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   1158篇
  免费   87篇
  国内免费   9篇
耳鼻咽喉   7篇
儿科学   3篇
妇产科学   3篇
基础医学   153篇
口腔科学   75篇
临床医学   47篇
内科学   57篇
皮肤病学   27篇
神经病学   218篇
特种医学   22篇
外科学   51篇
综合类   66篇
预防医学   8篇
眼科学   480篇
药学   28篇
中国医学   6篇
肿瘤学   3篇
  2024年   1篇
  2023年   8篇
  2022年   10篇
  2021年   44篇
  2020年   25篇
  2019年   23篇
  2018年   22篇
  2017年   34篇
  2016年   31篇
  2015年   46篇
  2014年   53篇
  2013年   54篇
  2012年   55篇
  2011年   56篇
  2010年   52篇
  2009年   66篇
  2008年   37篇
  2007年   65篇
  2006年   45篇
  2005年   55篇
  2004年   44篇
  2003年   45篇
  2002年   37篇
  2001年   38篇
  2000年   30篇
  1999年   20篇
  1998年   28篇
  1997年   22篇
  1996年   13篇
  1995年   14篇
  1994年   16篇
  1993年   13篇
  1992年   11篇
  1991年   18篇
  1990年   22篇
  1989年   12篇
  1988年   9篇
  1987年   12篇
  1986年   9篇
  1985年   17篇
  1984年   14篇
  1983年   8篇
  1982年   6篇
  1981年   5篇
  1980年   4篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
排序方式: 共有1254条查询结果,搜索用时 20 毫秒
1.
廖珊  刘可 《国际眼科杂志》2022,22(7):1123-1126

随着人们生活水平的不断提高和生活方式的多样化发展,获得更好的视觉质量已成为现阶段手术治疗白内障的新目标。角膜散光直接影响白内障手术功能性人工晶状体(IOL)种类的选择和患者术后视功能的恢复,角膜散光检查的种类不再局限于单一的散光数值,而是细分成角膜前表面散光、后表面散光、全角膜散光以及高阶角膜散光等,相应的检查设备及技术也有较多更新。临床医生可根据不同设备特点及应用范围,选择适合的检查设备评估术前角膜散光情况,为制定更精准的屈光性白内障手术规划提供参考,对散光型IOL的定位、度数计算以及多焦点类IOL的选择有重要意义。本文将对白内障术前角膜散光检查种类和检查设备新进展进行综述。  相似文献   

2.
3.
《Brain stimulation》2021,14(1):154-160
BackgroundTranscranial direct current stimulation (tDCS) to the dorsolateral prefrontal cortex (DLPFC) hypothetically modulates cognitive functions by facilitating or inhibiting neuronal activities chiefly in the cerebral cortex. The effect of tDCS in the deeper brain region, the basal ganglia-cortical circuit, remains unknown.ObjectiveTo investigate the interaction between γ-aminobutyric acid (GABA) concentrations and dopamine release following tDCS.MethodThis study used a randomized, placebo-controlled, double-blind, crossover design. Seventeen healthy male subjects underwent active and sham tDCS (13 min twice at an interval of 20 min) with the anode placed at the left DLPFC and the cathode at the right DLPFC, followed by examinations with [11C]-raclopride positron emission topography (PET) and GABA-magnetic resonance spectroscopy (MRS). MRS voxels were set in the left DLPFC and bilateral striata. Paired t-tests and regression analyses were performed for PET and MRS parameters.ResultsMRS data analyses showed elevations in GABA in the left striatum along with moderate reductions in the right striatum and the left DLPFC after active tDCS. PET data analyses showed that reductions in [11C]-raclopride binding potentials (increase in dopamine release) in the right striatum were inversely correlated with those in the left striatum after active tDCS. GABA reductions in the left DLPFC positively correlated with elevations in GABA in the left striatum and with increases in right striatal dopamine release and negatively correlated with increases in left striatal dopamine release.ConclusionThe present results suggest that tDCS to the DLPFC modulates dopamine-GABA functions in the basal ganglia-cortical circuit.  相似文献   
4.
