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   2232篇
  免费   208篇
  国内免费   2篇
耳鼻咽喉   5篇
儿科学   164篇
妇产科学   74篇
基础医学   333篇
口腔科学   30篇
临床医学   234篇
内科学   316篇
皮肤病学   26篇
神经病学   153篇
特种医学   45篇
外科学   239篇
综合类   53篇
一般理论   3篇
预防医学   161篇
眼科学   38篇
药学   185篇
中国医学   1篇
肿瘤学   382篇
  2021年   23篇
  2020年   16篇
  2019年   18篇
  2018年   39篇
  2017年   31篇
  2016年   26篇
  2015年   34篇
  2014年   56篇
  2013年   65篇
  2012年   85篇
  2011年   81篇
  2010年   70篇
  2009年   52篇
  2008年   75篇
  2007年   63篇
  2006年   92篇
  2005年   109篇
  2004年   97篇
  2003年   92篇
  2002年   59篇
  2001年   71篇
  2000年   66篇
  1999年   69篇
  1998年   33篇
  1997年   38篇
  1996年   32篇
  1995年   22篇
  1994年   23篇
  1993年   30篇
  1992年   47篇
  1991年   51篇
  1990年   61篇
  1989年   67篇
  1988年   54篇
  1987年   48篇
  1986年   52篇
  1985年   41篇
  1984年   44篇
  1983年   35篇
  1982年   24篇
  1981年   24篇
  1980年   16篇
  1979年   23篇
  1978年   34篇
  1977年   13篇
  1976年   20篇
  1975年   14篇
  1974年   24篇
  1973年   17篇
  1967年   16篇
排序方式: 共有2442条查询结果,搜索用时 15 毫秒
1.
Stuart Cathcart  BA    Donald Pritchard  PhD 《Headache》1998,38(3):214-221
An exploratory study was conducted examining arousal-related moods and episodic tension-type headache. Twelve subjects meeting International Headache Society criteria for episodic tension-type headache and 12 headache-free controls recorded headache activity and mood eight times daily for 14 consecutive days. Moods were measured using the Activation-Deactivation Adjective Check List, a self-report list that subjectively represents general arousal along two dimensions of Tension and Energy. Headache subjects had higher Tension levels than controls even in the absence of pain, and greater variation in this dimension as well. Within the headache group, Tension during pain-free periods was significantly lower than when experiencing headache, and was correlated with headache activity. The results were taken to support Thayer's (1989) biopsychological model of mood and arousal, and are discussed in terms of the model's heuristic value for general arousal and headache research.  相似文献   
2.
The history and epidemiology of bovine tuberculosis in cattle herds in East Sussex are described. Since 1960, following the compulsory eradication scheme for tuberculosis, the incidence of herd infection has been low. The epidemiological features of herd infection have been sporadic incidents, with only small numbers of cattle becoming infected in the majority of incidents. There was no evidence of endemic Mycobacterium bovis infection in the cattle population in East Sussex in recent years, but a low risk of infection for cattle on the South Downs, from badgers, was apparent.  相似文献   
3.
4.
5.
6.
Background: The placental transfer of the a2 receptor agonist clonidine, earlier used as an adjuvant in obstetric epidural analgesia, was compared with the transfer of the newer and more %-selective agonist dexmedetomidine.
Methods: Term placentas were obtained immediately after delivery with maternal consent and a 2-hour recycling perfusion of a single placental cotyledon was performed. Disappearance from the maternal circulation, accumulation in placental tissue and appearance in the fetal circulation of clonidine or dexmedetomidine with the reference compound antipyrine were followed in 4 experiments for both drugs.
Results: At 2 hours the percent dexmedetomidine found in the fetal circulation was 12.5 (SD 5.1)%, while 48.1 (SD 20.3)% was found in the perfused placental cotyledon. A higher mean clonidine than dexmedetomidine concentration was achieved in the fetal circulation (1.90 vs. 0.56 nmol/l, P <0.05). At 2 hours the percent clonidine found in the fetal circulation was 22.1 (SD 2.4)% ( P <0.05), while 11.3 (SD 3.3)% ( P <0.05) was re tained in the perfused placental cotyledon. The transfer indexes, describing maternal-to-fetal transfer of dexmedetomidine and clonidine normalized with the transfer of antipyrine, were 0.88 (SD 0.07) and 1.04 (SD 0.08) respectively ( P <0.05).
Conclusions: Dexmedetomidine disappeared faster than clonidine from the maternal circulation, while even less dexmedetomidine was transported into the fetal circulation. This was due to its greater placental tissue retention, the basis for which probably is the higher lipophilicity of dexmedetomidine.  相似文献   
7.
