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   9047篇
  免费   444篇
  国内免费   85篇
耳鼻咽喉   70篇
儿科学   153篇
妇产科学   99篇
基础医学   1121篇
口腔科学   255篇
临床医学   514篇
内科学   2559篇
皮肤病学   197篇
神经病学   604篇
特种医学   232篇
外科学   1292篇
综合类   59篇
预防医学   304篇
眼科学   248篇
药学   655篇
中国医学   19篇
肿瘤学   1195篇
  2023年   35篇
  2022年   90篇
  2021年   190篇
  2020年   112篇
  2019年   138篇
  2018年   224篇
  2017年   181篇
  2016年   178篇
  2015年   202篇
  2014年   282篇
  2013年   367篇
  2012年   559篇
  2011年   672篇
  2010年   364篇
  2009年   294篇
  2008年   538篇
  2007年   597篇
  2006年   560篇
  2005年   540篇
  2004年   564篇
  2003年   524篇
  2002年   548篇
  2001年   128篇
  2000年   107篇
  1999年   134篇
  1998年   115篇
  1997年   88篇
  1996年   104篇
  1995年   95篇
  1994年   81篇
  1993年   77篇
  1992年   102篇
  1991年   84篇
  1990年   69篇
  1989年   86篇
  1988年   70篇
  1987年   51篇
  1986年   44篇
  1985年   43篇
  1984年   35篇
  1983年   33篇
  1982年   26篇
  1981年   23篇
  1980年   25篇
  1979年   32篇
  1978年   19篇
  1977年   14篇
  1976年   14篇
  1973年   17篇
  1966年   16篇
排序方式: 共有9576条查询结果,搜索用时 218 毫秒
81.
82.
Sleep timing is influenced by the circadian system. Morningness-eveningness (ME) preference in humans is affected by the free-running period, which is determined by circadian clock-relevant genes. In this study, we investigated association between the 3111T/C polymorphism in the 3'-flanking region of hClock (Homo sapiens Clock homolog) and ME preference in 421 Japanese subjects. The Horne-Ostberg ME questionnaire (MEQ) scores showed normal distribution, with mean score of 51.2 +/- 1.4 (range, 25-73), and scores were positively correlated with sleep onset time (r = 0.541, P < 0.001) and wake time (r = 0.513, P < 0.001). MEQ scores were significantly lower in subjects with 3111C/C (n = 12) than in subjects with 3111T/C (n = 106, P < 0.001) or 3111T/T (n = 303, P < 0.001), suggesting a stronger eveningness preference in 3111C/C homozygotes. This group also showed significantly delayed sleep onset (P < 0.001), shorter sleep time (P < 0.001), and greater daytime sleepiness (P < 0.001) in comparison to parameters in the subjects with the 3111T allele. There was no significant difference in any of these parameters between the 3111C/T and 3111T/T genotypes. The influence of the 3111T/C polymorphism on ME preferences in Caucasian populations remains controversial. The present findings in a Japanese population sample, which should have a relatively low risk of population stratification effects, suggest the significance of the association of the 3111C/C allele of hClock with evening preference.  相似文献   
83.
84.
Gefitinib (Iressa, ZD1839), an inhibitor of epidermal growth factor receptor-tyrosine kinase, has shown potent anti-tumor effects and improved symptoms and quality-of-life of a subset of patients with advanced non-small cell lung cancer (NSCLC). However, a large portion of the patients showed no effect to this agent. To establish a method to predict the response of NSCLC patients to gefitinib, we used a genome-wide cDNA microarray to analyze 33 biopsy samples of advanced NSCLC from patients who had been treated with an identical protocol of second to seventh line gefitinib monotherapy. We identified 51 genes whose expression differed significantly between seven responders and 10 non-responders to the drug. We selected the 12 genes that showed the most significant differences to establish a numerical scoring system (GRS, gefitinib response score), for predicting response to gefitinib treatment. The GRS system clearly separated the two groups without any overlap, and accurately predicted responses to the drug in 16 additional NSCLC cases. The system was further validated by the semi-quantitative RT-PCR, immunohistochemistry and ELISA for serological test. Moreover, we proved that the anti-apoptotic activity of amphiregulin, a protein that was significantly over-expressed in non-responders but undetectable in responders, leads to resistance of NSCLC cells to gefitinib in vitro. Our results suggested that sensitivity of a given NSCLC to gefitinib can be predicted according to expression levels of a defined set of genes that may biologically affect drug sensitivity and survival of lung cancer cells. Our scoring system might eventually lead to achievement of personalized therapy for NSCLC patients.  相似文献   
85.
