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   23714篇
  免费   1721篇
  国内免费   961篇
耳鼻咽喉   111篇
儿科学   274篇
妇产科学   313篇
基础医学   4999篇
口腔科学   296篇
临床医学   2347篇
内科学   4181篇
皮肤病学   446篇
神经病学   525篇
特种医学   416篇
外国民族医学   10篇
外科学   2664篇
综合类   3607篇
现状与发展   8篇
预防医学   1179篇
眼科学   172篇
药学   1193篇
  2篇
中国医学   245篇
肿瘤学   3408篇
  2024年   26篇
  2023年   307篇
  2022年   450篇
  2021年   832篇
  2020年   665篇
  2019年   658篇
  2018年   664篇
  2017年   641篇
  2016年   668篇
  2015年   737篇
  2014年   1122篇
  2013年   1211篇
  2012年   1011篇
  2011年   1294篇
  2010年   1028篇
  2009年   1035篇
  2008年   1107篇
  2007年   1241篇
  2006年   1126篇
  2005年   1081篇
  2004年   954篇
  2003年   821篇
  2002年   862篇
  2001年   758篇
  2000年   675篇
  1999年   603篇
  1998年   558篇
  1997年   533篇
  1996年   449篇
  1995年   353篇
  1994年   394篇
  1993年   338篇
  1992年   269篇
  1991年   233篇
  1990年   266篇
  1989年   175篇
  1988年   170篇
  1987年   133篇
  1986年   111篇
  1985年   195篇
  1984年   145篇
  1983年   107篇
  1982年   91篇
  1981年   80篇
  1980年   62篇
  1979年   52篇
  1978年   38篇
  1977年   24篇
  1976年   23篇
  1971年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Anti-Ro sera immunoprecipitate Ro ribonucleoproteins (RNPs) from human cell extracts. Ro RNPs are biochemically heterogeneous particles whose functions are unknown and whose exact composition remains controversial. In addition to 60-kD Ro and to La proteins, a 52-kD polypeptide (p52) has been proposed to be a stable component of the Ro RNPs. To confirm the immunological studies supporting this hypothesis, we have biochemically purified Ro RNPs from HeLa cells using non-denaturing conditions. Ro RNPs segregated into three distinct populations, one of which only contained hY5 RNA (RohY5 RNPs). No p52 co-purified with Ro RNPs. Despite the absence of p52, purified Ro RNPs had biochemical and immunological properties identical to those of unfractionated Ro RNPs. Many anti-Ro sera only recognize p52 in immunoblots, and are said to be monospecific anti-p52. Preincubation with purified RohY5 RNPs (free of p52) of all human anti-Ro (including so-called monospecific anti-p52) sera abolished their capacity to immunoprecipitate Ro RNPs from unfractionated HeLa cell extracts. Conversely, preincubation of anti-Ro sera with purified p52 protein specifically inhibited recognition of p52 in immunoblots, but did not interfere with immunoprecipitation of Ro RNPs. Our data demonstrate that anti-p52 antibodies do not target intact Ro RNPs, nor do they target the native 60-kD Ro protein. Contrary to previous reports, p52 protein is not a stable component of antigenically intact Ro RNPs.  相似文献   
32.
Macrophages, dendritic cells or B lymphocytes have been shownto play a major role in the presentation of soluble antigensto CD4+ T cells. In contrast, the capacity of these cells topresent particulate antigens such as bacterial or parasiticantigens to T cells remains controversial. To investigate thisquestion, well defined particulate antigens were prepared bycovalent linkage of proteins or peptides to 1 µm in diametersynthetic microspheres. The T cell immunogenicity of such particulateantigens was analyzed in vitro and in vivo. In vitro, a solubleprotein such as hen egg lysozyme (HEL) coupled to beads stimulateda strong proliferative T cell response of lymph node cells fromHEL-primed mice or of specific T cell hybridomas. HEL coupledto beads was presented to the specific T cell hybridomas bysplenocytes or by peritoneal macrophages, but not by lymphomaB cells. Immunization of mice with several different proteinantigens or with a synthetic peptide covalently linked to beadsinduced strong CD4+ T cell responses in the absence of adjuvant.The strong in vivo immunogenicity of proteins coupled to beadsdid not result from a non-specific adjuvant effect of beadssince covalent linkage of the antigen to beads was strictlyrequired to induce T cell responses in the absence of adjuvant.In vivo treatment by carrageenan showed that macrophages arerequired for the in vivo stimulation of T cell responses bythese particulate antigens. Thus, these results demonstratedthe role of phagocytic cells, especially macrophages, for invivo presentation of particulate antigens. These particulateantigens represent an interesting approach for the developmentof new vaccines, and for the in vivo analysis of the role ofvarious antigen presenting cells in T cell activation and differentiation.  相似文献   
33.
