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   1829007篇
  免费   131648篇
  国内免费   4954篇
耳鼻咽喉   23746篇
儿科学   58083篇
妇产科学   49204篇
基础医学   261011篇
口腔科学   51539篇
临床医学   164121篇
内科学   358497篇
皮肤病学   42346篇
神经病学   141270篇
特种医学   70378篇
外国民族医学   242篇
外科学   274706篇
综合类   40528篇
现状与发展   9篇
一般理论   602篇
预防医学   132504篇
眼科学   43780篇
药学   135528篇
  7篇
中国医学   5923篇
肿瘤学   111585篇
  2021年   17283篇
  2019年   16729篇
  2018年   23790篇
  2017年   18000篇
  2016年   20413篇
  2015年   24174篇
  2014年   32441篇
  2013年   45499篇
  2012年   64094篇
  2011年   66367篇
  2010年   39307篇
  2009年   36129篇
  2008年   59613篇
  2007年   62705篇
  2006年   62424篇
  2005年   59462篇
  2004年   56793篇
  2003年   53357篇
  2002年   50909篇
  2001年   93628篇
  2000年   95345篇
  1999年   78529篇
  1998年   20674篇
  1997年   17994篇
  1996年   18070篇
  1995年   17351篇
  1994年   15781篇
  1993年   14509篇
  1992年   58227篇
  1991年   56159篇
  1990年   53723篇
  1989年   51446篇
  1988年   46808篇
  1987年   45554篇
  1986年   42858篇
  1985年   40573篇
  1984年   29785篇
  1983年   25303篇
  1982年   14198篇
  1981年   12669篇
  1979年   25883篇
  1978年   17870篇
  1977年   15193篇
  1976年   14108篇
  1975年   14792篇
  1974年   17896篇
  1973年   17180篇
  1972年   15895篇
  1971年   14614篇
  1970年   13589篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In this report, we examine the functional significance of the molecular microheterogeneity of alpha-fetoprotein (AFP). In doing so, we have taken the direct approach of purifying the naturally occurring isomeric forms of fetal-derived AFP using a preparative anion exchange column linked to an automated fast protein liquid chromatography (FPLC) system followed by parallel testing of each isolated molecular variant for in vitro immunoregulatory activity. The data obtained demonstrate the presence of seven distinct variants of AFP as defined by their retention volumes on FPLC elution profiles, by their pIs on analytical IEF gels, and by Western blot analysis. Molecular mass determination by SDS-PAGE showed each isomer to be equivalent in size to 69,000-dalton native unfractionated AFP molecules. All the immunosuppressive activity of AFP was localized to a single variant representing only 6% of the total composition of native AFP. The immunoregulating isomer termed AFP-1 was the least acidic of the seven isolated variants with a pI of 5.1 and displayed a sialic acid content of 1 mol/mol of protein. The inhibitory activity of AFP-1 could be readily measured on T cell-dependent antibody synthesis, Con A-induced stimulation of Lyt-1+23- thymocyte DNA synthesis, and lymphokine-activated NK cell activity. All other isomers were without effect in these test systems. The immunosuppressive AFP-1 isomer also displayed the strongest growth-promoting influence on cultured bone marrow lymphocytes. There was no correlation between functional activity and degree of expression of sialic acid residues on the AFP molecules. These findings demonstrate that the immunoregulating function of AFP is confined to a distinct and relatively small subpopulation of native AFP molecules and should therefore contribute to the resolution of outstanding questions regarding the structure/function relationship of this onco-fetal glycoprotein.  相似文献   
992.
The methodology of a so-called task force approach to the diagnosis is suggested. It determines the strategy of the physician's diagnostic searches in some problems occurring in the examination of patients afflicted with the given disease. The problems (stages, levels of examination) show how one should reason, i. e. they form concrete bases for clinical thinking. According to this methodology, the symptoms should be classified with separate diagnostic problems--trends or stages of the patient's examination at the stage of a probable diagnosis establishment. The task force approach is a method of analysis which prevents potential gross diagnostic errors by means of deciding the main questions (functional, pathogenetic, etc.). A well-defined wording of the above-indicated problems--concrete regularities of the clinical thinking--are of paramount importance in teaching therapy. Examples are provided of the task force approach to the diagnosis of pyelonephritis, infectious myocarditis, anemia, and some other diseases.  相似文献   
993.
994.
Chronic hiccups     
Patients with chronic hiccups should be carefully examined for an underlying disorder while receiving symptomatic treatment. Treatment includes physical maneuvers, drugs such as chlorpromazine, metoclopramide, anticonvulsants or quinidine, and other, less tested modalities such as hypnosis. Only those patients with disabling hiccups that do not respond to conservative treatment should be considered for phrenic nerve surgery.  相似文献   
995.
A lawsuit directed by parents at a day care program following an outbreak of infectious disease would most likely be based on the legal theory of negligence--the failure to exercise due care as required by circumstances. In the determination of liability for infectious diseases in child day care, the element of causation is most critical. Did the day care facility's actions or failure to act cause the harm? Another important question is whether an infectious disease can be occupational and under what circumstances. Although worker's compensation laws initially had no provisions for occupational disease, now all states recognize responsibility for them. Awareness of potential problems with legal liability and establishment of procedures to minimize risk are important for day care providers, public health officials, clinicians, and parents.  相似文献   
996.
997.
998.
Indirect evidence suggests that amphetamine (AMPH) releases dopamine (DA) from an extravesicular, cytoplasmic pool. Disruption of vesicular DA storage by reserpine has been hypothesized to increase the concentration of extravesicular DA available for release by AMPH, which is consistent with the observation that reserpine does not prevent but augments the behavioral response to AMPH. In order to more directly test this hypothesis, the in vivo microdialysis technique was used to concurrently examine the behavioral and striatal dopaminergic response to AMPH (1.25 or 2.5 mg/kg) 24 h following reserpine pretreatment (2.5 mg/kg). Reserpine decreased tissue levels of DA by approximately 90% and reduced baseline dialysate DA concentrations by approximately 80%. Reserpine augmented the behavioural effects of AMPH, particularly increasing the occurrence and intensity of stereotypies. In contrast, reserpine did not alter the amount or duration of AMPH-induced DA release. This observation confirms that DA release by AMPH does not depend on vesicular stores but is inconsistent with the hypothesis that augmentation or behaviour by reserpine results from increased striatal DA release.  相似文献   
999.
The authors compared children (ages 7-13 years) of unipolar depressed mothers with children of nondepressed psychiatric patients, of nondepressed medical patients, and of nondepressed mothers in the community. The children's adjustment was rated by clinicians on the Child Adjustment Schedule and by the mothers on the Child Behavior Checklist. The highest proportion of clinically significant problems was found in the children of the depressed mothers. However, the overlap between the problems of these children and those of the children of the nondepressed psychiatric patients calls into question the formulation that children's adjustment difficulties are specific to parental depression.  相似文献   
1000.
Although England/Wales, Italy, and the United States share a common policy of deinstitutionalization, their mental health systems differ considerably. Each country's civil commitment standards define patient eligibility criteria along one of two primary dimensions--need for treatment or degree of dangerousness. These differential selection criteria result in mental health systems serving different subgroups of the total population. The criteria in England/Wales target older women; in the United States, younger men; and in Italy, a group balanced in age and sex. Implications for the current debate on civil commitment policies are considered.  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