全文获取类型
收费全文 | 2009篇 |
免费 | 150篇 |
国内免费 | 42篇 |
专业分类
儿科学 | 57篇 |
妇产科学 | 3篇 |
基础医学 | 475篇 |
口腔科学 | 8篇 |
临床医学 | 156篇 |
内科学 | 279篇 |
皮肤病学 | 3篇 |
神经病学 | 7篇 |
特种医学 | 20篇 |
外国民族医学 | 1篇 |
外科学 | 42篇 |
综合类 | 248篇 |
预防医学 | 678篇 |
眼科学 | 3篇 |
药学 | 157篇 |
中国医学 | 20篇 |
肿瘤学 | 44篇 |
出版年
2023年 | 9篇 |
2022年 | 30篇 |
2021年 | 68篇 |
2020年 | 60篇 |
2019年 | 37篇 |
2018年 | 47篇 |
2017年 | 58篇 |
2016年 | 72篇 |
2015年 | 65篇 |
2014年 | 92篇 |
2013年 | 149篇 |
2012年 | 117篇 |
2011年 | 127篇 |
2010年 | 109篇 |
2009年 | 90篇 |
2008年 | 112篇 |
2007年 | 92篇 |
2006年 | 85篇 |
2005年 | 100篇 |
2004年 | 71篇 |
2003年 | 64篇 |
2002年 | 42篇 |
2001年 | 49篇 |
2000年 | 45篇 |
1999年 | 26篇 |
1998年 | 37篇 |
1997年 | 37篇 |
1996年 | 33篇 |
1995年 | 31篇 |
1994年 | 28篇 |
1993年 | 25篇 |
1992年 | 27篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有2201条查询结果,搜索用时 31 毫秒
11.
目的 构建甲型副伤寒杆菌(Salmonella paratyphi A)H1a基因原核表达系统,确定表达产物rH1a免疫原性和保护作用,检测甲型副伤寒杆菌临床菌株H1a基因携带和表达情况。方法 采用高保真PCR从甲型副伤寒杆菌临床株JH01中扩增H1a基因,T-A克隆后测序,构建H1a基因原核表达系统pET32a-H1a-E.coli B121DE3。采用SDS-PAGE和BioRad凝胶图象分析系统检查rH1a表达情况,Ni-NTA亲和层析法收集rH1a。采用Western blot鉴定其免疫反应性和免疫原性。建立PCR和ELISA检测98株甲型副伤寒杆菌临床菌株H1a基因携带和表达频率。观察rH1a对甲型副伤寒杆菌50001株感染小鼠的免疫保护作用。结果 与报道的相关序列比较,所克隆的H1a基因核苷酸和氨基酸序列相似性均为99.59%。rH1a表达量为细菌总蛋白的60%左右。甲型副伤寒杆菌全菌抗血清能识别rH1a并与之结合。rH1a免疫家兔可产生抗体。100%(98/98)甲型副伤寒杆菌临床菌株均含有H1a基因并表达H1a。500μg rH1a灌喂或皮下注射免疫小鼠受甲型副伤寒杆菌50001株攻击后的存活率均为50.0%,若加入5μg rLTB,存活率分别上升至75.0%和66.7%。结论 本研究成功地从甲型副伤寒杆菌临床菌株中构建了H1a基因高效原核表达系统。rH1a有良好的免疫原性和一定的免疫保护作用。甲型副伤寒杆菌临床菌株广泛存在H1a基因并高频率表达。 相似文献
12.
Macrophages and dendritic cells (DCs) are antigen-presenting cells (APCs), and the direct involvement of both cell types in the immune response to Salmonella has been identified. In this study we analysed the phenotypic and functional changes that take place in murine macrophages and DCs in response to live and heat-killed Salmonella enterica serovar Typhimurium. Both types of cell secreted proinflammatory cytokines and nitric oxide (NO) in response to live and heat-killed salmonellae. Bacterial stimulation also resulted in up-regulation of costimulatory molecules on macrophages and DCs. The expression of major histocompatibility complex (MHC) class II molecules by macrophages and DCs was differentially regulated by interferon (IFN)-gamma and salmonellae. Live and heat-killed salmonellae as well as lipopolysaccharide (LPS) inhibited the up-regulation of MHC class II expression induced by IFN-gamma on macrophages but not on DCs. Macrophages as well as DCs presented Salmonella-derived antigen to CD4 T cells, although DCs were much more efficient than macrophages at stimulating CD4 T-cell cytokine release. Macrophages are effective in the uptake and killing of bacteria whilst DCs specialize in antigen presentation. This study showed that the viability of salmonellae was not essential for activation of APCs but, unlike live bacteria, prolonged contact with heat-killed bacteria was necessary to obtain maximal expression of the activation markers studied. 相似文献
13.
