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   187495篇
  免费   11373篇
  国内免费   480篇
耳鼻咽喉   2432篇
儿科学   6089篇
妇产科学   3980篇
基础医学   25676篇
口腔科学   8225篇
临床医学   14427篇
内科学   41616篇
皮肤病学   4712篇
神经病学   15794篇
特种医学   5618篇
外国民族医学   26篇
外科学   22666篇
综合类   1517篇
现状与发展   1篇
一般理论   72篇
预防医学   19886篇
眼科学   3567篇
药学   11397篇
中国医学   760篇
肿瘤学   10887篇
  2023年   1032篇
  2022年   2219篇
  2021年   4209篇
  2020年   2774篇
  2019年   3977篇
  2018年   5434篇
  2017年   4071篇
  2016年   3807篇
  2015年   4449篇
  2014年   6063篇
  2013年   7713篇
  2012年   12048篇
  2011年   12591篇
  2010年   6386篇
  2009年   5716篇
  2008年   9750篇
  2007年   10313篇
  2006年   9589篇
  2005年   9801篇
  2004年   9184篇
  2003年   8447篇
  2002年   6409篇
  2001年   5140篇
  2000年   5119篇
  1999年   4504篇
  1998年   1699篇
  1997年   1377篇
  1996年   1362篇
  1995年   1159篇
  1994年   1150篇
  1993年   1048篇
  1992年   2750篇
  1991年   2655篇
  1990年   2426篇
  1989年   2386篇
  1988年   2166篇
  1987年   2015篇
  1986年   1888篇
  1985年   1809篇
  1984年   1301篇
  1983年   1052篇
  1982年   606篇
  1981年   547篇
  1980年   525篇
  1979年   952篇
  1978年   620篇
  1977年   491篇
  1975年   565篇
  1974年   557篇
  1973年   558篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
In 19 patients with different types of severe descensus, all without clinical evidence of stress incontinence, urethral stress pressure profiles and stress tests were done before and after repositioning of the prolapse. In 13 of the 19 patients, continence was artificial, because during repositioning they showed leakage of urine; however, 6 of the patients remained continent. The pressure transmission ratios decreased in different parts of the urethra in all the patients when repositioning with a gynecological speculum was done. The drop was most significant in those patients who lost urine after repositioning, showing poor urethral function. In women with genito-urinary prolapse, a test of urethral function is essential, even if there is no clinical evidence of incontinence after removal of the descensus. In cases of severe stress incontinence under this condition, a procedure for bladder neck stabilization should be added to routine prolapse surgery.  相似文献   
962.
963.
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   
964.
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   
965.
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   
966.
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   
967.
968.
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   
969.
This study examined the enumeration and numerical reasoning levels of children with specific language impairment (SLI) compared to those of two groups of typically developing children: children matched for age (AM) and children matched for grammatical ability (GM). The children completed four numerical tasks: reproduction of sets, numerosity of sets, an addition/subtraction condition of the numerosity of sets, and transformation effects (conservation of number). Between-group analyses indicate that the children in the SLI group performed better than the children in the GM group for all set sizes of all tasks with one exception (set size 7 of the odd/subtract task) and performed more poorly than the children in the AM group for 7 of the 16 trials. There was a strong correlation of count range with the reproduction of sets task for the children with SLI, but not for the children in the other two groups. The AM group consistently used verbal counting to facilitate numerical problem solving. Conversely prompting the children with SU to use verbal counting while completing any of the numerical tasks resulted in a 50% decline in accuracy. Children need opportunities to strengthen numerical constructs, such as those enhanced through verbal counting. However, children with SLI also need opportunities to fortify their nonverbal enumeration and numerical reasoning without requiring the use of their deficit area.  相似文献   
970.
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   
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