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   250篇
  免费   22篇
  国内免费   8篇
儿科学   32篇
妇产科学   1篇
基础医学   27篇
口腔科学   7篇
临床医学   29篇
内科学   80篇
皮肤病学   1篇
神经病学   4篇
特种医学   41篇
外科学   14篇
综合类   6篇
预防医学   20篇
眼科学   1篇
药学   6篇
肿瘤学   11篇
  2022年   1篇
  2021年   3篇
  2019年   1篇
  2018年   1篇
  2017年   1篇
  2016年   3篇
  2015年   8篇
  2014年   10篇
  2013年   8篇
  2012年   5篇
  2011年   3篇
  2010年   6篇
  2009年   9篇
  2008年   1篇
  2007年   7篇
  2006年   5篇
  2005年   7篇
  2004年   6篇
  2003年   4篇
  2002年   2篇
  2001年   4篇
  2000年   2篇
  1999年   4篇
  1998年   20篇
  1997年   17篇
  1996年   19篇
  1995年   17篇
  1994年   15篇
  1993年   13篇
  1992年   1篇
  1991年   2篇
  1990年   5篇
  1989年   11篇
  1988年   9篇
  1987年   8篇
  1986年   3篇
  1985年   5篇
  1984年   4篇
  1983年   3篇
  1982年   4篇
  1981年   6篇
  1980年   3篇
  1979年   2篇
  1978年   3篇
  1977年   7篇
  1976年   1篇
  1972年   1篇
排序方式: 共有280条查询结果,搜索用时 15 毫秒
1.
2.
Hydrosalpinges adversely affect markers of endometrial receptivity   总被引:22,自引:10,他引:22  
While in-vitro fertilization (IVF) was initially developed in women with tubal factor infertility, recent clinical studies have suggested that the presence of hydrosalpinges lowers implantation and pregnancy rates. We postulated that these hydrosalpinges cause impaired endometrial receptivity. A total of 103 women with hydrosalpinges were prospectively evaluated, and compared with 55 infertile and 44 fertile controls. All women had endometrial biopsies during the window of implantation, analysed by conventional histological criteria, and also stained for three integrin markers of endometrial receptivity (alpha1beta1, alpha4beta1 and alpha vbeta3). Women with hydrosalpinges (cases) expressed significantly less of the alpha vbeta3 integrin compared with controls. There was no difference in expression of alpha1beta1 or alpha4beta1 among groups. A significantly greater number of cases had out of phase histology and missing alpha vbeta3 (type I defects) and absent integrin expression despite normal histological maturation (type II) defects, compared with controls. Of 20 women with impaired endometrial receptivity who were also biopsied after hydrosalpinx surgery, 70% demonstrated increased alpha vbeta3 expression. Seventy-seven percent of type I and 57% of type II defects were corrected postoperatively. Using markers of endometrial receptivity, this study demonstrates that inflammatory hydrosalpinges have an adverse effect on endometrial receptivity, which in some cases may be overcome by surgical treatment of the hydrosalpinx.   相似文献   
3.
Proliferative expansion and apoptotic cell death play prominent roles in T cell development. The molecular control of cell cycle progression and apoptosis appear to be inter-connected since the Bcl-2 protein can inhibit apoptosis and slow cell cycle progression in cortical thymocytes and mature T cells, particularly during the transition from the quiescent state into the cell cycle. Here the impact of bcl-2 transgene expression on CD3-CD4-CD8- T cell progenitors was assessed. Bcl-2 enhanced the survival of these progenitors at all of the four major differentiation stages, CD25- CD44+ (pro-T1), CD25 + CD44+ (pro- T2), CD25 + CD44- (pro-T3) and CD25-CD44- (pro-T4). However, it reduced cell cycling and slowed turnover only in the pro-T4 subset. From an analysis of bcl-2 transgenic mice expressing a TCR transgene or bearing a mutation in the scid or rag-1 gene we conclude that Bcl-2 inhibits proliferation only of T cell progenitors that are activated via the pre- TCR, not those stimulated via c-Kit and the IL-7 receptor.   相似文献   
4.