表达鼠精子Cyritestin蛋白的减毒沙门氏菌疫苗株的构建及其鉴定 总被引:3,自引:0,他引:3
目的 构建表达鼠精子eyritestin蛋白的可口服减毒沙让氏菌活疫苗株。方法 应用质粒TAZ83/13,将之进行双酶切获得含有成熟cyritestin蛋白cDNA序列的酶切片段。将其插入表达载体yA3149中,构建重组质粒pCFL。将该重组质粒转入鼠沙门氏伤寒杆菌疫苗株X4632和X4550中,以获得重组菌株X4632(pCFL)和X4550(pCFL)。结果 该两种无抗药性的重组菌株在体外营养选择压力下,可较稳定地携带重组质粒传代繁殖。X4550(pCFL)在体内可较稳定地害居于Peyer‘s结,肠系膜淋巴结和脾脏;X4632(pCFL)可较稳定地定居于Peyer‘s结。二者均可表达被抗cyritestin单抗(mAb)识别的重组cyritestin蛋白。口服该疫苗菌株无明显的毒性作用。结论 X4632(pCFL),X4550(pCFL)疫苗株的构建,为研究以cyritestin为靶抗原的精子抗原避孕疫苗打下了基础。 相似文献
14.
Zhan Y Brown LE Deliyannis G Seah S Wijburg OL Price J Strugnell RA O'Connell PJ Lew AM 《Immunologic research》2004,30(1):1-14
The most common models of CD4 T-cell deficiency are mice exogenously injected with anti-CD4 antibody (Ab), CD4 knockout (CD4−/−) and major histocompatibility complex (MHC) class II knockout (class II−/−) mice. We recently described the anti-CD4 Ab transgenic mouse (GK) as an improved CD4 cell-deficient model. This review compares
this new GK mouse model with the widely available class II−/− and CD4−/− mice, when exposed to complex antigens (foreign grafts and during bacterial or viral infection). We highlight here the cytometric
and functional differences (including Ab isotype, viral or bacterial clearance, and graft survival) among these CD4 cell-deficient
models. For example, whereas grafts are generally rejected in class II−/− and CD4−/− mice as quickly as in wild-type mice, they survive longer in GK mice. Also, CD4−/− mice produce IgG against both simple model and complex antigens, but class II−/− and GK mice produce small amounts of IgG2a against complex antigens but not simple model antigens. These differences harbinger
the caveats in the use of these various mice. 相似文献
15.
16.
我们已经在减毒鼠伤寒沙门菌SL3261以融合蛋白的形式表达了人工合成的恶性疟原虫杂合113肽基因AB(GZ-AB)。活菌以2×109CFU经口服免疫新西兰家兔,用ELISA测定抗体水平,结果于首次免疫或加强免疫后都可检测到一定水平的特异性抗体。所免疫的家免可以诱发针对恶性疟原虫抗原及GZ-AB的迟发性超敏反应(DTH)。我们的研究表明,含有多个恶性疟原虫抗原表位的人工合成基因可以在减毒鼠伤寒沙门菌中表达,活菌可诱发家兔产生特异的体液免疫及细胞免疫,为恶性疟口服活菌苗的制备打下基础。 相似文献
17.
目的 构建携带鼠疫耶尔森菌F1-V融合基因的重组减毒沙门菌苗,口服免疫Balb/c小鼠检测其免疫原性,为口服鼠疫活载体DNA疫苗研究打下基础.方法 将F1-V融合基因克隆到真核表达载体asd-pVAX1,进一步依次将重组质粒转化减毒沙门菌X3730、X4550得到重组沙门菌X4550(asd-pVAX1/F1-V),提取重组质粒转染COS-7细胞并做免疫组化和Western-blot检测F1-V融合蛋白在细胞中的表达.以1×109CFU/只的剂量3次口服免疫Balb/c小鼠,ELISA方法检测血清中抗体水平.结果 构建的重组减毒沙门菌转染COS-7细胞后,免疫组化和Western-blot试验证明F1-V融合蛋白在细胞中得到了瞬时表达,ELISA检测到免疫小鼠血清有特异性抗体IgG产生.结论 构建的重组沙门菌能运送DNA疫苗到体内并成功释放质粒刺激机体产生特异性免疫应答,为口服鼠疫活载体DNA疫苗的黏膜免疫研究打下了基础. 相似文献
18.
