全文获取类型
收费全文 | 1640篇 |
免费 | 248篇 |
国内免费 | 21篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 58篇 |
妇产科学 | 26篇 |
基础医学 | 85篇 |
口腔科学 | 73篇 |
临床医学 | 271篇 |
内科学 | 427篇 |
皮肤病学 | 38篇 |
神经病学 | 60篇 |
特种医学 | 295篇 |
外科学 | 131篇 |
综合类 | 19篇 |
预防医学 | 285篇 |
眼科学 | 11篇 |
药学 | 36篇 |
肿瘤学 | 85篇 |
出版年
2023年 | 48篇 |
2022年 | 13篇 |
2021年 | 11篇 |
2020年 | 41篇 |
2019年 | 18篇 |
2018年 | 52篇 |
2017年 | 33篇 |
2016年 | 45篇 |
2015年 | 55篇 |
2014年 | 96篇 |
2013年 | 119篇 |
2012年 | 34篇 |
2011年 | 53篇 |
2010年 | 63篇 |
2009年 | 82篇 |
2008年 | 48篇 |
2007年 | 74篇 |
2006年 | 50篇 |
2005年 | 36篇 |
2004年 | 40篇 |
2003年 | 16篇 |
2002年 | 15篇 |
2001年 | 25篇 |
2000年 | 22篇 |
1999年 | 29篇 |
1998年 | 65篇 |
1997年 | 89篇 |
1996年 | 79篇 |
1995年 | 57篇 |
1994年 | 62篇 |
1993年 | 52篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 31篇 |
1989年 | 42篇 |
1988年 | 32篇 |
1987年 | 34篇 |
1986年 | 34篇 |
1985年 | 33篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 25篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 10篇 |
1969年 | 2篇 |
排序方式: 共有1909条查询结果,搜索用时 15 毫秒
71.
A diaper bank and home visiting partnership: Initial exploration of research and policy questions 下载免费PDF全文
72.
73.
Cytokine production by primary bone marrow megakaryocytes 总被引:4,自引:2,他引:4
Primary human bone marrow megakaryocytes were studied for their ability to express and release cytokines potentially relevant to their proliferation and/or differentiation. The purity of the bone marrow megakaryocytes was assessed by morphologic and immunocytochemical criteria. Unstimulated marrow megakaryocytes constitutively expressed genes for interleukin-1 beta (IL-1 beta), IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor-alpha (TNF-alpha), by the polymerase chain reaction (PCR) and Northern blot analysis. At the protein level, megakaryocytes secreted significant amounts of IL-1 beta (53.6 +/- 3.6 pg/mL), IL-6 (57.6 +/- 15.6 pg/mL), and GM-CSF (24 +/- 4 pg/mL) but not TNF-alpha. Exposure of human marrow megakaryocytes to IL-1 beta increased the levels of IL-6 (87.3 +/- 2.3 pg/mL) detected in the culture supernatants. Transforming growth factor- beta was also able to stimulate IL-6, IL-1 beta, and GM-CSF secretion, but was less potent than stimulation with phorbol-12-myristate-13- acetate (PMA). The secreted cytokines acted additively to maintain and increase the number of colony-forming unit-megakaryocytes colonies (approximately 35%). These studies demonstrate the production of multiple cytokines by isolated human bone marrow megakaryocytes constitutively or stimulated in vitro. The capacity of human megakaryocytes to synthesize several cytokines known to modulate hematopoietic cells supports the concept that there may be an autocrine mechanism operative in the regulation of megakaryocytopoiesis. 相似文献
74.
Benjamin C. Sun MD MPP Helen R. Burstin MD MPH Troyen A. Brennan MD JD MPH 《Academic emergency medicine》2003,10(4):320-328
OBJECTIVE: To identify predictors and outcomes associated with frequent emergency department (ED) users. METHODS: Cross-sectional intake surveys, medical chart reviews, and telephone follow-up interviews of patients presenting with selected chief complaints were performed at five urban EDs during a one-month study period in 1995. Frequent use was defined by four or more self-reported, prior ED visits. Multivariate logistic regression identified predictors of frequent ED visitors from five domains (demographics, health status, health access, health care preference, and severity of acute illness). Associations between high use and selected outcomes were assessed with logistic regression models. RESULTS: All study components were completed by 2,333 of 3,455 eligible patients (67.5%). Demographics predicting frequent use included being a single parent, single or divorced marital status, high school education or less, and income of less than $10,000 (1995). Health status predictors included hospitalization in the preceding three months, high ratings of psychological distress, and asthma. Health access predictors included identifying an ED or a hospital clinic as the primary care site, having a primary care physician (PCP), and visiting a PCP in the past month. Choosing the ED for free care was the only health preference predictive of heavy use. Illness severity measures were higher in frequent visitors, although these were not independently predictive in the multivariate model. Outcomes correlated with heavy use include increased hospital admissions, higher rates of ED return visits, and lower patient satisfaction, but not willingness to return to the ED or follow-up with a doctor. CONCLUSIONS: Frequent ED visits are associated with socioeconomic distress, chronic illness, and high use of other health resources. Efforts to reduce ED visits require addressing the unique needs of these patients in the emergency and primary care settings. 相似文献
75.
