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   1064篇
  免费   48篇
电工技术   11篇
综合类   1篇
化学工业   282篇
金属工艺   33篇
机械仪表   49篇
建筑科学   57篇
矿业工程   1篇
能源动力   35篇
轻工业   60篇
水利工程   7篇
石油天然气   1篇
无线电   67篇
一般工业技术   220篇
冶金工业   78篇
原子能技术   4篇
自动化技术   206篇
  2023年   17篇
  2022年   6篇
  2021年   49篇
  2020年   37篇
  2019年   47篇
  2018年   33篇
  2017年   18篇
  2016年   36篇
  2015年   37篇
  2014年   41篇
  2013年   63篇
  2012年   70篇
  2011年   87篇
  2010年   67篇
  2009年   53篇
  2008年   46篇
  2007年   62篇
  2006年   41篇
  2005年   39篇
  2004年   25篇
  2003年   14篇
  2002年   26篇
  2001年   13篇
  2000年   14篇
  1999年   9篇
  1998年   33篇
  1997年   19篇
  1996年   15篇
  1995年   17篇
  1994年   8篇
  1993年   7篇
  1992年   5篇
  1991年   2篇
  1990年   5篇
  1989年   3篇
  1988年   7篇
  1987年   7篇
  1986年   4篇
  1985年   5篇
  1983年   3篇
  1981年   3篇
  1980年   2篇
  1977年   2篇
  1976年   3篇
  1972年   1篇
  1971年   1篇
  1969年   2篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
排序方式: 共有1112条查询结果,搜索用时 406 毫秒
81.
With the increasing demand for alternative fuels the storage of natural gas (NG) in adsorbents like metal organic frameworks (MOFs) will become more important. In order to use MOFs as storage media in fuel delivery systems, the optimization of mass and energy transfer of the system is crucial. For rapid NG filling of a tank, molecules need to reach the adsorption sites within a reasonable time while the heat of adsorption should be dissipated to the environment. In this article, mass transfer in shaped bodies of MOFs was determined by permeability measurements and pulsed field gradient (PFG) NMR spectroscopy. The heat dissipation was also experimentally measured and both data sets were used to set up a theoretical density function theory model to predict the behavior of MOFs for NG storage.  相似文献   
82.
By means of a simple optical apparatus the levels and variations of concentrations of elemental carbon in particles were measured. Additionally, relations between variations of elemental carbon, lead, sulfate, total suspended particle, and nitrate concentrations were studied. Calibration was performed on real samples analyzed by a wet chemical method.  相似文献   
83.
Titania microspheres with narrow size distribution and diameters of about 1 µm were prepared and subsequently functionalized using surface‐initiated atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide. The ATRP initiator was immobilized on the particle surface via acylation of surface hydroxyl groups with α‐bromoisobutyryl bromide. Subsequently, an established ATRP reaction system was used for the preparation of titania surface‐grafted poly(N‐isopropylacrylamide) (PNiPAAm). Characterization was performed with electron microscopies, X‐ray diffraction, infrared spectroscopy and dynamic light scattering. It was found that the particle size in aqueous dispersions changed reversibly with temperature as expected for a shell of PNiPAAm, a polymer with a lower critical solution temperature at 32 °C. This confirmed the successful preparation of functional, stimuli‐responsive TiO2 microparticles via a straightforward controlled surface‐initiated polymerization method.  相似文献   
84.
Histidase (histidine ammonia-lyase, EC 4.3.1.3) from Pseudomonasputida was expressed in Escherichia coli and purified. In theabsence of thiols the tetrameric enzyme gave rise to undefinedaggregates and suitable crystals could not be obtained. Thesolvent accessibility along the chain was predicted from theamino acid sequence. Among the seven cysteines, only one waslabeled as `solvent-exposed'. The exchange of this cysteineto alanine abolished all undefined aggregations and yieldedreadily crystals diffracting to 1.8 Å resolution.  相似文献   
85.
In this article, activation energies for a poly(methyl methacrylate) material were determined by shear rheometry and by bond strength in welding. Functions for temperature dependency of viscosity and for bond strength, depending on time and temperature, were found. These functions were fitted to measurements from shear rheometry between 230 and 270 °C and from strength of lap-shear joints welded from 105 to 130 °C, where by values of activation energies were found. It was found that bonding pressure was less than significant. Despite experimental differences, there was good correlation with data from literature for each method as well as for temperature dependency.  相似文献   
86.
