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   532篇
  免费   25篇
  国内免费   19篇
耳鼻咽喉   1篇
儿科学   29篇
妇产科学   4篇
基础医学   54篇
口腔科学   30篇
临床医学   46篇
内科学   108篇
皮肤病学   5篇
神经病学   12篇
特种医学   110篇
外科学   22篇
综合类   9篇
预防医学   35篇
眼科学   3篇
药学   30篇
中国医学   2篇
肿瘤学   76篇
  2022年   3篇
  2019年   12篇
  2018年   9篇
  2017年   6篇
  2016年   10篇
  2015年   12篇
  2014年   8篇
  2013年   23篇
  2012年   7篇
  2011年   11篇
  2010年   26篇
  2009年   29篇
  2008年   13篇
  2007年   22篇
  2006年   10篇
  2005年   17篇
  2004年   18篇
  2003年   10篇
  2002年   11篇
  2001年   5篇
  2000年   10篇
  1999年   9篇
  1998年   30篇
  1997年   32篇
  1996年   27篇
  1995年   24篇
  1994年   25篇
  1993年   18篇
  1992年   4篇
  1991年   3篇
  1990年   7篇
  1989年   15篇
  1988年   16篇
  1987年   11篇
  1986年   15篇
  1985年   12篇
  1984年   6篇
  1983年   6篇
  1982年   12篇
  1981年   7篇
  1980年   6篇
  1978年   3篇
  1977年   1篇
  1976年   2篇
  1975年   6篇
  1972年   1篇
  1968年   1篇
  1966年   1篇
  1941年   1篇
  1910年   1篇
排序方式: 共有576条查询结果,搜索用时 15 毫秒
51.
收集脊柱损伤的信息对于脊髓损伤患者的诊断和治疗非常重要,设立脊髓损伤患者脊柱损伤基础数据集是为了规范脊柱损伤相关信息的收集方式和报告内容,学习并使用国际脊髓损伤脊柱损伤基础数据集,有助于规范和统一我国脊髓损伤患者脊柱损伤信息的收集,为相关治疗提供依据。本文将介绍国际脊髓损伤脊柱损伤基础数据集的研发过程,数据元素的内容以及数据编码的应用实例。  相似文献   
52.
A t(5;12)(q33;p13) translocation is a recurrent chromosome abnormality in a subgroup of myeloid malignancies with features of both myeloproliferative disorders and myelodysplastic syndromes (MDSs). The molecular consequence of a t(5;12) is a fusion between the platelet- derived growth factor receptor-B gene on chromosome 5 and a novel ETS- like gene, TEL, on chromosome 12. We report on three patients with a t(5;12)(q33;p13) diagnosed as chronic myelomonocytic leukemia, and one case of a t(10;12)(q24;p13) in a progressive MDS, with eosinophilia and monocytosis. Involvement of the TEL gene in these chromosome translocations was investigated by fluorescence in situ hybridization (FISH) with cosmid probes containing selectively the 5' end or 3' end of TEL. Hybridization of these cosmids to the der(5)/der(10) or a der(12), respectively, demonstrated a rearrangement of TEL in both translocations, showing that the t(10;12) is a variant translocation of the t(5;12). Cloning of the fusion cDNA of one case of t(5;12) showed that the breakpoint occurred at the RNA level at exactly the same position as reported by Golub et al (Cell 77:307, 1994). In addition, the TEL gene on chromosome 12 could be localized between two probes previously mapped to 12p13, namely PRB1 and D12S178, leading to a better definition of the position of TEL in this chromosome region. Moreover, in the case involving chromosome 10, the breakpoint occurred between cKTN206 and cKTN312/LYT-10 at 10q24. Clinicohematological data in these studies as well as the restriction mapping of chromosomal breakpoints strongly suggest that (1) common features in MDSs involving the TEL gene are monocytosis and eosinophilia, (2) chromosomes other than no. 5 may be involved and at least a t(10;12)(q24;p13) variant chromosome translocation does exist in these MDSs, and (3) both standard and variant 12p/TEL translocations may be identified by FISH with appropriate probes.  相似文献   
53.
