全文获取类型
收费全文 | 2732篇 |
免费 | 192篇 |
国内免费 | 1篇 |
专业分类
耳鼻咽喉 | 12篇 |
儿科学 | 56篇 |
妇产科学 | 79篇 |
基础医学 | 258篇 |
口腔科学 | 16篇 |
临床医学 | 575篇 |
内科学 | 498篇 |
皮肤病学 | 15篇 |
神经病学 | 136篇 |
特种医学 | 283篇 |
外科学 | 258篇 |
综合类 | 94篇 |
一般理论 | 3篇 |
预防医学 | 418篇 |
眼科学 | 29篇 |
药学 | 93篇 |
肿瘤学 | 102篇 |
出版年
2023年 | 14篇 |
2022年 | 10篇 |
2021年 | 37篇 |
2020年 | 26篇 |
2019年 | 29篇 |
2018年 | 55篇 |
2017年 | 34篇 |
2016年 | 43篇 |
2015年 | 41篇 |
2014年 | 58篇 |
2013年 | 127篇 |
2012年 | 169篇 |
2011年 | 188篇 |
2010年 | 90篇 |
2009年 | 108篇 |
2008年 | 159篇 |
2007年 | 172篇 |
2006年 | 191篇 |
2005年 | 202篇 |
2004年 | 184篇 |
2003年 | 153篇 |
2002年 | 177篇 |
2001年 | 38篇 |
2000年 | 41篇 |
1999年 | 46篇 |
1998年 | 28篇 |
1997年 | 23篇 |
1996年 | 19篇 |
1995年 | 23篇 |
1994年 | 11篇 |
1993年 | 12篇 |
1992年 | 29篇 |
1991年 | 29篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1979年 | 10篇 |
1977年 | 10篇 |
1974年 | 12篇 |
1973年 | 13篇 |
1972年 | 12篇 |
1971年 | 13篇 |
1969年 | 8篇 |
1967年 | 9篇 |
排序方式: 共有2925条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
5.
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
6.
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
7.
Pam Almada Karen Carafoli John B Flattery Douglas A French Mary McNamara 《Journal for nurses in staff development》2004,20(6):268-273
Newly graduated nurses often finish orientation and then believe they still need more support and mentoring than is available. Retention rates suffer as they think it must be better elsewhere. This article reports a community hospital's implementation of an education-based preceptor program. A convenience sample of 40 new graduates participated in the study. Qualitative and quantitative findings indicate a high level of satisfaction (mean visual analogue scale score 93.7), 29% increase in retention, and 9.5% decrease in vacancy. 相似文献
8.
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
9.
The physiological regulation of toll-like receptor expression and function in humans 总被引:5,自引:0,他引:5
Graeme I. Lancaster Qamar Khan Pam Drysdale Fiona Wallace Asker E. Jeukendrup Mark T. Drayson Michael Gleeson 《The Journal of physiology》2005,563(3):945-955
Eleven mammalian toll-like receptors (TLRs 1–11) have been identified to date and are known to play a crucial role in the regulation of immune responses; however, the factors that regulate TLR expression and function in vivo are poorly understood. Therefore, in the present study, we investigated the physiological regulation of TLR expression and function in humans. To examine the influence of diurnal rhythmicity on TLR expression and function, peripheral venous blood samples were collected from healthy volunteers ( n = 8) at time points coinciding with the peak and nadir in the endogenous circulating cortisol concentration. While no diurnal rhythmicity in the expression of TLRs 1, 2, 4 or 9 was observed, the upregulation of costimulatory (CD80 and CD86) and antigen-presenting (MHC class II) molecules on CD14+ monocytes following activation with specific TLR ligands was greater ( P < 0.05) in samples obtained in the evening compared with the morning. To examine the influence of physical stress on TLR expression and function, peripheral venous blood samples were collected from healthy volunteers ( n = 11) at rest and following 1.5 h of strenuous exercise in the heat (34°C). Strenuous exercise resulted in a decrease ( P < 0.005) in the expression of TLRs 1, 2 and 4 on CD14+ monocytes. Furthermore, the upregulation of CD80, CD86, MHC class II and interleukin-6 by CD14+ monocytes following activation with specific TLR ligands was decreased ( P < 0.05) in samples obtained following exercise compared with at rest. These results demonstrate that TLR function is subject to modulation under physiological conditions in vivo and provide evidence for the role of immunomodulatory hormones in the regulation of TLR function. 相似文献
10.