全文获取类型
收费全文 | 3018篇 |
免费 | 134篇 |
国内免费 | 53篇 |
专业分类
耳鼻咽喉 | 21篇 |
儿科学 | 93篇 |
妇产科学 | 72篇 |
基础医学 | 302篇 |
口腔科学 | 52篇 |
临床医学 | 334篇 |
内科学 | 540篇 |
皮肤病学 | 50篇 |
神经病学 | 167篇 |
特种医学 | 266篇 |
外科学 | 255篇 |
综合类 | 310篇 |
预防医学 | 233篇 |
眼科学 | 55篇 |
药学 | 275篇 |
3篇 | |
中国医学 | 101篇 |
肿瘤学 | 76篇 |
出版年
2023年 | 16篇 |
2022年 | 28篇 |
2021年 | 45篇 |
2020年 | 45篇 |
2019年 | 27篇 |
2018年 | 30篇 |
2017年 | 42篇 |
2016年 | 32篇 |
2015年 | 51篇 |
2014年 | 74篇 |
2013年 | 95篇 |
2012年 | 154篇 |
2011年 | 140篇 |
2010年 | 120篇 |
2009年 | 120篇 |
2008年 | 170篇 |
2007年 | 181篇 |
2006年 | 156篇 |
2005年 | 128篇 |
2004年 | 86篇 |
2003年 | 60篇 |
2002年 | 72篇 |
2001年 | 75篇 |
2000年 | 58篇 |
1999年 | 56篇 |
1998年 | 40篇 |
1997年 | 55篇 |
1996年 | 61篇 |
1995年 | 43篇 |
1994年 | 52篇 |
1993年 | 34篇 |
1992年 | 20篇 |
1991年 | 23篇 |
1990年 | 38篇 |
1989年 | 29篇 |
1988年 | 33篇 |
1987年 | 36篇 |
1986年 | 19篇 |
1985年 | 35篇 |
1984年 | 32篇 |
1983年 | 18篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1977年 | 16篇 |
1959年 | 41篇 |
1958年 | 66篇 |
1957年 | 75篇 |
1956年 | 73篇 |
1955年 | 83篇 |
1954年 | 51篇 |
排序方式: 共有3205条查询结果,搜索用时 31 毫秒
41.
LOUISE POTVIN PhD SERGE DESROSIERS MSc MARY TRIFONOPOULOS MSc PDt NICOLE LEDUC PhD MICHLE RIVARD ScD ANN C. MACAULAY MD GILLES PARADIS MD MSc FRCPC 《Journal of the American Dietetic Association》1999,99(8):955-961
OBJECTIVE: Recent studies have concluded that Native North American children have higher proportions of overweight and obesity than children from the general North American population. This study presents anthropometric data on a representative sample of children from the Mohawk Nation that can be used for comparison with other Native American populations. DESIGN: This is a cross-sectional study comparing distributions of anthropometric characteristics of Mohawk children to the corresponding age and gender data from the Second National Health and Nutrition Examination Survey (NHANES II). Weight, height, triceps and subscapular skinfold thickness, and waist and hip circumferences were measured in 527 children. SUBJECTS/SETTING: All children in grades 1 to 6 (aged 6 to 11 years) in the 3 elementary schools of 2 Mohawk communities in Canada, for whom parental consent was obtained, were enrolled in the present study. There were no exclusion criteria. With a participation rate of 83%, the 527 children enrolled in this study represent an unbiased sample of the population from 2 Mohawk territories. RESULTS: Compared with children studied in NHANES II, Mohawk children were similar in height and triceps skinfolds but were generally heavier, had thicker subscapular skinfolds, and had greater waist and hip circumferences. These differences were greater in older children. Mohawk children who had extreme-high weight values compared with their population means were heavier than their NHANES II counterparts. APPLICATIONS/CONCLUSIONS: Results indicated that, on average, Mohawk children seem to be slightly heavier than children in NHANES II. Except for those with extreme overweight values, Mohawk children show less variation of weight and body mass index than children in NHANES II. Finally, overweight Mohawk children seem to be more likely to carry their excess body fat truncally, compared with overweight children from NHANES II. Health practitioners working with Native American populations should be careful when assessing childhood obesity. Simple comparisons of weight or body mass index with NHANES standards may lead to inappropriate risk assessments. 相似文献
42.
Deckert J Catalano M Syagailo YV Bosi M Okladnova O Di Bella D Nöthen MM Maffei P Franke P Fritze J Maier W Propping P Beckmann H Bellodi L Lesch KP 《Human molecular genetics》1999,8(4):621-624
A genetic contribution to the pathogenesis of panic disorder has been demonstrated by clinical genetic studies. Molecular genetic studies have focused on candidate genes suggested by the molecular mechanisms implied in the action of drugs utilized for therapy or in challenge tests. One class of drugs effective in the treatment of panic disorder is represented by monoamine oxidase A inhibitors. Therefore, the monoamine oxidase A gene on chromosome X is a prime candidate gene. In the present study we investigated a novel repeat polymorphism in the promoter of the monoamine oxidase A gene for association with panic disorder in two independent samples (German sample, n = 80; Italian sample, n = 129). Two alleles (3 and 4 repeats) were most common and constituted >97% of the observed alleles. Functional characterization in a luciferase assay demonstrated that the longer alleles (3a, 4 and 5) were more active than allele 3. Among females of both the German and the Italian samples of panic disorder patients (combined, n = 209) the longer alleles (3a, 4 and 5) were significantly more frequent than among females of the corresponding control samples (combined, n = 190, chi2 = 10.27, df = 1, P = 0.001). Together with the observation that inhibition of monoamine oxidase A is clinically effective in the treatment of panic disorder these findings suggest that increased monoamine oxidase A activity is a risk factor for panic disorder in female patients. 相似文献
43.
