全文获取类型
收费全文 | 58797篇 |
免费 | 5642篇 |
国内免费 | 2138篇 |
专业分类
耳鼻咽喉 | 465篇 |
儿科学 | 572篇 |
妇产科学 | 669篇 |
基础医学 | 8625篇 |
口腔科学 | 1492篇 |
临床医学 | 4786篇 |
内科学 | 6632篇 |
皮肤病学 | 610篇 |
神经病学 | 5535篇 |
特种医学 | 1837篇 |
外国民族医学 | 2篇 |
外科学 | 4876篇 |
综合类 | 9604篇 |
现状与发展 | 5篇 |
预防医学 | 7452篇 |
眼科学 | 1012篇 |
药学 | 6288篇 |
74篇 | |
中国医学 | 3249篇 |
肿瘤学 | 2792篇 |
出版年
2024年 | 318篇 |
2023年 | 1147篇 |
2022年 | 2256篇 |
2021年 | 2701篇 |
2020年 | 2305篇 |
2019年 | 1864篇 |
2018年 | 1794篇 |
2017年 | 2021篇 |
2016年 | 1955篇 |
2015年 | 2150篇 |
2014年 | 3451篇 |
2013年 | 4076篇 |
2012年 | 3332篇 |
2011年 | 3771篇 |
2010年 | 3016篇 |
2009年 | 3103篇 |
2008年 | 3129篇 |
2007年 | 3082篇 |
2006年 | 2678篇 |
2005年 | 2417篇 |
2004年 | 2038篇 |
2003年 | 1815篇 |
2002年 | 1395篇 |
2001年 | 1213篇 |
2000年 | 1118篇 |
1999年 | 961篇 |
1998年 | 789篇 |
1997年 | 724篇 |
1996年 | 674篇 |
1995年 | 616篇 |
1994年 | 584篇 |
1993年 | 462篇 |
1992年 | 428篇 |
1991年 | 383篇 |
1990年 | 325篇 |
1989年 | 306篇 |
1988年 | 248篇 |
1987年 | 235篇 |
1986年 | 212篇 |
1985年 | 304篇 |
1984年 | 244篇 |
1983年 | 157篇 |
1982年 | 163篇 |
1981年 | 157篇 |
1980年 | 126篇 |
1979年 | 105篇 |
1978年 | 69篇 |
1977年 | 38篇 |
1976年 | 45篇 |
1975年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
根管细菌渗漏体外模型的建立 总被引:1,自引:0,他引:1
目的:建立检测微细菌培养模型,以用于评价根管充填封闭情况。方法:牙根的冠根两端各连接一细菌培养储室,冠方储室置1mL无菌培养基并接种0.1mL菌液,根方储室起始为无菌培养基。每隔3d将冠方储室中菌液吸出1mL,并注入1mL新鲜BHI培养基,共90d。当根尖储室中培养基发生浑浊即为细菌渗漏发生,记录细菌渗漏发生时的天数。选择18个直根管前牙,其中牙胶充填组6个,用冷牙胶侧方加压充填技术充填;空管组6个,根管只预备不充填;根管密封组6个,根管充填并严密封闭根管口和根尖孔。用设计的模型检测密封状况。结果:全部空管组6个样本在1d内根方储室中出现浑浊;根管密封组6个样本的根方储室在90d内均未发生浑浊。牙胶充填组有2个样本分别在44d和46d发生浑浊。结论:此模型方法简单易行且实用有效,具有一定的临床相关性和可行性。 相似文献
132.
