全文获取类型
收费全文 | 11503篇 |
免费 | 1449篇 |
国内免费 | 257篇 |
专业分类
耳鼻咽喉 | 59篇 |
儿科学 | 183篇 |
妇产科学 | 124篇 |
基础医学 | 1446篇 |
口腔科学 | 256篇 |
临床医学 | 979篇 |
内科学 | 2054篇 |
皮肤病学 | 136篇 |
神经病学 | 716篇 |
特种医学 | 263篇 |
外国民族医学 | 2篇 |
外科学 | 559篇 |
综合类 | 1200篇 |
一般理论 | 3篇 |
预防医学 | 3051篇 |
眼科学 | 185篇 |
药学 | 1162篇 |
4篇 | |
中国医学 | 196篇 |
肿瘤学 | 631篇 |
出版年
2024年 | 12篇 |
2023年 | 229篇 |
2022年 | 231篇 |
2021年 | 517篇 |
2020年 | 484篇 |
2019年 | 467篇 |
2018年 | 412篇 |
2017年 | 472篇 |
2016年 | 445篇 |
2015年 | 542篇 |
2014年 | 786篇 |
2013年 | 977篇 |
2012年 | 762篇 |
2011年 | 818篇 |
2010年 | 641篇 |
2009年 | 615篇 |
2008年 | 611篇 |
2007年 | 660篇 |
2006年 | 537篇 |
2005年 | 410篇 |
2004年 | 383篇 |
2003年 | 288篇 |
2002年 | 261篇 |
2001年 | 256篇 |
2000年 | 189篇 |
1999年 | 153篇 |
1998年 | 140篇 |
1997年 | 127篇 |
1996年 | 110篇 |
1995年 | 88篇 |
1994年 | 76篇 |
1993年 | 66篇 |
1992年 | 70篇 |
1991年 | 59篇 |
1990年 | 38篇 |
1989年 | 30篇 |
1988年 | 39篇 |
1987年 | 25篇 |
1986年 | 26篇 |
1985年 | 33篇 |
1984年 | 18篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 13篇 |
1976年 | 3篇 |
1969年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Reciprocal effects of apolipoprotein E alleles (ε2 AND ε4) on plasma lipid levels in normolipidemic subjects 总被引:2,自引:0,他引:2
A significantly lower frequency of the epsilon 2 allele and a significantly higher frequency of the epsilon 3 allele were found in the normolipidemic Japanese population than those in the normolipidemic Caucasian populations. We have compared plasma lipid variables among the apolipoprotein (apo) E phenotype groups and estimated the average effects of the three common alleles (epsilon 2, epsilon 3 and epsilon 4) on plasma lipid levels in normolipidemic subjects. Plasma triglyceride (TG), very low density lipoprotein (VLDL)-TG, VLDL-cholesterol (C) and apo E levels were high in the apo E3/2 group, intermediate in the apo E3/3 group and low in the apo E4/3 group, whereas plasma total cholesterol (TC), low density lipoprotein (LDL)-C and high density lipoprotein (HDL)-C levels were low in the apo E3/2 group, intermediate in the apo E3/3 group and high in the apo E4/3 group. Furthermore, the epsilon 2 allele had an effect to increase the TG, VLDL-TG, VLDL-C and apo E levels and decrease the TC, LDL-C and HDL-C levels, whereas the epsilon 4 allele had an effect opposite to the epsilon 2 allele. These results indicate that the epsilon 2 and epsilon 4 alleles have the reciprocal effects on plasma lipid, lipoprotein and apo E levels. 相似文献
92.
93.
用分子克隆技术构建D12S391基因座等位基因分型标准物及群体遗传学研究 总被引:9,自引:1,他引:9
目的 解决长期困扰短串联重复序列(short tandem repeat,STR)分型上存在的准确性和标准化问题。方法 先用PCR扩增出D12S391基因座的9个等位基因片段,将其插入pUC重组质粒中,经DNA测序分析证实插入片段的结构及大小,用国际标准将插入的等位基因片段进行命名,最后经转染、扩大培养、扩增及再鉴定后,制备出标准的D12S391等位基因分型标准物。结果 应用此法制备出大量的D12S391基因座等位基因分型标准物,并将其用于调查该基因座在德国Mainz地区、日本Miyazaki地区及中国成都汉族、北京汉族、新疆维吾尔族和甘肃回族6个群体中的基因型分布频率。D12S391基因座在各群体中均有较高的多态性,其非父排除概念及个人识别能力分别为0.609-0.786和0.940-0.952。结论 该法制备的STR基因座等位基因分型标准物在法医科学实践中应用价值极高,D12S391基因座是一个非常适合于群体遗传学研究和法医科学应用的遗传标记。 相似文献
94.
