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   2585篇
  免费   149篇
  国内免费   8篇
耳鼻咽喉   12篇
儿科学   110篇
妇产科学   45篇
基础医学   270篇
口腔科学   28篇
临床医学   222篇
内科学   595篇
皮肤病学   45篇
神经病学   126篇
特种医学   194篇
外科学   324篇
综合类   334篇
一般理论   1篇
预防医学   258篇
眼科学   13篇
药学   81篇
  1篇
中国医学   5篇
肿瘤学   78篇
  2021年   15篇
  2020年   19篇
  2019年   21篇
  2018年   21篇
  2017年   22篇
  2016年   19篇
  2015年   49篇
  2014年   62篇
  2013年   74篇
  2012年   92篇
  2011年   107篇
  2010年   112篇
  2009年   95篇
  2008年   120篇
  2007年   122篇
  2006年   138篇
  2005年   120篇
  2004年   105篇
  2003年   94篇
  2002年   101篇
  2001年   88篇
  2000年   75篇
  1999年   67篇
  1998年   53篇
  1997年   43篇
  1996年   48篇
  1995年   34篇
  1994年   36篇
  1993年   17篇
  1992年   47篇
  1991年   41篇
  1990年   41篇
  1989年   39篇
  1988年   41篇
  1987年   53篇
  1986年   49篇
  1985年   47篇
  1984年   29篇
  1983年   29篇
  1982年   25篇
  1981年   17篇
  1980年   19篇
  1979年   29篇
  1978年   26篇
  1977年   19篇
  1976年   15篇
  1974年   17篇
  1973年   16篇
  1972年   13篇
  1966年   21篇
排序方式: 共有2742条查询结果,搜索用时 15 毫秒
1.
BACKGROUND: The present study was aimed to define the gender ratio, familial occurrence, age of onset, precipitating factors, clinical types, nail and joint involvement of psoriasis in childhood and adolescence in Turkey. METHODS: A total of 61 children with psoriasis under 18 years old were evaluated retrospectively, for age, gender, age of disease onset, family history, concomitant disease, the clinical type of psoriasis, clinical localization, nail and joint involvement and treatment modalities. RESULTS: Of the patients, 23 (37.70%) were boys and 38 (62.30%) were girls. Mean age was 9.28 +/- 4.02 years in girls and 11.18 +/- 3.85 years in boys (9.96 +/- 4.03 years in all children). Mean age at the onset of the disease was 6.81 +/- 4.11 years in girls and 7.03 +/- 4.28 years in boys (6.89 +/- 4.14 years in all patients). In 14 (23%) cases, a positive family history was detected. The most frequent probable triggering factors were upper respiratory tract infections (14.8%) and positive throat culture for A group ss-hemolytic streptococcus (21.3%). Frequency of emotional stress and psychiatric morbidity were 54% and 9.8%, respectively. The most frequent localizations at onset were trunk (44.3%), extremities (54.0%), and scalp (36.0%). Three children (4.9%) had a history of dissemination from psoriatic diaper rash. In total, 51 (83.6%) patients presented with psoriasis vulgaris, eight (13.1%) with generalized pustular psoriasis, and the remaining two (3.3%) with erythrodermic psoriasis. CONCLUSION: The incidence of psoriasis among dermatological patients in childhood and adolescence was 3.8%. The disease tends to appear earlier in girls than boys. The authors suggested that stress and upper respiratory infections are the most important triggering factors in childhood and adolescence psoriasis.  相似文献   
2.
3.
The role(s) of androgens in the steroidogenic regulation of human granulosa cell production of estrogen and progesterone during monolayer culture was studied. These cells were exposed in vivo to human menopausal gonadotropin and hCG gonadotropin with or without clomiphene citrate. Steroid production rates were compared between cells cultured in control medium and those cultured in medium containing a nonaromatizable androgen [dihydrotestosterone (DHT)] or an aromatizable androgen [androstenedione (A'D)]. Some cultures received A'D from 3-12 days; other cultures received DHT alone for 3, 6, or 9 days before the addition of A'D for 3 days. The effect on steroid production during the culture interval before the addition of A'D also was evaluated. Exposure to A'D increased estrogen production over 50-fold compared with that in control cells or those treated with DHT (P less than 0.001). DHT also failed to alter estrogen production when A'D was added to cultures. Furthermore, the delay in introducing A'D to the cultures for up to 9 days did not decrease subsequent estrogen production compared with that in cultures continually exposed to A'D or DHT plus A'D. Progesterone production was substantial for at least 12 days of culture and was unaffected by the presence of androgen. These results do not confirm previous studies using murine or porcine granulosa cells, which suggested that androgen receptor-dependent mechanisms were involved in increasing estrogen and/or progesterone production in vitro. Rather, they indicate that androgen may not be required to maintain aromatase capability per se in human granulosa-luteal cells previously exposed to ovulation-inducing quantities of gonadotropin.  相似文献   
4.
