全文获取类型
收费全文 | 1605篇 |
免费 | 82篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 94篇 |
妇产科学 | 106篇 |
基础医学 | 137篇 |
口腔科学 | 42篇 |
临床医学 | 165篇 |
内科学 | 332篇 |
皮肤病学 | 56篇 |
神经病学 | 26篇 |
特种医学 | 145篇 |
外科学 | 126篇 |
综合类 | 135篇 |
预防医学 | 100篇 |
眼科学 | 10篇 |
药学 | 90篇 |
1篇 | |
中国医学 | 74篇 |
肿瘤学 | 52篇 |
出版年
2021年 | 16篇 |
2020年 | 13篇 |
2018年 | 15篇 |
2017年 | 18篇 |
2016年 | 14篇 |
2015年 | 35篇 |
2014年 | 42篇 |
2013年 | 46篇 |
2012年 | 53篇 |
2011年 | 51篇 |
2010年 | 57篇 |
2009年 | 46篇 |
2008年 | 50篇 |
2007年 | 40篇 |
2006年 | 43篇 |
2005年 | 23篇 |
2004年 | 19篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 24篇 |
2000年 | 12篇 |
1999年 | 21篇 |
1998年 | 43篇 |
1997年 | 55篇 |
1996年 | 47篇 |
1995年 | 43篇 |
1994年 | 57篇 |
1993年 | 35篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 30篇 |
1988年 | 29篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1959年 | 35篇 |
1958年 | 58篇 |
1957年 | 87篇 |
1956年 | 45篇 |
1955年 | 75篇 |
1954年 | 67篇 |
1953年 | 17篇 |
1952年 | 14篇 |
1949年 | 10篇 |
排序方式: 共有1700条查询结果,搜索用时 15 毫秒
41.
We have recently found that antibodies to L-selectin, the homing receptor on neutrophils, are as effective as those to beta 2-integrin at blocking formyl peptide-stimulated aggregation. Therefore, we investigated the requirements for expression of L-selectin and beta 2- integrin on adjacent cells during aggregation. Fluorescence flow cytometry allowed characterization of aggregates on the basis of size and color, as well as antibody binding to these two adhesive molecules. Formyl peptide-stimulated aggregate formation was measured for individual populations fluorescently labeled red (LDS-751) or green (CD44-FITC), and interpopulation red-green cell conjugates. Blocking either the beta 2-integrin or L-selectin adhesive epitope with monoclonal antibody on individual cell populations resulted in an approximately 50% reduction in two-color aggregation as compared with that in unblocked samples. Shedding the L-selectin on a cell population by preincubation with complexes of lipopolysaccharide and its plasma membrane binding protein also decreased aggregation to a control population by approximately 50%. We examined the aggregation of neutrophils from patients genetically deficient in beta 2-integrin and clinically leukocyte adhesion deficient (LAD). LAD adhesion to normal neutrophils was dependent on the expression of L-selectin on LAD cells and beta 2-integrin on normal cells. Thus, the minimum requirement for adhesion between two mixed populations of neutrophils was that one population expressed the beta 2-integrin and the other expressed the L- selectin adhesive epitope. 相似文献
42.
43.
The widespread assumption that cytoplasts generated from human polymorphonuclear leukocytes (PMNs) are vesicles consisting solely of cytoplasm surrounded by plasma membrane and devoid of granule activity remains to be tested. PMN cytoplasts were prepared by centrifugation of intact cells on a Ficoll step gradient in the presence of cytochalasin B. Two granule membrane markers, Mol, a fluorometrically detectable antigen, and cytochrome b, both of which have been shown to translocate to the plasma membrane during granule release, were compared for their activity in cytoplasts and intact PMNs. We found that the amount of Mol detected on the plasma membrane of intact PMNs, as compared with other membrane markers (such as antigens LFA-1 and beta 2m), increased 1.6- fold upon exposure of PMNs to Ficoll plus cytochalasin B prior to centrifugation. Another twofold increase in Mol expression occurred upon cytoplast preparation. Release of the granule enzymes, vitamin B12- binding protein, and lysozyme were also followed and correlated well (r = .78 and .92) with the amount of Mol antigen present on the cell surface. Cytochrome b was also found to be higher (1.4-fold) on plasma membranes isolated from cytoplasts than on plasma membranes isolated from intact control cells. These results indicate that some fusion of granule membranes and plasma membranes occurred during treatment of PMNs with Ficoll plus cytochalasin b and during cytoplast preparation. 相似文献
44.
45.
