全文获取类型
收费全文 | 2051篇 |
免费 | 45篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 17篇 |
综合类 | 2篇 |
化学工业 | 410篇 |
金属工艺 | 20篇 |
机械仪表 | 30篇 |
建筑科学 | 69篇 |
矿业工程 | 16篇 |
能源动力 | 26篇 |
轻工业 | 132篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 147篇 |
一般工业技术 | 281篇 |
冶金工业 | 706篇 |
原子能技术 | 29篇 |
自动化技术 | 211篇 |
出版年
2021年 | 23篇 |
2019年 | 18篇 |
2018年 | 26篇 |
2016年 | 22篇 |
2014年 | 19篇 |
2013年 | 109篇 |
2012年 | 45篇 |
2011年 | 88篇 |
2010年 | 47篇 |
2009年 | 34篇 |
2008年 | 62篇 |
2007年 | 76篇 |
2006年 | 60篇 |
2005年 | 58篇 |
2004年 | 35篇 |
2003年 | 38篇 |
2002年 | 41篇 |
2001年 | 28篇 |
2000年 | 41篇 |
1999年 | 25篇 |
1998年 | 80篇 |
1997年 | 58篇 |
1996年 | 50篇 |
1995年 | 46篇 |
1994年 | 37篇 |
1993年 | 57篇 |
1992年 | 37篇 |
1991年 | 19篇 |
1990年 | 33篇 |
1989年 | 42篇 |
1988年 | 34篇 |
1987年 | 38篇 |
1986年 | 38篇 |
1985年 | 30篇 |
1984年 | 43篇 |
1983年 | 39篇 |
1982年 | 35篇 |
1981年 | 37篇 |
1980年 | 27篇 |
1979年 | 26篇 |
1978年 | 41篇 |
1977年 | 32篇 |
1976年 | 45篇 |
1975年 | 32篇 |
1974年 | 24篇 |
1973年 | 18篇 |
1972年 | 19篇 |
1970年 | 21篇 |
1969年 | 15篇 |
1964年 | 17篇 |
排序方式: 共有2110条查询结果,搜索用时 27 毫秒
51.
Hemant J. Desai Daniel O. Acheampong Robert Hudson Richard Lacey Claire Stanley Helen Turner 《Journal of Energetic Materials》2017,35(1):109-124
The synthesis of a novel heterocyclic–telechelic polymer, α,ω-oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infrared spectroscopy (IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo, and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitrato-functionalized polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solvent N,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favored and allows internal back-biting to the nearest carbon bearing the nitrato group, intrinsically in an SN2(i) reaction, leading to α,ω-oxetanyl functionalization. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g., acidic) or radiative (e.g., ultraviolet) curing methods without the use of high temperatures, usually below 100°C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ring closure and synthesis of heterocycles. 相似文献
52.
This paper begins by identifying the growth in female-headed households in Australia. Despite this increase, it is argued that females still lag males in terms of home ownership rates (HORs) with women in Australia facing similar ownership challenges as those experienced in the UK and the USA. In seeking to establish any dynamic change, the study analyses female home ownership rates in Australia for two points in time, 1998 and 2008. Logit models are used to predict HORs. The results indicate that factors such as household type, income and source of income have an impact on rates of ownership. The paper concludes that female-headed households in Australia show an increasing propensity to purchase which match, or even exceed, those of male-headed households. 相似文献
53.
Duc‐The Ngo Roberto Scipioni Søren Bredmose Simonsen Peter Stanley Jørgensen Søren Højgaard Jensen 《国际能源研究杂志》2016,40(14):2022-2032
LiFePO4‐based cathodes suffer from various degradation mechanisms, which influences the battery performance. In this paper, morphological and structural degradation phenomena in laboratory cathodes made of LiFePO4 mixed with carbon black (CB) in a 1 mol/L LiPF6 in EC : DMC (1:1 by weight) electrolyte are investigated by transmission electron microscopy at various preparation, assembling, storage, and cycling stages. High‐resolution transmission electron microscopy imaging shows that continuous SEI layers are formed on the LiFePO4 particles and that both storage and cycling affect the formation. Additionally, loss of CB crystallinity, CB aggregation, and agglomeration is observed. Charge–discharge curves and impedance spectra measured during cycling confirm that these degradation mechanisms reduce the cathode conductivity and capacity. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
54.
Dora Siva Prasad Nitla Stanley Ebenezer Chintada Shoba 《Transactions of the Indian Institute of Metals》2017,70(10):2601-2607
Nickel electroplating was applied to A356.2 aluminum alloy and its composites for improving its corrosion resistance. The corrosion resistance of the A356.2 and composites reinforced with rice husk ash particulates was evaluated by potentio-dynamic polarization tests in aerated 3.5% NaCl solution. Composites were fabricated by using the liquid state processing technique. Scanning electron microscopy, energy dispersive spectroscopy, techniques were used for surface analysis of the coatings before the corrosion tests and optical microscope was used to study the surface morphology of the uncoated and coated specimens after polarization tests. Results demonstrated that the nickel coated specimens exhibited higher corrosion resistance than the uncoated specimens. However, it was noticed that there was no significant change in the corrosion resistance for the nickel plated composites. 相似文献
55.
