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   464篇
  免费   29篇
  国内免费   1篇
电工技术   21篇
综合类   2篇
化学工业   107篇
金属工艺   21篇
机械仪表   13篇
建筑科学   9篇
能源动力   9篇
轻工业   35篇
水利工程   4篇
无线电   40篇
一般工业技术   85篇
冶金工业   80篇
原子能技术   11篇
自动化技术   57篇
  2024年   1篇
  2023年   7篇
  2022年   15篇
  2021年   18篇
  2020年   7篇
  2019年   18篇
  2018年   24篇
  2017年   23篇
  2016年   33篇
  2015年   15篇
  2014年   21篇
  2013年   27篇
  2012年   27篇
  2011年   31篇
  2010年   15篇
  2009年   22篇
  2008年   22篇
  2007年   18篇
  2006年   6篇
  2005年   17篇
  2004年   9篇
  2003年   7篇
  2002年   7篇
  2001年   1篇
  2000年   7篇
  1999年   4篇
  1998年   25篇
  1997年   13篇
  1996年   11篇
  1995年   6篇
  1994年   7篇
  1993年   8篇
  1992年   3篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1988年   3篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1976年   1篇
排序方式: 共有494条查询结果,搜索用时 15 毫秒
51.
Marcha or murcha is a traditional amylolytic starter used to produce sweet-sour alcoholic drinks, commonly called jaanr in the Himalayan regions of India, Nepal, Bhutan, and Tibet (China). The aim of this study was to examine the microflora of marcha collected from Sikkim in India, focusing on yeast flora and their roles. Twenty yeast strains were isolated from six samples of marcha and identified by genetic and phenotypic methods. They were first classified into four groups (Group I, II, III, and IV) based on physiological features using an API test. Phylogenetic, morphological, and physiological characterization identified the isolates as Saccharomyces bayanus (Group I); Candida glabrata (Group II); Pichia anomala (Group III); and Saccharomycopsis fibuligera, Saccharomycopsis capsularis, and Pichia burtonii (Group IV). Among them, the Group I, II, and III strains produced ethanol. The isolates of Group IV had high amylolytic activity. Because all marcha samples tested contained both starch degraders and ethanol producers, it was hypothesized that all four groups of yeast (Group I, II, III, and IV) contribute to starch-based alcohol fermentation.  相似文献   
52.
53.
We present the magnetic properties and the magnetic phase diagram of Ni50Mn50?xGax ferromagnetic shape memory alloys across a wide concentration range. Martensitic transformation, intermediate transformation, B2–L21 order–disorder transformation, Néel and Curie temperatures are determined for the prepared samples. The martensitic transformation temperature decreases with increasing Ga concentration and bends two times when crossing the Curie temperature and the intermediate-phase transformation temperature. Spontaneous magnetization and its composition dependence were also investigated. Composition dependence of the transformation temperatures and the spontaneous magnetization in the martensite phase of Ni50Mn50?xGax are compared with those of Ni50Mn50?xInx and Ni50Mn50?xSnx, revealing a similarity in the NiMn-based alloy systems.  相似文献   
54.
Changes made in 1997 and 1998 in the U.S. childhood immunization schedule are discussed, with a focus on the use of poliovirus, pertussis, and combination vaccines. Oral poliovirus vaccine (OPV), the vaccine of choice for all four doses in the polio immunization series since 1962, can cause vaccine-associated paralytic poliomyelitis (VAPP). The inactivated poliovirus vaccine (IPV) has not been associated with VAPP but must be administered by injection and provides inferior intestinal immunity. With the reduced threat of poliovirus importation into the United States, the risk of VAPP, although low, has become less acceptable. The Centers for Disease Control and Prevention accordingly recommended a shift from OPV to IPV in the childhood immunization schedule for the United States, effective January 1997. A sequential OPV and IPV series is recommended, but the schedule includes an OPV-only option, which may be preferred in order to avoid the required injections, and an IPV-only option, which is recommended for immunocompromised persons and their contacts. Concern over local and systemic reactions associated with whole-cell pertussis vaccines, in addition to controversy over a possible relationship between the whole-cell vaccine and neurologic damage, has led to the development of new diphtheria and tetanus toxoids and acellular pertussis vaccine products for use in the diphtheria and tetanus toxoids and pertussis immunization series. Several combination products were licensed in 1997, and more are on the way. This will mean fewer inoculations for children. Increased use of IPV and acellular pertussis products could reduce the frequency of VAPP due to OPV and the local and systemic reactions associated with whole-cell pertussis vaccine.  相似文献   
55.
