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   3837篇
  免费   164篇
  国内免费   5篇
电工技术   39篇
综合类   2篇
化学工业   1015篇
金属工艺   132篇
机械仪表   93篇
建筑科学   119篇
矿业工程   18篇
能源动力   106篇
轻工业   523篇
水利工程   21篇
石油天然气   21篇
无线电   215篇
一般工业技术   866篇
冶金工业   101篇
原子能技术   26篇
自动化技术   709篇
  2024年   39篇
  2023年   73篇
  2022年   54篇
  2021年   150篇
  2020年   121篇
  2019年   123篇
  2018年   206篇
  2017年   201篇
  2016年   229篇
  2015年   165篇
  2014年   203篇
  2013年   426篇
  2012年   217篇
  2011年   238篇
  2010年   204篇
  2009年   183篇
  2008年   122篇
  2007年   80篇
  2006年   44篇
  2005年   59篇
  2004年   46篇
  2003年   51篇
  2002年   40篇
  2001年   33篇
  2000年   30篇
  1999年   30篇
  1998年   32篇
  1997年   28篇
  1996年   29篇
  1995年   24篇
  1994年   29篇
  1993年   27篇
  1992年   22篇
  1991年   19篇
  1990年   16篇
  1987年   26篇
  1986年   17篇
  1985年   28篇
  1984年   30篇
  1983年   26篇
  1982年   26篇
  1981年   22篇
  1980年   20篇
  1979年   17篇
  1978年   15篇
  1977年   23篇
  1976年   25篇
  1975年   19篇
  1974年   17篇
  1973年   18篇
排序方式: 共有4006条查询结果,搜索用时 0 毫秒
81.
On the basis of LC/UV/MS analysis, 35 compounds from the extracts of seeds of black, red, and white currants (2 cultivars of each) were identified. Black currants cultivars contained protocatechuic acid and p-hydroxybenzoic acid, and traces of nitril containing phenolic acids. The presence of synapoyl glucoside was characteristic for cv. Malling Jewel. Sesquiterpenoid glycosides and carboxymethylindol glycosides were present mainly in white and red currant cultivars. Blackcurrant seeds contained higher amounts of flavonoids, especially rutin, isoquercetin, and taxifolin. The currant seed extracts were tested for in vitro protective effect on chromosome aberrations in peripheral human lymphocytes using cytochalasin-B blocked micronucleus (CBMN) assay. The frequency of MN was scored in binucleated cells, and the cultivars of black currants showed the best antioxidant potential. At a concentration of only 0.17 mg/mL, extract of the seed cv. Malling Jewel effected a decrease in the frequency of MN of 60% compared with control cell cultures. PRACTICAL APPLICATION: Our results provide evidence of protective effects of currant seed extracts and isolated pure compounds on cytogenetic damages in human lymphocytes. Thus, currant seed extracts could exert beneficial effects in quite a few diseases, for many of the biological actions have been attributed to their antioxidant properties.  相似文献   
82.
The attractive prospect of a continuous beer fermentation system consists mostly of the accelerated transformation of wort into beer. Although continuous beer fermentation has been studied as a promising technology for several decades, the number of industrial applications is still limited. The major obstacle hindering the extensive industrial exploitation of this technology is the difficulty in achieving the correct balance of sensory compounds in the short time typical for continuous systems. This paper offers an integral view on the particularities of continuous systems, which may impart beer a sensorial character distinct from conventionally fermented counterparts. The main groups of flavour active compounds are discussed from the perspective of possible control strategies by means of process parameters and strain selection.  相似文献   
83.
We report on the application of supplementary light-emitting diode (LED) lighting within a greenhouse for cultivation of red, green and light green leaf baby lettuces (Lactuca sativa L.) grown under natural illumination and high-pressure sodium (HPS) lamps (16-h; PPFD-170 μmol m−2 s−1) during different growing season. Supplementary lighting from blue 455/470 nm and green 505/530 nm LEDs was applied (16-h; PPFD-30 μmol m−2 s−1). Our results showed that to achieve solely a positive effect is complicated, because metabolism of antioxidant properties in lettuce depended on multicomponent exposure of variety, light quality or seasonality. The general trend of a greater positive effect of supplemental LED components on the vitamin C and tocopherol contents was in order: 535 > 505 > 455 > 470 nm; on the total phenol content: 505 > 535 = 470 > 455 nm; on the DPPH free-radical scavenging capacity: 535 = 470 > 505 > 455 nm; on the total anthocyanins: 505 > 455 > 470 > 535 nm. Further investigations are needed for understanding the mechanism and interaction between antioxidants and light signal transduction pathways.  相似文献   
84.
