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   255938篇
  免费   18116篇
  国内免费   1132篇
耳鼻咽喉   2828篇
儿科学   6636篇
妇产科学   4709篇
基础医学   33386篇
口腔科学   4627篇
临床医学   25882篇
内科学   54334篇
皮肤病学   3408篇
神经病学   24521篇
特种医学   8569篇
外国民族医学   11篇
外科学   38898篇
综合类   3513篇
一般理论   320篇
预防医学   21833篇
眼科学   6721篇
药学   17278篇
  6篇
中国医学   364篇
肿瘤学   17342篇
  2023年   1349篇
  2022年   2435篇
  2021年   5495篇
  2020年   3302篇
  2019年   5344篇
  2018年   6005篇
  2017年   4517篇
  2016年   5001篇
  2015年   5879篇
  2014年   8681篇
  2013年   11885篇
  2012年   18157篇
  2011年   19067篇
  2010年   10673篇
  2009年   9508篇
  2008年   16724篇
  2007年   17600篇
  2006年   17461篇
  2005年   17429篇
  2004年   16324篇
  2003年   15199篇
  2002年   14207篇
  2001年   2238篇
  2000年   1729篇
  1999年   2424篇
  1998年   3102篇
  1997年   2585篇
  1996年   2216篇
  1995年   2129篇
  1994年   1782篇
  1993年   1603篇
  1992年   1346篇
  1991年   1276篇
  1990年   1104篇
  1989年   1090篇
  1988年   1044篇
  1987年   1040篇
  1986年   1032篇
  1985年   1050篇
  1984年   1266篇
  1983年   1170篇
  1982年   1410篇
  1981年   1339篇
  1980年   1173篇
  1979年   765篇
  1978年   795篇
  1977年   669篇
  1976年   613篇
  1975年   504篇
  1974年   513篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Summary: This is the first report of the largest study of blood pressure measurement in pregnancy in a New Zealand population using standardized definitions and methodology. Over 3,800 women who delivered in an 8-month period in the Wellington region were included in the study. Blood pressure measurement and the presence of oedema and proteinuria were recorded from booking until delivery and in the puerperium. Only 2.7% of women were unable to be contacted after delivery for details on outcomes. The results established normal ranges for blood pressure throughout pregnancy. The data show that Mood pressure greater than 140/90 until 35 weeks' gestation is outside 2 standard deviations at all gestations and justifies using these measurements as the definition of hypertension in pregnancy. The fall in blood pressure in the 2nd trimester was less than 1 mm Ffg per week in both the systolic and diastolic pressures. This fall was smaller than previously recorded in other studies. Gestational hypertension was the commonest blood pressure abnormality occurring in 15.2% of the population. This represented 69% of the pregnant women with a hypertensive disorder. The overall incidence of both gestational hypertension and preeclampsia was 18.5% which is higher than reported in other parts of the world. In this study obesity was significantly associated with hypertensive disorders in pregnancy. An arm circumference of >33 cm, one of the measurements of obesity, was found in 6.8% of the study population. Even after the effect of arm circumference was taken into account, hypertensive disorders were also more common in Pacific Island women. Ankle oedema was significantly associated with the development of both gestational hypertension and preeclampsia but the incidence of oedema was noted in only 11.9% of the subjects.  相似文献   
93.
Summary Twenty-two patients with recurrent or metastatic squamous cell carcinoma of the head and neck were treated with piroxantrone 150 mg/m2 intravenously every 21 days. There were no objective responses. The 95% upper confidence bound for response is 15%. Primary toxicity was hematologic.  相似文献   
94.
. Neutrophil-mediated tissue damage has been implicated in the pathogenesis of diarrhoea-associated haemolytic uraemic syndrome (D+ HUS). This study evaluates priming and activation of the neutrophil oxidative burst in D+ HUS using chemiluminescent techniques. Peripheral blood neutrophils from 11 children with acute D+ HUS were examined. No difference was found in the oxidative burst of neutrophils from patients and controls. Serum elastase levels were measured in 8 patients and found to be significantly elevated. Although elastase results suggest neutrophil activation, chemiluminescence studies do not confirm this in the peripheral blood neutrophil. This does not support a significant role for circulating agents in priming and activating the peripheral blood neutrophil. Received August 17, 1995; received in revised form and accepted November 27, 1995  相似文献   
95.
96.
Three- and four-ring polyamides containing N-methylimidazole and N-methylpyrrole, and their hairpin-linked derivatives, bind side-by-side in the minor groove of DNA in a sequence-specific manner. The sequences recognized by side-by-side molecules are dependent on the pairings of the polyamide rings to the bases. In this study we report a mathematical model for estimating the free energies of binding for γ-aminobutyric acid-linked polyamides to 5- and 6-bp DNA sequences. The model parameters are calibrated by a least-squares fit to 35 experimental binding constants. The model performs well in cross-validation experiments and the parameters are consistent with previously proposed empirical rules of polyamide–DNA binding. We apply the model to the design of targeted polyamides, evaluating the ability of the proposed polyamides to bind to a DNA sequence of interest while minimizing binding to the remaining DNA sequences.  相似文献   
97.
Summary This study explores the effects of a calcium-deficient diet on patterns of bone remodeling, and examines regional differences in the amount of bone lost. Skeletally mature female rabbits (n=6) were fed a calcium-deficient diet (0.10% Ca2+ and 0.50% P) for 14 weeks. A separate group of rabbits (n=4) were fed a maintenance diet (1.2% Ca2+ and 0.45% P). Bone mineral content, serum calcium, and serum phosphorus were measured each week during the experimental period. Following sacrifice, the L3 vetebra, femoral head, proximal tibial metaphysis, and tibial midshaft were analyzed histomorphometrically. Rabbits had 20% less vertebral bone after only 14 weeks of a calcium-deficient diet. As in human postmenopausal osteoporosis, bone loss in calcium-deficient rabbits occurs in the trabecular bone of the lumbar spine before that in the trabecular bone of the lower extremity. Calcium-deficient diets alone do not lead to increased osteoid volume or thickness. Because bone loss is relatively rapid and because the pattern of loss is similar in some respects to that found in humans, adult rabbits may provide an attractive model of calcium deficiency osteoporosis in a skeletally mature mammal in which remodeling is predominant over modeling.  相似文献   
98.
99.
100.
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