全文获取类型
收费全文 | 7458篇 |
免费 | 728篇 |
国内免费 | 69篇 |
专业分类
耳鼻咽喉 | 121篇 |
儿科学 | 233篇 |
妇产科学 | 196篇 |
基础医学 | 995篇 |
口腔科学 | 207篇 |
临床医学 | 694篇 |
内科学 | 1392篇 |
皮肤病学 | 222篇 |
神经病学 | 475篇 |
特种医学 | 436篇 |
外科学 | 766篇 |
综合类 | 124篇 |
一般理论 | 2篇 |
预防医学 | 958篇 |
眼科学 | 156篇 |
药学 | 602篇 |
中国医学 | 11篇 |
肿瘤学 | 665篇 |
出版年
2022年 | 47篇 |
2021年 | 101篇 |
2020年 | 78篇 |
2019年 | 124篇 |
2018年 | 131篇 |
2017年 | 114篇 |
2016年 | 141篇 |
2015年 | 156篇 |
2014年 | 180篇 |
2013年 | 222篇 |
2012年 | 339篇 |
2011年 | 289篇 |
2010年 | 199篇 |
2009年 | 194篇 |
2008年 | 308篇 |
2007年 | 364篇 |
2006年 | 352篇 |
2005年 | 353篇 |
2004年 | 289篇 |
2003年 | 280篇 |
2002年 | 255篇 |
2001年 | 240篇 |
2000年 | 242篇 |
1999年 | 226篇 |
1998年 | 146篇 |
1997年 | 143篇 |
1996年 | 111篇 |
1995年 | 123篇 |
1994年 | 98篇 |
1993年 | 98篇 |
1992年 | 143篇 |
1991年 | 178篇 |
1990年 | 176篇 |
1989年 | 186篇 |
1988年 | 185篇 |
1987年 | 146篇 |
1986年 | 114篇 |
1985年 | 127篇 |
1984年 | 111篇 |
1983年 | 69篇 |
1982年 | 63篇 |
1981年 | 70篇 |
1980年 | 51篇 |
1979年 | 85篇 |
1978年 | 53篇 |
1977年 | 60篇 |
1976年 | 57篇 |
1975年 | 61篇 |
1974年 | 54篇 |
1973年 | 52篇 |
排序方式: 共有8255条查询结果,搜索用时 15 毫秒
41.
We compared short-term indicators for service mammography screening in Europe. Data were available from 17 programmes, although not all programmes provided a comprehensive reporting. More than 90% of the target population had been screened within the last 3 years in the WE trial, whereas only two-thirds of women in England and Copenhagen had been screened within the last 3 years, which will delay or reduce the effect of screening compared with the trial. Participation was highest in sparsely populated areas. Detection rates at first screen reached three times the baseline in Copenhagen, the Netherlands and North-West England. The clinical characteristics of screen-detected cases were badly reported. Given their importance for the long-term effect of screening, further data are warranted. Sensitivity and specificity could be measured only indirectly; they showed, however, considerable variation between programmes. Fyn, Florence and Stockholm had succeeded in combining high specificity with high sensitivity. With different recall policies, different proportions of women will experience a false-positive test; expected numbers after three screens were 14%, 10% and 1%, for England, Copenhagen and the Netherlands, respectively. Based on the observed wide variation in short-term indicators, a similar wide variation is expected in the effect of screening on breast cancer mortality. 相似文献
42.
