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排序方式: 共有197条查询结果,搜索用时 15 毫秒
91.
Background and purpose: Prefrontal cortex, known to be a crucial region for the function of attention, is generally thought to be largely associated with the pathogenesis of attention-deficit hyperactivity disorder (ADHD). Most previous structural imaging studies of ADHD reported abnormality of grey matter volume in prefrontal region. However, volume measure is affected by the size of the interrogated brain, which may cause the inconsistence of the volume based findings. The purpose of the current paper is to use a scale-free measure, fractal information dimension (FID), to assess the prefrontal cortical convolution complexity and asymmetry in ADHD patients. Methods: MRI scans from 12 boys with ADHD and 11 controls were carefully processed. Prefrontal cortex was outlined manually. FIDs of bilateral prefrontal cortical surface were examined in each case. Group differences of the bilateral prefrontal cortical convolution complexities and the asymmetry pattern were statistically tested. Results: We found a left-greater-than-right prefrontal cortical convolution complexity pattern in both groups. However, compared with healthy controls, the left prefrontal cortical convolution complexities of ADHD patients were significantly reduced, resulting in significant reduction of the normal left-greater-than-right cortical convolution complexity asymmetry pattern. Conclusion: This study confirms and extends the existing anatomical knowledge about the brains of people with ADHD. The cortical convolution analysis method may also be applied to quantitatively assess changes in other neuropsychiatric syndromes as well. 相似文献
92.
93.
褶合光谱法同时测定胃康胶囊中3种维生素的含量 总被引:4,自引:0,他引:4
建立胃康胶囊中3种维生素的含量测定方法。方法:用计算机辅助把台光谱分析法,不经分离同时测定多成分混合体系各组分的含量。结果:胃康胶囊中维生素B1、维生素B2和维生系B6的平均回收率和RSD分别为(99.4±0.4)%、(100±0.3)%和(100.2±0.4)%。结论:此方法准确可靠、方便易行,适合于医院制剂的常规分析。 相似文献
94.
目的 探讨基于深度卷积神经网络(DCNN)对电子密度模体(CIRS 062)插件自动定位的方法。方法 首先基于DCNN模型分割CIRS 062的吸气态肺、呼气态肺、松质骨和密质骨4个插件;之后采用摩尔邻域追踪算法处理插件边缘;最后根据几何特征定位其他4个插件。结果 基于DCNN分割结果的戴斯相似性系数均>0.85,精确度均>0.81,综合评价指标均>0.61。结论 基于DCNN方法可实现插件自动定位。 相似文献
95.
目的比较食管癌调强放射治疗各向异性分析算法(AAA)与光子笔形束卷积(PBC)算法的剂量学差异。方法选取9例食管癌患者,其中男性6例,女性3例;年龄54-68岁,平均年龄61岁。用瓦里安Eclipse 8.6治疗计划系统设计5野均分逆向调强计划,分别用AAA和PBC算法模型计算并利用COMPASS进行剂量验证。利用剂量体积直方图比较靶区、肺、心脏和脊髓照射剂量和体积。数据应用SPSS15.0进行配对t检验分析。结果大体肿瘤区(GTV)的均匀性指数(HI)、适合度指数(CI)、Dmean及计划靶区(PTV)的HI,AAA结果均优于PBC算法,差异均有统计学意义(P〈0.05)。AAA双肺各指标差值为-0.02%~-1.87%,即低估了肺2%以内的受量。PBC算法双肺各指标差值为-3.95%~1.05%,低剂量区(V5~15)低估了肺4%以内的受量,高剂量区(V20~30)则稍高估。对于脊髓,AAA和PBC算法分别高估了1.57%、4.49%。两种算法都低估了心脏的受量,但AAA相对准确。结论食管癌放射治疗中采用AAA优于PBC算法。 相似文献
96.
