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   153篇
  免费   2篇
  国内免费   1篇
电工技术   1篇
化学工业   20篇
金属工艺   2篇
机械仪表   1篇
建筑科学   1篇
能源动力   3篇
轻工业   23篇
水利工程   1篇
石油天然气   8篇
无线电   6篇
一般工业技术   17篇
冶金工业   38篇
自动化技术   35篇
  2023年   1篇
  2020年   1篇
  2019年   3篇
  2018年   5篇
  2017年   3篇
  2016年   4篇
  2015年   1篇
  2014年   5篇
  2013年   19篇
  2012年   4篇
  2011年   10篇
  2010年   2篇
  2009年   5篇
  2008年   6篇
  2007年   6篇
  2006年   3篇
  2005年   3篇
  2004年   4篇
  2003年   4篇
  2002年   5篇
  2001年   2篇
  2000年   3篇
  1999年   4篇
  1998年   1篇
  1997年   4篇
  1996年   1篇
  1995年   4篇
  1994年   6篇
  1992年   6篇
  1991年   3篇
  1990年   7篇
  1989年   1篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1984年   2篇
  1982年   1篇
  1981年   2篇
  1980年   2篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1972年   2篇
  1961年   1篇
  1940年   1篇
排序方式: 共有156条查询结果,搜索用时 31 毫秒
1.
The sugar content was determined of 19 cultivars of swede (Brassica napus ssp rapifera L) grown in rows 50 and 75 cm apart. Sugar concentration ranged from 54.3 to 78.7 g kg?1 fresh weight and was positively correlated with dry matter content which ranged from 90.4 to 138.7 g kg?1 fresh weight. The average concentration of fructose, glucose and sucrose in the dry matter was 225.0, 328.4 and 34.5 g kg?1 DM, respectively. The high-dry-matter cultivars tended to have less fructose and more sucrose than the low-dry-matter ones, but total sugar concentration in the dry matter was not associated with dry-matter content. Row width had little effect on sugar content compared with the differences between cultivars. The implications for the feeding value of swedes are discussed.  相似文献   
2.
Fat-tailed dunnarts (Sminthopsis crassicaudata) were trained on visual discrimination learning-set, reversal-set, and spatial delayed-alternation tasks. The learning set involved 36 2-way black-and-white pattern discriminations and 5 probe reversals. Ten reversals of a black-and-white pattern discrimination were followed by 5 novel tasks. Spatial alternation was tested at delays up to 20 s. Learning-set and reversal-set formation, including 1-trial learning and spontaneous transfer from learning set to reversals and vice versa, was found. Learning-set-experienced dunnarts showed no retention of previously learned tasks 1 week after testing but demonstrated consistently high Trial 2 performance, indicating the retention of a response strategy. Delayed-alternation tasks were learned up to 10-s delays. These results provide the first evidence of a visually guided "win-stay, lose-shift" strategy in a marsupial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
3.
Samples consisting of the whole above-ground part of the oilseed rape plant (Brassica napus L), were taken every 2 weeks from before stem extension to maturity. The plants were separated into vegetative tissue, floral tissue, pods and seeds (when these components appeared), and the individual glucosinolates present were quantified by high performance liquid chromatography. A high glucosinolate variety (Rafal) and a low glucosinolate variety (Cobra) were compared. The effect of sulphur (32 kg ha?1 elemental sulphur applied at the beginning of stem extension) on the various parts of the plant was investigated. Total glucosinolate concentration in all plant parts was higher in Rafal than in Cobra. Glucosinolate concentration in the vegetation declined over time, most noticeably when the flowers and seeds were produced, and glucosinolate concentration of the pods also fell as that of the seeds rose. It is suggested that there may have been some redistribution of glucosinolates or glucosinolate precursors within the plant as maturity approached. Changes occurred in the proportions that individual glucosinolates contributed to the total glucosinolate content, and this may be relevant to plant/pathogen relationships. Sulphur application increased the glucosinolate concentration of the vegetative tissue by mid April and also increased the glucosinolate concentration of the flowers. It is suggested that this could affect the plant's resistance to disease.  相似文献   
4.
The current ASTM (D5304) procedure for determining storage stability involves rather drastic conditions, namely, 16 hours at 90°C and under 100 psig of oxygen. These mandated test conditions give rise to the question, “Does the reaction conditions induce chemical instability, or is it an accurate measure of the true instability process?” Several organo-sulfur functional groups are known to be present in petroleum derived fuels. Thiophenes, benzothiophenes, sulfides, disulfides, and trace amounts of thiols are the organo-sulfur compounds most prevalent. The reaction of organo-sulfur compounds under the ASTM reaction conditions have not been investigated. The purpose of the present research is to determine if the ASTM reaction conditions induce a reaction in an otherwise stable fuel matrix.  相似文献   
5.