Battaglia M Fossati A Torgersen S Bertella S Bajo S Maffei C Bellodi L Smeraldi E 《Schizophrenia Research》1999,37(1):53-64
This study aimed to clarify the structure and the etiological constituents of schizotypal disorder (SPD) by directly interviewing pairs of twins. A latent class analysis was applied to each individual's outcome for specified SPD items, such that each subject's phenotype could be redefined in terms of individual probabilities of class membership. Intraclass correlations were then calculated for each twin pair, and a standard univariate twin model applied. The best latent class analysis solution encompassed a model with four latent classes (three latent classes of SPD subjects, one of non-SPD). The intraclass correlations revealed a moderate to high heritability for two out of three SPD classes and for the modal class (a class composed of subjects that possessed a conditional probability of belonging to any of the SPD classes). Model fittings revealed considerable variation in the extent to which the different classes of SPD were influenced by additive genetic constituents or non-genetic factors. Although these data confirm the importance of genetic contributors in determining liability to SPD and the schizophrenia spectrum, they indicate that there is a relationship between psychometric multidimensionality and etiological heterogeneity in SPD. 相似文献
44.
45.
高效液相色谱法测定绿茶和饮料中的咖啡因 总被引:5,自引:0,他引:5
采用反相高效液相色谱法,固定相为十八烷基硅烷键合硅胶,以乙腈-水(20:80)为流动相,检测波长274nm,测定绿茶和饮料中的咖啡因含量。结果线性范围为3.9~3900ng,r=O.9999;绿茶和2种饮料的平均加样回收率分别为100.2%、100.1%和99.8%。该方法准确、简便、快速,适合绿茶和可乐型饮料中咖啡因的测定。 相似文献
46.
47.
Abstract: Haemoptysis in otherwise healthy children is an uncommon event. Two cases of massive haemoptysis, subsequently requiring lobectomy, are discussed. In each case, foreign vegetable matter was identified despite previously normal bronchoscopy and minimal changes on chest radiograph. 相似文献
48.
OBJECTIVE: Because survival from admission to discharge does not provide parents and physicians information about future life expectancy in the premature neonate, we characterized the actuarial survival, defined as the future life expectancy from a given postnatal age, in a large inborn population of premature infants < 30 weeks' gestation. STUDY DESIGN: We determined daily actuarial survival of 1925 inborn infants (23 to 29 weeks' gestation) admitted to the Baylor Affiliated Nurseries from July 1986 through December 1994, stratified by 100-g birth weight and by 1-week gestational-age intervals. RESULTS: In the 501- to 600-g birth weight stratum, actuarial survival improved from 31% at birth, to 61% on day of life 7, and then to 75% on day of life 28; in the 901- to 1000-g birth weight stratum, actuarial survival improved from 88%, to 94%, and then to 98% throughout the same times, respectively. Similar trends were obtained when data were stratified by gestational age. CONCLUSIONS: Survival in the smallest infants improves dramatically during the first few days of life, but there is a significant risk for late death in the smallest of these infants. 相似文献
49.
外源核苷酸对免疫抑制小鼠胸腺细胞DNA损伤的影响 总被引:5,自引:0,他引:5
目的:检测外源核苷酸对经环磷酰胺诱导的免疫抑制小鼠胸腺细胞DNA损伤的影响。方法:采用18~20 g昆明种小鼠30只,雌雄各半,随机分成阴性对照组(NEC)、阳性对照组(POC)和核苷酸组(NTG),每组10只。NEC组和POC组小鼠均饲喂半纯合无核苷酸的基础日粮,NTG组则在基础日粮中添加0.25%的核苷酸,实验期为21 d。在实验结束前18 h POC组和NTG组小鼠按照150mg/kg bw的剂量腹腔注射环磷酰胺,NEC组注射生理盐水,实验结束时测定脾脏和胸腺脏器指数,并取胸腺细胞,做单细胞凝胶电泳,观察细胞DNA损伤情况。结果:在基础日粮中添加核苷酸对小鼠免疫器官重量没有显著影响(P>0.05),但能极显著降低受损胸腺细胞百分率(P<0.01)和受损细胞DNA尾长(P<0.01)。结论:外源核苷酸能显著降低免疫抑制小鼠受损胸腺细胞百分率和损伤程度。 相似文献
50.
自然流产妇女弓形虫感染的调查研究 总被引:2,自引:0,他引:2
目的 探讨自然流产妇女与弓形虫 (Tox)感染的相关性。方法 采用酶联免疫吸附试验(EL ISA)对自然流产的 4 76例孕妇外周血进行了弓形虫循环抗原 (CAg)和特异性抗体 (Tox- Ig M,Tox- Ig G)的检测 ,并和正常妊娠妇女作比较 ;应用聚合酶链反应 (PCR)技术对经 EL ISA测定为阳性的 1 4例孕妇流产物进行 Tox- DNA检测。结果 流产组 CAg,Tox- Ig M,Tox- Ig G等阳性率分别为 5 .2 5 % ,6 .30 % ,1 1 .76 % ,其中 CAg及 Tox- Ig M阳性率与正常孕妇相比 ,差异有非常显著性 (P<0 .0 1 ) ;1 4例流产物中 Tox- DNA阳性 8例 ,阳性率为 5 7.1 4 %。结论 Tox可通过胎盘传给胎儿 ,引起流产 ;孕妇急性感染与自然流产有相关性 ,CAg,Tox- Ig M,CAg+Tox- Ig M阳性率与发生流产次数呈正相关 相似文献