全文获取类型
收费全文 | 270271篇 |
免费 | 15468篇 |
国内免费 | 1040篇 |
专业分类
耳鼻咽喉 | 3144篇 |
儿科学 | 8849篇 |
妇产科学 | 5967篇 |
基础医学 | 37656篇 |
口腔科学 | 10805篇 |
临床医学 | 21603篇 |
内科学 | 60736篇 |
皮肤病学 | 6814篇 |
神经病学 | 24289篇 |
特种医学 | 7699篇 |
外国民族医学 | 27篇 |
外科学 | 30284篇 |
综合类 | 1775篇 |
现状与发展 | 1篇 |
一般理论 | 108篇 |
预防医学 | 26889篇 |
眼科学 | 4769篇 |
药学 | 17300篇 |
中国医学 | 1006篇 |
肿瘤学 | 17058篇 |
出版年
2023年 | 1808篇 |
2022年 | 3931篇 |
2021年 | 6927篇 |
2020年 | 4496篇 |
2019年 | 6228篇 |
2018年 | 8047篇 |
2017年 | 6095篇 |
2016年 | 6253篇 |
2015年 | 7091篇 |
2014年 | 9455篇 |
2013年 | 12212篇 |
2012年 | 18759篇 |
2011年 | 19517篇 |
2010年 | 10298篇 |
2009年 | 9080篇 |
2008年 | 15392篇 |
2007年 | 16007篇 |
2006年 | 14790篇 |
2005年 | 14728篇 |
2004年 | 13621篇 |
2003年 | 12388篇 |
2002年 | 9961篇 |
2001年 | 5671篇 |
2000年 | 5470篇 |
1999年 | 5073篇 |
1998年 | 2330篇 |
1997年 | 1926篇 |
1996年 | 1816篇 |
1995年 | 1539篇 |
1994年 | 1493篇 |
1993年 | 1315篇 |
1992年 | 2973篇 |
1991年 | 2791篇 |
1990年 | 2587篇 |
1989年 | 2554篇 |
1988年 | 2292篇 |
1987年 | 2127篇 |
1986年 | 2006篇 |
1985年 | 1880篇 |
1984年 | 1405篇 |
1983年 | 1141篇 |
1982年 | 719篇 |
1981年 | 627篇 |
1980年 | 610篇 |
1979年 | 1003篇 |
1978年 | 701篇 |
1977年 | 547篇 |
1975年 | 599篇 |
1974年 | 605篇 |
1973年 | 581篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
E. A. Rosenbaum A. Caballero de Castro L. Gauna A. M. Pechen de D'Angelo 《Archives of environmental contamination and toxicology》1988,17(6):831-835
The exposure of newly fertilized amphibian embryos to malathion (44 mg/L) produces 67% mortality on the fifth day of exposure. Clinical signs of intoxication are evident on the fourth day. A variety of biochemical parameters, such as enzyme activity, lipid and protein content, was examined in control and malathion-treated embryos. The activity of acetyl, butyrylcholinesterase and aliesterase are quickly inhibited. An interference with cellular protein synthesis and redistribution is possible. A slight increase in total phospholipids is evident after 24 hr of exposure. 相似文献
992.
Biodistribution of radioactive epidermal growth factor in normal and tumor bearing mice 总被引:1,自引:0,他引:1
The biodistribution of iodinated epidermal growth factor in normal and tumor bearing mice was analyzed. The uptake of epidermal growth factor was high in the liver, skin and submaxillary gland, which all have detected receptors for the growth factor. Organs, such as lung, heart, spleen, intestine, bone and central nervous system, which lack the receptor, did not retain the growth factor. In tumor bearing mice, the growth factor accumulated in receptor positive tumors, but to a lesser extent than in the liver. This finding will probably prevent the use of epidermal growth factor as a carrier for radionuclides for a therapeutic purpose. 相似文献
993.
