全文获取类型
收费全文 | 1871篇 |
免费 | 107篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 18篇 |
综合类 | 3篇 |
化学工业 | 448篇 |
金属工艺 | 40篇 |
机械仪表 | 46篇 |
建筑科学 | 46篇 |
矿业工程 | 4篇 |
能源动力 | 58篇 |
轻工业 | 367篇 |
水利工程 | 12篇 |
石油天然气 | 4篇 |
无线电 | 157篇 |
一般工业技术 | 296篇 |
冶金工业 | 187篇 |
原子能技术 | 14篇 |
自动化技术 | 281篇 |
出版年
2023年 | 16篇 |
2022年 | 36篇 |
2021年 | 59篇 |
2020年 | 42篇 |
2019年 | 31篇 |
2018年 | 60篇 |
2017年 | 64篇 |
2016年 | 72篇 |
2015年 | 54篇 |
2014年 | 73篇 |
2013年 | 130篇 |
2012年 | 119篇 |
2011年 | 117篇 |
2010年 | 93篇 |
2009年 | 87篇 |
2008年 | 100篇 |
2007年 | 85篇 |
2006年 | 76篇 |
2005年 | 45篇 |
2004年 | 36篇 |
2003年 | 61篇 |
2002年 | 53篇 |
2001年 | 34篇 |
2000年 | 30篇 |
1999年 | 28篇 |
1998年 | 65篇 |
1997年 | 55篇 |
1996年 | 28篇 |
1995年 | 28篇 |
1994年 | 16篇 |
1993年 | 25篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1966年 | 4篇 |
排序方式: 共有1981条查询结果,搜索用时 15 毫秒
141.
Denis Teixeira Franco Maí Correia Vasconcelos Lirida Naviner Jean-François Naviner 《Microelectronics Reliability》2008,48(8-9):1586-1591
As integrated circuits scale down into nanometer dimensions, a great reduction on the reliability of combinational blocks is expected. This way, the susceptibility of circuits to intermittent and transient faults is becoming a key parameter in the evaluation of logic circuits, and fast and accurate ways of reliability analysis must be developed. This paper presents a reliability analysis methodology based on signal probability, which is of straightforward application and can be easily integrated in the design flow. The proposed methodology computes circuit’s signal reliability as a function of its logical masking capabilities, concerning multiple simultaneous faults occurrence. 相似文献
142.
143.
Franco Preparata 《Calcolo》1966,3(1):113-126
A digital data acquisition system is analyzed under the traffic standpoint. This system receives a random stream of digital
messages, accumulates them in an electronic buffer storage and unloads them on a magnetic tape. The system is representable
as a single waiting line, the service mechanism of which is ruled by the characteristics of the cascaded functional blocks.
Queueing theory methods are applied to determine the queue length distribution under stationary conditions as a function of
the system parameters; this, conversely, provides some criteria for the selection of the values of the parameters, necessary
to achieve a given statistical behavior. The expected message loss due to temporary system saturation is also computed. 相似文献
144.
Francesco Fatone Paolo Battistoni David Bolzonella Paolo Pavan Franco Cecchia 《Desalination》2008,227(1-3):72
The alternating processes applied in membrane bioreactors for municipal wastewater treatment may be an attractive option to reduce the energy consumptions and optimize carbon and nitrogen removal. However, the knowledge of these systems is often based on empirical results so to discourage the plant operators for its adoption. This paper discusses and compares the empirical evidence coming from two different alternating membrane bioreactors, a demonstration and a full-scale one. The two plants treat two real municipal wastewaters, rather different for both C:N ratio and degree of biodegradability of the influent organics. Nine steady-state runs have been carried out in the demonstration plant, while a one whole year operation has been considered for the full-scale system. Combining the results of the two MBRs, it was found that the alternating process was able to adjust automatically and adequately the aeration of the biological reactor with a nitrogen loading rate in the range 0.05–0.18 kgN m−3 d−1 and C:N mass ratios greater than 5–6. As a result, the use of the available carbon source, with concern to the total nitrogen removal, was as low as 0.1 kg of total nitrogen removed per kg of total influent COD. Effluent total nitrogen met the standard for reuse with specific energy consumptions in the range 85–109 gTNremoved per kWhconsumed. Considering the usual loading conditions of the municipal wastewater treatment plants in Italy, membrane bioreactors operating alternating processes may be implemented to increase the nitrogen treatment capacity of existing plants and achieve the standards for reuse. 相似文献
145.
