全文获取类型
收费全文 | 651篇 |
免费 | 42篇 |
专业分类
电工技术 | 5篇 |
综合类 | 2篇 |
化学工业 | 189篇 |
金属工艺 | 18篇 |
机械仪表 | 10篇 |
建筑科学 | 49篇 |
矿业工程 | 2篇 |
能源动力 | 17篇 |
轻工业 | 38篇 |
水利工程 | 2篇 |
无线电 | 52篇 |
一般工业技术 | 133篇 |
冶金工业 | 33篇 |
原子能技术 | 6篇 |
自动化技术 | 137篇 |
出版年
2023年 | 15篇 |
2022年 | 18篇 |
2021年 | 20篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 16篇 |
2016年 | 28篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 32篇 |
2012年 | 33篇 |
2011年 | 43篇 |
2010年 | 45篇 |
2009年 | 43篇 |
2008年 | 38篇 |
2007年 | 43篇 |
2006年 | 14篇 |
2005年 | 25篇 |
2004年 | 25篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1966年 | 3篇 |
1964年 | 1篇 |
排序方式: 共有693条查询结果,搜索用时 15 毫秒
651.
652.
Growth of Deposits on Pipes in a Field of Flow. The deposition of ash particles on the heat pipes of steam generators represents an energy and safety problem. A deterministic single-particle model was used to simulate this deposit formation. The numeric solution of the equation of motion gives the distribution of the impact points of the particles on the pipe surface. A particle mass balance allows calculation of the deposit formation δ (φ, t) on a pipe in space and time. Even if only a simple adhesion model is used, the calculated shape of the deposit can approach real deposit shapes. The effect of the sticking probability on deposit shape and formation time is shown. Numeric and analytical studies indicate the existence of stable limiting forms of the deposit. Thus, pipe forms can be calculated which allow only low levels of deposition and erosion. The model can be applied to particle-fluid flows around other contours. 相似文献
653.
654.
Explores recent developments in involuntary civil commitment and the legal and psychosocial process whereby persons alleged to be mentally ill and dangerous are involuntarily hospitalized. Highlighted are current trends toward cooperation among lawyers and mental health professionals and toward an avoidance of formal procedures in commitment proceedings. It is concluded that psychologists need to assume a greater role in this process. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
655.
We introduce graphical learning algorithms and use them to produce bounds on error deviance for unstable learning algorithms
which possess a partial form of stability. As an application we obtain error deviance bounds for support vector machines (SVMs)
with variable offset parameter.
Editor: Avrim Blum 相似文献
656.
Ingo Steinbach 《JOM Journal of the Minerals, Metals and Materials Society》2013,65(9):1096-1102
“Solidification” is a branch of pattern formation in theoretical physics. “Phase-field” is an applied tool in engineering. This strange combination of basic and applied research is reviewed against its historical background: a story of failure and success. The main achievements in both fields are highlighted, and future perspectives are briefly discussed. 相似文献
657.
Schwerdtle T Hamann I Jahnke G Walter I Richter C Parsons JL Dianov GL Hartwig A 《Molecular nutrition & food research》2007,51(2):201-210
Copper is an essential trace element involved, among other functions, in enzymatic antioxidative defense systems. However, nonprotein bound copper ions have been shown to generate reactive oxygen species. To gain insight into the discrepancy between the protective properties of copper on the one hand and its toxicity on the other hand, we examined the genotoxic effects of CuSO(4) in cultured human cells. Here we report that copper, at cytotoxic concentrations, induces oxidative DNA base modifications and DNA strand breaks. However, at lower noncytotoxic concentrations, copper inhibits the repair of oxidative DNA damage induced by visible light. As a first mechanistic hint, inhibition of H(2)O(2)-induced poly(ADP-ribosyl)ation was identified in cultured cells and further experiments demonstrated a strong inhibition of the activity of isolated poly(ADP-ribose)polymerase-1 (PARP-1) by copper. Bioavailability studies of copper showed a dose-dependent uptake in cells and pointed out the relevance of the applied concentrations. Taken together, the results indicate that copper, under conditions of either disturbed homeostasis or overload due to high exposure, exerts defined genotoxic effects. Hence, a balance needs to be maintained to ensure sufficient uptake and to prevent overload. 相似文献
658.