Depression and smoking in pregnancy in Scotland.   总被引:6,自引:1,他引:5       下载免费PDF全文
OBJECTIVE--The aim was to examine the association between depressive symptoms and smoking in pregnancy and to investigate the part played by social and psychosocial factors. SETTING--A single Glasgow hospital. DESIGN--Prospective survey by postal questionnaires at 20 and 30 weeks' gestation. PARTICIPANTS--A total of 395 women (69% of the 572 eligible) parity 1 who booked for delivery between November 1988 and February 1990 took part. MEASUREMENTS--Depressive symptoms were measured using the Hospital Anxiety and Depression Scale. Smoking was self reported. The Life Events Inventory and measures of role specific strain and stress in domestic roles were used to assess psychosocial well being. MAIN RESULTS--Smokers were more likely than non-smokers to experience depressive symptoms at 20 and 30 weeks' gestation and on both occasions. The excess risk remained substantial and significant after adjustment for social and psychosocial factors. CONCLUSIONS--Smoking is a significant risk factor for depression in pregnancy. The association of smoking with depression and psychosocial difficulty represents a major problem for interventions intended to reduce smoking in pregnancy.  相似文献   
8.
One hundred thirty-one children underwent rigid bronchoscopy under general anesthesia for suspected aspirated foreign bodies. There were 79 boys and 52 girls, with a mean age of 2.1 years. Physical examination showed decreased breath sounds (n = 130) and wheezing (n = 119) over the affected site. Chest roentgenograms were diagnostic or suggestive of aspirated foreign bodies in 127 cases (97%). Radiopaque lesions were noted on roentgenograms in ten cases. Four infants had a preoperative hypoxic arrest. Two patients had negative results of bronchoscopy (1.5%). Extraction of the aspirated foreign body was carried out at laryngoscopy in two patients and by forceps under direct vision at bronchoscopy in 97 patients. A Fogarty catheter was used in 12 cases. Postendoscopic complications included fever (n = 27), pulmonary infiltrate (n = 11), ventilatory support (n = 4), and pneumothorax (n = 2). Rigid bronchoscopy for aspirated foreign body in children is a safe, effective, and sometimes life-saving procedure. Morbidity is low and mortality is zero.  相似文献   
9.
This paper outlines the synthesis of selected acid mimics of the non-peptide CCK-B selective antagonist CI-988, 1. CCK-B and CCK-A binding affinities of these analogues are described and their CCK-B affinity and selectivity rationalized by consideration of the pK(a) values, charge distribution, and geometry of the respective acid mimics. Several of the compounds have CCK-B binding affinities similar to the parent carboxylic acid 1 (CCK-B, IC50 = 1.7 nM; pK(a) = 5.6) and span a pK(a) range of less than 1 (sulfonic acid 27) to greater than 9.5 (5-thio-1,2,4-triazole 24). Among the more active compounds synthesized are tricyclo[3.3.1.1(3,7)]dec-2-yl [R-(R*,R*)]-[2-[[2-[[(3-hydroxy-5-isoxazolyl)acetyl]-amino]-2- phenylethyl]amino]-1-(1H-indol-3-ylmethyl)-1-methyl-2-oxoethyl+ ++]carbamate (15), tricyclo[3.3.1.1(3,7)]dec-2-yl [R-(R*,R*)]-[1-(1H-indol-3-ylmethyl)-1-methyl-2-oxo-2-[[2-[(1-oxo- 3-sulfopropyl)amino]-2-phenylethyl]amino]-ethyl]carbamate, monosodium salt (27), and tricyclo[3.3.1.1(3,7)]dec-2-yl [R-(R*,R*)]-[1-(1H-indol-3-ylmethyl)-1- methyl-2-oxo-2-[[2-[[(1H-1,2,4-triazol-5-ylsulfinyl)acetyl]a mino]-2-phenylethyl]amino]ethyl]carbamic acid (34) which have CCK-B binding affinities of IC50 = 2.6, 1.3, and 1.7 nM, CCK-A/-B ratios of 650, 780, and 550 and pK(a) values of 6.5, less than 1, and 7.0, respectively.  相似文献   
10.
MicroRNAs (miRNAs) have recently emerged as being essential for development and for the control of cell proliferation/differentiation in various organisms. However, little is known about miRNA function and mode of action at the cellular level. We have designed a miRNA loss-of-function assay, based on chemically modified locked nucleic acids (LNA) antisense oligonucleotides and usable in tissue culture cells. We show that LNA/DNA mixed oligonucleotides form highly stable duplexes with miRNAs in vitro. Ex vivo, the target miRNA becomes undetectable in cells transfected with the antisense oligonucleotide. The effect is dose-dependent, long-lasting, and specific. Moreover, using a reporter assay, we show that antisense LNA/DNA oligonucleotides inhibit short non-coding RNAs at the functional level. Thus LNA/DNA mixmers represent powerful tools for functional analysis of miRNAs.  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