全文获取类型
收费全文 | 1293篇 |
免费 | 33篇 |
专业分类
电工技术 | 16篇 |
化学工业 | 138篇 |
金属工艺 | 27篇 |
机械仪表 | 16篇 |
建筑科学 | 55篇 |
矿业工程 | 15篇 |
能源动力 | 21篇 |
轻工业 | 139篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 78篇 |
一般工业技术 | 163篇 |
冶金工业 | 448篇 |
原子能技术 | 20篇 |
自动化技术 | 180篇 |
出版年
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 25篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 49篇 |
2012年 | 24篇 |
2011年 | 53篇 |
2010年 | 38篇 |
2009年 | 30篇 |
2008年 | 34篇 |
2007年 | 37篇 |
2006年 | 48篇 |
2005年 | 38篇 |
2004年 | 34篇 |
2003年 | 27篇 |
2002年 | 31篇 |
2001年 | 21篇 |
2000年 | 11篇 |
1999年 | 34篇 |
1998年 | 118篇 |
1997年 | 79篇 |
1996年 | 62篇 |
1995年 | 29篇 |
1994年 | 33篇 |
1993年 | 30篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 16篇 |
1987年 | 10篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 19篇 |
1982年 | 18篇 |
1981年 | 16篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1977年 | 19篇 |
1976年 | 29篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1972年 | 10篇 |
1971年 | 8篇 |
1970年 | 11篇 |
排序方式: 共有1326条查询结果,搜索用时 0 毫秒
1.
Intraseptal scopolamine has differential effects on Pavlovian eye blink and heart rate conditioning.
Evaluated the effects of intraseptal scopolamine hydrobromide (40 μg) injections on Pavlovian (classical) conditioning, with tones used as the CS and a periorbital electric shock train as the UCS, using New Zealand albino rabbits. Eyeblink (EB) and heart rate (HTR) CRs were concomitantly recorded. Although injections of scopolamine into the medial septum impaired the acquisition of the Pavlovian conditioned eyelid reflex, these injections enhanced the magnitude of accompanying Pavlovian conditioned HTR decelerations. However, scopolamine applied to the lateral septal area had no effect on EB conditioning, relative to the vehicle; like medial injections, scopolamine also enhanced the magnitude of the accompanying HTR decelerations. Results are compatible with those of previous investigations indicating that medial septal dysfunction impairs somatomotor conditioning but leaves autonomic conditioning intact and that septal dysfunction produces a parasympathetic bias of the cardiovascular system. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
Design and practical implementation of multifrequency RF front ends using direct RF sampling 总被引:1,自引:0,他引:1
Psiaki M.L. Powell S.P. Hee Jung Kintner P.M. 《Microwave Theory and Techniques》2005,53(10):3082-3089
The use of direct RF sampling has been explored as a means of designing multifrequency RF front ends. Such front ends will be useful to multifrequency RF applications such as global navigation satellite system receivers that use global positioning system (GPS) L1, L2, and L5 signals and Galileo signals. The design of a practical multifrequency direct RF sampling front end is dependent on having an analog-to-digital converter whose input bandwidth accommodates the highest carrier frequency and whose maximum sampling frequency is more than twice the cumulative bandwidth about the multiple carrier signals. The principle of direct RF sampling is used to alias all frequency bands of interest onto portions of the Nyquist bandwidth that do not overlap. This paper presents a new algorithm that finds the minimum sampling frequency that avoids overlap. This design approach requires a multifrequency bandpass filter for the frequency bands of interest. A prototype front end has been designed, built, and tested. It receives a GPS coarse/acquisition code at the L1 frequency and GPS antispoofing precision code at both L1 and L2. Dual-frequency signals with received carrier-to-noise ratios in excess of 52 dB-Hz have been acquired and tracked using this system. 相似文献
3.
