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   1892篇
  免费   40篇
  国内免费   4篇
电工技术   71篇
化学工业   396篇
金属工艺   27篇
机械仪表   47篇
建筑科学   17篇
能源动力   77篇
轻工业   156篇
水利工程   2篇
石油天然气   3篇
无线电   205篇
一般工业技术   241篇
冶金工业   512篇
原子能技术   59篇
自动化技术   123篇
  2023年   6篇
  2022年   18篇
  2021年   43篇
  2020年   14篇
  2019年   15篇
  2018年   24篇
  2017年   25篇
  2016年   29篇
  2015年   23篇
  2014年   40篇
  2013年   95篇
  2012年   52篇
  2011年   71篇
  2010年   50篇
  2009年   77篇
  2008年   72篇
  2007年   60篇
  2006年   43篇
  2005年   48篇
  2004年   45篇
  2003年   54篇
  2002年   53篇
  2001年   47篇
  2000年   30篇
  1999年   50篇
  1998年   197篇
  1997年   117篇
  1996年   94篇
  1995年   64篇
  1994年   42篇
  1993年   49篇
  1992年   19篇
  1991年   7篇
  1990年   13篇
  1989年   27篇
  1988年   13篇
  1987年   12篇
  1986年   19篇
  1985年   18篇
  1984年   15篇
  1983年   15篇
  1982年   12篇
  1981年   11篇
  1980年   15篇
  1978年   10篇
  1977年   19篇
  1976年   22篇
  1974年   8篇
  1973年   5篇
  1970年   4篇
排序方式: 共有1936条查询结果,搜索用时 31 毫秒
1.
2.
Liquid marble (LM) is a droplet that is wrapped by hydrophobic solid particles, which behave as a non-wetting soft solid. Based on these properties, LM can be applied in fluidics and soft device applications. A wide variety of functional particles have been synthesized to form functional LMs. However, the formation of multifunctional LMs by integrating several types of functional particles is challenging. Here, a general strategy for the flexible patterning of functional particles on droplet surfaces in a patchwork-like design is reported. It is shown that LMs can switch their macroscopic behavior between a stable and active state on super-repellent surfaces in situ by jamming/unjamming the surface particles. Active LMs hydrostatically coalesce to form a self-sorted particle pattern on the droplet surface. With the support of LM handling robotics, on-demand cyclic activation–manipulation–coalescence–stabilization protocols by LMs with different sizes and particle types result in the reliable design of multi-faced LMs. Based on this concept, a single bi-functional LM is designed from two mono-functional LMs as an advanced droplet carrier.  相似文献   
3.
Closed-loop expressions for the minimum energy control of a single-input linear digital system are described. They are obtained by two different methods. The optimal inputs are given by state feedback with the bounded variable gains. The gains are independent of the initial state of the system  相似文献   
4.
A 4*4 directional coupler switch matrix is developed which uses, for the first time, the quantum confined Stark effect of InGaAlAs/InAlAs multiquantum well structures. The rearrangeable nonblocking 4*4 network with six 2*2 switches is shown to be perfectly functional with switching voltages between 5 and 6 V and crosstalk below -17 dB in all the operation states.<>  相似文献   
5.
A newly developed graded-index polymer optical fiber (GI-POF) with high-temperature and high-humidity stability was proposed. As it was found that the high numerical aperture and high glass transition temperature (T/sub g/) at the core center of the GI-POF were key issues to achieve both high-temperature and humidity stability, a partially fluorinated polymer material was adopted to obtain both characteristics in the GI-POF. The newly developed GI-POF had low-loss (140 dB/km at 650-nm wavelength), high-bandwidth (higher than 1 GHz for 100 m transmission), high-temperature and humidity stability at 70/spl deg/C, 80% relative humidity (R.H.) and low bending loss.  相似文献   
6.
7.
The effect of CF4 plasma etching on diamond surfaces, with respect to treatment time, was investigated using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. SEM observations and Raman spectra indicated an increase in surface roughening on a scale of 10–20 nm, and an increase in crystal defect density was apparent with treatment time in the range of 10 s to 30 min. In contrast, alteration of the diamond surface terminations from oxygen to fluorine was found to be rather rapid, with saturation of the F/C atomic ratio estimated from XPS analysis after treatment durations of 1 min and more. The redox kinetics of Fe(CN)63−/4− was also found to be significantly modified after 10 s of CF4 plasma treatment. This behavior shows that C–F terminations predominantly affect the redox kinetics compared to the effect on the surface roughness and crystal defects. The double-layer capacitance (Cdl) of the electrolyte/CF4 plasma-treated boron-doped diamond interface was found to show a minimum value at 1 min of treatment. These results indicate that a short-duration CF4 plasma treatment is effective for the fabrication of fluorine-terminated diamond surfaces without undesirable surface damage.  相似文献   
8.
We report on a single‐layer organic memory device made of poly(N‐vinylcarbazole) embedded between an Al electrode and ITO modified with Ag nanodots (Ag‐NDs). Devices exhibit high ON/OFF switching ratios of 104. This level of performance could be achieved by modifying the ITO electrodes with some Ag‐NDs that act as trapping sites, reducing the current in the OFF state. Temperature dependence of the electrical characteristics suggest that the current of the low‐resistance state can be attributed to Schottky charge tunnelling through low‐resistance pathways of Al particles in the polymer layer and that the high‐resistance state can be controlled by charge trapping by the Al particles and Ag‐NDs.  相似文献   
9.
Recently published studies indicate a potential clinical application of PET in head and neck tumors. In the preoperative staging phase, PET enables confirmation of regional lymph node extension and guides nodal neck dissection or systemic treatment. In this phase, a high negative predictive value, near 100%, could make it possible to avoid many negative neck dissections. This is a reliable technique for confirming or excluding the presence of recurrent/residual tumor and for obtaining an early evaluation of chemotherapeutic and radiotherapeutic response. PET imaging in many cases makes it possible to locate and guide histological study of tumors with an unknown primary. PET imaging for these indications is a perfect complementary method for clinical exploration and better than other imaging techniques.  相似文献   
10.
The DNA binding selectivity of new dicationic ligands based on the bis(vinylpyridinium)benzene unit has been investigated by means of UV-Vis absorption spectroscopy. From the experimental results it is concluded that these extended pi-electron bridged viologens have relatively high affinity to AT base pair sequences whereas the binding to GC pairs is about 10 times lower, and binding affinity depends on minor variation in the ligand structure. Linear type ligand exhibits two binding mode interaction, intercalation at high dye concentration which undergoes switching to groove binding at low ligand concentration.  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