全文获取类型
收费全文 | 1221篇 |
免费 | 129篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 37篇 |
妇产科学 | 56篇 |
基础医学 | 304篇 |
口腔科学 | 17篇 |
临床医学 | 43篇 |
内科学 | 72篇 |
皮肤病学 | 7篇 |
神经病学 | 12篇 |
特种医学 | 96篇 |
外科学 | 21篇 |
综合类 | 104篇 |
预防医学 | 99篇 |
眼科学 | 248篇 |
药学 | 124篇 |
中国医学 | 6篇 |
肿瘤学 | 140篇 |
出版年
2023年 | 14篇 |
2022年 | 27篇 |
2021年 | 32篇 |
2020年 | 33篇 |
2019年 | 41篇 |
2018年 | 33篇 |
2017年 | 28篇 |
2016年 | 36篇 |
2015年 | 36篇 |
2014年 | 46篇 |
2013年 | 105篇 |
2012年 | 55篇 |
2011年 | 67篇 |
2010年 | 51篇 |
2009年 | 52篇 |
2008年 | 58篇 |
2007年 | 51篇 |
2006年 | 54篇 |
2005年 | 40篇 |
2004年 | 39篇 |
2003年 | 25篇 |
2002年 | 20篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 25篇 |
1998年 | 25篇 |
1997年 | 33篇 |
1996年 | 16篇 |
1995年 | 29篇 |
1994年 | 21篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 16篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1970年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有1389条查询结果,搜索用时 15 毫秒
21.
PURPOSE: The mouse eye is a widely used model for retinal disease and has potential to become a model for myopia. Studies of retinal disease will benefit from imaging the fundus in vivo. Experimental models of myopia often rely on manipulation of the visual experience. In both cases, knowledge of the optical quality of the eye, and in particular, the retinal image quality degradation imposed by the ocular aberrations is essential. In this study, we measured the ocular aberrations in the wild type mouse. METHODS: Twelve eyes from six four-week old black C57BL/6 wild type mice were studied. Measurements were done on awake animals, one being also measured under anesthesia for comparative purposes. Ocular aberrations were measured using a custom-built Hartmann-Shack system (using 680-nm illumination). Wave aberrations are reported up to fourth order Zernike polynomials. Spherical equivalent and astigmatism were obtained from the 2nd order Zernike terms. Modulation Transfer Functions (MTF) were estimated for the best focus, and through-focus, to estimate depth-of-focus. All reported data were for 1.5-mm pupils. RESULTS: Hartmann-Shack refractions were consistently hyperopic (10.12+/-1.41 D, mean and standard deviation) and astigmatism was present in many of the eyes (3.64+/-3.70 D, on average). Spherical aberration was positive in all eyes (0.15+/-0.07 microm) and coma terms RMS were significantly high compared to other Zernike terms (0.10+/-0.03 microm). MTFs estimated from wave aberrations show a modulation of 0.4 at 2c/deg, for best focus (and 0.15 without cancelling the measured defocus). For that spatial frequency, depth-of-focus estimated from through-focus modulation data using the Rayleigh criterion was 6D. Aberrations in the eye of one anesthetized mouse were higher than in the same eye of the awake animal. CONCLUSIONS: Hyperopic refractions in the mouse eye are consistent with previous retinoscopic data. The optics of the mouse eye is far from being diffraction-limited at 1.5-mm pupil, with significant amounts of spherical aberration and coma. However, estimates of MTFs from wave aberrations are higher than previously reported using a double-pass technique, resulting in smaller depth-of-field predictions. Despite the large degradation imposed by the aberrations these are lower than the amount of aberrations typically corrected by available correction techniques (i.e., adaptive optics). On the other hand, aberrations do not seem to be the limiting factor in the mouse spatial resolution. While the mouse optics are much more degraded than in other experimental models of myopia, its tolerance to large amounts of defocus does not seem to be determined entirely by the ocular aberrations. 相似文献
22.