Stature estimation based on hand length and foot length 总被引:1,自引:0,他引:1
Sanli SG Kizilkanat ED Boyan N Ozsahin ET Bozkir MG Soames R Erol H Oguz O 《Clinical anatomy (New York, N.Y.)》2005,18(8):589-596
This study was carried out to estimate the relationship between hand length, foot length and stature using multiple linear regression analyses based on a sample of male and female adult Turks residing in Adana. Measurements of hand length, foot length and stature were taken from 155 adult Turks (80 male, 75 female) aged 17-23 years. The participants were students of the Medical Faculty of Cukurova University. A multiple linear regression model was fitted to the observed data. Stature was taken as the response or dependent variable, hand length and foot length were taken as explanatory variables or regressors. All possible (simple and multiple) linear regression models for each of males, females and both genders together were tested for the best model. The multiple linear regression model for both genders together was found to be the best model with the highest values for the coefficients of determination R2 = 0.861 and R2adjusted = 0.859, and multiple correlation coefficient R = 0.928. 相似文献
95.
Lisa M. Nakamura Barry Eng Forbes D. Porter John S. Waye 《American journal of medical genetics. Part A》2001,102(4):383-386
Smith‐Lemli‐Opitz syndrome (SLOS) is an inherited multiple malformation syndrome caused by enzymatic deficiency of 3β‐hydroxysterol‐Δ7‐reductase (DHCR7). SLOS is thought to be most common among European Caucasians, with an incidence of 1 in 20,000 to 1 in 30,000 births. To define the carrier rate and ethnic distribution of SLOS, we screened DNA samples from 2,978 unrelated individuals for the most common SLOS mutation (IVS8‐1G→C). Twenty‐four heterozygotes of the IVS8‐1G→C mutation were detected in 2,978 individuals of European Caucasian and Black backgrounds. For European Caucasians, the carrier rate for SLOS may be as high as 1 in 30, suggesting an incidence of 1 in 1,700 to 1 in 13,400. This high number is supported by the recent observation of newborn and prenatal incidence of 1 in 22,000 in the Caucasian population. Ours is the first report of the IVS8‐1G→C mutation in persons of African ancestry. Published 2001 Wiley‐Liss, Inc. 相似文献
96.
Advances in sequencing and genotyping technologies over the last decade have enabled geneticists to easily characterize genetic variation at the nucleotide level. Hundreds of genes harboring mutations associated with genetic disease have now been identified by positional cloning. Using variation at closely linked genetic markers, it is possible to predict the times in the past at which particular mutations arose. Such studies suggest that many of the rare mutations underlying human genetic disorders are relatively young. Studies of variation at genetic markers linked to particular mutations can provide insights into human geographic history, and historical patterns of natural selection and disease, that are not available from other sources. We review two approaches for estimating allele age using variation at linked genetic markers. A phylogenetic approach aims to reconstruct the gene tree underlying a sample of chromosomes carrying a particular mutation, obtaining a “direct” estimate of allele age from the age of the root of this tree. A population genetic approach relies on models of demography, mutation, and/or recombination to estimate allele age without explicitly reconstructing the gene tree. Phylogenetic methods are best suited for studies of ancient mutations, while population genetic methods are better suited for studies of recent mutations. Methods that rely on recombination to infer the ages of alleles can be fine‐tuned by choosing linked markers at optimal map distances to maximize the information available about allele age. A limitation of methods that rely on recombination is the frequent lack of a fine‐scale linkage map. Maximum likelihood and Bayesian methods for estimating allele age that rely on intensive numerical computation are described, as well as “composite” likelihood and moment‐based methods that lead to simple estimators. The former provide more accurate estimates (particularly for large samples of chromosomes) and should be employed if computationally practical. Hum Mutat 18:87–100, 2001. © 2001 Wiley‐Liss, Inc. 相似文献
97.
青岛地区D6S477等五个短串联重复序列基因座的遗传多态性研究 总被引:3,自引:0,他引:3
目的 了解D6S477等5个基因座在青岛地区汉族群体中基因型分布及等位基因频率等遗传多态性数据,初步探讨其应用价值。方法 收集200名青岛地区汉族无关个体的静脉血,ACD抗凝,采用Chelex法提取DNA,应用聚合酶链反应技术,扩增D6S477、D9S1118、D18S865、D19S400和D20S161基因座的短串联重复序列,聚丙烯酰胺凝胶垂直电泳,银染显色分型。结果 获得了青岛地区汉族群体上述5个基因座的等位基因频率,基因型分布均符合Hardy-Weinberg平衡(P〉0.05)。结论 这5个基因座在青岛地区汉族群体中有较高的非父排除率和个人识别机率,在遗传学研究中有较高的应用价值。 相似文献
98.
