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   262篇
  免费   27篇
  国内免费   4篇
电工技术   3篇
综合类   1篇
化学工业   84篇
金属工艺   2篇
机械仪表   2篇
建筑科学   10篇
矿业工程   1篇
能源动力   5篇
轻工业   36篇
水利工程   1篇
石油天然气   1篇
无线电   22篇
一般工业技术   57篇
冶金工业   40篇
自动化技术   28篇
  2023年   2篇
  2022年   8篇
  2021年   15篇
  2020年   6篇
  2019年   7篇
  2018年   11篇
  2017年   16篇
  2016年   12篇
  2015年   8篇
  2014年   17篇
  2013年   19篇
  2012年   16篇
  2011年   20篇
  2010年   10篇
  2009年   9篇
  2008年   11篇
  2007年   12篇
  2006年   9篇
  2005年   5篇
  2004年   5篇
  2003年   4篇
  2002年   1篇
  2001年   6篇
  2000年   5篇
  1999年   7篇
  1998年   10篇
  1997年   8篇
  1996年   7篇
  1995年   4篇
  1993年   4篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1987年   3篇
  1986年   3篇
  1985年   4篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1976年   2篇
  1970年   1篇
排序方式: 共有293条查询结果,搜索用时 16 毫秒
91.
The effect of posture on phase III (alveolar nitrogen plateau) and phase IV (closing capacity) of the single-breath oxygen test was examined in 10 normal people. In part 1 of the study, subjects inspired and expired in the standing, supine, prone, and right lateral decubitus positions; there was no effect of posture on phase IV but slopes of phase III were higher when subjects were in the supine and lateral positions. In part 2, subjects inspired in the standing position and expired in one of the recumbent positions. Phase IV occurred infrequently except in the prone position (6 of 10 subj); slopes of phase III in part 2 were not consistently altered by changing posture. It is difficult to explain the failure of posture to alter phase IV solely on a model requiring a linear gradient of pleural pressure. The slope of phase III appears to depend more on the emptying patterns of small regions with widely varying volume-to-ventilation ratios than on gravity-dependent sequences of emptying. Finally, the data suggest a considerable similarity between the upright and prone positions in terms of lung filling and emptying.  相似文献   
92.
Factors that affect time overrun in the Nigerian construction industry have been studied, and the rank agreement factor for the professionals are architects∕engineers, 0.75; architects∕builders, 0.83; quantity surveyors∕engineers, 0.74; quantity surveyors∕builders, 0.79; and engineers∕builders, 0.69. Important findings are (1) the degree of occurrence of time overrun is high—between 80 and 90%; (2) relative contributions of the client, contractor, and others are 62, 32, and 6%, respectively; (3) time overrun is more pronounced in government/public sector projects (89%); and (4) time overrun occurs on all projects, irrespective of size.  相似文献   
93.
抗性淀粉的研究与分析   总被引:10,自引:1,他引:9  
抗性淀粉是摄食后不被小肠消化而能被大肠微生物群作用的那部分淀粉。已有关于食物中抗性淀粉测定的报道。本文综述了近来抗性淀粉研究进展以及相应的测定方法。本文所述的测定方法有较高的准确性和较好的重现性,能测定含量在1%以下的抗性淀粉。抗性淀粉对健康有潜在意义,以后将更注重这方面的研究。  相似文献   
94.
Ethical communication during crisis response is often assessed by external perceptions of the organization's intentions, rather than an assessment of the organization's communicative behaviors. This can easily lead researchers to draw editorial conclusions about an organization's ethics in crisis response rather than accurately describing its communicative behaviors. The case of BP's 2010 oil spill in the Gulf of Mexico provides a prime example for the importance of accurately assessing the ethical content of an organization's crisis response because the ethics of BP's response have been discussed in news and academic sources; yet little direct examination of the ethical content in BP's response has occurred. The findings have implications for communication ethics, social media engagement, and crisis communication more generally.  相似文献   
95.
Phthalonitrile polymers are known for their high thermal stability and good mechanical properties. However, their brittle nature limits their application as structural composites in many critical areas. The present study investigates the feasibility of toughening novolac–phthalonitrile (NPN) resin using chemically modified poly(ether ether ketone) (PEEK). A telechelic PEEK bearing a phthalonitrile end group (PEEKPN) was synthesized via nucleophilic substitution of nitrophthalonitrile with the corresponding phenol–telechelic poly(ether ether ketone) (PEEKOH). Different compositions of NPN and PEEKOH–PEEKPN blends with curing agent, i.e. diaminodiphenylsulfone, were investigated for their cure behaviour and mechanical properties of their carbon fabric composites. In NPN–PEEKOH blends, crosslinking of the phthalonitrile groups was facilitated by phenol‐mediated reactions resulting in the reduction of cure temperatures by around 130 °C with substantial improvement in thermal stability. Blending the resin with the thermoplastic enhanced the mechanical properties of the composites. The apparent flexural strength and impact strength of carbon fabric‐reinforced composites were improved by more than 200 and 150%, respectively, on incorporation of 20 wt% PEEKOH in the NPN matrix. However, higher concentration of PEEKOH had a detrimental effect on the properties. Substitution of phenol end groups by phthalonitrile moieties led to integration of the PEEK moieties with the NPN matrix. However, it was not as conducive as PEEKOH for improving the matrix properties. The better performance of PEEKOH is attributed to the formation of polar heterocyclic groups like isoindoline by way of the phenol–nitrile reaction. © 2014 Society of Chemical Industry  相似文献   
96.
