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排序方式: 共有408条查询结果,搜索用时 15 毫秒
71.
Fredrik Östlund Karolina Rzepiejewska‐Malyska Klaus Leifer Lucas M. Hale Yuye Tang Roberto Ballarini William W. Gerberich Johann Michler 《Advanced functional materials》2009,19(15):2439-2444
Robust nanostructures for future devices will depend increasingly on their reliability. While great strides have been achieved for precisely evaluating electronic, magnetic, photonic, elasticity and strength properties, the same levels for fracture resistance have been lacking. Additionally, one of the self‐limiting features of materials by computational design is the knowledge that the atomistic potential is an appropriate one. A key property in establishing both of these goals is an experimentally‐determined effective surface energy or the work per unit fracture area. The difficulty with this property, which depends on extended defects such as dislocations, is measuring it accurately at the sub‐micrometer scale. In this Full Paper the discovery of an interesting size effect in compression tests on silicon pillars with sub‐micrometer diameters is presented: in uniaxial compression tests, pillars having a diameter exceeding a critical value develop cracks, whereas smaller pillars show ductility comparable to that of metals. The critical diameter is between 310 and 400 nm. To explain this transition a model based on dislocation shielding is proposed. For the first time, a quantitative method for evaluating the fracture toughness of such nanostructures is developed. This leads to the ability to propose plausible mechanisms for dislocation‐mediated fracture behavior in such small volumes. 相似文献
72.
The dynamics of free radical polymerization of styrene and on-line control of temperature in a cooling jacketed batch polymerization
reactor is investigated. The benzoyl peroxide initiator is introduced into the reactor once at the beginning of the reaction
to obtain the desired monomer conversion and the desired average chain length in a minimum reaction time. The optimal constant
set temperature, which is generally realized in industrial applications, and the set profile are used as two different optimal
operating conditions. The temperature control of the polymerization reactor is achieved experimentally and theoretically.
The control of nonlinear systems has progressed considerably, and various nonlinear process model based control techniques
have appeared in the literature. The problem is how to tune the controller in order to obtain comparable closed loop responses.
Generic model control (GMC) is applied and the performance of the control results are compared with the previously published
control results. 相似文献
73.
Guldenmund F Hale A Goossens L Betten J Duijm NJ 《Journal of hazardous materials》2006,130(3):575-241
This paper describes the development of a management model to control barriers devised to prevent major hazard scenarios. Additionally, an audit technique is explained that assesses the quality of such a management system. The final purpose of the audit technique is to quantify those aspects of the management system that have a direct impact on the reliability and effectiveness of the barriers and, hence, the probability of the scenarios involved.
First, an outline of the management model is given and its elements are explained. Then, the development of the audit technique is described. Because the audit technique uses actual major hazard scenarios and barriers within these as its focus, the technique achieves a concreteness and clarity that many other techniques often lack. However, this strength is also its limitation, since the full safety management system is not covered with the technique. Finally, some preliminary experiences obtained from several test sites are compiled and discussed. 相似文献
74.
Variation in rubber chemistry and dynamic mechanical properties of the milking liner barrel with age
The milking liner is the interface between the milking machine and the cow. Liner properties important to milking performance were investigated for liners of different ages using discriminating tests rather than the normal, rubber-industry quality control-based tests. Large variations in the liner mechanical properties occurred depending on where the sample was taken; stiffness increased 4-fold 40 to 50 mm below the top of the liner. This was related to changes in the chemistry of the rubber created by absorption of milk-derived products (MDP) into the rubber and losses of formulation components, particularly 50% of the plasticizer and all of the antidegradent 40 to 50 mm below the top of the liner, with age and use. The presence of MDP leads to calcium and phosphate deposits on the inner surface of the liner barrel where the MDP was absorbed. The detailed liner properties can be used to explain the forces on the cow's teat and its reactions and effects on milk flow behavior, and to guide future liner development. 相似文献
75.
Engineering education is undergoing an assessment of its own. Organizations responsible for engineering education are looking at themselves in an attempt to improve their total quality as well as the quality of the programs they assess. The reasons for these changes include issues relating to cost, efficiency and quality of engineering education programs, and the increased demand for accountability by constituencies (state legislatures, students, employers). The ability to work in a group and to acquire and assimilate new knowledge effectively is another key requirement of graduate engineers and is difficult to assess. This article describes the national and local forces for more definitive outcome assessment and how we have responded to those forces. The article in particular describes how we have used senior design projects as an important part of undergraduate program assessment. 相似文献
76.
