全文获取类型
收费全文 | 6254篇 |
免费 | 756篇 |
国内免费 | 564篇 |
专业分类
电工技术 | 549篇 |
综合类 | 829篇 |
化学工业 | 469篇 |
金属工艺 | 105篇 |
机械仪表 | 348篇 |
建筑科学 | 440篇 |
矿业工程 | 152篇 |
能源动力 | 209篇 |
轻工业 | 366篇 |
水利工程 | 213篇 |
石油天然气 | 242篇 |
武器工业 | 71篇 |
无线电 | 663篇 |
一般工业技术 | 648篇 |
冶金工业 | 179篇 |
原子能技术 | 121篇 |
自动化技术 | 1970篇 |
出版年
2024年 | 12篇 |
2023年 | 92篇 |
2022年 | 102篇 |
2021年 | 130篇 |
2020年 | 195篇 |
2019年 | 184篇 |
2018年 | 169篇 |
2017年 | 196篇 |
2016年 | 237篇 |
2015年 | 246篇 |
2014年 | 337篇 |
2013年 | 388篇 |
2012年 | 496篇 |
2011年 | 525篇 |
2010年 | 419篇 |
2009年 | 378篇 |
2008年 | 401篇 |
2007年 | 477篇 |
2006年 | 413篇 |
2005年 | 369篇 |
2004年 | 334篇 |
2003年 | 287篇 |
2002年 | 211篇 |
2001年 | 176篇 |
2000年 | 159篇 |
1999年 | 119篇 |
1998年 | 104篇 |
1997年 | 88篇 |
1996年 | 56篇 |
1995年 | 68篇 |
1994年 | 51篇 |
1993年 | 23篇 |
1992年 | 32篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1964年 | 2篇 |
1959年 | 3篇 |
1958年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有7574条查询结果,搜索用时 15 毫秒
1.
彭家寅 《计算机工程与应用》2020,56(12):93-97
目的是利用高维量子纠缠态为量子信道,讨论未知单粒子态的受控隐形传输问题。以三维量子纠缠态为信道,提出一个二维任意单粒子态的受控隐形传输协议。提出了以任意[d]-维量子纠缠态为量子信道,[t]-维任意单粒子态的隐形传输协议[(t相似文献
2.
Mohammad Hossein
Abbasi Laura Iapichino Sajad Naderi Lordejani Wil Schilders Nathan van de Wouw 《International journal for numerical methods in engineering》2020,121(23):5178-5199
To circumvent restrictions of conventional drilling methods, such as slow control actions and inability to drill depleted reservoirs, a drilling method called managed pressure drilling (MPD) has been developed. In MPD, single-phase flow processes can be modeled as a feedback interconnection of a high-order linear system and a low-order nonlinear system. These nonlinearities appear locally both inside and at the boundaries of the computational domain. To obtain a fast simulation platform for real-time purposes (eg, online model-based controller implementation), model order reduction is required for MPD. However, the local nonlinearities render applying model order reduction techniques challenging. In this study, a new approach is proposed to deal with such nonlinearities within the reduced basis (RB) context and it is successfully tested on a model for MPD. Contrary to the classical RB technique, the proposed approach not only does not generate nonphysical spikes at the locations of these local nonlinearities but also yields high speedup factors. The obtained reduced-order model can be used for efficient online simulation and controller design for drilling systems with MPD. 相似文献
3.
为了鉴别不同品牌矿泉水标注水源地信息真伪,对11种不同品牌饮用水的氢氧稳定同位素(δD和δ18 O)进行测定。结果表明,水平衡法(GasBench-IRMS)和高温转化法(TC/EA-IRMS)的测定结果一致性较好,两种方法测定6种不同饮用水的δD和δ18 O的平均差异分别为(0.6±1.59)‰和(0.02±0.13)‰。水平衡法需要较长的制备和测定时间,但δD和δ18 O的测定精度明显优于高温转化法。11种饮用水δD和δ18 O变化范围较大,其δD和δ18 O受不同品牌饮用水的水源地降水影响形成明显的地域性。虽然无法区分矿泉水是否由其他类别饮用水伪造,但δD和δ18 O可以为特定区域(如高海拔与沿海地区)以及产地相近的矿泉水水源地鉴别提供依据。 相似文献
4.
In this paper, a robust controller for a Six Degrees of Freedom (6 DOF) coaxial octorotor helicopter control is proposed in presence of actuator faults. Radial Base Function Neural Network (RBFNN), Fuzzy Logic Control approach (FLC) and Sliding Mode Control (SMC) technique are used to design a controller, named Fault Tolerant Control (FTC), for each subsystem of the octorotor helicopter. The proposed FTC scheme allows avoiding difficult modeling, attenuating the chattering effect of the SMC, reducing the rules number of the fuzzy controller, and guaranteeing the stability and the robustness of the system. The simulation results show that the proposed FTC can greatly alleviate the chattering effect, good tracking in presence of actuator faults. 相似文献
5.