97.
Fractionation of palm kernel oil (PKO) by short path distillation (SPD) at two feed flow rates (135 g/h and 195 g/h) and six distillation temperatures, TD,s (200, 210, 220, 230, 240 and 250 ℃) was investigated. Other distillation parameters, such as vacuum pressure (0.001 mbar), blade rotation speed (400 rpm) and temperature of the feed material (60 ℃) were kept constant. The fractionated products, known as residue and distillate, were analysed for physico-chemical properties including fatty acid composition (FAC), triacylglycerol (TAG) composition, slip melting point (SMP), thermal analysis by differential scanning calorimetry (DSC) and solid fat content (SFC). Product yield was measured as well. Crystallisation behaviour of PKO and the fractionated products were studied by measurement of isothermal crystallisation, Tc,. at 0, 5, 10, 15, 20 and 25 ℃. The distillates, collected at all fractionation temperatures, were enriched with caprylic, capric and lauric acids. These fractions were also concentrated with low molecular weight and C36 TAGs. Distillates obtained at higher TDis (230-250 ℃) exhibited higher in SMP and SFC. On the other hand, the residual oils collected at all fractionation temperatures contained higher amount of long-chain fatty acid and palmitic acid. These fractions were enriched with high molecular weight TAGs. Residues obtained at lower Tois (200-220 ℃) were low in SMP and comparable SFC with PKO. Changes in fatty acid and TAG composition resulted in different crystallisation behaviour of the fractions. Distillates collected at all fractionation temperatures crystallised in a sharper peak while residues obtained at higher T Dis (230-250 ℃) showed broader crystallisation peaks, as shown by the DSC thermograms.  相似文献   
98.
Spodosols in Florida exhibit a unique hydrology including a fluctuating water table that can often reach the surface horizon during the summer months. This paper evaluated the effects of fluctuating water table on P fluxes and availability in a typical Florida Spodosol. The study was conducted on an established bahiagrass (Paspalum notatum Flügge) pasture grown on a Smyrna sand (sandy, siliceous, hyperthermic Aeric Alaquods). Phosphorus fluxes were measured using suction cup lysimeters installed at depths of 15, 30, 60, 90, and 150 cm. The 15- and 30-cm deep lysimeters were located above the spodic (Bh) horizon, whereas the remaining lysimeters (60-, 90- and 150-cm) were below the Bh horizon. A pressure transducer was installed at the center of the experimental site to monitor changes in water table depth. Two anion exchange membranes (2 × 6 cm) were buried in each plot at a 15-cm depth to estimate in situ P availability. During the 2-year study, leachate P concentrations in the lysimeters above the Bh horizon increased as water tables rose in the months of August and September. Conversely, P concentration measured in the lysimeters below the Bh horizon remained relatively constant (0.02 mg L−1). Soil P availability also increased (from 3.2 μg cm−2 in June to 9.2 μg cm−2 in August) in response to rising water table. Results showed that the fluctuating water table conditions experienced during the summer months in Florida cause upward flux of P from the Bh horizon, which increased soil P availability and susceptibility to off-site transport.  相似文献   
99.
100.
Previous research has largely focused on the influence of experienced affect on decision making; however, other sources of affective information may also shape decisions. In two studies, we examine the interacting influences of affective information, state affect, and personality on temporal discounting rates (i.e., the tendency to choose small rewards today rather than larger rewards in the future). In Study 1, participants were primed with either positive or negative affect adjectives before making reward choices. In Study 2, participants underwent either a positive or negative affect induction before making reward choices. Results in both studies indicate that neuroticism interacts with state unpleasant affect and condition (i.e., positive or negative primes or induction) to predict discounting rates. Moreover, the nature of the interactions depends on the regulatory cues of the affective information available. These results suggest that irrelevant (i.e., primes) and stable (i.e., personality traits) sources of affective information also shape judgments and decision making. Thus, current affect levels are not the only source of affective information that guides individuals when making decisions. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  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