全文获取类型
收费全文 | 7519篇 |
免费 | 748篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 131篇 |
儿科学 | 225篇 |
妇产科学 | 229篇 |
基础医学 | 1002篇 |
口腔科学 | 212篇 |
临床医学 | 1002篇 |
内科学 | 1144篇 |
皮肤病学 | 144篇 |
神经病学 | 645篇 |
特种医学 | 263篇 |
外科学 | 944篇 |
综合类 | 233篇 |
一般理论 | 4篇 |
预防医学 | 830篇 |
眼科学 | 71篇 |
药学 | 614篇 |
中国医学 | 33篇 |
肿瘤学 | 550篇 |
出版年
2021年 | 113篇 |
2020年 | 75篇 |
2019年 | 149篇 |
2018年 | 162篇 |
2017年 | 123篇 |
2016年 | 137篇 |
2015年 | 146篇 |
2014年 | 192篇 |
2013年 | 303篇 |
2012年 | 411篇 |
2011年 | 476篇 |
2010年 | 255篇 |
2009年 | 192篇 |
2008年 | 359篇 |
2007年 | 370篇 |
2006年 | 352篇 |
2005年 | 333篇 |
2004年 | 318篇 |
2003年 | 292篇 |
2002年 | 271篇 |
2001年 | 196篇 |
2000年 | 187篇 |
1999年 | 160篇 |
1998年 | 76篇 |
1997年 | 49篇 |
1996年 | 66篇 |
1995年 | 70篇 |
1994年 | 56篇 |
1993年 | 58篇 |
1992年 | 122篇 |
1991年 | 126篇 |
1990年 | 138篇 |
1989年 | 132篇 |
1988年 | 136篇 |
1987年 | 136篇 |
1986年 | 130篇 |
1985年 | 119篇 |
1984年 | 99篇 |
1983年 | 86篇 |
1982年 | 68篇 |
1980年 | 42篇 |
1979年 | 74篇 |
1978年 | 57篇 |
1975年 | 46篇 |
1974年 | 67篇 |
1973年 | 70篇 |
1972年 | 52篇 |
1971年 | 52篇 |
1970年 | 43篇 |
1969年 | 52篇 |
排序方式: 共有8276条查询结果,搜索用时 203 毫秒
61.
Diabetes and Deficits in Cortical Bone Density,Microarchitecture, and Bone Size: Framingham HR‐pQCT Study 下载免费PDF全文
Elizabeth J Samelson Serkalem Demissie L Adrienne Cupples Xiaochun Zhang Hanfei Xu Ching‐Ti Liu Steven K Boyd Robert R McLean Kerry E Broe Douglas P Kiel Mary L Bouxsein 《Journal of bone and mineral research》2018,33(1):54-62
Older adults with type 2 diabetes (T2D) tend to have normal or greater areal bone mineral density (aBMD), as measured by DXA, than those who do not have diabetes (non‐T2D). Yet risk of fracture is higher in T2D, including 40% to 50% increased hip fracture risk. We used HR‐pQCT to investigate structural mechanisms underlying skeletal fragility in T2D. We compared cortical and trabecular bone microarchitecture, density, bone area, and strength in T2D and non‐T2D. In secondary analyses we evaluated whether associations between T2D and bone measures differed according to prior fracture, sex, and obesity. Participants included 1069 members of the Framingham Study, who attended examinations in 2005 to 2008 and underwent HR‐pQCT scanning in 2012 to 2015. Mean age was 64 ± 8 years (range, 40 to 87 years), and 12% (n = 129) had T2D. After adjustment for age, sex, weight, and height, T2D had lower cortical volumetric BMD (vBMD) (p < 0.01), higher cortical porosity (p = 0.02), and smaller cross‐sectional area (p = 0.04) at the tibia, but not radius. Trabecular indices were similar or more favorable in T2D than non‐T2D. Associations between T2D and bone measures did not differ according to sex or obesity status (all interaction p > 0.05); however, associations did differ in those with a prior fracture and those with no history of fracture. Specifically, cortical vBMD at the tibia and cortical thickness at the radius were lower in T2D than non‐T2D, but only among those individuals with a prior fracture. Cortical porosity at the radius was higher in T2D than non‐T2D, but only among those who did not have a prior fracture. Findings from this large, community‐based study of older adults suggest that modest deterioration in cortical bone and reductions in bone area may characterize diabetic bone disease in older adults. Evaluation of these deficits as predictors of fracture in T2D is needed to develop prevention strategies in this rapidly increasing population of older adults. © 2017 American Society for Bone and Mineral Research. 相似文献
62.
