全文获取类型
收费全文 | 3239篇 |
免费 | 240篇 |
国内免费 | 14篇 |
专业分类
耳鼻咽喉 | 79篇 |
儿科学 | 261篇 |
妇产科学 | 60篇 |
基础医学 | 328篇 |
口腔科学 | 68篇 |
临床医学 | 364篇 |
内科学 | 653篇 |
皮肤病学 | 48篇 |
神经病学 | 171篇 |
特种医学 | 428篇 |
外科学 | 417篇 |
综合类 | 78篇 |
一般理论 | 2篇 |
预防医学 | 214篇 |
眼科学 | 47篇 |
药学 | 158篇 |
1篇 | |
中国医学 | 1篇 |
肿瘤学 | 115篇 |
出版年
2022年 | 21篇 |
2021年 | 42篇 |
2020年 | 35篇 |
2019年 | 49篇 |
2018年 | 62篇 |
2017年 | 45篇 |
2016年 | 43篇 |
2015年 | 53篇 |
2014年 | 69篇 |
2013年 | 93篇 |
2012年 | 107篇 |
2011年 | 110篇 |
2010年 | 90篇 |
2009年 | 85篇 |
2008年 | 112篇 |
2007年 | 85篇 |
2006年 | 104篇 |
2005年 | 104篇 |
2004年 | 102篇 |
2003年 | 87篇 |
2002年 | 105篇 |
2001年 | 86篇 |
2000年 | 71篇 |
1999年 | 71篇 |
1998年 | 111篇 |
1997年 | 110篇 |
1996年 | 107篇 |
1995年 | 75篇 |
1994年 | 75篇 |
1993年 | 67篇 |
1992年 | 78篇 |
1991年 | 84篇 |
1990年 | 71篇 |
1989年 | 95篇 |
1988年 | 78篇 |
1987年 | 75篇 |
1986年 | 63篇 |
1985年 | 73篇 |
1984年 | 60篇 |
1983年 | 53篇 |
1982年 | 38篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 36篇 |
1978年 | 27篇 |
1976年 | 19篇 |
1975年 | 27篇 |
1974年 | 22篇 |
1970年 | 19篇 |
1969年 | 18篇 |
排序方式: 共有3493条查询结果,搜索用时 46 毫秒
101.
Discovery and characterization of a selective, nonpeptidyl thrombopoietin receptor agonist 总被引:2,自引:0,他引:2
Erickson-Miller CL DeLorme E Tian SS Hopson CB Stark K Giampa L Valoret EI Duffy KJ Luengo JL Rosen J Miller SG Dillon SB Lamb P 《Experimental hematology》2005,33(1):85-93
OBJECTIVE: Peptide and other small molecule agonists have been described for several cytokines and growth factors. Hydrazone compounds described here as thrombopoietin receptor agonists were identified as activating STAT proteins in a Tpo responsive cell line. METHODS: STAT activation and analysis of signal transduction pathways in cell lines and normal human platelets was elucidated by Western blot and electrophoretic mobility shift assays. Proliferation assays in cell types responsive to other cytokines determined specificity for Tpo receptor. Flow cytometry quantified differentiation of CD34(+) cells into CD41(+) megakaryocytes and platelet production in vitro. RESULTS: Activation of STAT5, mitogen-activated protein kinase, p38, and early response genes by SB 394725 was similar to that induced by Tpo. SB 394725 induced a reporter gene response under a STAT activation promoter as well as the megakaryocyte-specific gpIIb promoter. The compound induced proliferation of Tpo responsive lines but demonstrated no activity in cell lines responding to other cytokines, i.e., erythropoietin, granulocyte-colony stimulating factor, interleukin-3, interferon-gamma. The response of normal human Tpo receptors was elucidated by measuring growth and differentiation of human bone marrow in vitro. Activation of endogenous Tpo receptors by SB 394725 was demonstrated in human and chimp platelets, but not in platelets of other species including mouse, dog, rabbit, or cynomolgus monkey. CONCLUSIONS: SB 394725, a small molecule with a molecular weight of 452 Da, is capable of activating Tpo-specific signal transduction, proliferation, and differentiation responses similar to the responses and functions of the protein growth factor, Tpo. 相似文献
102.
