全文获取类型
收费全文 | 4870篇 |
免费 | 221篇 |
国内免费 | 229篇 |
专业分类
耳鼻咽喉 | 24篇 |
儿科学 | 68篇 |
妇产科学 | 76篇 |
基础医学 | 1419篇 |
口腔科学 | 50篇 |
临床医学 | 469篇 |
内科学 | 1071篇 |
皮肤病学 | 108篇 |
神经病学 | 164篇 |
特种医学 | 75篇 |
外国民族医学 | 1篇 |
外科学 | 252篇 |
综合类 | 651篇 |
预防医学 | 185篇 |
眼科学 | 39篇 |
药学 | 198篇 |
中国医学 | 11篇 |
肿瘤学 | 459篇 |
出版年
2023年 | 27篇 |
2022年 | 48篇 |
2021年 | 58篇 |
2020年 | 75篇 |
2019年 | 61篇 |
2018年 | 57篇 |
2017年 | 65篇 |
2016年 | 86篇 |
2015年 | 94篇 |
2014年 | 155篇 |
2013年 | 249篇 |
2012年 | 165篇 |
2011年 | 226篇 |
2010年 | 196篇 |
2009年 | 181篇 |
2008年 | 179篇 |
2007年 | 204篇 |
2006年 | 181篇 |
2005年 | 212篇 |
2004年 | 158篇 |
2003年 | 164篇 |
2002年 | 152篇 |
2001年 | 175篇 |
2000年 | 148篇 |
1999年 | 142篇 |
1998年 | 118篇 |
1997年 | 88篇 |
1996年 | 116篇 |
1995年 | 86篇 |
1994年 | 120篇 |
1993年 | 101篇 |
1992年 | 121篇 |
1991年 | 94篇 |
1990年 | 107篇 |
1989年 | 85篇 |
1988年 | 87篇 |
1987年 | 90篇 |
1986年 | 78篇 |
1985年 | 122篇 |
1984年 | 79篇 |
1983年 | 66篇 |
1982年 | 70篇 |
1981年 | 60篇 |
1980年 | 56篇 |
1979年 | 42篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1975年 | 4篇 |
1971年 | 2篇 |
排序方式: 共有5320条查询结果,搜索用时 15 毫秒
81.
目的 探讨逆转录病毒载体介导的HBsAg抗原的表达及其稳定性。方法 将HBsAg基因插入逆转录病毒载体PLXSN中,构建成重组逆转录病毒载体。用电穿孔法转染PA317细胞,包装成假病毒颗粒,在不同温度下冻存。于不同时间用假病毒颗粒感染HepG2、NIH3T3及293细胞,用RT—PCR及ELISA法检测HBsAg表达;以感染后G418抗性克隆形成数确定假病毒颗粒的活力。结果 在各个时间段HBsAg表达量均差异无显著性。在-20℃冻存时,6个月后克隆数即下降过半,12个月后仅形成少数克隆,24个月后无克隆形成;在-40℃冻存时12个月后HepG2、NIH3T3、293形成的克隆数分别为121、332和89,24个月后分别为42、137和43,与冻存前比较差异有显著性;-70℃冻存时,24个月后克隆数分别为159、463和112,与冻存前比较差异无显著性。结论 HBsAg重组逆转录病毒颗粒在-70℃保存2年后,病毒活力未受明显影响,HBsAg表达量亦无明显改变。 相似文献
82.
