全文获取类型
收费全文 | 4332篇 |
免费 | 689篇 |
国内免费 | 472篇 |
专业分类
电工技术 | 454篇 |
技术理论 | 1篇 |
综合类 | 702篇 |
化学工业 | 386篇 |
金属工艺 | 67篇 |
机械仪表 | 382篇 |
建筑科学 | 306篇 |
矿业工程 | 86篇 |
能源动力 | 94篇 |
轻工业 | 232篇 |
水利工程 | 161篇 |
石油天然气 | 191篇 |
武器工业 | 72篇 |
无线电 | 581篇 |
一般工业技术 | 323篇 |
冶金工业 | 53篇 |
原子能技术 | 38篇 |
自动化技术 | 1364篇 |
出版年
2024年 | 9篇 |
2023年 | 54篇 |
2022年 | 104篇 |
2021年 | 129篇 |
2020年 | 146篇 |
2019年 | 148篇 |
2018年 | 115篇 |
2017年 | 152篇 |
2016年 | 178篇 |
2015年 | 195篇 |
2014年 | 280篇 |
2013年 | 337篇 |
2012年 | 382篇 |
2011年 | 364篇 |
2010年 | 266篇 |
2009年 | 327篇 |
2008年 | 284篇 |
2007年 | 313篇 |
2006年 | 279篇 |
2005年 | 201篇 |
2004年 | 175篇 |
2003年 | 164篇 |
2002年 | 124篇 |
2001年 | 124篇 |
2000年 | 96篇 |
1999年 | 77篇 |
1998年 | 67篇 |
1997年 | 57篇 |
1996年 | 49篇 |
1995年 | 54篇 |
1994年 | 37篇 |
1993年 | 30篇 |
1992年 | 33篇 |
1991年 | 24篇 |
1990年 | 26篇 |
1989年 | 26篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1968年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有5493条查询结果,搜索用时 15 毫秒
1.
Laura Cuy-Chaparro Michel David Bohrquez Gabriela Arvalo-Pinzn Jeimmy Johana Castaeda-Ramírez Carlos Fernando Surez Laura Pabn Diego Ordez Gina Marcela Gallego-Lpez Carlos Esteban Surez Darwin Andrs Moreno-Prez Manuel Alfonso Patarroyo 《International journal of molecular sciences》2021,22(2)
Apical membrane antigen 1 is a microneme protein which plays an indispensable role during Apicomplexa parasite invasion. The detailed mechanism of AMA-1 molecular interaction with its receptor on bovine erythrocytes has not been completely defined in Babesia bovis. This study was focused on identifying the minimum B. bovis AMA-1-derived regions governing specific and high-affinity binding to its target cells. Different approaches were used for detecting ama-1 locus genetic variability and natural selection signatures. The binding properties of twelve highly conserved 20-residue-long peptides were evaluated using a sensitive and specific binding assay based on radio-iodination. B. bovis AMA-1 ectodomain structure was modelled and refined using molecular modelling software. NetMHCIIpan software was used for calculating B- and T-cell epitopes. The B. bovis ama-1 gene had regions under functional constraint, having the highest negative selective pressure intensity in the Domain I encoding region. Interestingly, B. bovis AMA-1-DI (100YMQKFDIPRNHGSGIYVDLG119 and 120GYESVGSKSYRMPVGKCPVV139) and DII (302CPMHPVRDAIFGKWSGGSCV321)-derived peptides had high specificity interaction with erythrocytes and bound to a chymotrypsin and neuraminidase-treatment sensitive receptor. DI-derived peptides appear to be exposed on the protein’s surface and contain predicted B- and T-cell epitopes. These findings provide data (for the first-time) concerning B. bovis AMA-1 functional subunits which are important for establishing receptor-ligand interactions which could be used in synthetic vaccine development. 相似文献
2.
Higher transmission rate is one of the technological features of prominently used wireless communication namely Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO–OFDM). One among an effective solution for channel estimation in wireless communication system, specifically in different environments is Deep Learning (DL) method. This research greatly utilizes channel estimator on the basis of Convolutional Neural Network Auto Encoder (CNNAE) classifier for MIMO-OFDM systems. A CNNAE classifier is one among Deep Learning (DL) algorithm, in which video signal is fed as input by allotting significant learnable weights and biases in various aspects/objects for video signal and capable of differentiating from one another. Improved performances are achieved by using CNNAE based channel estimation, in which extension is done for channel selection as well as achieve enhanced performances numerically, when compared with conventional estimators in quite a lot of scenarios. Considering reduction in number of parameters involved and re-usability of weights, CNNAE based channel estimation is quite suitable and properly fits to the video signal. CNNAE classifier weights updation are done with minimized Signal to Noise Ratio (SNR), Bit Error Rate (BER) and Mean Square Error (MSE). 相似文献
3.
4.