Reduction in renal blood flow following acute increase in the portal pressure: evidence for the existence of a hepatorenal reflex in man? 总被引:3,自引:3,他引:3 下载免费PDF全文
BACKGROUND: To investigate the relation between changes in portal haemodynamics and renal blood flow (RBF) in patients with cirrhosis. PATIENTS/METHODS: Twenty patients with cirrhosis and transjugular intrahepatic portosystemic stent-shunts were divided into two groups which were well matched. At routine portography, either changes in unilateral RBF (group I) or changes in cardiac output (group II) before and after shunt occlusion were studied. Blood was obtained from the renal and systemic circulations for the measurement of neurohumoral factors before and after shunt occlusion in group I patients. RESULTS: After shunt occlusion, there was a progressive reduction in unilateral RBF from a mean (SD) of 289 (32) to 155 (25) (-43.5%) (p < 0.001). These changes correlated significantly with the changes in the portal atrial gradient (p < 0.001). There was no significant change in heart rate, mean arterial pressure and right atrial pressure. No significant changes were found in the concentrations of the various neurohumoral factors measured. There was a less notable but significant reduction in the cardiac output (-10.9%) (p = 0.02) unaccompanied by significant reduction in the pulmonary capillary wedge pressure or mean arterial pressure. CONCLUSIONS: These results suggest the existence of hepatorenal reflex in man which is important in the regulation of RBF, although other mechanisms may also be contributory. 相似文献
103.
Cross-sectional and M-mode echocardiograms were performed on 23 consecutive patients with infective endocarditis. Both M-mode and cross-sectional echocardiography identified vegetations in 18 patients, 10 of whom required valve replacement within 1 month of presentation. Cross-sectional echocardiography alone identified a vegetation in one patient with a prosthetic valve. Neither technique identified vegetations in five instances. The size and shape of a vegetation on cross-sectional echocardiography did not accurately predict the need for early valve replacement of the incidence of major peripheral emboli. 相似文献
104.
High force development and crossbridge attachment in smooth muscle from swine carotid arteries 总被引:2,自引:0,他引:2
In experiments designed to achieve maximal activation, the active force/cell cross-sectional area in tissues prepared from the swine carotid media was 6.7 +/- 0.3 (sd) X 10(5) N/m5. This value exceeds that reported for other vertebrate muscle cells and is striking because of the low smooth muscle myosin content. The hypothesis that high force generation may, in part, reflect an increase in the crossbridge duty cycle, i.e., the fraction of the cycle during which force is generated, was tested by determining the rate of force redevelopment after a step shortening and the ration of the load-bearing capacity of the contractile system to the developed stress during the course of isometric contractions. Maximal crossbridge cycling rates estimated by the rate of force redevelopment occurred 30 seconds after the onset of a high K+-induced contraction, and decreased thereafter, although the load-bearing capacity or maximum active stress was maintained. These results from isometric experiments support the hypothesis and provide further evidence that attached, non-cycling crossbridges contribute to force maintenance in tonically contracting arterial smooth muscle. 相似文献
105.
Pandey Manish Peetermans Marijke Doyle Andrew J. Dillon Richard Meadows Christopher I. S. 《Journal of artificial organs》2021,24(3):387-391
Journal of Artificial Organs - Veno-venous extracorporeal membrane oxygenation (ECMO) is typically instituted in severe respiratory failure, defined by Lung Injury Score, and caused either by... 相似文献
106.
S Mukherjee K Abhinav PJ Revington 《Annals of the Royal College of Surgeons of England》2015,97(1):66-72
IntroductionThe aim of this study was to determine the incidence and patterns of cervical spine injury (CSI) associated with maxillofacial fractures at a UK trauma centre.MethodsA retrospective analysis was conducted of 714 maxillofacial fracture patients presenting to a single trauma centre between 2006 and 2012.ResultsOf the 714 maxillofacial fracture patients, 2.2% had associated CSI including a fracture, cord contusion or disc herniation. In comparison, 1.0% of patients without maxillofacial trauma sustained a CSI (odds ratio: 2.2, p=0.01). The majority (88%) of CSI cases of were caused by a road traffic accident (RTA) with the remainder due to falls. While 8.8% of RTA related maxillofacial trauma patients sustained a CSI, only 2.0% of fall related patients did (p=0.03, not significant). Most (70%) of the CSIs occurred at C1/C2 or C6/C7 levels. Overall, 455, 220 and 39 patients suffered non-mandibular, isolated mandibular and mixed mandibular/non-mandibular fractures respectively. Their respective incidences of CSI were 1.5%, 1.8% and 12.8% (p=0.005, significant). Twelve patients with concomitant CSI had their maxillofacial fractures treated within twenty-four hours and all were treated within four days.ConclusionsThe presence of maxillofacial trauma mandates exclusion and prompt management of cervical spine injury, particularly in RTA and trauma cases involving combined facial fracture patterns. This approach will facilitate management of maxillofacial fractures within an optimum time period. 相似文献
107.