Angular correlation of excitation functions in dissipative heavy ion collision 27Al+27A1 has been measured. The incident beam energies ranged from 114MeV to 127 MeV in steps of 200keV. The angular analysis region was continuous from 50° to 90° in the center of mass system. An angular coherent width, at least 40°, was obtained. This long-range angular correlation could not be interpreted in the framework of the standard statistical reaction theory with state of equilibrium or near equilibrium, maybe it reveals the formation of a new kind ofdissipative structure in the reaction of 27Al+27A1 with the state that is far from equilibrium.  相似文献   
85.
Decommissioning of nuclear facilities becomes an important issue in all areas of nuclear technology, mainly in their energetic applications. Decommissioning process has to be planned in the safe, ecological and economic manner. It determines the requirements on appropriate evaluation of needed technologies, media, amount of solid materials released into the environment, radioactivity of effluents, amount of radioactive waste for disposal, number and exposure of personnel and finally the financial demands. A detailed evaluation of these parameters may be done by analytical calculation approach. This approach models a real process of decommissioning with its individual basic activities. The methodology of integrated material flow and radioactivity distribution within this calculation evaluation tool is applied and implemented to describe the real decommissioning activities and their mutual relations to obtain more accurate outputs.  相似文献   
86.
Capabilities of spectroscopic ion beam analysis (IBA) techniques that are available in ion microprobe facilities can be greatly improved by the use of digital pulse processing. We report here development of a digital multi parameter data acquisition system suitable for IBA imaging applications. Input signals from charge sensitive preamplifier are conditioned by using a simple circuit and digitized with fast ADCs. The digitally converted signals are processed in real time using FPGA. Implementation of several components of the system is presented.  相似文献   
87.
Project work is becoming more and more important in everyday business, as is staffing the right newcomers for the project. Recognizing that not all new project team workers possess equally important specific knowledge, skills and abilities for the success of projects, we draw on project management, human resource management, and organizational socialization literature to develop a framework on how new project team members might be socialized, depending on their strategic value for the project. We specifically draw on the socialization tactics literature and propose how four categories of new employees – Internal specialists, External specialists, External generalists and Internal generalists; based on two dimensions – work task complexity and employment mode, can be socialized more effectively. Implications for theory and practice are discussed as well.  相似文献   
88.
Neural Computing and Applications - Successfully organizing the transport of hazardous materials and handling them correctly is a very important logistical task that affects both the overall flow...  相似文献   
89.

Nowadays, the stability and the safe cover and closure of soft tailings has become one of the most challenging topics in geotechnical and environmental engineering. For appropriate analysis and modelling, geotechnical properties of tailings should be well defined. Due to low strength, viscous nature and poor trafficability, as well as due to the specific geometrical properties of fine particles and pore water chemistry in tailings, different test methods and their modification and improvements must be used for valid and reliable characterisation of tailings. This paper analyses and compares the results of different field test methods, piezocone penetration test (CPTu), flat dilatometer test (DMT) and field vane test (FVT), performed on the red gypsum sludge and complementary laboratory tests. CPTu and DMT measurements were evaluated using procedures developed for soils and the obtained mechanical properties were compared with those measured in the laboratory. The significant distinctions between different test methods and different empirical correlations were analysed taking into account differences in index properties of soils and the red gypsum sludge. Based on analysis, some modifications of conventional empirical correlations were proposed for field tests results interpretation and sludge characterisation. The obtained data also show the advantages and limitations of some conventional methods and prove the need for further development in that field of geotechnical investigation.

  相似文献   
90.
High-dose gamma irradiation of electrodes provided with an active film consisting of 5 mol. % RuO2 and 95 mol. % TiO2 may produce electrodes whose chlorine overvoltage at 60°C in a solution containing 300 g NaCl per dm3 conforms to the relation
for
A 60Co source and doses about 4.9.105 C kg?1 (1.9 GR) were used. The gamma radiation has a positive effect of short duration in that it decreases the chlorine overvoltage, especially at higher cds. In the course of time the chlorine overvoltage of irradiated electrodes will increase beyond the values obtained with untreated electrodes.  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