全文获取类型
收费全文 | 86040篇 |
免费 | 6478篇 |
国内免费 | 5275篇 |
专业分类
耳鼻咽喉 | 634篇 |
儿科学 | 2477篇 |
妇产科学 | 1157篇 |
基础医学 | 16030篇 |
口腔科学 | 2150篇 |
临床医学 | 7745篇 |
内科学 | 13467篇 |
皮肤病学 | 1918篇 |
神经病学 | 5265篇 |
特种医学 | 1750篇 |
外国民族医学 | 32篇 |
外科学 | 4609篇 |
综合类 | 16558篇 |
现状与发展 | 25篇 |
一般理论 | 1篇 |
预防医学 | 5016篇 |
眼科学 | 1956篇 |
药学 | 6253篇 |
13篇 | |
中国医学 | 1857篇 |
肿瘤学 | 8880篇 |
出版年
2024年 | 120篇 |
2023年 | 928篇 |
2022年 | 1421篇 |
2021年 | 2631篇 |
2020年 | 2319篇 |
2019年 | 2214篇 |
2018年 | 2070篇 |
2017年 | 2281篇 |
2016年 | 2481篇 |
2015年 | 2618篇 |
2014年 | 4200篇 |
2013年 | 5347篇 |
2012年 | 4464篇 |
2011年 | 5444篇 |
2010年 | 4460篇 |
2009年 | 4521篇 |
2008年 | 4889篇 |
2007年 | 5358篇 |
2006年 | 4989篇 |
2005年 | 4804篇 |
2004年 | 4326篇 |
2003年 | 3864篇 |
2002年 | 3361篇 |
2001年 | 3039篇 |
2000年 | 2663篇 |
1999年 | 2302篇 |
1998年 | 2061篇 |
1997年 | 1690篇 |
1996年 | 1312篇 |
1995年 | 1238篇 |
1994年 | 976篇 |
1993年 | 668篇 |
1992年 | 520篇 |
1991年 | 399篇 |
1990年 | 316篇 |
1989年 | 212篇 |
1988年 | 171篇 |
1987年 | 129篇 |
1986年 | 111篇 |
1985年 | 188篇 |
1984年 | 145篇 |
1983年 | 88篇 |
1982年 | 125篇 |
1981年 | 89篇 |
1980年 | 66篇 |
1979年 | 45篇 |
1978年 | 43篇 |
1977年 | 25篇 |
1976年 | 22篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
用血清学方法研究显示中国人胰岛素依赖性糖尿病(IDDM)与HLA-DR9相关。鉴于白种人中的研究显示IDDM与HLA-DQβ链第57位氨基酸相关,Asp-57对IDDM呈抗性,non-Asp与IDDM易感性相关。我们用PCR技术扩增了中国人中血清学DR9纯合的IDDM患者和正常对照的HLA-DQB1基因第二外显子并测定了核苷酸顺序,结果未发现IDDM特异HLA-DQB1等位基因,但发现IDDM病人HLA-DQB157位均为天冬氨酸。表明中国IDDM患者中的HLA-DQB157位天冬氨酸不一定具有保护个体抵抗IDDM的足够能力。IDDM易感性可能涉及多个基因位点的变化,另外还可能与其它遗传因素及环境因素有关。 相似文献
992.
993.
H1N2新亚型流感病毒神经氨酸酶基因来源的进一步研究 总被引:1,自引:0,他引:1
对流感病毒H1N2亚型重组株A/哈防/1/88、A/哈防/12/92以及H3N2亚型病毒株A/雅防/2/87、A/京防/57/898和A/粤防/1/92神经氨酸酶(NA)基因核苷酸全序列的测定,进一步弄清了A/哈防/1/88病毒株的NA基因确来自当时人群中流行的H3N2亚型病毒株,很可能是来自A/雅防/2/87类病毒株;而A/哈防/12/92病毒株的NA基因可能是与A/哈防/1/88病毒株的NA基 相似文献
994.