Inoculation of Zygosaccharomyces rouxii into a soy sauce mash free from lactic acid bacteria at 106 cells mL−1 resulted in the formation of the flavour-active compound HEMF over a number of days at 30°C. Delays in inoculation up to 14 days after production of the mash greatly increased the amount of HEMF formed and under some conditions concentrations in the commercial range were achieved without addition of any other microorganisms.  相似文献   
56.
Phase equilibria in Fe-Cu-X (X: Co, Cr, Si, V) ternary systems   总被引:2,自引:0,他引:2  
Phase equilibria on the Fe-Cu side in the Fe-Cu-X (X: Co, Cr, Si, V) system were experimentally determined over the temperature range of 1073–1273 K. Based on the present results and previous works, the thermodynamic assessments of the phase equilibria in the Fe-Cu-X system were evaluated using the Calculation of Phase Diagram (CALPHAD) method. The Gibbs energies (G) of the bcc, fcc, and liquid phases are described by the subregular solution model, and a set of thermodynamic parameters enable us to calculate various isothermal and vertical sections and the miscibility gaps of the solid and liquid phases.  相似文献   
57.
For identifying human or finger movement, it is necessary to sense subtle movements at multiple points, including the local strain and global deformation simultaneously; however, this has not yet been realized. Therefore, a highly stretchable, global, and distributed local strain sensing electrode made of GaInSn and polydimethylsiloxane is developed for wearable devices. To investigate the electrical properties of multiple sections of the GaInSn electrode when stretching, tensile, cyclic, and three‐point‐bending tests are performed. The results demonstrate that the electrode can withstand a strain up to 50% and has little hysteresis without any delay. Moreover, the distributed local strain and global strain can be simultaneously measured using just a single electrode line. Finally, a prototype of a data glove as an application of the strain sensing line is manufactured, and it is demonstrated that the folding state of fingers could be identified. The proposed technology may allow the creation of a lightweight master hand manipulator or 3D data entry device.  相似文献   
58.
59.
Recently, renewable energy has been attracting attention as a result of global warming and the depletion of fossil fuels. Photovoltaic (PV) systems have spread rapidly around the world because they generate electric power quietly and can be installed in many places. The output power generated in a PV system fluctuates with changes in solar irradiance and panel temperature. The reverse flow of surplus power in output spikes may have a negative effect on electric power quality, such as on the frequency and voltage in a power system. A residential distributed generation (DG) system composed of a fuel cell (FC) unit, an electrolyzer (EL) unit, and a PV system has been proposed in order to resolve these problems. In order to operate this system without interruption, the hydrogen storage volume must be managed. This paper proposes a novel hydrogen management method for a residential DG system with PV cells and hydrogen‐storage type FCs. The hydrogen storage volume is maintained at the preset frequency by operating the FC unit and the EL unit. Models of the PV, FC, and EL were constructed for a simulation. In the simulation, we showed that the proposed management method is viable for a residential DG system with PV cells and hydrogen‐storage FCs.  相似文献   
60.
This paper presents a novel posture control approach using feedback compensation with an unstable pole. For a narrow and small personal mobility robot (PMR), this is needed in order to control its posture for achieving quick turning and high acceleration. However, in the conventional control approach that uses the posture angle as a controlled variable, the zero moment point (ZMP) does not settle to the desired point in the following cases: an unknown disturbance force given to the PMR, a fluctuation in the center of gravity of the PMR, and a change in the conditions between the tires and the road surface. In this paper, a novel control method using feedback compensation with an unstable pole is proposed to achieve the desired ZMP in the steady state. The proposed controller changes the control input for the actuator of posture control to zero in order to achieve the desired posture angle. The effectiveness of the proposed approach is verified through experiments using a prototype of the PMR.  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