全文获取类型
收费全文 | 1634篇 |
免费 | 126篇 |
国内免费 | 1篇 |
专业分类
耳鼻咽喉 | 30篇 |
儿科学 | 76篇 |
妇产科学 | 20篇 |
基础医学 | 213篇 |
口腔科学 | 24篇 |
临床医学 | 217篇 |
内科学 | 200篇 |
皮肤病学 | 35篇 |
神经病学 | 155篇 |
特种医学 | 131篇 |
外科学 | 220篇 |
综合类 | 54篇 |
一般理论 | 2篇 |
预防医学 | 177篇 |
眼科学 | 29篇 |
药学 | 101篇 |
中国医学 | 5篇 |
肿瘤学 | 72篇 |
出版年
2021年 | 18篇 |
2020年 | 15篇 |
2019年 | 22篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 19篇 |
2015年 | 26篇 |
2014年 | 45篇 |
2013年 | 59篇 |
2012年 | 74篇 |
2011年 | 45篇 |
2010年 | 45篇 |
2009年 | 39篇 |
2008年 | 57篇 |
2007年 | 72篇 |
2006年 | 80篇 |
2005年 | 61篇 |
2004年 | 71篇 |
2003年 | 65篇 |
2002年 | 58篇 |
2001年 | 47篇 |
2000年 | 40篇 |
1999年 | 47篇 |
1998年 | 32篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 33篇 |
1994年 | 28篇 |
1993年 | 25篇 |
1992年 | 40篇 |
1991年 | 37篇 |
1990年 | 27篇 |
1989年 | 27篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 38篇 |
1985年 | 26篇 |
1984年 | 29篇 |
1983年 | 26篇 |
1982年 | 13篇 |
1981年 | 19篇 |
1980年 | 10篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1974年 | 15篇 |
1973年 | 11篇 |
1972年 | 9篇 |
1952年 | 16篇 |
1951年 | 23篇 |
排序方式: 共有1761条查询结果,搜索用时 15 毫秒
1.
D G Laing 《Physiology & behavior》1986,37(1):163-170
The duration that a single odor needs to be sniffed for identification was determined for 18 humans. A hot wire anemometer and an oscilloscope were used to monitor the duration, volume and inhalation rate of sniffs. In Experiment 1 subjects used 1, 3 or 5 natural sniffs, or an unlimited number of natural sniffs to sample seven dissimilar single odors of moderate perceived intensity, and demonstrated that each odor could be identified with a single sniff. In Experiment 2 subjects demonstrated that each of the odors could be identified with the shortest sniff (0.42 sec) they could physically achieve. In Experiment 3 tests with two of the odorants at several concentrations showed that sniff duration influences identification over a narrow range of concentrations that is just above the recognition threshold. These results together with earlier data that described the optimum conditions for the detection of an odor and the perception of odor intensity, provide information that is necessary for the development of a standard olfactometer and standard methods for human olfactory measurements. 相似文献
2.
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
3.
Abnormalities in glucose metabolism are thought to be among the main causes of cataract formation. The authors have made noninvasive biochemical measurements of the lens that provide information concerning glucose metabolism in the lens epithelium. The autofluorescence of reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) within the rabbit lens were noninvasively measured as a function of depth using redox fluorometry. The peak of the autofluorescence at 440 nm (excited at 360 nm) and 540 nm (excited at 460 nm) were determined at the lens epithelium. When 8 mM sodium pentobarbital, a known inhibitor of mitochondrial respiration, was applied to the lens, the autofluorescence peak at 440 nm increased and that at 540 nm decreased. The 440 nm autofluorescence is thought to be from reduced pyridine nucleotides, whereas the 540 nm autofluorescence is from the oxidized flavoprotein. Blocking lens respiration with pentobarbital caused an increase in the PN/Fp ratio by a factor of 3 within 3.5 hr after pentobarbital application. 相似文献
4.
5.
6.
Numerical comparisons of two formulations of the logistic regressive models with the mixed model in segregation analysis of discrete traits. 总被引:4,自引:0,他引:4
Segregation analysis of discrete traits can be conducted by the classical mixed model and the recently introduced regressive models. The mixed model assumes an underlying liability to the disease, to which a major gene, a multifactorial component, and random environment contribute independently. Affected persons have a liability exceeding a threshold. The regressive logistic models assume that the logarithm of the odds of being affected is a linear function of major genotype effects, the phenotypes of older relatives, and other covariates. A formulation of the regressive models, based on an underlying liability model, has been recently proposed. The regression coefficients on antecedents are expressed in terms of the relevant familial correlations and a one-to-one correspondence with the parameters of the mixed model can thus be established. Computer simulations are conducted to evaluate the fit of the two formulations of the regressive models to the mixed model on nuclear families. The two forms of the class D regressive model provide a good fit to a generated mixed model, in terms of both hypothesis testing and parameter estimation. The simpler class A regressive model, which assumes that the outcomes of children depend solely on the outcomes of parents, is not robust against a sib-sib correlation exceeding that specified by the model, emphasizing testing class A against class D. The studies reported here show that if the true state of nature is that described by the mixed model, then a regressive model will do just as well. Moreover, the regressive models, allowing for more patterns of family dependence, provide a flexible framework to understand gene-environment interactions in complex diseases. 相似文献
7.
B. J. Hales I. A. Laing L. J. Pearce L. A. Hazell K. L. Mills K. Y. Chua R. B. Thornton P. Richmond A. W. Musk A. L. James P. N. LeSouëf W. R. Thomas 《Clinical and experimental allergy》2007,37(9):1357-1363
BACKGROUND: There is evidence that the specificity of the IgE binding in allergy tests can vary for different populations. OBJECTIVE: We aimed to examine the allergenic specificity of IgE binding in sera from house dust mite (HDM)-atopic subjects in a tropical Australian Aboriginal community. METHODS: Sera shown to contain IgE antibodies to an HDM extract of Dermatophagoides pteronyssinus were examined for IgE binding to a panel of nine purified HDM allergens from this mite species by quantitative microtitre assays. IgG antibody binding (IgG1 and IgG4) was also measured. RESULTS: The IgE-binding activity in the sera from the Aboriginal community was not directed to the expected major groups 1 and 2 HDM allergens but instead to the group 4 amylase allergen. There was also little IgE binding to the potentially cross-reactive tropomyosin (Der p 10) or arginine kinase (Der p 20) allergens. The IgG4 antibody was rarely detected and limited to the Der p 4 allergen. IgG1 antibody binding was frequently measured to all the allergens regardless of an individual's atopic status, whereas in urban communities it is restricted to the major allergens and to atopic subjects. CONCLUSION: The high IgE anti-HDM response of Australian Aboriginals predominantly bound Der p 4 and not the Der p 1 and 2 allergens, showing a distinctive allergy that could affect the disease outcome and diagnosis. 相似文献
8.
9.
10.
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