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   190517篇
  免费   17388篇
  国内免费   9521篇
耳鼻咽喉   2556篇
儿科学   4064篇
妇产科学   2100篇
基础医学   34494篇
口腔科学   6374篇
临床医学   15327篇
内科学   25435篇
皮肤病学   4719篇
神经病学   11640篇
特种医学   4306篇
外国民族医学   122篇
外科学   17646篇
综合类   29530篇
现状与发展   49篇
一般理论   2篇
预防医学   5236篇
眼科学   3901篇
药学   14850篇
  41篇
中国医学   6311篇
肿瘤学   28723篇
  2024年   434篇
  2023年   2780篇
  2022年   4859篇
  2021年   6940篇
  2020年   6187篇
  2019年   5931篇
  2018年   6174篇
  2017年   6560篇
  2016年   6984篇
  2015年   8022篇
  2014年   11852篇
  2013年   13065篇
  2012年   11078篇
  2011年   12498篇
  2010年   10393篇
  2009年   9830篇
  2008年   10188篇
  2007年   10299篇
  2006年   9383篇
  2005年   8542篇
  2004年   7447篇
  2003年   6355篇
  2002年   5178篇
  2001年   4387篇
  2000年   3621篇
  1999年   3231篇
  1998年   3056篇
  1997年   2790篇
  1996年   2484篇
  1995年   2197篇
  1994年   1929篇
  1993年   1619篇
  1992年   1319篇
  1991年   1234篇
  1990年   988篇
  1989年   909篇
  1988年   841篇
  1987年   679篇
  1986年   639篇
  1985年   836篇
  1984年   746篇
  1983年   521篇
  1982年   576篇
  1981年   461篇
  1980年   407篇
  1979年   289篇
  1978年   207篇
  1977年   165篇
  1976年   124篇
  1975年   43篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
61.
Objective: To further explore the mechanism of congenital pyrimidine 5'-nucleotidase I deficiency. Methods; The samples were collected from the family members of a patient with P5'N- I deficiency. The enzyme activities were measured by UMP method and the enzyme proteins were quantified by ELISA while the morphology of peripheral blood cells was observed. Results: The enzyme contents reduced as their enzyme activities decreased in the family especially in four members. There was a significant positive correlation(r =0. 955) between the activity and the content of P 5'N- I . The count of the stippling cell was varied in the family. Conclusion.- One of the reasons for congenital P5' N- I deficiency might be the deficiency in the enzyme content. The morphology of peripheral blood erythrocyte may be an assistant diagnotic index. The P5'N- I activities and contents were measured simultaneously may be a effective method in clinic diagnosis.  相似文献   
62.
Iron deficiency (ID) is one of the most commonly known forms of nutritional deficiencies. Low body iron is thought to induce neurologic defects but may also play a protective role against cancer development by cell growth arrest. Thus, ID may affect cellular pathways controlling cell growth and proliferation, the mechanism of which is still not fully understood. The serine/threonine protein kinase Akt and its downstream target, the mammalian Target of Rapamycin (mTOR), is known to play a crucial role in the regulation of cell growth and survival. Therefore, we hypothesized that Akt/mTOR pathway could be influenced by ID. Three-week-old male Wistar-strain rats were divided into 3 groups and the 2 groups had free access to a control diet (C group) or an iron-deficient diet (D group). The third group (PF group) were pair-fed the control diet to the mean intake of the D group. After 4 weeks, rats were killed and their brains were sampled. In separate experiments, COS-1 cells were cultured with or without the iron chelator deferoxamine. Western blots of brain samples and COS-1 lysates were used to analyze the expression and phosphorylation state of Akt, TSC2, mTOR, and S6 kinase proteins implicated in the Akt/mTOR pathway. Using 2 different ID models, we show for the first time that iron deficiency depresses Akt activity in rats and in COS-1 cells, leading to a decrease in mTOR activity.  相似文献   
63.
64.