Angle-dependent backscatter from the arterial wall 总被引:1,自引:0,他引:1
M G de Kroon L F van der Wal W J Gussenhoven N Bom 《Ultrasound in medicine & biology》1991,17(2):121-126
The anisotropic nature of intra-arterial echographic images is reported, and the source of this anisotropy is investigated using postmortem human iliac arteries. A 27 MHz transducer, mounted on an ultrasonic microscope, is used to quantify the angular dependence of the backscatter power versus the angle of incidence, and these results are correlated with histological findings. Besides the observed differences in the acoustic response of morphologically different tissues, significant variations in backscatter power are found in both media and internal elastic lamina due to variations in the angle of incidence. This angle dependence is caused by the dominant orientation of fibers in tissue layers and by the shape and size various scattering particles. The results indicate that long microscopic structures with one main orientation are responsible for the backscattered signal and that the angular-dependent response is related to the histologically determined orientation of these fibers. These results may have an impact on the assessment of intra-arterial echographic images. 相似文献
994.
995.
Two amino-acid substitutions in the myelin protein zero gene of a case of Charcot-Marie-Tooth disease associated with light-near dissociation. 总被引:2,自引:0,他引:2
H M E Bienfait F Baas A A W M Gabre?ls-Festen J H T M Koelman C T Langerhorst M de Visser 《Neuromuscular disorders : NMD》2002,12(3):281-285
Charcot-Marie-Tooth disease caused by mutations of the myelin protein zero gene demonstrates considerable phenotypical variability. We describe a 45-year-old female with a peripheral neuropathy with demyelinating and axonal features, pes cavus and pupillary light-near dissociation. She was heterozygous for two mutations in the myelin protein zero gene (His81Tyr and Val113Phe), both present on the same allele. Our patient shows a less severe phenotype than previously described patients with a His81Arg mutation. Multiple mutations in the myelin protein zero gene, as well as Charcot-Marie-Tooth with pupillary abnormalities have previously been described in rare instances. However, concurrent occurrence of both phenomena is a novel finding. 相似文献
996.
Michael Groeneweg Suzan Tan Annemieke M. Boot Johan C. de Jongste Jan Bouquet Maarten Sinaasappel 《Journal of cystic fibrosis》2002,1(4):583-280
BACKGROUND: Assessment of nutritional status in children with cystic fibrosis (CF) is clinically relevant. Methods to measure nutritional status should be reliable and non-invasive, and reference values should be available. AIM: To compare weight and height measurements and measurements of specific body compartments in children with CF. METHODS: In a cross-sectional survey of 58 children with CF (28 females), we compared height and weight (expressed as: weight-for-height, body mass index (BMI), height-for-age and weight-for-age) with fat mass (skinfold sum (SFS)), muscle mass (upper arm circumference (UAC)) and bioelectrical impedance analysis (BIA). Results were expressed as Z-scores, using Dutch reference values. RESULTS: BMI and weight-for-height were within the normal range (mean Z-score (range): -0.13 (-1.5, 2.7) and -0.02 (-1.7, 2.8)). Weight and height corrected for age were below normal (mean Z-score (range): -0.79 (-2.4, -0.05) and -1.2 (-2.8, 1.4) (P<0.01)). Lean body mass by skinfold sum (LBM(sfs)), UAC and BIA were also significantly below reference values (mean Z-score (range): -0.9 (-2.2, 1.8), -0.95 (-2.4, 1.8) and -1.1 (-3.6, 1.0) (P<0.01)). Lean body mass (LBM) by BIA correlated with LBM(sfs). BIA systematically underestimated LBM in both CF patients and in control subjects. CONCLUSION: Nutritional status of children with CF must be evaluated, using age-corrected weight and height expressed in Z-score. LBM estimated by SFS, UAC and by BIA appear to be useful, although longitudinal studies in CF children should be performed to evaluate their clinical significance in detecting changes in nutritional status. 相似文献
997.