The Smart Factory is the central element of Industry 4.0 and establishes the foundation to enable integrated value chains across companies. The linkage of information along value chains offers a wide range of opportunities and potentials to realize new innovative solutions.  相似文献   
87.
Climate change challenges water managers and researchers to find sustainable management solutions, in order to avoid undesirable impacts on water resources, environment and water-dependent sectors. Needed are projections into the future for the main driving forces, the resulting pressures on water resources, and quantification of the impacts. Modeling studies can play an important role in investigating, quantifying, and communicating possible impacts of climate change, with account of uncertainty of the results. However, climate change related impacts and a need for adaptation still play a minor role in current river basin management plans that have to comply e.g. with the EU Water Framework Directive (WFD). One important reason is that climate impact assessment is generally done in research institutes, while management plans are designed by practitioners working in national and regional environmental agencies and water supply companies. Knowledge transfer from science to practice and visa versa is often missing. In the present study, we propose a methodology and a case study for model-supported decision making in the water sector applicable to a participatory water resources planning process. The methodology is applied in a case study investigating climate change impacts on water resources. The case study area is the German State of Saxony-Anhalt, where the task was to develop a climate change impact assessment including possible adaptation measures as basis for a federal adaptation directive.  相似文献   
88.
89.
Novel composites on basis of austenitic stainless TRIP‐steel as matrix with reinforcements of Mg‐PSZ are presented. Compact rods were produced by cold isostatic pressing and sintering, square honeycomb samples by the ceramic extrusion technique. The samples are characterized by optical and scanning electron microscopy before and after deformation, showing the microstructure and the deformation‐ induced martensite formation. The mechanical properties of samples with 5 vol% zirconia are superior compared to zirconia‐free samples and composites with higher zirconia contents in terms of bending and compression tests. The honeycomb samples exhibit extraordinary high specific energy absorption in compression.  相似文献   
90.
Reports an error in "'Personality and citizenship behavior: The mediating role of job satisfaction': Correction" by Remus Ilies, Ingrid Smithey Fulmer, Matthias Spitzmuller and Michael D. Johnson (Journal of Applied Psychology, 2010[Mar], Vol 95[2], 404). The volume number of the original article was incorrectly identified. It should have been identified as Vol. 94. (The following abstract of the original article appeared in record 2010-04488-016.) Reports an error in "Personality and citizenship behavior: The mediating role of job satisfaction" by Remus Ilies, Ingrid Smithey Fulmer, Matthias Spitzmuller and Michael D. Johnson (Journal of Applied Psychology, 2009[Jul], Vol 94[4], 945-959). The path coefficients presented in the figures are slight overestimates. For example, in Figure 1 (p. 952), the paths from Agreeableness and Conscientiousness to Job Satisfaction should be .11 and .23 instead of .12 and .28, the direct effects from Agreeableness and Conscientiousness to Citizenship Behavior should be .10 and .16 instead of .11 and .18, and the paths from Job Satisfaction to Citizenship Behavior should be .28 (.22) instead of .34 (.26). The statistical significance of the path coefficients is correct, and so are the substantive conclusions based on the better fit of the partially mediated models relative to the fully mediated models. Also, the meta-analytic estimates presented in Table 1 (p. 949), Table 2 (p. 950), and Table 3 (p. 951) are correct. (The following abstract of the original article appeared in record 2009-10167-018.) Using meta-analytic path analysis, the authors tested several structural models linking agreeableness and conscientiousness to organizational citizenship behavior (OCB). Results showed that the 2 personality traits had both direct effects and indirect effects—through job satisfaction—on overall OCB. Meta-analytic moderator analyses that distinguished between individual- and organization-targeted citizenship behaviors (OCB-I and OCB-O) showed that agreeableness was more closely related with OCB-I and conscientiousness with OCB-O. Finally, the path analyses predicting OCB-I and OCB-O offered further support for the general hypothesis that these 2 constructs are distinct. That is, the results of these analyses revealed that agreeableness had both direct and indirect effects on OCB-I but only indirect effects on OCB-O, and that for conscientiousness the pattern of direct and indirect effects was exactly opposite (direct and indirect effects on OCB-O but only indirect effects on OCB-I). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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