首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2105篇
  免费   166篇
  国内免费   15篇
耳鼻咽喉   12篇
儿科学   107篇
妇产科学   130篇
基础医学   177篇
口腔科学   42篇
临床医学   205篇
内科学   437篇
皮肤病学   62篇
神经病学   75篇
特种医学   160篇
外科学   252篇
综合类   155篇
预防医学   179篇
眼科学   60篇
药学   105篇
  1篇
中国医学   74篇
肿瘤学   53篇
  2021年   24篇
  2019年   16篇
  2018年   27篇
  2017年   31篇
  2016年   29篇
  2015年   42篇
  2014年   56篇
  2013年   54篇
  2012年   78篇
  2011年   71篇
  2010年   67篇
  2009年   64篇
  2008年   65篇
  2007年   59篇
  2006年   57篇
  2005年   35篇
  2004年   36篇
  2003年   26篇
  2002年   23篇
  2001年   34篇
  2000年   20篇
  1999年   30篇
  1998年   49篇
  1997年   61篇
  1996年   51篇
  1995年   47篇
  1994年   55篇
  1993年   41篇
  1992年   26篇
  1991年   22篇
  1990年   17篇
  1989年   32篇
  1988年   39篇
  1987年   37篇
  1986年   32篇
  1985年   20篇
  1984年   22篇
  1983年   21篇
  1981年   25篇
  1980年   21篇
  1979年   16篇
  1978年   18篇
  1973年   18篇
  1959年   39篇
  1958年   59篇
  1957年   88篇
  1956年   45篇
  1955年   75篇
  1954年   68篇
  1953年   17篇
排序方式: 共有2286条查询结果,搜索用时 15 毫秒
41.
目的探讨子宫内膜微创术对不孕症妇女体外受精-胚胎移植(IVF-ET)妊娠结局的影响。方法选择2010年1月-2012年6月在新疆医科大学第一附属医院生殖助孕中心74例接受IVF-ET/卵胞浆内单精子注射(ICSI)的不孕症患者,以采用子宫内膜微创术的41例患者作为治疗组,在促排周期月经来潮24h内进行子宫内膜微创术;以未进行子宫内膜微创术的33例为对照组,比较两组的胚胎种植率及临床妊娠率。结果治疗组与对照组胚胎种值率分别26.51%和11.43%,差异有统计学意义(P<0.05);治疗组与对照组临床妊娠率分别为43.90%和21.21%,差异有统计学意义(P<0.05)。结论不孕症妇女进行子宫内膜微创术后能够显著提高IVF-ET/ICSI周期的胚胎种植率及临床妊娠率,改善妊娠结局。  相似文献   
42.
目的 探讨米非司酮对雌激素受体α(ERα)和孕激素受体(PR)在不同月经周期的子宫腺肌症中表达的影响.方法 47例行全子宫切除术的子宫腺肌症患者分为米非司酮组(n=24)和未用药组(n=23);无腺肌症的正常子宫内膜作为对照组(n=15).运用免疫组化的方法测定异位和在位子宫内膜及正常子宫内膜在不同月经周期的腺上皮及间质细胞中ERα和PR水平.结果 未用药组ERα和PR在异位子宫内膜腺上皮及间质细胞中的表达均低于在位内膜及对照组正常内膜(P<0.05).对照组及未用药组ERα和PR在在位内膜腺上皮细胞中的表达,增生期高于分泌期(P<0.05),而在未用药组异位内膜,差异无统计学意义(P>0.05).ERα和PR在异位和在位子宫内膜中的表达,米非司酮组低于未用药组(P<0.05).结论 ERα和PR在异位子宫内膜中的表达与在位子宫内膜不同;异位内膜丧失了正常内膜的周期性变化规律;米非司酮通过下调其性激素受体(ERα和PR)含量治疗子宫腺肌症.  相似文献   
43.
