全文获取类型
收费全文 | 6986篇 |
免费 | 483篇 |
国内免费 | 25篇 |
专业分类
耳鼻咽喉 | 83篇 |
儿科学 | 204篇 |
妇产科学 | 105篇 |
基础医学 | 987篇 |
口腔科学 | 956篇 |
临床医学 | 501篇 |
内科学 | 1472篇 |
皮肤病学 | 152篇 |
神经病学 | 447篇 |
特种医学 | 262篇 |
外科学 | 683篇 |
综合类 | 41篇 |
预防医学 | 777篇 |
眼科学 | 117篇 |
药学 | 469篇 |
中国医学 | 64篇 |
肿瘤学 | 174篇 |
出版年
2023年 | 61篇 |
2022年 | 142篇 |
2021年 | 234篇 |
2020年 | 188篇 |
2019年 | 231篇 |
2018年 | 307篇 |
2017年 | 183篇 |
2016年 | 206篇 |
2015年 | 256篇 |
2014年 | 325篇 |
2013年 | 389篇 |
2012年 | 544篇 |
2011年 | 627篇 |
2010年 | 320篇 |
2009年 | 287篇 |
2008年 | 379篇 |
2007年 | 418篇 |
2006年 | 324篇 |
2005年 | 264篇 |
2004年 | 201篇 |
2003年 | 158篇 |
2002年 | 166篇 |
2001年 | 125篇 |
2000年 | 112篇 |
1999年 | 113篇 |
1998年 | 55篇 |
1997年 | 50篇 |
1996年 | 47篇 |
1995年 | 40篇 |
1994年 | 40篇 |
1993年 | 30篇 |
1992年 | 45篇 |
1991年 | 50篇 |
1990年 | 33篇 |
1989年 | 55篇 |
1988年 | 44篇 |
1987年 | 53篇 |
1986年 | 46篇 |
1985年 | 33篇 |
1984年 | 32篇 |
1983年 | 25篇 |
1982年 | 25篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1975年 | 15篇 |
1970年 | 20篇 |
1968年 | 20篇 |
排序方式: 共有7494条查询结果,搜索用时 578 毫秒
81.
Bone Mineral Density and Androgen Levels in Elderly Males 总被引:4,自引:0,他引:4
Rapado A Hawkins F Sobrinho L Díaz-Curiel M Galvao-Telles A Arver S Melo Gomes J Mazer N Garcia e Costa J Horcajada C López-Gavilanes E Mascarenhas M Papapietro K López Alvarez MB Pereira MC Martinez G Valverde I García JJ Carballal JJ García I 《Calcified tissue international》1999,65(6):417-421
To clarify the relationship of sex male hormones and bone in men, we studied in 140 healthy elderly men (aged 55–90 years)
the relation between serum levels of androgens and related sex hormones, bone mineral density (BMD) at different sites, and
other parameters related to bone metabolism. Our results show a slight decrease of serum-free testosterone with age, with
an increase of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in a third of the elderly subjects studied.
BMD decreased significantly with age in all regions studied, except in the lumbar spine. We found a positive correlation between
body mass index (BMI) and BMD at the lumbar spine and femoral neck (P < 0.001). No relationship was found (uni- and multivariate regression analysis) between serum androgens or sex hormone-binding
globulin (SHBG) and BMD. We found a positive correlation of vitamin D binding protein (DBP) and osteocalcin with lumbar spine
BMD and with BMI, DBP, IGF-1, and PTH with femoral neck BMD. In conclusion, there is a slight decline in free testosterone
and BMD in the healthy elderly males. However, sex male hormones are not correlated to the decrease in hip BMD. Other age-related
factors must be associated with bone loss in elderly males.
Received: 29 April 1997 / Accepted: 9 November 1997 相似文献
82.
Gomes J Lloyd OL Revitt DM 《International archives of occupational and environmental health》1999,72(1):40-45
Farm workers in developing countries tend not to use protective measures while handling pesticides. This study investigates
the use of personal protection equipment and the practice of safety and hygiene procedures in the handling of pesticides in
agriculture. Methods: Through a multi-stage sampling technique, one-fifth of the farms in a region were selected and all the farm workers at these
farms were included in the study. A comparison population matching in age, socio-economic status and stay in the region was
selected. A specifically designed questionnaire was used to collect information on the use of protective measures and the
practice of safety and hygiene during work and on the disposal of empty pesticide containers. Blood pressure and erythrocyte
acetylcholinesterase (AChE) activity were measured in the exposed and the unexposed populations. Results: Protective equipment was worn by a minority of farm workers – gloves, by 35%; work coveralls, by 36%; a scarf to cover the
nose and mouth, by 39%; and shoes at work, by 79%. With regard to personal hygiene measures, 83% of the workers changed clothes
after work and the same proportion took a shower after work; 63% and 46% drank and ate while at work respectively; and 11%
used articles of domestic use in the preparation of pesticides on the farm. Most of the farm workers (96%) were asked to prepare
pesticides for spraying by the foreman and 61% were asked to spray the pesticides on the crops. AChE activity was highly significantly
depleted in the exposed population as compared with the unexposed population. Conclusions: AChE depletion was found to be negatively associated with the use of gloves, of work coveralls, and of a scarf to cover the
nose and mouth and with the implementation of safety and hygiene procedures on the farm. AChE depletion was positively associated
with the frequency of pesticide spraying.
