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1.
介绍了电机故障诊断技术平台的组成,分析了电机常见故障下电信号的特征。利用宜昌和景洪工厂两台电机进行了实际对比测试,宜昌工厂电机定子电流特征频率在49.2Hz时表现出峰值-36.08dB,在50.8Hz时表现峰值则为-37.23dB,表明电机存在转子断条故障;景洪工厂电机在转子特征频率为113.51Hz时,出现峰值-58.47dB,表明电机存在静态偏心故障。经电机现场抽芯检查,验证了电机故障快速诊断平台给出的电机健康状态评估结果,证实了基于电信号特征分析的电机故障诊断技术的准确性。  相似文献   
2.
《Ceramics International》2022,48(9):12209-12216
We report the structural, magnetic, electrical and broadband microwave absorption in La0.7Na0.3MnO3 sample synthesized by microwave (MW) irradiation (Na0.3LMO_MW) and compare them to the sample synthesized by solid-state (SS) reaction method (Na0.3LMO_SS). Single phase Na0.3LMO_MW was synthesized at 800 °C in 30 min, whereas, Na0.3LMO_SS sample was obtained by sintering at 1200 °C for 48 h. Although both these samples show ferromagnetic transition at TC ~324.8 K, the MW-synthesized sample shows distinct physical properties: broad ferromagnetic transition, smaller saturation magnetization, a large difference between the magnetic ordering and metal-insulator transition temperatures, a large high-field magnetoresistance, a table top-like magnetocaloric effect, and a large low-field microwave absorption compared to the solid state synthesized sample. These differences are suggested to arise from magnetic heterogeneity induced by smaller grain size and surface spin disorder in the MW synthesized La0.7Na0.3MnO3.  相似文献   
3.
Hydrogen is among a few promising energy carriers of the future mainly due to its zero-emission combustion nature. It also plays an important role in the transition from fossil fuel to renewable. Hydrogen technology is relatively immature and serious knowledge gaps do exist in its production, transport, storage, and utilization. Although the economical generation of hydrogen to the scale required for such transition is still the biggest technical and environmental challenge, unlocking the large-scale but safe storage is similarly important. It is difficult to store hydrogen in solid and liquid states and storing it in the gaseous phase requires a huge volume which is just available in subsurface porous media. Sandstone is the most abundant and favourable medium for such storage as carbonate rock might not be suitable due to potential geochemical reactions.It is well established in the literature that interaction of the host rock-fluid and injected gas plays a crucial role in fluid flow, residual trapping, withdrawal, and more generally storing capacity. Such data for the hydrogen system is extremely rare and are generally limited to contact angle measurements, while being not representative of the reality of rock-brine-hydrogen interaction(s). Therefore, we have conducted, for the first time, a series of core flooding experiments using Nuclear Magnetic Resonance (NMR) to monitor hydrogen (H2) and Nitrogen (N2) gas saturations during the drainage and imbibition stages under pressure and temperature that represent shallow reservoirs. To avoid any geochemical reaction during the test, we selected a clean sandstone core plug of 99.8% quartz (Fontainebleau with a gas porosity of 9.7% and a permeability of 190 mD).Results show significantly low initial and residual H2 saturations in comparison with N2, regardless of whether the injection flow rate or capillary number were the same or not. For instance, when the same injection flow rate was used, H2 saturation during primary drainage was 4% and it was <2% after imbibition. On other hand, N2 saturation during the primary drainage was 26% and it was 17% after imbibition. However, when the same capillary number of H2 was utilised for the N2 experiment, the N2 saturation values were ~15% for initial gas saturation and 8% for residual gas saturation. Our results promisingly support the idea of hydrogen underground storage; however, we should emphasise that more sandstone rocks of different clay mineralogy should be investigated before reaching a conclusive outcome.  相似文献   
4.
超稳光纤链路这个概念包含超稳频率光源和超稳频率传递的光纤链路。从当前看,如何利用已有庞大的公用电信网、专用网的光纤和光网络的资源,选择一个通用的光纤通路改造成超稳光纤链路来实现频率传递,取代基于卫星的频率传递,提高传输的频率精度,这是一个巨大的系统工程。本文对超稳频率光源和超稳频率传递的光纤链路的关键技术进行研究和讨论。  相似文献   
5.
This study investigated the effect of 5 freeze–thaw cycles (freezing at −18°C for 12 h and then thawing at 4°C for approximately 12 h) on the meat quality, proximate composition, water distribution and microstructure of bovine rumen smooth muscle (BSM). As the number of freeze–thaw cycles increased, BSM pH, shear force, water content and protein content decreased by 3.06%, 35.50%, 14.49% and 21.11%, respectively, whereas BSM thawing loss, cooking loss, pressing loss, total aerobic count (TAC), ash content and fat content increased by 108.12%, 47.75%, 78.33%, 90.99%, 105% and 35.20%, respectively. The freeze–thaw cycles resulted in greater protein and lipid oxidation, as evidenced by a 36.46% reduction in the sulfhydryl content and a 209.06% and 338.46% increase in the carbonyl and malondialdehyde contents, respectively. Ice crystal formation disrupted the structural integrity of the muscle tissue. Low-field nuclear magnetic resonance results showed that the freeze–thaw cycles prolonged the relaxation times (T2b, T21 and T22), indicating that immobile water shifted to free water, and consequently, free water mobility increased. After 3 freeze–thaw cycles, the decline in shear force slowed, the increase in thawing loss became accelerated, and the TAC approached the domain value (6 log colony-forming units/g). Therefore, the number of freeze–thaw cycles of smooth muscle during transport, storage and distribution should be controlled to 3 or fewer. The current results provide a theoretical basis and data support for the further utilisation and culinary processing of smooth muscle.  相似文献   
6.
