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   12227篇
  免费   1156篇
  国内免费   702篇
耳鼻咽喉   202篇
儿科学   189篇
妇产科学   165篇
基础医学   1705篇
口腔科学   122篇
临床医学   1559篇
内科学   2050篇
皮肤病学   132篇
神经病学   666篇
特种医学   428篇
外国民族医学   9篇
外科学   1273篇
综合类   1547篇
一般理论   1篇
预防医学   591篇
眼科学   316篇
药学   1202篇
  9篇
中国医学   563篇
肿瘤学   1356篇
  2024年   24篇
  2023年   182篇
  2022年   415篇
  2021年   583篇
  2020年   448篇
  2019年   450篇
  2018年   439篇
  2017年   364篇
  2016年   372篇
  2015年   593篇
  2014年   720篇
  2013年   676篇
  2012年   907篇
  2011年   942篇
  2010年   590篇
  2009年   491篇
  2008年   591篇
  2007年   604篇
  2006年   610篇
  2005年   579篇
  2004年   397篇
  2003年   375篇
  2002年   340篇
  2001年   252篇
  2000年   291篇
  1999年   322篇
  1998年   178篇
  1997年   197篇
  1996年   179篇
  1995年   143篇
  1994年   130篇
  1993年   84篇
  1992年   105篇
  1991年   65篇
  1990年   67篇
  1989年   63篇
  1988年   47篇
  1987年   47篇
  1986年   44篇
  1985年   23篇
  1984年   26篇
  1983年   25篇
  1982年   12篇
  1981年   14篇
  1979年   8篇
  1978年   6篇
  1977年   11篇
  1976年   10篇
  1974年   7篇
  1971年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
We compared the effects of in vivo administration of the anti-T-cell receptor (TCR) alpha beta monoclonal antibody (mAb) (H57-597) to those of the anti-CD3 mAb (145-2C11), with or without anti-NK1.1 mAb (PK136), on xenogeneic skin graft survival in mice. In anti-TCR alpha beta mAb-treated B6 mice, F344 rat skin grafts survived for about 54 days, whereas in anti-CD3 mAb-treated B6 mice with or without anti-NK1.1 mAb treatment grafts survived about 25 days. In anti-TCR alpha beta mAb-treated B6 mice, TCR alpha beta-bearing T-lymphocyte function was completely abrogated, although TCR gamma delta-bearing T-lymphocyte function was still intact on day 9. In the anti-CD3 mAb-treated mice, the functions of both types of T lymphocytes were completely abrogated. On day 32, when most of the skin xenografts had been rejected in the anti-CD3 mAb-treated mice, the functions of both T lymphocytes had recovered considerably, and could actually respond to F344 antigens. In contrast, the function of TCR alpha beta-bearing cells had only partially recovered in the anti-TCR alpha beta mAb-treated mice. Finally, natural killer (NK) activity in the anti-TCR alpha beta mAb-treated mice was intact on day 32, when rat skin grafts still survived. In contrast, NK activity in the anti-CD3 mAb plus anti-NK1.1 mAb-treated mice did not recover on day 32, when skin xenografts had already been rejected. These results suggest that TCR gamma delta-bearing T cells and NK cells by themselves, at least in the absence of TCR alpha beta-bearing T cells, do not mediate xenogeneic skin graft rejection in mouse/rat combinations.  相似文献   
72.
促肝细胞生长素诱导人肝癌细胞(BEL-7402)凋亡   总被引:1,自引:0,他引:1  
本文从细胞学、DNA凝胶电泳、流式细胞术三方面研究促肝细胞生长素(pHGF)在体外对肝癌细胞增殖活性的影响。结果表明:pHGF对肝癌BEL-7402细胞增殖有抑制作用,并存在剂量和时间相关性。其48h的半数抑制浓度(ID50)为0.37mg/ml±0.04mg/ml。而37℃灭活的pHGF对BEL-7402细胞增殖在15h无抑制作用,在24和48h抑制作用很弱(ID50>1.5mg/ml)。DNA凝胶电泳结果表明,pHGF可诱导BEL7402细胞产生细胞凋亡(Apoptosis)。流式细胞术(FCM)结果显示:pHGF抑制BEL-7402细胞增殖过程是先使细胞停留在G0/G1期,继而诱导细胞产生凋亡。后两项结果均显示pHGF对人肝癌细胞凋亡的诱导里时间和剂量相关性。  相似文献   
73.