M. Berkan Sesen Michael D. Peake Rene Banares-Alcantara Donald Tse Timor Kadir Roz Stanley Fergus Gleeson Michael Brady 《Journal of the Royal Society Interface》2014,11(98)
Multidisciplinary team (MDT) meetings are becoming the model of care for cancer patients worldwide. While MDTs have improved the quality of cancer care, the meetings impose substantial time pressure on the members, who generally attend several such MDTs. We describe Lung Cancer Assistant (LCA), a clinical decision support (CDS) prototype designed to assist the experts in the treatment selection decisions in the lung cancer MDTs. A novel feature of LCA is its ability to provide rule-based and probabilistic decision support within a single platform. The guideline-based CDS is based on clinical guideline rules, while the probabilistic CDS is based on a Bayesian network trained on the English Lung Cancer Audit Database (LUCADA). We assess rule-based and probabilistic recommendations based on their concordances with the treatments recorded in LUCADA. Our results reveal that the guideline rule-based recommendations perform well in simulating the recorded treatments with exact and partial concordance rates of 0.57 and 0.79, respectively. On the other hand, the exact and partial concordance rates achieved with probabilistic results are relatively poorer with 0.27 and 0.76. However, probabilistic decision support fulfils a complementary role in providing accurate survival estimations. Compared to recorded treatments, both CDS approaches promote higher resection rates and multimodality treatments. 相似文献
56.
This paper is a review of different methods used to reduce the effect of strain gradients in experimental models with 3D embedded strain gauged transducers. A detailed analysis of various methods used in relation to research carried out on a prosthetic hip implant is investigated. The methods to reduce these gradient effects detail the importance of the selection of the most suitable 3D transducer pattern and establishing the locations on the model where strain gradients are least problematic. It is also shown that the use of large‐scale models helps minimise the effect a gradient may have on data. Another way of avoiding strain gradients is to use axisymmetric models and embed the gauges at the same radius in the model but at a different angular orientation from the central axis. The strain gradient across the 3D embedded strain gauge transducer can be reduced using the methods described here so that significant errors in the final tensor do not materialise. 相似文献
57.
Joanna Kałużna-Czaplińska Paulina Gątarek Salvatore Chirumbolo Max Stanley Chartrand Geir Bjørklund 《Critical reviews in food science and nutrition》2019,59(1):72-88
Tryptophan (Trp) is an amino acid and an essential component of the human diet. It plays a crucial role in many metabolic functions. Clinicians can use Trp levels in the course of diagnosing various metabolic disorders and the symptoms associated with those diseases. Furthermore, supplementation with this amino acid is considered in the treatment of depression and sleep disorders, mainly due to the Trp relationship with the synthesis of serotonin (5-HT) and melatonin. It is also used in helping to resolve cognitive disorders, anxiety, or neurodegenerative diseases. Reduced secretion of serotonin is associated with autism spectrum disorder, obesity, anorexia and bulimia nervosa, and other diseases presenting peripherals symptoms. The literature strongly suggests that Trp has a significant role in the correct functionality of the brain-gut axis and immunology. This information leads to the consideration of Trp as an essential dietary component due to its role in the serotonin pathway. A reduced availability of Trp in diet and nutraceutical supplementation should be considered with greater concern than one might expect. This paper constitutes a review of the more salient aspects gleaned from the current knowledge base about the role of Trp in diseases, associated nutritional disorders, and food science, in general. 相似文献
58.
Stanley L. Sclove 《技术计量学》2013,55(2):391-403
The problem of choosing between the models Y = α + βX and log Y = α + βX is considered. The maximum likelihood method of Box and Cox is compared with the method of using correlation coefficients to make the choice between the two models. The methods are applied to some data from the field of metallurgy. Operating characteristics of the two methods are estimated by simulation. Over a wide range of parameters there is not much difference between the two methods, although there are parameter values for which the correlation method appears markedly inferior to the likelihood method. The likelihood method seems preferable in that it is based on a probability model; this enables the statistician to make a confidence statement about the choice of model. 相似文献
59.
We propose a fast algorithm to approximate the optimal transport distance. The main idea is to add a Fisher information regularization into the dynamical setting of the problem, originated by Benamou and Brenier. The regularized problem is shown to be smooth and strictly convex, thus many classical fast algorithms are available. In this paper, we adopt Newton’s method, which converges to the minimizer with a quadratic rate. Several numerical examples are provided. 相似文献
60.