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   9787篇
  免费   699篇
  国内免费   306篇
电工技术   361篇
综合类   381篇
化学工业   1580篇
金属工艺   522篇
机械仪表   614篇
建筑科学   501篇
矿业工程   171篇
能源动力   313篇
轻工业   459篇
水利工程   149篇
石油天然气   298篇
武器工业   30篇
无线电   1466篇
一般工业技术   1574篇
冶金工业   885篇
原子能技术   92篇
自动化技术   1396篇
  2024年   42篇
  2023年   132篇
  2022年   252篇
  2021年   338篇
  2020年   269篇
  2019年   279篇
  2018年   274篇
  2017年   267篇
  2016年   265篇
  2015年   349篇
  2014年   411篇
  2013年   602篇
  2012年   554篇
  2011年   598篇
  2010年   502篇
  2009年   536篇
  2008年   472篇
  2007年   464篇
  2006年   416篇
  2005年   399篇
  2004年   274篇
  2003年   276篇
  2002年   262篇
  2001年   250篇
  2000年   211篇
  1999年   261篇
  1998年   270篇
  1997年   220篇
  1996年   181篇
  1995年   164篇
  1994年   136篇
  1993年   107篇
  1992年   96篇
  1991年   82篇
  1990年   63篇
  1989年   67篇
  1988年   58篇
  1987年   46篇
  1986年   38篇
  1985年   42篇
  1984年   31篇
  1983年   22篇
  1982年   35篇
  1981年   26篇
  1980年   17篇
  1979年   14篇
  1977年   20篇
  1976年   19篇
  1974年   19篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Organic vertical-type triodes (OVTs) based on the cascade energy band structure as emitter layer are studied. The electric characteristics were dramatically enhanced while incorporating the cascade energy under current driving and voltage driving modes. The improvement is attributed to that injection carriers can obtain higher energy through a stepwise energy level. When the device has a layered structure of F16CuPC (10 nm)/PTCDI (10 nm)/pentacene (100 nm) in emitter, it exhibits a common-base transport factor of 0.99 and a common-emitter current gain of 225 under current driving mode and exhibits a high current modulation-exceeding ?520 μA for a low collector voltage of ?5 V and a base voltage of ?5 V and the current on/off ratio of 103 under voltage driving mode. Furthermore, we realized first organic current mirror that exhibited out/in current ratio of 0.75 and output resistance of 105 Ω by using the OVTs.  相似文献   
92.
In this brief, we present a new interconnect delay model called fitted Elmore delay (FED). FED is generated by approximating HSPICE delay data using a curve fitting technique. The functional form used in curve fitting is derived based on the Elmore delay (ED) model. Thus, our model has all the advantages of the ED model. It has a closed-form expression as simple as the ED model and is extremely efficient to compute. Interconnect optimization with respect to design parameters can also be done as easily as in the ED model. In fact, most previous algorithms and programs based on ED model can use our model without much change. Most importantly, FED is significantly more accurate than the ED model. The maximum error in delay estimation is at most 2% for our model, compared to 8.5% for the scaled ED model. The average error is less than 0.8%. We also show that FED can be more than 10 times more accurate than the ED model when applied to wire sizing.  相似文献   
93.
本文概述了移动通信网络对同步的需求,介绍了主要的同步技术,阐述了时间同步设备在工程上的实际组网应用。  相似文献   
94.
为了提高航空的安全性,降低发生故障的概率,很多部门开始深入研究航空电气系统绝缘电阻自动测试系统,进一步提高测试的准确度,降低测试成本,提高企业的经济效益.  相似文献   
95.
Cubic and octahedral Cu2O nanocrystals and Au–Cu2O core–shell heterostructures are used as sacrificial templates for the growth of Cu2S nanocages and Au–Cu2S core–cage structures. A rapid sulfidation process involving a surface reaction of Cu2O nanocrystals with Na2S, followed by etching of the Cu2O cores with HCl solution for ≈5 sec, results in the fabrication of Cu2S cages with a wall thickness of 10–20 nm. Transmission electron microscopy characterization reveals the formation of crystalline walls and the presence of ultrasmall pores with sizes of 1 nm or less. Formation of Cu2O–Cu2S core–shell structures and their conversion into Cu2S cages is verified by UV–vis absorption spectroscopy. X‐ray photoelectron spectra further confirm the composition of the cages as Cu2S. The entire hollowing process via the Kirkendall effect is recorded using in‐situ transmission X‐ray microscopy. After shell formation, continuous ionic diffusion removes the interior Cu2O. Intermediate structures with remaining central Cu2O portions and bridging arms to the surrounding cages are observed. The nanocages are also shown to allow molecular transport: anthracene and pyrene penetration into the cages leads to enhanced fluorescence quenching immediately upon adsorption onto the surfaces of the encapsulated gold nanocrystals.  相似文献   
96.