N. Drakoulis I. Cascorbi J. Brockmöller C. R. Gross I. Roots 《Journal of molecular medicine (Berlin, Germany)》1994,72(3):240-248
Genetic differences in the metabolism of carcinogens may codetermine individual predisposition to cancer. Cytochrome P-4501A1 (CYP1A1) metabolically activates precarcinogens in cigarette smoke, such as benzo(a)pyrene, which is also an inducer of CYP1A1. Two point mutations have been reported, m1 in the 3-flanking region (6235T to C), and m2 within exon 7 (4889A to G), the latter leading to an isoleucine to valine exchange. In the Japanese population ml and m2 are correlated with lung cancer, suggesting an increased susceptibility to cigarette smoking related lung cancer. We studied 142 lung cancer and 171 reference patients in an ethnically homogeneous German group for m1 and m2 mutations by restriction fragment length polymorphism and allele-specific polymerase chain reaction, respectively. No statistically significant difference was found in the distribution of m1 alleles between lung cancer and controls; the frequency was 8.5% and 7.3% of the alleles, respectively (odds ratio = 1.17). A trend to an overrepresentation of ml alleles was observed among 52 squamous cell carcinoma patients (odds ratio = 1.65). In contrast, the frequency of m2 alleles in lung cancer patients was twofold higher (6.7%) than in the reference group (3.2%; odds ratio = 2.16; 95% confidence limits 0.96–5.11, P = 0.033); the odds ratio of m2 alleles in squamous cell carcinoma was 2.51 (95% confidence limits 0.85–7.05, P = 0.05). There was a close genetic linkage of m2 to m1 (10 of 11 reference patients), but a significantly higher number of cancer patients showed no linkage compared to the controls (odds ratio = 8.89, 95% confidence limits 0.83–433, P = 0.04). Thus no association was found between presence of ml alleles and lung cancer, but, in contrast, m2 alleles proved as a hereditary risk factor, especially if not linked with m1 alleles.Abbreviations Ah
aryl hydrocarbon
- CYP1A1
cytochrome P4501A1
-
CYP1A1
CYP1A1 gene
- PCR
polymerase chain reaction
- PY
pack years
- RFLP
restriction fragment length polymorphism
Correspondence to: N. Drakoulis 相似文献
995.
L. D. Luk'yanova G. N. Chernobaeva V. E. Romanova 《Bulletin of experimental biology and medicine》1989,107(4):482-484
Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. V. Val'dman.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 107, No. 4, pp. 431–433, April, 1989. 相似文献
996.
以基因表达谱芯片对Ty2 1a免疫前后小鼠肠细胞 (包括肠粘膜上皮细胞和肠上皮间淋巴细胞 )基因表达的差异性进行研究比较。将 490条经抑制消减杂交法筛选出的与小鼠Ty2 1a免疫相关的cDNA制备成表达谱芯片 ;利用免疫前后小鼠肠细胞的mRNA通过逆转录方法 ,将Cy3和Cy5两种荧光分别标记到两种组织的cDNA上 ,制备成cDNA探针 ,并与表达谱芯片进行杂交及扫描 ,单点重复 2次实验 ,通过计算机数据处理判定基因是否在上述两种细胞群中有表达差异。筛选出差异表达基因共 98条 ,其中 92条为表达上调基因 ,6条为表达降低基因。提示 ,基因表达谱芯片技术是高通量进行基因表达模式研究的方法 ,可同时定量研究大量的基因表达水平 ,从而鉴定可能参与免疫的基因。 相似文献
997.
新城疫病毒pIRHN核酸疫苗构建和表达及对肿瘤细胞的影响 总被引:6,自引:0,他引:6
目的:研究NDV HN基因抗肿瘤作用及其可能机制。方法:以 pIRES1neo为表达载体构建了 NDV HN基因的pIRHN核酸疫苗,在体外转染HeLa细胞,用间接免疫荧光和Western blot检测pIRHN在真核细胞中表达状况,用荧光显微镜、DNA琼脂糖电泳及TUNEL染色等方法,检测HN基因导致细胞死亡的类型;用3,5-二羟基甲苯法测定HeLa细胞唾液酸含量的变化。结果:pIRHN 转染HeLa细胞后,能够在真核细胞中表达,能促进肿瘤细胞死亡,其死亡方式主要以诱导细胞凋亡为主,pIRHN使 HeLa细胞唾液酸含量减少。结论:用 NDV HN基因所构建的核酸疫苗能够在真核细胞中高效表达,表达的 HN蛋白主要位于胞膜,胞浆中亦有 HN蛋白表达;pIRHN具有抗肿瘤作用,可能通过其表达产物与肿瘤细胞唾液酸受体的相互作用,发挥其抗肿瘤作用。本实验为迸一步阐明NDV抗肿瘤作用机制提供了理论依据。 相似文献
998.
