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   5819篇
  免费   280篇
  国内免费   5篇
电工技术   50篇
综合类   21篇
化学工业   1748篇
金属工艺   114篇
机械仪表   119篇
建筑科学   272篇
矿业工程   16篇
能源动力   183篇
轻工业   380篇
水利工程   34篇
石油天然气   11篇
无线电   359篇
一般工业技术   1153篇
冶金工业   738篇
原子能技术   41篇
自动化技术   865篇
  2023年   61篇
  2022年   138篇
  2021年   194篇
  2020年   100篇
  2019年   114篇
  2018年   150篇
  2017年   137篇
  2016年   162篇
  2015年   152篇
  2014年   222篇
  2013年   341篇
  2012年   325篇
  2011年   388篇
  2010年   295篇
  2009年   252篇
  2008年   275篇
  2007年   269篇
  2006年   198篇
  2005年   171篇
  2004年   168篇
  2003年   132篇
  2002年   131篇
  2001年   96篇
  2000年   88篇
  1999年   93篇
  1998年   120篇
  1997年   108篇
  1996年   74篇
  1995年   74篇
  1994年   62篇
  1993年   48篇
  1992年   60篇
  1991年   56篇
  1990年   60篇
  1989年   65篇
  1988年   38篇
  1987年   40篇
  1985年   35篇
  1983年   40篇
  1982年   34篇
  1981年   35篇
  1980年   35篇
  1979年   30篇
  1978年   39篇
  1977年   36篇
  1976年   46篇
  1975年   39篇
  1974年   42篇
  1973年   39篇
  1970年   28篇
排序方式: 共有6104条查询结果,搜索用时 31 毫秒
71.
A simple method for the characterisation of fabric softness using a conventional tensile tester and a special measurement device has been developed. The method is demonstrated to be especially useful in detecting changes in softness of a given substrate due to different treatments. The results obtained, particularly hysteresis at 75% of the maximum extension, provide a good correlation with subjective ranking for samples that are subjectively distinguishable; they also differentiate well between samples which seem subjectively indistinguishable. Screening tests were carried out, mainly on wool fabrics, to find the effect of different treatments such as oxidative (alkaline and acidic) and reductive (Blankit IN) bleaching, dyeing with acid and a 1:2 metal complex, chrome and (mono and bi)reactive dyes, the effect of the antisetting agent Basolan AS (BASF) and of crosslinking with Irgasol HTW (CGY) on fabric softness.  相似文献   
72.
Sodium Aluminium Silicates - Properties and Application Sodium aluminium silicates in amorphous and crystalline form are used since many years in various technical processes. The crystalline sodium aluminium silicates, e. g. zeolites, belong to the group of structured silicates and are known for their reversible water uptake and alkaline earth exchange properties. Recently, sodium aluminium silicates have gained considerable importance since their cation exchanging ability can be utilized in washing agents for the removal of undesirable hardness of water. Thus, the polyphosphates used in washing agents can possibly be substituted. Zeolites can be supplied to the detergent industry in the form of powder or suspension. Production of the powder by spray drying does not involve special problems. Incorporation of the powder into the slurry of the detergent appears to be an anachronism from the viewpoint of energy saving. Optimization work on suspensions of zeolite yielded stable products with 45 to 48% zeolite content. The theory of critical particle concentration was applied in this work.  相似文献   
73.
74.
Virtualization is the cornerstone of the developing third-party compute industry, allowing cloud providers to instantiate multiple virtual machines (VMs) on a single set of physical resources. Customers utilize cloud resources alongside unknown and untrusted parties, creating the co-resident threat—unless perfect isolation is provided by the virtual hypervisor, there exists the possibility for unauthorized access to sensitive customer information through the exploitation of covert side channels. This paper presents co-resident watermarking, a traffic analysis attack that allows a malicious co-resident VM to inject a watermark signature into the network flow of a target instance. This watermark can be used to exfiltrate and broadcast co-residency data from the physical machine, compromising isolation without reliance on internal side channels. As a result, our approach is difficult to defend against without costly underutilization of the physical machine. We evaluate co-resident watermarkingunder a large variety of conditions, system loads and hardware configurations, from a local laboratory environment to production cloud environments (Futuregrid and the University of Oregon’s ACISS). We demonstrate the ability to initiate a covert channel of 4 bits per second, and we can confirm co-residency with a target VM instance in $<$ 10 s. We also show that passive load measurement of the target and subsequent behavior profiling is possible with this attack. We go on to consider the detectability of co-resident watermarking, extending our scheme to create a subtler watermarking attack by imitating legitimate cloud customer behavior. Our investigation demonstrates the need for the careful design of hardware to be used in the cloud.  相似文献   
75.
The dependence of the critical concentration of the ternary system polymer-polymer-solvent on the molecular weight can be expressed by the relation where cc is the critical concentration, M? the appropriate average of the molecular weight of both polymers; A and cc∞ are constants for the given system. The possibility of determining the molecular weight of one of the polymers from the value cc and the molecular weight of the known polymer with the aid of equation (1) is discussed.  相似文献   
76.
A theoretical approach to the kinetics of the thermal decomposition of molten thermoplastic polyurethane elastomers, under conditions of thermoplastic processing, is described. On the basis of these considerations, the thermal decomposition in different instruments (melt index analyser and measuring extruder) can be described quantitatively and the various results can be compared. As a result, identical conditions of decomposition of the melt can be defined accurately, thus opening up the possibility of combining experimental values from different instruments. The fundamental kinetic equation obtained for the kinetics of the thermal decomposition of thermoplastic polyurethanes describes the decomposition reaction and the reverse reaction (formation reaction) – which is dependent on the system of measurement and processing – as a function of the molar mass (end‐group concentration) of the original product, determined from the velocity constants for the decomposition reaction and back reaction. The consideration of the limiting value for t → ∞ is in agreement with the equilibrium constant. Consequently, the development of physical characteristic functions of thermoplastic polyurethane elastomers – independent of the system of measurement – is possible.

