全文获取类型
收费全文 | 1455篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 65篇 |
金属工艺 | 5篇 |
机械仪表 | 12篇 |
建筑科学 | 35篇 |
矿业工程 | 6篇 |
能源动力 | 18篇 |
轻工业 | 32篇 |
水利工程 | 4篇 |
石油天然气 | 3篇 |
无线电 | 35篇 |
一般工业技术 | 64篇 |
冶金工业 | 1144篇 |
原子能技术 | 6篇 |
自动化技术 | 39篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 31篇 |
2012年 | 11篇 |
2011年 | 10篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 35篇 |
1998年 | 330篇 |
1997年 | 198篇 |
1996年 | 137篇 |
1995年 | 65篇 |
1994年 | 75篇 |
1993年 | 67篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 40篇 |
1976年 | 81篇 |
1974年 | 2篇 |
1960年 | 2篇 |
1957年 | 2篇 |
1920年 | 2篇 |
排序方式: 共有1470条查询结果,搜索用时 15 毫秒
51.
Field and pot trials were conducted to determine optimum management practices for usingLeucaena leucocephala (Lam. de Wit) leaves as a N source for crop production. Field trials with maize showed no benefit from split application of leucaena leaves or from application of fresh as opposed to dried material. Field trials also failed to show any difference between incorporation as opposed to surface application of leucaena leaves. This may be attributed to the low nitrogen response observed. Pot trials however, showed that soil incorporation of leucaena leaves was more effective than surface application in increasing plant dry weight.Leucaena leaves were not as effective as inorganic N in increasing maize grain yield (field trials) or dry matter production (pot trial). Unlike inorganic N, leucaena leaves had a significant residual effect on the succeeding maize crop. In decomposition studies, buried leucaena leaves decomposed more quickly than surface-applied leaves, and fresh leaves decomposed more rapidly than dried leaves. 相似文献
52.
53.
An enterprise modelling CASE tool and data schema requirements for the selection of software support
This paper describes a prototype CASE tool which has been implemented to support the selection of software applications. It is argued that information structures are invariably linked to the operation of the enterprise and can, therefore, be used as a powerful basis both for the suitability assessment and selection of candidate software applications. A structured methodology for the modelling of the enterprise operation and development of information requirements is first outlined to establish the application domain of the CASE tool. The functionality of the CASE tool is subsequently described, showing how aspects of the enterprise are captured in terms of organization, functionality, resource and information. It will be demonstrated how the information structures, captured by the CASE tool, are subsequently developed into a schema and used for the evaluation of a suitable software application. 相似文献
54.
In vitro evaluation of spray‐dried chitosan microspheres crosslinked with pyromellitic dianhydride for oral colon‐specific delivery of protein drugs
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chitosan microspheres have been prepared using a spray‐drying method, and crosslinked with pyromellitic dianhydride. The chemical structure of the modified chitosan was characterized by FTIR spectroscopy and solid state 13C NMR analysis. The particle size and morphology of the crosslinked chitosan were investigated. These microspheres were evaluated for colon‐specific delivery of bovine serum albumin (BSA) as a model protein drug. The results indicate that the drug was released as follows: 37.1 ± 2.8% after 2 h in SGF, 73.1 ± 4.8% after 8 h (2 h in SGF+ 6 h in SIF), and 80.9 ± 4.1% after 12 h in SCF. The effect of β‐glucosidase on the drug release was also examined. The encapsulation efficiency was decreased from 88.4 ± 3.1% to 62.8 ± 2.9%, with increasing BSA concentration. Loading capacity was significantly increased from 6.3 ± 0.3% to 41.8 ± 4.1% by increasing the initial BSA concentration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40514. 相似文献
55.
Jason Iles Raminta Zmuidinaite Christoph Sadee Anna Gardiner Jonathan Lacey Stephen Harding Jernej Ule Debra Roblett Jonathan Heeney Helen Baxendale Ray K. Iles 《International journal of molecular sciences》2022,23(8)
The immune response to SARS-CoV-2 infection requires antibody recognition of the spike protein. In a study designed to examine the molecular features of anti-spike and anti-nucleocapsid antibodies, patient plasma proteins binding to pre-fusion stabilised complete spike and nucleocapsid proteins were isolated and analysed by matrix-assisted laser desorption ionisation–time of flight (MALDI-ToF) mass spectrometry. Amongst the immunoglobulins, a high affinity for human serum albumin was evident in the anti-spike preparations. Careful mass comparison revealed the preferential capture of advanced glycation end product (AGE) forms of glycated human serum albumin by the pre-fusion spike protein. The ability of bacteria and viruses to surround themselves with serum proteins is a recognised immune evasion and pathogenic process. The preference of SARS-CoV-2 for AGE forms of glycated serum albumin may in part explain the severity and pathology of acute respiratory distress and the bias towards the elderly and those with (pre)diabetic and atherosclerotic/metabolic disease. 相似文献
56.