An association of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphism and common carotid atherosclerosis 总被引:3,自引:0,他引:3
Kawamoto R Kohara K Tabara Y Miki T Doi T Tokunaga H Konishi I 《Journal of human genetics》2001,46(9):506-510
Plasma homocysteine (Hcy) concentration has been shown to be influenced by a mutation in the gene coding methylenetetrahydrofolate
reductase (MTHFR). Although plasma Hcy is related to atherosclerotic disorders, conflicting results have been reported about
the association between MTHFR gene polymorphism and sclerotic lesions of the common carotid arteries. The effect of age–gene interaction on carotid arterial
remodeling was investigated in elderly subjects with several risk factors for atherosclerosis. We evaluated sclerotic lesions
of the common carotid arteries by ultrasonography in 326 patients (mean age ± standard deviation, 73 ± 12 years) and studied
relations among the known risk factors for atherosclerosis, including MTHFR gene polymorphism and its interactions with age and sex. Of the 326 subjects studied, 136 had MTHFR genotype CC, 136 genotype CT, and 54 genotype TT. The three groups did not differ with respect to background factors such as age, history of cigarette smoking, blood pressure,
lipids or uric acid, or in the incidence of atherosclerotic diseases. Spearman's rank correlation revealed a significant relationship
between gender, age, Brinkman index, systolic blood pressure, triglycerides, HDL-cholesterol (HDL-C), uric acid, and MTHFR gene polymorphism. Multiple regression analysis using intima-media complex thickness (IMT) as a criterion variable and risk
factors, including MTHFR gene polymorphism as explanatory variables showed that MTHFR gene polymorphism (P = 0.039) was a significant independent explanatory variable for IMT, along with gender (male) (P < 0.001), age (P < 0.001), systolic blood pressure (SBP) (P = 0.047), total cholesterol (T-C) (P < 0.001), and HDL-C (P < 0.001). Furthermore, a general linear model analysis revealed that interaction between age and MTHFR gene polymorphism was significantly associated with IMT, independently of age, SBP, T-C, and HDL-C in male subjects. However,
age–gene interaction was not observed in female subjects. The findings of the present study confirm an association between
MTHFR gene polymorphism and common carotid atherosclerosis in the Japanese population and further support the role of risk factor–gene
interaction in common carotid atherosclerosis.
Received: May 14, 2001 / Accepted: June 8, 2001 相似文献
999.
Etokebe GE Opsahl M Tveter AK Lie BA Thorsby E Vartdal F Spurkland A 《Tissue antigens》2003,61(6):443-450
Genomic typing of polymorphic loci may be hampered by ambiguous typing results. Moreover, robust methods for simultaneous sequencing of two alleles present in a given sample may be difficult to establish. We used denaturing high-performance liquid chromatography (DHPLC) for physical separation of HLA-A alleles before sequence-based genomic typing (SBT). Physical separation was achieved by resolution of heteroduplexes between the sample alleles and a modified reference probe by DHPLC followed by selective reamplification of the sample alleles present in heteroduplexes. Complementary strands of the reference probe and sample alleles for heteroduplex induction were obtained by lambda-exonuclease digestion. HLA-A genotyping of 101 individuals using DHPLC-SBT yielded better typing resolution compared with serological typing and genotyping by the sequence-specific primer-polymerase chain reaction (SSP-PCR) method. Physical separation of alleles using a modified reference probe allows for development of fully automated methods for genomic typing of highly polymorphic loci such as HLA. 相似文献
1000.