Pilar Prieto-Alvarez Isabel Tello-Galindo Jesus Cuenca-Peña Maria Rull-Bartomeu Carmen Gomar-Sancho 《Journal canadien d'anesthésie》2002,49(1):25-31
PURPOSE: To compare two protocols of epidural administration of racemic methadone for postoperative analgesia (continuous infusion and intermittent bolus), focussing on plasma concentration, analgesic efficacy and side effects. METHODS: Ninety patients undergoing abdominal or lower-limb surgery were randomly assigned to two groups in a prospective double-blind design. The continuous infusion patients (n=60) received initial doses of 3 to 6 mg followed by 6 to 12 mg by continuous infusion over 24 hr. The bolus administration patients (n=30) received repeated boluses of 3 to 6 mg of racemic methadone every eight hours. Pain intensity was assessed on a visual analog scale. Amount of supplementary analgesia was recorded, as was the incidence of side effects. Plasma methadone concentrations were determined by high performance liquid chromatography. Treatment was continued for 72 hr. RESULTS: Pain relief was good and comparable in both groups throughout the three days of treatment. No accumulation of plasma racemic methadone was observed in either group, although the concentrations were significantly higher in the bolus group. Miosis was significantly more frequent in the bolus group. CONCLUSION: Plasma methadone concentrations were significantly lower with continuous infusion. Plasma methadone accumulation, which is considered the main disadvantage for its purported influence on the incidence of side effects, did not occur at the doses used over the three days of treatment that we report. 相似文献
998.
Luis Erik Clavería Jacinto Duarte Maria Dolores Sevillano Angel Pérez-Sempere Carmen Cabezas Fernanda Rodríguez Jesús de Pedro-Cuesta 《Movement disorders》2002,17(2):242-249
We assessed the prevalence of Parkinson's disease in Cantalejo, Spain. In 1994, we screened 1,579 persons (age > or = 40 years) using a high-sensitivity method. Cases fulfilling established clinical criteria were followed for a minimum of 3 years. Prevalences were compared with those from other door-to-door surveys. We detected 27 individuals with parkinsonism, 20 of whom had Parkinson's disease. The prevalence of Parkinson's disease increased with age and, when age-adjusted to European standards, was 9.01 per 1,000 (age 40 years and over; 10.78 in men and 5.23 in women). Of the 11 men, three were in Hoehn & Yahr grades III-IV, but six of the nine women were more severely affected. Overall, we found 18 newly diagnosed cases of parkinsonism, 13 of which were Parkinson's disease, and the majority of which were in men aged 80 years or older with a mean duration of illness of 5 years. Our prevalence figures are the highest reported, apparently because of the inclusion of several very elderly men. Parkinson's disease in Cantalejo is less severe in men than in women, particularly in those newly diagnosed. Despite the low numbers, the high prevalence and sex-related pattern are unexplained but they probably relate to the high sensitivity of the screening method. 相似文献
999.
原癌基因蛋白质C-erbB-2在乳腺良恶性病变中表达的意义 总被引:3,自引:1,他引:2
目的:检测原癌基因蛋白质C-erbB-2在乳腺良恶性病变中的表达及意义.方法:对111例乳腺良恶性病变的石蜡切片标本进行免疫组织化学染色.结果:乳腺良恶性病变中乳腺导管内乳头状瘤病的C-erbB-2阳性率为31.3%,与乳腺纤维腺病和纤维腺瘤比较差异有显著性(P<0.01),乳腺癌C-erbB-2的阳性率为74.3%,与良性病变比较差异有显著性(P<0.01);乳腺癌C-erbB-2表达与肿瘤大小和组织学分级呈正比(P<0.05),与激素受体(ER、PR)水平及5年生存期呈反比(P<0.05),与淋巴结是否转移无关.结论:C-erbB-2表达的乳腺导管内乳头状瘤病容易癌变,C-erbB-2过度表达的乳腺癌组织分化差、生存期短、预后不好.C-erbB-2 可作为判定乳腺导管内乳头状瘤病早期癌变及乳腺癌预后的有效指标. 相似文献
1000.