全文获取类型
收费全文 | 3050篇 |
免费 | 264篇 |
国内免费 | 24篇 |
专业分类
耳鼻咽喉 | 31篇 |
儿科学 | 130篇 |
妇产科学 | 83篇 |
基础医学 | 403篇 |
口腔科学 | 75篇 |
临床医学 | 398篇 |
内科学 | 586篇 |
皮肤病学 | 31篇 |
神经病学 | 165篇 |
特种医学 | 224篇 |
外科学 | 461篇 |
综合类 | 59篇 |
一般理论 | 1篇 |
预防医学 | 249篇 |
眼科学 | 23篇 |
药学 | 157篇 |
中国医学 | 2篇 |
肿瘤学 | 260篇 |
出版年
2023年 | 19篇 |
2020年 | 25篇 |
2019年 | 26篇 |
2018年 | 36篇 |
2017年 | 31篇 |
2016年 | 50篇 |
2015年 | 39篇 |
2014年 | 53篇 |
2013年 | 76篇 |
2012年 | 143篇 |
2011年 | 180篇 |
2010年 | 91篇 |
2009年 | 73篇 |
2008年 | 121篇 |
2007年 | 146篇 |
2006年 | 118篇 |
2005年 | 125篇 |
2004年 | 135篇 |
2003年 | 122篇 |
2002年 | 111篇 |
2001年 | 103篇 |
2000年 | 114篇 |
1999年 | 97篇 |
1998年 | 64篇 |
1997年 | 61篇 |
1996年 | 64篇 |
1995年 | 43篇 |
1994年 | 41篇 |
1993年 | 37篇 |
1992年 | 78篇 |
1991年 | 82篇 |
1990年 | 61篇 |
1989年 | 69篇 |
1988年 | 69篇 |
1987年 | 62篇 |
1986年 | 62篇 |
1985年 | 51篇 |
1984年 | 49篇 |
1983年 | 31篇 |
1982年 | 27篇 |
1981年 | 16篇 |
1979年 | 28篇 |
1978年 | 29篇 |
1977年 | 23篇 |
1976年 | 25篇 |
1975年 | 16篇 |
1974年 | 26篇 |
1973年 | 22篇 |
1971年 | 18篇 |
1970年 | 22篇 |
排序方式: 共有3338条查询结果,搜索用时 12 毫秒
1.
2.
Twin study of genetic and environmental effects on lipid levels 总被引:4,自引:0,他引:4
D L O'Connell R F Heller D C Roberts J R Allen J C Knapp P L Steele D Silove 《Genetic epidemiology》1988,5(5):323-341
A study of 106 pairs of monozygotic (MZ) and 94 pairs of dizygotic (DZ) twins tested the hypothesis that part of the previously described genetic influence on blood lipid levels can be ascribed to closer similarities among MZ than among DZ twin pairs in environmental factors that affect lipid levels. Participants were adult twin volunteers (age 17-66; 64 male and 136 female pairs) who were selected from the NH & MRC Twin Registry or were respondents to advertisements. They completed a 4-day weighed food diary from which mean nutrient intake was derived. Information on lifestyle and demographic variables was obtained by questionnaire and a nonfasting blood sample was taken for measures of total, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol and the HDL2 and HDL3 subfractions. Height and weight were measured, and body mass index (BMI) was calculated (kg/m2). Estimates of the heritability of sex-adjusted lipid levels were 0.72 for total cholesterol, 0.79 for HDL cholesterol, 0.69 for HDL2, 0.20 for HDL3, 1.06 for LDL cholesterol, and 0.44 for sex-adjusted BMI. In all cases except for HDL3, genetic variance was statistically significant. After adjusting for the effects of environmental variables in three different ways, the estimates of heritability were somewhat lower for total cholesterol, HDL2, and BMI, and those for HDL cholesterol (borderline) and LDL cholesterol (definitely) remained statistically significant but were decreased. A genetic influence on HDL3 was not found. Adjusted heritability estimates obtained from one method of analysis were 0.35 for total cholesterol, 0.49 for HDL, 0.04 for HDL2, -0.34 for HDL3, 0.66 for LDL, and 0.32 for BMI. These results suggest that the assumptions made in the classical twin study approach are not appropriate when examining genetic effects on lipid levels or BMI, or indeed on any biological variable that may be affected by environmental factors that tend to be more similar in MZ twins than in DZ twins. In these circumstances, more complex models may be needed to differentiate between genetic and environmental influences. 相似文献
3.