Experimental values and calculated curves for the thermal decomposition of PUR‐Et in a melt index analyser.  相似文献   

77.
Production-integrated environmental protection – Utilization of residues . Chemical plants as well as coal-fired powerstations utilize chemical reactions in order to produce materials or energy. Most of these reactions additionally produce gaseous, liquid, or solid residues. It is the main objective of production-integrated environmental protection to use these residues as suitable feedstocks in order to reduce environmental pollution and lower the consumption of raw materials. Several examples from the BASF Group will show how, by crossing the borders of the respective plant, reasonable solutions for material, or at least energetic, utilization of residues can be achieved. As a result of permanent efforts in production-integrated environmental protection over many years and despite increasing outputs the emissions of the chemical industry have been continuously reduced.  相似文献   
78.
Summary: This paper describes a step on the ambitious aim to “design” application properties of ldPE by first simulating the detailed molecular structure of a high‐pressure tubular reactor product. The reactor of a certain configuration produces under well‐defined operating conditions. The next step is to correlate the structure with the application properties. Finally, the sequence will be reversed in order to deduce the operating conditions, which lead to the desired product quality. Two‐dimensional distributions, in molecular weight and branching frequency, as well a two compartment models with a core and a shell stream were simulated and compared with experimental results. Therefore, CFD simulations were carried out to discretize the reaction medium. Samples were taken from both pilot and commercial plants. The TREF‐SEC analytical method was successfully applied in order to measure the microscopic structure of the material. The tremendous numerical problems were solved with the help of the software PREDICI .

Detailed MWD for a pilot scale reactor product.  相似文献   

79.
A new model is presented which can describe quantitatively the small angle neutron scattering from montmorillonite-type clay dispersions and polymer-clay nanocomposites. The model is shown to be able to describe well the data from a series of dilute montmorillonite in water dispersions in which the deuterium content of the water phase is varied. The fits combined with information from other techniques suggest strongly that H-D exchange occurs in the montmorillonite-water dispersions. Deviations from Q−2 behaviour often observed experimentally for clay dispersions are convincingly explained by the presence of a small proportion of tactoids.  相似文献   
80.
Summary: Non‐Newtonian fluid behavior has significant influence on quantities in chemical engineering like power input, mixing time, heat transfer etc. In the laminar flow region, the concept of effective viscosity by Metzner and Otto is well established. In the transition region between laminar and turbulent flow, the existing concepts use three and even more empirical parameters to determine the specific power input. Here, a unified and general but simple approach is introduced to calculate the power input for shear thinning fluids over the whole flow region using just one empirical parameter. The Metzner‐Otto relation is obtained as a limiting case for the laminar region. The empirical parameter of the new approach is related to the Metzner‐Otto constant. The concept is validated for eight different stirrer systems. Mixing time and maximum shear rate and heat transfer can also be calculated using this approach. The new concept presented should also be applicable for other apparatuses, e.g., static mixers.

Comparison of experimental data and a curve calculated according to the new method (solid line).  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