全文获取类型
收费全文 | 10218篇 |
免费 | 607篇 |
国内免费 | 326篇 |
专业分类
耳鼻咽喉 | 61篇 |
儿科学 | 181篇 |
妇产科学 | 146篇 |
基础医学 | 2105篇 |
口腔科学 | 149篇 |
临床医学 | 1402篇 |
内科学 | 1631篇 |
皮肤病学 | 130篇 |
神经病学 | 321篇 |
特种医学 | 273篇 |
外国民族医学 | 3篇 |
外科学 | 737篇 |
综合类 | 1567篇 |
预防医学 | 394篇 |
眼科学 | 110篇 |
药学 | 662篇 |
中国医学 | 191篇 |
肿瘤学 | 1088篇 |
出版年
2023年 | 68篇 |
2022年 | 104篇 |
2021年 | 214篇 |
2020年 | 179篇 |
2019年 | 175篇 |
2018年 | 194篇 |
2017年 | 227篇 |
2016年 | 242篇 |
2015年 | 263篇 |
2014年 | 419篇 |
2013年 | 581篇 |
2012年 | 474篇 |
2011年 | 597篇 |
2010年 | 449篇 |
2009年 | 470篇 |
2008年 | 495篇 |
2007年 | 564篇 |
2006年 | 510篇 |
2005年 | 538篇 |
2004年 | 451篇 |
2003年 | 477篇 |
2002年 | 413篇 |
2001年 | 369篇 |
2000年 | 335篇 |
1999年 | 301篇 |
1998年 | 245篇 |
1997年 | 241篇 |
1996年 | 253篇 |
1995年 | 240篇 |
1994年 | 205篇 |
1993年 | 138篇 |
1992年 | 120篇 |
1991年 | 99篇 |
1990年 | 84篇 |
1989年 | 75篇 |
1988年 | 38篇 |
1987年 | 40篇 |
1986年 | 31篇 |
1985年 | 52篇 |
1984年 | 23篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 23篇 |
1972年 | 14篇 |
1971年 | 18篇 |
1969年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Belibasakis GN Mattsson A Wang Y Chen C Johansson A 《APMIS : acta pathologica, microbiologica, et immunologica Scandinavica》2004,112(10):674-685
The cytolethal distending toxin (Cdt) is produced by several Gram-negative bacterial species and causes growth arrest and morphological alterations in mammalian cells. Actinobacillus actinomycetemcomitans, which is involved in the pathogenesis of localized aggressive periodontitis, also produces a Cdt that affects periodontal connective tissue cells. The aim of this study was to investigate in which phase of the cell cycle these cells are arrested and enlarged when challenged with A. actinomycetemcomitans, and to evaluate the involvement of its Cdt. Human gingival fibroblasts and periodontal ligament cells were challenged with A. actinomycetemcomitans extract, or with purified Cdt, and cell cycle analysis was performed by propidium iodide staining and flow cytometry. Cells exposed to an A. actinomycetemcomitans wild-type strain, or to purified Cdt, were arrested in both G1 and G2/M phases, and appeared enlarged compared to the corresponding controls. The cellular enlargement occurred in both G1 and G2/M arrested cells. In contrast, cells exposed to an A. actinomycetemcomitans cdt-knockout mutant strain showed cell cycle phase distribution and size similar to the controls. In conclusion, A. actinomycetemcomitans causes a combined G1 and G2/M growth arrest and enlargement in periodontal connective tissue cells, which is attributed to its Cdt. 相似文献
102.
采用流式细胞术对42例正常晚孕妇女及50例妊高征患者产前及产后72小时P-选择素进行对比研究。结果:妊高征患者P-选择素含量明显大于正常晚孕妇女,P-选择素含量在轻、中及重度妊高征患者呈递增趋势,差异均有显著性,产后72小时其P-选择素含量降至正常晚孕妇女水平。提示:P-选择素可作为妊高征早期诊断及监测病情的一个重要指标 相似文献
103.