Evaluation of allergenicity of genetically modified soybean protein extract in a murine model of oral allergen-specific sensitization 总被引:1,自引:0,他引:1
F. Gizzarelli S. Corinti B. Barletta P. Iacovacci B. Brunetto C. Butteroni C. Afferni R. Onori M. Miraglia G. Panzini G. Di Felice R. Tinghino 《Clinical and experimental allergy》2006,36(2):238-248
Background With the development of genetically modified crop plants there has been a growing interest in the approaches available to assess the potential allergenicity of novel gene products. For additional assessment of the potential allergenicity of expressed proteins, informative data can be generated using animal models. Soybean is one of the major source of protein in human and animal nutrition, and has also been well characterized as a major allergenic source. Advances in biotechnology have resulted in an increasing number of genetically engineered foods, and among these soybean is one of the most widespread. Objective To develop and characterize a murine model of IgE‐mediated soybean sensitization induced by intragastric immunization, in the presence of Cholera Toxin, with wild‐type soybean extract (wt‐SE) or with genetically modified soybean extract (gm‐SE). Methods Balb/c mice born in our animal facilities, from females fed on soy‐free food, were fed with the same soy‐free food and used in all the experiments. Mice were sensitized by gavages with soybean extracts, and allergen‐specific IgE and IgG responses were studied by direct ELISA and ELISA inhibition. Antigen‐specific cell proliferation and cytokine production were evaluated in spleen cell cultures. Results Sensitization with both soybean extracts induced high levels of antigen‐specific IgE and IgG1 and low levels of specific IgG2a. Both wt‐SE and gm‐SE were able to inhibit the binding of specific IgE from mice immunized with gm‐SE to the same antigen used for the ELISA coating. A comparable proliferative response was obtained with the homologous as well as with the heterologous extracts. Conclusion In sensitized mice, we observed a predominantly T‐helper type 2 (Th2)‐type immune response, with increased soybean‐specific IgE and IgG1 antibodies and a concomitant increase of IL‐4 and IL‐5 production. Results obtained by specific IgE ELISA inhibition and by antigen‐specific T cell proliferation demonstrated that wt‐SE and gm‐SE shared B and T epitopes. The present murine model of soybean sensitization established by the oral route should provide valuable information about risk assessment for food allergy from new proteins of genetically modified foods. 相似文献
133.
酱油卫生状况模糊评价模型的建立 总被引:3,自引:0,他引:3
目前酱油卫生状况采用单项的评价方法,存在着轻重不分等不科学因素。如食盐超标与大肠菌超标及重金属超标有着极大的差别。为了消除这种差别,根据模糊数学原理、建立M(·+)综合评价模型[1]对宁德地区1989年酱油抽查检验结果进行卫生学评价取得了满意结果,从而为酱油卫生综合评价建立了有效的评价模型。 相似文献
134.
Donald B. White Cynthia A. Walawander Dong Y. Liu Thaddeus H. Grasela 《Journal of pharmacokinetics and pharmacodynamics》1992,20(3):295-313
In a simulation study of inference on population pharmacokinetic parameters, two methods of performing tests of hypotheses comparing two populations using NONMEM were evaluated. These two methods are the test based upon 95% confidence intervals and the likelihood ratio test. Data were simulated according to a monoexponential model and, in that context, power curves for each test were generated for (i)the ratio of mean clearance and (ii)the ratio of the population standard deviations of clearance. To generate the power curves, a range of these parameters was employed; other pharmacokinetic parameters were selected to reflect the variability typically present in a Phase II clinical trial. For tests comparing the means, the confidence interval tests had approximately the same power as the likelihood ratio tests and were consistently more faithful to the nominal level of significance. For comparison of the standard deviations, and when the volume of information available was relatively small, however, the likelihood ratio test was more able to detect differences between the two groups. These results were then compared to results on parameter estimation in order to gain insight into the question of power. As an example, the nonnormality of estimates of the ratio of standard deviations plays an important role in explaining the low power for the confidence interval tests. We conclude that, except for the situation of modeling standard deviations with only sparse information, NONMEM produces tests of significance that are effective at detecting clinically significant differences between two populations.Partial support from the Upjohn Company, NIH-BRSG SO RR 07066, and the Burroughs Wellcome Foundation. 相似文献
135.
136.
影响妇女生育率的直接因素,如妇女已婚比、避孕及人工流产等的定量分析是卫生人口统计分析中的重要内容。本文应用美国人口学者Bongaarts提出的中介生育率变量模型就重庆城乡妇女生育率直接影响因素作一定量研究 相似文献
137.
Trang T. Duong Joanne St. Louis Joseph J. Gilbert Fred D. Finkelman Gill H. Strejan 《Journal of neuroimmunology》1992,36(2-3)
SJL/J mice challenged with myelin basic protein (MBP) in complete Freund's adjuvant (CFA) developed only mild chronic-relapsing experimental allergic encephalomyelitis (EAE) with very low incidence. However, treatment of challenged mice with anti-infeferonγ (IFN-γ) monoclonal antibody (mAb) determined severe disease in all cases. Similarly, in passive EAE, the addition of anti-IFN-γ to the in vitro MBP-activated cells at the time of transfer led to significant disease exacerbation in all recipients. The disease enhancing effect was observed only when the mAb was given at the time of active challenge or of passive transfer, but not at later times. Anti-interleukin-2 (IL-2) antibody had only a marginal effect in the active induction, but drastically reduced the manifestations of passive EAE, even when mixed with a disease-enhancing dose of anti-IFN-γ. These findings support the notion that IL-2 is required for disease induction whereas IFN-γ plays a disease-limiting role early in the development of EAE. 相似文献
138.
