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   17524篇
  免费   1462篇
  国内免费   382篇
耳鼻咽喉   143篇
儿科学   146篇
妇产科学   245篇
基础医学   1081篇
口腔科学   423篇
临床医学   2215篇
内科学   916篇
皮肤病学   111篇
神经病学   471篇
特种医学   371篇
外国民族医学   2篇
外科学   4414篇
综合类   4293篇
预防医学   1329篇
眼科学   329篇
药学   2021篇
  58篇
中国医学   481篇
肿瘤学   319篇
  2024年   42篇
  2023年   280篇
  2022年   553篇
  2021年   658篇
  2020年   692篇
  2019年   589篇
  2018年   613篇
  2017年   665篇
  2016年   649篇
  2015年   654篇
  2014年   1310篇
  2013年   1170篇
  2012年   1181篇
  2011年   1201篇
  2010年   990篇
  2009年   893篇
  2008年   802篇
  2007年   864篇
  2006年   790篇
  2005年   742篇
  2004年   466篇
  2003年   417篇
  2002年   400篇
  2001年   315篇
  2000年   239篇
  1999年   212篇
  1998年   185篇
  1997年   194篇
  1996年   145篇
  1995年   167篇
  1994年   125篇
  1993年   120篇
  1992年   97篇
  1991年   117篇
  1990年   100篇
  1989年   73篇
  1988年   77篇
  1987年   84篇
  1986年   68篇
  1985年   84篇
  1984年   80篇
  1983年   58篇
  1982年   52篇
  1981年   56篇
  1980年   37篇
  1979年   18篇
  1978年   13篇
  1977年   12篇
  1976年   8篇
  1974年   6篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Thirty-seven lymphocytotoxic antisera, 27 of which were raised by immunization with skin grafts and blood from partially matched donors, were tested against cells obtained from 218 unrelated animals and 205 offspring from a colony of cynomolgus monkey (Macaca fascicularis). Evidence was obtained for the presence of at least 21 specificities defined by cluster analysis and segregation within families. Allelic relationships between 16 specificities was suggested by segregation patterns, the absence of triplets and statistical analysis of association in the unrelated population sample. The data support a two-locus model, with tentative assignment of seven specificities to the A locus and six to the B locus. That these lymphocyte alloantigens constitute the major histocompatibility complex (MHC) of the cynomolgus monkey is suggested by analogy with other known MHCs and by the increased survival times of skin grafts between paternally matched half sibs compared to haplodistinct full sibs.  相似文献   
72.
Peripheral-blood lymphocytes were primed in vitro with the mitogen phytohemagglutinin (PHA) or with allogeneic cells and their memory responses studied following sequential restimulation with either mitogen or alloantigen. Chromosome preparations were made every 12 hours following exposure to the stimulating agents. Cultures were labeled with BUdR for sister-chromatid staining of the chromosomes which provided information about the kinetics of cell growth and rates of sister chromatid exchange. Cultures containing no BUdR were used for the investigation of cell karyotypes after chromosome-banding.Following PHA as well as alloantigen restimulation, an earlier reaction of the responding cells was observed. The peak response after the first stimulation was found at 120 h with allogeneic stimulation and at 60 h with mitogen stimulation. In the second round of stimulation, the peak occurred after 48 h (allogeneic) and 36 h (PHA) and following the third stimulation after 36 h (allogeneic) and 24 h (PHA). The speed of cell growth was decreased following restimulation with either alloantigen and mitogen. In contrast to the allogeneic restimulation, the number of cells responding after PHA restimulation was decreased.No systematic numerical or structural aberration of the karyotype was detected following repeated stimulation with either alloantigen or mitogen. In this sense, the lymphocyte subpopulations selected by repeated stimulation did not differ from the starting material. On the other hand, the sister-chromatid exchange (SCE) frequency was increased following allogeneic restimulation, whereas it remained constant with PHA restimulation.  相似文献   
73.
Properties of T cells from inflammatory lesions were analysed by comparing the response of peripheral blood (PB) and synovial fluid (SF) T cells from 19 patients with a range of arthropathies to enriched allogeneic dendritic cells (DC) in a primary mixed leucocyte reaction (MLR). In 17 patients the proliferative response of SF T cells was significantly (P less than 0.05) less than that of PB lymphocytes. The reduced response of SF T cells was observed in all disease categories studied and could not be attributed to differences in cell number requirements or response kinetics. Addition of recombinant interleukin-2 enhanced the response of SF T cells in a dose-dependent manner. Cell mixing experiments suggested that active suppression was not the underlying mechanism of the poor MLR response of SF T cells. In contrast to the MLR response. SF T cells were able to mount vigorous proliferative responses to recall antigen presented by autologous antigen-presenting cells. The possibility is discussed that T cells compartmentalized at inflammatory lesions are a unique population with a diminished ability to interact with DC and respond to primary stimuli but an ability to respond to secondary antigenic challenge.  相似文献   
74.
卵巢宫内膜样腺癌的病理组织学及组织化学分析   总被引:1,自引:0,他引:1  
本文通过对24肺卵巢宫内膜样腺癌的巨检,镜及组织化学染色等结果分析,提出按该瘤所含组织成分,将其分为单纯型及混合型两大类。单纯型中分化程度不同又再分成Ⅰ,Ⅱ,ⅢⅣ级。混合型中根据所含成分又再分为腺棘癌,腺鳞癌,透明细胞腺癌型,含粘液腺癌型及含浆液腺癌型。讨论了该瘤的临床表现,发病率,组织来源,病理特征,诊断步骤及各类型与预后之间的关系。  相似文献   
75.