Calorini L Mannini A Bianchini F Mugnai G Balzi M Becciolini A Ruggieri S 《Clinical & experimental metastasis》1999,17(10):889-895
A previous study by our laboratory showed that the peritoneal murine Corynebacterium parvum-elicited macrophages released into their growth medium an activity which enhanced the ability of B16-F10 melanoma cells to
form experimental metastases in the lung of syngeneic mice. In the present study, we used a clone of B16-F10 line (F10-M3
cells) to investigate whether the increase in lung-colonizing potential due to the pro-clonogenic activity released by C. parvum-elicited macrophages was associated with biological properties characteristic of a metastatic phenotype. We have found that
the pulmonary retention, growth rate in lung parenchyma, invasiveness through Matrigel, adhesiveness to IL-1-activated endothelium
and MHC class I expression were increased in F10-M3 cells stimulated by the macrophage pro-clonogenic activity. By using an
in vitro experimental protocol, the enhancement of lung-colonizing potential in the stimulated melanoma cells turned out to be a transient
phenomenon as was the increase of invasiveness through Matrigel and the higher expression of MHC class I antigens. In conclusion,
the melanoma cells stimulated by the pro-clonogenic activity released by C. parvum-elicited macrophages showed changes in biological parameters which are relevant to metastatic diffusion. These changes appeared
as a temporary phenomenon which sustains the view that the metastatic phenotype represents a transient biological character
influenced by host factors.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
83.
Masanori Hara Daisuke Mase Susumu Inaba Akira Higuchi Takakuni Tanizawa Noriaki Yamanaka Yuichi Sugisaki Yoshikazu Sado Toshio Okada 《Virchows Archiv : an international journal of pathology》1986,408(4):403-419
Summary The immunofluorescent localization of glomerular basement membrane (GBM) antigens was examined in 52 specimens from normal kidneys and in various renal diseases using antisera to human GBM HGBM), IV type collagen (IV Col) and P3 antigen, a rat nephritogen. Anti-HGBM serum normally stained the GBM and the mesangium in a restrictive pattern, anti-IV Col serum stained the GBM and the mesangium in a wider pattern and anti-P3 serum stained only the GBM. In mesangial proliferative glomerulonephritis, including IgA nephropathy pathy and Henoch-Schönlein nephritis, the widened mesangial areas were stained with anti-HGBM and anti-IV Col sera. In membranous nephropathy, the punched-out lesions of thickened GBM were demonstrated with the three antisera in moderate cases and a double linear distribution with fine granulation with anti-HGBM and anti-IV Col sera were revealed in one severe case. In membranoproliferative glomerulonephritis, the expanded mesangium and thickened capillary walls were stained with anti-HGBM and anti-IV Col sera, while the outer line of glomerular capillary walls was only positive with anti-P3 serum. In crescentic glomerulonephritis, the collapsed glomerular tufts were stained normally with anti-HGBM and anti-P3 sera and weakly with anti-IV Col serum. In diabetic nephropathy, anti-HGBM serum stained the GBM in a double linear distribution without reacting with the expanded mesangium; anti-IV Col serum stained the mesangium and the GBM in a less clear double linear fashion while anti-P3 serum stained the GBM as single line. Thin membrane disease and Alport's syndrome had normal reactivity with all antisera. However, in one case of Alport's syndrome anti-HGBM and anti-P3 sera stained the GBM in a focal and segmental pattern, while normal staining with anti-IV Col serum was found. In lesions with adhesions and crescents the staining was positive for HGBM and IV Col and negative for P3; obsolescent glomeruli were stained with anti-HGBM and anti-P3 sera, and had diminished staining with anti-IV Col serum.The identification of the various structural glomerular antigens is useful in the classification of certain types of glomerular diseases. Further insight into the mechanisms underlying these conditions may be obtained in this way. 相似文献
84.
I. I. Podoplelov G. V. Kryukova A. S. Samoilenko 《Bulletin of experimental biology and medicine》1976,81(5):709-711
The character of interaction between different strains ofEscherichia
coli serotype O26 and cells of continuous cultures of human strains HeLa, Tg-33, and RH was studied in vitro. The phenomenon of cytopathogenic action (CPA) of uropathogenic strains ofE.
coli containing heterogenetic type O(H) and B antigens on human cell strains with the corresponding isoantigens was detected after interaction for 6 h. The number of dead cells in these cultures was 1.5–3 times greater than their number in control cultures to whichE.
coli cells not containing heterogenetic antigens or containing dissimilar heterogenetic antigens of the human AB0 type were added. It is postulated that this phenomenon plays an important role in the development of chronic forms of colibacillary pyelonephritis.Research Laboratory of Experimental Immunobiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Zhukov-Verezhnikov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 5, pp. 568–570, May, 1976. 相似文献
85.