【摘要】 目的 明确弥漫性大B细胞淋巴瘤患者常见的染色体改变及其与生存期的关系。方法 采用改进的染色体制备方法,对30例经病理活组织检查确诊的弥漫性大B细胞淋巴瘤患者进行染色体分析,并予相应的化疗方案处理,统计各组患者的生存期。结果 28例获得满意的染色体分裂象,其中5例染色体核型正常,8例为多倍体,4例发生t(14;18)(q32;q21),5例发生t(3;14)(q27;q32),2例发生t(2;3)(p11;q27),1例发生t(3;22)(q27;q11),2例涉及7号染色体与其他染色体间异位,1例涉及17号染色体与其他染色体间异位。染色体核型正常以及发生t(14;18)(q32;q21)和3q+改变的患者,生存期分别为(71.4±2.0)、(67.9±1.6)和(69.1±1.7)个月,较多倍体、7号染色体异常、17号染色体异常患者明显延长(均P<0.05)。Ⅰ+Ⅱ期患者中,正常染色体核型、t(14;18)(q32;q21)以及3q+患者生存期较发生多倍体改变患者以及7号染色体发生改变患者明显延长(P<0.05)。Ⅲ+Ⅳ期患者中,发生多倍体改变患者生存期亦较发生t(14;18)(q32;q21)、3q+以及正常染色体核型患者缩短(P<0.05)。且Ⅰ+Ⅱ期正常染色体核型、t(14;18)(q32;q21)、3q+以及多倍体患者与Ⅲ+Ⅳ期生存期比较,差异均有统计学意义(均P<0.05)。结论 依据恶性淋巴瘤患者染色体改变及其与恶性淋巴瘤分期等的相关性研究,可以预测淋巴瘤患者的治疗效果、生存期等。 相似文献
23.
Chromosomes in 1620 metaphases of ascitic fluid cells in 20 cases of ovariancarcinoma were analyzed.The results showed that there were marked structuralaberrations aside from significant increase in chromosomal numerical aberrations(85.2%).In the ascitic fluid cells from 12 patients,15 types of marker chromosomes were found,among which t(6;14)(q21;q24)and t(2;6)(q35;p12)were more frequently noted witha rate of 7.84% and 7.59% respectively,which was significantly higher than that of othermarker chromosomes(P<0.01).The findings suggested that,besides t(6;14)(q21;q24),t(2;6)(q35;p12)may also be a specific marker chromosome of ovarian carcinoma. 相似文献
24.
目的:分析产前诊断中异常核型与指征的关系及异常核型胎儿的调查随访,为遗传咨询提供可靠的依据。方法:对15413例具有产前诊断指征的妊娠妇女在知情同意的情况下,经B型超声引导行羊膜腔穿刺或脐带血穿刺,经培养处理后进行染色体核型分析。有220对胎儿核型异常的父母在知情同意的情况下进行外周血染色体核型分析,之后进行电话随访。结果:细胞培养成功率为99.6%(15349/15413),其中羊水细胞培养成功率99.76%(11299/11326),脐带血细胞培养成功率99.1%(4050/4087)。培养成功者染色体异常占11.20%(1719/15349),其中正常多态性占8.70%(1335/15349),染色体数目异常占1.72%(264/15349),结构异常占0.79%(121/15349)。按产前诊断指征分布筛查高危的核型异常率,唐氏综合征为10.67%(879/8236),高龄妊娠为9.76%(128/1312),不良孕产史为12.27%(138/1125),超声异常为11.41%(124/1087),胎儿畸形引产为23.91%(132/552)。异常核型的胎儿中有108例来自母亲,69例来自父亲,43例为新发生。结论:高危妊娠妇女行产前诊断染色体分析有助于减少出生缺陷。 相似文献
25.
26.
Factors affecting single-step transepithelial photorefractive keratectomy outcome in the treatment of mild, moderate, and high myopia: a cohort study 下载免费PDF全文
Mansour M. Al-Mohaimeed 《国际眼科》2022,15(5):786-792
AIM: To investigate the effect of preoperative factors on visual acuity, higher-order aberrations (HOAs), and index of success for spherical change (S.IOS) after transepithelial photorefractive keratectomy (t-PRK) for treating different grades of myopia.
METHODS: This was a retrospective one-armed cohort study where patients with high, moderate, or mild myopia treated with single-step t-PRK using Amaris 500 Hz excimer laser were evaluated for visual acuity, refractive status, corneal topography, HOAs, S.IOS, and mean efficiency and safety index before and 6mo after surgery.
RESULTS: A total of 154 eyes of 77 patients with mild (n=59), moderate (n=83), and high (n=12) myopia were reviewed. The efficiency and safety indices for vision recovery by single-step t-PRK were 98% and 100%, respectively. The achieved spherical equivalent (SE) was within 1 diopter (D) in 151 (98%) eyes. The median of the S.IOS was 1.18 [interquartile range (IQR) 1.0, 1.4]. The change in S.IOS was significantly correlated with age (P=0.007), 6.5 mm ablation zone (Mann-Whitney U test, P<0.01), and mild and moderate grade of myopia (Kruskal–Wallis test, P<0.001). Trefoil aberration, spherical aberration, and aberration coefficient types of HOA increased significantly (Wilcoxon test, P<0.001) 6mo post-surgery. There was a significant correlation between spherical aberration and aberration coefficient HOAs by myopia grades (P<0.05).
