全文获取类型
收费全文 | 219篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 17篇 |
金属工艺 | 5篇 |
机械仪表 | 9篇 |
建筑科学 | 3篇 |
矿业工程 | 1篇 |
能源动力 | 5篇 |
轻工业 | 45篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 22篇 |
一般工业技术 | 19篇 |
冶金工业 | 70篇 |
原子能技术 | 1篇 |
自动化技术 | 22篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 8篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1944年 | 1篇 |
排序方式: 共有225条查询结果,搜索用时 31 毫秒
21.
Rodney G. TeKrony Glen D. Sanders Billy Cummins 《Canadian Metallurgical Quarterly》2004,130(2):148-153
In the early days of the Reclamation Service, the criteria for irrigability of lands generally consisted of two elements: (1) is water available? and (2) can we get the water to the land? Within a few years, many of the early projects were experiencing reduced agricultural productivity and reduced ability to repay construction loans because the soils were becoming waterlogged and saline. By 1915, construction of subsurface drainage facilities had been initiated on several projects. However, at the time, subsurface drainage was more of an art than a science. Much of the world’s experience with agricultural drainage had been gained in humid areas which were quite different from arid areas. With no standards and limited knowledge of ground water movement, these early drainage efforts met with varying degrees of success. This paper summarizes the development of scientific methods to ensure successful application of drainage in a sustainable irrigated agriculture. Reclamation has introduced these methods to solve irrigated drainage problems at the international level. This paper will address the international experience, and how the same design and construction methods and procedures are now being used to design corrective drainage facilities for dams and other major structures and to support environmental enhancement programs. 相似文献
22.
目前,市场都期盼着中国大陆3G许可证能于2006年发放,随着WCDMA等3G技术的发展,一方面将推动3G手持终端的开发和推广;同时由于对带宽需求的显著提高,这也意味着对流量的管理需求也将大大提高,这也将推动对3G基站的投资并带来更多的高级服务供应商应用.杰尔系统认为2006年中国无线运营商将大幅推广赢利性应用和服务,以满足消费者的需要,为未来的竞争做好充分准备.新服务将包括实时音频和视频流、立体声音乐下载、个性化彩铃下载、互动游戏等,甚至包括广播电视功能. 相似文献
23.
JA Clements A Mukhtar K Verity M Pullar P McNeill J Cummins PJ Fuller 《Canadian Metallurgical Quarterly》1996,44(2):223-231
Somatostatin has been suggested to influence the somatotrophic axis outside the central nervous system, in reducing GH-induced IGF-I mRNA and IGF-I generation. This study aimed to determine whether such effects were mediated via the GH receptor (GHR). GH-deficient dwarf rats aged 45-47 days (n = 8 per group) received twice daily subcutaneous injections of octreotide (1 mg/kg) (group O), saline (group S), octreotide (1 mg/kg) plus bovine GH (0.25 mg/kg) (group OG), or bovine GH (0.25 mg/kg) plus saline (group G) for 10 days. Octreotide-treated animals had less weight gain compared with saline-treated animals, but not when GH cotreated (group OG vs G). Octreotide had an overall effect on decreasing length gain (P < 0.01). Serum IGF-I (ng/ml) was reduced by octreotide (group O 171 +/- 11, group S 239 +/- 20, P < 0.01; group OG 283 +/- 30, group G 362 +/- 10, P < 0.001), as was serum insulin (P < 0.001). A significant decrease in hepatic and muscle IGF-I mRNA expression was found as expected, yet this was not associated with decreased hepatic GHR expression. Rather, an increase in hepatic 125I-bovine GH specific binding was observed (P < 0.001) and, in GH-cotreated animals (OG), hepatic GHR and GH binding protein (GHBP) mRNA expression were also increased by octreotide by approximately 40%. In muscle, octreotide was associated with an approximately 30% decrease in GHBP mRNA and no effect on GHR mRNA. This study suggests that the suppressive effects of octreotide on IGF-I metabolism, at least in liver, are not mediated via down-regulation of GHR expression, but more likely by direct effects on IGF-I expression. 相似文献
24.
Hawkins Elizabeth H.; Cummins Lillian H.; Marlatt G. Alan 《Canadian Metallurgical Quarterly》2004,130(2):304
Substance abuse has had profoundly devastating effects on the health and well-being of American Indians and Alaska Natives. A wide variety of intervention methods has been used to prevent or stem the development of alcohol and drug problems in Indian youth, but there is little empirical research evaluating these efforts. This article is an overview of the published literature on substance use prevention among Indian adolescents, providing background epidemiological information, a review of programs developed specifically for Indian adolescents, and recommendations for the most promising prevention strategies currently in practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
MJ Schaeken JS Van der Hoeven CA Saxton D Cummins 《Canadian Metallurgical Quarterly》1996,23(5):465-470
The basal and depolarization-induced arginine-vasopressin (AVP) release from intact pituitaries of SHR and WKY rats was studied in vitro in a perfusion chamber. Differences associated to strain, sex and two age periods (pre-adult: 25-30 days of age; adult: 60-70 days of age) were assessed. The results show an enhanced AVP release in the adult male as well as female SHR compared to the WKY rat. The stimulated AVP release was also significantly higher in the preadult male SHR and indicated in preadult females SHR. No differences associated to strain in basal AVP release were detected at the age interval 25-30 days. The response to muscimol was increased in preadult female and male SHR rats compared to the WKY animals. It is concluded that the augmented depolarization-induced AVP release and sensitivity to muscimol in the SHR is not related to sex, and no apparent change in this pattern was associated to the transition between the juvenile and adult condition. 相似文献
26.