Stefano Bianco Mario Enorini Franco L. Fabbri Adriano Zallo Pier G. Rancoita 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,235(2):240-243
A multilayer solid state device which is both an active target and tracking detector is proposed for an electronic experiment investigating the so-called anomalons and studying their production mechanism, interaction cross-section and lifetime. The experimental method is based on triggering the reinteractions in two targets of heavy fragments, originated in a production target by a relativistic ion beam. This method greatly increases the sensitivity to the anomalon's effect when compared to other proposed electronic experiments. Solid state devices seem to provide a resolving technique for the study of these short-lived states among high-multiplicity final systems. 相似文献
146.
In this study the effects of CCK microinjections into the rostral or caudal nucleus accumbens (Acc) on locomotor activation derived from systemic amphetamine treatment were examined. It was found that CCK microinjections into the rostral Acc attenuated and CCK microinjections into the caudal Acc potentiated amphetamine-induced locomotor activity. Results indicate that rostral Acc CCK microinjections have dopamine agonistlike effects on amphetamine-induced locomotor activity. The relevance of the present findings to previous results regarding CCK–dopamine interactions is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
147.
Franco Brezzi Klaus-Jürgen Bathe Michel Fortin 《International journal for numerical methods in engineering》1989,28(8):1787-1801
We present in this paper a procedure to establish Reissner–Mindlin plate bending elements. The procedure is based on the idea to combine known results on the approximation of Stokes problems with known results on the approximation of elliptic problems. The proposed elements satisfy the mathematical conditions of stability and convergence, and some of them promise to provide efficient elements for practical solutions. 相似文献
148.
149.
Medical screws are a common mass-produced implantable medical component made of Titanium. To machine the threads of these types of components, thread whirling with carbide tools is typically used. However, tool wear and low cutting speed limit the productivity and increase the manufacturing cost of such medical parts. In this study, a direct motor driven thread whirling unit for an advanced Swiss-type CNC lathe was developed and it was used with advanced tool materials such as low binder content Cubic boron nitride (CBN) and Polycrystalline diamond (PCD) to find a cost-effective and more productive alternative to carbide tools. 相似文献
150.
Gamboa Delgado EM López Barbosa N Prada Gómez GE Franco Cadena JT Landínez Navarro A 《Archivos latinoamericanos de nutrición》2010,60(3):247-253
The objective of this study was to determine associated factors to the consumption of fruit and vegetables (FV) in the adult population of each socioeconomic status (SES) in Bucaramanga, Colombia. We conducted a cross-sectional in a sample of 317 people and we measured socio-demographic, economic and anthropometric variables and dietary factors related to the purchase and consumption of FV. We made a survey, a 24-Hour dietary recall and we did anthropometric measurements. Portion sizes were estimated with a standardized set of utensils and food-photography atlas. Frequencies, measures of central tendency and dispersion were established and Logistic Regression models were used for the bi and multivariate analysis. Average consumption of FV was 162.6 g/day (188.5 g in high SES and 145.7 g in low SES, p = 0.056). On average 2 servings per day of FV (2.3 servings in high SES and 1.5 in low SES, p = 0.055). The prevalence of adequate intake of FV (more than 5 servings / day) was 8.6% (8.9% in high SES and 8.4% in low SES, p = 0.896). The associated factor to consumption of FV was BMI > or =25 (OR: 0.31, CI (95%): 0.11-0.89, p = 0.030), adjusted for occupation, income, SES, and number of family members. FV consumption is low; excess weight is the only variable associated to no-consumption of five or more servings; causes: cost to the consumption of fruit and flavor in the case of vegetables. 相似文献