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   244042篇
  免费   36643篇
  国内免费   3143篇
耳鼻咽喉   6227篇
儿科学   8166篇
妇产科学   4707篇
基础医学   15708篇
口腔科学   3791篇
临床医学   34048篇
内科学   67581篇
皮肤病学   9312篇
神经病学   23343篇
特种医学   10053篇
外国民族医学   23篇
外科学   54160篇
综合类   1869篇
现状与发展   72篇
一般理论   47篇
预防医学   12295篇
眼科学   4856篇
药学   8581篇
  3篇
中国医学   516篇
肿瘤学   18470篇
  2024年   724篇
  2023年   5125篇
  2022年   2178篇
  2021年   4814篇
  2020年   7087篇
  2019年   3754篇
  2018年   9281篇
  2017年   8763篇
  2016年   9930篇
  2015年   10179篇
  2014年   17820篇
  2013年   19110篇
  2012年   10245篇
  2011年   10436篇
  2010年   13483篇
  2009年   16956篇
  2008年   10127篇
  2007年   8615篇
  2006年   10811篇
  2005年   7899篇
  2004年   7518篇
  2003年   6337篇
  2002年   6493篇
  2001年   7471篇
  2000年   6618篇
  1999年   6121篇
  1998年   4736篇
  1997年   4312篇
  1996年   4134篇
  1995年   3964篇
  1994年   2599篇
  1993年   2211篇
  1992年   3129篇
  1991年   3144篇
  1990年   2534篇
  1989年   2595篇
  1988年   2316篇
  1987年   2021篇
  1986年   2040篇
  1985年   1746篇
  1984年   1308篇
  1983年   1209篇
  1982年   960篇
  1981年   788篇
  1979年   870篇
  1978年   745篇
  1977年   762篇
  1975年   705篇
  1974年   707篇
  1972年   724篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
992.
993.
A rare case of primary malignant intramedullary lymphoma, localized in the cervical part of the spinal cord, is presented. The onset of clinical symptoms was associated with herpes zoster infection. Surgery led to the histological diagnosis. The clinical investigations excluded the presence of lymphoma in other sites in the central nervous system and in the extraneural organs. Postoperative irradiation and chemotherapy effected relict of neurological symptoms.  相似文献   
994.
The relationship between primary tumor proliferative activity and clinical and pathologic characteristics was analyzed in relation to menopausal status in 32 patients with malignant or benign breast disease. The thymidine labeling index (TLI) showed significantly higher median values in the cancer patients (3.48 per cent) than in the patients with benign diseases (1.02 per cent). TLI was not significantly affected by delayed incubation at room temperature for about 1 hour. In the breast cancer patients, TLI did not significantly correlate to tumor size, the presence of axillary lymph node metastasis or pathologic nuclear grading. The only significant difference was limited to the breast cancer patients without axillary lymph node metastasis in relation to menopausal status; the TLI in the premenopausal patients (5.10 per cent) was significantly higher (p<0.05) than that in the postmenopausal patients (2.28 per cent). These data thus suggest that among premenopausal patients without axillary lymph node metastasis, those with a high TLI could be potential candidates for adjuvant chemotherapy.  相似文献   
995.
OBJECTIVE: Our objective was to determine whether the observed relaxation to lactate and other agents in placental vessels of normal pregnancies is altered in severe preeclampsia.STUDY DESIGN: Isolated placental arteries and veins from women with severe preeclampsia and uncomplicated term pregnancies were precontracted with prostaglandin F under 5% oxygen and 5% carbon dioxide with the balance nitrogen (Po2 35 to 38 torr) and then exposed to lactate (1 to 10 mmol/L, pH 7.4, n = 8 to 15), arachidonic acid (0.01 to 10 μmol/L, n = 6 to 13), nitroglycerin (1 nmol to 1 μmol/L, n = 4 to 12), or forskolin (0.01 to 10 μmol/L, n = 6 to 9). The response to lactate was also examined in placental vessels from appropriate-for-gestational-age preterm deliveries (n = 8) for comparison with a similar group with severe preeclampsia (n = 8). The t test and analysis of variance statistics were used.RESULTS: Relaxation to lactate was markedly inhibited in both placental arteries and veins of women with severe preeclampsia compared with vessels from uncomplicated term or preterm pregnancies. Responses to the other relaxing agents were not altered in the severely preeclampsia vessels.CONCLUSIONS: In severe preeclampsia absence of lactate-induced dilatation of placental vessels may contribute to the fetal complications associated with impaired blood flow and vasospasm.  相似文献   
996.
997.
998.
Abstract: The hepatitis B surface antigen (HBsAg) carrier state is associated with changes in hepatocellular function involving the cytochrome P450 (CYP) system. Among this system, CYP1A2 enzyme plays an important role in chemical carcinogenesis and in the metabolism of several drugs. We have thus investigated CYP1A2 function using two 14C-caffeine breath tests (3-methyl-14C; C3BT and 7-methyl-14C caffeine; C7BT) in 12 HBsAg healthy carriers and 8 healthy volunteers matched for 14C-aminopyrine breath test values. HBsAg carriers exhibited lower C3- and C7BT values than normal controls. This difference, however, did not reach statistical significance except for C7BT values normalised for aminopyrine breath test values. Our data thus do not support the association between viral presence and CYP1A2 dysfunction.  相似文献   
999.
We studied retrospectively 12 eyes with a solitary choroidal hemangioma in 12 patients over a period of 13 years. A peculiar, even hyperfluorescence of the tumor within the retinal venous phases occurred in all 12 cases. In all but four patients, laser therapy was performed to reduce subretinal fluid and partially destroy the tumor. Two of the three eyes without extensive retinal detachment or cystoid macular edema at the initial visit regained a final vision of 20/30 or better. The remaining 5 patients with the two major complications had a final vision of 20/80 or worse due to degenerative retinal changes. We believe that laser treatment is definitely advisable in the early stages of a circumscribed choroidal hemangioma.The study was performed at the Institute of Ophthalmology, University of Nijmegen.  相似文献   
1000.
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