Sotirios Stathakis Carlos Esquivel Alonso N. Gutirrez ChengYu Shi Niko Papanikolaou 《Applied radiation and isotopes》2009,67(10):1939-1944
Purpose: In this paper, we present an alternative to the originally proposed technique for the delivery of spatially fractionated radiation therapy (GRID) using multi-leaf collimator (MLC) shaped fields. We employ the MLC to deliver various pattern GRID treatments to large solid tumors and dosimetrically characterize the GRID fields.Methods and materials: The GRID fields were created with different open to blocked area ratios and with variable separation between the openings using a MLC. GRID designs were introduced into the Pinnacle3 treatment planning system, and the dose was calculated in a water phantom. Ionization chamber and film measurements using both Kodak EDR2 and Gafchromic EBT film were performed in a SolidWater® phantom to determine the relative output of each GRID design as well as its spatial dosimetric characteristics.Results: Agreement within 5.0% was observed between the Pinnacle3 predicted dose distributions and the measurements for the majority of experiments performed. A higher magnitude of discrepancy (15%) was observed using a high photon beam energy (18 MV) and small GRID opening. Skin dose at the GRID openings was higher than the corresponding open field by a factor as high as three for both photon energies and was found to be independent of the open-to-blocked area ratio.Conclusion: In summary, we reaffirm that the MLC can be used to deliver spatially fractionated GRID therapy and show that various GRID patterns may be generated. The Pinnacle3 TPS can accurately calculate the dose of the different GRID patterns in our study to within 5% for the majority of the cases based on film and ion chamber measurements. Disadvantages of MLC-based GRID therapy are longer treatment times and higher surface doses. 相似文献
97.
目的:介绍一种基于笔射束核阵列的方法在剂量计算中的应用。方法:通过对由测量数据反解卷积获取的笔射束核阵列做进一步处理,得到拟合笔射束核。利用光通分布与笔射束核卷积得到射野剂量的分布,将拟合核和标准核计算的目标射野的剂量值与测量值进行比较。结果:与常规笔射束核相比,改进后的笔射束核应用于卷积模型中计算剂量分布,对模型的计算准确度有较大的提高。结论:改进后的笔射束核能够有效的提高卷积模型的计算精度,更为精确的预测射野的剂量分布。 相似文献
98.
白细胞图像的自动分类有助于提高临床诊疗效率,但仍需进一步改进方法以提高分类正确率。探索用卷积神经网络(CNN)进行外周血白细胞图像的自动分类识别。在深度学习框架Caffe上,以AlexNet和LeNet为网络原型构建CNN训练平台;用CellaVision DM96采集外周血涂片中的5类白细胞图像,经人工鉴定后按训练∶校验∶测试=7∶2∶1的比例,随机分配图像构建原始数据集,再通过平移、旋转及镜像构建扩充数据集;训练时采用随机梯度下降算法优化模型权值,以分类准确率>95%为目标评估训练结果及优化调整网络结构。结果发现,AlexNet的训练误差无法收敛,陷入局部极小,LeNet则达到预期目标。随后对LeNet网络进行删减优化,获得一轻量高效的新结构--CCNet,其在模型大小、训练用时和分类用时上分别仅为LeNet的1/1000、1/3和1/30。两者对979张5类细胞图像的最佳分类准确率分别达到99.69%和99.18%,高于目前同类研究报道。结果表明,CNN可用于5类白细胞图像的“端对端”分类识别,特别是CCNet模型兼具准确与效率优势。 相似文献
99.
《Pharmaceutical development and technology》2013,18(6):708-716
AbstractThe objective of this study was to design oral controlled release (CR) matrix tablets of Milnacipran using hydroxypropyl methylcellulose (HPMC) as the retardant polymer and to study the effect of various formulation factors such as polymer proportion, polymer viscosity, compression force and also the pH of dissolution medium on the in-vitro release of drug. Two viscosity grade of HPMC (15?K and 100?K) were used in the proportion of 50, 100, 150 and 200?mg per CR tablet. In-vitro release rate was characterized using various model dependent approaches and model independent dissolution parameters [T50% and T80% dissolution time, mean dissolution time (MDT), mean residence time (MRT), dissolution efficiency (DE)]. The statistical analysis was performed on all the model independent approaches using student t test and ANOVA. Results were found that as polymer concentration (50?mg to 200?mg) and viscosity (15?K to 100?K) increases, the MDT, MRT, T50% and T80% extended significantly. Drug release rate was found to be significantly different at different hardness. In-vivo human plasma concentration--time profile was predicted from in-vitro release data using convolution method. Predicted human pharmacokinetic parameters shows that the design CR formulation has capability to sustained the plasma drug level of milnacipran. 相似文献
100.
二氢卟吩金属络合物的褶合光谱法鉴别分析 总被引:2,自引:0,他引:2
目的:对结构相似的5种二氢卟吩金属络合物进行定性鉴别。方法:采用褶合变换技术和计算机信息处理技术进行鉴别分析。结果:通过两两匹配,使用三维褶合光谱差谱,对5种二氢卟吩金属络合物进行鉴别分析,得出10个非同一性认定鉴别结论。结论:本法专属性强,操作简便,在鉴别化合物的结构方面值得推广。 相似文献