A novel hematopoietic growth factor for primitive hematopoietic progenitor cells, the ligand for the flt3/flk2 receptor, (FL), has been recently purified and its gene has been cloned. In the present study, we investigated the effects of FL on the proliferation and differentiation of normal and leukemic myeloid progenitor cells. We demonstrate that FL is a potent stimulator of the in vitro growth of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin- 3 (IL-3), or G-CSF-dependent granulocyte-macrophage committed precursors from Lin- CD34+ bone marrow cells of normal donors. By contrast, FL does not affect the growth of erythroid-committed progenitors even in the presence of erythropoietin. The effect of FL on the proliferation and on the in vitro growth of clonogenic leukemic precursor cells was studied in 54 acute myeloid leukemia (AML) cases. Fresh leukemia blasts from 36 of 45 patients with AML significantly responded to FL without any relation to the French-American-British (FAB) subtype. FL stimulated the proliferation of leukemic blasts in a dose-dependent fashion. Synergistic activities were seen when FL was combined with G-CSF, GM-CSF, IL-3, or stem cell factor (SCF). FL as a single factor induced or increased significantly colony formation by clonogenic precursor cells from 21 of 24 patients with AML. In the presence of suboptimal and optimal concentrations of G-CSF, GM-CSF, IL3, SCF, or a combination of all factors, FL strongly enhanced the number of leukemic colonies (up to 18-fold). We also evaluated the induction of tyrosine phosphorylated protein on FL stimulation in fresh AML cells. We demonstrate that, on FL stimulation, a band of phosphorylated protein(s) of about 90 kD can be detected in FL- responsive, but not in FL-unresponsive cases. This study suggests that FL may be an important factor for the growth of myeloid leukemia cells, either as a direct stimulus or as a synergistic factor with other cytokines.  相似文献   
54.
Abughali  N; Dubyak  G; Tosi  MF 《Blood》1993,82(7):2182-2187
Neonatal neutrophils (polymorphonuclear leukocytes [PMN]) exhibit a well-documented deficiency in chemotaxis, the nature of which has not been fully elucidated. To determine whether impaired ability of neonatal PMN to increase hexose uptake in response to chemoattractants could contribute to this defect, we compared uptake of 2-deoxy-D- glucose (2-DOG) in stimulated versus resting PMN from neonates (cord blood) and healthy adults. Compared with unstimulated values; N-formyl- methionyl-leucyl-phenylalanine (fMLP) (optimal at 10 nmol/L) caused a threefold to fourfold increase in 2-DOG uptake by adult PMN. Unstimulated 2-DOG uptake by neonatal PMN was slightly higher than that for adult cells, but fMLP caused only a minimal (less than twofold) increase, and optimally stimulated uptake was significantly lower than for adult PMN (P < .01 for adult versus neonatal stimulated uptake; n = 6). Findings were similar when ionomycin or C5a was used as a stimulus. Optimal fMLP stimulation of adult PMN was associated with a marked decrease in the Km for 2-DOG uptake, from 0.74 +/- 0.11 to 0.23 +/- 0.03 mmol/L (delta Km = -0.51 +/- 0.12 mmol/L; n = 6). In contrast, there was relatively little fMLP-induced change in the Km for uptake of 2-DOG by neonatal PMN (from 0.44 +/- 0.04 mmol/L to 0.32 +/- 0.019 mmol/L n = 6); delta Km = -0.12 +/- 0.04 mmol/L; P = .011 for adult versus neonatal delta Km. Stimulation with fMLP was not accompanied by a significant change in the Vmax for 2-DOG uptake with either adult or neonatal PMN, and the respective values for Vmax were similar. We conclude that the chemoattractant-induced increase in hexose uptake by PMN is deficient in neonates compared with adults and that this deficiency involves mechanisms that determine the Km for this process. This impairment may contribute to defective chemotaxis in neonatal PMN.  相似文献   
55.