Marrow samples from 89 patients with aplastic anemia (AA) were evaluated for their ability to grow stromal layers in standard long- term marrow cultures (LTMCs). Results were highly variable: 6.8% failed to grow any stromal cells (group I); 42.5% either failed to grow to confluency or appeared to have a decreased number of adipocytes and/or macrophages (group II); and 52.8% appeared as normal confluent cultures with fibroblasts, adipocytes, and macrophages (group III). Analyses of patient data suggested that group I patients had a longer disease duration and poorer survival (P = .07). Enzyme-linked immunosorbent assay analysis of cytokine production was performed on 20 of the normal- appearing AA LTMCs and 12 LTMCs established from normal donors. Significant differences between the AA and control groups were apparent for macrophage inflammatory protein-1 alpha (MIP-1 alpha), interleukin- 1 receptor antagonist (IL-1ra), granulocyte-macrophage colony- stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G- CSF), and leukemia-inhibitory factor (LIF). The most dramatic differences observed were elevated levels of MIP-1 alpha and GM-CSF and decreased levels of IL-1ra, particularly after IL-1 alpha stimulation. In contrast, IL-1 alpha stimulation of AA LTMCs produced levels of IL- 6, LIF, and G-CSF comparable with those of controls. These data suggest that defects exist within the microenvironment of some AA marrows. Whether the majority of these defects are the cause or consequence of aplasia is not clear. However, we speculate that some of these abnormalities may contribute to the maintenance of the hypoplastic state and, in extreme cases, prevent engraftment of donor marrow. 相似文献
46.
Styles LA; Schalkwijk CG; Aarsman AJ; Vichinsky EP; Lubin BH; Kuypers FA 《Blood》1996,87(6):2573-2578
Acute chest syndrome (ACS) is associated with significant morbidity and is the leading cause of death in patients with sickle cell disease (SCD). Recent reports suggest that bone marrow fat embolism can be detected in many cases of severe ACS. Secretory phospholipase A2 (sPLA2) is an important inflammatory mediator and liberates free fatty acids, which are felt to be responsible for the acute lung injury of the fat embolism syndrome. We measured SPLA2 levels in 35 SCD patients during 20 admissions for ACS, 10 admissions for vaso-occlusive crisis, and during 12 clinic visits when patients were at the steady state. Eleven non-SCD patients with pneumonia were also evaluated. To determine if there was a relationship between sPLA2 and the severity of ACS we correlated SPLA2 levels with the clinical course of the patient. In comparison with normal controls (mean = 3.1 +/- 1.1 ng/mL), the non- SCD patients with pneumonia (mean = 68.6 +/- 82.9 ng/mL) and all three SCD patient groups had an elevation of SPLA2 (steady state mean = 10.0 +/- 8.4 ng/mL; vaso-occlusive crisis mean = 23.7 +/- 40.5 ng/mL; ACS mean = 336 +/- 209 ng/mL). In patients with ACS sPLA2 levels were 100- fold greater than normal control values, 35 times greater than values in SCD patients at baseline, and five times greater than non-SCD patients with pneumonia. The degree of SPLA2 elevation in ACS correlated with three different measures of clinical severity and, in patients followed sequentially, the rise in SPLA2 coincided with the onset of ACS. The dramatic elevation of SPLA2 in patients with ACS but not in patients with vaso-occlusive crisis or non-SCD patients with pneumonia and the correlation between levels of SPLA2 and clinical severity suggest a role for SPLA2 in the diagnosis and, perhaps, in the pathophysiology of patients with ACS. 相似文献
47.
Andrea LA?TOVKOVá Pavlina KLUSá?KOVá Zdenka FENCLOVá Vincent BONNETERRE Daniela PELCLOVá 《Industrial health》2015,53(6):562-568
The objective of this study is to describe a case-series of potassium aluminium
tetrafluoride (KAlF4)-induced occupational asthma (OA) and/or occupational
rhinitis (OR). The study involves five patients from a heat-exchanger production line who
were examined (including specific inhalation challenge tests) for suspected OA and/or OR
caused by a flux containing almost 100% KAlF4 − with fluorides’ workplace air
concentrations ranging between 1.7 and 2.8 mg/m3. No subject had a previous
history of asthma. All five patients had a positive specific challenge test (three
patients were diagnosed with OA alone, one with OR and one with both OR and OA). At the
follow-up visit, after three years on average, all patients needed permanent
corticosteroid therapy (four topical, one oral). After elimination from the exposure, only
one of the observed subjects gave an indication of an improvement, two subjects stabilized
and two worsened. Our case series focuses on the correlation between patients’ exposure to
fluorides in air-conditioner production and the subsequent occurrence of OR/OA. Currently,
it is uncertain whether these OR/OA were caused by hypersensitivity or irritation. 相似文献
48.
