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   1521343篇
  免费   110048篇
  国内免费   1989篇
耳鼻咽喉   20131篇
儿科学   50237篇
妇产科学   43747篇
基础医学   226710篇
口腔科学   41267篇
临床医学   139803篇
内科学   294768篇
皮肤病学   32846篇
神经病学   120860篇
特种医学   56738篇
外国民族医学   302篇
外科学   219225篇
综合类   32498篇
现状与发展   4篇
一般理论   725篇
预防医学   123648篇
眼科学   34200篇
药学   110698篇
  7篇
中国医学   2691篇
肿瘤学   82275篇
  2019年   12306篇
  2018年   16942篇
  2017年   12861篇
  2016年   14100篇
  2015年   16237篇
  2014年   22297篇
  2013年   34282篇
  2012年   46102篇
  2011年   48865篇
  2010年   28771篇
  2009年   27381篇
  2008年   45734篇
  2007年   49030篇
  2006年   48489篇
  2005年   47260篇
  2004年   45390篇
  2003年   43437篇
  2002年   41931篇
  2001年   66676篇
  2000年   67913篇
  1999年   57238篇
  1998年   16026篇
  1997年   14583篇
  1996年   14867篇
  1995年   14013篇
  1994年   13100篇
  1993年   12244篇
  1992年   45006篇
  1991年   44561篇
  1990年   43224篇
  1989年   41898篇
  1988年   38723篇
  1987年   37830篇
  1986年   36082篇
  1985年   34189篇
  1984年   25927篇
  1983年   22594篇
  1982年   13441篇
  1979年   24664篇
  1978年   18060篇
  1977年   15092篇
  1976年   13970篇
  1975年   15187篇
  1974年   18469篇
  1973年   18241篇
  1972年   17158篇
  1971年   16074篇
  1970年   15218篇
  1969年   14255篇
  1968年   13431篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
BACKGROUND: Graft-vs.-host disease (GVHD) is the major cause of morbidity and mortality in patients undergoing allogeneic Bone Marrow Transplantation (BMT). The aim of our study was to identify the most relevant histological features for diagnosis of chronic Graft-vs.-Host Disease (cGVHD) in oral mucosa and minor salivary glands of 25 patients, as well as to evaluate the immunophenotype of the inflammatory cells. METHODS: Sixteen patients that were submitted to allogeneic BMT but did not present cGVHD were selected as a control group. The sections were studied on H & E and CD68, CD45, CD4, CD8, CD20 staining. RESULTS: The most frequent histologic findings in oral mucosa at the day of diagnosis of cGVHD were: hydropic degeneration of the basal layer of the epithelium, apoptotic bodies, lymphocytic infiltration, and focal or total cleavage between the epithelial and connective tissue. In the labial salivary glands (LSG), lymphocytic infiltration, acinar loss and fibrosis were the main alterations. Cytotoxic CD8-T cells and macrophages were predominant both in the epithelium and connective tissue, as well as in minor salivary glands. CONCLUSIONS: Histological features were useful in the diagnosis of oral cGVHD. It is suggested that CD8-T cells and macrophages play important role in the pathogenesis of the disease.  相似文献   
962.
BACKGROUND: The hamster cheek-pouch carcinogenesis model is a well-known animal system that closely mimics the development of premalignant and malignant lesions in human oral cancer. Our aim was to numerically characterize the premalignant and malignant lesions and expressions of field cancerization in this model using ploidy as the end-point. METHODS: To study the DNA content and proliferation status of the cells in this model we assessed the Feulgen reaction and the immunohistochemical reaction for 5-bromo-2-deoxiuridine (BrdU) in different histological areas of serial tissue sections of the cheek pouches of animals injected with BrdU. RESULTS: Ploidy values were higher in cancerized epithelia with no unusual microscopic features (NUMF), in preneoplastic and tumor areas than in control epithelia. The aneuploidy index was higher in NUMF areas than in control and differed significantly from control in preneoplastic areas and carcinoma. CONCLUSIONS: The unexpected alteration in DNA content observed in NUMF epithelia is of great relevance as a biomarker of field cancerized areas.  相似文献   
963.
964.
965.
With their unique perspectives in the identification, design, promotion, and evaluation of cancer patient education programs and services, the National Cancer Institute and the American Cancer Society have the abilities to meet a wide variety of cancer patient education needs. With federal support and connections to national organizations and the comprehensive and clinical cancer center networks, the National Cancer Institute has access to nationwide experts in medical care and the resources to develop, design, and promote quality, state-of-the-art education programs. The American Cancer Society, with its strong volunteer community base, can pull together local expertise and collaborate with local organizations to meet the special needs of local population groups. In addition, the American Cancer Society volunteer committees have the flexibility to individualize programming and resources to answer specific patient/family education problems. As the number of people affected by cancer continues to raise, and as organizations realize the need to maximize their resources with collaborative efforts, the National Cancer Institute and the American Cancer Society are challenged to focus their energies on the patient education initiatives that build upon and combine their unique strengths.  相似文献   
966.
Benzene is metabolized to one or more hematotoxic species. Saturation of benzene metabolism could limit the production of toxic species. Saturation of phase II enzymes involved in the conjugation of the phenolic metabolites of benzene also could affect the hematotoxicity of benzene. To investigate the latter possibility, we exposed male Swiss mice, via the inhalation route, to various concentrations of benzene for 6 h per day for 5 days. Following termination of the final exposure the mice were killed and the levels of phenylsulfate and phenylglucuronide in the blood determined. Spleen weights were recorded and the number of white blood cells counted. At low benzene exposure concentrations phenylsulfate is the major conjugated form of phenol in the blood. At high exposure concentrations, phenylglucuronide is the predominant species. The reductions in spleen weight and white blood cell numbers correlated with the concentration of phenylsulfate in the blood, but are most probably not causally related.  相似文献   
967.
P E Granum  M Richardson 《Toxicon》1991,29(7):898-900
Chymotrypsin treatment of the enterotoxin from Clostridium perfringens results in the loss of 36 amino acids from the N-terminus and 3 amino acids from the C-terminus. This processing results in a 3.2 fold increase in activity on Vero cells, which is close to what had been found for trypsin treatment following the loss of 25 amino acids from the N-terminus.  相似文献   
968.
The contributors performed a study of the blastomogenic properties of the heavy high vanadium oil processed at different temperatures. Skin applications of the oil and oil products in hybrid mice induced skin tumours in 27.5 (48.7%), pregastric--6.4 (7.6%), genital--15.4 (21.1%) cases. It was established that high temperatures of oil sublimation increased the benzopyrene contents and the oil products' blastomogenic activity.  相似文献   
969.
The aim of this study was to evaluate the public opinion towards the possible replacement of ration cards by cash payment and to investigate the effect of partial termination of food price subsidy programme on food consumption by families from different income brackets. A purposive sample of 300 families from Alexandria Governorates were interviewed to assess the attitude of the consumer towards the possible termination of current food subsidy programme. After one year, during which the subsidy programme was reduced, a follow up sample of 240 were interviewed. The results show that a large proportion of the families prefer the continuation of the current programme (80-81.2%), meanwhile, around 90% of them believed that subsidized foods do not reach the target group. The data show that subsidized meat and poultry are consumed by high income families while frozen subsidized fish was mostly consumed by poor families. The partial termination of the subsidy programme forced the families to reduce their consumption from sugar, tea, oil, and rice. During the second phase of the study. However the results show that high income families were least affected by the partial termination of the subsidy programme.  相似文献   
970.
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