Alpesh Kumar B. V. Rathish Kumar 《International Journal for Computational Methods in Engineering Science and Mechanics》2019,20(5):451-459
AbstractIn this article, we presented a method for option pricing problem under regime-switching jump-diffusion models. We have proposed a numerical method for solving a partial integro-differential equation (PIDE) for pricing European option and for solving linear complementarity problem (LCP), to evaluate the price of American options. We use implicit explicit method for time semi discretization, followed by radial basis function based finite difference (RBF-FD) method for spatial discretization to solve PIDE. The proposed method is further extended to solve the LCP by coupling it with operator splitting method. Numerical simulation is done for European and American option to demonstrate efficiency and accuracy of the proposed method. 相似文献
6.
7.
The objective of this study was to extend a stable isotope-based assessment of AA absorption from rumen-degradable protein (RDP) sources to include determination of essential AA (EAA) availability from microbial protein (MCP). To demonstrate the technique, a study using a 2 × 2 factorial arrangement of treatments applied in a repeated 4 × 4 Latin square design was undertaken. Factors were high and low rumen-degradable protein and high and low starch. Twelve lactating cows were blocked into 3 groups according to days in milk and randomly assigned to the 4 treatment sequences. Each period was 14 d in length with 10 d of adaption followed by 4 d of ruminal infusions of 15N-labeled ammonium sulfate. On the last day of each period, a 13C-labeled AA mixture was infused into the jugular vein over a 6-h period to assess total AA entry. Rumen, blood, urine, and milk samples were collected during the infusions. Ruminal bacteria and blood samples were assessed for AA enrichment. Total plasma AA absorption rates were derived for 6 EAA from plasma 13C AA enrichment. Absorption of 6 EAA from MCP was calculated from total AA absorption based on 15N enrichment in blood and rumen bacteria. Essential AA absorption rates from total protein, MCP, and rumen-undegradable protein were derived with standard errors of the mean of 6, 14, and 14%, respectively. An average of 45% of absorbed EAA were from MCP, which varied among 6 EAA and was interactively affected by starch and RDP in diets. Microbial AA availability measured by isotope dilution method increased with the high RDP diets and was unaffected by starch level, except for Met, which decreased with high starch. Microbial protein outflow, estimated from urinary purine derivatives, increased with RDP and was not significantly affected by starch. This was consistent with measurements from the isotope dilution method. Total AA absorption rates measured from isotope dilution were similar to estimates from CNCPS (v. 6.55), but a lower proportion of absorbed AA was derived from MCP for the former method. Compared with the isotope and CNCPS estimates, the Fleming model underestimated microbial EAA and total EAA availability. An average of 58% of the absorbed EAA was converted into milk, which varied among individual AA and was interactively affected by starch and RDP in diets. The isotope dilution approach is advantageous because it provides estimates of EAA availability for individual EAA from rumen-undegradable protein and MCP directly with fewer errors of measurement than can be achieved with intestinal disappearance methods. 相似文献
8.
9.
针对跨数据中心的资源调度问题,提出了一种基于组合双向拍卖(PCDA)的资源调度方案。首先,将云资源拍卖分为三个部分:云用户代理报价、云资源提供商要价、拍卖代理组织拍卖;其次,在定义用户的优先级及任务紧迫度的基础上,在拍卖过程中估算每一个工作发生的服务等级协议(SLA)违规并以此计算云提供商的收益,同时每轮竞拍允许成交多项交易;最终达到根据用户等级合理分配云资源调度的效果。仿真实验结果表明该算法保证了竞拍成功率,与传统一次拍卖成交一项的组合双向拍卖方案相比,PCDA在竞拍时间段产生的能耗降低了35.00%,拍卖云提供商的利润提高了约38.84%。 相似文献
10.
Mariusz Ciesielski Bohdan Mochnacki 《International Journal of Cast Metals Research》2019,32(4):213-220
The thermal processes proceeding in the casting-mould system are analysed. Solidification process can be described in the different ways. One of them consists in the application of the Fourier–Kirchhoff equation in which the source function controlling the phase change is introduced. In this paper, two approaches to the modelling of pure metals solidification, i.e. the solidification proceeding at the constant temperature and in the artificially introduced interval of temperature are considered. Numerical model used at the stage of computations is constructed using the Control Volume Method in which the principle of conservation of energy (taking also into account the release of latent heat of solidification) is applied to each control volume ensuring the correctness of the model. The use of Voronoi/Thiessen tessellation to the discretization of the casting-mould system can accurately reproduce the shape of each sub-domain. In the final part of the paper, the examples of computations are shown. 相似文献