全文获取类型
收费全文 | 897篇 |
免费 | 62篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 35篇 |
妇产科学 | 39篇 |
基础医学 | 113篇 |
口腔科学 | 24篇 |
临床医学 | 94篇 |
内科学 | 212篇 |
皮肤病学 | 11篇 |
神经病学 | 20篇 |
特种医学 | 170篇 |
外科学 | 53篇 |
综合类 | 29篇 |
预防医学 | 42篇 |
眼科学 | 8篇 |
药学 | 68篇 |
肿瘤学 | 77篇 |
出版年
2021年 | 10篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 17篇 |
2012年 | 30篇 |
2011年 | 18篇 |
2010年 | 18篇 |
2009年 | 32篇 |
2008年 | 20篇 |
2007年 | 38篇 |
2006年 | 26篇 |
2005年 | 15篇 |
2004年 | 13篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 28篇 |
1998年 | 58篇 |
1997年 | 47篇 |
1996年 | 41篇 |
1995年 | 33篇 |
1994年 | 24篇 |
1993年 | 34篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 22篇 |
1989年 | 36篇 |
1988年 | 26篇 |
1987年 | 34篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 20篇 |
1980年 | 21篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1966年 | 3篇 |
排序方式: 共有998条查询结果,搜索用时 15 毫秒
41.
Cardoso AA; Schultze JL; Boussiotis VA; Freeman GJ; Seamon MJ; Laszlo S; Billet A; Sallan SE; Gribben JG; Nadler LM 《Blood》1996,88(1):41-48
Even if neoplastic cells express tumor associated antigens they still may fail to function as antigen presenting cells (APC) if they lack expression of one or more molecules critical for the induction of productive immunity. These cellular defects can be repaired by physiologic activation, transfection, or fusion of tumor cells with professional APC. Although such defects can be repaired, antitumor specific T cells may still fail to respond in vivo if they may have been tolerized. Here, human pre-B cell acute lymphoblastic leukemia (pre-B ALL) was used as a model to determine if primary human tumor cells can function as alloantigen presenting cells (alloAPC) or alternatively whether they induce anergy. In the present report, we show that pre-B cell ALL express alloantigen and adhesion molecules but uniformly lack B7-1 (CD80) and only a subset express B7-2 (CD86). Pre-B ALL cells are inefficient or ineffective alloAPC and those cases that lack expression of B7-1 and B7-2 also induce alloantigen specific T- cell unresponsiveness. Under these circumstances, T-cell unresponsiveness could be prevented by physiologic activation of tumor cells via CD40, cross-linking CD28, or signaling through the common gamma chain of the interleukin-2 receptor on T cells. Taken together, these results suggest that pre-B ALL may be incapable of inducing clinically significant T-cell-mediated antileukemia responses. This defect may be not only due to their inability to function as APC, but also due to their potential to induce tolerance. Attempts to induce clinically significant antitumor immune responses may then require not only mechanisms to repair the antigen presenting capacity of the tumor cells, but also reversal of tolerance. 相似文献
42.
Hematologic and immunomodulatory effects of an interleukin-1 receptor antagonist coinfusion during low-dose endotoxemia in healthy humans 总被引:3,自引:0,他引:3
Granowitz EV; Porat R; Mier JW; Orencole SF; Callahan MV; Cannon JG; Lynch EA; Ye K; Poutsiaka DD; Vannier E 《Blood》1993,82(10):2985-2990
Endotoxin is a component of gram-negative bacteria that causes hematologic and immunologic changes through its induction of cytokines. Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring inhibitor of IL-1 that competes with IL-1 for occupancy of cell-surface receptors but possesses no agonist activity. We investigated the ability of human recombinant IL-1Ra to block the effects of low-dose endotoxin. Fourteen healthy male volunteers between 18 and 30 years old were injected intravenously with 3 ng/kg Escherichia coli endotoxin. Concurrent with the injections, nine volunteers received a 3-hour continuous intravenous infusion of IL-1Ra. The other five subjects were given a 3-hour infusion of saline. Volunteers injected with endotoxin experienced a threefold increase in circulating neutrophils over baseline. This neutrophilia was significantly reduced by 48% in subjects administered endotoxin plus IL-1Ra (P = .0253). Ex vivo mitogen-induced peripheral blood mononuclear cell proliferation decreased by greater than 60% at 3 and 6 hours after endotoxin injection (P = .0053). This endotoxin-induced reduction in mitogen response was reversed in subjects coinjected with IL-1Ra (P = .0253). Endotoxin-induced symptoms, fever, and tachycardia were unaffected by IL-1Ra. IL-1 appears to be an important mediator in endotoxemia because some of its hematologic and immunomodulatory effects can be blocked by IL-1Ra. 相似文献
43.
