全文获取类型
收费全文 | 1203篇 |
免费 | 104篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 10篇 |
妇产科学 | 41篇 |
基础医学 | 144篇 |
口腔科学 | 7篇 |
临床医学 | 176篇 |
内科学 | 236篇 |
皮肤病学 | 4篇 |
神经病学 | 27篇 |
特种医学 | 267篇 |
外科学 | 141篇 |
综合类 | 42篇 |
一般理论 | 2篇 |
预防医学 | 127篇 |
眼科学 | 12篇 |
药学 | 38篇 |
肿瘤学 | 31篇 |
出版年
2021年 | 17篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 15篇 |
2014年 | 23篇 |
2013年 | 54篇 |
2012年 | 73篇 |
2011年 | 72篇 |
2010年 | 41篇 |
2009年 | 59篇 |
2008年 | 54篇 |
2007年 | 70篇 |
2006年 | 57篇 |
2005年 | 55篇 |
2004年 | 52篇 |
2003年 | 39篇 |
2002年 | 46篇 |
2001年 | 28篇 |
2000年 | 33篇 |
1999年 | 26篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1992年 | 22篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1979年 | 9篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1974年 | 11篇 |
1973年 | 12篇 |
1972年 | 12篇 |
1971年 | 13篇 |
1970年 | 7篇 |
1969年 | 8篇 |
1967年 | 9篇 |
1966年 | 7篇 |
排序方式: 共有1307条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Abstract: Background : In response to rising cesarean rates, it is reasonable for health care organizations to look to a managed care model as a means of controlling further rate increases. However, little conclusive evidence exists to support this solution. We undertook a study of the Department of Defense health care beneficiary population to assess the impact of enrollment in TRICARE Prime, the Department's managed care health plan, on cesarean delivery rates. Methods : Pooled hospital discharge records from 1999–2002 for live, singleton births were analyzed to calculate primary and repeat cesarean rates for TRICARE Prime and non‐Prime beneficiaries in the military and civilian hospitals that comprise the Department of Defense health care network. Stepwise logistic regression was used to calculate adjusted odds ratios for clinical indicators for each combination of health plan and hospital setting using theχ2difference(p < 0.05)to eliminate nonsignificant variables from the model. Total primary and repeat cesarean rates were compared with primary and repeat cesarean rates for women with no reported clinical complications to account for differences in case mix across subgroups. Statistical significance of the differences calculated for subgroups was assessed usingχ2. Results : Primary cesarean rates were significantly lower for TRICARE Prime enrollees relative to non‐Prime beneficiaries for all race subgroups and three of five age subgroups in military hospitals and four of five age subgroups in civilian hospitals. No significant differences in repeat cesarean rates were observed between Prime and non‐Prime beneficiaries within any race or age subgroup. Breech presentation followed by dystocia, fetal distress, and other complications were significant predictors for primary cesarean. Previous cesarean delivery was the leading predictor for repeat cesarean delivery. Primary and repeat cesarean rates observed for military hospitals were consistently lower than rates observed for civilian hospitals within each health plan type and age group. Conclusions : Enrollment in the managed care health plan was significantly associated with lower risk of primary cesarean delivery relative to membership in other health plans offered to Department of Defense health care beneficiaries. Repeat cesarean rates in this population varied independently of health plan type. Primary cesarean delivery was generally associated with clinical complications, whereas previous cesarean delivery was the strongest indictor for a repeat cesarean delivery. A clear explanation of reduced cesarean rates for Prime enrollees remains elusive, but it is likely that factors beyond individual practitioner decision‐making were at work. 相似文献
5.