Ingo Leya Rolf Michel 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(21):2487-2503
We determined neutron excitation functions from the respective reaction thresholds up to 1.6 GeV for almost 100 target-product combinations relevant for cosmochemical, geochemical, and technological applications. We started with thick target production rates that have been obtained by irradiating iron and stone spheres with protons having energies between 600 MeV and 1.6 GeV. From the particle spectra of primary protons, secondary protons, and secondary neutrons, and the usually well known cross sections for the proton-induced reactions we calculated the production rates only due to protons. By subtracting these data from the measured total production rates we obtained production rates only due to secondary neutrons. With the modelled neutron spectra, guess functions calculated using nuclear model codes, and sophisticated energy-dependent deconvolution procedures we were able to determine almost 100 neutron excitation functions with their uncertainties. With the thus obtained neutron cross sections we are able to describe the experimental production rates in the thick target experiments, meteorites, the lunar surface, and terrestrial surface samples usually within the uncertainties, i.e., to within 10-15%. The adjusted neutron cross sections (a posteriori) are compared to results from the theoretical nuclear model codes INCL4.5/ABLA07 and TALYS. The TALYS code usually describes the a posteriori data reasonably well, i.e., mostly within a factor of a few. The quality of the INCL4.5 + ABLA07 predictions depends on the reaction type and increases with increasing number of ejectiles, i.e., increasing target-product mass difference. The neutron cross section database, though successful in quantifying production rates in terrestrial and extraterrestrial matter, presents by no means a final step and experiments with quasi-monoenergetic neutrons are needed. 相似文献
659.
Kotyczka C Boettler U Lang R Stiebitz H Bytof G Lantz I Hofmann T Marko D Somoza V 《Molecular nutrition & food research》2011,55(10):1582-1586
Recent results from prospective cohort studies have shown that moderate coffee consumption is associated with a reduced risk for diabetes mellitus type II or Alzheimer's disease. Since reactive oxygen species (ROS) are believed to be involved in the pathogenesis of these diseases, antioxidants in coffee might contribute to this risk reduction. We aimed at elucidating whether a dark roast coffee beverage (CB) rich in N‐methylpyridinium ions (NMP: 785 μmol/L) and low in chlorogenic acids (CGA: 523 μmol/L) has stronger antioxidant effects on human erythrocytes than a CB prepared from a light roast with opposite proportions (CGA: 4538 μmol/L; NMP: 56 μmol/L). Following a 2‐wk wash out period, 500 mL of the respective CB was administered to 30 subjects daily for 4‐wk. Blood and spot urine samples were collected at the beginning and at the end of each intervention. Intake of the dark roast CB most effectively improved the antioxidant status of erythrocytes: superoxide dismutase and glutathione peroxidase activity decreased by 5.8 and 15%, respectively, whereas tocopherol and total glutathione concentrations increased by 41 and 14%, respectively. Furthermore, administration of the NMP‐rich CB led to a significant body weight reduction in pre‐obese subjects, whereas the CGA‐rich CB did not. 相似文献
660.
Luis M. Molina Sungsik Lee Kristian Sell Giovanni Barcaro Alessandro Fortunelli Byeongdu Lee Soenke Seifert Randall E. Winans Jeffrey W. Elam Michael J. Pellin Ingo Barke Viola von Oeynhausen Yu Lei Randall J. Meyer Julio A. Alonso Arantxa Fraile Rodríguez Armin Kleibert Suzanne Giorgio Claude R. Henry Karl-Heinz Meiwes-Broer Stefan Vajda 《Catalysis Today》2011,160(1):965