Purification of biologically active rubella virus antigens by immunoaffinity chromatography 总被引:1,自引:0,他引:1
A general procedure for isolating biologically active rubella virus antigens (VPI, Mr = 61,000; VP2, Mr = 45,000; VP3, Mr = 36,000) by monoclonal antibody affinity chromatography is described. Complexes formed between monoclonal antibodies and rubella virus antigens were found to be stable either at low pH or in Tris buffer containing detergent and high salt, but were efficiently dissociated by 5% diethanolamine, pH 11.5, or 50 mM lithium diiodosalicylate buffer, pH 8.0. Chromatographically purified rubella viral antigens retained their antigenicity as determined by enzyme-linked immunosorbent assays. Biological studies showed that rubella structural proteins VP2 and VP3 had no hemagglutinin function while the mixture of VP1 and VP2 and VP3 directly demonstrated hemagglutination activity. These results indicate that VP1 is at least in part responsible for the hemagglutinin function of rubella virus. 相似文献
86.
Preparing monolayers of non-adherent mammalian cells 总被引:5,自引:0,他引:5
A simple method is described for preparing monolayers of non-adherent cells, using concanavalin A to bind the cells to wells of plastic microtest plates. The method was used successfully with all 202 human cell types tested, which included 23 tissue culture lines, 165 fresh specimens of all major histological types of leukemia and lymphoma, 20 fresh myelomas, 2 fresh thymomas, normal spleen and lymph node cells, fractionated T lymphocytes and B lymphocytes from peripheral blood, and cultured fetal amniotic cells. All cell types attached firmly, and were not detached by subsequent vigorous washing. In contrast, attempted attachment of cells in serum free medium, or with poly-L-lysine or glutaraldehyde, was ineffective with many cell types. We used the monolayers as target cells for antibodies to cell surface antigens, utilizing immune rosetting or complement-mediated cytotoxicity. This procedure should simplify most assays involving non-adherent target cells. 相似文献
87.
目的 验证HBeAgTP基因在细胞内的表达及表达蛋白的亚细胞定位。方法 构建HBeAgTP基因的酵母表达诱饵质粒pGBKT7-HBeAgTP及绿色荧光蛋白表达质粒DEGFP-C1-HBeAgTP,pEGFP-C1.HBeAgTP转染HepG2细胞,24h后荧光显微镜下观察蛋白表达的亚细胞定位。pGBKT7-HBeAgTP转化AH109酵母细胞,提取转化了质粒的酵母蛋白质,进行Western免疫印迹分析。结果 成功构建出HBeAgTP基因。HBeAgTP基因的酵母表达诱饵质粒pGBKT7-HBeAgTP及绿色荧光蛋白表达质粒pEGFP-C1.HBeAgTP,Western免疫印迹法印证HBeAgTP可表达蛋白,其表达的蛋白亚细胞定位于细胞质。结论 HBeAgTP基因可表达蛋白,其表达蛋白亚细胞定位于细胞质。 相似文献
88.
HPA polymorphism in sub-Saharan African populations: Beninese, Cameroonians, Congolese, and Pygmies 总被引:2,自引:0,他引:2
Halle L Bigot A Mulen-Imandy G M'Bayo K Jaeger G Anani L Martageix C Bianchi F Julien E Kaplan C 《Tissue antigens》2005,65(3):295-298
The frequency of human platelet antigen-1 (HPA-1) to HPA-11w (excluding HPA-8w) and HPA-15 systems was studied in four sub-Saharan populations: Beninese, Congolese (Democratic Republic of Congo Kinshasa), Cameroonians, and Aka pygmies (Central African Republic). No report of HPA prevalence has previously been published concerning these populations which are characterized by the highest HPA-2b gene frequencies of any reported to date (Aka 0.393, Benin 0.292, Cameroon 0.237, and Congo 0.224) and at lesser degree HPA-5b (Aka 0.405, Congo 0.268, Cameroon 0.254, and Benin 0.182). This study is of great importance (i) particularly in the context of the diversity caused by the population migrations, we may observe today in our hospitals (ii) to confirm that the Pygmy population with distinctive frequencies (absence of the HPA-1b, HPA-2b, and HPA-5b highest frequencies) is an isolated population. 相似文献
89.
