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   1345630篇
  免费   101054篇
  国内免费   4290篇
耳鼻咽喉   16885篇
儿科学   43811篇
妇产科学   36614篇
基础医学   199484篇
口腔科学   36093篇
临床医学   130756篇
内科学   260296篇
皮肤病学   26513篇
神经病学   112522篇
特种医学   48748篇
外国民族医学   366篇
外科学   185303篇
综合类   29033篇
现状与发展   1篇
一般理论   467篇
预防医学   115422篇
眼科学   29164篇
药学   99576篇
  6篇
中国医学   3174篇
肿瘤学   76740篇
  2021年   11069篇
  2019年   11796篇
  2018年   16503篇
  2017年   12432篇
  2016年   13395篇
  2015年   15359篇
  2014年   21048篇
  2013年   32413篇
  2012年   44717篇
  2011年   47412篇
  2010年   27386篇
  2009年   25182篇
  2008年   43159篇
  2007年   45514篇
  2006年   45637篇
  2005年   44010篇
  2004年   41938篇
  2003年   39889篇
  2002年   38659篇
  2001年   61118篇
  2000年   62806篇
  1999年   52555篇
  1998年   14708篇
  1997年   13399篇
  1996年   13248篇
  1995年   12587篇
  1994年   11740篇
  1993年   11041篇
  1992年   41796篇
  1991年   41004篇
  1990年   39658篇
  1989年   37541篇
  1988年   34766篇
  1987年   33887篇
  1986年   32330篇
  1985年   30832篇
  1984年   23205篇
  1983年   19732篇
  1982年   11851篇
  1979年   20925篇
  1978年   14913篇
  1977年   12139篇
  1976年   11955篇
  1975年   12192篇
  1974年   14881篇
  1973年   14555篇
  1972年   13429篇
  1971年   12495篇
  1970年   11558篇
  1969年   10452篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Extra-erythrocyte hemoglobin (EEH) level and total peroxidase activity (TPA) have been analysed in the blood serum and plasma of 44 patients following hyperbaric oxygenation (HBO). The levels of the parameters tested decreased after 3 HBO procedures and remained low to the end of the treatment period in the first group of patients. In the second group of patients, on the contrary, EEH and TPA levels increased after 3 HBO procedures and remained high to the end of the treatment period. In both groups of patients EEH changes correlated with TPA alterations. Possible EEH and TPA determination for the estimation and enhancement of HBO treatment efficacy is discussed.  相似文献   
992.
The purpose of the study was to compare skin blood flow by laser Doppler flowmetry (LDF) and the 133-Xenon washout technique in UVB-inflamed human skin. Six healthy subjects participated in the study. Forearm skin blood flow was measured prior to irradiation and then 8, 24, 48 and 72 h after the exposure to twice the minimal erythema dose of UVB. Baseline blood flow as measured by the 133-Xenon washout method was 5.2 (range 3.0 to 10.4) ml/100g/min and LDF flux was 3.1 (range 2.7 to 5.7) arbitrary units. Following irradiation, maximum blood flow increase as evaluated by the 133-Xenon washout was 10.8 (95% confidence interval 3.7 to 11.3) times baseline blood flow, corresponding to an absolute blood flow of 47.5 (range 33.8 to 56.3) ml/100g/min. Maximum increase after induction of inflammation as assessed by LDF was 34.6 (95% confidence interval 24.6 to 56.5) times baseline flux. The two methods showed comparable time courses in all subjects. A significant correlation between the two methods was found, Spearman's rho = 0.54, p = 0.006. The relative LDF blood flow increase was 4.2-fold (95% confidence interval 2.7 to 5.0) greater than the increase measured by the 133-Xenon washout method. These results are at variance with previous comparative studies of the two methods. Some explanations are discussed.  相似文献   
993.
994.
Kindling is a process in which episodic electrical stimulation permanently increases seizure susceptibility. One mechanism to account for a change in seizure susceptibility is some alteration in signal transduction, possibly at the level of second messenger systems. In this study, male Long-Evans rats were kindled in the amygdala, and Ca2+/calmodulin (Ca2+/CaM)-dependent protein phosphorylation was assessed at the site of the primary kindled focus using one- and two-dimensional gel electrophoresis. In vitro phosphorylation of membrane and cytosol fractions in the presence of absence of Ca2+/CaM did not differentiate kindled from nonkindled amygdaloid tissue. These results suggest that changes in Ca2+/CaM-dependent phosphorylation are not related to the mechanism(s) underlying the establishment of an amygdaloid kindled focus.  相似文献   
995.
In a study of the families of 21 schizotypal patients, we found an increased morbidity risk for schizophrenia compared with that in the families of 21 nonschizotypal patients and 42 controls. The Axis I diagnoses did not influence the distribution of the morbidity risk in the families of the schizotypal patients. If the schizotypal subjects also had other personality disorders, the morbidity risk for schizophrenia among their relatives was lower, although not significantly.  相似文献   
996.
The utility of the dexamethasone suppression test (DST) in the diagnosis of depression was examined in an outpatient sample of 29 stroke patients. Results indicated that the DST's sensitivity was 15%, its specificity was 67%, and its positive predictive value was 48%. These findings suggest that the DST yields no more information than would be gained from random assignment of the diagnosis of depression. Therefore, it is not a useful measure of mood in these patients.  相似文献   
997.
998.
999.
Programmed atrial stimulation at five atrial sites was performed to evaluate electrophysiologic atrial properties in 17 control patients (14 M, 3F, mean age 61 +/- 9 years) (Group A) and in 18 patients with paroxysmal atrial fibrillation (13 M, 5 F, mean age 61 +/- 5 years) (Group B) with normal sinus node function. The mean value of the P wave duration was similar in both groups. Programmed atrial stimulation was performed at five atrial sites: high, medium and low lateral wall, and high and low medial wall. We evaluated the following parameters: A) local conduction delay measured at the functional refractory period as the difference between A1-A2 and S1-S2 intervals; B) widening of local electrogram measured at the functional refractory period as the difference between A1-A2 interval measured at the end of each local electrogram and A1-A2 interval measured at the beginning of each local electrogram. We evaluated the mean and the maximum value of the two above-mentioned parameters; C) dispersion of effective refractory period and functional refractory period, determined as the longest minus the shortest refractory period from the range of refractory periods measured in each patient; D) the mean of effective refractory periods and functional refractory periods observed at five atrial sites. Mean and maximum local conduction delay, mean effective and functional refractory periods did not present significant differences in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
1000.
Morgan et al demonstrated that adults who consumed ready-to-eat cereals had significantly lower fat and cholesterol intakes than those who ate other foods at breakfast. Not discussed in that study was the effect of breakfast consumption habits on serum cholesterol levels. The NHANES II study of 11,864 adults was used to both verify the Morgan et al results with a different sample and to extend that research by including serum cholesterol. The analysis disclosed that serum cholesterol levels are lowest among adults eating a breakfast that includes ready-to-eat cereal and highest among breakfast skippers.  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