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   514039篇
  免费   33353篇
  国内免费   614篇
耳鼻咽喉   6894篇
儿科学   16851篇
妇产科学   13521篇
基础医学   85012篇
口腔科学   14479篇
临床医学   44349篇
内科学   93630篇
皮肤病学   12155篇
神经病学   36189篇
特种医学   18466篇
外国民族医学   63篇
外科学   77045篇
综合类   8474篇
一般理论   118篇
预防医学   38966篇
眼科学   12134篇
药学   40537篇
中国医学   1006篇
肿瘤学   28117篇
  2018年   4933篇
  2015年   4511篇
  2014年   6066篇
  2013年   9550篇
  2012年   12876篇
  2011年   14272篇
  2010年   8305篇
  2009年   7775篇
  2008年   13706篇
  2007年   14699篇
  2006年   14944篇
  2005年   14363篇
  2004年   14048篇
  2003年   13394篇
  2002年   13266篇
  2001年   24068篇
  2000年   25078篇
  1999年   20555篇
  1998年   5426篇
  1997年   4706篇
  1996年   5041篇
  1995年   4625篇
  1994年   4320篇
  1993年   4136篇
  1992年   15725篇
  1991年   16309篇
  1990年   16422篇
  1989年   15796篇
  1988年   14575篇
  1987年   14419篇
  1986年   13597篇
  1985年   12975篇
  1984年   9627篇
  1983年   8247篇
  1982年   4559篇
  1981年   4229篇
  1979年   9418篇
  1978年   6855篇
  1977年   5772篇
  1976年   5602篇
  1975年   6396篇
  1974年   7634篇
  1973年   7130篇
  1972年   6960篇
  1971年   6685篇
  1970年   6172篇
  1969年   5888篇
  1968年   5559篇
  1967年   5012篇
  1966年   4450篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
The charts of all patients hospitalized between 1978 and 1983 with proved ectopic pregnancies at Northwestern Memorial Hospital, Chicago, and Meir Hospital, Kfar-Sava, Israel, were reviewed. Eighty-four patients with ectopic pregnancies had endometrial tissue available for histologic analyses. Review of the endometrial curettings revealed that the most common endometrium associated with ectopic pregnancy was secretory (39.4%). Proliferative endometrium present 19% of the time was as common a finding as Arias-Stella phenomenon. This study shows that any type of endometrium lacking trophoblasts may be associated with an ectopic pregnancy. The lack of decidual reaction or Arias-Stella phenomenon should not alone lower the clinician's index of suspicion.  相似文献   
982.
5H-Mebendazole and some related heterocyclic methyl carbamates were synthesized and their anthelmintic activity against Caenorhabditis elegans was determined. In order to study the influence of the heteroaromatic region with regard to the carbamate moiety on biological activity, the molecular electrostatic potentials (MEP) of all structures were calculated and a structure-activity relationship (SAR) was established. The electrostatic pattern of activity includes two minima of the carbamate moiety, a third heterocyclic minimum, and a pi-electronic region.  相似文献   
983.
984.
985.
Objective   To investigate the reliability and validity of the expressed emotion (EE) measure, the Pre-school Five Minute Speech Sample (PFMSS), in child-to-child sibling relationships.
Method   A total of 106 boys aged 7–11 were recruited from 12 mainstream primary schools in North Wales. The children completed the PFMSS regarding their sibling and two self-report measures of sibling relationship: the Sibling Relationship Questionnaire (SRQ) and a Child Visual Analogue Scale (CVAS). The parents of 60 participants completed the Strengths and Difficulties Questionnaire regarding the behavioural problems of the participating child and his younger sibling.
Results   The PFMSS demonstrated good inter-rater and code–recode reliability. The significant associations between EE dimensions such as relationship, positive comments and critical comments with various components of the SRQ and CVAS provided support for the concurrent validity of the PFMSS. Significantly higher levels of Conflict and Rivalry and significantly lower levels of Warmth/Closeness on the SRQ were reported by children with high EE, demonstrating good discriminant validity for the PFMSS. There was no significant association between the child's EE profile and the behavioural difficulties of both siblings as reported by parents.
Conclusions   The study found that the PFMSS is a valid and reliable measure of child EE. Future research is needed to clarify the concurrent validity of the warmth and initial statement components of the measure as well as the association between EE dimensions and behaviour.  相似文献   
986.
987.
988.
BACKGROUND: We have seen several patients with itchy lichenified plaques located bilaterally on the elbows and/or knees and have named this condition 'psoriatic neurodermatitis' (PN). OBJECTIVE: The purpose of this study was to compare clinical and histopathological characteristics of these patients to those of patients with typical lichen simplex chronicus (LSC). METHODS: Nineteen patients with PN and 34 patients with typical LSC were included. Besides clinical dermatological evaluation, the prick test was carried out on 49 patients; the Phadiatop test on 40 patients; the patch test with European standard series on 47 patients; histopathological evaluation on 39 patients; and clinical psychiatric examination on 38 patients. RESULTS: Almost exclusively, PN was seen in females and was located on the extremities. It caused more plaques than typical LSC did. In PN, the plaques were smaller, sharper, more keratotic and less excoriated, and had fewer lichenoid papules around them. Itching was usually more severe in the evening, while resting and in a hot environment in typical LSC, but not in PN. In plaques of PN, microabscesses in the horny layer, hypogranulosis, regular acanthosis and thinning of the suprapapillary plates were more frequent, and hyperpigmentation in the basal layer was less. In patients with PN, depressive disorder was found more frequently; and generalized anxiety disorder or psychosomatic characteristics, less. There were no significant differences in the results of prick, Phadiatop and patch tests between patients with PN and those with typical LSC. CONCLUSION: In our opinion, it is most likely that the so-called PN is itchy psoriasis superimposed by LSC.  相似文献   
989.
990.
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