Baumhueter  S; Dybdal  N; Kyle  C; Lasky  LA 《Blood》1994,84(8):2554-2565
Extravasation of leukocytes into organized lymphoid tissues and into sites of inflammation is critical to immune surveillance. Leukocyte migration to peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN) and Peyer's patches (PP) depends on L-selectin, which recognizes carbohydrate-bearing, sialomucin-like endothelial cell surface glycoproteins. Two of these ligands have been identified at the molecular level. One is the potentially soluble mucin, GlyCAM 1, which is almost exclusively produced by high endothelial venules (HEV) of PLN and MLN. The second HEV ligand for L-selectin is the membrane-bound sialomucin CD34. Historically, this molecule has been successfully used to purify human pluripotent bone marrow stem cells, and limited data suggest that human CD34 is present on the vascular endothelium of several organs. Here we describe a comprehensive analysis of the vascular expression of CD34 in murine tissues using a highly specific antimurine CD34 polyclonal antibody. CD34 was detected on vessels in all organs examined and was expressed during pancreatic and skin inflammatory episodes. A subset of HEV-like vessels in the inflamed pancreas of nonobese diabetic (NOD) mice are positive for both CD34 and GlyCAM 1, and bind to an L-selectin/immunoglobulin G (IgG) chimeric probe. Finally, we found that CD34 is present on vessels of deafferentiated PLN, despite the fact that these vessels are no longer able to interact with L-selectin or support lymphocyte binding in vitro or trafficking in vivo. Our data suggest that the regulation of posttranslational carbohydrate modifications of CD34 is critical in determining its capability to act as an L-selectin ligand. Based on its ubiquitous expression, we propose that an appropriately glycosylated form of vascular CD34 may act as a ligand for L-selectin-mediated leukocyte trafficking to both lymphoid and nonlymphoid sites.  相似文献   
44.
Limited red blood cell (RBC) regeneration often prevents collection of sufficient blood from autologous donors. We studied the effects of subcutaneous recombinant erythropoietin (rEPO) in subjects making frequent blood donations. Six healthy iron-replete male subjects took rEPO (200 U/kg) subcutaneously daily, and donated blood (450 mL) twice a week for 3 weeks. During a control study, these subjects also attempted twice-weekly blood donations without rEPO. Four other males given rEPO, including one with idiopathic hemochromatosis, waited until day 8 to begin blood donations. All healthy subjects took oral ferrous sulfate. Subcutaneous rEPO given with blood donations resulted in a marked reticulocytosis (mean peak value 568 +/- 159 x 10(9)/L v 235 +/- 77 x 10(9)/L, control study; P < .05), and enhanced RBC production at 28 days (1,208 +/- 227 mL v 719 +/- 161 mL, P < .05). rEPO in advance of blood donations was slightly less effective in normal subjects (941 +/- 139 mL, P < .05); however, the subject with hemochromatosis produced substantially more RBCs (1,764 mL) than any normal subject. rEPO-treated normal subjects (but not the rEPO-treated patient with hemochromatosis or untreated controls) produced iron-deficient RBCs with elevated zinc protoporphyrin levels and low hemoglobin content. These cells appeared within 1 week of rEPO administration and before laboratory confirmation of depleted iron stores. Thus, subcutaneous rEPO is an effective stimulant of erythropoiesis in nonanemic blood donors. However, in addition to eventual depletion of iron stores, early functional iron deficiency affects response to the drug.  相似文献   
45.
Simon  SI; Rochon  YP; Lynam  EB; Smith  CW; Anderson  DC; Sklar  LA 《Blood》1993,82(4):1097-1106
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   
46.
47.
Petrequin  PR; Todd  RF d; Smolen  JE; Boxer  LA 《Blood》1986,67(4):1119-1125
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   
48.
49.
Phospholipase A2 levels in acute chest syndrome of sickle cell disease   总被引:4,自引:2,他引:4  
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   
50.
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   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号