Hill Daniel Boyd Andrew Board Tim 《European journal of orthopaedic surgery & traumatology : orthopedie traumatologie》2018,28(6):1183-1189
European Journal of Orthopaedic Surgery & Traumatology - The aim of this survey was to explore general practitioners’ opinions and practices regarding the management of symptomatic knee... 相似文献
63.
64.
Innate and adaptive lymphocytes employ diverse effector programs that provide optimal immunity to pathogens and orchestrate tissue homeostasis, or conversely can become dysregulated to drive progression of chronic inflammatory diseases. Emerging evidence suggests that CD4+ T helper cell subsets and their innate counterparts, the innate lymphoid cell family, accomplish these complex biological roles by selectively programming their cellular metabolism in order to instruct distinct modules of lymphocyte differentiation, proliferation, and cytokine production. Further, these metabolic pathways are significantly influenced by tissue microenvironments and disease states. Here, we summarize our current knowledge on how cell-intrinsic metabolic factors modulate the context-dependent bioenergetic pathways that govern innate and adaptive lymphocytes. Further, we propose that a greater understanding of these pathways may lead to the identification of unique features in each population and provoke the development of novel therapeutic strategies to modulate lymphocytes in health and disease. 相似文献
65.
66.
Interferon–inducible T Cell Alpha Chemoattractant (I-TAC): A Novel Non-ELR CXC Chemokine with Potent Activity on Activated T Cells through Selective High Affinity Binding to CXCR3 下载免费PDF全文
67.
Discovery of cyanovirin-N, a novel human immunodeficiency virus-inactivating protein that binds viral surface envelope glycoprotein gp120: potential applications to microbicide development. 总被引:22,自引:3,他引:22 下载免费PDF全文
M R Boyd K R Gustafson J B McMahon R H Shoemaker B R O'Keefe T Mori R J Gulakowski L Wu M I Rivera C M Laurencot M J Currens J H Cardellina nd R W Buckheit Jr P L Nara L K Pannell R C Sowder nd L E Henderson 《Antimicrobial agents and chemotherapy》1997,41(7):1521-1530
We have isolated and sequenced a novel 11-kDa virucidal protein, named cyanovirin-N (CV-N), from cultures of the cyanobacterium (blue-green alga) Nostoc ellipsosporum. We also have produced CV-N recombinantly by expression of a corresponding DNA sequence in Escherichia coli. Low nanomolar concentrations of either natural or recombinant CV-N irreversibly inactivate diverse laboratory strains and primary isolates of human immunodeficiency virus (HIV) type 1 as well as strains of HIV type 2 and simian immunodeficiency virus. In addition, CV-N aborts cell-to-cell fusion and transmission of HIV-1 infection. Continuous, 2-day exposures of uninfected CEM-SS cells or peripheral blood lymphocytes to high concentrations (e.g., 9,000 nM) of CV-N were not lethal to these representative host cell types. The antiviral activity of CV-N is due, at least in part, to unique, high-affinity interactions of CV-N with the viral surface envelope glycoprotein gp120. The biological activity of CV-N is highly resistant to physicochemical denaturation, further enhancing its potential as an anti-HIV microbicide. 相似文献
68.