A. J. Pijl K. A. Solen† S. F. Mohammad R. Monson† L. S. Yu J. M. T. van Griensven D. B. Olsen W. J. Kolff 《Artificial organs》1990,14(2):125-129
Device-induced thrombogenesis was studied in an in vitro model using human blood circulated through an artificial ventricle. A new constant pressure filtration technique was used to detect circulating microemboli, the activated partial thromboplastin time (APTT) test was used to monitor the blood for the presence of anticoagulant activity of heparin, and hemolysis was quantified by measuring the plasma free hemoglobin level. Circulation of blood through a 20-ml stroke volume pneumatically driven ventricle for 6-9 h resulted in a significant reduction of APTT, indicating the loss of the anticoagulant effect of heparin. Microemboli concentration was minimal until the APTT decreased below 125 s, at which time the microemboli concentration increased rapidly. This was presumed to be due to the formation of thrombi following a decrease in heparin activity. A significant increase in hemolysis was also noted when blood was pumped. None of these changes was noted in the nonpumped control blood. Spontaneous loss of heparin activity in blood circulated by a pneumatically driven pump may have clinical implications and may help understanding of the problems associated with device-induced thrombogenesis. 相似文献
43.
P. S. Karnes A. T. Shamban D. R. Olsen M. J. Fazio R. E. Falk 《American journal of medical genetics. Part A》1992,42(1):29-34
Several “progeroid” syndromes have now been identified. The De Barsy syndrome is an autosomal recessive syndrome of dwarfism, mental deficiency, an “aged” appearance at birth, abnormal elastic fibers on skin biopsy, and lax skin, large helices, eye abnormalities, lax joints, hypotonia, and athetoid posturing. We report one case and review 11 cases from the literature. To understand the abnormal appearance of the elastic fibers on biopsy, we performed elastin gene expression studies on fibroblasts cultured from our patient's skin. Molecular hybridization studies revealed reduced elastin mRNA steady-state levels as compared with age matched control individuals. Assuming normal rates of mRNA translation, reduced elastin synthesis would occur. Diminished dermal elastin content could explain the altered cutaneous elasticity, decreased elastic fibers in the skin, and many clinical manifestations of individuals with this condition. 相似文献
44.
45.
大狼毒三萜类化学成分的研究 总被引:3,自引:0,他引:3
自大戟科(Euphorbiaceae)植物大狼毒(Euphorbia nematocypha Hand—Mazz)根的乙醇提取物的苯溶解部分,经20%AgNO3硅胶层析,分离得到七个三萜类成分。根据光谱(IR,EIMS,1H—NMR和13C—NMR)和化学方法,确定其中一个化合物为新化合物,命名为大狼毒醇(nematocyphol,Ⅳa),其它化合物为已知物:印度荆芥醇乙酸酯(nepehinol acetate Ⅰ),日尔曼醇乙酸酯(germanicol acetate Ⅱ),大戟醇(euphol,Ⅲ),蒲公英醇(taraxasterol,Ⅴa),24-亚甲基环阿尔廷醇(24-methylenecycloartanol,Ⅴa)和印度荆芥醇(nepehinol,Ⅶa)。这些化合物均为首次从大狼毒中得到。 相似文献
46.
The fingers of seven women with primary Raynaud's phenomenon (PRP), 10 female controls, seven men with vibration induced white finger (VWF), and eight male controls were exposed to vibration and the relative change in finger capillary blood flow was measured by an atraumatic 133xenon washout technique without and during proximal nervous blockade. All four groups showed a vasoconstriction to vibration (p less than or equal to 0.02) which was abolished by proximal nervous blockade. Women with PRP had an augmented response to vibration (p less than 0.01) and men with VWF had a normal response (p greater than 0.10) when compared with that of their respective sex matched controls. The results show the existence of a vibration elicited central sympathetic vasoconstrictor reflex in the normal finger and in fingers affected by PRP and VWF. The results indicate a hyperreactivity of the central sympathetic nervous system in PRP and VWF and a dysfunction of the peripheral sensory nerve fibres in subjects with VWF. The described vibration test may be of guidance in the differentiation of PRP from VWF. 相似文献
47.
48.
