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   2645篇
  免费   191篇
  国内免费   14篇
电工技术   49篇
综合类   17篇
化学工业   688篇
金属工艺   65篇
机械仪表   39篇
建筑科学   146篇
矿业工程   6篇
能源动力   132篇
轻工业   102篇
水利工程   12篇
石油天然气   7篇
无线电   259篇
一般工业技术   579篇
冶金工业   126篇
原子能技术   8篇
自动化技术   615篇
  2024年   6篇
  2023年   61篇
  2022年   124篇
  2021年   160篇
  2020年   107篇
  2019年   107篇
  2018年   111篇
  2017年   122篇
  2016年   133篇
  2015年   101篇
  2014年   159篇
  2013年   189篇
  2012年   216篇
  2011年   222篇
  2010年   136篇
  2009年   141篇
  2008年   121篇
  2007年   99篇
  2006年   81篇
  2005年   43篇
  2004年   47篇
  2003年   44篇
  2002年   33篇
  2001年   28篇
  2000年   23篇
  1999年   25篇
  1998年   37篇
  1997年   17篇
  1996年   9篇
  1995年   18篇
  1994年   9篇
  1993年   10篇
  1992年   11篇
  1991年   13篇
  1990年   16篇
  1989年   5篇
  1988年   4篇
  1987年   14篇
  1986年   3篇
  1985年   3篇
  1983年   5篇
  1981年   4篇
  1979年   3篇
  1977年   3篇
  1976年   3篇
  1975年   4篇
  1974年   3篇
  1973年   3篇
  1972年   4篇
  1971年   2篇
排序方式: 共有2850条查询结果,搜索用时 15 毫秒
71.
Simple SummaryA new sources of plant growth-promoting (PGP) bacteria are needed to increase the agricultural crops without increasing the usage of chemicals. The aim of this study was to test the hypothesis that insect-gut bacteria promote tomato plant growth. The insect gut bacteria were screened for the presence of PGP traits. The plants treated with bacterial consortium showed a significant increase in fruit yield, in both number of fruits (+41%) and weight of fruits (+44%). Our results showed that: (i) D. virgifera gut’s bacteria significantly promote the growth of tomato plants, and (ii) bacteria other than plant-related can be considered as PGP. It must be underlined that even though the insect gut bacteria were proven to stimulate the plant’s growth, their practical usage must be preceded by an examination of their influence on ecological and biological safety.AbstractWe investigated gut bacteria from three insect species for the presence of plant growth properties (PGP). Out of 146 bacterial strains obtained from 20 adult specimens of Scolytidae sp., 50 specimens of Oulema melanopus, and 150 specimens of Diabrotica virgifera, we selected 11 strains displaying the following: PGP, phosphate solubility, production of cellulase, siderophore, lipase, protease, and hydrogen cyanide. The strains were tested for growth promotion ability on tomato (Lycopersicon esculentum) plants. Each strain was tested individually, and all strains were tested together as a bacterial consortium. Tomato fruit yield was compared with the negative control. The plants treated with bacterial consortium showed a significant increase in fruit yield, in both number of fruits (+41%) and weight of fruits (+44%). The second highest yield was obtained for treatment with Serratia liquefaciens Dv032 strain, where the number and weight of yielded fruits increased by 35% and 30%, respectively. All selected 11 strains were obtained from Western Corn Rootworm (WCR), Diabrotica virgifera. The consortium comprised: Ewingella americana, Lactococcus garvieae, L. lactis, Pseudomonas putida, Serratia liquefaciens, and S. plymuthica. To our knowledge, this is the first successful application of D. virgifera gut bacteria for tomato plant growth stimulation that has been described.  相似文献   
72.
The chemical industry is one of the key industrial sectors in Germany and at the same time one of the largest consumers of energy and raw materials. A successful energy transition and the development of a circular economy can only succeed if they are actively supported and shaped by the chemical industry – through the redesign of existing production processes and the exploration and implementation of new process routes. The challenge is to realize this transformation within a very short time and for many production processes, whereby a much larger number of process routes must be explored. Digital technologies are key to master this transformation towards more sustainability, climate, and environmental protection. The KEEN project aims to explore and leverage artificial intelligence (AI) opportunities in process industry. The newly developed AI methods are tested wherever possible in real working environments and production plants to prove the economic benefit, applicability, and reliability of the methods and technologies.  相似文献   
73.
