首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   194698篇
  免费   11466篇
  国内免费   590篇
耳鼻咽喉   2421篇
儿科学   6042篇
妇产科学   3990篇
基础医学   25800篇
口腔科学   8102篇
临床医学   14374篇
内科学   44688篇
皮肤病学   4810篇
神经病学   17113篇
特种医学   6033篇
外国民族医学   26篇
外科学   24758篇
综合类   1426篇
现状与发展   1篇
一般理论   66篇
预防医学   18833篇
眼科学   3589篇
药学   11710篇
中国医学   717篇
肿瘤学   12255篇
  2023年   1047篇
  2022年   2303篇
  2021年   4330篇
  2020年   2852篇
  2019年   4005篇
  2018年   5493篇
  2017年   4150篇
  2016年   3953篇
  2015年   4592篇
  2014年   6367篇
  2013年   8053篇
  2012年   12555篇
  2011年   13042篇
  2010年   6732篇
  2009年   6082篇
  2008年   10293篇
  2007年   10949篇
  2006年   10152篇
  2005年   10417篇
  2004年   9883篇
  2003年   8894篇
  2002年   6908篇
  2001年   5121篇
  2000年   5048篇
  1999年   4480篇
  1998年   1778篇
  1997年   1482篇
  1996年   1457篇
  1995年   1242篇
  1994年   1197篇
  1993年   1098篇
  1992年   2760篇
  1991年   2645篇
  1990年   2421篇
  1989年   2396篇
  1988年   2170篇
  1987年   2016篇
  1986年   1880篇
  1985年   1803篇
  1984年   1333篇
  1983年   1053篇
  1982年   609篇
  1981年   555篇
  1980年   524篇
  1979年   940篇
  1978年   620篇
  1977年   502篇
  1975年   555篇
  1974年   555篇
  1973年   554篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
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   
992.
Angle-dependent backscatter from the arterial wall   总被引:1,自引:0,他引:1  
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   
993.
A comparative chronic inhalation exposure study was performed to investigate the potential health effects of gasoline and ethanol engine exhaust fumes. Test atmospheres of gasoline and ethanol exhaust were given to Wistar rats and Balb C mice housed in inhalation chambers for a period of 5 weeks. Gas concentration and physical parameters were continually monitored during the exposure period. Several biological parameters were assessed after the exposure including pulmonary function, mutagenicity, and hematological, biochemical, and morphological examinations. The results demonstrated that the chronic toxicity of the gasoline-fueled engine is significantly higher than that of the ethanol engine.  相似文献   
994.
995.
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.
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.
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   
998.
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   
999.
1000.
Pentachlorophenol (PCP) is a widely applied insecticide and fungicide, particularly in wood preservation. Significant amounts of this compound have been reported in human serum, adipose tissue and urine. PCP is even found in people not occupationally exposed to this toxin or not living in PCP-treated log-houses. Substantial concentrations of this possible neurotoxic agent were detected in the cerebrospinal fluid (CSF) of 16 neurologic patients as measured by a high resolution gas chromatographic method using electron capture detection. This is the first report on PCP levels in (human) CSF. The observed level in CSF ranged from 0.24 up to 2.03 micrograms/L (ppb), with an average value of 0.75 +/- 0.49. The cerebrospinal fluid level did not correlate with the serum PCP concentration nor with the protein level of the cerebrospinal fluid.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号