Alloimmunization to platelets in heavily transfused patients with sickle cell disease 总被引:2,自引:0,他引:2
Bone marrow transplantation (BMT) is now an option for some patients with sickle cell disease (SCD). Many SCD patients are multiply transfused with red blood cells (RBCs), and may be immunized to alloantigens other than erythrocyte antigens. Because platelet refractoriness is a significant complication during BMT, we wished to determine the prevalence of alloimmunization to platelets in transfused SCD patients. Sera collected from 47 transfused and 14 untransfused SCD patients were screened for HLA and platelet-specific antibodies. Transfusion and RBC antibody histories were reviewed. A subset of the patients were rescreened 1 year later. Eighty-five percent of patients with at least 50 RBC transfusions (22 of 26), 48% of patients with less than 50 transfusions (10 of 21), and none of 14 untransfused patients demonstrated platelet alloimmunization (P < .05). Platelet alloimmunization was more prevalent than RBC alloimmunization (20% to 30%). Half of the platelet reactivity was chloroquine-elutable. Eighteen of 22 patients (82%) on chronic RBC transfusion remained platelet-alloimmunized 11 to 22 months after initial testing. In summary, 85% of heavily transfused SCD patients are alloimmunized to HLA and/or platelet-specific antigens. These patients may be refractory to platelet transfusion, a condition that would increase their risk during BMT. Leukodepletion in the transfusion support of SCD patients should be considered to prevent platelet alloimmunization. 相似文献
108.
We have previously reported that lithium chloride (LiCl) stimulates the production of granulocyte-macrophage colony-forming cells (GM-CFC), pluripotent stem cells (CFU-S), and differentiated granulocytes, macrophages and megakaryocytes in murine Dexter marrow cultures and that this effect appears to be mediated indirectly by a radioresistant adherent marrow cell. In this study we have established that exposure of murine Dexter cultures to LiCl (4 mEq/L) causes an increase of colony-forming cell megakaryocytes (CFU-meg) over 1 to 6 weeks of culture in both supernatant (188% to 611%) and stromal phases (123% to 246%). Moreover, we have shown that lithium treatment of either irradiated (1,100 rad) or unirradiated stromal cells increased production of activities stimulating formation of megakaryocyte, granulocyte, macrophage, and mixed lineage colonies and proliferation of the factor-dependent cell line, FDC-P1. This FDC-P1 stimulatory activity was completely blocked by an antibody to purified recombinant granulocyte-macrophage colony stimulating factor (rGM-CSF). The baseline or lithium-induced--stromal-derived bone marrow colony stimulating activity was partially blocked by the antibody to rGM-CSF and by an antibody to purified colony stimulating factor I (CSF-1); the two antibodies combined resulted in greater than 90% inhibition of the lithium-induced marrow stimulatory activity. In addition, radioimmunoassay (RIA) showed that although CSF-1 was detectable in supernatants of these cultures, exposure to lithium did not increase CSF-1 levels. These data indicate that Dexter stromal cells produce CSF- 1 and GM-CSF and that lithium appears to exert its stimulatory effects on in vitro myelopoiesis by inducing production of GM-CSF. 相似文献
109.
Immunologic status of hemophilia patients treated with cryoprecipitate or lyophilized concentrate 总被引:1,自引:0,他引:1
We evaluated 37 patients with moderate or severe hemophilia A and six patients with severe factor IX deficiency for clinical or laboratory evidence of immune abnormalities. Patients were assigned to one of four groups according to the type of clotting factor replacement. Twenty patients had received only cryoprecipitate during the two years preceding the evaluation (group I); 11 additional patients were treated predominantly with cryoprecipitate but had also received up to nine bottles of factor VIII concentrate (group II); six patients received factor VIII concentrate (group III); six patients received factor IX concentrate (group IV). There was no clinical or laboratory evidence of immunodeficiency among the 43 patients. The mean absolute number of Th cells was normal in all patient groups, but the mean absolute number of Ts cells was increased compared with controls, both in patients treated with cryoprecipitate and in patients treated with factor VIII or factor IX concentrate. There was no correlation between the Th/Ts ratio and patient age, alanine aminotransferase level, hepatitis serology, in vitro lymphocyte function, or amount of clotting factor administered. Our observations demonstrate that the volunteer or commercial origin of clotting factor replacement cannot fully explain the alterations in lymphocyte subset distribution previously described in patients with hemophilia A. 相似文献
110.
Mark T Dillon Christopher F Ake Mary F Burke Anshuman Singh Edward H Yian Elizabeth W Paxton Ronald A Navarro 《Acta orthopaedica》2015,86(3):286-292