全文获取类型
收费全文 | 1169篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 152篇 |
金属工艺 | 3篇 |
机械仪表 | 26篇 |
建筑科学 | 36篇 |
矿业工程 | 3篇 |
能源动力 | 12篇 |
轻工业 | 105篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 136篇 |
一般工业技术 | 190篇 |
冶金工业 | 371篇 |
原子能技术 | 8篇 |
自动化技术 | 126篇 |
出版年
2023年 | 5篇 |
2021年 | 11篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 52篇 |
2012年 | 21篇 |
2011年 | 30篇 |
2010年 | 25篇 |
2009年 | 19篇 |
2008年 | 33篇 |
2007年 | 37篇 |
2006年 | 34篇 |
2005年 | 30篇 |
2004年 | 41篇 |
2003年 | 38篇 |
2002年 | 21篇 |
2001年 | 33篇 |
2000年 | 37篇 |
1999年 | 41篇 |
1998年 | 95篇 |
1997年 | 70篇 |
1996年 | 45篇 |
1995年 | 35篇 |
1994年 | 24篇 |
1993年 | 41篇 |
1992年 | 29篇 |
1991年 | 13篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 21篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 19篇 |
1975年 | 6篇 |
1974年 | 9篇 |
1973年 | 5篇 |
1967年 | 4篇 |
排序方式: 共有1188条查询结果,搜索用时 0 毫秒
31.
Tristan F. Burns Kraft Barbara M. Schmidt G.G. Yousef Christopher T.G. Knight Muriel Cuendet Young-Hwa Kang John M. Pezzuto David S. Seigler Mary Ann Lila 《Journal of food science》2005,70(3):S159-S166
ABSTRACT: Wild lowbush blueberry fruit extract was fractionated using vacuum chromatography and analyzed for chemopreventive potential using bioassays that test the ability of compounds to inhibit the initiation, promotion, and progression stages of carcinogenesis. A fraction containing phytosterols was active against the initiation stage (quinone reductase assay). However, more polar compounds were inhibitors of later stages of carcinogenesis; a fraction containing flavan-3-ols and fractions containing mainly anthocyanins, phenolic acids, flavan-3-ols, and some proanthocyanidin dimers demonstrated activity against the promotion stage (cyclooxygenase and ornithine decarboxylase assays, respectively), and a proanthocyanidin-rich fraction demonstrated antiproliferation activity (inhibition of cancerous murine hepatocyte proliferation is associated with the progression stage). These results indicate that lowbush blueberries contain a range of compounds that have bioactivity against multiple stages of carcinogenesis, and different types of phenolic compounds are active at different stages. 相似文献
32.
CW Shuttleworth AJ Burns SM Ward WE O'Brien KM Sanders 《Canadian Metallurgical Quarterly》1995,68(4):1295-1304
Neurons that synthesize nitric oxide from arginine produce stoichiometric amounts of citrulline. We investigated whether nitric oxide-releasing enteric neurons have the capacity to recycle citrulline to arginine and thereby sustain nitrergic neurotransmission. Argininosuccinate synthetase-like immunoreactivity and argininosuccinate lyase-like immunoreactivity, enzymes capable of citrulline to arginine conversion, were both localized in discrete populations of myenteric and submucosal neurons in the canine proximal colon. Argininosuccinate synthetase-like immunoreactivity and argininosuccinate lyase-like immunoreactivity co-localized with neuronal beta-nicotinamide adenine dinucleotide phosphate diaphorase staining, a marker for nitric oxide synthase. The functional significance of argininosuccinate synthetase-like immunoreactivity and argininosuccinate lyase-like immunoreactivity was shown by testing the effects of exogenous citrulline on responses to enteric inhibitory nerve stimulation, which were assessed by measuring contractions, inhibitory junction potentials and electrical slow waves. As shown previously, arginine analogues (L-nitroarginine methyl ester or L-nitroarginine; 100 microM) inhibited nitric oxide-dependent responses, and excess L-arginine restored inhibitory responses. Citrulline alone (0.1-2 mM) had no effect on nitrergic transmission under control conditions, but in the presence of L-nitroarginine methyl ester or L-nitroarginine, citrulline (0.1-2 mM) restored nitrergic transmission in a concentration-dependent manner. Other neutral amino acids (L-serine, L-leucine) did not mimic the effects of citrulline. Taken together, these data suggest that enteric nitrergic neurons have the enzymatic apparatus and functional capability of recycling citrulline to arginine. 相似文献
33.