Freshly cultured vascular endothelial cells express the CD34 antigen in a diffuse cell surface pattern with some concentration on microvilli. Expression is downregulated with proliferation in continuous culture and undetectable after nine population doublings but can be maintained by restraining cell proliferation and promoting cell contact. Expression of CD34 at the antigen and mRNA levels on early passage cells is rapidly downregulated by interleukin-1 beta (IL-1 beta), interferon-gamma (INF-gamma), and tumor necrosis factor-alpha (TNF- alpha) under conditions in which these ligands upregulate the adhesion molecules: endothelial leukocyte adhesion molecule 1 (ELAM-1) and intracellular adhesion molecule 1 (ICAM-1). This reciprocal pattern of expression and the topographic distribution of CD34 molecules on the lumenal interdigitated microprocesses of adjacent endothelial cells in vivo suggest that CD34 might have a negative modulating role on adhesion functions of endothelia.  相似文献   
56.
57.
58.
A deficiency of adenosine deaminase, an enzyme important in purine nucleoside catabolism, is associated with a severe combined immunodeficiency disease in children. Inhibition of this enzyme in vitro and in vivo results in an impairment in lymphoblast proliferation. We have investigated the pharmacologic inhibition of this enzyme by 2'-deoxycoformycin in 15 patients with hematologic malignancies. Biochemical consequences of the administration of this agent were closely monitored in erythrocytes, nucleated peripheral blood and bone marrow cells, serum, and urine. A marked rise in erythrocyte dATP was accompanied by a depletion of ATP in those patients exhibiting toxicity. Most patients excreted large amounts of deoxyadenosine but not adenosine in the urine. Serum deoxyadenosine rose in patients demonstrating a marked decrease in cell mass. The biochemical disturbances and clinical toxicity, including hepatic, renal, and conjunctival abnormalities, were usually reversible. Central nervous system toxicity, which potentially was the most serious consequence, was associated with high erythrocyte dATP/ATP ratios and high levels of cerebrospinal fluid deoxyadenosine. In patients with lymphoma and leukemia, objective responses were observed but were short- lived. Patients with chronic lymphocytic leukemia receiving weekly low doses of the drug demonstrated minimal toxicity and some efficacy. The chemotherapeutic potential o 2'-deoxycoformycin, as either a single agent or in combination with Ara-A, merits further exploration.  相似文献   
59.
A case of transfusion-related acute lung injury (TRALI) due to HLA antibodies present in one unit of packed red blood cells led us to discuss the screening of HLA antibodies for female donors having been pregnant, and the use of labile blood products.  相似文献   
60.
BACKGROUND: Osteopenia with decreased bone mineral density (BMD) is a frequent finding in renal allograft recipients. Data concerning the bone architecture in these patients do not exist, however. METHODS: We compared the bone architecture of 33 randomly assigned women (age 49 +/- 12 years), who had received renal allografts 5.6 +/- 5.3 years before the investigation, with 74 women (age 50 +/- 14 years) who were admitted for osteodensitometry. All patients underwent single-energy computed tomography (SEQCT) and a midvertebral high-resolution tomography with computer-assisted analysis of the trabecular vertebral body architecture. RESULTS: Progressive alteration of bone architecture was associated with increasing vertebral height loss of the vertebral body. Height reduction of a vertebral body of more than 15% was associated with a significantly lower BMD (-2.3 +/- 0.8 versus -1.1 +/- 1.1 standard deviations below normal BMD), a lower trabecular bone area (13 +/- 8% versus 42 +/- 22%) and a lower trabecular diameter (1.4 +/- 0.5 mm versus 2.2 +/- 0.8 mm) compared to recipients without height reduction. In comparison to a matched group of patients with similarly reduced BMD (1.1 +/- 1.2 versus 1.2 +/- 1.1 SD below normal BMD), renal allograft recipients showed a lower number of trabecular plates (5.6 +/- 3.1 versus 7.0 +/- 3.7) and a smaller intertrabecular surface (54 +/- 116 mm versus 75 +/- 138 mm). CONCLUSIONS: Alterations of bone architecture in renal allograft recipients were associated with progressive vertebral height loss. Despite similar bone mineral density, differences of bone architecture could be observed between renal allograft recipients and patients with osteoporosis.   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