BackgroundSmartphones have become increasingly more popular and complicated tasks can be performed with these devices. However, the increasing use is associated with shoulder and neck pain, as well as with psychological addiction.Research questionDo different smartphone tasks lead to changes in spinal posture and pelvic position? Is there a relationship between smartphone addiction and changes in posture?MethodsA cross-sectional study including 50 participants was performed. Test subjects completed the Smartphone Addiction Scale and the SF-36 health questionnaire. Subjects spinal posture and pelvic position during different smartphone tasks were measured through a surface topography system. The different tasks were: standing in an upright position, simulating a phone call, texting with one or two hands during standing or while walking on a treadmill. Paired T-tests and ANOVA tests were performed to evaluate differences. The Kendall rank test was used to investigate the association between clinical scores and changes in spinal posture.ResultsAll smartphone tasks lead to a significant increase in thoracic kyphosis and trunk inclination during standing and while walking. A significant increased lumbar lordosis was also found. Texting with one or two hands correlated with increased surface rotation. No associations between smartphone addiction and changes of the spinal posture were reported.SignificanceThis represents the first surface topography study that investigated the influence of different smartphone tasks on the spinal posture and pelvic position during standing and while walking. With the results of this study we demonstrated that smartphone use leads to significant changes of sagittal and frontal spine parameters. Further research should focus on the evaluation of possible detrimental effects of long-term smartphone use on the spinal posture and on the development of preventive measures.  相似文献   
5.
In many species, neurons are unevenly distributed across the retina, leading to nonuniform analysis of specific visual features at certain locations in visual space. In recent years, the mouse has emerged as a premiere model for probing visual system function, development, and disease. Thus, achieving a detailed understanding of mouse visual circuit architecture is of paramount importance. The general belief is that mice possess a relatively even topographic distribution of retinal ganglion cells (RGCs)—the output neurons of the eye. However, mouse RGCs include ∼30 subtypes; each responds best to a specific feature in the visual scene and conveys that information to central targets. Given the crucial role of RGCs and the prominence of the mouse as a model, we asked how different RGC subtypes are distributed across the retina. We targeted and filled individual fluorescently tagged RGC subtypes from across the retinal surface and evaluated the dendritic arbor extent and soma size of each cell according to its specific retinotopic position. Three prominent RGC subtypes: On-Off direction selective RGCs, object-motion-sensitive RGCs, and a specialized subclass of nonimage-forming RGCs each had marked topographic variations in their dendritic arbor sizes. Moreover, the pattern of variation was distinct for each RGC subtype. Thus, there is increasing evidence that the mouse retina encodes visual space in a region-specific manner. As a consequence, some visual features are sampled far more densely at certain retinal locations than others. These findings have implications for central visual processing, perception, and behavior in this prominent model species.  相似文献   
6.
近视眼是影响我国儿童青少年眼健康的焦点问题。远视储备是眼球发生近视前的屈光状态, 是眼轴长度与角膜及晶状体等参数之间动态匹配的结果, 对于近视眼防控意义重大。我国一直缺乏儿童眼球发育参数的指导依据以及遗传因素影响的参考资料, 尤其针对上述参数在儿童眼球正视化过程中变化规律的总结。为了促进儿童青少年近视眼防控工作的标准化, 规范人群筛查和临床治疗, 使社会各界对近视眼的预防干预和评价有据可依, 中华预防医学会公共卫生眼科分会基于我国不同地区儿童青少年的屈光不正调查数据, 针对我国学龄儿童正视眼在不同年龄段眼球远视储备、眼轴长度和角膜曲率的参考区间及相关遗传因素达成共识性意见。  相似文献   
7.