FKHRL1 (FOXO3a), a member of the Forkhead family of genes, has been considered to be involved in the development of breast tumors; however, the in vivo expression and activation status of FKHRL1 in breast tumors still remains unclear. We immunohistochemically demonstrated the expression and intracellular localization of FKHRL1 in human breast tumors by the novel anti-FKHRL1 antibody which is available for formalin-fixed paraffin-embedded specimens. In a total of 51 cases of benign tumors, FKHRL1 was diffusely expressed in all cases, and its intracellular localization was revealed to be cytoplasmic (inactive form) in 94% of cases of intraductal papillomas (16/17) and 91% cases of fibroadenomas (31/34), with a similar pattern to normal glandular epithelium. In invasive ductal carcinomas, 83% of the cases (93/112) diffusely expressed FKHRL1; however, unlike benign tumors, 71% of the cases (66/93) showed the nuclear-targeted, active form of FKHRL1. Moreover, activated FKHRL1 was predominantly observed in scirrhous (29/36, 81% of the cases) and papillotubular (30/38, 79% of the cases) subtypes, compared to the solid-tubular subtype (7/19, 37% of the cases). Furthermore, the cases with nuclear-targeted FKHRL1 showed a tendency to have lymph nodal metastasis with statistical significance (P < 0.0001). Thus, the activation of FKHRL1 seems to be recognized as one of the specific features of invasive ductal carcinoma of the breast.  相似文献   
86.
BACKGROUND: Recent reports have suggested that cryopreservation reduces the immunogenicity of donor tissue. The immunomodulation by cryopreservation might influence on the tissue durability after xenotransplantation. We investigated the in vivo morphologic changes in cryopreserved xenograft (CXG) heart valves. MATERIAL AND METHOD: We transplanted a fresh (fresh xenograft; FXG) and a cryopreserved (CXG) porcine aortic root and a cryopreserved canine (cryopreserved allograft; CAG) aortic root into the abdominal aorta of a dog without any immunosuppressive agents. Explanted grafts on the 21st to 49th days after implantation were analyzed morphologically with light microscopy using some special stains, immunohistochemical analysis, and scanning electron microscopy (SEM). RESULT: Light microscopy showed the absence of smooth muscle cells in the media of the aorta in any group after transplantation. FXG valves did not maintain any cellularity after transplantation. CXG valves contained cellular infiltration in themselves. CAG valves contained numerous fibroblasts, which showed the maintenance of tissue integrity without allowing cellular infiltration. The structure of elastic fibers was well maintained, even in the part of CXG valve with cellular infiltration. Immunohistochemical studies documented the infiltration of T lymphocytes in CXG valves that were labeled by anti-CD3 antibodies. SEM demonstrated that no endothelia were seen on the surface of the valves in any group after transplantation. CONCLUSION: We concluded that the cryopreservation method might provide an immunomodulation of xenogeneic heart valves for transplantation.  相似文献   
87.
Computer imaging analysis was used for quantitative evaluation of the extents, amounts and distributions of glomerular extracellular components, such as the 7S and NC 1 domains of type IV collagen, laminin (LN), fibronectin (FN) and IgA, in glomeruli from patients with IgA nephropathy. Renal biopsy specimens from 13 patients with IgA nephropathy were incubated with mouse monoclonal antibodies against the FN or non collagenous (NC 1) domain of type IV collagen or polyclonal antiserum against the LN or 7S domain of human type IV collagen, and then stained with appropriate dilutions of FITC labeled anti mouse Ig antisera. Marked staining of the 7S or NC 1 domain of type IV collagen, LN or FN was detected in the glomerular capillary walls and/or mesangial areas in patients with IgA nephropathy. In particular, a prominent increase of FN was observed in the subendothelial regions of glomerular capillary walls, i.e. mesangial interposition, in the moderate or advanced stage of IgA nephropathy. Therefore, computer imaging analysis was shown to be useful for the quantitative determination of such components distributed in glomeruli from patients with IgA nephropathy. Acta Pathol Jpn 39: 296 305, 1989.  相似文献   
88.
