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   240146篇
  免费   7290篇
  国内免费   1435篇
耳鼻咽喉   3462篇
儿科学   7926篇
妇产科学   6442篇
基础医学   32423篇
口腔科学   6819篇
临床医学   19394篇
内科学   43503篇
皮肤病学   6119篇
神经病学   14779篇
特种医学   13466篇
外国民族医学   102篇
外科学   34589篇
综合类   2718篇
一般理论   8篇
预防医学   18678篇
眼科学   5334篇
药学   17944篇
  8篇
中国医学   1227篇
肿瘤学   13930篇
  2022年   1522篇
  2021年   2220篇
  2020年   1262篇
  2019年   1416篇
  2018年   4972篇
  2017年   5082篇
  2016年   4858篇
  2015年   7104篇
  2014年   6915篇
  2013年   6334篇
  2012年   14165篇
  2011年   8876篇
  2010年   4662篇
  2009年   6009篇
  2008年   4865篇
  2007年   5334篇
  2006年   5275篇
  2005年   13144篇
  2004年   14078篇
  2003年   9459篇
  2002年   4500篇
  2001年   5221篇
  2000年   2514篇
  1999年   6430篇
  1992年   7026篇
  1991年   7265篇
  1990年   7526篇
  1989年   7093篇
  1988年   6594篇
  1987年   6355篇
  1986年   6052篇
  1985年   5305篇
  1984年   3638篇
  1983年   2952篇
  1982年   1029篇
  1979年   3858篇
  1978年   2389篇
  1977年   1808篇
  1976年   1573篇
  1975年   2497篇
  1974年   3124篇
  1973年   2753篇
  1972年   2772篇
  1971年   2756篇
  1970年   2580篇
  1969年   2471篇
  1968年   2249篇
  1967年   2172篇
  1966年   1906篇
  1965年   1132篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
101.
Variations of the medial and inferior choanal limits may facilitate snoring. These are: 1) short vomer without crista choanalis vomeris and adaptational formations, 2) extremely concave posterior margin of the hard palate leading to disproportion between the muscular and aponeurotic part of m. tensor veli palatini and hence to a flabby soft palate especially during sleep, and 3) neonatal relation of the height and width of the choane resulting in a very large choanal region instead of relative reduction of choanal width compared to its increasing height. All these variations result in a flabby soft palate especially during sleep and may lead to formation of whirles of inspired air and snoring.  相似文献   
102.
Development of an auxotrophic oral live Shigella flexneri vaccine   总被引:11,自引:0,他引:11  
An oral live attenuated Shigella flexneri vaccine candidate strain was constructed by making it auxotrophic and dependent on aromatic metabolites not available in mammalian tissues. An aroD gene of Escherichia coli K12 strain NK 5131, inactivated by insertion in it of the Tn 10 transposon, was transduced using phage P1 into a virulent S. flexneri serotype Y strain (Sfl 1) isolated from a patient with bacillary dysentery. One of the transductant strains Sfl 114 was found to invade HeLa cells in vitro, to cause plaque formation in HeLa monolayers (i.e. maintain intracellular multiplication in vitro), but to be unable to cause keratoconjunctivitis in guinea-pig eyes. When the strain was fed to Macacca fascicularis monkeys it was well tolerated, excreted for 1-4 days, and found to elicit a local intestinal sIgA and serum IgA, IgM and IgG responses. Monkeys challenged with 100 ID50 dose (1 X 10(11) bacteria) of the virulent parent Sfl 1 strain were completely protected from development of diarrhoea. Coloscopy of the monkeys and the sampling of intestinal biopsies showed that the vaccine protected against the surface epithelial erosions and ulcerations seen in unimmunized monkeys. Killing of invading virulent shigellae apparently took place intracellularly in the mucosa suggesting that cellular immune mechanisms played a role in the elicited host defence. The constructed S. flexneri Sfl 114 strain has the properties of a promising shigella vaccine and will next be the subject of studies with human volunteers.  相似文献   
103.
104.
