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   628篇
  免费   36篇
  国内免费   46篇
耳鼻咽喉   2篇
儿科学   47篇
妇产科学   20篇
基础医学   64篇
口腔科学   37篇
临床医学   89篇
内科学   164篇
皮肤病学   13篇
神经病学   19篇
特种医学   118篇
外科学   25篇
综合类   10篇
预防医学   19篇
眼科学   3篇
药学   51篇
  1篇
肿瘤学   28篇
  2023年   5篇
  2022年   5篇
  2021年   5篇
  2019年   4篇
  2018年   10篇
  2017年   10篇
  2016年   11篇
  2015年   15篇
  2014年   19篇
  2013年   27篇
  2012年   10篇
  2011年   14篇
  2010年   19篇
  2009年   20篇
  2008年   8篇
  2007年   39篇
  2006年   16篇
  2005年   9篇
  2004年   3篇
  2003年   4篇
  2002年   11篇
  2001年   4篇
  2000年   7篇
  1999年   11篇
  1998年   44篇
  1997年   52篇
  1996年   54篇
  1995年   44篇
  1994年   30篇
  1993年   30篇
  1992年   2篇
  1991年   11篇
  1990年   7篇
  1989年   14篇
  1988年   24篇
  1987年   19篇
  1986年   14篇
  1985年   14篇
  1984年   6篇
  1983年   8篇
  1982年   9篇
  1981年   8篇
  1980年   11篇
  1978年   4篇
  1977年   8篇
  1976年   2篇
  1975年   4篇
  1973年   1篇
  1967年   1篇
  1960年   1篇
排序方式: 共有710条查询结果,搜索用时 15 毫秒
671.

Introduction

Since the late 1990s, a number of factors have reduced the threshold for parathyroidectomy in patients with primary hyperparathyroidism. This study examined whether this has translated into increased numbers of parathyroid operations over the last decade.

Methods

A retrospective analysis was performed of the Patient Episode Database for Wales and English Hospital Episode Statistics annual data from 2000 to 2010 for parathyroidectomy admissions per 100,000 population. Statistical analysis was by linear regression.

Results

Between 2000 and 2010 there were 24,247 parathyroid operations in England and Wales (0.005% of the population), with 3 times as many women treated as men. Overall, incidence of parathyroidectomy rose from 3.3/100,000 population in 2000 to 5.8/100,000 in 2010 (p<0.0001). In England, it increased from 3.3/100,000 population to 5.8/100,000 and in Wales, it increased from 2.4/100,000 population to 4.6/100,000. Despite similar population demographics, the difference in the rate of change between England and Wales was significant (p<0.05). Uptake also varied according to age; in those aged 0–14 years, incidence of parathyroidectomy remained static whereas in all other age groups, uptake of parathyroidectomy increased significantly from 2000 to 2010. Most notably, surgical intervention in those aged 60–74 and >75 years nearly doubled over the decade (p<0.0001).

Conclusions

The incidence of parathyroidectomy in adults has increased significantly in the last decade in England and Wales. This likely reflects changes in population demography, available guidelines, lower threshold for referral, changing surgical approach and the realisation that surgical morbidity is now infrequent.  相似文献   
672.
Introduction: High-risk human papillomavirus (hrHPV) testing is expected to replace cytology as primary screening method for cervical cancer screening in an increasing number of countries. The high sensitivity of hrHPV testing is combined with a limited specificity which makes triaging of hrHPV positive women necessary. As an ideal triage method does not yet exist, an optimal triage strategy for hrHPV positive women based on current knowledge should be obtained. The aim of this article is to present an overview of available options for triage of hrHPV positive women, with their strengths and limitations and possible future opportunities.

Areas covered: Current knowledge on morphological biomarkers, molecular biomarkers and combined triage strategies will be discussed to give an overview of the state-of-the-art on triaging hrHPV positive women. The literature search was limited to studies on triage strategies for hrHPV positive women.

Expert commentary: Experience with morphology-based biomarkers makes these a valuable triage method. However, they lack the ability of differentiating productive from transforming infections. Molecular biomarkers are objective, highly reproducible, can be used in high throughput testing, and show promising results. With more extensive knowledge on these molecular markers, cervical cancer screening may transform to a full molecular screening in the future.  相似文献   