Rose Nathan S.; Myerson Joel; Roediger Henry L. III; Hale Sandra 《Canadian Metallurgical Quarterly》2010,36(2):471
Two experiments compared the effects of depth of processing on working memory (WM) and long-term memory (LTM) using a levels-of-processing (LOP) span task, a newly developed WM span procedure that involves processing to-be-remembered words based on their visual, phonological, or semantic characteristics. Depth of processing had minimal effect on WM tests, yet subsequent memory for the same items on delayed tests showed the typical benefits of semantic processing. Although the difference in LOP effects demonstrates a dissociation between WM and LTM, we also found that the retrieval practice provided by recalling words on the WM task benefited long-term retention, especially for words initially recalled from supraspan lists. The latter result is consistent with the hypothesis that WM span tasks involve retrieval from secondary memory, but the LOP dissociation suggests the processes engaged by WM and LTM tests may differ. Therefore, similarities and differences between WM and LTM depend on the extent to which retrieval from secondary memory is involved and whether there is a match (or mismatch) between initial processing and subsequent retrieval, consistent with transfer-appropriate-processing theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
TiO_2 nanotubes on Ti metal surface were prepared by the electrochemical anodization method. Then, nanosilver was deposited onto the nanotubes by the electroless dip coating and the anodization. The obtained TiO2 nanotubes were examined by using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, cyclic voltammetry, and UV–Vis. The electrochemical band gap(E_g~(CV)) of the nanosilver-coated TiO_2 nanotubes prepared by the anodization was found as 1.54 eV. Using the UV–Vis measurements, the optical band gap energy(E_g~(op).) was calculated as 1.51 eV for the Ag/TiO_2 nanotubes obtained by electroless dip coating. The electrical conductivity of the TiO_2 nanotubes also increased from 3.0 9 10-4 to 34.7 S/cm after nano Ag deposition by the anodization method.These Ag/TiO_2 nanotubes with low band gap and high electrical conductivity are desirable for the applications in electronics, Li-ion batteries, and solar cells. 相似文献
78.
This article presents an effort to collect operational and maintenance data on 240 power generation, power distribution and heating, ventilation, and air conditioning (HVAC) items, including gas turbine generators, diesel engine generators, electrical switchgear, cables, circuit breakers, boilers, piping, valves, pumps, motors, and chillers. 相似文献
79.
Kathleen Simis Mingzu Lei Amy Tsai Lu Krishnamohan C. V. Sharma Ron L. Hale Ryan Timmons 《Drug development and industrial pharmacy》2013,39(9):936-942
Application of the Staccato system to liquid drugs presents unique technological challenges. Liquids, such as nicotine, do not form physically stable films on vaporization substrates. We identified two thermally reversible zinc halides (ZnCl2 and ZnBr2) that complex with nicotine in a 1:2 mol ratio (zinc halide: nicotine) that can be coated as a solid film. Feasibility studies indicated that the chloride complex liberates a higher fraction of nicotine upon heating whereas the nicotine aerosol purity for both complexes was approximately 99%. Using a multidose Staccato device previously used in a Phase I clinical trial, we demonstrated that highly pure nicotine aerosol can be reliably generated from the chloride complex with the following qualities: aerosol purity approximately 99%, single emitted dose approximately 117 μg, particle fraction approximately 57%, and mean particle size approximately 0.8 μm. These results were supported by thermogravimetric analysis and differential scanning calorimetry. 相似文献
80.
Stephen H. Hale Hans J. Schlereth Stefan Bortnowski 《Energy Conversion and Management》1982,22(4):385-388
A 450 ft ‘site-built’ air collector was completed in February 1981 in Boston, Massachusetss. The collector uses the Airco/Guardian ‘Passive Solar Glass’ with a selective surface coating on the inner lite of the collector's double glazing. This paper discusses the issues and theory that led to the building of the collector and estimates performance for the system. Preliminary data taken in late winter indicates that the system will perform seasonally as predicted. 相似文献