AIMS: Nodal expression of the carcinoembryonic antigen (CEA), cytokeratin 20 (CK20), and guanylyl cyclase C (GCC) genes was measured in tandem in patients with colorectal cancer (CRC) to assess whether there would be sufficient agreement between these markers in their ability to detect micrometastasis to qualify one of them as a universal marker, and whether frozen and paraffin wax embedded tissues would yield similar results. METHODS: One hundred and seventy five frozen lymph nodes (FT) and 158 formalin fixed, paraffin wax embedded lymph nodes (PET) from 28 CRC cases were analysed using gene specific quantitative real time polymerase chain reaction, carried out on the LightCycler system with SYBR Green chemistry. RESULTS: There was significant disparity in positive detection of the three biomarkers in FT versus PET, with notable agreement achieved only for CEA (66.6%) in FT versus PET in Dukes' B disease, and between CK20 and GCC (44.6%) in FT, also in Dukes' B disease. One patient with full concordance in all three tumour markers with both tissue types suffered a relapse and died within two years of follow up. CONCLUSIONS: There was considerable discordance in the positive detection of the three tumour markers in both tissue types (FT versus PET). This brings into question whether using a single tumour marker to detect micrometastasis in one tissue type (FT or PET) is adequately representative, and challenges the concept of universal markers for molecular CRC metastatic detection. Multiple tumour markers would predict more accurately the metastatic potential of Dukes' B CRCs.  相似文献   
74.
儿童退缩和同伴关系的相关   总被引:6,自引:2,他引:6  
目的:用元分析方法对近20年关于儿童退缩和同伴关系相关的研究结果进行总结。方法:用多水平分析技术对儿童退缩和同伴接受的相关、退缩和同伴拒绝相关的研究结果进行总结分析。结果:儿童退缩和同伴接受之间有显著的负相关关系,退缩和同伴拒绝之间有低度的非负相关关系,各研究结果之间的变异显著。结论:退缩导致儿童不良的同伴关系。  相似文献   
75.
Serotype distribution and antibiotic resistance (AR) among group B streptococci (GBS) affect GBS disease prevention strategies, but vary among patient groups. A multiplex PCR-based reverse line blot (mPCR/RLB) hybridisation assay was used to compare the distributions of GBS serotypes, serotype III subtypes and AR-associated genes among 666 invasive isolates from 663 patients, divided into five age groups: infants, early-onset (EO; 0-6 days) and late-onset (LO; 7-90 days); children (aged 3 months to 14 years); women of childbearing age (WCBA; aged 15-45 years); and other adults (males aged >15 years; females aged >45 years). Serotypes Ia and V and serosubtype III-1 accounted for 60% of infections. Serosubtype III-2, which corresponds to a virulent clone belonging to sequence type (ST)17, was relatively uncommon overall (7%), but was associated strongly with LO infant infections, in which it was significantly more common than in adult infections (25/104 (24%) vs. 9/392 (2%), p <0.0001) or in EO infections (25/104 (24%) vs. 14/155 (9%), p <0.005). Erythromycin resistance genes were found in 8% of all isolates (ermB 3%, ermA 2.5% and mefA/E 2%), in 11-15% of isolates of serotypes II and V and subtype III-1, but in none of the isolates of serosubtype III-2 (III-2, 0/49 vs. all others, 54/618 (9%), p <0.04). In summary, the virulent serosubtype III-2 was associated strongly with LO infant GBS infection, but was less likely than other serotypes or serosubtype III-1 to carry AR genes.  相似文献   
76.
沈燕  仲人前 《现代免疫学》1998,18(4):210-211
本文采用生物素-亲合素-碱性磷酸酶法(ABC-AKP)检测10例正常人血清和7例系统性红斑狼疮(SLE)病人血清中IgG类抗-Sm/抗-U_1RNP抗体对Hep-2细胞的进入作用.结果表明:自身抗体能够进入存活的Hep-2细胞,患者组阳性者4例(57.14%),对照组皆为阴性(P<0.05).讨论了自身抗体进入活的靶细胞在自身免疫性疾病发病中的意义.  相似文献   
77.
