全文获取类型
收费全文 | 3455篇 |
免费 | 549篇 |
国内免费 | 350篇 |
专业分类
电工技术 | 190篇 |
技术理论 | 2篇 |
综合类 | 384篇 |
化学工业 | 357篇 |
金属工艺 | 31篇 |
机械仪表 | 100篇 |
建筑科学 | 178篇 |
矿业工程 | 36篇 |
能源动力 | 68篇 |
轻工业 | 140篇 |
水利工程 | 88篇 |
石油天然气 | 11篇 |
武器工业 | 4篇 |
无线电 | 665篇 |
一般工业技术 | 280篇 |
冶金工业 | 37篇 |
原子能技术 | 18篇 |
自动化技术 | 1765篇 |
出版年
2024年 | 5篇 |
2023年 | 50篇 |
2022年 | 78篇 |
2021年 | 131篇 |
2020年 | 151篇 |
2019年 | 111篇 |
2018年 | 60篇 |
2017年 | 115篇 |
2016年 | 118篇 |
2015年 | 122篇 |
2014年 | 203篇 |
2013年 | 261篇 |
2012年 | 366篇 |
2011年 | 421篇 |
2010年 | 370篇 |
2009年 | 404篇 |
2008年 | 326篇 |
2007年 | 378篇 |
2006年 | 370篇 |
2005年 | 180篇 |
2004年 | 23篇 |
2003年 | 26篇 |
2002年 | 35篇 |
2001年 | 21篇 |
2000年 | 23篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1993年 | 1篇 |
排序方式: 共有4354条查询结果,搜索用时 109 毫秒
1.
Science China Technological Sciences - Iterative methods are used to simulate the in vitro feedforward neural networks in physiological experiments. Emissivity can be propagated to a minimum of ten... 相似文献
2.
面向知识库的自动问答是自然语言处理的一项重要任务,其旨在对用户提出的自然语言形式问题给出精练、准确的回复。目前由于缺少数据集,存在特征不一致等因素,导致难以使用通用的数据和方法实现领域知识库问答。因此,该文将“问题意图”视作不同领域问答可能存在的共同特征,将“问题”与三元组知识库中“关系谓词”的映射过程作为问答核心工作。为了考虑多种层次的语义并避免重要信息的损失,该文分别将“基于门控卷积的深层语义”和“基于交互注意力机制的浅层语义”通过门控感知机制相融合。在NLPCC-ICCPOL 2016 KBQA数据集上的实验表明,该文方法与现有的CDSSM和BDSSM方法相比,效能有明显提升。此外,该文通过构造天文常识知识库,将问题与关系谓词映射模型移植到特定领域,结合Bi-LSTM-CRF模型构建了天文常识自动问答系统。 相似文献
3.
目的 了解武汉市一般人群血清中全氟及多氟烷基化合物(PFASs)浓度,探索血清中PFASs浓度水平的影响因素。方法 以在武汉市某医院进行一般体检的人群为研究对象(n=67),通过超高效液相色谱-三重四级杆质谱(UPLC-TQ/MS)联用仪测定外周血清中12种PFASs浓度,采用多元线性回归分析方法分析一般人口学特征和血清中PFASs浓度的关联性。结果 武汉市一般人群血清中12种PFASs的平均浓度水平为11.60 ng/mL。全氟辛烷磺酸及其盐类(PFOS)和全氟辛酸及其盐类(PFOA)的贡献率较大,分别为45.03%和31.86%。男性人群血清中PFOS、PFOA、全氟己基磺酸(PFHxS)、全氟壬酸(PFNA)等主要化合物的浓度高于女性,其β值(95%可信区间)分别为0.708(0.313,1.104)、0.518(0.069,0.967)、0.724(0.388,1.059)和0.684(0.399,0.968)。同时,发现血清中PFOS、PFHxS、PFNA浓度和年龄呈正相关,其β值(95%可信区间)分别为0.062(0.042,0.081)、0.035(0.019,0.052)和0.030(0.016,0.045)。结论 性别和年龄对血清中PFASs浓度有影响,在进行人体PFASs暴露评估中应考虑这些因素。 相似文献
4.
Dependence is one of programming quality points can be quantified. Software Reliability Growth Model (SRGM) used to study the reliability in various difficult times available. In all cases the test execution over time, the traditional time-sensitive SRGM may not be accurate. To overcome this problem, SRGM practice rather than using the test of time. Previously, the proposed limited testing athletic ability, but with unlimited test time, test motion becomes infinite and may not make sense. Then, this method presents endless test execution work related to older models of Neural Heterogeneous Poisson Process (NHPP) of. Programming model disappointment with the proposed information to prepare Artificial Neural Network (ANN). They can imagine a lot of the load placed on a similar model to represent the previous disappointment information. Use AI model selection method can adequately represent the past and future load fitting location information. Consider using common-sense information programming disappointed indicators to show the proposed number of Testing Exertion Flow (TEF) and SRGM also successfully depicted disappointment extensive information, Machine Learning (ML) and ANN improved the accuracy of the conventional boundary estimation as compared with the discharge time and can be used to ensure that programming. 相似文献
5.
