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   2180篇
  免费   89篇
  国内免费   30篇
耳鼻咽喉   3篇
儿科学   95篇
妇产科学   19篇
基础医学   424篇
口腔科学   77篇
临床医学   250篇
内科学   495篇
皮肤病学   112篇
神经病学   40篇
特种医学   267篇
外科学   167篇
综合类   48篇
预防医学   76篇
眼科学   25篇
药学   140篇
中国医学   1篇
肿瘤学   60篇
  2015年   24篇
  2014年   19篇
  2013年   74篇
  2012年   23篇
  2010年   44篇
  2009年   30篇
  2008年   22篇
  2007年   44篇
  2006年   50篇
  2005年   26篇
  2004年   19篇
  2003年   26篇
  2002年   19篇
  2001年   29篇
  2000年   24篇
  1999年   33篇
  1998年   82篇
  1997年   95篇
  1996年   104篇
  1995年   70篇
  1994年   73篇
  1993年   76篇
  1992年   39篇
  1991年   36篇
  1990年   41篇
  1989年   67篇
  1988年   57篇
  1987年   49篇
  1986年   52篇
  1985年   38篇
  1984年   57篇
  1983年   28篇
  1982年   31篇
  1981年   37篇
  1980年   49篇
  1979年   25篇
  1978年   27篇
  1977年   35篇
  1976年   38篇
  1975年   37篇
  1972年   24篇
  1971年   21篇
  1970年   23篇
  1965年   50篇
  1964年   50篇
  1963年   47篇
  1962年   41篇
  1961年   40篇
  1960年   65篇
  1959年   20篇
排序方式: 共有2299条查询结果,搜索用时 15 毫秒
81.
We have tested the value of maternal plasma creatine kinase activity for diagnosing ectopic pregnancies obtained after in-vitro fertilization and embryo transfer. Plasma creatine kinase was assayed in 57 patients: 20 normal, 23 miscarriages and 14 ectopic pregnancies, for a total of 240 samples. All values were in the lower part of the normal range except only one in a miscarrying patient. A statistically significant difference was observed for a cut-off value of 45 IU/l between normal and ectopic pregnancies. However, for this cut-off point, the measurement of plasma creatine kinase activity had a sensitivity of 0.50 and a specificity of 0.76 for the diagnosis of ectopic pregnancy. The positive predictive value was 0.69. Creatine kinase activity measurements are thus of no practical value in this particular population, in which an early and specific marker of ectopic implantation would be of paramount interest. The association of human chorionic gonadotrophin (HCG) determinations and ultrasound scanning of the pelvis still remain the best paraclinical support for an early diagnosis of ectopic implantation.   相似文献   
82.
Yoo E‐H, Woo H, Ki C‐S, Lee HJ, Kim D‐K, Kang I‐S, Park P, Sung K, Lee CS, Chung T‐Y, Moon JR, Han H, Lee S‐T, Kim J‐W. Clinical and genetic analysis of Korean patients with Marfan syndrome: possible ethnic differences in clinical manifestation. Marfan syndrome (MFS) is an autosomal dominant disorder of the fibrous connective tissue caused by mutations in the fibrillin‐1 (FBN1) gene. Although clinical and genetic analyses have been performed in various populations, there have been few studies in Korea. The aim of this study was to investigate the clinical characteristics and genetic background of Korean patients with MFS. In 39 Korean patients with MFS who met the Ghent criteria, the most common clinical finding was aortic dilatation and/or dissection (94.9%), whereas only 35.9% of patients had ectopia lentis. The majority of MFS patients had fewer than four of the skeletal findings required to fulfill the major skeletal Ghent criterion for MFS. Only 21% of Korean patients had major skeletal abnormalities and most cases showed only minor skeletal involvement. FBN1 gene mutations were detected in 35 out of 39 patients (89.7%), which is similar to rates presented in the previous reports. These results suggest that some clinical features in Korean patients with MFS differed from those reported in Western MFS patients.  相似文献   
83.
OBJECTIVES: To investigate the relationship of specific nutrients and food items with oral precancerous lesions among tobacco users.
DESIGN: A population-based case-control study. SETTING: Villages in Palitana taluk of Bhavnagar district, Gujarat, India.
SUBJECTS AND METHODS: An interviewer-administered food frequency questionnaire, developed and validated for this population, was used to estimate nutrient intake in blinded, house-to-house interviews. Among 5018 male tobacco users, 318 were diagnosed as cases. An equal number of controls matched on age (±5 years), sex, village, and use of tobacco were selected.