In this paper, we report on a novel family of monodisperse thermo‐sensitive core–shell hydrogel microspheres that is featured with high monodispersity and positively thermo‐responsive volume phase transition characteristics with tunable swelling kinetics, i.e., the particle swelling is induced by an increase rather than a decrease in temperature. The microspheres were fabricated in a three‐step process. In the first step, monodisperse poly(acrylamide‐co‐styrene) seeds were prepared by emulsifier‐free emulsion polymerization. In the second step, poly(acrylamide) or poly[acrylamide‐co‐(butyl methacrylate)] shells were fabricated on the microsphere seeds by free radical polymerization. In the third step, the core–shell microspheres with poly‐ (acrylamide)/poly(acrylic acid) based interpenetrating polymer network (IPN) shells were finished by a method of sequential IPN synthesis. The proposed monodisperse core–shell microspheres provide a new mode of the phase transition behavior for thermo‐sensitive “smart” or “intelligent” monodisperse micro‐actuators that is highly attractive for targeting drug delivery systems, chemical separations, sensors, and so on.  相似文献   
97.
Temperature variation-induced thermoelectric catalytic efficiency of thermoelectric material is simultaneously restricted by its electrical conductivity, Seebeck coefficient, and thermal conductivity. Herein, Bi2Te3 nanosheets are in situ grown on reduced graphene oxides (rGO) to generate an efficient photo-thermoelectric catalyst (rGO-Bi2Te3). This system exhibits phonon scattering effect and extra carrier transport channels induced by the formed heterointerface between rGO and Bi2Te3, which improves the power factor value and reduces thermal conductivity, thus enhancing the thermoelectric performance of 2.13 times than single Bi2Te3. The photo-thermoelectric catalysis of rGO-Bi2Te3 significantly improves the reactive oxygen species yields, resulting from the effective electron–hole separation caused by the unique thermoelectric field and heterointerfaces of rGO-Bi2Te3. Correspondingly, the electrospinning membranes containing rGO-Bi2Te3 nanosheets exhibit high antibacterial efficiency in vivo (99.35 ± 0.29%), accelerated tissue repair ability, and excellent biosafety. This study provides an insight into heterointerface design in photo-thermoelectric catalysis.  相似文献   
98.
Synthetic antiferromagnetic (SAF) skyrmions are emerging as novel information carriers due to their high mobility and lack of a skyrmion Hall effect. However, distinguishing SAF skyrmions from their ferromagnetic counterparts using imaging techniques like magneto-optical microscopy remains challenging. While the suppressed intrinsic skyrmion Hall effect (SkHE) has been commonly used to identify SAF skyrmions, it is important to note that other factors such as defect pinning and dipolar interaction can also lead to a suppressed SkHE. Therefore, there is an urgent need for a universal identification method that can reliably differentiate SAF skyrmions from ferromagnetic ones. In this study, the generation of a SAF skyrmion within a standard SAF stack is demonstrated and its motion with almost no SkHE is investigated. Furthermore, a universal identification method is proposed wherein the application of an out-of-plane field allows the SAF skyrmion to be decoupled into two domains, which can either expand or contract with the application of an electric current. By expediting the development of a reliable means of identifying SAF skyrmions, these findings will accelerate the realization of practical applications based on these unique information carriers.  相似文献   
99.
氧分子的三个电子激发的Herzberg态(A∧3∑∧ u,c∧1∑∧-u,A′∧3△u)在地球上层大气低温条件下的光化学动力学行为的实验研究为上层大气模型的建立提供重要的理论基础,本文介绍利用流动余辉技术和激光技术测量A∧3∑∧ 和c∧1∑∧-u态与大气分子碰撞反应速率常数的实验和结果,分析和讨论A∧3∑∧ u和c∧1∑∧-u态的高振动能级和低振动能级碰撞失活速率常数的巨大差别,并结合前人分析的结果提出自己的算法,最后,展望了实验研究上层气中Herzberg态动力学行为的前景。  相似文献   
100.
系统测试是项目验收的重要工作,也是保证软件项目质量的重要手段,系统测试工作的规范化、标准化、科学化,更有利于提高测试结果的准确性,从而提高项目的质量;依托东营软件园甲骨文公共技术服务平台项目,介绍了信息系统的类型及信息系统项目测试的流程,探讨了系统测试的关注点,分析了基于IBM云平台基础架构对Oracle软件产品进行二次开发配置的系统测试的流程及监理工作要点,实现了对系统测试的监理工作内容及要点的分析,指出了系统测试监理对软件工程监理的重要性。  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