673.
硒谷胱甘肽过氧化物酶保护心肌作用机制   总被引:5,自引:0,他引:5  
通过人工半合成及天然低成饲料喂养豚鼠,在出现组织硒水平及谷胱甘肽过氧化物酶(GP)活性明显降低同时,动物红细胞、心肌细胞等的膜结构出现异常,膜脂组成中的磷脂减少.代表细胞膜老化指数的胆固醇/磷脂的分子比增加,作为心肌线粒体内膜必需界面脂的心磷脂明显减少,线粒体能量转换的关键呼吸酶.细胞色素氧化酶(CCO)活性明显降低,同时代表其二级结构的园二色谱异常,208nm峰及224n峰明显降低.各型脂质过氧化产物,如代表膜磷脂自由基氧化损伤初级产物的脂氢过氧化物、续发产物的丙二醛、呼气烷烃和脂过氧化物聚集产物的荧光色脂均明显增加。这可能正是30多年前Neubert等(1962)提出GP对细胞膜的保护作用,尤其所谓线粒体“收缩因子”(“Contraction factor”)作用的机制所在。  相似文献   
674.
Fortier  N; Snyder  LM; Garver  F; Kiefer  C; McKenney  J; Mohandas  N 《Blood》1988,71(5):1427-1431
In vitro induced oxidative damage to normal human RBCs has previously been shown to result in increased membrane rigidity as a consequence of the generation of a protein complex between hemoglobin and spectrin. In order to determine if in vivo generated hemoglobin-spectrin complexes may play a role in increased membrane rigidity of certain pathologic red cells, we measured both these parameters in membranes prepared from hereditary xerocytosis (Hx), sickle cell disease (Sc), and red cells from thalassemia minor (beta thal). Membranes were prepared from density-fractionated red cells, and membrane deformability was measured using an ektacytometer. Hemoglobin-spectrin complex was determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel analysis, as well as by Western blot analysis using a monoclonal antibody against the beta- subunit of hemoglobin. For these three types of pathologic red cells, progressive cellular dehydration was associated with increased membrane rigidity and increased content of hemoglobin-spectrin complex. Moreover, the increase in membrane rigidity appeared to be directly related to the quantity of hemoglobin-spectrin complex associated with the membrane. Our findings imply that hemoglobin-spectrin complex is generated in vivo, and this in turn results in increased membrane rigidity of certain pathologic red cells. The data further suggest that oxidative crosslinking may play an important role in the pathophysiology of certain red cell disorders.  相似文献   
675.
To further elucidate the natural history of human immunodeficiency virus (HIV) infection, we studied intermediate HIV-related conditions occurring before acquired immunodeficiency syndrome (AIDS) in a prospectively observed multicenter cohort of 738 HIV-infected persons with hemophilia. We analyzed the frequency in adults and children of common HIV-related conditions and the relative risk of AIDS after occurrence of these conditions, controlling for age at seroconversion and the percentage of CD4+ lymphocytes. Thrombocytopenia was the most frequently observed condition with cumulative incidences of 43% +/- 7% in adults and 27% +/- 6% in children and adolescents by 10 years after seroconversion. Oral candidiasis, fever, weight loss, and non-AIDS pneumonia were two to four times more common in adults than children, whereas herpes zoster risk was similar in the two age groups. HIV- related conditions were infrequent during the first 4 years of infection, particularly in children. With the exception of thrombocytopenia, mean CD4 counts were less than 350 cells/microL at the onset of the conditions. The relative hazard of AIDS after oral candidiasis was 18 in children and 3.8 in adults. Relative hazard in adults was also increased after persistent fever (10), weight loss (3.2), and non-AIDS pneumonia (2.2). Herpes zoster and thrombocytopenia were not significantly associated with AIDS in either age group. We conclude that intermediate HIV-related conditions occur more frequently in adults than in children with hemophilia. Persistent fever is the strongest predictor of AIDS in adults, whereas oral candidiasis is the strongest predictor in children. These findings should facilitate the design and conduct of clinical trials as well as the management of HIV- infected children and adults.  相似文献   
676.
Primary bone marrow blasts from 4 children with t(8;21) acute myeloid leukemia (AML), 6 children with inv(16) AML, and 2 children with t(9;11) AML were injected intravenously or transplanted under the kidney capsule of sublethally irradiated mice with severe combined immunodeficiency (SCID). Leukemic cells from all AML patients infiltrated the SCID mouse thymus, suggesting that the thymic microenvironment supports the survival and growth of human AML blasts. Blasts from 1 of 4 t(8;21) AML patients and 4 of 6 inv(16) AML patients caused histopathologically detectable disseminated leukemia. Blasts from the remaining patients produced disseminated occult leukemia that was only detected by polymerase chain reaction. Occurrence of histopathologically detectable disseminated leukemia was dependent on intravenous injection of leukemic cells; none of the mice challenged with an inoculum transplanted under the kidney capsule developed overt leukemia. No obvious association was noted between occurrence of leukemia in SCID mice and clinical or laboratory features presented by patients, including age, sex, or leukocyte count at diagnosis. To our knowledge, this study is the first to show that leukemic blasts from children with newly diagnosed AML, especially inv(16) AML, can cause disseminated human leukemia in SCID mice without exogenous cytokine support. The SCID mouse model system may prove particularly useful for designing more effective treatment strategies against childhood AML.  相似文献   
677.