We report the case of a 25-year-old male patient who presented with complaints of redness, photophobia, and decreased vision in the right eye of a week's duration. Slit-lamp biomicroscopic examination revealed a cream-colored, irregular elevated inferior iris mass, extending on to the anterior lens surface. Differential diagnoses of a fungal granuloma, a medulloepithelioma, and an amelanotic melanoma were considered. An excisional biopsy of the mass was performed through a superior clear corneal incision. Polymerase chain reaction analysis of the aqueous humor showed a positive pan fungal genome. Histopathology of the biopsied mass showed a giant cell granuloma with surrounding numerous branching, septate hyphae. Culture growth revealed Aspergillus fumigatus We report this case because of the rarity of Aspergillus iris granuloma as a primary presentation of endogenous Aspergillosis and review the relevant literature. Absence of a significant systemic history compounded the diagnostic dilemma in our patient. Definitive differentiation of this rare entity from a foreign body, amelanotic melanoma, and other inflammatory conditions such as sarcoidosis and tuberculosis, may be possible only on microbiological and histo-pathological evaluation.  相似文献   
65.
泰素蒂加顺铂治疗进展期NSCLC的临床研究   总被引:5,自引:0,他引:5  
目的观察泰素蒂加顺铂方案治疗进展期非小细胞肺癌的临床疗效、毒副作用。方法收集可评价疗效的进展期非小细胞肺癌50例,以泰素蒂加顺铂方案进行化疗,泰素蒂75 mg/m2静脉滴注,第1天;顺铂25 mg/m2~30 mg/m2静脉滴注,第2天~第5天,每3周为一个周期,2~3周期后评价疗效和毒副反应并随访。结果50例患者中,总有效率为50.0 %,其中初治病例为53.1 %,复治病例为44.4 %,初复治病例间差异无显著性(P >0.05)。中位缓解期为5个月。中位生存期为9.5个月,1年生存率为61.0 %。毒副反应主要为骨髓抑制,白细胞下降达Ⅲ度、Ⅳ度者52.0 %,血小板下降达Ⅲ度、Ⅳ度者为14.0 %。血红蛋白下降不严重。其他毒副反应还有脱发、过敏反应、水钠潴留、静脉炎、末梢神经炎、口腔炎、腹泻等,但发生率均较低。结论泰素蒂加顺铂方案治疗进展期非小细胞肺癌,特别是复发病例,临床疗效比较满意,毒副反应能够耐受。辅以G蛳CSF可防治重度的骨髓抑制,有较好的临床应用价值。  相似文献   
66.
The role played by dendritic cell (DC) subsets in the immune response to alloantigens is not well defined. In vitro experiments have extensively shown that freshly isolated myeloid (M)DCs induce a strong T lymphocyte proliferation whereas plasmacytoid (P)DCs do not, unless activated by CD40 ligation. The aim of these studies was to explore whether the interplay among PDCs, MDCs and T cells modulates alloresponse. Freshly isolated MDCs and PDCs were merged in different proportions and used as antigen presenting cells (APCs) in mixed lymphocyte cultures (MLC). As described, isolated PDCs only induced a mild alloresponse, while MDCs were potent inducers of alloproliferation. Unexpectedly, when PDCs were merged with even low numbers of MDCs (down to 100 cells) and used as APCs, a potent Th1 cell proliferation was detected. Survival and maturation of PDCs was increased in these MLC conditions, which could partially explain the magnitude of the T-cell response. Interestingly, the proportion of IFNgamma-producing cells generated in such cultures was higher compared to MDC-stimulated cultures. These data suggest that the interaction between both DC subsets is determinant to generate a potent Th1 response, at least in an allogeneic situation, and may be relevant to the outcome of allogeneic stem cell transplantation.  相似文献   
67.
