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   12818篇
  免费   396篇
  国内免费   58篇
电工技术   260篇
综合类   16篇
化学工业   2278篇
金属工艺   367篇
机械仪表   361篇
建筑科学   219篇
矿业工程   73篇
能源动力   703篇
轻工业   1179篇
水利工程   190篇
石油天然气   82篇
无线电   1623篇
一般工业技术   2771篇
冶金工业   1544篇
原子能技术   198篇
自动化技术   1408篇
  2024年   39篇
  2023年   177篇
  2022年   505篇
  2021年   504篇
  2020年   409篇
  2019年   407篇
  2018年   554篇
  2017年   512篇
  2016年   484篇
  2015年   281篇
  2014年   447篇
  2013年   887篇
  2012年   519篇
  2011年   678篇
  2010年   541篇
  2009年   531篇
  2008年   477篇
  2007年   389篇
  2006年   331篇
  2005年   264篇
  2004年   244篇
  2003年   219篇
  2002年   180篇
  2001年   143篇
  2000年   147篇
  1999年   156篇
  1998年   355篇
  1997年   233篇
  1996年   251篇
  1995年   219篇
  1994年   183篇
  1993年   171篇
  1992年   143篇
  1991年   151篇
  1990年   114篇
  1989年   108篇
  1988年   130篇
  1987年   109篇
  1986年   89篇
  1985年   115篇
  1984年   94篇
  1983年   107篇
  1982年   99篇
  1981年   88篇
  1980年   78篇
  1979年   54篇
  1978年   46篇
  1977年   56篇
  1976年   76篇
  1975年   32篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Glibenclamide has limited gastrointestinal absorption. Therefore, different concentrations of sodium lauryl sulphate and tweenR80 were included into the tablet formulations to increase the absorption of the drug and hence, to enhance the BSL lowering in rabbits and human volunteers suffering from maturity onset diabetes mellitus. It was found that the surfactants had enhanced both the rate and extent of BSL lowering in rabbits as well as in diabetic patients in higher concentrations present in the tablet formulations.  相似文献   
12.
Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D6 Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis.  相似文献   
13.
The degradation behaviour of Kodar [poly(1,4-cyclohexylene dimethyl-eneterephthalate)] was investigated in air using thermogravimetry, differential thermal analysis and wide angle X-ray diffraction studies. The rates of crystallization and degradation were influenced by thermal exposure and polychromatic irradiation (Λ > 290 nm) for different time intervals. The crystallinity changes (Xc%) and activation energies (ΔE) for the systems have been determined.  相似文献   
14.
Cladosporium herbarum grown as a surface culture in a chemically defined medium of sucrose and inorganic salts gave a high yield of fat (29.2%). The component acids of this fat have been found to be palmitic (34.2%); oleic (15.9%); linoleic (34.2%) and linolenic (15.7%). The combined proportion of linoleic and linolenic acids being about 50 per cent, the fat will be of great value for the manufacture of oil-modified resins as the films produced by such resins do not become yellow with age.  相似文献   
15.
The Journal of Supercomputing - Cluster-based routing protocols have been proven efficient in prolonging the life cycle of wireless sensor networks (WSNs). Periodic and multi-hop clustering are the...  相似文献   
16.
Neural Computing and Applications - Grouping the sensor nodes into clusters is an effective way to organize wireless sensor networks and to prolong the networks’ lifetime. This paper presents...  相似文献   
17.
Ionic flow associated with neural activation of the brain produces a magnetic field, called the neuromagnetic field, that can be measured outside the head using a highly sensitive superconducting quantum interference device (SQUID)-based neuromagnetometer. Under certain conditions, the sources producing the neuromagnetic field can be localized from a sampling of the neuromagnetic field. Neuromagnetic measurements alone, however, do not contain sufficient information to visualize brain structure. Thus, it is necessary to combine neuromagnetic localization with an anatomical imaging technique such as magnetic resonance imaging (MRI) to visualize both function and anatomy in vivo. Using experimentally measured human neuromagnetic fields and magnetic resonance images, the authors have developed a technique to register accurately these two modalities and have applied the registration procedure to portray the spatiotemporal distribution of neural activity evoked by auditory stimulation.  相似文献   
18.
The nonlinear Boussinesq equation is used to understand water table fluctuations in various ditch drainage problems. An approximate solution of this equation with a random initial condition and deterministic boundary conditions, recharge rate and aquifer parameters has been developed to predict a transient water table in a ditch-drainage system. The effects of uncertainty in the initial condition on the water table are illustrated with the help of a synthetic example. These results would find applications in ditch-drainage design.Notation A / tanh t - a lower value of the random variable representing the initial water table height at the mid point - a+b Upper value of the random variable representing the initial water table height at the midpoint - B tanh t - C 4/ - h variable water table height - h mean of the variable water table height - h m variable water table height at the mid point - h m mean of the variable water table height at the mid point - K hydraulic conductivity - L half spacing between the ditches - m 0 initial water table height at the mid point - N Uniform rate of recharge - S specific yield - t time of observation - x distance measured from the ditch boundary - (4/SL)(NK)1/2 - (L/4)(N/K)1/2 - dummy integral variable  相似文献   
19.
Thus it may be summarised that work hardening behaviour of the alloy superni 263 can not be analysed using the simple power law equation. The work hardening behaviour is satisfactorily analysed using the modified power law equation (Ludwigson equation). There is systematic variation in the different work hardening parameters K1, n1, K2, n2 and C with the period of ageing at 800 °C. The drastic lowering of the parameters n1 and eup, from ageing even for a short duration, suggests that this material should be formed in fully solution treated condition and any precipitation of γ′ must be avoided for good formability.  相似文献   
20.
Metallurgical and Materials Transactions A - The design of high entropy alloys (HEAs) can be accelerated using machine learning (ML) algorithms. In the current study, the design parameter’s...  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