目的:为带臂外侧上皮神经及其营养血管筋膜皮瓣提供解剖学基础.方法:32例经灌注红色乳胶的成人上肢标本,对臂外侧上皮神经及其营养血管等进行了较详细的应用解剖学研究.结果:臂外侧上皮神经在均由腑神经发出,起点横径为1.5±0.4mm,在三角肌深方斜向外下3.6±1.1cm从该肌后缘中1/3浅出肌间隔,分为上支和下支,分布于三角肌后部、外侧部和臂外侧上部.该神经的营养血管起源于旋肱后动脉,起点外径为0.9±0.4mm;其行程、分支和分布均同在神经,供血范因为14.8×9.8cm~2,并与周围的皮动脉存在丰富吻合.结论:带臂外侧上皮神经及其营养血管筋膜皮 瓣可视受区需要设计成游离瓣或旋转瓣,用于修复邻近部位、手或颌面部缺损.  相似文献   
78.
The TGF-1(–/–) mouse is a murine model for systemic autoimmune disease. The aim of this study is to elucidate the immunological mechanism that leads to multifocal tissue inflammation and autoantibody production in TGF-1(–/–) mice. Heart, lung, liver, and salivary gland from TGF-1(–/–) were assessed for CD154 expression by RT-PCR and immunohistochemistry. Compared to wild-type littermates, CD154 expression was elevated in all tissues studied. Furthermore, IL-12 mRNA was expressed in the salivary gland and heart of TGF-1(–/–) mice and not in wild-type littermates. This suggests that the CD154 pathway is activated in these tissues. This shows that TGF-1 regulates CD154 expression leading to spontaneous IL-12 production and autoimmunity.  相似文献   
79.
T Maeda  M Eto  Y Nishimura  K Nomoto  Y Y Kong    K Nomoto 《Immunology》1993,78(1):113-121
It has previously been reported that a single i.p. injection of 200 mg/kg cyclophosphamide (CP) 2 days after priming with 10(8) donor spleen cells (SC) leads to donor-specific skin allograft tolerance in H-2 compatible, multiminor antigen incompatible murine strain combinations. It is speculated that the i.v. injection of donor cells may result in synchronized proliferation of donor-reactive host T cells and subsequently administered CP may specifically destroy these proliferating T cells in the periphery. Although this unique action of CP is considered to be a principal mechanism in this method, direct evidence has not yet been obtained. In the present article, this in vivo destructive effect of CP is clearly demonstrated by assessing detailed kinetics of host-derived blastoid T cells and donor (Mls-1a)-reactive V beta 6+ T cells in the model system of C3H mice rendered tolerant to AKR. Frequencies of the blastoid cells and V beta 6+ cells, which increased as a result of AKR priming, decreased rapidly with the administration of CP. C3H mice, which received AKR SC alone, also exhibited partial deletion of V beta 6+ T cells, but both tempo and magnitude of decrease in the frequency of V beta 6+ cells were quite different from those of the C3H mice given AKR SC and CP, which showed more rapid and profound elimination of V beta 6+ T cells. In accordance with these kinetic studies, in vitro proliferative response to Mls-1a antigens was greatly impaired in mice treated with SC and CP, whereas a low but appreciable response was detected in mice given SC alone.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
80.
针刺大鼠“人中”、“四白”穴使之产生明显镇痛效果后,再将针刺时间分别延长至1、2、4、6、8、10、12h,到预定时间立即将动物灌流杀死取材,采用定量电镜方法观察计数了三叉神经尾侧脊束核胶状质亚核内各种有衣小泡的数量、形态以及在不同针刺时间内数量的变化。结果发现:大单壁有衣小泡的形成与针刺时间无明显正比例关系;而双壁有衣小泡则显然与之不同,它不仅形态多样,数目也随针刺时间而改变。本文将观察到的双壁有衣小泡归纳为以下五种类型:1、尚未与相邻两终末质膜脱离的孤立存在者。2、游离于终末内孤立存在者。3、与终末质膜相连且融合而成簇存在者;4、游离于终末内融合成簇者;5、树突棘凸入另一轴突或树突内并与之共同形成的不典型的双壁有衣小泡簇。本研究还发现,在针刺过程中双壁有衣小泡在1~8h内的形成与时间成正比,即1h时开始增多,4h显著增多,8h达高峰;以后开始下降,10h已恢复到4h的水平,到12h恢复到针刺前的状态。对照组仅见少数孤立的双壁有衣小泡,其形成基本上不随时间而变化。本文认为双壁有衣小泡的形成,是较大单壁有衣小泡的形成更为有效地继大致密核心小泡非突触部位胞吐之后膜再循环的一条新途径。  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