Andr Mas Hassan Jaaba Franois Schu Anna M. Belu Camille M. Kassis Richard W. Linton Joseph M. Desimone 《Macromolecular chemistry and physics.》1997,198(11):3737-3752
Homogeneous and stable layers were deposited through allylamine plasma polymerization (75 W, 100 Pa, 15 min) onto poly[(3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)] (91 : 9 wt.-%) (P(HB-co-9%HV)) film surfaces, XPS analysis using take-off angles of 20° and 70° and performed 10 days and 20 days after plasma treatment gives information on the composition (in atom%) of the modified surface: C, 62.74; N, 19.60; O, 17.65. The unexpected oxygen percentage is weaker if argon plasma pretreatment (25 W, 40 Pa, 5 min) is applied. Then, a succinct mechanism is proposed. The study of changes in element ratios and binding energy values shows that the majority of incorporated functional groups seem to be amide and imine groups. 相似文献
6.
Genetic diversity and molecular identification of mosquito species in the Anopheles maculatus group using the ITS2 region of rDNA. 总被引:2,自引:0,他引:2
C Walton P Somboon S M O'Loughlin S Zhang R E Harbach Y-M Linton B Chen K Nolan S Duong M-Y Fong I Vythilingum Z D Mohammed Ho Dinh Trung R K Butlin 《Infection, genetics and evolution》2007,7(1):93-102
The species diversity and genetic structure of mosquitoes belonging to the Anopheles maculatus group in Southeast Asia were investigated using the internal transcribed spacer 2 (ITS2) of ribosomal DNA (rDNA). A molecular phylogeny indicates the presence of at least one hitherto unrecognised species. Mosquitoes of chromosomal form K from eastern Thailand have a unique ITS2 sequence that is 3.7% divergent from the next most closely related taxon (An. sawadwongporni) in the group. In the context of negligible intraspecific variation at ITS2, this suggests that chromosomal form K is most probably a distinct species. Although An. maculatus sensu stricto from northern Thailand and southern Thailand/peninsular Malaysia differ from each other in chromosomal banding pattern and vectorial capacity, no intraspecific variation was observed in the ITS2 sequences of this species over this entire geographic area despite an extensive survey. A PCR-based identification method was developed to distinguish five species of the group (An. maculatus, An. dravidicus, An. pseudowillmori, An. sawadwongporni and chromosomal form K) to assist field-based studies in northwestern Thailand. Sequences from 187 mosquitoes (mostly An. maculatus and An. sawadwongporni) revealed no intraspecific variation in specimens from Thailand, Cambodia, mainland China, Malaysia, Taiwan and Vietnam, suggesting that this identification method will be widely applicable in Southeast Asia. The lack of detectable genetic structure also suggests that populations of these species are either connected by gene flow and/or share a recent common history. 相似文献
7.
8.
9.
PCR detection, identification to species level, and fingerprinting of Campylobacter jejuni and Campylobacter coli direct from diarrheic samples. 总被引:7,自引:0,他引:7
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Three sets of primers were designed for PCR detection and differentiation of Campylobacter jejuni and Campylobacter coli. The first PCR assay was designed to coidentify C. jejuni and C. coli based on their 16S rRNA gene sequences. The second PCR assay, based on the hippuricase gene sequence, identified all tested reference strains of C. jejuni and also strains of that species which lack detectable hippuricase activity. The third PCR assay, based on the sequence of a cloned (putative) aspartokinase gene and the downstream open reading frame, identified all tested reference strains of C. coli. The assays will find immediate application in the rapid identification to species level of isolates. The assays combine with a protocol for purification of total DNA from fecal samples to allow reproducible PCR identification of campylobacters directly from stools. Of 20 clinical samples from which campylobacters had been cultured, we detected C. jejuni in 17, C. coli in 2, and coinfection of C. jejuni and Campylobacter hyointestinalis in 1. These results were concordant with culture and phenotypic identification to species level. Strain typing by PCR-restriction fragment length polymorphism of the flagellin (flaA) gene detected identical flaA types in fecal DNA and the corresponding campylobacter isolate. Twenty-five Campylobacter-negative stool samples gave no reaction with the PCR assays. These PCR assays can rapidly define the occurrence, species incidence, and flaA genotypes of enteropathogenic campylobacters. 相似文献
10.