目的探讨角膜形态学和生物力学参数对近视眼人群角膜后表面高度异常的影响及其辅助诊断角膜后表面高度异常的可行性。方法病例对照研究。选取2017年12月至2018年10月在青岛眼科医院拟行角膜屈光手术的屈光不正患者144例(227只眼),其中男性90例(139只眼),女性54例(88只眼);年龄(22.8±5.6)岁。所有患者检查最佳矫正视力下的球镜和柱镜度数,并行Pentacam眼前节分析系统和Corvis ST角膜生物力学检查。根据Pentacam参数角膜后表面高度变化值(BD)进行分组,将BD<12μm定为对照组(59例,118只眼);将BD≥12μm定为高BD组(85例,109只眼),其中BD≤16μm者为可疑组(44例,53只眼),>16μm者为异常组(41例,56只眼)。选取Pentacam眼前节分析系统中BD、前表面曲率(ASK)、后表面曲率(PSK)、前表面散光(AAstig)、后表面散光(PAstig)、中央角膜厚度(CCT)、角膜直径(W-W)7个参数及Corvis ST角膜生物力学检测系统中第1次压平时间(AT1)、第1次压平长度(AL1)、第1次压平速度(AV1)、第2次压平时间(AT2)、第2次压平长度(AL2)、第2次压平速度(AV2)、最大压陷时间(HCT)、最大压陷峰距(HC-PD)、最大压陷形变幅度(HC-DA)、最大压陷曲率半径(HC-R)、形变幅度比值(DA Ratio)、综合半径、最薄点厚度/厚度变化率(ARTH)、硬度参数(SPA1)、Corvis生物力学指数(CBI)15个参数纳入研究。采用独立样本t检验、Kruskal-Wallis H检验及Bonferroni法进行组间差异性比较,利用Spearman秩相关分析探讨BD的相关影响因素,并建立多元线性回归模型寻找影响BD的主要因素。结果对照组和高BD组在年龄、球镜度数、柱镜度数差异无统计学意义(t=-3.311,-1.808,-2.359;P=0.071,0.072,0.121);Pentacam测量发现在对照组、可疑组和异常组中,ASK、PSK、PAstig、W-W组间差异有统计学意义(Z=18.492,31.547,10.773,70.167;P<0.05),AAstig、CCT组间差异无统计学意义(Z=2.204,1.108;P>0.05)。其中异常组[43.40(42.20,44.40)]较对照组[42.80(41.98,44.00)]ASK增大(t=-4.292;P<0.05),可疑组[-6.50(-6.60,-6.35)]与异常组[-6.50(-6.70,-6.33)]较对照组[-6.30(-6.50,-6.20)]PSK均增大(t=4.492,4.618;P<0.05);可疑组[0.40(0.30,0.40)]与异常组[0.40(0.30,0.40]较对照组[0.40(0.30,0.50)]PAsting均增大(t=2.796,2.515;P=0.016,0.036);可疑组[11.40(11.00,11.60)]和异常组[11.10(10.90,11.30)]较对照组[11.50(11.40,11.80)]W-W减小,同时异常组较可疑组W-W也明显减小(t=3.235,8.353,4.282;P<0.05);Corvis ST参数在3个组间差异无统计学意义(P>0.05)。将每组患者BD与Pentacam参数进行相关性分析发现,在对照组、可疑组、异常组以及所有患者中,BD与W-W呈低至中度负相关(r=-0.614,-0.304,-0.396,-0.661;P<0.05),BD与其他参数相关性较低或未见明显相关性;将患者BD与Corvis ST参数进行相关性分析发现,仅在可疑组中,BD与AV1、HCT、HC-DA间存在低度正相关(r=0.332,0.361,0.382;P<0.05),BD与Corvis ST其他参数在各组中未见明显相关性。以BD为因变量,选取Pentacam参数与Corvis ST参数建立多元线性回归分析模型:变量W-W、ASK、PSK、HC-PD、SPA1、CCT间不存在共线性(容忍度<0.100),方程检验结果F=37.221,P<0.001,调整r^2=0.504,拟合较好。结论角膜形态学参数中角膜直径、前表面曲率、后表面曲率是影响BD的主要因素,角膜生物力学参数中HC-PD和SPA1也可能对BD产生一定程度影响。角膜形态学和生物力学参数的联合评估有助于角膜后表面高度异常的鉴别诊断。  相似文献   
8.