The fate of the open canalicular system in surface and suspension- activated platelets 总被引:6,自引:0,他引:6
We have examined the movement of fibrinogen-gold (fgn-Au) complexes in platelets activated in suspension and by surface contact. Fgn-Au probes did not react with resting cells but were bound to the external membrane of platelets in suspension 5 seconds after addition of 1 U/mL of thrombin. At intervals over a period of 5 to 20 minutes, fgn-Au probes moved from the cell surface to peripheral and then deep channels of the open canalicular system (OCS). When platelets were surface activated by exposure to carbon-stabilized, formvar-coated grids for 5 to 20 minutes and then exposed to fgn-Au complexes for 5 minutes, probes were also observed in the OCS. At 5 minutes, over 40% of the platelets had concentrated fgn-Au in their OCS. Results after 10 minutes revealed 25% with gold-filled channels, 16% after 15 minutes, and 5% after 20 minutes. The decrease in frequency of OCS staining correlated with the increasing frequency of spread platelets, suggesting that tension produced by spreading may cause collapse of the OCS or that the OCS may evaginate onto the platelet during spreading. To evaluate the latter hypothesis, platelets were initially exposed to grids for 5 minutes and then incubated with fgn-Au for intervals of 5 to 20 minutes. The frequency of platelets with fgn-Au concentrated in the OCS was greatest at 5 minutes (44%) and decreased at the same rate as the frequency of spread platelets increased. Only 14.7% of the cells contained fgn-Au in the OCS after 20 minutes. These were primarily dendritic in form, while fully spread platelets rarely contained an OCS filled with the probe. The study indicates that fgn-Au particles are cleared to channels of the OCS independent of the mechanism of platelet activation. Fgn-Au that has been concentrated in the OCS at early stages of surface activation can be externalized during platelet spreading but remain internalized in suspension-activated cells. The OCS represents a membrane reservoir that can be evaginated onto the platelet surface during interaction with surfaces. 相似文献
44.
45.
46.
Warkentin TE; Hayward CP; Boshkov LK; Santos AV; Sheppard JA; Bode AP; Kelton JG 《Blood》1994,84(11):3691-3699
Heparin-induced thrombocytopenia is characterized by moderate thrombocytopenia and thrombotic complications, whereas quinine/quinidine-induced thrombocytopenia usually presents with severe thrombocytopenia and bleeding. Using flow cytometry and assays of procoagulant activity, we investigated whether sera from patients with these immune drug reactions could stimulate normal platelets to generate platelet-derived microparticles with procoagulant activity. Sera or purified IgG from patients with heparin-induced thrombocytopenia stimulated the formation of platelet-derived microparticles in a heparin-dependent fashion. Further studies showed that heparin-induced thrombocytopenia sera also produced a marked increase in procoagulant activity. In contrast, sera from patients with quinine- or quinidine-induced thrombocytopenia did not generate platelet-derived microparticles nor generate increased procoagulant activity. However, quinine/quinidine-induced thrombocytopenia sera produced a significant increase in the binding of IgG to platelets in a drug-dependent fashion, whereas sera from patients with heparin-induced thrombocytopenia demonstrated no drug-dependent binding of IgG to platelets. We also observed increased levels of circulating microparticles in patients with acute heparin-induced thrombocytopenia compared with control patients. Our observations indicate that the generation of procoagulant platelet-derived microparticles in vivo is a plausible explanation for the thrombotic complications observed in some patients with heparin-induced thrombocytopenia. 相似文献
47.
48.
Many people believe that euthanasia and assisted suicide are condoned carte blanche in the Netherlands. Not true. Both are formally forbidden by criminal law and can be administered only when certain procedures and criteria have been followed. Below, a look at the policies and practices regarding euthanasia and assisted suicide in The Netherlands and the role of nurses in this area. 相似文献
49.
50.
Symptomatic peripheral arterial disease: the value of a validated questionnaire and a clinical decision rule 下载免费PDF全文
Bianca LW Bendermacher Joep AW Teijink Edith M Willigendael Marie-Louise Bartelink Harry R Büller Ron JG Peters Jelis Boiten Machteld Langenberg Martin H Prins 《The British journal of general practice》2006,56(533):932-937
BACKGROUND: If a validated questionnaire, when applied to patients reporting with symptoms of intermittent claudication, could adequately discriminate between those with and without peripheral arterial disease, GPs could avoid the diagnostic measurement of the ankle brachial index. AIM: To investigate the Edinburgh Claudication Questionnaire (ECQ) in general practice and to develop a clinical decision rule based on risk factors to enable GPs to easily assess the likelihood of peripheral arterial disease. DESIGN OF STUDY: An observational study. SETTING: General practice in The Netherlands. METHOD: This observational study included patients of > or =55 years visiting their GP for symptoms suggestive of intermittent claudication or with one risk factor. The ECQ and the ankle brachial index were performed. The prevalence of peripheral arterial disease, defined as an ankle brachial index <0.9, was related to risk factors using logistic regression analyses, on which a clinical decision rule was developed and related to the presence of peripheral arterial disease. RESULTS: Of the 4790 included patients visiting their GP with symptoms suggestive of intermittent claudication, 4527 were eligible for analyses. The prevalence of peripheral arterial disease in this group was 48.3%. The sensitivity of the ECQ was only 56.2%. The prevalence of peripheral arterial disease in a clinical decision rule that included age, male sex, smoking, hypertension, hypercholesterolemia, and a positive ECQ, increased from 14% in the lowest to 76% in the highest category. CONCLUSION: This study indicates that the ECQ alone has an inadequate diagnostic value in detecting patients with peripheral arterial disease. The ankle brachial index should be performed to diagnose peripheral arterial disease in patients with complaints suggestive of intermittent claudication, although our clinical decision rule could help to differentiate between extremely high and lower prevalence of peripheral arterial disease. 相似文献