Received: 30 January 1998 / Accepted: 19 August 1998 相似文献
83.
Techniques of time series analysis were used to examine historical records of the incidence of diphtheria, pertussis, and measles, and of deaths by measles in Portugal during the twentieth century. There are statistically significant seasonal and long-term oscillations in the incidence of these diseases. Seasonal oscillations appear to be in close association with the resumption of school classes in the fall in the case of diphtheria, but not in pertussis and measles. Long-term oscillations in pertussis (3.5–4 year period) and measles (3-year period), before vaccination, corroborate theoretical predictions about the dynamics of these diseases, whereas absence of long-term oscillations in diphtheria is probably due to the influential presence of carriers upon the dynamics of the disease. Mass vaccination strongly suppressed disease incidence, did not eliminate seasonal oscillations, and appeared to have acted to lengthen long-term periodicity in pertussis and measles. 相似文献
84.
A quartz crystal microbalance has been used to check the purity of glycerol. The experimental procedure involves no derivatization or other preliminary step except determination of water content. The protocol consists of the direct reading of the frequency of a quartz crystal with one face in contact with an aqueous solution of the glycerol to be tested. The method is inexpensive, simple, rapid, and highly sensitive; diethylene glycol contamination at the 3.61% level could be detected. 相似文献
85.
A. Dolei C. Serra A. Biolchini S. Curreli P. Marongiu E. Gomes F. Ameglio 《Perspectives in Drug Discovery and Design》1996,5(1):93-102
Summary HIV-1 is a polytropic virus that, apart from hematopoietic cells, can replicate in several cells from solid tissues. Virus yields vary widely, closely resembling differences in HIV binding to the cells; the latter phenomenon appears mainly related to the extent of CD4 expression, even though other molecules have been implied in virus-cell interactions, the expression of which on the cell membrane can be modulated by several stimuli. During the course of HIV replication, a series of cytokines is produced and released in parallel to virus growth, particularly IL-6 and TNF-. In fact, exposure of fibroblasts or epithelial cells to these HIV-in-duced cytokines causes an increase of CD4 expression, HIV adsorption to uninfected cells, and release of infectious virions by infected cells. In cells exposed to interferon-, IL-6 and TNF- allow the virus to bypass interferon inhibition of virus release. The fact that HIV-1 adsorption and spread can be mediated by HIV-induced cytokines may be relevant in AIDS pathogenesis, accelerating virus transmission both within the organ and to infiltrating cells, activating a self-maintaining mechanism of infection. 相似文献
86.
C. Gomes T. H. Svensson G. Trolin 《Journal of neural transmission (Vienna, Austria : 1996)》1976,39(1-2):33-46
Summary Morphine caused in the anaesthetized rat reduction in brain noradrenaline (NA) turnover, hypotension and bradycardia, similarly to the antihypertensive,-adrenergic agonist, clonidine. All effects of morphine were antagonized by naloxone, as well as the-receptor antagonist, yohimbine. In contrast, naloxone did not affect the circulatory depression and reduction in brain NA utilization by clonidine, which both previously have been found to be antagonized by yohimbine. In contrast to clonidine, morphine even in high doses did not facilitate the flexor reflex activity of acutely spinalized rats. Pretreatment with protriptylin largely attenuated the circulatory depressive effects of morphine, as it has previously been found to block the corresponding effects of clonidine. Thus, the morphine-induced cardiovascular depressive effects are primarily elicited by activation of opiate receptors. However, the inhibition of brain NA neurotransmission by morphine appears critically involved in the mediation of the circulatory depression. 相似文献
87.
We are concerned in this paper with learning classification procedures from known cases. More precisely, we provide a diagnostic model that discriminate between cerebellum-pontine angle (CPA) tumors and otorhinolaryngological (ENT) disorders. Usually, in order to distinguish between CPA tumors and ENT disorders one must perform clinical-neurological examination together with expensive radiological imagery (CT and MRI). The proposed model was obtained through artificial intelligence methods and presented a good accuracy level (88.4%) when tested against new cases, considering only clinical examination without radiological imagery results. 相似文献
88.
89.
90.
The link between excessive consumption of dietary saturated fats and coronary heart disease (CHD) is now well established. Because of its high content of saturated fatty acids, the consumption of foods containing coconut oil may therefore be a risk factor for CHD. While the fatty acid composition of coconut oil is well established, relatively little is known about the other constituents of coconut: the milk, water, cream and meat fractions. In this study, we show that while the water fraction is low in lipid content, the milk contains about 24% of the fat content of oil and the cream and meat fractions about 34%. The other coconut constituents contain significant amounts of medium-chain triglycerides that are formed from fatty acids of chain length 8:0 to 14:0. It is these fatty acids, primarily 14:0, that are thought to be atherogenic. On the other hand, medium-chain triglycerides may be advantageous under some circumstances in that they are absorbed intact and do not undergo degradation and re-esterification processes. As a result, medium-chain triglycerides provide a ready source of energy and may be useful in baby foods or in diet therapy. Nevertheless, the possible negative effects of the saturated fatty acids and the absence of the essential fatty acid linolenic acid from all coconut constituents suggest that the coconut milk, oil and cream should not be used on a regular basis in adults. 相似文献