全文获取类型
收费全文 | 9945篇 |
免费 | 1253篇 |
国内免费 | 14篇 |
专业分类
耳鼻咽喉 | 122篇 |
儿科学 | 354篇 |
妇产科学 | 335篇 |
基础医学 | 1540篇 |
口腔科学 | 153篇 |
临床医学 | 1355篇 |
内科学 | 1798篇 |
皮肤病学 | 202篇 |
神经病学 | 1181篇 |
特种医学 | 366篇 |
外科学 | 1163篇 |
综合类 | 238篇 |
一般理论 | 10篇 |
预防医学 | 964篇 |
眼科学 | 221篇 |
药学 | 741篇 |
中国医学 | 9篇 |
肿瘤学 | 460篇 |
出版年
2021年 | 121篇 |
2020年 | 100篇 |
2019年 | 153篇 |
2018年 | 171篇 |
2017年 | 148篇 |
2016年 | 123篇 |
2015年 | 143篇 |
2014年 | 223篇 |
2013年 | 311篇 |
2012年 | 431篇 |
2011年 | 421篇 |
2010年 | 260篇 |
2009年 | 214篇 |
2008年 | 375篇 |
2007年 | 434篇 |
2006年 | 423篇 |
2005年 | 432篇 |
2004年 | 404篇 |
2003年 | 377篇 |
2002年 | 333篇 |
2001年 | 357篇 |
2000年 | 363篇 |
1999年 | 301篇 |
1998年 | 128篇 |
1997年 | 134篇 |
1996年 | 108篇 |
1995年 | 116篇 |
1994年 | 97篇 |
1993年 | 86篇 |
1992年 | 211篇 |
1991年 | 211篇 |
1990年 | 219篇 |
1989年 | 230篇 |
1988年 | 236篇 |
1987年 | 216篇 |
1986年 | 219篇 |
1985年 | 185篇 |
1984年 | 138篇 |
1983年 | 139篇 |
1982年 | 107篇 |
1981年 | 90篇 |
1980年 | 89篇 |
1979年 | 144篇 |
1978年 | 122篇 |
1977年 | 87篇 |
1976年 | 98篇 |
1975年 | 102篇 |
1974年 | 118篇 |
1973年 | 101篇 |
1971年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A. C. Webster J. C. Craig J. M. Simpson M. P. Jones J. R. Chapman 《American journal of transplantation》2007,7(9):2140-2151
Transplant recipients have increased cancer risk, but data on risk variation across different patient groups are sparse. Rates and standardized rate ratios (SRR) of cancer (all sites, excluding nonmelanocytic skin and lip cancer) compared to the general population were calculated, using Australia and New Zealand Dialysis and Transplant Registry data. Within the transplant population, risk factors were identified (hazard ratios: HR; 95% CI) and absolute risk estimated for recipient groups. A total of 1642 (10.8%) of 15 183 recipients developed cancer. Risk was inversely related to age (SRR 15-30 children, 2 if >65 years). Females aged 25-29 had rates equivalent to women aged 55-59 from the general population. Age trend for lymphoma, colorectal and breast risk was similar; melanoma showed less variability across ages, prostate showed no risk increase. Within the transplanted population, risk was affected by age differently for each sex (p = 0.007), elevated by prior malignancy (HR 1.40; 1.03-1.89), white race (HR 1.36; 1.12-1.89), but reduced by diabetic end-stage kidney disease (ESKD) (HR 0.67; 0.50-0.89). Cancer rates in kidney recipients are similar to nontransplanted people 20-30 years older, but absolute risk differs across patient groups. Men aged 45-54 surviving 10 years have cancer risks varying from 1 in 13 (non-white, no prior cancer, diabetic ESKD) to 1 in 5 (white, prior cancer, other ESKD). 相似文献
42.
P G Gibson J L Simpson 《The European respiratory journal》2004,23(3):492; author reply 492-492; author reply 493
43.
44.
P K Donnelly A R Simpson A D Milner M L Nicholson T Horsburgh P S Veitch P R Bell 《Nephrology, dialysis, transplantation》1990,5(9):808-811
Whilst HLA matching is routine for renal transplantation, the possible benefits of matching donor and recipient age have not been previously examined. In this study we examined the simultaneous effect of donor to recipient age difference on the graft survival of 141 consecutive first cadaver transplant recipients treated by cyclosporin immunosuppression. Multivariate regression analysis, taking into account other variables of moderately matched recipients (i.e. dialysis time and type, donor/recipient sex, local/imported kidneys, recent sensitivity, total ischaemic time, preoperative transfusions), indicated that age-difference was the single most important variable (P less than 0.05). Individually there was no significant effect of recipient age, whilst older donors (aged greater than 50 years) were associated with significantly worse graft survival than those younger (P less than 0.01). When dealing with donors aged greater than or equal to 50 years the corresponding recipient 1-year graft was improved when the donor was no more than 5 years older than the transplant recipient. Donor age to recipient age difference is a potentially important selection criterion in renal transplantation. 相似文献
45.
Lynn McIntyre Edwin G. Belzer Lise Manchester Wade Blanchard Suzanne Officer A. Catherine Simpson 《The Journal of school health》1996,66(3):132-137
ABSTRACT: The Dartmouth Health Promotion Study was a longitudinal, quasi-experimental field study with a qualitative research arm, designed to learn whether coordinating school health instruction, health services, and a healthful environment enhanced the program's effect on the heart health and mental health of children. The research strategy — the Coordinated Approach — was applied to approximately 300 children in each of two cohorts in grades four to six attending nine trial schools; a further 600 children attended 10 comparison schools in Dartmouth and nine distal comparison schools. Although the qualitative analysis demonstrated that positive feelings were engendered in most areas of the study, when either the classroom or the individual was used as the unit of analysis, the Coordinated Approach did not have a more favorable effect on the heart or mental health of children than did the standard school health program. Thus, the effect of an existing school health program was not directly enhanced through coordinating its components. 相似文献
46.