Yoichiro Kusunoki Yuko Hirai Tomonori Hayashi Seishi Kyoizumi Keiko Takahashi Yukari Morishita Yoshiaki Kodama Mitoshi Akiyama 《European journal of immunology》1993,23(11):2735-2739
We have previously reported 2 cases of healthy men showing in vivo monoclonal expansion of mature CD4? CD8? αβ T cells. In the present study, an additional 3 adults were found to exhibit such an expansion, among a total 464 adult donors studied. These 5 individuals were otherwise physiologically normal, with no history of severe illness and autoimmune disease at the time of examination. To investigate the mechanisms of the clonal expansion, further characterization of the clonal cells was attempted. No apparent preference for usage of the Tcell receptor β chain variable region was observed in the clonal T cells. These clonal T cells showed lectin-dependent or redirected antibody-dependent cell-mediated cytotoxicities, whereas they could not lyse autologous lymphoblastoid cell lines. Failure of Fas antigen expression was not observed for any of these clones. These results suggest that clonal expansion of CD4? CD8? αβ T cells frequently occurs in the periphery without any T cell abnormalities. 相似文献
104.
A system effective in the early diagnosis of Dengue virus infection was developed. The time course kinetics of Dengue virus type 2 (D-2) antigen in vitro were analyzed by Flow Cytometry. Early profiles of D-2 were also studied quantitatively through this method of analysis. The early events of host cell and virus interaction were investigated: attachment, internalization and replication. From these early profiles, the time at which new viral synthesis was detectable differed with each individual trial. These different times were found to be dependent of the phase of the cell cycle. From these results we could detect newly synthesized viral antigen within 10 h after infection. 相似文献
105.
A flow cytometric method for the measurement of phagocytosis by polymorphonuclear leucocytes 总被引:2,自引:0,他引:2
A new method for the measurement of phagocytosis of Candida albicans by human polymorphonuclear leucocytes (PMN) is described using a fluorescence activated cell sorter. We have used acridine orange to discriminate between PMN which have internalised yeast particles and those which have not. This method allows accurate measurement of particle phagocytosis as an event distinct from particle adherence. It also permits detailed examination of the kinetics of phagocytosis, the study of which is likely to be of value in the investigation of diseases where abnormalities of PMN function are suspected. 相似文献
106.
Marius Schwabenland Henrike Salié Jovan Tanevski Saskia Killmer Marilyn Salvat Lago Alexandra Emilia Schlaak Lena Mayer Jakob Matschke Klaus Püschel Antonia Fitzek Benjamin Ondruschka Henrik E. Mei Tobias Boettler Christoph Neumann-Haefelin Maike Hofmann Angele Breithaupt Nafiye Genc Christine Stadelmann Bertram Bengsch 《Immunity》2021,54(7):1594-1610.e11
107.
Alteration in expression of beta 2 integrins on lamina propria lymphocytes in ulcerative colitis and Crohn's disease 总被引:2,自引:0,他引:2
We have previously demonstrated by immunohistochemistry that mucosal expression of beta 2 integrins was enhanced in Crohn's disease and ulcerative colitis as compared to normal controls. We aimed, therefore, to determine whether there was a corresponding alteration in the expression of CD11a/CD18 (LFA-1), the primary lymphocyte beta 2 integrin, among the principal subsets of lamina propria lymphocytes (LPLs). Accordingly, LPLs were extracted from surgical resection specimens derived from patients with Crohn's colitis, ulcerative colitis, and from noninflamed controls. Following immunofluorescent staining, three-color flow-cytometry analysis identified LPLs on the basis of CD45 side scatter gating, which in turn, were further subdivided into CD4(+), CD8(+), and CD19(+) cells to account for the predominant T and B cells in the lamina propria. Expression patterns of CD11a, the alpha-subunit of LFA-1; CD18, the beta-subunit of LFA-1; and alpha d, a novel alpha-subunit of the beta 2 integrin family were assessed for each of these lymphocyte subsets. In Crohn's disease and ulcerative colitis there was an increased mean percentage expression of CD4(+) cells and CD11a(+) cells compared with noninflamed controls. CD11a was more likely to be expressed on CD4(+) cells in both Crohn's disease and ulcerative colitis and compared with controls and less expressed on CD19(+) cells. It is likely that an influx of CD4(+)11a(+) cells into the lamina propria accounted for these changes. These results suggest that although currently there is great interest in harnessing alpha 4 beta 7 in treatment of inflammatory bowel disease, further consideration should be given to the role of CD11a in these disease states. 相似文献
108.