The mRNA encoding the variant specific antigen of Trypanosoma brucei has been prepared by immunoprecipitation of polysomes. Polysomes carrying the variant specific antigen account for approx. 3% of the total polysomes. The mRNA thus produced is active in the mRNA dependent rabbit reticulocyte lysate in vitro protein synthesis system and directs the synthesis of a polypeptide of 60 000 daltons which co-migrates both with 125I-labelled purified variant specific antigen and with antigen immunoprecipitated from reticulocyte lysate charged with total polyadenylated mRNA from the same clone. The mRNA is being used both to prepare cDNA clones and to prepare high specific radioactivity cDNA to be used to screen a gene bank for clones containing variant specific antigen coding sequences. 相似文献
90.
J. Lorenz J. Müller-Quernheim C. Castillo-Höfer A. Doboszynska R. Ferlinz 《Journal of molecular medicine (Berlin, Germany)》1990,68(14):728-734
Summary Small cell lung cancer (SCLC) is the most malignant of the pulmonary neoplasms and is associated with a poor local cellular immune response. 16 patients with non small cell lung cancer (NSCLC) and 11 patients with SCLC underwent bronchoalveolar lavage (BAL) in the lung which harbored the tumor in order to investigate the lymphocyte surface antigens utilizing the immunoperoxidase technique. Analysis of blood lymphocytes was performed in parallel. 8 patients with previous sarcoidosis in complete remission who underwent BAL and 10 normal blood donors served as controls.Among blood lymphocytes the CD3+, CD4+ and CD16+ cell populations were elevated significantly and the T4/T8 ratio was elevated in NSCLC patients, but only CD16+ were augmented in SCLC. Cell populations expressing the activation markers transferrin (TF) receptor, interleukin-2 (IL-2) receptor and the very late antigen VAL-1 were also increased in NSCLC, while SCLC was associated with antigen distributions similar to controls. No differences between the cohorts were seen in the expression of human leukocyte antigen (HLA)-DR. In BAL the population of CD3+ and CD4+ cells were reduced in SCLC and the T4/T8 ratio was diminished in contrast to controls and NSCLC patients, whereas these two latter groups did not differ from each other. The distribution pattern of CD16, TF receptor and IL-2 receptor in the study groups resembled that of cells of the blood stream, but CD16+ natural killer cells were additionally down regulated to control values in SCLC. No differences were seen in the distribution of VLA-1. HLA-DR+ cells were clearly elevated in both cancer groups.In general NSCLC was associated with a shift to higher relative numbers of immunocompetent and activated cells. This was most probably attributable to an immune response to neoplastic growth. This shift was largely lacking in SCLC. The analysis of lymphocytes from the periphery of the target organ emerged as a sensitive tool for the study of cellular immunity in lung cancer and showed many similarities to circulating blood cells. However, the analysis of natural killer cells and HLA-DR suggested a dissection of cellular immune response between blood and lung in pulmonary cancer. A depressive interaction between the tumor and the cellular host immune response may contribute to the exceptional malignancy of SCLC.Abbreviations BAL
bronchoalveolar lavage
- HLA-DR
human leukocyte antigen-DR
- IL-2
interleukin-2
- NSCLC
non small cell lung cancer
- SCLC
small cell lung cancer
- TF
transferrin
- VLA-1
very late antigen-1 相似文献