Melo Cavalcante AA Rubensam G Picada JN Gomes da Silva E Fonseca Moreira JC Henriques JA 《Environmental and molecular mutagenesis》2003,41(5):360-369
Fresh and processed cashew (Anacardium occidentale) apple juice (CAJ) are among the most popular drinks in Brazil. Besides their nutritional benefits, these juices have antibacterial and antitumor potential. The chemical constituents of both the fresh juice and the processed juice (cajuina) were analyzed and characterized as complex mixtures containing high concentrations of vitamin C, various carotenoids, phenolic compounds, and metals. In the present study, these beverages exhibited direct and rat liver S9-mediated mutagenicity in the Salmonella/microsome assay with strains TA97a, TA98, and TA100, which detect frameshifts and base pair substitution. No mutagenicity was observed with strain TA102, which detects oxidative and alkylating mutagens and active forms of oxygen. Both CAJ and cajuina showed antioxidant activity as determined by a total radical-trapping potential assay. To test whether this antioxidant potential might result in antimutagenesis, we used a variation of the Salmonella/microsome assay that included pre-, co-, and posttreatment of hydrogen peroxide-exposed Salmonella typhimurium strain TA102 with the juices. CAJ and cajuina protected strain TA102 against mutation by oxidative damage in co- and posttreatments. The antimutagenic effects during cotreatment with hydrogen peroxide may be due to scavenging free radicals and complexing extracellular mutagenic compounds. The protective effects in posttreatment may be due to stimulation of repair and/or reversion of DNA damage. The results indicate that CAJ and cajuina have mutagenic, radical-trapping, antimutagenic, and comutagenic activity and that these properties can be related to the chemical constituents of the juices. 相似文献
19.
The inverse association of salmonellosis in infancy with allergic rhinoconjunctivitis and asthma at school-age: a longitudinal study 总被引:1,自引:0,他引:1
Pelosi U Porcedda G Tiddia F Tripodi S Tozzi AE Panetta V Pintor C Matricardi PM 《Allergy》2005,60(5):626-630
BACKGROUND: Respiratory allergies are inversely related to early acquisition of food-borne and fecal-oral infections, consumption of unpasteurized milk, early exposure to stables and high endotoxin concentrations in a farming environment. We tested therefore if infection by Salmonella in early life can protect from development of respiratory allergies later in life. METHODS: During 2003, we studied two groups of Sardinian children (age 6-18 years) who had been hospitalized before 4 years of age (during 1989-2001) with non-typhoid salmonellosis (n = 148) or acute enteritis of nonbacterial etiology (NB-enteritis) (n = 167). Allergic rhinoconjunctivitis (AR) and asthma were evaluated by telephonic interview with a ISAAC questionnaire; participants reporting AR and/or asthma were further examined through a complete diagnostic work-up to objectively confirm or exclude current disease. Kaplan-Meier curves and Cox proportional hazard models were used to analyze the role of different types of enteritis on the risk of developing allergic rhinoconjunctivitis or asthma over time. RESULTS: Children who had been hospitalized with salmonellosis had a lower prevalence of allergic rhinoconjunctivitis (eight of 148, 5.4%vs 23 of 167, 13.8%; P = 0.019) or asthma (five of 148, 3.4% vs 21 of 167, 12.6%; P = 0.006) than those who had been hospitalized with NB-enteritis. The proportional hazard of salmonellosis for asthma was 0.23 (95% CI: 0.08-0.67; P < 0.01) and for allergic rhinoconjunctivitis was 0.40 (95% CI: 0.17-0.95; P = 0.04), after adjusting for confounders. DISCUSSION: The strength of the observed associations suggests that Salmonella may contribute to shape the natural history of respiratory allergies. However, further studies are needed to test in other settings the association observed in Sardinian children. We speculate that clinical or subclinical infection by Salmonella may contribute to the atopy protective influence of a traditional farming environment or of areas endemic for food-borne and fecal-oral infections. Food hygiene and prevention of salmonellosis must remain however a public health priority. 相似文献
20.
Ross IL Willmore R Heuzenroeder MW 《International journal of medical microbiology : IJMM》2003,293(5):371-375
Fluorescent amplified fragment length polymorphism (FAFLP) analysis was performed on 68 isolates of Salmonella enterica subsp. salamae serovar Sofia (S. Sofia). Fifty eight isolates were obtained over a period of approximately 15 years from a range of human, chicken industry and environmental sources throughout Australia. A further ten isolates were identified from human and poultry sources in Israel from 1972 to 1987. Analysis of FAFLP profiles for fragments between 50 to 500 base pairs in length indicated distinct clusters of isolates. All but seven isolates clustered into four groups of >90% similarity and all isolates displayed at least 70% similarity with each other. No cluster could be attributed to a particular geographical, temporal or source-of-isolation origin. It is concluded that S. Sofia is genetically variable with certain clones persisting over time but no group appears unique to Australia. 相似文献