目的探讨腹腔镜手术对不孕症患者的诊断及治疗价值。方法回顾性分析新疆医科大学第一附属医院2010年9月-2014年5月收治的319例不孕症患者的临床资料,对所有患者行腹腔镜下诊断及相应的手术治疗(包括盆腔粘连分解、输卵管造口术、输卵管灼断术等)。结果 319例患者腹腔镜术中检查与术前子宫输卵管碘油造影结果的符合率为72.1%(230/319),其中有43例术中发现子宫肌瘤,56例术中发现输卵管系膜囊肿,8例患者术中发现子宫内膜异位症,有2例患者诊断为盆腔结核,1例术中发现结肠肌瘤(术前考虑卵巢囊肿),其余为不同程度的盆腔慢性炎症。轻度粘连69例,妊娠21例,宫外孕2例,妊娠率33.33%。中重度粘连250例,其中行灼断术34例,灼断术患者后行体外受精及胚胎移植(IVF-ET),妊娠13例,妊娠率38.23%(13/34)。其余216例,失访3例,妊娠31例,宫外孕3例、妊娠率15.9%。结论腹腔镜对诊断输卵管性不孕及盆腔疾病有重要价值,子宫输卵管造影仅能初级筛查,诊断价值有限。在治疗输卵管粘连梗阻中,腹腔镜的治疗价值有待进一步探讨,临床预后与盆腔炎症的程度有关,应个体化选择手术方案。 相似文献
49.
Induction of proliferation of B prolymphocytic leukemia cells by phorbol ester and native or recombinant interferon-gamma 总被引:1,自引:0,他引:1
Phorbol ester phorbol myristate acetate (PMA) induces proliferation in nonmalignant human B cells and B cells from a patient with B prolymphocytic leukemia (B-PLL). Mitogen-free T cell-derived conditioned medium acts synergistically with PMA in inducing proliferation of B-PLL cells but does not enhance the PMA-stimulated outgrowth of nonmalignant B cells. Interleukin 2 (IL-2) has no effect on the outgrowth of B-PLL cells, and monoclonal antibodies against the IL-2 receptor do not influence the response to PMA and conditioned medium. Recombinant interferon-gamma (IFN-gamma), in contrast, is a potent enhancer of PMA-induced proliferation of B-PLL cells. With gel filtration techniques and with the use of anti-IFN-gamma antibodies, it is shown that IFN-gamma in the conditioned medium is responsible for the observed increase in B-PLL cell proliferation. Preincubation of B- PLL cells with IFN-gamma induces responsiveness to PMA, whereas IFN- gamma alone had no effect on these cells when pretreated with PMA. The combined data show that, in the presence of PMA, native and recombinant IFN-gamma are growth factors for B cells from a B-PLL patient and that IL-2 is not involved in this process. 相似文献
50.
A New Variant of Hereditary Hemolytic Anemia With Stomatocytosis and Erythrocyte Cation Abnormality 总被引:4,自引:1,他引:4
MILLER DENIS R.; RICKLES FREDERICK R.; LICHTMAN MARSHALL A.; LA CELLE PAUL L.; BATES JONATHAN; WEED ROBERT I. 《Blood》1971,38(2):184-204
A new variant of congenital hemolyticanemia associated with stomatocytosis,reticulocytosis, decreased osmotic fragility, type I autohemolysis and shortened erythrocyte survival without specific splenic sequestration was discoveredin three siblings of Swiss-German ancestry. Increased intracellular sodium(two to three times normal) and slightlydecreased intracellular potassium weredetected. Total sodium efflux was eight-fold greater than normal but total potassium influx was normal and ouabain-sensitive potassium influx was decreased.The ouabain-sensitive sodium efflux:potassium influx ratio was 26:1 ratherthan the 3:2 ratio noted in normal cells.The consanguineous parents, four othersiblings, and 44 other family membershad mild stomatocytosis, reticulocytosis,and, when studied, decreased osmoticfragility, increased autohemolysis, intermediate abnormalities of cation content,cation flux, and moderate shortening oferythrocyte survival. Autosomal dominant inheritance was suggested. Noabnormalities of RBC enzymes, hemoglobin or lipids were observed. No abnormalities of membrane protein weredetected on acrylamide gel. Substratedepletion of these hypermetabolic cellsresulted in intracellular dehydrationwith potassium loss in excess of sodiumgain and decreased deformability. Although the exact nature of the defectresponsible for hemolysis is unknown,this syndrome differs from other hereditary hemolytic anemias associated withstomatocytosis. Submitted on December 21, 1970 Revised on March 16, 1971 Accepted on March 29, 1971 相似文献