Changing smoking, drinking, and eating behaviour among pregnant women in Denmark. Evaluation of a health campaign in a local region 总被引:1,自引:0,他引:1
J Olsen G Frische A O Poulsen H Kirchheiner 《Scandinavian journal of social medicine》1989,17(4):277-280
Health behaviour during pregnancy was examined before and after a comprehensive health campaign targeted at pregnant women in Odense, Denmark. Furthermore, lifestyle habits were compared before and during the campaign with similar habits in Aalborg, Denmark. All 13,815 pregnant women (equal numbers from each city) were enrolled in the study, and 11,980 gave information on eating, drinking, and smoking habits during pregnancy. Data collection in both cities took place from April 1984 to April 1987. The campaign, which was entitled "Healthy Habits for Two", ran from April 1985 to April 1987 in the city of Odense only. No significant change in health behaviour in the Odense area was noted after the start of the campaign. 相似文献
49.
Olsen LH Mortensen K Martinussen T Larsson LI Baandrup U Pedersen HD 《Journal of comparative pathology》2003,129(2-3):120-130
Comparable pathological changes in the mitral valve have been described in dogs, pigs and human patients with myxomatous mitral valve disease (MMVD), i.e., primary mitral valve prolapse. The progressive myxomatous changes are probably a response to repeated impact on the leaflets, and endothelial stress or damage probably plays a central role in the pathogenesis. Little, however, is known about the vasoactive substances that mediate the subendothelial changes. The aim of this study was to investigate the expression of nitric oxide synthase (NOS) in canine mitral valve leaflets and to relate the findings to MMVD changes. The mitral valve was taken post mortem from 12 dogs (six males and six females) and a whole valve NADPH (the reduced form of nicotinamide-adenine dinucleotide phosphate) diaphorase (NADPH-d) reaction was performed. Macroscopical (semiquantitative) and microscopical (computer image analysis) evaluations of the staining due to NADPH-d activity were performed at four specific areas of the valve and related to microscopical signs of MMVD and gross signs of thickening or prolapse, or both. Macroscopically, the NADPH-d colour grade was correlated with the degree of MMVD (P=0.01). In addition, endothelial NADPH-d staining intensity was correlated with macroscopical signs of disease (P=0.004) as well as with collagen degeneration (P=0.008) and deposition of mucopolysaccharides (P=0.02). Age, gender and specific area of the valve did not seem to influence the NADPH-d activity. In conclusion, increased NADPH-d activity, suggesting increased NOS expression, was found in areas of the mitral valve with myxomatous changes. This indicates that nitric oxide (NO) may play a role in the pathogenesis of MMVD in dogs. 相似文献
50.
P G Mbuthia L W Njagi P N Nyaga L C Bebora U Minga J Kamundia J E Olsen 《Avian pathology》2008,37(1):51-57
Pasteurella multocida causes fowl cholera, a highly contagious and severe disease in chickens and water fowls. The disease is not well described in less intensive production systems, including scavenging family poultry production in developing countries. P. multocida was isolated from 25.9% of healthy-looking ducks and 6.2% of chickens from free-range family poultry farms and at slaughter slabs at market. On experimental infection with 1.2 to 2.0 x 10(8) organisms of the P. multocida type strain (NCTC 10322(T)), 12-week-old chickens expressed fowl cholera clinical signs significantly more times (372 signs) than those of 4-week-old, 8-week-old and 16-week-old chickens (173, 272 and 187 signs) and more signs were severe. In family ducks the 8-week-old birds expressed clinical signs significantly more times (188 signs) than those of the other age groups (117, 80, and 83 signs, respectively) and severe signs were more frequent. P. multocida transmitted from seeder birds (n=12) to sentinel birds (n=30), which developed clinical signs, and in some cases lesions of fowl cholera allowed bacterial re-isolation, whether infected ducks served as seeders for chickens or chickens served as seeder for ducks. This study has documented the occurrence of P. multocida among healthy-appearing family poultry in a tropical setting, and demonstrated that age susceptibility is highest in 12-week-old family chickens and 8-week-old family ducks when challenged with a low-virulent strain of P. multocida. It has further demonstrated that cross-transmission of fowl cholera may happen between family ducks and chickens, and vice versa. 相似文献