76.
77.
78.
Arg-Gly-Asp-dependent occupancy of GPIIb/IIIa by applaggin: evidence for internalization and cycling of a platelet integrin 总被引:1,自引:0,他引:1
Using indirect immunofluorescence microscopy we examined the distribution and cycling of GPIIb/IIIa after binding to applaggin, a high-affinity Arg-Gly-Asp (RGD)--containing ligand. Resting, unfixed platelets were incubated with applaggin for 30 minutes at 37 degrees C, and bound applaggin was detected by an affinity-purified rabbit anti- applaggin antibody. Examination of intact cells showed a rim pattern for applaggin, consistent with its binding to the platelet surface. Staining of Triton X-100--permeabilized cells showed an intracellular pool of applaggin. Competition of applaggin binding by either AP-2, an anti-GPIIb/IIIa monoclonal antibody (MoAb) that blocks fibrinogen binding, or the synthetic peptide RGDW eliminated both surface and intracellular staining, indicating that applaggin is binding to GPIIb/IIIa in an RGD-dependent manner. Inhibition of platelet activation by PGE1 and theophylline had no effect on the observed staining patterns, indicating that cellular activation is not required for surface binding and subsequent internalization. To evaluate whether occupancy of functional binding sites on GPIIb/IIIa is required for internalization, we used mAb15, an anti-GPIIIa antibody that neither blocks fibrinogen binding nor induces the expression of ligand-induced binding sites on GPIIb/IIIa. In these studies mAb15 was internalized in a manner analogous to both AP-2 and applaggin, showing that occupancy of the RGD binding site is not required to initiate receptor internalization. To estimate the size of the newly internalized pool of applaggin, 125I-applaggin--binding studies were performed. Displacement of bound 125I-applaggin by excess unlabeled applaggin or EDTA showed that at least 17% of bound applaggin was nondisplaceable when binding was performed under conditions permitting membrane flow and internalization. These data indicate that GPIIb/IIIa is internalized in unstimulated platelets independent of cellular activation or occupancy of the functional binding site(s) of GPIIb/IIIa by RGD-containing ligands. Thus, internalization of GPIIb/IIIa may represent a mechanism by which the surface expression of this adhesion receptor is regulated. 相似文献
79.
Dr. Jerome M. Creenberg MD Bruce H. Dobun MD MPH David W. Shapiro MD JD Lawrence S. Linn PhD Neil S. Wenger MD MPH 《Journal of general internal medicine》1993,8(12):683-685
Advance directives, such as the durable power of attorney for health care (DPAHC), help patients and physicians make end-of-life health care decisions. Medical education should prepare student physicians to be knowledgeable about and comfortable with discussing advance directives. The authors developed an educational module for the third-year medical school curriculum and conducted a randomized trial to evaluate in students its effect on various outcome measures regarding the DPAHC. Over a six-week period, students who received written material about the DPAHC and a two-hour seminar significantly increased knowledge about and reported increased skill, comfort, and experience with the DPAHC. 相似文献
80.
The 14q+ chromosome in pre-B-ALL 总被引:2,自引:0,他引:2
A child who had acute lymphoblastic leukemia (ALL) associated with an 8;14 chromosome translocation and with a pre-B phenotype is described. The leukemic cells were determined to be pre-B-cells on the basis of intracytoplasmic mu-chain immunoglobulin (cIgM+) and the common-ALL antigen, lack of receptors for sheep erythrocytes, and lack of surface immunoglobulin. The 8;14 translocation is frequently found in patients with Burkitt's lymphoma and in most patients with B-cell ALL and is known to carry a poor prognosis. Thus far, no karyotypes have been reported for patients with pre-B-ALL. The present case indicates that a 14q+ chromosome may provide a proliferative advantage not only to cells with a B-cell phenotype, but also to pre-B-cells. The short survival of our patient also suggests that the 14q+ abnormality and the pre-B phenotype may signal a poor prognosis. 相似文献