To investigate airway physiology by use of inhaled aerosols, it is frequently necessary to measure the actual amount of material deposited on the airway wall as well as the site of particle deposition. To satisfy these needs, radiolabeled aerosols and gamma camera techniques have been used to measure regional deposition of inhaled particles. To make quantitative measurements of the amount deposited, previous investigators have used a "phantom" technique to indirectly calibrate the gamma camera for the attenuation of gamma rays through the lungs and chest wall. For this calibration, the phantom is a simulated lung containing a known amount of radioactivity. Radioactive counts emitted from the phantom are assumed to be attenuated in the same manner as the intact human lung. The present article describes a technique to determine directly the amount of inhaled aerosol deposited in the lung and simultaneously to calibrate the gamma camera for each individual subject. We used right angle light scattering and a gamma camera to measure individual values of the deposition fraction (DF) of inhaled aerosol deposited in the lung and the coefficient of attenuation (AC) of gamma rays in normal and obstructed lungs of human subjects. Radiolabeled monodisperse aerosols 1 and 2 microns in diameter were used. Knowledge of the activity of the inhaled aerosol (microcurie per liter), the volume inhaled, and the measured DF determined each subject's AC (counts per minute per microcurie). DF varied by an order of magnitude in normal (0.04 to 0.48) and obstructed (0.16 to 0.75) of subjects.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
109.
Gamma delta T cells expressing CD8 or CD4low appear early in murine foetal thymus development. 总被引:2,自引:0,他引:2
Three-colour flow cytometry was used to study the distribution of TCR gamma delta+ cells among CD4+CD8-, CD4-CD8+, CD4+CD8+, and CD4-CD8- cell populations during thymic development. Thymocytes were obtained either directly from embryos at different stages of gestation (ex vivo) or from organ cultures maintained in vitro. In both cases, TCR gamma delta+ cells were found predominantly among the double negative (CD4-CD8-) and CD8 single positive subsets. These cells were actively dividing as demonstrated by 7 amino actinomycin D (7AAD) labelling. A small population of TCR gamma delta+ cells expressing low levels of CD4 was identified early and transiently (days 15-18) during development, but this subset was rare in the adult thymus. In newborn mice, adult mice, and late during organ culture, TCR gamma delta+ cells were found mainly within the CD4-CD8- compartment of thymocytes, although a minor population of CD8+ cells (5-10%) bearing gamma delta receptor was routinely observed. In contrast, few gamma delta cells were contained among the CD4+CD8+ subset at any timepoint studied. These data highlight differences between the ontogeny of alpha beta and gamma delta cells in the thymus, and suggest that a CD4+CD8+ intermediate may not be a requisite for the intrathymic differentiation of murine gamma delta T cells. 相似文献
110.
R P Müller H W Addicks E M Meier 《International journal of radiation oncology, biology, physics》1985,11(9):1613-1619
In order to analyze the possible meaning of cellular DNA content and cell cycle phases for the radiosensitivity and the prognosis of human malignant tumors, flow cytometric measurements have been performed in biopsies of 131 patients with histologically proven squamous cell carcinomas of the maxillo-facial region. In two-thirds of the patients (88/131; 67%), aneuploid tumor cell lines have been found, only 33% (43/131) had a diploid DNA distribution pattern. The average DNA index (DI) of the aneuploid carcinomas was 3.4 +/- 0.6 (normal nonmalignant tissue DI = 2.0). The frequency of S-phase cells, which represents the "proliferative activity", was between 4.8 and 63.2%, regardless of the ploidy stages. The aneuploid carcinomas had about twice as many S-phase cells (mean 23.7 +/- 11.8%) than diploid tumors (mean 12.7 +/- 4.8%). Mean survival for patients with diploid carcinoma and aneuploid carcinoma was 12 and 9.5 months, respectively. Concerning the relationship of S-phase frequency and survival times in our material there was a high negative statistical correlation (Spearman-Rank test) in patients with diploid carcinomas. A high S-phase fraction resulted in short survival times. No correlation was found in the aneuploid carcinomas: patients with tumors in high S-phase values in their biopsies showed no difference in prognosis in comparison to tumors with lower S-phase fractions. 相似文献