N-3 fatty acid deficiency is described in a 7-year-old girl who had been fed solely by gastric tube from the age of 3 years. She had received the same nutrient during the last 22 months, supplying 16.2% of calories from linoleate and 0.07% from alpha-linolenate. She weighed 9.5 kg at the age of 3, and 10.3 kg at the start of the study, the weight being constant the last 15 months. She was now supplemented daily with 1.2 ml of a linseed- and cod liver-oil mixture (5:1, v/v), thereby increasing her alpha-linolenate intake to 0.71% and total N-3 fatty acids to 0.74% of total energy. Two months later, her rate of weight gain was 0.43 kg/month. After 5 months, the fatty acid supplement was changed to 7.5 ml of cod liver oil daily, thereby changing alpha-linolenate and total N-3 acid intake to 0.10% and 1.3% of total energy, respectively. Her rate of weight gain now increased to 0.64 kg/month, and her length increased from 117 to 122 cm in 5 months. The results indicate that the optimal dietary requirement for N-3 fatty acids in this child is higher than 0.74%, and extrapolation estimated the optimal requirement to be 1.1%-1.2% of total calories. The results suggest that N-3 fatty acids are required for normal growth in man.  相似文献   
105.
106.
The relationship between energy expenditure and body composition, in terms of fat and fat-free masses, has previously been described by a variety of predictive regression equations with parameters devoid of physiological content. We present here results obtained by calculating the specific energy expenditure, ie, the energy expenditure per unit of mass, of fat and fat-free tissue on the basis of measurements of the total energy expenditure (EE), the masses of fat (FM), and fat-free (FFM) tissue using the following simple model: EE = k1.FM + k2.FFM where k1 and k2 are the specific energy expenditures of fat and fat-free tissue, respectively. The results of observations on 104 women at rest yielded values for k1 and k2 of 0.31 and 1.35 watts/kg of fat and fat-free mass, respectively, with standard errors of estimate of 0.074 and 0.052 watts/kg, respectively. Analysis of several series of measurements, from other sources and on smaller samples of subjects, yielded similar values at rest but with larger standard errors of estimate. Data from subjects performing varying amounts of work in 24-h measurements showed, as expected, larger values for both tissues. The results explain to a very large extent the well-established relation between resting metabolic rate and body weight, ie, a linear relation with a non-zero intercept. The results also offer a clear-cut explanation for the well known difference in energy expenditure between men and women with the same body weight.  相似文献   
107.
本文选择34颗有银汞充填体悬突的患牙,采用金刚砂钻和银汞磨光钻去除悬突,并观察去除悬突前后部分牙周组织的变化、结果表明银汞充填体悬突危害牙周组织的健康.去除悬突并协同口腔卫生宣教、可促进牙周组织的恢复.  相似文献   
108.
Eleven patients with lunatomalacia were treated by excision of the lunate and instillation of liquid silicone. The silicone vulcanised and formed an in-situ molded prosthesis. The patients were reexamined after a mean of 7.1 years. Four patients were pain-free and two had pain only at work; three had not been improved by the operation and two had undergone arthrodesis. The patients with good results all belonged to group IV pre-operatively. Surprisingly, no patient showed any sign of silicone synovitis, although all the prostheses except one had either fractured or deformed. The reasons for this are discussed and the indications for the operation established.  相似文献   
109.
110.
We have investigated anemia in patients at different stages of the evolution of three chronic renal diseases: Balkan endemic nephropathy (BEN), chronic pyelonephritis (PN) and chronic glomerulonephritis (GN). A total of 88 patients with creatinine clearances from 9 to 118 ml/min and hemoglobin concentrations from 70 to 160 g/l were studied with regard to the relationship, if any, between erythropoietin production and the type and stage of nephropathy. Anemia in BEN was a particular focus of interest since it had been stated that in BEN, anemia precedes renal failure. Our data neither prove nor disprove this statement. A significant positive correlation between creatinine clearance and hemoglobin concentration was found in all three nephropathies, indicating that in the patients studied the severity of anemia increased with the impairment of renal function regardless of the underlying disease. Serum levels of immunoreactive erythropoietin were in the normal range in 54 patients, moderately increased in 20 and slightly decreased in 14. The erythropoietin level appears to be unrelated to the stage of renal failure or the type of nephropathy. The only exception was the subgroup where the patients with glomerulonephritis and normal renal function had increased serum erythropoietin levels and significantly higher parameters of red blood cell concentration than the patients from the same subgroup with tubulointerstitial nephropathies. In patients with severe renal failure and anemia, serum erythropoietin levels were inappropriately low for the degree of anemia, indicating that erythropoietin plays a role in the pathogenesis of the anemia.  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