T.C. Simonen R.H. Bulmer F.H. Coensgen W.F. Cummins C. Gormezano B.C. Logan A.W. Molvik W.E. Nexsen W.C. Turner B.W. Stallard G.E. Vogtlin R.R. Vandervoort 《Journal of Nuclear Materials》1976
The control of first-wall surface conditions in the 2XIIB Magnetic Mirror Plasma Confinement experiment is described. Before each plasma shot, the first wall is covered with a freshly gettered titanium surface. Up to 5 MW of neutral beam power has been injected into 2XIIB, resulting in first-wall bombardment fluxes of 1017 atoms · cm?2 · s?1 of 13-keV mean energy deuterium atoms for several ms. The background gas flux is measured with a calibrated, 11-channel, fast-atom detector. Background gas levels are found to depend on surface conditions, injected beam current, and beam pulse duration. For our best operating conditions, an efective reflex coefficient of 0.3 can be inferred from the measurements. Experiments with long-duration and high-current beam injection are limited by charge exchange; however, experiments with shorter beam duration are not limited by first-wall surface conditions. We conclude that surface effects will be reduced further with smoother walls. 相似文献
27.
To better understand why sensory neurons express voltage-gated Na+ channel isoforms that are different from those expressed in other types of excitable cells, we compared the properties of the hNE sodium channel [a human homolog of PN1, which is selectively expressed in dorsal root ganglion (DRG) neurons] with that of the skeletal muscle Na+ channel (hSkM1) [both expressed in human embryonic kidney (HEK293) cells]. Although the voltage dependence of activation was similar, the inactivation properties were different. The V1/2 for steady-state inactivation was slightly more negative, and the rate of open-state inactivation was approximately 50% slower for hNE. However, the greatest difference was that closed-state inactivation and recovery from inactivation were up to fivefold slower for hNE than for hSkM1 channels. TTX-sensitive (TTX-S) currents in small DRG neurons also have slow closed-state inactivation, suggesting that hNE/PN1 contributes to this TTX-S current. Slow ramp depolarizations (0.25 mV/msec) elicited TTX-S persistent currents in cells expressing hNE channels, and in DRG neurons, but not in cells expressing hSkM1 channels. We propose that slow closed-state inactivation underlies these ramp currents. This conclusion is supported by data showing that divalent cations such as Cd2+ and Zn2+ (50-200 microM) slowed closed-state inactivation and also dramatically increased the ramp currents for DRG TTX-S currents and hNE channels but not for hSkM1 channels. The hNE and DRG TTX-S ramp currents activated near -65 mV and therefore could play an important role in boosting stimulus depolarizations in sensory neurons. These results suggest that differences in the kinetics of closed-state inactivation may confer distinct integrative properties on different Na+ channel isoforms. 相似文献
28.
No other successful nuclear method, besides bone scanning, has been reported in the literature for in vivo imaging of olfactory neuroblastoma. In this article, excellent uptake is reported by an In-111 labeled bleomycin complex (BLMC) in the ethmoid region of a histologically confirmed olfactory neuroblastoma. The uptake of BLMC was 0.7 x 10(-3)% ID/g at 48 hours after injection, and tumor-to-muscle and tumor-to-fat ratios were 6:1 and 11:1, respectively. The authors conclude that BLMC should be considered as a useful imaging agent, and the BLMC has potential as a radiochemotherapeutic agent against an olfactory neuroblastoma. 相似文献
29.
Notes that as yet no satisfactory explanation has been advanced to explain the mechanisms mediating the anatomical and biochemical brain changes induced by exposing animals to environments rich in sensory stimuli. It is hypothesized here that a fundamental mechanism is the arousal response, since alterations in arousal appear to be concomitants of all such environmentally induced changes. The properties of the arousal reaction are discussed in terms of their possible relationship to the neurological changes induced, and evidence is presented indicating that this mechanism may be common to several areas of environmental stimulation research which have previously been thought of as separate investigative fields. Several possible tests of the hypothesis are presented, and an underlying cellular response sequence transducing electrical into biosynthetic activity is discussed. (41/2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
RA McKay LL Cummins MJ Graham EA Lesnik SR Owens M Winniman NM Dean 《Canadian Metallurgical Quarterly》1996,24(3):411-417
We have previously described the characterization of a 20mer phosphorothioate oligodeoxynucleotide (ISIS 4189) which inhibits murine protein kinase C-alpha (PKC-alpha) gene expression, both in vitro and in vivo. In an effort to increase the antisense activity of this oligonucleotide, 2'-O-propyl modifications have been incorporated into the 5'- and 3'-ends of the oligonucleotide, with the eight central bases left as phosphorothioate oligodeoxynucleotides. Hybridization analysis demonstrated that these modifications increased affinity by approximately 8 and 6 degrees C per oligonucleotide for the phosphodiester (ISIS 7815) and phosphorothioate (ISIS 7817) respectively when hybridized to an RNA complement. In addition, 2'-O-propyl incorporation greatly enhanced the nuclease resistance of the oligonucleotides to snake venom phosphodiesterase or intracellular nucleases in vivo. The increase in affinity and nuclease stability of ISIS 7817 resulted in a 5-fold increase in the ability of the oligonucleotide to inhibit PKC-alpha gene expression in murine C127 cells, as compared with the parent phosphorothioate oligodeoxynucleotide. Thus an RNase H-dependent phosphorothioate oligodeoxynucleotide can be modified as a 2'-O-propyl 'chimeric' oligonucleotide to provide a significant increase in antisense activity in cell culture. 相似文献