Systemic sclerosis (SSc) is characterized by systemic fibrosis and microvascular lesions. As TGF-beta is suggested to be related to skin fibrosis, we examined the production of TGF-beta from peripheral mononuclear cells (MNC) of SSc patients. Since anti-TGF-beta neutralizing antibody improved the defective proliferative response in autologous mixed lymphocyte reaction (AMLR) of SSc patients, TGF-beta was thought to participate in the decreased AMLR of SSc patients. Greater amounts of TGF-beta in the active as well as in the latent forms were produced during AMLR of SSc patients than that of normal subjects. It was suggested that TGF-beta excessively produced from the MNC of SSc patients might play a major role in the fibrosis of the patients during AMLR-like in vivo responses.  相似文献   
76.
The contribution of sialic acids and of N-linked sugars to the biological activity of the receptor for IL 2 has been evaluated by treating activated cells with Neuraminidase or by growing them in the presence of inhibitors of N-linked glycosylation or processing. After treatment with Neuraminidase, Con A-activated spleen cells had not lost their ability to bind IL 2. The IL 2-absorbing capability was, however, strongly reduced after trypsinisation. 6 hours after Trypsin treatment, this property was again expressed. Proliferation of the IL 2-dependent CTLL cells was normal in the presence of Swainsonine but strongly impaired in the presence of Tunicamycin. Glycosylation of the IL 2 receptor may thus be required, but integrity of the sugars is not critical.  相似文献   
77.
该研究将通过M icrosoft V isua l C 6.0和V isua l B as ic 6.0为主要的开发工具,SQL Server为数据库,采用客户端/服务器结构,设计出基于W indow s操作系统,网络环境下运行的应用程序,并将它们用于自动麻醉记录。该自动记录系统负责处理麻醉全过程中的相关病人信息,对医护现场的多种医疗设备:如监护仪、静脉输液泵、麻醉机等进行数据的实时自动采集、加工以及集成等,并在综合病人相关信息及生理参数的基础上自动输出麻醉记录单。该记录系统不仅提高了临床医师的工作效率,减低了麻醉医师的劳动强度,而且使麻醉记录更加准确和完整。  相似文献   
78.
Summary This study characterized acute peritonitis and chronic abscess formation resulting from experimental mixed anaerobic infection withBacteroides melaninogenicus andFusobacterium necrophorum. At intervals after infection liver and spleen samples were obtained, fixed, and processed for histological examination. An acute to chronic infection progressed in mice infected with this mixture of anaerobic bacteria, whereas, no infection resulted when either organism was injected alone. Acute inflammatory cell infiltrates were noted in tissue samples at 12 h postinfection. Small, discrete areas of liver cell necrosis with neutrophilic infiltrates were observed as early as 24 h. By 48 h after infection the liver parenchyma was infiltrated with both acute and chronic inflammatory cells, with moderate to severe hepatocyte degeneration recognized at 72 h. Large intrahepatic abscesses were present in the subphrenic (upper lobe) area 2 to 6 weeks after experimental infection.  相似文献   
79.
Human isolates of the highly prevalent TT virus (TTV) have been classified into five major genomic groups (1-5). The geographical distribution of the groups throughout the world is not well known. Five different PCR assays were developed in an attempt to amplify specifically TTV DNAs of each genomic group. Serum samples collected from 72 Brazilian adults (24 voluntary blood donors, 24 hepatitis B virus (HBV) carriers, and 24 human immunodeficiency virus type 1 (HIV-1)-infected patients) were tested. TTV DNA from at least one genomic group was detected in 11 (46%) blood donors, 13 (54%) HBV carriers, and 24 (100%) HIV-1 patients. All five genomic groups were detected in the three populations, with the exception of group 2 in blood donors. Some samples, negative with all five specific assays, were positive with the commonly used untranslated region (UTR) PCR system. On the other hand, TTV DNA was detected in some samples by using specific assays but not with the UTR PCR. Mixed infections with 2-5 TTV isolates from different groups were detected in 21% blood donors, 29% HBV carriers, and 71% HIV-1 patients. Fifteen PCR products (three obtained with each assay) were sequenced. Most sequences showed high (>86%) homology with those of TTV isolates belonging to their presumed groups. However, three sequences had low homology with all TTV sequences available from the DNA databanks. In conclusion, TTV isolates belonging to all five known genomic groups circulate in Brazil, and the results suggest the existence of new and as yet uncharacterised major genomic groups.  相似文献   
80.
Ameloblastic fibroma of the jaw is a rare, benign mixed odontogenic tumor, having little tendency for local invasion and a low recurrence rate. Cytologic distinction from ameloblastoma, ameloblastic fibrosarcoma, and intraosseous adenoid cystic carcinoma is necessary, in view of the different biologic behavior. A painful, slow-growing swelling of the jaw in a 5-yr-old child clinicoradiologically considered as a benign cystic lesion was aspirated. Sheets of small monomorphic epithelial cells with peripheral palisading by columnar cells were seen on cytology smears. The striking feature was central hyaline globules in some tubules. A cytologic possibility of adenomatoid odontogenic tumor was suggested. Histopathology, however, confirmed it to be an ameloblastic fibroma.  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