MAIN OUTCOME MEASURES: Odds ratios (OR) from multiple logistic regression analysis controlling for relevant variables (type of tobacco use and economic status).
RESULTS: A protective effect of fibre was observed for both oral submucous fibrosis (OSF) and leukoplakia, with 10% reduction in risk per g day-1 ( P < 0.05). Ascorbic acid appeared to be protective against leukoplakia with the halving of risk in the two highest quartiles of intake (versus the lowest quartile: OR = 0.46 and 0.44, respectively; P < 0.10). A protective effect of tomato consumption was observed in leukoplakia and a suggestion of a protective effect of wheat in OSF.
CONCLUSION: In addition to tobacco use, intake of specific nutrients may have a role in the development of oral precancerous lesions.  相似文献   
84.
In 1974 we reported an inverse relationship between sinoatrial conduction time (SACT) and sinus cycle length (SCL) during sinus arrhythmia utilizing the indirect atrial premature stimulation technique for estimating SACT, However, this behavior seemed anomalous try analogy with the AV node. Subsequent to 1974, methodological considerations about and limitations of the indirect techniques for estimating SACT became apparent, making us question our former impression. When the capability to directly record sinus node electrograms was developed and established in the 1980s, we had the means to reevaluate the SACT/SCL relationship. This report presents our findings in 40 patients: the SACT/SCL relationship is direct, not inverse. Moreover, we also show that during the phasic fluctuations of sinus arrhythmia, the P-P alterations are initiated more frequently by changes in sinoatrial conduction time than by changes in sinus cycle length.  相似文献   
85.
86.
Rat platelets were labeled with tritiated diisopropylfluorophosphate(3H-DFP) during recovery from acute thrombocytopenia. The results indicated that there was significant labeling of megakaryocytes by 3H-DFPwhich, in the presence of an increased rate of platelet production, resulted inmaintenance of relatively constant values for platelet-bound radioactivity during the period of maximum platelet production and reactive thrombocytosis.Significant random loss of platelets was apparent, and, when a cohort ofyoung platelets was transfused to normal recipients, they were destroyed at anormal rate.

  相似文献   
87.
Marrow transplantation was attempted in a 13-yr-old boy with congenital hypoplastic anemia who had never responded to corticosteroid therapy. Prior to the transplant, he had received 238 transfusions, at least 12 of which were from his father. He was prepared for grafting with antilymphocyte globulin, procarbazine, and total body irradiation (1000 rads). The patient, whose red cells were Group B, then received marrow cells from his Group O, histocompatible, sister. Thereafter, reticulocytes, Group O erythrocytes, and female leukocytes appeared in the peripheral blood. Erythroid precursors were seen in the patient's marrow for the first time in his life, and all lacked fluorescent Y chromosomes. Dividing cells were all female. After initially progressing well, the patient developed interstitial pneumonia and died 55 days after the transplant. The successful erythroid graft suggested that this patient's failure to produce red blood cells was due to a defective stem cell rather than to a humoral defect, plasma inhibitor, or abnormal marrow microenvironment. It suggested further that sibling marrow may be engrafted in patients who have received multiple transfusions, even from a parent.  相似文献   
88.
89.
Cerebral edema may complicate the course of fulminant hepatic failure. Response to conventional therapy has been disappointing. We present a patient with fatal acetaminophen-induced fulminant hepatic failure, with signs and symptoms of cerebral edema, unresponsive to conventional medical therapy. Cranial decompression was carried out. A justification of the need for further evaluation of cranial decompression in such patients is presented.  相似文献   
90.
Introduction: We report the electrodiagnostic (EDX) features of 32 patients with surgically verified true neurogenic thoracic outlet syndrome (TN‐TOS). Methods: Retrospective record review. Results: We found uniform EDX evidence of a chronic axon loss process that affected the lower portion of the brachial plexus and disproportionately involved the T1 more than the C8 sensory and motor fibers. Because of this relationship, the medial antebrachial cutaneous sensory nerve (T1) and median motor (T1 > C8) study combination was abnormal in 89%, whereas response combinations that primarily assessed the C8 fibers were less frequently affected. Conclusions: The characteristic EDX features of TN‐TOS are T1 > C8 nerve fiber involvement. A comprehensive EDX examination of the lower plexus with contralateral comparison studies is imperative to diagnose this disorder accurately. Muscle Nerve 49 : 724–727, 2014  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