H. Oka T. Yamamoto T. Kawazoe K. Saratani Y. Hikida 《Medical & biological engineering & computing》1988,26(3):260-266
A new impact response method using a fracture of a pencil-lead to produce an excitation pulse is proposed. Impact excitations
(rectangular pulse, triangular pulse and half-sine pulse) are strictly given in physical and mathematical definitions and
complete solutions to the impact excitations are provided for Noyes' model of the human tooth. When a relatively long triangular
pulse is applied to Noyes' model, which can express the physical characteristic of periodontal tissues, a sinusoidal damped
vibration of a single degree-of-freedom model is approximately obtained. The acceleration response is characterised by the
physical parameters (T, δ and Ao) and mechanical elements (m1, c1 and k) of which a single degree-of-freedom model is composed. By means of this method, the values of the parameters and elements
in the cases of healthy maxillary, healthy mandibular and pathological mandibular incisors are obtained. The single degree-of-freedom
model can express the high-frequency spectra of Noyes' model. The pathological tooth is characterised by a longer damped time
constant and a larger acceleration maximum. This impact response method can effectively be applied to clinical diagnosis in
view of the physical parameters and mechanical elements which have been derived. 相似文献
139.
Laying the Cytotaxonomic Foundations of a New Model Grass, Brachypodium distachyon (L.) Beauv. 总被引:2,自引:0,他引:2
Brachypodium distachyon is a ubiquitous, temperate grass species which is being developed and exploited as an alternative model to rice, in order to gain access to important syntenic regions of the genomes of less tractable relatives such as wheat. As part of this initiative, this paper describes for the first time the cytotaxonomy of members of the polyploid series of this species, and challenges the assumption that the series evolved simply by chromosome doubling. In situ hybridization using genomic DNA probes and rDNA markers uncovers a hybrid origin of several of the polyploid ecotypes, and sheds light upon the complex evolution of this species and its close relatives. 相似文献
140.
Q. T. Dinh † D. A. Groneberg† C. Witt‡ C. Peiser† L. B. Cifuentes† N. Frossard§ B. F. Klapp A. Fischer† 《Clinical and experimental allergy》2004,34(12):1934-1941
BACKGROUND: The traditional neurotransmitter catecholamine and the neuropeptide tyrosine in sympathetic airway nerves have been proposed to be involved in the pathogenesis of airway diseases. OBJECTIVE: The aim of the present study was to investigate the effect of allergic airway inflammation on the expression of catecholamine enzyme tyrosine hydroxylase (TH), neuropeptide tyrosine (NPY) and tachykinins in mouse sympathetic airway ganglia. METHODS: Using neuronal tracing in combination with immunohistochemistry, the present study was designed to characterize TH, NPY and tachykinin profiles of superior cervical (SCG) and stellate ganglia after allergen challenge. RESULTS: The vast majority of fast blue-labelled SCG neurons (allergen: 97.5+/-1.22% (mean+/-SEM) vs. controls: 94.5+/-1.48%, P=0.18) and stellate neurons (allergen: 95.3+/-1.01% vs. controls: 93.6+/-1.33%, P=0.34) were immunoreactive for TH. Of the TH immunoreactive and fast blue-labelled SCG neurons, 52.0+/-1.01% allergen vs. 51.2+/-3.58% controls (P=0.83) and stellate neurons, 57.3%+/-0.97 allergen vs. 56.4+/-1.65% controls (P=0.64) were positive for TH only but not NPY, whereas 45.3+/-1.05% allergen vs. 43.3+/-1.18% controls (P=0.47) of fast blue-labelled SCG neurons and 37.9+/-0.86% allergen vs. 37.1+/-1.24% controls (P=0.62) of fast blue-labelled stellate neurons were immunoreactive for both TH and NPY immunoreactivities. There was a trend of an increase, but not significant one, in the percentage of TH-/NPY-immunoreactive and fast blue-labelled neurons in allergen-treated animals in comparison with the controls. Tachykinins, however, were not expressed by sympathetic neurons and were also not induced in sympathetic neurons after allergen challenge. CONCLUSION: The present study indicates that allergic airway inflammation does not alter the expression of noradrenalin and NPY in sympathetic ganglia and also shows that sympathetic neurons do not respond to allergic airway inflammation with tachykinins induction. However, a participation of catecholamine and NPY in the pathogenesis of allergic airway inflammation cannot be excluded in the present study as a higher neurotransmitter output per neuron following allergen challenge could be possible. 相似文献