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   
7.
高效率地使用工程车辆是工程项目管理中节约成本的有效方法,无人监管环境下工程车辆的工况识别,是实现工程车辆高效率使用的有效手段。目前以GPS等技术为核心的车辆智能管理系统未对工程车辆进行工况识别,提出一种基于GRU循环神经网络的工程车辆工况识别方法,通过对工程车辆在不同工况下产生的音频信号进行分析,从中提取Mel倒谱系数作为主要特征,构建GRU循环神经网络模型进行训练和识别。实验结果表明,该方法可以实现对工程车辆工况的有效识别。  相似文献   
8.
This work investigates the influence of niobium pentoxide (Nb2O5) as dopant, on the structural, magnetic, and dielectric properties of NiZnCo ferrites. The results showed that Nb2O5 was an effective dopant, and the Nb5+ ions entered the B site to replace Fe3+ ions, which altered the electromagnetic properties of the NiZnCo ferrite. In particular, the coercivity (Hc) was 20~24 Oe, and the magnetic quality factor (Q), was more than 200 at x = 0 and x = 0.1 wt%, which is 4~5 times higher than that of NiZn and NiCuZn ferrites. Excellent electromagnetic properties were obtained for 0.1 wt% Nb2O5-doped NiZnCo ferrite, i.e., Ms = 88.3 emu/g, Hc =20.4 Oe, ρ = 2.4 × 105 Ω m and Q = 202 @20 MHz. These excellent electromagnetic properties of Nb2O5-doped NiZnCo ferrites could be potentially applied to resonators and capacitors at high frequency.  相似文献   
9.
传统通信模拟系统设计较为复杂,导致模拟过程消耗能量较大,不能准确模拟稳频通信质量。因此,提出基于Matlab的量子激光雷达稳频通信模拟系统。由于振荡器是雷达形成初始信号源的基础,通过分析振荡电路与相位噪声,获得相位噪声函数与通信频率存在的关系;为确保通信过程的稳定,将准确性与稳定性作为信号质量的评价指标,并采用锁频环稳频技术计算频率偏移程度,根据PID控制算法控制频率,量子激光雷达稳频通信;利用Matlab确定激光器、探测器等硬件组成结构,通过时序与数字阵列的设置完成模拟系统设计。仿真结果表明所提系统结构简便、性能稳定,能够真实模拟出稳频通信的信号质量。  相似文献   
10.
This paper introduces the design of a hardware efficient reconfigurable pseudorandom number generator (PRNG) using two different feedback controllers based four-dimensional (4D) hyperchaotic systems i.e. Hyperchaotic-1 and -2 to provide confidentiality for digital images. The parameter's value of these two hyperchaotic systems is set to be a specific value to get the benefits i.e. all the multiplications (except a few multiplications) are performed using hardwired shifting operations rather than the binary multiplications, which doesn't utilize any hardware resource. The ordinary differential equations (ODEs) of these two systems have been exploited to build a generic architecture that fits in a single architecture. The proposed architecture provides an opportunity to switch between two different 4D hyperchaotic systems depending on the required behavior. To ensure the security strength, that can be also used in the encryption process in which encrypt the input data up to two times successively, each time using a different PRNG configuration. The proposed reconfigurable PRNG has been designed using Verilog HDL, synthesized on the Xilinx tool using the Virtex-5 (XC5VLX50T) and Zynq (XC7Z045) FPGA, its analysis has been done using Matlab tool. It has been found that the proposed architecture of PRNG has the best hardware performance and good statistical properties as it passes all fifteen NIST statistical benchmark tests while it can operate at 79.101-MHz or 1898.424-Mbps and utilize only 0.036 %, 0.23 %, and 1.77 % from the Zynq (XC7Z045) FPGA's slice registers, slice LUTs, and DSP blocks respectively. Utilizing these PRNGs, we design two 16 × 16 substitution boxes (S-boxes). The proposed S-boxes fulfill the following criteria: Bijective, Balanced, Non-linearity, Dynamic Distance, Strict Avalanche Criterion (SAC) and BIC non-linearity criterion. To demonstrate these PRNGs and S-boxes, a new three different scheme of image encryption algorithms have been developed: a) Encryption using S-box-1, b) Encryption using S-box-2 and, c) Two times encryption using S-box-1 and S-box-2. To demonstrate that the proposed cryptosystem is highly secure, we perform the security analysis (in terms of the correlation coefficient, key space, NPCR, UACI, information entropy and image encryption quantitatively in terms of (MSE, PSNR and SSIM)).  相似文献   
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