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   1599061篇
  免费   133590篇
  国内免费   2575篇
耳鼻咽喉   21645篇
儿科学   52924篇
妇产科学   46223篇
基础医学   227760篇
口腔科学   47187篇
临床医学   140802篇
内科学   314609篇
皮肤病学   34089篇
神经病学   130065篇
特种医学   64722篇
外国民族医学   474篇
外科学   243826篇
综合类   39710篇
现状与发展   3篇
一般理论   544篇
预防医学   122736篇
眼科学   36450篇
药学   121235篇
  2篇
中国医学   2974篇
肿瘤学   87246篇
  2018年   14771篇
  2016年   12908篇
  2015年   15033篇
  2014年   20655篇
  2013年   31363篇
  2012年   42565篇
  2011年   44765篇
  2010年   26350篇
  2009年   25313篇
  2008年   43019篇
  2007年   45251篇
  2006年   46069篇
  2005年   44689篇
  2004年   44117篇
  2003年   42200篇
  2002年   41314篇
  2001年   75701篇
  2000年   78342篇
  1999年   66404篇
  1998年   17738篇
  1997年   16344篇
  1996年   16328篇
  1995年   16023篇
  1994年   15073篇
  1993年   14219篇
  1992年   55436篇
  1991年   53777篇
  1990年   52567篇
  1989年   50842篇
  1988年   47233篇
  1987年   46563篇
  1986年   44285篇
  1985年   42844篇
  1984年   32035篇
  1983年   27566篇
  1982年   16146篇
  1981年   14436篇
  1980年   13566篇
  1979年   30462篇
  1978年   21065篇
  1977年   17766篇
  1976年   16696篇
  1975年   17575篇
  1974年   21486篇
  1973年   20673篇
  1972年   18854篇
  1971年   17772篇
  1970年   16290篇
  1969年   15269篇
  1968年   13949篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
971.
972.
Sex and racial predilection, social history, and histology were analyzed in a biopsy-proven adenocarcinoma of the lower esophagus/esophagogastric junction collected over a 5-year period in two teaching institutions with different patient populations. Adenocarcinoma occurred in 11% of patients with biopsy-proven esophageal cancer. The disease occurred only in males at one center, and in a 7:1 ratio of males to females at the other center. Clear racial predilection was seen, since 12 of 13 patients with adenocarcinoma of the esophagus were white, whereas less than 20% of patients with squamous carcinoma of the esophagus were white. The finding of Barrett's epithelium in eight of the 13 cases strongly supports the theory that in white males, Barrett's epithelium is a precursor lesion of adenocarcinoma of the esophagus/esophagogastric junction.  相似文献   
973.
Aseptic bone necrosis is a well known complication after corticosteroid treatment in adults and several hundred cases have been reported. Alterations in fat metabolism with vascular occlusion due to fat embolization, as well as microtraumata and osteoporosis are discussed as etiologic factors. In contrast, aseptic bone necrosis in relation to corticosteroid treatment is rare in children and adolescents. We therefore report 3 patients, aged from 10 to 18 years, suffering from severe aplastic anemia, meningeal relapse after acute lymphocytic leukemia and acute myelocytic leukemia respectively, who developed aseptic bone necrosis 6, 11, and 20 months following the onset of corticoid therapy. The patients survive from 28+ to 50+ months after diagnosis of their initial hematologic disease, as it can be expected today for increasing numbers of patients. We therefore believe, that aseptic bone necrosis may represent a serious therapy related complication and suggest that, diagnostic examination in patients with suspicious complaints of the hip, shoulder or knee should also exclude the possibility of a bone necrosis after leucemic relapse has been ruled out. Since radiological changes only develop several weeks to months after the onset of the clinical symptoms and because of the disabling consequences for patients, misdiagnosed at the beginning, a 99 technetium bone scan should be done as early as possible. Corticosteroids, despite their serious side effects are still being considered as a important part of hematologic therapy and are not being omitted in the near future, so that the earliest possible diagnosis of bone necrosis will remain of great importance.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
974.