CONCLUSION: Single-step t-PRK has promising short-term outcomes for refractive corrections and vision improvement to treat all three grades of myopia. 相似文献
27.
报告1例首次发现的染色体异常核型家系,此家系2例患者为3号染色体部分单体,10号染色体部份三体。3例为3号染色体和10号染色体相互易位携带者。 相似文献
28.
29.
《International journal of radiation biology》2013,89(9):800-808
Purpose:?To estimate the biological doses for two severely exposed subjects (A and B) in a radiation accident in Shandong Jining, China in 2004.Materials and methods:?Conventional chromosome aberration analysis and cytokinesis-block micronuclei (CBMN) assay were performed in peripheral blood and bone marrow samples on two subjects after the accident. A new dose-effect curve and the nuclear division index (NDI) obtained from in vitro irradiation experiments using high dose of 60Co γ-rays were used to estimate the exposed doses.Results:?No metaphases or binucleated cells were observed in the peripheral blood cultures from either of the subjects. However, metaphases and binucleated cells were obtained from both subjects after bone marrow cultures. Both dicentric/ring and micronuclei yields were very high. The dose estimated for A and B were 20.0 Gy and 8.8 Gy, respectively, by dicentric/ring scoring, similar to the data by combination of the CBMN and NDI (CBMN?+?NDI) assay. The estimated doses by the two methods were in accordance with the clinical symptoms.Conclusion:?The new curve, together with the CBMN?+?NDI assay, are reliable for estimating higher doses of irradiation. In future radiation accidents, the accuracy and significance of these methods can be further tested. 相似文献
30.
目的探讨不良孕产史夫妇染色体异常核型检出率及其分布,以及染色体异常核型与不良孕产史的关系,为优生优育及遗传咨询提供理论依据。 方法选取2016年1月1日至2017年12月31日,于济南艾迪康医学检验中心进行染色体核型检测的10 330对(20 660例)不良孕产史育龄夫妇为研究对象。采集每例受试者肘静脉血3 mL,肝素钠抗凝,取0.3 mL进行血细胞培养、标本制备,采用常规G显带技术进行染色体核型分析。对于染色体异常核型检出率、不同类型染色体异常核型占染色体异常核型总例数的比例等计数资料,采用率(%)表示。本研究遵循的程序符合2013年修订的《世界医学协会赫尔辛基宣言》要求。 结果①本组10 330对(20 660例)不良孕产史育龄夫妇中,共计检出染色体异常核型为1 119例(不含染色体多态性),染色体异常核型检出率为5.42%(1 119/20 660)。其中,常染色体异常者为658例,占染色体异常核型的58.80%(658/1 119),包括354例染色体平衡易位、205例染色体倒位、83例染色体罗伯逊易位、11例染色体插入、5例染色体重复,分别占染色体异常核型的31.64%、18.32%、7.41%、0.98%、0.45%。染色体倒位者中,以9号染色体倒位居多,偶见于1、4、7、11、12号染色体,并且多合并自然流产。性染色体异常者为440例,占染色体异常核型的39.32%(440/1 119),包括365例性染色体数目异常(占染色体异常核型的32.62%)。其中,男性多表现为无精子症,以47,XXY染色体异常核型居多(144例),女性多表现为原发性不孕,以45,X染色体异常核型居多(103例); 61例为性染色体结构异常、14例为性别反转,分别占染色体异常核型的5.45%、1.25%。其他罕见染色体异常核型者为21例,占染色体异常核型的1.88%(21/1 119),如环状染色体、mar染色体等。②本组10 330对(20 660例)不良孕产史育龄夫妇中,11例为常染色体插入,5例为常染色体重复,54例为性染色体缺失,其主要临床表现为原发性不孕不育、胚胎停止发育、无精子症或重度少精子症。 结论染色体异常核型是导致育龄期夫妇不良孕产史的重要原因之一。对于不良孕产史夫妇,建议进行染色体核型分析和遗传咨询。临床为这类患者进行优生优育指导,可提高出生人口质量。 相似文献