PROBLEM: There is substantial data that support the efficacy of paternal leukocyte immunization (PLI) for the treatment of alloimmune mediated miscarriage; however, there is confusion regarding the laboratory test that should be performed to determine levels of maternal anti-paternal leukocyte antibodies (MAPLA). METHOD: Popular methodologies employed include: 1) microcytotoxicity (MCX), 2) mixed lymphocyte culture (MLC), and 3) cell flow cytometry crossmatch (FCXM). Cell flow cytometry crossmatch correlates well with the more difficult MLC assay although the former proves the more sensitive study. This work compares the MCX assays with FCXM. The study group consisted of ten women who had a history of three or more spontaneous abortions (SABs). All ten had very low levels (<10%) of MAPLA as measured by FCXM. Following PLI all subjects demonstrated elevated levels (>50%) of MAPLA by FCXM. At 12 weeks gestation, sera were simultaneously measured for MAPLA by MCX and FCXM. RESULTS: Although all ten patients had very high levels of MAPLA by FCXM during pregnancy, five of ten had antibodies to HLA Class I and two of ten had antibodies to HLA Class II paternal antigens by MCX. Furthermore, all patients who were positive by MCX to paternal Class I antigens were also positive to Class I antigens not seen in either parent. Both patients who were positive by MCX to paternal Class II antigens were also positive to maternal Class II antigens. Notable is that all ten women eventually delivered healthy infants. CONCLUSION: Based on this preliminary study, the MCX assay is neither sensitive or reliable enough to determine the need and/or to monitor the effectiveness of PLI. Flow cytometry should be the modality of choice when determining the need for alloimmunotherapy and to monitor the effectiveness of treatment.  相似文献   
34.
含化复方新诺明引起过敏性休克一例患者,女,30岁,因咽峡炎于1992年8月7日晚10时自行含化复方新诺明(广州白云山制药厂)两片、约7分钟后,出现全身搔痒,当即肌注苯海拉明20mg,静推10%葡萄糖酸钙10ml,旋即全身泛起荨麻疹,奇痒难忍,眼睑轻度水肿,嘴唇发麻,咽部“发紧”,发音困难,烦躁,立即给予吸氧,静推地塞米松10mg,皮下注射肾上腺素0.5mg,与此同时,患者脸色苍白、鼻尖、未梢发凉,口唇紫绀,时吸暂停,意识丧失,脉搏140次/分,细数,血压测不到,再次给予皮下注射肾上腺素0.5mg,静点地塞米松15mg,并给予扩容、纠酸,约一分钟后,欲行气管切开时,患者呼吸渐恢复、继而意识清楚,紫绀减轻,血压10/16kPa,遂休克纠正。复方新诺明片致过敏性休克者尚属少见,该患者有青霉素过敏史,局部用药又易致过敏,考虑喉头痉挛与药物含化有关。(长治市人民医院王爱军,崔文华,郭天然)含化复方新诺明引起过敏性休克一例@王爱军,崔文华,郭天然$长治市人民医院  相似文献   
35.
Hepatocyte regeneration has been widely investigated, with the mitotic index and the incorporation of [3H]thymidine being used as regeneration markers. We focused on the induction of DNA replication enzymes, particularly DNA polymerases (pol) α, δ, and ε. Using rat models, we have shown that the activity of pol α in crude liver extract well represents the regenerating capacity of hepatocytes. Using pol α as an indicator, we analyzed liver regeneration in rat models under various conditions: obstructive jaundice, external or internal biliary drainage, and the obstruction of portal vein branches. It has been revealed that the ligation of the common bile duct alone induces a certain amount of hepatocyte proliferation. It was striking that external biliary drainage suppressed regeneration capacity in cholestatic rat liver after partial hepatectomy. The strong regeneration in nonligated lobes induced by portal branch ligation was similar to the liver regeneration seen after partial hepatectomy with respect to the induction of DNA polymerases. Taken together, the aspects of DNA replication, particularly the induction of DNA polymerases, may contribute to shedding new light on the regeneration of human liver. This work was supported in part by a Grant-in-Aid for General Scientific Research and for Cancer Research from the Ministry of Education, Science and Culture, Japan, and by grants from the Uehara Memorial Foundation  相似文献   
36.
采用斑点免疫金银染色(Dot-IGSS)试验对4种日本血吸虫抗原的敏感性及特异性进行比较。结果显示粗提成虫抗原(AWA)、尿素溶解性成虫抗原(JWU)、硫酸铵沉淀成虫抗原(AW)和可溶性虫卵抗原(SEA)检测40例日本血吸虫病人血清抗体的敏感性均达100.0%,40例正常人血清的可疑阳性反应分别为2.5%、0、2.5%和0,40例肝吸虫病人血清的可疑交叉率分别为2.5%、0、2.5%和0,表明在高敏感的IGSS检测系统中,粗提成虫抗原的敏感性和特异性与部分纯化者和虫卵抗原无显著性差异(P>0.05)。  相似文献   
37.