One hundred and thirty children with Down's syndrome were screened for the presence of atlantoaxial instability, using both clinical examination and radiographs of the cervical spine taken in flexion and hyperextension views. Seven children were found to have radiological evidence of atlantoaxial instability, with an atlanto-dens interval greater than 5.0 mm in one or all positions. Although a full clinical history was obtained from the attending parent and each child underwent a complete neurological examination, there were no factors detected which differentiated between those with radiological evidence of atlantoaxial instability and those with a normal atlantodens distance. It is recommended that children with Down's syndrome be screened twice, at the ages of 5-10 years and at 15 years. 相似文献
4.
5.
Factors influencing women to undergo screening mammography 总被引:2,自引:0,他引:2
6.
Braffman BH; Coleman BG; Ramchandani P; Arger PH; Nodine CF; Dinsmore BJ; Louie A; Betsch SE 《Radiology》1994,190(3):797
7.
For many years, burn professionals have attempted to assess the outcomes of different types of burn injury and the factors that are related to good patterns of coping with the aftermath of thermal injury. Most writers have attempted to use objective criteria such as return to work or preexisting psychologic problems (e.g., alcoholism) in determining the success of rehabilitation, but much controversy over the forms of assessment persists. It is agreed that antisocial personality, organic brain syndromes, and lack of social support all undermine good recovery for patients with burns. The authors have attempted to look at the subjective side of the patient's adjustment by providing representative examples of several types of burn adjustment in terms of personality features, all of which would tend to complement other approaches. The use of denial, the ways in which hostility is managed by the patient, and how he or she uses key persons in the environment are examined. The cognitive, emotional (affective), and behavioral styles of patients are examined as part of this pilot study of cluster patterns or types of adjustment. 相似文献
8.
J. Towfighi W. A. Kofke B. K. O'Connell C. Housman J. M. Graybeal 《Acta neuropathologica》1989,77(6):612-620
Summary Light microscopic and ultrastructural changes of substantia nigra were studied in paralyzed ventilated rats with status epilepticus induced by mercaptopropionic acid. Some rats were killed at the end of seizure activity and others were examined in varying intervals after the arrest of seizure. The earliest changes were reduction in the size of the neuronal nuclei and chromatin clumping followed by simultaneous distention of axons and dendrites. There was also enlargement of the neuronal perikarya associated with microvacuolation. This neuronal microvacuolation corresponded ultrastructurally to swollen mitochondria with disrupted cristae. These changes were followed by progressive neuronal shrinkage and astrocytic swelling. The swollen astrocytic processes together with swollen neurites gave a spongy appearance to the involved area. The lesion thereafter progressively enlarged and evolved into an area of frank necrosis containing abundant macrophages. This lesion is morphologically different from that produced in cortex and hippocampus by seizure activity or due to the direct effect of excitotoxins. The significance of substantia nigra pars reticularis changes and their pathogenesis are discussed. 相似文献
9.
10.
R A O'Connell S N Sireci M E Fastov J E Cueva D Luck M R Nathanson R L Van Heertum 《General hospital psychiatry》1991,13(5):305-312
Cerebral single photon emission computed tomography (SPECT), a method of functional brain imaging, measures cerebral blood flow and metabolism. This paper describes the imaging procedure and several cases where cerebral SPECT was of use in the differential diagnosis of medically ill patients who also presented with psychopathology. SPECT patterns in cerebrovascular disease, dementia, focal epilepsy, and AIDS are at present the best described and seem to be the most specific. Often changes in regional cerebral blood flow are seen before structural changes become apparent on CT or MRI. Cerebral SPECT can add valuable diagnostic information in assessing psychopathology in the medically ill and can often lead to changes in treatment. 相似文献