L. E. Pospelov A. G. Matrakshin L. S. Erdynieva A. F. Malenko K. I. Afanasiev G. A. Rubtsova I. K. Egorov V. V. Yeremeyev A. S. Apt 《Tissue antigens》1997,49(6):629-634
Todja is a secluded region of northern Tuva situated in the Sayany Mountains, Siberia. The aboriginal population of Todja is Tuvan. A total of 128 healthy Tuvans living in Todja were typed for HLA-A, -B and -C antigens and several plasma and erythrocyte protein polymorphisms (Hp, Tf, Gc, ESD, ACP, PGM1, PGD and ADA). The observed frequencies of all 8 blood protein and HLA genotypes were in agreement with Hardy-Weinberg expectations. The most frequent HLA antigens in Todjans are A2 (0.36). A3 (0,24), A9 (0.50), B15 (0.34) and B40 (0.50). HLA haplotypes A2B5, A2B40, A9B15 and A9B40 are most common in this population. The observed frequencies of protein polymorphisms and HLA antigens and haplotypes in Todjans are similar to those of other Mongoloid populations. A comparison of HLA frequencies currently observed in Todjans with those obtained 20 years ago at the same locality showed minor changes attributable to the effect of migration. 相似文献
99.
The objective was to evaluate a postal questionnaire screening procedure for selection of subjects with positive reactions to skin prick tests with common allergens. The project consisted of a screening, with subsequent skin prick test of two selected groups. The setting was the Glostrup Population Studies institute in Copenhagen, Denmark. Participants in the screening included 8000 subjects, aged 15–69 years. The subjects were randomly selected from the population of western Copenhagen County, Denmark. From the 6998 respondents (87.5%), 793 subjects were randomly selected (Random Group), and 788 subjects were chosen on the basis of their answers to the questionnaire (Symptom Group). Both groups were invited to take skin prick tests. Attendance rates were 75.5% (Random Group) and 80.6% (Symptom Group).
The main outcome measures were responses (yes or no) to the specific questions and the subjects' skin reaction (positive or negative). The association between symptoms and skin reactivity, adjusted for the effects of sex and age, was summarized by odds ratios. Symptoms on exposure to allergens were highly associated with positive skin reactivity. In the Symptom Group the percentage of subjects with at least one positive skin reaction was 57.7%, which was twice as much (28.4%) as in the Random Group. The results show that it was possible to select a group with high skin reactivity on the basis of the symptoms reported in the screening. Questions about exposure to allergens were the most appropriate for selection of this group. 相似文献
The main outcome measures were responses (yes or no) to the specific questions and the subjects' skin reaction (positive or negative). The association between symptoms and skin reactivity, adjusted for the effects of sex and age, was summarized by odds ratios. Symptoms on exposure to allergens were highly associated with positive skin reactivity. In the Symptom Group the percentage of subjects with at least one positive skin reaction was 57.7%, which was twice as much (28.4%) as in the Random Group. The results show that it was possible to select a group with high skin reactivity on the basis of the symptoms reported in the screening. Questions about exposure to allergens were the most appropriate for selection of this group. 相似文献
100.
我国福建汉族人HSP70基因多态性分析 总被引:1,自引:0,他引:1
目的了解福建省汉族人HSP70基因多态性分布,进而为探讨HSP70基因多态性与疾病的相关性提供遗传背景资料。方法应用聚合酶链反应技术、限制性内切酶分析检测了127名福建汉族正常人的HSP70基因3个多态性位点,并比较了部分不同地区和人群之间的基因型与等位基因频率。结果福建汉族人HSP70-1基因型(GG,GC和CC)分布频率分别是55.1%、40.2%和4.7%;HSP70-2基因型(从,AG和GG)分布频率分别是44.1%、铝.8%和6.9%;HSP70-hom基因型(Tr,TC和CC)分布频率分别是59.8%、37.0%和3.2%;HSP70-1等位基因频率G和C分别是75.2%和24.8%;HSP70-2等位基因频率A和G分别是68.5%和31.5%;HSP70-hom等位基因频率T和C分别是78.3%和21.7%。福建汉族人HSP70-1的基因型分布和等位基因频率同日本、墨西哥人群比较差异无统计学意义,与美国和西班牙人比较,差异有统计学意义(P〈0.01)。福建汉族人HSP70-1的GG纯合型(55.1%)显著高于美国(42.6%)和西班牙(33.0%)人群;福建汉族人HSP70-2的基因型分布和等位基因频率与日本人比较差异无统计学意义,与墨西哥、美国和西班牙人群比较,差异有统计学意义(P〈0.05),福建汉族人HSP70-2的AA纯合型(44.1%)高于墨西哥(23.O%)、美国(38.8%)和西班牙(20.O%)人群;福建汉族人群的HSP70-hom基因型和等位基因频率分布同日本、墨西哥、美国和西班牙人群的基本一致,差异无统计学意义,福建汉族人群的HSP70基因型和等位基因频率分布同中国台湾汉族人基本一致,差异无统计学意义,与武汉地区汉族人某些位点存在差异。结论福建汉族人HSP70基因多态性分布不同于某些地区的人群,具有种族和地区差异。 相似文献