巴囊瘤发病的重要的基因遗传学基础。 相似文献