Monoclonal antibodies against human and bovine 2′:3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) were generated by fusing FOX-NY myeloma cells with spleen cells from RBF/Dn mice previously immunized with the purified brain antigens. The enzyme isolated from bovine brain was quite basic, with an isoelectric point of 9.71 and both the bovine and human enzymes consisted of a closely spaced doublet at approximately 44 and 46 kDa on SDS-PAGE. Six monoclonals were identified as strongly recognizing the enzyme on both ELISA plates and on immunoblots of whole brain protein. Four monoclonals very weakly cross-reacted with guinea pig myelin basic protein. In contrast with two previous reports, some of our monoclonal antibodies did immunostain 2 or 3 protein bands in peripheral nerve, two bands closely corresponding to those immunostained in central nervous system (CNS) myelin, the Wolfgram protein fraction and in acetone powders of whole brain. Each of the 6 monoclonals reacting strongly on immunoblots recognized the enzyme in from 2 to 5 of the species examined (human, bovine, rat, mouse and rabbit). In addition, all 6 monoclonals that immunostained the enzyme in whole brain, myelin and Wolfgram protein immunoblots recognized both CNP1 (44 kDa) and CNP2 (46 kDa). The two closely spaced protein bands observed on SDS-PAGE and previously stained on immunoblots of CNS CNPase using polyvalent rabbit anti-bovine CNPase antisera, and now different monoclonal antibodies, appear to be immunologically related and to contain highly conserved sequences.  相似文献   
68.
目的:观察核心结合因子a1(Cbfa1)对兔骨髓间充质干细胞(MSCs)向成骨细胞分化的诱导作用。方法:体外分离培养兔骨髓MSCs,用AdEasy1/Cbfa1。转染MSCs,在转染后3d,1、2、3和4周时,组织化学和免疫组化等方法检测成骨标志碱性磷酸酶和骨钙素的表达。结果:AdEasy1/Cbfa1转染后的兔骨髓MSCs表现出与成骨细胞相似的形态,并且表达碱性磷酸酶和骨钙素。结论:Cbfa1可诱导兔骨髓MSCs向成骨细胞分化。  相似文献   
69.
目的探讨缺氧条件对卵巢癌细胞Caov-3体外黏附和迁移能力的影响。方法在常氧和缺氧条件下培养卵巢癌细胞Caov-3,分别用四甲基偶氮唑蓝(MTT)比色法和细胞迁移试验测定常氧和缺氧条件下培养的Caov-3细胞体外黏附和迁移能力。结果缺氧条件下,Caov-3细胞在Matrigel和纤维连接蛋白Fn基质上黏附数量增加,黏附促进率分别为17.1%和15.2%,与常氧条件下比较有显著性差异(P<0.05)。缺氧条件下,Caov-3细胞在Matrigel基质上迁移距离增大,分别为258.8±19.5μm和331.3±24.4μm,迁移促进率为28.0%,与常氧条件下比较有显著性差异(P<0.05)。结论缺氧环境对卵巢癌细胞Caov-3体外黏附和迁移具有明显的促进作用。  相似文献   
70.
BACKGROUND: To understand the immunopathological features of oral lichen planus (OLP), we analyzed the expression of chemokines in the epithelial cell layers. Methods: Epithelia from OLP or healthy gingiva were collected by laser microdissection. The chemokine and chemokine receptor expressions in the epithelia were analyzed by DNA microarray. RESULTS: High levels of MIP-3alpha/LARC/CCL20 and its receptor CCR6 were expressed in the lesional epithelia. Furthermore, DC-CK1/CCL18, ELC/CCL19, SDF-1/CXCL12 and CXCR4 expressions were also increased. Immunohistologial analysis showed that high numbers of Langerhans cells (LCs) were present in the epithelia of OLP. Lesional epithelia also expressed high levels of the ligands specific for CXCR3 (e.g. MIG/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11) and CCR5 (e.g. RANTES/CCL5). CONCLUSIONS: Infiltration of LCs is orchestrated by CCR6. Further, LCs residing in the lesional epithelia may be a mature phenotype. Moreover, infiltration of T cells in OLP could be mediated by signaling pathways through CXCR3 and CCR5.  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