57.
Protecting against corner impacts: sensitivities discovered during a rail cask impact limiter design
D. C. Harding D. Garrido. Quevedo 《Packaging, Transport, Storage and Security of Radioactive Material》2014,25(1):38-46
Type B packages for the transportation of radioactive materials must remain ‘essentially leak tight’ under severe regulatory accident conditions, defined in the US Nuclear Regulatory Commission’s 10 CFR 71·73 and the International Atomic Energy Agency’s TS-R-1. The 9-m free drop test requirement onto an unyielding surface is performed in an orientation ‘for which maximum damage is expected’. Analytical techniques are used to evaluate various possible impact orientations before testing, and historically these maximal damage orientations have been side, slap-down, end, and centre-of-gravity over corner. Other orientations are rarely considered. Sandia National Laboratories (SNL) was asked by Equipos Nucleares SA (ENSA) to design, analyse, and test an impact limiter system for a newly designed rail cask. During the conceptual design process, SNL performed due diligence and evaluated a wide spectrum of possible impact orientations, in order to assure that peak cask body acceleration design goals were not exceeded. However, design of the impact limiter, including not only crush strength of constituent materials (which can be orientation and temperature dependent), but also the shape of the impact limiter, greatly affects peak acceleration response during 9-m drops in various orientations. Although many impact limiter design shapes resemble truncated right circular cylinders attached to each end of the cask, some tend to round the outer corners or truncate those corners with conical sections. SNL’s original conceptual design followed a similar theme, intending to use polyurethane foam or aluminium honeycomb within a bevelled corner shaped cylindrical shell. Detailed finite element analyses indicated excellent impact resistance at regulatory cold temperatures in the stereotypically tested side, slap-down, end, and CGOC impact orientations. Shortly before proceeding to engineering design, a rarely-considered impact orientation of 45° from horizontal indicated that cask body acceleration levels jumped unexpectedly, exceeding the design goal due to insufficient crushable material protecting the sharp corner of the cask. A complete re-design of the impact limiter was necessary, and the lessons learned from this experience could have implications for future impact limiter designs, and possibly existing designs that may not have considered this atypical impact orientation during the design process. 相似文献
58.
J. Benziger L. Cadonati F. Calaprice M. Chen A. Corsi F. Dalnoki-Veress R. Fernholz R. Ford C. Galbiati A. Goretti E. Harding Aldo Ianni Andrea Ianni S. Kidner M. Leung F. Loeser K. McCarty D. McKinsey A. Nelson A. Pocar C. Salvo D. Schimizzi T. Shutt A. Sonnenschein 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2009,608(3):464-474
The system for controlled filling of the nested flexible scintillator containment vessels in the Borexino solar neutrino detector is described. The design and operation principles of pressure and shape monitoring systems are presented for gas filling, gas displacement by water, and water displacement by scintillator. System specifications for safety against overstressing the flexible nylon vessels are defined as well as leak-tightness and cleanliness requirements. The fluid-filling system was a major engineering challenge for the Borexino detector. 相似文献
59.
Cobalt ferrite (CoFe2O4) was synthesized using sol-gel techniques from cobalt nitrate: iron nitrate: polyvinyl alcohol (PVA) gel in a ratio of 1:2:12. Variations in the amount of PVA in water (5 %, 10 % and 15 %) influenced the crystallite size and phases of the ferrite products, which in turn controlled their magnetic properties. X-ray diffraction studies indicated single phase CoFe2O4 with larger crystallite size and with the hysteresis loops displaying an increase in both coercive field and squareness as the PVA content was increased. Differential scanning calorimetry (DSC) showed that desorption of water and combustion of excess gel were clearly observed in CoFe2O4 prepared from 10 % and 15 % PVA in water. In the case of 5 % PVA in water, two other ratios of cobalt nitrate: iron nitrate: PVA solution were also tested and it was found that the 1:2:10 ratio led to the smallest coercive field and squareness. 相似文献
60.
Simon Harding Julian F. Miller Wolfgang Banzhaf 《Genetic Programming and Evolvable Machines》2010,11(3-4):397-439
Self-modifying Cartesian Genetic Programming (SMCGP) is a general purpose, graph-based, developmental form of Genetic Programming founded on Cartesian Genetic Programming. In addition to the usual computational functions, it includes functions that can modify the program encoded in the genotype. This means that programs can be iterated to produce an infinite sequence of programs (phenotypes) from a single evolved genotype. It also allows programs to acquire more inputs and produce more outputs during this iteration. We discuss how SMCGP can be used and the results obtained in several different problem domains, including digital circuits, generation of patterns and sequences, and mathematical problems. We find that SMCGP can efficiently solve all the problems studied. In addition, we prove mathematically that evolved programs can provide general solutions to a number of problems: n-input even-parity, n-input adder, and sequence approximation to π. 相似文献