This prospective study investigated the urodynamics of the urinary bladder prior to renal transplantation in 57 patients and related this to graft function and transplantation outcome. The study demonstrated a clear deterioration in the pretransplant urodynamic characteristics in all subgroups, with male patients in the hemodialysis group (HD) showing a more substantial decline: 1st sensation volume (ml) in male HD patients = 112 (120) vs. 171 (173) in male CAPD patients, P < 0.05; and corresponding average flow rate for same groups 3 (3) ml/sec vs. 5 (5) ml/sec, P < 0.05. Figures are median (interquartile range). We have identified a subgroup of patients with a small bladder capacity (less than 100 ml) who have a reduced graft survival (55% vs. 92% for bladders larger than 100 ml at 2 years) apparently unrelated to immunological processes.  相似文献   
6.
The reactions that lead to long-term storage instability of fuels are not fully understood. Various reports in the literature link particular fuels with specific reactions, usually oxidation or free radical processes. Trace quantities of metals are present in all processed fuels. The metal source can be naturally occurring or present from fuel handling. The usual case is to look at the reaction of the metal or metal ion with molecular oxygen or other active oxygen species such as hydroperoxides. This article reports on the reaction of a nitrogen heterocycle, indole. We propose a mechanism that shows that catalytic amounts of nickel can produce compounds of higher molecular weight and increased polarity.  相似文献   
7.
1. Paracetamol is increasingly involved in self-poisoning in the United Kingdom and remains a common cause of fatal poisoning. 2. To document the epidemiology and early management of paracetamol poisoning data were collected on consecutive patients with suspected paracetamol poisoning presenting to 6 hospitals in the North East of England over 12 weeks in 1994. 3. There were 400 presentations (attendance rate 1.14/10(3) population/yr) involving 343 persons (45% male). Paracetamol concentrations at 4 h correlated weakly with reported paracetamol dose (R = 0.49, P < 0.0001) and were similar comparing those treated and not treated by gastric decontamination. 4. In 38 (9%) cases paracetamol concentrations were above the appropriate nomogram treatment line, including 3% and 20% of patients who reported ingesting less than and more than 12 g respectively. In 21 patients acetylcysteine treatment was deferred until admission to the ward, the mean delay involved was 2.8 h. 5. One patient died, from arrhythmias caused by co-ingested dothiepin. 6. Paracetamol poisoning is common. Most cases do not have potentially toxic plasma paracetamol concentrations, but those who do often present late and antidotal treatment may be delayed inappropriately.  相似文献   
8.
The authors examined the ability of domestic dogs to use human body cues (gestures) and equivalent-sized nonhuman cues to find hidden food in an object choice paradigm. In Experiment 1 the authors addressed the importance of the human element of the cue, and the effects of size, topography, and familiarity on dogs' success in using cues. Experiment 2 further explored the role of the human as cue-giver, and the impact of a change in the experimenter's attentional state during cue presentation. This included a systematic test of the role inanimate tokens play as cues apart from human placement. Our results indicate that dogs are more sensitive to human cues than equivalent nonhuman cues, and that the size of the cue is a critical element in determining dogs' success in following it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
A rapid procedure is described for determining quartz in refractory clays by fusion in potassium bisulfate and subsequently by dissolving precipitated silica with a hot caustic solution. Data are included on the quartz content of several clays.  相似文献   
10.
Differences in performance were evaluated between binaural fittings of the Oticon MultiFocus (MF) and ReSound BT2-E on 25 hearing-impaired subjects across two sites. Subjects were initially fit using each manufacturer's algorithm and adjustments were made at 1 week based on subjects' responses to diary questions. Performance was assessed after a 4- to 6-week trial period with each hearing aid set using the Speech Perception in Noise (SPIN) test administered at 50, 65, and 80 dB SPL, the Abbreviated Profile of Hearing Aid Benefit (APHAB) questionnaire, loudness judgments of female connected discourse at 65 and 80 dB SPL, and an overall preference selection. The MF yielded significantly better SPIN scores at 50 and 65 dB SPL, while the BT2-E yielded a significantly better score at 80 dB SPL. No statistically significant differences were found in the APHAB benefit scores between the hearing aid sets, but both sets were significantly better than the subjects' own hearing aids on three of the four subscales. The MF produced slightly higher mean loudness judgments at both input levels than the BT2-E. Finally, 12 subjects preferred the BT2-E, 10 subjects preferred the MF, and three subjects stated no preference. The results are discussed in terms of audiogram effects on preference and effects of differences in signal processing approaches between the devices.  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