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   49782篇
  免费   1255篇
  国内免费   150篇
电工技术   753篇
综合类   84篇
化学工业   9406篇
金属工艺   1691篇
机械仪表   2578篇
建筑科学   1075篇
矿业工程   44篇
能源动力   1829篇
轻工业   3533篇
水利工程   217篇
石油天然气   167篇
武器工业   3篇
无线电   8733篇
一般工业技术   9902篇
冶金工业   4900篇
原子能技术   545篇
自动化技术   5727篇
  2024年   417篇
  2023年   505篇
  2022年   718篇
  2021年   1256篇
  2020年   990篇
  2019年   1062篇
  2018年   1135篇
  2017年   1133篇
  2016年   1497篇
  2015年   1118篇
  2014年   1758篇
  2013年   2933篇
  2012年   2706篇
  2011年   3331篇
  2010年   2493篇
  2009年   2685篇
  2008年   2477篇
  2007年   2083篇
  2006年   1907篇
  2005年   1622篇
  2004年   1549篇
  2003年   1432篇
  2002年   1380篇
  2001年   1049篇
  2000年   1023篇
  1999年   1007篇
  1998年   1862篇
  1997年   1245篇
  1996年   987篇
  1995年   820篇
  1994年   595篇
  1993年   580篇
  1992年   420篇
  1991年   401篇
  1990年   367篇
  1989年   319篇
  1988年   254篇
  1987年   220篇
  1986年   212篇
  1985年   193篇
  1984年   166篇
  1983年   128篇
  1982年   113篇
  1981年   103篇
  1980年   108篇
  1979年   77篇
  1978年   80篇
  1977年   107篇
  1976年   138篇
  1975年   70篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We propose a fast and effective technique to improve sub‐grid visual details of the grid based fluid simulation. Our method procedurally synthesizes the flow fields coming from the incompressible Navier‐Stokes solver and the vorticity fields generated by vortex particle method for sub‐grid turbulence. We are able to efficiently animate smoke which is highly turbulent and swirling with small scale details. Since this technique does not solve the linear system in high‐resolution grids, it can perform fluid simulation more rapidly. We can easily estimate the influence of turbulent and swirling effect to the fluid flow.  相似文献   
102.
An improved digital image processing procedure is developed to extract the size and shape of the plastic zone formation at the tip of a notched metal specimen based on the characteristics of the variation of intensity in a digitized image. The result is compared with the result from finite element analysis, and with that from a previously developed image processing procedure. Comparison shows that this method provides a faster and more accurate result than previously.  相似文献   
103.
Peer-to-Peer Networking and Applications -  相似文献   
104.
The Leader–Member Exchange (LMX) relationship quality between superiors and subordinates in Korean civil engineering companies were empirically examined for superiors’ feedback-seeking behaviors. The results showed that for superiors, affect, loyalty, and contribution toward subordinates were positively related to seeking negative as well as positive feedback from subordinates. From subordinates’ point of view, affect, contribution, and professional respect toward their superiors were positively related to superiors’ negative feedback seeking, but affect was negatively related to superiors’ positive feedback seeking. It was also found that superiors and subordinates were not consensual in LMX and superiors’ feedback-seeking behaviors. For example, for superiors, all of the four LMX dimensions were positively related to superiors’ asking subordinates directly for feedback, whereas for subordinates, none of the LMX dimensions were significantly related to superiors’ asking subordinates directly for feedback. These and other findings are discussed in detail, and implications for the findings are provided.  相似文献   
105.
S.N. Huang  K.K. Tan  T.H. Lee 《Automatica》2005,41(12):2161-2162
In Kim et al. [(1997) A dynamic recurrent neural-network-based adaptive observer for a class of nonlinear systems. Automatica 33(8), 1539–1543], authors present an excellent neural network (NN) observer for a class of nonlinear systems. However, the output error equation in their paper is strictly positive real (SPR) which is restrictive assumption for nonlinear systems. In this note, by introducing a vector b0 and Lyapunov equation, the observer design is obtained without requiring the SPR condition. Thus, our observer can be applied to a wider class of systems.  相似文献   
106.
A torsional micromechanical scanner was fabricated using photosensitive polymer (SU-8). The proposed polymer-based optical microscanner with reduced torsional stiffness offers a new approach to increase scanning angles. The scanner consists of two parts; the top layer (micro mirror and electrodes) and the bottom layer (anchors and electrodes). The SU-8 scanner is actuated by electrostatic force generated by gap-closing electrodes. For the fabricated optical scanner with the mirror size of 3 × 3 mm2, the experimentally obtained scanning angles were 0.43° for 60 Hz (non-resonant) and 1.54° for 1.13 kHz (resonant) at the input voltage of 160 V. This paper also proposes a simple and new fabrication method, which can effectively control the stiffness of the torsional springs by molding SU-8 photoresist through V-groove on the silicon substrate, thereby increasing the scanning angles.  相似文献   
107.