Previous reports have indicated that the nucleotide affinity analog 5'- p-fluorosulfonylbenzoyl adenosine (FSBA) at concentrations between 40 and 100 mumol/L and at times greater than 20 minutes covalently modifies a single protein component on the external platelet membrane surface and that adenosine diphosphate (ADP) protects against this reaction. That this protein is an ADP receptor linked to platelet activation is shown by FSBA inhibition of ADP-mediated platelet shape change, aggregation, and fibrinogen receptor exposure. In this report, further evidence for the interaction of FSBA with the ADP receptor on platelets is provided by the observation that FSBA at high concentrations (100 to 500 mumol/L) behaves as a weak agonist to produce platelet shape change within one minute as detected by spectroscopic assay and scanning electron microscopy with concomitant phosphorylation of the light chain of platelet myosin. The specificity of FSBA as an agonist is demonstrated by inhibition of FSBA-induced shape change by ATP and the covalent incorporation of SBA as well as the failure of 5'-fluorosulfonylbenozoyl guanosine (FSBG) to cause shape change. In contrast, incubation of platelets with low concentrations of [3H]-FSBA (40 mol/L) is not associated with stimulation of platelet shape change or myosin light chain phosphorylation.  相似文献   
678.
Guinan  EC; Gribben  JG; Boussiotis  VA; Freeman  GJ; Nadler  LM 《Blood》1994,84(10):3261-3282
The above story illustrates the translation of basic scientific discoveries to the clinic. In vitro and preclinical in vivo experimentation suggests that modulation of the B7:CD28 pathway will result in either amplification or suppression of the immune response. Considering the frequency with which diseases characterized by either inadequate or dysregulated immune function present to the practicing hematologist or oncologist, it is not difficult to envisage clinical applications for reagents that modulate this pathway. However, we still have much to learn about the function and clinical potential of this and other potentially redundant costimulatory pathways and therefore we suspect that this story will become considerably more complex over the next few years.  相似文献   
679.
Smith  CL; Pilarski  LM; Egerton  ML; Wiley  JS 《Blood》1989,74(6):2038-2042
The thymus is a site of active T-lymphoid cell proliferation and DNA synthesis. In this study, the capacity of human thymocytes for nucleoside transport was assessed both by cytosine arabinoside influx and by equilibrium binding of nitrobenzylmercaptopurine riboside (NBMPR), a specific ligand for the equilibrative nucleoside transporter of leukocytes. The proportion of freshly isolated thymocytes synthesizing DNA was 8.6% +/- 2.1% (n = 12) by 3H-thymidine labeling index and 7.8% +/- 2.9% (n = 4) S-phase cells by flow cytometric analysis of DNA content. In comparison, both methods gave proliferation S-phase values less than 1% for peripheral blood lymphocytes (PBLs). Thymocytes expressed a high density of specific NBMPR binding sites (26,068 +/- 8,776 sites per cell, n = 12) as compared with PBLs (1,123 +/- 553 sites per cell, n = 8). The initial influx of cytosine arabinoside into thymocytes was 14-fold greater than into PBLs, and in both cell types the influx of nucleoside was totally inhibited by 0.5 mumol/L NBMPR, which is known to inhibit the major equilibrative nucleoside transporter in white blood cells. Depletion of mature CD3+ cells from the thymocyte preparation by anti-CD3 antibody left a residual population with both increased labeling index and up to twofold greater density of NBMPR binding sites. When PBLs were cultured for 48 hours with the T-cell mitogen phytohemagglutinin, a 40-fold increase in labeling index was observed, together with a 30-fold increase in the density of specific NBMPR binding sites. Thus, fresh thymocytes from human thymus are actively proliferating and express high densities of a functional nucleoside transporter. The more immature cells in the thymocyte population which are proliferating more actively have a greater density of nucleoside transporters than the whole population. In contrast, mitotically inactive PBLs-have few nucleoside transporters, but after mitogenic stimulation PBLs express large numbers of this transmembrane molecule.  相似文献   
680.
Palek  J; Liu  SC; Snyder  LM 《Blood》1978,51(3):385-395
The discocyte-echinocyte transformation and the decrease in deformability associated with red cell ATP depletion have been attributed to changes in the physical properties of spectrin and actin, membrane proteins located at the membrane-cytosol interface. We investigated the spontaneous formation of spectrin-rich complexes in human erythrocyte membranes, employing two-dimensional SDS- polyacrylamide gel electrophoresis. Membranes of red cells depleted in ATP under aerobic conditions exhibited (1) an increase in components 4.5 and 8 and globin subunits, (2) a spontaneous formation of heterodimers of spectrin 1 + 2 and spectrin 2 + component 4.9, and (3) a large molecular weight (greater than 10(6) daltons) protein complex with a high spectrin to band 3 ratio. These complexes were dissociated with dithiothreitol and were prevented by anaerobic incubation or the maintenance of red cell ATP and GSH levels with glucose, adenine, and inosine. The complexes 1 + 2 and 2 + 4.9 were also seen in acetylphenylhydrazine-treated, glucose-6-phosphate dehydrogenase- deficient fresh erythrocytes that showed marked GSH depletion but preserved greater than 70% of the original ATP level. However, membranes of these cells did not contain the greater 10(6) dalton aggregate with a high spectrin to band 3 ratio. We concluded that the formation of the latter complex results from rearrangement of spectrin and other polypeptides in membranes of ATP-depleted red cells. Under aerobic conditions, the rearranged proteins undergo spontaneous intermolecular crosslinkings through disulfide couplings.  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