47.
Postoperative radiation therapy in the management of lung cancer 总被引:1,自引:0,他引:1
Postoperative radiation therapy for lung cancer is still controversial. In a 9-year period, 69 patients with non-oat-cell carcinoma of the lung (16% stage I, 26% stage II, and 58% stage III) received such therapy. The radiation dose was less than 5,000 cGy in 42 patients, 5,000-5,900 cGy in 16, and 6,000 cGy or more in 11; follow-up ranged from 24 to 64 months. Actuarial survival at 2 and 4 years was 50% and 16%, respectively, for squamous cell carcinoma, and 40% and 26% for adenocarcinoma. The 5-year survival for stages I, II, and III cancer was 29%, 17%, and 19%, respectively. Histologic findings and type of surgery did not affect survival, but the radiation dose apparently did. The 3-year survival for patients who received less than 6,000 cGy was 35%, compared with 73% for patients who received higher doses. In eight patients, treatment failed within the irradiated volume: all had received doses of less than 6,000 cGy, and the volume in three was judged to be inadequate. 相似文献
48.
Obstruction of a Bjork-Shiley mitral valve prosthesis occurred in a 41 year old woman due to pannus tissue growing over the valve and impairing disc opening. The unusual intermittent nature of the obstruction was clearly demonstrated by Doppler ultrasound. The pannus was excised and the valve prosthesis replaced successfully with a Carpentier-Edwards xenograft. 相似文献
49.
Evidence consistent with horizontal transfer of the gene (emm12) encoding serotype M12 protein between group A and group G pathogenic streptococci. 下载免费PDF全文
Human isolates of Lancefield group G streptococci harbor sequences homologous with the structural gene (emm) encoding M protein, a major virulence factor in Streptococcus pyogenes (a group A Streptococcus species). We used DNA-DNA hybridization, restriction endonuclease chromosomal profiling, and multilocus enzyme electrophoresis to examine genetic relationships between group A and group G streptococcal strains expressing homologous serologic type 12 M (M12) protein. All M12 group A strains studied had very similar restriction endonuclease genomic profiles and multilocus enzyme genotypes. In contrast, the restriction enzyme genomic profile and multilocus enzyme genotype of the M12 group G strain CS140 were strikingly different from those characterizing the M12 group A organisms. DNA-DNA hybridization studies revealed, on average, 57% genomic similarity between the M12 group A and group G strains. Taken together, our data demonstrate that a gene encoding M12 protein occurs in two highly divergent chromosomal backgrounds, a result suggesting that an episode of horizontal gene transfer and recombination has occurred between two streptococcal lineages. 相似文献
50.
Pregnancy outcome associated with natural family planning (NFP): scientific basis and experimental design for an international cohort study 总被引:1,自引:0,他引:1
J. L. Simpson R. H. Gray J. T. Queenan P. Mena A. Perez R. T. Kambic G. Tagliabue F. Pardo W. S. Stevenson M. Barbato V. H. Jennings M. J. Zinaman J. M. Spieler 《Advances in Contraception》1988,4(4):247-264
Although natural family planning (NFP) is a form of contraception without ostensible maternal risks (other than pregnancy), potential fetal risks could exist if aging gametes are involved in inadvertent fertilization. In the following report, we first review animal studies firmly establishing that aging sperm and aging oocytes (delayed fertilization) cause chromosomal abnormalities in mammals and other species. We next review human studies associating decreased coital frequency with trisomy and studies of NFP populations that generally show no increased frequency of anomalous offspring or spontaneous abortions. Our rationale for initiating an international cohort study is presented, along with the experimental design selected. Preliminary findings indicate that the experimental design chosen will indeed provide information allowing NFP safety to be assessed definitively.
Resumen Aunque la planificación familiar natural (PFN) es una forma de anticoncepción sin riesgos maternos ostensibles, (fuera del embarzo) podrían existir posibles riesgos fetales di gametos que están envejeciendo son inadvertidamente fertilizados. La primera revisión de estudios en animales establece firmemente que espermatozoides y oocytos en envejecimiento (fertilización tardía), causan anormalidades cromosómicas en mamíferos y otras especies. A continuación revisamos estudios en humanos que asocian la disminución de la frecuencia coital con trisomía, y estudios de poblaciones practicando PFN que generalmente no muestran aumento en la frecuencia de descendientes anormales o de abortos espontáneos. Presentamos nuestras razones para iniciar el estudio de una cohorte internactional ademas del diseño experimental elegido proveerá información alegando que la inocuidad de la PFN sea definitivamente valorada.
Resumé Bien que le planning familial naturel (PFN-NFP) soit une forme de contraception ne présentant pas de risques manifestes pour la mère (autres qu'une grossesse), il pourrait y avoir des risques potentiels pour le foetus si des gamètes âgés sont par inadvertance fécondés. Nous passons en revue tout d'abord des études effectuées sur des animaux, établissant fermement que le sperme veillissant et les oocytes vieillissants (fécondation retardée) provoquent des anomalies chromosomales chez les mammifères et d'autres espèces. Nous examinons ensuite des études sur des humains, qui associent diminution coitale et trisomie, et des études de populations pratiquant le PFN, qui ne révèlent généralement pas de fréquence accrue d'enfants anormaux ou d'avortements spontanés. Cette communication expose la raison pour laquelle nous avons entrepris une étude sur une cohorte internationale, ainsi que le concept d'expérimentation que nous avons choisi. Les constatations préliminaires indiquent que ce concept fournira véritablement des informations qui permettront d'évaluer de façon définitive la sécurité du PFN.相似文献