The serum neutralization (SN) test has been regarded as the “gold standard” for seroconversion following foot-and-mouth disease virus (FMDV) vaccination, although a high-level biosafety laboratory is necessary. ELISA is one alternative, and its format is constantly being improved. For instance, standard polyclonal antisera have been replaced by monoclonal antibodies (MAbs) for catching and detecting antibodies, and inactive viruses have been replaced by virus-like particles (VLPs). To the best of current knowledge, however, no researchers have evaluated the performances of different MAbs as tracers. In previous studies, we successfully identified site 1 and site 2 MAbs Q10E and P11A. In this study, following the established screening platform, the VLPs of putative escape mutants from sites 1 to 5 were expressed and used to demonstrate that S11B is a site 3 MAb. Additionally, the vulnerability of VLPs prompted us to assess another diagnostic antigen: unprocessed polyprotein P1. Therefore, we established and evaluated the performance of blocking ELISA (bELISA) systems based on VLPs and P1, pairing them with Q10E, P11A, S11B, and the non-neutralizing TSG MAb as tracers. The results indicated that the VLP paired with S11B demonstrated the highest correlation with the SN titers (R2 = 0.8071, n = 63). Excluding weakly positive serum samples (SN = 16–32, n = 14), the sensitivity and specificity were 95.65% and 96.15% (kappa = 0.92), respectively. Additionally, the P1 pairing with Q10E also demonstrated a high correlation (R2 = 0.768). We also discovered that these four antibodies had steric effects on one another to varying degrees, despite recognizing distinct antigenic sites. This finding indicated that MAbs as tracers could not accurately detect specific antibodies, possibly because MAbs are bulky compared to a protomeric unit. However, our results still provide convincing support for the application of two pairs of bELISA systems: VLP:S11B-HRP and P1:Q10E-HRP.  相似文献   
108.
Digital halftoning is a technique to display a gray-level image with a bilevel device. Conventionally, most halftoning techniques are done in the spatial domain. A new halftoning technique based on the discrete cosine transform is proposed. The method chooses an optimal bilevel image to display the original gray-level image and minimize the weighted mean square error based on the discrete cosine transform domain. The simulation results indicate that our algorithm can produce very good halftoned images without false contours.  相似文献   
109.
Novel forces in image segmentation based on active contours models are proposed for capturing objects in the image. Contemplating the common functionality of forces in previous active contours models, we propose the geometric attraction-driven flow (GADF), the binary edge function, and the binary balloon forces to detect objects in difficult cases such as varying illumination and complex shapes. The orientation of GADF is orthogonally aligned with the boundary of object and has the opposite direction across the boundary. It prevents the leakage through weak edges of objects, which occur due to illumination. To reduce the interference from other forces, we design the binary edge function using the property of the orientation in the GADF. We also design the binary balloon force based on the four-color theorem. Combining with initial dual level set functions, the proposed model captures holes in objects and multiple junctions from different colors. The result does not depend on positions of initial contours.  相似文献   
110.
A new series of charge neutral Os(II) isoquinolyl triazolate complexes ( 1 – 4 ) with both trans and cis arrangement of phosphine donors are synthesized, and their structural, electrochemical and photophysical properties are established. In sharp contrast to the cis‐arranged complexes 2 – 4 , the trans derivative 1 , which shows a planar arrangement of chromophoric N‐substituted chelates, offers the most effective extended π‐delocalization and hence the lowest excited state energy gap. These complexes exhibit phosphorescence with peak wavelengths ranging from 692–805 nm in degassed CH2Cl2 at room temperature. Near‐infrared (NIR)‐emitting electroluminescent devices employing 6 wt % of 1 (or 4 ) doped in Alq3 host material are successfully fabricated. The devices incorporating 1 as NIR phosphor exhibit fairly intense emission with a peak wavelength at 814 nm. Forward radiant emittance reaches as high as 65.02 µW cm?2, and a peak EQE of ~1.5% with devices employing Alq3, TPBi and/or TAZ as electron‐transporting/exciton‐blocking layers. Upon switching to phosphor 4 , the electroluminescence blue shifts to 718 nm, while the maximum EQE and radiance increase to 2.7% and 93.26 (μW cm?2) respectively. Their performances are optimized upon using TAZ as the electron transporting and exciton‐blocking material. The OLEDs characterized represent the only NIR‐emitting devices fabricated using charge‐neutral and volatile Os(II) phosphors via thermal vacuum deposition.  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