This publication presents a general approach for the enhancement of packings regarding scalability, separation efficiency, and fluid dynamic properties using three-dimensional (3D) printing. The methodology is used to develop miniaturized, scalable packings for process development, and scale-up applications. For this purpose, a 3D printable computer-aided design version of the Rombopak 9M industrial packing (RP9M-3D), which is known for its positive scalability properties, was created. An initial characterization by means of computational fluid dynamics simulations and mass transfer measurements reveals positive but also negative design properties. These findings are used to create a more advanced, miniaturized packing structure, the XW-Pak. The evolved structure is compared to the RP9M-3D. The simulation and experimental results show that the enhanced packing, which is still in the early stages of development, exhibits higher separation efficiencies with improved scalability properties at the same void fraction and surface area than the RP9M-3D.  相似文献   
74.
Hydrate–liquid–vapour (HLV) equilibrium of aqueous clathrates formed from gas mixtures can be complex compared to hydrates formed with single guests. Typically, pressure and temperature are controlled to obtain these data, but for multicomponent systems, it is necessary to control/report more intensive variables, namely, composition. Metastability, manifested as impractically long experimental times, has been reported to be a challenge with some multicomponent systems. We present HLV equilibrium conditions of two ternary gas mixtures: methane + ethane + propane (90:7:3 molar ratio) and methane + propane + carbon dioxide (55:5:40 molar ratio). Conditions varied in the temperature range of 275–285 K and the pressure range of 1.24–4.75 MPa. Experimental standard uncertainties were on average 0.10 K and 0.005 MPa for methane + ethane + propane and 0.19 K and 0.005 MPa for methane + propane + carbon dioxide. Our technique allowed us to bypass the limitations reported in the literature and provided fast, reproducible HLV equilibria for gas-dominated systems.  相似文献   
75.
A new method for inline characterization of particles in high concentrated dispersions by ultrasonic backscattering is described, that is sensitive against particle size and concentration. Analyzing the backscattering signal yields the sound attenuation as well as a scattering intensity equivalent. The measurement can be performed without sampling and minimally invasive directly in the process.  相似文献   
76.
The depletion of higher alkanes from methane is a key aspect during the conditioning of natural gases or accompanying gases. Membrane technologies could be used as alternative to energy and cost intensive purifications. Against this background the influence of membrane geometry, composition of the gas mixture as well as temperature and pressure was investigated in separation experiments for methane/n‐butane mixtures using MFI membranes.  相似文献   
77.
78.
Bioactive peptides often contain several disulfide bonds that provide the main contribution to conformational rigidity and structural, thermal, or biological stability. Among them, cystine‐knot peptides—commonly named “knottins”—make up a subclass with several thousand natural members. Hence, they are considered promising frameworks for peptide‐based pharmaceuticals. Although cystine‐knot peptides are available through chemical and recombinant synthetic routes, oxidative folding to afford the bioactive isomers still remains a crucial step. We therefore investigated the oxidative folding of ten protease‐inhibiting peptides from two knottin families, as well as that of an HIV entry inhibitor and of aprotinin, under two conventional sets of folding conditions and by a newly developed procedure. Kinetic studies identified folding conditions that resulted in correctly folded miniproteins with high rates of conversion even for highly hydrophobic and aggregation‐prone peptides in concentrated solutions.  相似文献   
79.
Among carbon capture and storage (CCS), the post-combustion capture of carbon dioxide (CO2) by means of chemical absorption is actually the most developed process. Steady state process simulation turned out as a powerful tool for the design of such CO2 scrubbers. Besides steady state modeling, transient process simulations deliver valuable information on the dynamic behavior of the system. Dynamic interactions of the power plant with the CO2 separation plant can be described by such models. Within this work a dynamic process simulation model of the absorption unit of a CO2 separation plant was developed. For describing the chemical absorption of CO2 into an aqueous monoethanolamine solution a rate based approach was used. All models were developed within the Aspen Custom Modeler® simulation environment. Thermo physical properties as well as transport properties were taken from the electrolyte non-random-two-liquid model provided by the Aspen Properties® database. Within this work two simulation cases are presented. In a first simulation the inlet temperature of the flue gas and the lean solvent into the absorber column was changed. The results were validated by using experimental data from the CO2SEPPL test rig located at the Dürnrohr power station. In a second simulation the flue gas flow to the separation plant was increased. Due to the unavailability of experimental data a validation of the results from the second simulation could not be achieved.  相似文献   
80.
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