Nasser Samadzadehaghdam Bahador Makkiabadi Sadegh Masjoodi Mohammad Mohammadi Fahimeh Mohagheghian 《International journal of imaging systems and technology》2019,29(4):686-700
Brain source imaging based on EEG aims to reconstruct the neural activities producing the scalp potentials. This includes solving the forward and inverse problems. The aim of the inverse problem is to estimate the activity of the brain sources based on the measured data and leadfield matrix computed in the forward step. Spatial filtering, also known as beamforming, is an inverse method that reconstructs the time course of the source at a particular location by weighting and linearly combining the sensor data. In this paper, we considered a temporal assumption related to the time course of the source, namely sparsity, in the Linearly Constrained Minimum Variance (LCMV) beamformer. This assumption sounds reasonable since not all brain sources are active all the time such as epileptic spikes and also some experimental protocols such as electrical stimulations of a peripheral nerve can be sparse in time. Developing the sparse beamformer is done by incorporating L1-norm regularization of the beamformer output in the relevant cost function while obtaining the filter weights. We called this new beamformer SParse LCMV (SP-LCMV). We compared the performance of the SP-LCMV with that of LCMV for both superficial and deep sources with different amplitudes using synthetic EEG signals. Also, we compared them in localization and reconstruction of sources underlying electric median nerve stimulation. Results show that the proposed sparse beamformer can enhance reconstruction of sparse sources especially in the case of sources with high amplitude spikes. 相似文献
5.
针对SIFT描述子实时性差和传统二进制描述子对尺度、旋转和视角变化鲁棒性差的问题,本文通过优化采样模式和添加灰度差分不变量比较测试进行改进,提出了一种鲁棒性更高的二进制描述子。首先,设计了一种尺度关联、编号标记的采样模式;然后,旋转采样模式中各采样点到特定位置,确保描述子尺度、旋转不变性;接着,分析了采样点点对模式对描述子的影响,选择使用机器学习训练后的128对采样点对;最后,选择灰度值比较测试及梯度绝对值和比较测试构建二进制描述子。实验中采用DoG检测图像关键点,结果表明:本文提出的描述子在描述子构建和描述子匹配上比SIFT描述子分别快84%和67%;在有视角变化的图像匹配上,准确率比传统的二进制描述子高3%~5%,召回率平均要高30%以上。本文提出的特征点描述方法适用于时间要求高的图像匹配领域。 相似文献
6.
本文以神达朝凯煤矿正在开采的台阶为工程背景,针对该矿在台阶爆破过程中存在着大块率高、根底多的现象,通过改变装药结构的方式对爆破参数进行优化。实践证明,优化后大块率和根底问题的治理效果明显。 相似文献
7.
8.
Anne Hofmann Stefanie Wienkoop Snke Harder Fabian Bartlog Sabine Lüthje 《International journal of molecular sciences》2020,21(22)
Flooding induces low-oxygen environments (hypoxia or anoxia) that lead to energy disruption and an imbalance of reactive oxygen species (ROS) production and scavenging enzymes in plants. The influence of hypoxia on roots of hydroponically grown maize (Zea mays L.) plants was investigated. Gene expression (RNA Seq and RT-qPCR) and proteome (LC–MS/MS and 2D-PAGE) analyses were used to determine the alterations in soluble and membrane-bound class III peroxidases under hypoxia. Gel-free peroxidase analyses of plasma membrane-bound proteins showed an increased abundance of ZmPrx03, ZmPrx24, ZmPrx81, and ZmPr85 in stressed samples. Furthermore, RT-qPCR analyses of the corresponding peroxidase genes revealed an increased expression. These peroxidases could be separated with 2D-PAGE and identified by mass spectrometry. An increased abundance of ZmPrx03 and ZmPrx85 was determined. Further peroxidases were identified in detergent-insoluble membranes. Co-regulation with a respiratory burst oxidase homolog (Rboh) and key enzymes of the phenylpropanoid pathway indicates a function of the peroxidases in membrane protection, aerenchyma formation, and cell wall remodeling under hypoxia. This hypothesis was supported by the following: (i) an elevated level of hydrogen peroxide and aerenchyma formation; (ii) an increased guaiacol peroxidase activity in membrane fractions of stressed samples, whereas a decrease was observed in soluble fractions; and (iii) alterations in lignified cells, cellulose, and suberin in root cross-sections. 相似文献
9.
10.
针对超级计算机系统中网络引导时间开销大的问题,提出网络引导分布算法是影响网络引导性能的主要因素之一,是优化网络引导性能的主要方向的观点。首先,分析了影响大规模网络引导性能的主要因素;其次,结合一种典型超级计算机系统,分析了超节点循环分布算法(SCDA)和插件循环分布算法(BCDA)的网络引导数据流拓扑结构;最后,量化分析了这两种算法对各个网络路径段的压力和可获得的网络性能,发现BCDA性能是SCDA性能的1~20倍。通过理论分析和模型推导发现,在计算节点和引导服务器之间使用更细粒度的映射算法可以在引导部分资源时使用尽量多的引导服务器,减少对局部网络资源的过早竞争,提升网络引导性能。 相似文献