首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   245篇
  免费   4篇
电工技术   1篇
化学工业   61篇
机械仪表   2篇
建筑科学   14篇
能源动力   21篇
轻工业   25篇
水利工程   2篇
无线电   16篇
一般工业技术   60篇
冶金工业   10篇
原子能技术   1篇
自动化技术   36篇
  2024年   10篇
  2023年   4篇
  2022年   2篇
  2021年   15篇
  2020年   9篇
  2019年   18篇
  2018年   12篇
  2017年   12篇
  2016年   23篇
  2015年   9篇
  2014年   9篇
  2013年   19篇
  2012年   13篇
  2011年   21篇
  2010年   10篇
  2009年   13篇
  2008年   12篇
  2007年   4篇
  2006年   10篇
  2005年   7篇
  2004年   1篇
  2003年   4篇
  2002年   1篇
  2000年   2篇
  1999年   1篇
  1998年   2篇
  1996年   1篇
  1992年   1篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
排序方式: 共有249条查询结果,搜索用时 15 毫秒
81.
    
Poly(epichlorohydrin‐g‐styrene) and poly (epichlorohydrin‐g‐methyl methacrylate) graft copolymers were synthesized by a combination of cationic and photoinitiated free‐radical polymerization. For this purpose, first, epichlorohydrin was polymerized with tetrafluoroboric acid (HBF4) via a cationic ring‐opening mechanism, and, then, polyepichlorohydrin (PECH) was reacted ethyl‐hydroxymethyl dithio sodium carbamate to obtain a macrophotoinitiator. PECH, possessing photolabile thiuram disulfide groups, was used in the photoinduced polymerization of styrene or methyl methacrylate to yield the graft copolymers. The graft copolymers were characterized by 1H‐NMR spectroscopy, differential scanning calorimetry, and gel permeation chromatography. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
82.
    
New elemental sulfur‐based polymeric materials called poly(sulfur‐random‐divinylbenzene) [poly(S‐r‐DVB)] were synthesized by ring opening polymerization via inverse vulcanization technique in the presence of a mixture of o‐, m‐, and p‐diviniylbenzene (DVB) as a cross‐linker. A clear yellow/orange colored liquid was obtained from the elemental sulfur melted at 160 °C and then by adding various amounts of DVB to this liquid directly via a syringe at 200 °C viscous reddish brown polymeric materials were obtained. The copolymers are soluble in common solvents like tetrahydrofuran, dichloromethane, and chloroform, and they can be coated on any surface as a thin film by a spray coating technique. The characterization of the materials was performed by using nuclear magnetic resonance, fourier transform infrared, and Raman spectroscopies. The morphological properties were monitored via scanning electron microscope technique. Thermal analysis showed that an increase in the amount of DVB in the copolymers resulted in an increase in the thermal decomposition temperature. On the other hand, poly(S‐r‐DVB) copolymers exhibited good percent transmittance as 50% T between 1500 and 13,000 nm in electromagnetic radiation spectrum, which makes them good candidates to be amenable use in military and surveillance cameras. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43655.  相似文献   
83.
84.
    
The most significant complication of end-stage kidney disease (ESKD) is cardiovascular disease, mainly coronary artery disease (CAD). Although the effective treatment of CAD is an important prognostic factor, whether percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) is better for treating CAD in this group of patients is still controversial. We searched Pubmed/Medline, Web of Science, Embase, the Cochrane Central Register of Controlled Trials articles that compared the outcomes of CABG versus PCI in patients with ESKD requiring dialysis. A total of 10 observational studies with 39,666 patients were included. Our analysis showed that when compared to PCI, CABG had lower risk of need for repeat revascularization (relative risk [RR] = 2.25, 95% confidence interval [CI] 2.1–2.42, p < 0.00001) and cardiovascular death (RR = 1.19, 95% CI 1.14–1.23, p < 0.00001) and higher risk for short-term mortality (RR = 0.43, 95% CI 0.38–0.48, p < 0.00001). There was no statistically significant difference between the PCI and CABG groups in the risk for late mortality (RR = 1.05, 95% CI 0.97–1.14, p = 0.25), myocardial infarction (RR = 1.05, 95% CI 0.46–2.36, p = 0.91) or stroke (RR = 1.02, 95% CI 0.64–1.61, p = 0.95). This meta-analysis showed that in ESKD patients requiring dialysis, CABG was superior to PCI in regard to cardiovascular death and need for repeat revascularization and inferior to PCI in regard to short term mortality. However, this meta-analysis has limitations and needs confirmation with large randomized controlled trials.  相似文献   
85.
    
Monitoring fiber reinforced polymer composites (FRPC) during their production and operation is becoming crucial to track the performance of the final parts and optimize the overall life cycle. The challenges associated with integrating multifunctional sensors with the required aspect ratio, manufacturing scalability, robustness, and performance within FRPC parts remain, however, unresolved. Here, a novel class of electronic polymer fiber sensors that can be seamlessly integrated within FRPC, and can sense and decouple cure time, temperature, and strain during and postprocessing is reported. It is shown that the particular fiber geometry induces a minimal impact on the final FRPC microstructure. Integrating both capacitive- and resistive-based sensors within the electronic fibers, the monitoring of the resin flow and its curing during the production of FRPC parts is demonstrated. Finally, the embedded fiber sensors are used to measure and decouple thermal and mechanical loads imposed on the parts during their use, paving the way toward a new platform for smart and connected fiber reinforced polymer composites.  相似文献   
86.
    
Thoracic venous anomalies without congenital heart anomalies are present in minority of the population, but they are frequent enough to be encountered while placing hemodialysis catheters through the jugular or subclavian veins. Persistent left superior vena cava is the most commonly seen anomaly and it is rarely noticed before the observation of an unusual course of hemodialysis catheter or guidewire on chest X‐ray. We present two patients with previously unspotted persistent left superior vena cava and uncomplicated hemodialysis catheter insertions through the internal jugular veins with good catheter functions. Review of the relevant literature from a nephrologists’ perspective with technical aspects is provided.  相似文献   
87.
88.
    
Melamine based porous polymer (MPP) was prepared as a template solid to incorporate Cu(I) cations into the framework through chelating with nitrogen groups of the melamine. The copper integrated porous material (Cu(I)@MPP) was used as a heterogeneous catalyst and displayed high activity in copper catalyzed atom transfer radical polymerization of methyl methacrylate. The characterization of the Cu(I)@MPP was performed using nitrogen adsorption experiments and wide‐angle X‐ray and Fourier transform infrared spectroscopies. The atomic absorption spectroscopy measurements confirmed that the catalyst is practically non‐leaching and Cu(I) was found to be below 20 ppb after each atom transfer radical polymerization. Moreover, the catalyst showed reusability without any significant change in its activity. © 2017 Society of Chemical Industry  相似文献   
89.
    
This paper presents a performance‐guaranteed adaptive back‐stepping design for a class of nonlinear systems with uncertainties and disturbances. To circumvent the increasing complexity caused by the repeated analytic differentiations in back‐stepping, sliding mode differentiation technique is employed to estimate the derivative of the virtual control. Compared with the well‐known command filtered back‐stepping, no compensating signal is required. Besides, time‐varying parameters, system uncertainties and external disturbances are compensated using nonlinear damping technique, while the output tracking error is regulated in the prescribed range with the adjustable convergence speed and steady‐state error. As a verification example, this method is applied to the longitudinal control of an air‐breathing hypersonic vehicle configured with the variable geometry inlet.  相似文献   
90.
Molecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 μs and 2 nm, respectively.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号