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   1361篇
  免费   60篇
  国内免费   8篇
电工技术   17篇
综合类   1篇
化学工业   488篇
金属工艺   39篇
机械仪表   42篇
建筑科学   26篇
矿业工程   2篇
能源动力   63篇
轻工业   90篇
水利工程   11篇
石油天然气   14篇
无线电   138篇
一般工业技术   218篇
冶金工业   89篇
原子能技术   8篇
自动化技术   183篇
  2024年   5篇
  2023年   23篇
  2022年   45篇
  2021年   59篇
  2020年   38篇
  2019年   38篇
  2018年   68篇
  2017年   57篇
  2016年   53篇
  2015年   41篇
  2014年   54篇
  2013年   101篇
  2012年   72篇
  2011年   65篇
  2010年   64篇
  2009年   60篇
  2008年   46篇
  2007年   41篇
  2006年   27篇
  2005年   28篇
  2004年   21篇
  2003年   20篇
  2002年   30篇
  2001年   13篇
  2000年   11篇
  1999年   21篇
  1998年   34篇
  1997年   21篇
  1996年   21篇
  1995年   13篇
  1994年   12篇
  1993年   20篇
  1992年   13篇
  1991年   11篇
  1990年   9篇
  1989年   15篇
  1988年   7篇
  1987年   9篇
  1986年   14篇
  1985年   11篇
  1984年   15篇
  1983年   11篇
  1982年   15篇
  1981年   11篇
  1980年   15篇
  1979年   6篇
  1978年   5篇
  1977年   6篇
  1976年   8篇
  1975年   5篇
排序方式: 共有1429条查询结果,搜索用时 31 毫秒
1.
2.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards.  相似文献   
3.
An ice slurry generation system was developed using direct contact heat transfer between water and the coolant, Fluroinert FC-84. The location of the coolant nozzle is an important design consideration to avoid clogging due to freezing of water. An ice fraction of up to about 40 percent was obtained with the nozzle located at the bottom of the ice slurry tank and the jet directed upwards into the water. Two simplified model were developed to extract the heat transfer coefficient between the coolant drops and the water. The first model requires as input the average drop diameter and the residence time while the second model uses the measured drop diameter distribution. The estimated heat transfer coefficients are much smaller than those computed using single-sphere correlations.  相似文献   
4.
A generalized equation was derived to calculate the melting temperatures of homopolymers and copolymers. The Gibbs‐Thomson equation for homopolymers and a modified application to copolymers were derived using the proposed equation. The melting temperature Tm0 in the Flory equation corresponds to the melting temperature TmC,∞ of copolymer crystals with stems of infinite length. Also, TmC,n*, the melting temperature for copolymer crystals with stems containing the maximum possible number of structural units, n*, should be used instead of Tm0 as the basis of supercooling in crystallization. The proposed equation shows good agreement with experimental data for α‐alkene‐ethylene homogeneous copolymers.  相似文献   
5.
6.
The influence of minor amounts of pro‐ and anti‐oxidants on the kinetics of the autoxidation of fat has been evaluated. The reaction rates of oxygen with the substrates were found to follow the same basic equation, hitherto established for pure substrates. There is evidence that the surface of the reaction vessel also acts as a reaction catalyst and its effect is proportional to the area of glass in contact with lipids. Oxidation is enhanced by trace metal ions as well as by surface‐active compounds (e.g. hydroperoxides and sterols). Antioxidants such as α‐tocopherol and butylated hydroxyanisole inhibit the oxidation by delaying the start of oxygen consumption (the induction period) while retarders like amino acids only decrease the rate of oxidation. Thus pro‐ and anti‐ oxidants affect either the start or the rate of oxygen consumption. The empirical formula dx/dt = k [O2] (1‐x/n) f′(t) was found applicable to the different stages of oxidation.  相似文献   
7.
A 2-year-old boy with Rotor syndrome was studied with Tc-99m N-(di-isopropylphenyl carbamoylmethyl) iminodiacetic acid (DIPA). In this patient, the liver was not visualized, and there was persistent visualization of the cardiac blood pool and along with prominent kidney excretion. It is concluded that Tc-99m DIPA cholescintigraphy may be helpful in the diagnosis of Rotor syndrome.  相似文献   
8.
The gene rafY from the plasmid pRSD2, which enables Escherichia coli to grow on raffinose, was transferred into expression plasmid pUSL77. The protein was expressed in the porin-deficient Escherichia coli strain KS26 and was isolated and purified to homogeneity. The pure protein was reconstituted into lipid bilayer membranes. It formed an ion-permeable channel with a single-channel conductance of 2.9 nS of the open state in 1 M KCl, which is approximately twice of that of the general diffusion pores OmpF and OmpC of E. coli outer membrane. At lower pH the channel exhibited rapid flickering between three substates of the open channel. The RafY channel appears to be wide and water filled and has a small selectivity for cations over anions. Although RafY is part of an uptake and fermentation system for raffinose it does not contain a binding site for carbohydrates. Our results suggest that RafY is a general diffusion pore with a diameter, larger than that of the general diffusion porins OmpF and OmpC, that allows the diffusion of high-molecular-mass carbohydrates through the outer membrane.  相似文献   
9.
Neural Computing and Applications - Cryptography often involves substituting (and converting) the secret information into dummy data so that it could reach the desired destination without leakage....  相似文献   
10.
Neural Computing and Applications - Emperor Penguin Optimizer (EPO) is a recently developed metaheuristic algorithm to solve general optimization problems. The main strength of EPO is twofold....  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