We have devised assays to detect both circulating alloantibodies to platelets (indirect assay) and platelet-association IgG and IgM (direct assay) using a flow cytometric technique. A variety of patients with immune thrombocytopenia were studied. Employment of a confocal lens in the flow cytometer increased the discrimination power of the instrument. Patients with autoimmune thrombocytopenia (idiopathic thrombocytic purpura [ITP], systemic lupus erythematosus (SLE), lymphoma, leukemia, and drug-induced thrombocytopenia showed a significant increase in platelet-associated antibody. Circulating antibodies to platelets (alloantibodies) were demonstrated in cases of platelet refractoriness and neonatal isoimmune purpura. Day-today precision of the assays ranged from 3% to 6% (coefficient of variation). No interference was shown in the presence of hemoglobin (5 g/L), triglycerides (10 g/L), or polyclonal and monoclonal immunoglobulinemia (50 g/L: IgG, IgA, IgM). The sensitivity of the direct assay was 500 attograms of IgG or IgM platelet.  相似文献   
38.
Background: Oncogenes and other molecular tumor markers that predict tumor aggressiveness may allow individualization and optimization of surgical therapy of intermediate-thickness malignant melanoma. We examined the expression of selected markers, including the HLA-DR antigen, the heat shock protein-70 (HSP-70), and the c-myc oncogene in primary melanoma and regional nodes and related these findings to metastatic potential and survival. Methods: Forty patients with primary melanoma (1.5–4.0 mm) were studied, all of whom had prophylactic lymph node dissection and were followed for 18 months to 7 years. The primary tissue and nodes were examined using immunohistochemical techniques for the presence of HLA-DR antigen and HSP-70 protein and the expression of the c-myc oncogene. Results: Of 40 patients, there were 23 with lesions 1 to 2.9 mm thick and 17 with lesions 3 to 4 mm thick. Nodal metastases were present in 25 of the 40 patients who had elective node dissection. HLA-DR antibody stained the primary tumor in 10 patients (25%), but there was no correlation with survival in this group. HLA-DR antibody stained the stroma and cellular infiltrates surrounding the primary tumor in 28 of 40 patients; in this group there was a correlation of HLA-DR staining of the peritumoral stroma with improved survival overall. HLA-DR staining of the peritumoral stroma also influenced survival when patients were stratified by tumor thickness groups 1 to 2.9 mm and 3 to 4 mm and presence of nodal metastases. HSP-70 was demonstrated in the primary tumor in 25% of patients, who were also shown to have significantly improved survival when compared with those whose primary tumor did not stain with HSP-70. C-myc was expressed in the primary tumor in 25%, but showed no correlation with survival. None of these proteins correlated with or predicted the presence of nodal metastases. Conclusion: We conclude that the use of specific molecular-oncogene markers in intermediate-thickness primary melanoma may identify patients at high risk for conventional treatment failure and reduced survival who may profit from more aggressive surgery, adjuvant therapy, or both.Presented at the 48th Annual Cancer Symposium of The Society of Surgical Oncology, Boston, Massachusetts, March 23–26, 1995.  相似文献   
39.
应用放射免疫测定法,对20例胃肠癌患者进行了血清癌胚抗原(CEA)测定,并应用免疫组化法对其中16例癌组织中的CEA进行了检测.检测结果,血清CEA阳性6例,癌组织CEA阳性9例.低分化癌的血清CEA显著高于高分化癌(P<0.05).血清CEA与癌灶部位、癌组织CEA与分化程度及血清CEA均无关(P>0.05).提示血清CEA的含量与癌组织的分化程度有关,血清CEA与癌组织内的CEA无平行关系.作者并对其机制及检测CEA的意义进行讨论.  相似文献   
40.
增殖细胞核抗原及nm23在胃癌中的表达及意义   总被引:2,自引:0,他引:2  
目的 :探讨增殖细胞核抗原 (PCNA)及nm2 3基因在胃癌中的表达及其与生物学行为的关系。方法 :应用免疫组化SP法研究 85例胃癌手术标本中PCNA及nm2 3基因的表达。结果 :在 85例胃癌中PCNA、nm2 3的总阳性表达率分别为 5 2 9% (4 4 / 85例 )和 4 4 .7% (38/ 85例 ) ,PCNA及nm2 3在胃癌中的表达与其淋巴结转移、浸润深度、分化程度有关 (P <0 0 5 ,P <0 0 1 ) ;PCNA与分化程度无关 ,P >0 0 5。结论 :PCNA及nm2 3参与了胃癌的发生、发展、浸润及转移  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