Anger may have greater effects on chronic pain severity than other negative emotions and may do so by increasing muscle tension near the site of injury (symptom-specific reactivity). For patients with chronic low back pain (CLBP), relevant muscles are lower paraspinals (LP). Ninety-four CLBP patients and 79 controls underwent anger and sadness recall interviews. EMG and cardiovascular activity were recorded. Patients exhibited greater LP tension increases during anger and slower recovery than controls. Only patients showed greater LP reactivity during anger than sadness. For both groups, trapezius reactivity during anger and sadness did not differ. LP reactivity to anger correlated with everyday pain severity for patients. Anger-induced symptom-specific LP reactivity may be linked to chronic pain aggravation among CLBP patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
34.
A simplified mathematical analysis is made of the motion of the latch as the needle passes down the stitch cam. Two practical cases are considered: (i) when the latch retains contact with the previously formed loop of yarn as it rises towards the needle head; and (ii) when the yarn moves with a stick–slip motion such that the latch loses contact with the yarn. It is shown that among possible methods for reducing latch impact are a reduction in latch mass, a reduction in the stitch-cam angle during the period when the latch is closed, and a reduction in the latch length; an improved latch design is also suggested. 相似文献
35.
36.
B. Elhweg I.W. Burns Y.M.J. Chew P.J. Martin A.B. Russell D.I. Wilson 《Food and Bioproducts Processing》2009,87(4):266-272
We have analysed sets of capillary rheometry data (0.3 s?1 ≤ γapp ≤ 360 s?1) for a commercial ice cream as it flowed from a freezer on an industrial flow line. Pressure drop measurements were used and particular attention was paid to viscous dissipation effects. A semi-analytical model presented by Bird in 1955 indicated that over one third of the data points were subject to local wall heating, which was consistent with available temperature measurements. The filtered data were used to construct a viscosity function which, when implemented in a detailed CFD simulation of the flow, predicted the observed flow curve behaviour. The results demonstrate that viscous dissipation can be significant in ice cream and that interpretation of this behaviour in terms of wall slip is erroneous. 相似文献
37.
S. E. Burns K. Reynolds W. Reeves M. Banach T. Brown K. Chalmers N. Cousins M. Etchells C. Hayton K. Jacobs A. Menon S. Siddique P. Too C. Ramsdale J. Watts P. Cain T. Von Werne J. Mills C. Curling H. Sirringhaus K. Amundson M. D. McCreary 《Journal of the Society for Information Display》2005,13(7):583-586
Abstract— A scalable manufacturing process for fabricating active‐matrix backplanes on low‐cost flexible substrates, a key enabler for electronic‐paper displays, is presented. This process is based on solution processing, ink‐jet printing, and laser patterning. A multilayer architecture is employed to enable high aperture ratio and array performance. These backplanes were combined with E Ink electrophoretic media to create high‐performance displays that have high contrast, are bistable, and can be flexed repeatedly to a radius of curvature of 5 mm. 相似文献
38.
Synchronously pumped optical parametric oscillation in periodically poled lithium niobate with 1-w average output power 总被引:1,自引:0,他引:1
We report on a rugged all-solid-state laser source of near-IR radiation in the range of 1461-1601 nm based on a high-power Nd:YVO(4) laser that is mode locked by a semiconductor saturable Bragg reflector as the pump source of a synchronously pumped optical parametric oscillator with a periodically poled lithium niobate crystal. The system produces 34-ps pulses with a high repetition rate of 235 MHz and an average output power of 1 W. The relatively long pulses lead to wide cavity detuning tolerances. The comparatively narrow spectral bandwidth of <15 GHz is suitable for applications such as pollutant detection. 相似文献
39.
40.
The aim of this cross-sectional study which took place in a hypertension clinic at a district general hospital in Denmark was to make a pragmatic definition of white coat hypertension. A total of 420 patients were referred consecutively from general practice with newly diagnosed untreated essential hypertension and 146 normal subjects were drawn at random from the Danish national register. The following measurements were taken: office blood pressure; 24-h ambulatory blood pressure (BP) monitoring; echocardiography with determination of left ventricular mass index and relative wall thickness; and early morning urine albumin/creatinine ratios. Four different cut-off levels were studied. An ambulatory daytime BP of 135.6/90.4 mm Hg was found to correspond to an office BP of 140/90 mm Hg in normal controls; used as a cut-off level in patients with newly diagnosed hypertension it separated 19% as white coat hypertensives. The end-organ involvement of these white coat hypertensives differed significantly from those with established hypertension but not from the normal controls. Lower cut-off levels were less efficient in this respect, as was the case when the systolic BP was not taken into account. In conclusion a pragmatic definition of white coat hypertension should--apart from well-established hypertensive office measurements--include a cut-off level close to 135/90 mm Hg ambulatory daytime BP. 相似文献