Satellite and Mobile Wireless Transmission of Focused Assessment with Sonography in Trauma 总被引:1,自引:0,他引:1
Christofer A. Strode MD Bernard J. Rubal PhD Robert T. Gerhardt MD MPH Frank L. Christopher MD James R. Bulgrin BS-EE E. Sterling Kinkler Jr. PE MS Terry D. Bauch MD Sheri Y. N. Boyd MD 《Academic emergency medicine》2003,10(12):1411-1414
Objectives: Focused assessment with sonography in trauma (FAST) can define life‐threatening injuries in austere settings with remote real‐time review by experienced physicians. This study evaluates vest‐mounted microwave, satellite, and LifeLink communications technology for image clarity and diagnostic accuracy during remote transmission of FAST examinations. Methods: Using a SonoSite, FAST was obtained on three patients with pericardial and intraperitoneal effusions and two control subjects in a remotely located U.S. Army Combat Support Hospital. A miniature vest‐mounted video transmitter attached to the SonoSite sent wireless ultrasound video 20 m to a receiving antenna. The signal was then transferred over VSAT satellite systems at 512 kilobaud per second (kbps), INMARSAT satellite systems at 64 kbps, and over LifeLink on a moving ambulance through a metropolitan wireless traffic–management network. Clarity and absence or presence of effusions were recorded by 15 staff emergency physicians. Results: Average sensitivity, specificity, and accuracy were 87% (95% confidence interval [CI] = 79% to 95%), 85% (95% CI = 81% to 89%), and 86% (95% CI = 82% to 90%) for the Premier Wireless Vest; 98% (95% CI = 97% to 99%), 83% (95% CI = 75% to 91%), and 86% (95% CI = 82% to 90%) for VSAT; 95% (95% CI = 94% to 96%), 70% (95% CI = 58% to 82%), and 75% (95% CI = 70% to 80%) for INMARSAT; and 82% (95% CI = 73% to 91%), 83% (95% CI = 74% to 92%), and 82% (95% CI = 78% to 86%) for LifeLink with clarity of 3.0 (95% CI = 2.7 to 3.3), 2.9 (95% CI = 2.6 to 3.2), 1.3 (95% CI = 1.2 to 1.4), and 2.1 (95% CI = 1.8 to 2.4), respectively. Conclusions: Accuracy correlated with clarity. Roaming vest transmission of FAST provides interpretable, diagnostic imagery at the distances used in this study. VSAT provided the best clarity and diagnostic value with the lighter, more portable INMARSAT serving a lesser role for remote clinical interpretation. LifeLink performed well, and further infrastructure improvements may increase clarity and accuracy. 相似文献
69.
B cell origin of non-T cell acute lymphoblastic leukemia. A model for discrete stages of neoplastic and normal pre-B cell differentiation. 总被引:23,自引:7,他引:23 下载免费PDF全文
L M Nadler S J Korsmeyer K C Anderson A W Boyd B Slaughenhoupt E Park J Jensen F Coral R J Mayer S E Sallan et al. 《The Journal of clinical investigation》1984,74(2):332-340
The expression of B cell associated and restricted antigens on tumor cells isolated from 138 patients with non-T cell acute lymphoblastic leukemia (non-T cell ALL) was investigated by flow cytometric analysis by means of a panel of monoclonal antibodies. Tumor cells from these patients could be assigned to one of four subgroups: human leukocyte antigen-DR-related Ia-like antigens (Ia) alone (4%, stage I); IaB4 (14%, stage II); IaB4CALLA (33%, stage III); and IaB4CALLAB1 (49%, stage IV). The expression of B cell-restricted antigens (B4 and B1) and rearrangements of Ig heavy chain genes provided strong evidence for the B cell lineage of stages II, III, and IV tumors. The lineage of the Ia alone group is still unknown. The B4 antigen was expressed on approximately 95% of all non-T cell ALLs tested, and given its absence on T cell and myeloid tumors, it appears to be an exceptional marker to define cells of B lineage. The demonstration that Ia alone, IaB4, IaB4CALLA, and IaB4CALLAB1 positive cells can be readily identified by dual fluorescence analysis in normal fetal and adult bone marrow provided critical support for the view that these leukemic pre-B cell phenotypes were representative of the stages of normal pre-B cell differentiation. It was interesting that the IaB4+ cell was more frequently identified in fetal bone marrow than in adult marrow, whereas the predominant cell found in adult marrow expressed the IaB4CALLAB1 phenotype. These data suggest that the leukemogenic event may be random, since the predominant pre-B cell leukemic phenotype appears to correspond to the normal pre-B cell phenotype present in these hematopoietic organs. Our observations provide an additional distinction between adult and childhood ALL, since these studies show that most non-T cell ALLs seen in children less than 2 yr old are of stage II phenotype, whereas the majority of non-T ALLs in adults are of stage IV phenotype. Finally, it should be noted that the present study suggests that the analysis of leukemic B cell phenotypes and their normal counterparts can provide a mechanism for the investigation and orderly definition of stages of pre-B cell differentiation in man. 相似文献
70.