A total of 328 cases of infection with human immunodeficiency virus (HIV) in Western Australia in 1983-1987 was studied with respect to demographic factors, the risk profile, the clinical progression of disease, the utilization of inpatient services and trends in incidence over time. The crude incidence rates were 8.8 cases/100,000 person-years in men and 0.4 cases/100,000 person-years in women. Age-specific rates peaked at 25 to 29 years of age in men. The risk of HIV infection was associated with metropolitan residence, low socioeconomic level, and two specific occupational groups. Homosexual and bisexual men constituted 86% of all cases; the incidence rate of HIV infection in such men was approximately 1000-times higher than was the incidence rate by apparent sexual transmission in heterosexual persons. However, the proportion of cases that occurred in women or that apparently was caused by heterosexual sexual transmission increased from zero in 1983-1984 to 7.5% and 5.4%, respectively, in 1987. After two years of follow-up, 71% of preclinical (category-C) patients had developed signs, symptoms or evidence of immune dysfunction, and 12% of those patients with lymphadenopathy or with other early clinical features of disease (category-B) had progressed to the acquired immunodeficiency syndrome (AIDS). At 21 months of follow-up, the survival rate with AIDS was 9%. Patients with AIDS utilized an average of 68.9 short-stay hospital bed-days per person-year, while category-B patients used 11.5 hospital bed-days per person-year. Notifications of HIV infection increased each year from 1983 to 1986, but fell by 22% in 1987. The latter may have been as a result of chance, a screening artefact or a real reduction in the incidence rate.  相似文献   
5.
6.
7.
8.
AIMS: To determine the most appropriate regression models to use when assessing risk factors for severe hypoglycaemia and to investigate the impact of model misspecification and its clinical implications. METHODS: A total of 1229 children with Type 1 diabetes (mean age 11.7 years sd 4.1), of which 605 (49.2%) were males, were studied. Prospective assessment of severe hypoglycaemia (an event leading to loss of consciousness or seizure) was made over the 9-year period, 1992-2001. Patients were seen every 3 months and episodes of hypoglycaemia along with clinical data were recorded. Over 70% of children never experienced a severe hypoglycaemic event. Data were analysed using the Poisson regression, negative binomial, zero-inflated Poisson (ZIP) and zero-inflated negative binomial (ZINB) models. The over-dispersion and likelihood ratio statistics were calculated and the analytical methods compared. RESULTS: The Poisson regression model did not fit the data well. The negative binomial and the zero inflated Poisson and negative binomial models fitted the data better than Poisson. CONCLUSIONS: The commonly used Poisson regression models to analyse hypoglycaemia epidemiology may lead to biased parameter estimates and incorrect determination of risk factors for hypoglycaemia. We recommend the use of the negative binomial or zero inflated models to examine any risk factors associated with severe hypoglycaemia. Careful consideration must be given to the interpretation of hypoglycaemia surveys and their analysis.  相似文献   
9.
The neuroexcitatory actions of two toxicologically distinct classes of pyrethroid insecticides were characterized in rat brain synaptosomes using [3H]tetraphenylphosphonium to measure changes in synaptosomal membrane potential and by measuring the release of [3H]acetylcholine. Both type I (permethrin) and type II (deltamethrin, cypermethrin and fenvalerate) pyrethroids produced a concentration-dependent tetrodotoxin-sensitive membrane depolarization which was stereospecific for the neurotoxic isomer of each pyrethroid. Deltamethrin was the most potent and efficacious pyrethroid in these studies, with an EC50 of 30 nM and a maximal estimated membrane depolarization of 27 mV, followed by cypermethrin, fenvalerate and permethrin. The phenoxybenzyl pyrethroids also increased the spontaneous release of [3H]acetylcholine from rat brain synaptosomes, further supporting a depolarizing action of these insecticides on nerve terminal membranes. Pyrethroid-induced release of [3H]acetylcholine was tetrodotoxin-sensitive and occurred over the same concentration range as membrane depolarization. These data indicate that type I and type II phenoxybenzyl pyrethroids act potently and stereoselectively on the voltage-sensitive sodium channel to increase sodium influx into synaptic terminals producing membrane depolarization and neurotransmitter release. Furthermore, they show that pyrethroid-induced alterations in synaptosomal membrane potential is a sensitive measure of pyrethroid action on the sodium channel and of pyrethroid toxicity.  相似文献   
10.
MR using a susceptibility-weighted sequence and dynamic contrast enhancement with gadolinium demonstrated relative hyperperfusion of the right temporoparietal cortex in a patient in focal status epilepticus. A single-photon emission CT (SPECT) scan also demonstrated hyperperfusion of the right temporoparietal cortex. Perfusion MR, SPECT, and electroencephalogram normalized when the seizures ended.  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