In contrast to Caucasians, Japanese people have a relatively high incidence of malignant melanoma in the oral cavity and volar-subungual skin. The classification of oral melanoma has not been established. We report 7 new cases of oral melanoma, with a review of 36 cases, published in Japan, between 1970 and 1984. Most of the cases reviewed have radial growth phases, and their gross and microscopic features seem to correspond to those of acral lentiginous melanoma of the skin. However, 1 of our cases and 3 previously reported cases of oral nodular melanoma suggest the presence of melanoma heterogeneity in the oral cavity.  相似文献   
89.
The deposition of immune complexes induces an acute inflammatory response with tissue injury. Immune complex-induced tissue injury is mediated by inflammatory cell infiltration that is highly regulated by multiple chemokines. To assess the role of the chemokine receptors CCR1 and CCR5, and a ligand for these receptors CCL3/macrophage inflammatory protein-1alpha, in this pathogenic process, the reverse passive cutaneous Arthus reaction was induced in mice lacking CCR1, CCR5, or CCL3. Edema was significantly attenuated in CCR1-deficient (CCR1(-/-)) and CCL3(-/-) mice but not CCR5(-/-) mice, compared with wild-type mice. Numbers of infiltrating neutrophils and mast cells were reduced in CCL3(-/-) and CCR1(-/-) mice, respectively, compared with wild-type mice. CCR1 and CCR5 were expressed on neutrophils and mast cells. Remarkably, the intradermal mRNA expression of CCL5/RANTES, another ligand for CCR1 and CCR5, was increased in CCR5(-/-) and CCL3(-/-) mice, compared with wild-type mice, while the cutaneous CCL3 mRNA expression was augmented in CCR1(-/-) and CCR5(-/-) mice. These results indicate that CCR1, CCR5, and CCL3 cooperatively contribute to the cutaneous Arthus reaction, and also suggest that enhanced expression of CCL3 and CCL5 compensates for the loss of CCR1, CCR5, and CCL3 in the reaction.  相似文献   
90.
The marginal zone macrophages of the spleen are implicated in the clearance of polysaccharides, but underlying mechanisms need to be pinpointed. SIGN-R1 is one of five recently identified mouse genes that are homologous to human DC-SIGN and encode a single, external, C-terminal C-type lectin domain. We find that a polyclonal antibody to a specific SIGN-R1 peptide reacts primarily and strongly with a subset of macrophages in the marginal zone of spleen and lymph node medulla. In both sites, SIGN-R1 exists primarily in an aggregated form, resistant to dissociation into monomers upon boiling in SDS under reducing conditions. Upon transfection into three different cell lines, high-mol.-wt forms bearing SIGN-R1 are expressed, as well as reactivity with ER-TR9, a mAb previously described to react selectively with marginal zone macrophages. SIGN-R1-expressing macrophages preferentially sequester dextrans following i.v. injection. Likewise, when phagocytic cells are enriched from spleen and tested in culture, dextran is selectively endocytosed by a subset of very large SIGN-R1(+) cells representing approximately 5% of total released macrophages. Uptake of FITC-dextran by these macrophages in vivo and in vitro is blocked by ER-TR9 and polyclonal anti-SIGN-R1 antibodies. Following transfection with SIGN-R1, cell lines become competent to endocytose dextrans. The dextran localizes primarily to compartments lacking transferrin receptor and the LAMP-1 CD107a panlysosomal antigen. Therefore, SIGN-R1 mediates the uptake of dextran polysaccharides, and it is predominantly expressed in the macrophages of the splenic marginal zone and lymph node medulla.  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