The Lambda Library (LL) adds a form of lambda functions to C++, which are common in functional programming languages. The LL is implemented as a template library using standard C++; thus no language extensions or preprocessing is required. The LL consists of a rich set of tools for defining unnamed functions. In particular these unnamed functions work seamlessly with the generic algorithms in the C++ Standard Library. The LL offers significant improvements, in terms of generality and ease of use, compared to the current tools in the C++ Standard Library. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
JL Banyer S Goldwurm L Cullen B van der Griend A Zournazi DJ Smit LW Powell EC Jazwinska 《Canadian Metallurgical Quarterly》1998,9(3):235-239
We have examined acetaminophen (paracetamol) dosing for outpatient management of posttonsillectomy pain in children. Forty children, 5-15 years of age, undergoing tonsillectomy and their parents were randomly assigned to use a scheduled administration of acetaminophen in weight appropriate doses, 60 mg.kg-1.24h-1 orally, 90 mg.kg-1.24h-1 rectally, or to use acetaminophen 'as needed' according to present standards (control group). Postoperative pain was assessed by the child using the poker chip tool for the first three days after discharge. The prevalence of pain amongst all the children was high. The second day after discharge 22%-64% of the children in the study group and 36%-73% of the children in the control group rated severe pain. Recommended dose ranges of acetaminophen do not provide sufficient pain relief in children following tonsillectomy. Further studies are required to determine, whether higher doses of acetaminophen or analgesics with different analgesic properties will lead to improved analgesia in children following tonsillectomy. 相似文献
5.
Professional software engineering continues to face problems that involve large-scale (complex) software systems development. Such efforts typically require team collaboration over months, possibly years. Once implemented, the system must be maintained for sometimes decades. This development and maintenance life cycle requires not only technical knowledge and skills in software development, but also the knowledge and skills associated with software process. We believe the traditional computer science curriculum fails to consider this spectrum of needs. We also believe, however, that software engineering must use certain elements of the core knowledge and skills taught by computer scientists as its foundation. We describe lessons learned from the 10-year collaboration between Monmouth University and the Software Engineering Center of the US Army's CECOM (Communications Electronics Command). The center recruits electrical engineering and computer science graduates from academic institutions in the geographic regions surrounding its various installations to be part of its intern program; Monmouth University, in turn, incorporates the demands of the intern program in its Master of Science in software engineering curriculum 相似文献
6.
M Pomerantz JR Denton GA Huitt JM Brown LA Powell MD Iseman 《Canadian Metallurgical Quarterly》1996,62(4):990-993
BACKGROUND: In a series of 229 patients infected with mycobacterial organisms, we noted a specific female phenotype that involves isolated infections of the middle lobe and lingula. METHODS: Thirteen patients were found to have infections of the middle lobe, lingula, or both. All of them were infected with Mycobacterium other then Mycobacterium tuberculosis, all were women, 12 of the 13 were slender, and most had variable combinations of skeletal abnormalities. All underwent resection of the middle lobe, lingula, or both. RESULTS: There were no operative deaths. Only 2 patients have had reactivation requiring additional antibiotic therapy. All patients have had a decreased number of pulmonary infections in the postoperative period. Anatomic findings at operation included a complete major fissure and at least a partially complete minor fissure with middle lobe resections or an elongated lingula. CONCLUSIONS: Mycobacterial infection of the middle lobe and lingula is primarily a disease of asthenic women and is often associated with skeletal abnormalities and complete fissures or an elongated lingula. We recommend that surgical intervention be performed early once the condition is identified. 相似文献
7.
Injury or infection of adult dental pulp often necessitates root canal therapy. This terminates dentin formation and subsequent tooth maturation. In addition, the synthetic materials currently utilized to replace lost tooth structure are not capable of completely replacing the function of the lost tissue, and often fail over time. This report describes a technique to engineer new pulp-like tissues utilizing cultured cells and synthetic extracellular matrices. Fibroblasts were obtained from human adult dental pulps and multiplied in culture. These cells were subsequently seeded onto synthetic matrices fabricated from fibers (approximately 15 microns in diameter) of polyglycolic acid (PGA). The pulp-derived fibroblasts adhered to the fibers, proliferated, and formed a new tissue over 60 days in culture with a cellularity similar to that of native pulp. These tissues may find application in the regeneration of oral tissues and may provide novel systems in which to study the biocompatibility of materials and chemicals used in dentistry. 相似文献
8.
Francis E. Powell Brian W. Brooks 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,57(1):65-71
Dimensionless material balance equations describing an uninhibited enzyme hydrolysis process in a semi-batch reactor (i.e. fed-batch reactor) are formulated; numerical solution of these equations provided concentration profiles of the enzyme-substrate complex by using published kinetic parameters. The unrestricted values obtained are compared with estimates based separately on the reaction steady state and stationary state assumptions. Results are discussed in terms of the enzyme/substrate inventory used and it is found that the reaction steady state is a satisfactory approximation only when this ratio is sufficiently small. The stationary state may be a better approximation at other values, particularly when enzyme is added to substrate or when an empty tank is being filled. Reaction yields from semi-batch and batch operations are compared. Processing takes longer in the semi-batch operations and complete conversions are only practical in this mode when enzyme is added to substrate. 相似文献
9.
10.