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   777篇
  免费   28篇
电工技术   7篇
化学工业   182篇
金属工艺   6篇
机械仪表   31篇
建筑科学   34篇
矿业工程   8篇
能源动力   55篇
轻工业   104篇
水利工程   6篇
无线电   51篇
一般工业技术   113篇
冶金工业   124篇
原子能技术   6篇
自动化技术   78篇
  2024年   2篇
  2023年   3篇
  2022年   9篇
  2021年   26篇
  2020年   16篇
  2019年   14篇
  2018年   15篇
  2017年   13篇
  2016年   18篇
  2015年   11篇
  2014年   31篇
  2013年   46篇
  2012年   51篇
  2011年   57篇
  2010年   40篇
  2009年   50篇
  2008年   42篇
  2007年   39篇
  2006年   17篇
  2005年   22篇
  2004年   18篇
  2003年   12篇
  2002年   26篇
  2001年   10篇
  2000年   12篇
  1999年   15篇
  1998年   49篇
  1997年   20篇
  1996年   22篇
  1995年   19篇
  1994年   9篇
  1993年   15篇
  1992年   6篇
  1991年   5篇
  1990年   4篇
  1989年   4篇
  1987年   3篇
  1985年   5篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1979年   4篇
  1978年   2篇
  1976年   8篇
  1975年   4篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
  1968年   1篇
排序方式: 共有805条查询结果,搜索用时 234 毫秒
801.
Morales R  Serra X  Guerrero L  Gou P 《Meat science》2007,77(4):662-669
The aim of the study was to quantify the effect of meat quality characteristics and some processing conditions on the softness of dry-cured biceps femoris (BF) muscles. The BF muscles were dissected from forty hams and classified according to their pHBF into three groups: LpH (pH < 5.66), MpH (5.66  pH  6.00) and HpH (pH > 6.00). BF muscles within each pHBF group were distributed into three different Salting levels (1%, 2% or 4% of added NaCl). Muscles were salted, vacuum-packed and stored at 3 °C for 30 days. The post-salting BF muscles were classified into two intramuscular fat (IMF) levels: Low (IMF < 4%) and High (IMF  4%). Thereafter, the muscles were divided into two pieces and dried at two of the three different Drying levels (1.5, 2 and 2.5 g H2O/g desalted dry matter). Then, each piece was divided into two samples that were packed in N2 and stored at 5 °C or 30 °C for 1 month. Stress Relaxation was used to evaluate texture. Dry-cured BF muscles with initial pH > 6.0, with IMF > 4% or with added NaCl levels less than 2% were more prone to show soft texture. Softness in dry-cured muscles can be reduced by applying an ageing temperature of 30 °C for 30 days, despite increasing proteolysis. The softness reduction by ageing at 30 °C compared with 5 °C is expected to be higher when applied to drier samples, which show a smaller increase in proteolysis.  相似文献   
802.
Lubricants are of paramount importance in protecting metallic contact surfaces and reducing friction. The viscosity of lubricating oil can be engineered by introducing long linear polymers, such as poly(lauryl methacrylate) (PLMA). In particular, the formation of adsorption films by using polymers with hydroxy or amino side groups has attracted much attention in recent years. In this study, copolymers with controlled structure were synthesised by SARA ATRP, which can be used in large scale production. A comparison of friction and wear under boundary lubrication was conducted using both statistical and block copolymers with low Ð. Friction test results using a reciprocating sliding machine (SRV) showed that the block copolymers were less likely to desorb from the metal surface than the statistical copolymers. In addition, the wear evaluation after the SRV test showed that the block copolymer had less wear and less wear debris.  相似文献   
803.
Universal Access in the Information Society - This study thoroughly examines the usability of digital materials, to establish a classroom environment in which technology is integrated into teaching...  相似文献   
804.
Porphyrins, a type of heterocyclic aromatic compounds consisting of tetrapyrroles connected by four substituted methine groups, are appealing building blocks for solar energy applications. However, their photosensitization capability is limited by their large optical energy gap, which results in a mismatch in absorption toward efficient harvesting of the solar spectrum. Porphyrin π-extension by edge-fusing with nanographenes can be employed for narrowing their optical energy gap from 2.35 to 1.08 eV, enabling the development of porphyrin-based panchromatic dyes with an optimized energy onset for solar energy conversion in dye-sensitized solar fuel and solar cell configurations. By combining time-dependent density functional theory with fs transient absorption spectroscopy, it is found that the primary singlets, which are delocalized across the entire aromatic part, are transferred into metal centred triplets in only 1.2 ps; and subsequently, relax toward ligand-delocalized triplets. This observation implies that the decoration of the porphyrin moiety with nanographenes, while having a large impact on the absorption onset of the novel dye, promotes the formation of a ligand-centred lowest triplet state of large spatial extension, potentially interesting for boosting interactions with electron scavengers. These results reveal a design strategy for broadening the applicability of porphyrin-based dyes in optoelectronics.  相似文献   
805.
Even though the simulations used to describe the failure of laminates are becoming more and more predictive, complex testing under multiaxial loadings is still required to validate the design of structural parts in a wide range of industrial domains. It is thus essential to assess the actual boundary conditions to allow for an objective comparison between testing and calculations, in particular since the structural tests are complex and often leads to buckling. Therefore, accurate estimation of force and moment fluxes applied to the specimen is critical. In this context, stereo digital image correlation (SDIC) has proven to be an important measurement tool and provides very well-resolved surface displacement fields, but the exploitation of such measurements to calculate fluxes remains problematic when testing composites. The first objective of this study is both to reduce the uncertainty associated with fluxes determination on a complex test and to simplify the extraction process with respect to existing procedures. The second objective is to make this methodology robust to geometrically non-linear deformations. In this paper, we propose a new methodology that extracts minimal boundary conditions in the form of 3D mechanically admissible displacements fields. The approach developed uses a finite element SDIC (FE-SDIC) method regularized by means of mechanical behaviour admissibility equations. Results show that the new methodology outputs much more accurate fluxes than classical data generated from multiple differentiations of the displacement fields. Excellent noise robustness is obtained and quantified. Numerical predictions have been satisfactorily compared with experimental data from one structural-scale composite specimen under complex testing.  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