AIM: To analyze the crosslinking (CXL) effects in pediatric keratoconus, and to identify the patients’ corneal characteristics whose pachymetry could not be adequately evaluated by Scheimpflug method after procedure. METHODS: Consecutive pediatric patients with progressive keratoconus underwent CXL were included. Best-corrected visual acuity (BCVA) and spheric equivalent (SE) were measured before and after CXL. After CXL, groups 1 and 2 were divided based on the posterior surface Pentacam quality specifications (QS): “OK” (Group 1) and “not OK” (Group 2). The mean (RmF and RmB) and minimum (RminF and RminB) radius of curvatures of the anterior and posterior corneal surfaces, and the thinnest pachymetry (Pmin) were measured preoperatively at 3, 6, 12, 24, and 36mo. Haze was annotated. RESULTS: Twenty-six patients (14 men, mean age 14±1.8y) and median Kmax of 59.9 D initially and 61.4 D preoperatively were treated. BCVA was not different before and 24mo after CXL. Group 2 statistically differed to group 1 in that SE was more myopic before and with no difference 24mo after CXL; RmF and RmB were steeper and Pmin was thinner pre-surgically. Group 2, in which pachymetric changes could not be adequately evaluated after surgery, presented with significant RmF flattening, a shift to hyperopia, and more haze after CXL. CONCLUSION: Patients whose pachymetry could not be adequately evaluated after CXL had steeper and thinner corneas before surgery. The predictive factors for impaired QS after CXL are RmF, RmB, and Pmin. In advanced keratoconus, alternative methods to analyze pachymetry and the posterior surface should be considered.  相似文献   
9.
目的:使用Sirius眼前节分析仪测量飞秒激光制瓣LASIK术后角膜后表面形态,并分析其影响因素。方法前瞻性非随机临床研究。73例(146眼)近视患者纳入本研究。其中,男35例,女38例。年龄19~36岁,平均(25.7±5.1)岁。等效球镜度(SE)-10.25~-4.50 D,平均(-6.95±1.97)D。使用Sirius眼前节分析仪测量术前及术后1个月3、5、7 mm区域角膜后表面曲率。将术后1个月角膜后表面曲率变化值(ΔK)与切削百分比(AD/CT)、切削深度(AD)、残留基质厚度(RBT)及SE进行Pearson相关分析,并进一步采用逐步回归法对ΔK的影响因素行多元线性回归分析。结果术后1个月,3、5 mm直径区域角膜后表面曲率均比术前增加,差异有统计学意义(t=3.58、3.36,P<0.01)。ΔK3 mm、ΔK5 mm、ΔK7 mm与AD/CT(r=0.845、0.833、0.753,P<0.01)和AD(r=0.725、0.727、0.603,P<0.05)呈正相关,而与SE (r=-0.762、-0.756、-0.674,P<0.05)和RBT(r=-0.784、-0.733、-0.864,P<0.01)呈负相关。多元线性回归分析发现AD/CT、RBT为ΔK3 mm的影响因素(β=2.048、-0.002,95%CI:0.489~3.607、-0.003~0,P<0.1);AD/CT 为ΔK5 mm的影响因素(β=2.005,95%CI:1.068~3.942,P<0.1);RBT、SE 为ΔK7 mm的影响因素(β=-0.003、-0.325,95%CI:-0.004~0.002、-0.786~0.428,P<0.1)。结论飞秒激光制瓣LASIK术后角膜后表面微量前凸,在保证手术效果的前提下,控制切削比,保留足量残留基质厚度,可以尽量避免术后角膜扩张、屈光回退等并发症的发生。  相似文献   
10.
BackgroundSurface topography can be used for the evaluation of spinal deformities without any radiation. However, so far this technique is limited to posterior trunk measurements due to the use of a single posterior camera.Research questionPurpose of this study was to introduce a new multi camera surface topography system and to test its reliability and validity.MethodsThe surface topograph uses a two-camera system for imaging and evaluating the subjects front and back simultaneously. Inter- and intra-rater reliability was tested on 40 human subjects by two observers. For validation human, subjects were scanned by MRI and surface-topography. For additional validation we used a phantom with an anthropomorphic body which was scanned by CT and surface topography.ResultsInter- (0.97−0.99) and intra-rater reliability (0.81−0.98) testing revealed good and excellent results in the detection of the body surface structures and measurement of areas and volumes. CT based validation revealed good correspondence between systems in the imaging and evaluation of the phantom model (0.61–10.52 %). Results on validation of human subjects revealed good to moderate results in the detection and measurements of almost all body surface structures (1.36–13.34 %). Only measurements using jugular notch as a reference showed moderate results in validity (0.62–27.5%) testing.SignificanceWe have introduced a novel and innovative surface topography system that allows for simultaneous anterior and posterior trunk measurements. The results of our reliability and validity tests are satisfactory. However, in particular around the jugular notch region further improvements in the surface topography reconstruction are needed.  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