在分析现有轮廓线提取方法不足的基础上,提出基于虚拟格网的建筑物轮廓线自动提取方法。该方法利用建筑物点云生成虚拟格网并进行二值填充;采用邻域分析方法进行边界格网的标记与追踪;为了避免边界追踪错误,设计了基于方向的单边缘格网抑制方法及基于距离的连接关系调整方法以改善提取结果质量;根据格网追踪结果,从原始建筑物点云中提取真实轮廓点以保持原始建筑物轮廓形态;采用随机抽样一致性估计及最小二乘拟合方法进行轮廓线规则化处理,实现建筑物轮廓线的自动提取。实验结果表明,该方法能快速从建筑物点云中提取轮廓线,可为建筑物轮廓线的自动提取提供一种可行的解决方案。 相似文献
6.
Distortion visualization techniques for 3D coherent sets: A case study of 3D building property units
In the fields of 3D cadastre and 3D property management system, numerous building property objects are adjacent as primary property units assemble into a 3D coherent set. During visualization process of the coherent set, occlusion, obscure, mazy spatial relationships and relative location relationships among the units of the coherent set cause difficulty in observing and understanding the set and its units. Common 3D objects viewing method, such as rotation and navigation obtaining desired visualization effects through adjusting the view angle and position of the camera's field of view, provides weak interactive experience and orientation control for the coherent set because of the neighbour relationships of the 3D objects inside the set. In this paper, a novel method is proposed to solve the prior problems with two basic distortion methods based on “focus + context” theory. The coherent set is first discretized into individual objects and changed them locations according to linear or orthogonal function, while keeping their relative location and dual topological relationships. To maintain both global context awareness (topology and locations) of 3D coherent set and highlight effect of the focus 3D building property object, three evaluation indexes are adopted to assess the corresponding distortion results. A case study based on the real clustered 3D property in Shenzhen was conducted to evaluate the performance of distortion functions, the result shows that the method proposed in this article can not only expand the visual area of focused object and create a clear line of sight (LOS) to the focal object previously obscured, but also maintain verticality and proximity in some degree to facilitate understand the spatial occupation and distribution of whole coherent objects. 相似文献
7.
The relationship between location and land use patterns is one of the classic theoretical issues in urban studies. Classic models based on the monocentricity hypothesis have limitations in the interpretation of modern urban structure. China has experienced institutional transformation in recent decades, and the interaction of national government policy, market forces and the natural environment has influenced urban planning in Chinese metropolises, resulting in urban structures with special characteristics. This paper examines the distribution of location and land use intensity, and tested the Alonso model by the relationship between them in five Chinese metropolises using Point of Interest data, space syntax methodology, the grid weighted statistical method and the Geographically Weighted Regression (GWR) model. Universal patterns about the scaling relation between intensity of land use types and the centrality of location are revealed. The elasticity of land use types to location, from high to low sensitivity, is commercial, residential then industrial land in most of the five metropolises studied. The sensitivity sequence of land use studied suggests that the hypothetical model based on the classical Alonso model can explain the spatial structure of modern metropolises in China to some extent, especially for the commercial land. But the order of sensitivity of residential land and industrial land to location does not conform to the model. The spatial heterogeneity in land use intensity and centrality were explored and the factors embedded were discussed. It can be found that the relation between centrality and land use intensity conforms to power law. In most of the metropolises studied, when the scaling relation between land use intensity and centrality is super linear, the sequence of the frequency value from high to low are commercial, residential and industrial land; when the scaling relation is sublinear, the sequence of the frequency value is industrial, residential and commercial land. 相似文献
8.
Journal of Computer Science and Technology - Artistic augmentation of photographs with water droplets aims at generating aesthetic yet realistic images, and thus differs from traditional augmented... 相似文献
9.
Multimedia Tools and Applications - Depth sensor is widely used today and has great impact in object pose estimation, camera tracking, human actions, and scene reconstruction. This paper presents a... 相似文献
10.
《Ceramics International》2020,46(8):11499-11507
In this study, NiCo2O4 with different morphologies were fabricated using carriers by homogeneous coprecipitation combined with a sintering method. The phase and microstructure were characterized by XRD, SEM, EDS, TEM and BET, and the catalytic performances were investigated by NaBH4 hydrolysis experiments. These studies revealed that the deposition morphology of NiCo2O4 can be adjusted by using different kinds of carrier templates, and the supported NiCo2O4 samples presented the pine-needle-like, network-like, ball-cactus-like and dandelion-like morphologies respectively. The optimal catalytic activity, durability and stability make the network-like NiCo2O4 an appropriate catalyst for hydrogen generation of NaBH4 hydrolysis. It was found that the network-like NiCo2O4 is the most reusable and durable catalyst for ten consecutive cycles and 100% hydrogen generation conversion rate without obvious decrease among these morphologies. 相似文献