Parathyroid hormone secretion is negatively regulated by a 7- transmembrane domain, G-protein coupled Ca(2+)-sensing receptor. We hypothesized that activating mutations in this receptor might cause autosomal dominant hypoparathyroidism (ADHP). Consistent with this hypothesis, we identified, in two families with ADHP, heterozygous missense mutations in the Ca(2+)-sensing receptor gene that cosegregated with the disorder. None of 50 normal controls had either mutation. We also identified a de novo, missense Ca(2+)-sensing receptor mutation in a child with severe sporadic hypoparathyroidism. The amino acid substitution in one ADHP family affected the N-terminal, extracellular domain of the receptor. The other mutations involved the transmembrane region. Unlike patients with acquired hypoparathyroidism, patients with these mutations had hypercalciuria even at low serum calcium concentrations. Their greater hypercalciuria presumably reflected activation of Ca(2+)-sensing receptors in kidney cells, where the receptor negatively regulates calcium reabsorption. This augmented hypercalciuria increases the risk of renal complications and thus has implications for the choice of therapy.   相似文献   
5.
BACKGROUND: If a validated questionnaire, when applied to patients reporting with symptoms of intermittent claudication, could adequately discriminate between those with and without peripheral arterial disease, GPs could avoid the diagnostic measurement of the ankle brachial index. AIM: To investigate the Edinburgh Claudication Questionnaire (ECQ) in general practice and to develop a clinical decision rule based on risk factors to enable GPs to easily assess the likelihood of peripheral arterial disease. DESIGN OF STUDY: An observational study. SETTING: General practice in The Netherlands. METHOD: This observational study included patients of > or =55 years visiting their GP for symptoms suggestive of intermittent claudication or with one risk factor. The ECQ and the ankle brachial index were performed. The prevalence of peripheral arterial disease, defined as an ankle brachial index <0.9, was related to risk factors using logistic regression analyses, on which a clinical decision rule was developed and related to the presence of peripheral arterial disease. RESULTS: Of the 4790 included patients visiting their GP with symptoms suggestive of intermittent claudication, 4527 were eligible for analyses. The prevalence of peripheral arterial disease in this group was 48.3%. The sensitivity of the ECQ was only 56.2%. The prevalence of peripheral arterial disease in a clinical decision rule that included age, male sex, smoking, hypertension, hypercholesterolemia, and a positive ECQ, increased from 14% in the lowest to 76% in the highest category. CONCLUSION: This study indicates that the ECQ alone has an inadequate diagnostic value in detecting patients with peripheral arterial disease. The ankle brachial index should be performed to diagnose peripheral arterial disease in patients with complaints suggestive of intermittent claudication, although our clinical decision rule could help to differentiate between extremely high and lower prevalence of peripheral arterial disease.  相似文献   
6.
7.
OBJECTIVE: To establish criteria for the diagnosis of medium chain acyl-CoA dehydrogenase (MCAD) deficiency in the UK population using a method in which carnitine species eluted from blood spots are butylated and analysed by electrospray ionisation tandem mass spectrometry (ESI-MS/MS). DESIGN: Four groups were studied: (1) 35 children, aged 4 days to 16.2 years, with proven MCAD deficiency (mostly homozygous for the A985G mutation, none receiving carnitine supplements); (2) 2168 control children; (3) 482 neonates; and (4) 15 MCAD heterozygotes. RESULTS: All patients with MCAD deficiency had an octanoylcarnitine concentration ([C8-Cn]) > 0.38 microM and no accumulation of carnitine species > C10 or < C6. Among the patients with MCAD deficiency, the [C8-Cn] was significantly lower in children > 10 weeks old and in children with carnitine depletion (free carnitine < 20 microM). Neonatal blood spots from patients with MCAD deficiency had a [C8-Cn] > 1.5 microM, whereas in heterozygotes and other normal neonates the [C8-Cn] was < 1.0 microM. In contrast, the blood spot [C8-Cn] in eight of 27 patients with MCAD deficiency > 10 weeks old fell within the same range as five of 15 MCAD heterozygotes (0.38-1.0 microM). However, the free carnitine concentrations were reduced (< 20 microM) in the patients with MCAD deficiency but normal in the heterozygotes. CONCLUSIONS: Criteria for the diagnosis of MCAD deficiency using ESI-MS/MS must take account of age and carnitine depletion. If screening is undertaken at 7-10 days, the number of false positive and negative results should be negligible. Because there have been no instances of death or neurological damage following diagnosis of MCAD deficiency in our patient group, a strong case can be made for neonatal screening for MCAD deficiency in the UK.  相似文献   
8.