Contact lens-induced corneal warpage   总被引:1,自引:0,他引:1  
  相似文献   
975.
A transfer procedure is very useful in the treatment of strabismus. The most common use of this procedure is to augment an already planned resection or recession procedure so that it can be performed monocularly to reduce an accompanying hypertropia or hypotropia or to collapse the A or V pattern when horizontal surgery is being performed for estropia or exotropia. In transfer procedures, the resultant change of deviation and cosmetic improvement is good or excellent in almost all cases. Some special transfer procedures, such as the Harada-Ito or the Jensen operation, can have dramatic effects on both comfort and change of symptoms for the patient.  相似文献   
976.
The effects of neurotransmitters or drugs on the release of endogenous dopamine (DA) and extracellular levels of its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were examined in vivo by intracerebral dialysis. A dialysis tube was implanted stereotaxically through bilateral caudate nuclei of rats and perfused with the Ringer solution. Amounts of DA, DOPAC and HVA in the perfusates were measured by high performance liquid chromatography (HPLC) with electrochemical detection. The basal level of DA was 2.76 +/- 0.64 pg/min, whereas the levels of DOPAC and HVA were 218.7 +/- 20.7 and 142.4 +/- 10.6 pg/min, respectively. Apomorphine (4 mg/kg, i.v.) reduced the efflux of DA and its metabolites. Haloperidol (0.4 mg/kg, i.v.) did not change DA release and produced only a minor increase of its metabolites. This increase of metabolites was inhibited by pargyline. Met-enkephalin (10(-4) M), substance P (10(-4) M) and acetylcholine chloride (10(-4) M) added to the perfusing medium increased the release of DA. Met-enkephalin also increased the release of DOPAC. gamma-Amino-n-butyric acid (GABA, 10(-4) M) reduced the release of DOPAC and HVA when added to the perfusing medium. Thyrotropin releasing hormone (TRH, 5 mg/kg, i.v.) increased the release of HVA. These findings indicated that different mechanisms mediated effects of neurotransmitters or drugs on the release and metabolism of DA in the rat striatum.  相似文献   
977.
978.
In this P & T Committee interview with Richard Borreson, MD, issues concerning rational therapeutics in a VA Medical Center setting are identified. Dr. Borreson discusses the frustrations the Houston VA Medical Center P & T Committee encounters in promoting prescribing practices that are therapeutically sound and yet cost-effective. Although their P & T Committee is very active and productive, Dr. Borreson suggests that more effort is needed to educate staff in the cost-effective selection of drugs. The process that the Houston VA has adopted for adding drugs to the formulary and the reporting of adverse reactions as required by the Joint Commission on Accreditation of Hospitals (JCAH) are also discussed.  相似文献   
979.
980.
This study reports the purification and characterization of a high molecular weight human breast cancer-associated antigen identified by a previously described (1,2) murine monoclonal antibody, BCD-B4. Immunohistochemical analysis indicated that BCD-B4 recognizes an antigen expressed in an altered form on the human breast carcinoma cell line, BT-20, compared to the non-malignant human mammary epithelial cell line, HBL-100. Chemical treatments and enzymatic digestions suggested that the recognized moiety was a protein. The antigenic determinant was resistant to neuraminidase and periodate treatments but was sensitive to trypsin and proteinase K. The antigen was purified by affinity chromatography and its molecular weight, determined by SDS-PAGE analysis under non-reducing conditions, was proven to be 250 Kd. Under reducing conditions, the molecule dissociated into two polypeptides of 125 and 45 Kd, respectively. Both subunits could be isolated from normal HBL-100 and neoplastic BT-20 cellular protein extracts by affinity chromatography. The higher molecular weight subunit showed; however, qualitative and quantitative differences between the two cell lines: it was expressed in greater quantity on BT-20 cells and its molecular weight was 15 Kd higher. Both subunits could also be identified by immunoblots of BT-20 cells.  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