IntroductionWe assessed the practice of surgeons regarding venous thromboembolism (VTE) chemical prophylaxis for total hip replacement (THR) and total knee replacement (TKR), before and after issuing of updated National Institute for Health and Care Excellence (NICE) guidance in 2018.MethodsA survey, circulated through the British Hip Society and regional trainee networks/collaboratives, was completed by 306 UK surgeons at 187 units. VTE chemical prophylaxis prescribing patterns for surgeons carrying out primary THR (n=258) and TKR (n=253) in low-risk patients was assessed after publication of 2018 NICE recommendations. Prescribing patterns before and after the NICE publication were subsequently explored.ResultsFollowing the new guidance, 34% (n=87) used low-molecular-weight heparin (LMWH) alone, 33% (n=85) aspirin (commonly preceded by LMWH) and 31% (n=81) direct oral anticoagulants (DOACs: with/without preceding LMWH) for THR. For TKR, 42% (n=105) used aspirin (usually monotherapy), 31% (n=78) LMWH alone and 27% (n=68) DOAC (with/without preceding LMWH). NICE guidance changed the practice of 34% of hip surgeons and 41% of knee surgeons, with significantly increased use of aspirin preceded by LMWH for THR (before=25% vs after=73%; p<0.001), and aspirin for TKR (before=18% vs after=84%; p<0.001). Significantly more regimens were NICE guidance compliant after the 2018 update for THR (before=85.7% vs after=92.6%; p=0.011) and TKR (before=87.0% vs after=98.8%; p<0.001).ConclusionOver one-third of surveyed surgeons changed their VTE chemical prophylaxis in response to 2018 NICE recommendations, with more THR and TKR surgeons now compliant with latest NICE guidance. The major change in practice was an increased use of aspirin for VTE chemical prophylaxis.  相似文献   
9.
目的:一些理论质疑富血小板血浆对骨前体细胞成骨分化的作用,本实验拟验证富血小板血浆对体外培养的人骨髓间充质干细胞成骨分化的抑制效应。方法:实验于2005-05/11在南方医科大学组织工程试验室(省级)完成。①实验方法:抽取6名健康志愿者髂前上棘骨髓5mL进行体外细胞培养扩增,静脉血10mL以二次离心法制得富血小板血浆。诱导骨髓间充质干细胞时富血小板血浆与骨髓间充质干细胞均来自同一个体。②碱性磷酸酶染色:取第4代骨髓间充质干细胞,分为两组:富血小板血浆组加入富血小板血浆使终浓度为100g/L,单纯血清培养组仅加入等量胎牛血清。培养后第7天进行碱性磷酸酶染色,阳性细胞为胞质中呈现黑色颗粒或块状沉淀。③矿化结节染色:取第4代骨髓间充质干细胞,分组同上。培养后第19天以0.1%茜素红-TrisHcl(pH8.3)37℃下放置30min,矿盐沉积染色阳性为红色。④Cbfa1基因表达:取第4代骨髓间充质干细胞,分组同上。培养后第3,7,12,16天RT-PCR法检测骨髓间充质干细胞Cbfa1基因的表达。⑤形态学观察:实验过程中使用相差显微镜观察各组细胞生长情况及形态学变化。结果:①骨髓间充质干细胞碱性磷酸酶染色结果:培养后第7天,富血小板血浆组碱性磷酸酶阳性细胞数量较单纯血清培养组明显减少,且阳性细胞内灰黑色颗粒也明显减少,为弱阳性。②骨髓间充质干细胞矿化结节染色结果:培养后第19天,单纯血清培养组可见细胞表面有较多的矿盐沉积,但未形成明显的矿化结节。富血小板血浆组细胞表面只有稀少的矿盐沉积。③骨髓间充质干细胞cbfa1mRNA的表达:培养后第3,7,12,16天,随着培养时间的延长单纯血清培养组与富血小板血浆组cbfa1基因表达量均逐渐增高,同一时间点两组间cbfa1基因的表达基本相似。④骨髓间充质干细胞形态学变化:富血小板血浆组骨髓间充质干细胞增殖旺盛,细胞达到单层汇合的时间较单纯血清培养组明显缩短。单纯血清培养组细胞在完全汇合后开始出现聚合现象(14~16d),但趋向性不明显,未完全形成团簇;富血小板血浆组细胞在完全汇合后未出现聚合现象,细胞密集生长。培养初期两组细胞以梭形为主,多角形细胞较少,培养至14~16d单纯血清培养组多角形细胞较富血小板血浆组增多。结论:富血小板血浆可抑制人骨髓间充质干细胞碱性磷酸酶的分泌与矿盐沉积,对人骨髓间充质干细胞成骨分化的直接效应是抑制其分化。  相似文献   
10.
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