全文获取类型
收费全文 | 1712篇 |
免费 | 97篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 20篇 |
综合类 | 8篇 |
化学工业 | 674篇 |
金属工艺 | 67篇 |
机械仪表 | 25篇 |
建筑科学 | 45篇 |
矿业工程 | 5篇 |
能源动力 | 24篇 |
轻工业 | 310篇 |
水利工程 | 8篇 |
石油天然气 | 22篇 |
无线电 | 69篇 |
一般工业技术 | 260篇 |
冶金工业 | 125篇 |
原子能技术 | 18篇 |
自动化技术 | 132篇 |
出版年
2023年 | 26篇 |
2022年 | 137篇 |
2021年 | 193篇 |
2020年 | 42篇 |
2019年 | 51篇 |
2018年 | 64篇 |
2017年 | 49篇 |
2016年 | 55篇 |
2015年 | 50篇 |
2014年 | 75篇 |
2013年 | 99篇 |
2012年 | 80篇 |
2011年 | 93篇 |
2010年 | 76篇 |
2009年 | 78篇 |
2008年 | 81篇 |
2007年 | 52篇 |
2006年 | 39篇 |
2005年 | 29篇 |
2004年 | 13篇 |
2003年 | 24篇 |
2002年 | 21篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 7篇 |
1998年 | 25篇 |
1997年 | 23篇 |
1996年 | 16篇 |
1995年 | 23篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1984年 | 12篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1971年 | 6篇 |
1970年 | 9篇 |
1969年 | 7篇 |
排序方式: 共有1812条查询结果,搜索用时 15 毫秒
111.
Tracking uncooperative moving objects by means of radar is a complex task due to clutter and association problems in multi-target scenarios. An approach to solve this problem is probabilistic multiple hypothesis tracking (PMHT). This method combines classical track filtering with a likelihood ratio test for the estimation of the plot-to-track association. The basics of PMHT and similar algorithms have gained much attention recently. However, the efficient implementation of real world applications of this technique still represents a challenging task. Since a common requirement in this context is the reliable storage of track data in a database, an implementation of the tracker's calculation inside a database management system (DBMS) using SQL views is desirable. A naive implementation of PMHT using a commercial DBMS, however, usually leads to performance problems because of the high frequency of measurement updates. In this paper, we propose possible optimizations for solving these performance problems. Their usage leads to a dramatic run-time improvement in our sample case and makes the implementation of PMHT in a database context feasible. 相似文献
112.
A new analytical model was developed to estimate the degree of mutual influence of the links between the stations of Wi-Fi Mesh networks which use different channel access methods specified by the IEEE 802.11s standard, namely, contention-based channel access mechanism and the deterministic channel access mechanism based on the preliminary reservation of channel resources. The model was used to compare the efficiency of different backoff counting methods proposed in the paper for providing the interaction between two channel access methods. Additionally, the model was also used to analyze the effect of different techniques for arranging the time intervals reserved by means of the deterministic channel access mechanism on the performance of stations using contention-based channel access mechanism. 相似文献
113.
Carolina Tallon Monika Limacher George V. Franks 《Journal of the European Ceramic Society》2010,30(14):2819-2826
The effect of the nanometric-ranged particle size of the starting powder through a simple and well-established shaping method, slip casting, has been studied. Several alumina suspensions with the same viscosity (but different solid content suspensions) and different particle size (11, 44, 190 and 600 nm) were prepared and shaped into a dense body. The green and sintered densities ranged between 30–67% and 63–99% of the theoretical value, respectively. These values, together with the microstructure observations reveal the effect of the solid content of the suspensions and the characteristics of the ceramic powder, leading to the determination of an optimal particle size. Based on both processability (rheological behaviour) and microstructure (density and grain size) it has been determined that particles with sizes ranging 100–300 nm are the best for preparing concentrated suspensions with low viscosity and bodies with density close to the theoretical value when using conventional pressureless sintering densification. 相似文献
114.
The first cool-down of the EDIPO (European DIPOle) test facility is foreseen to take place in 2011 by means of the existing 1.2 kW cryoplant at EPFL-CRPP Villigen. In this work, the thermo-hydraulic analysis of the EDIPO cool-down is performed in order both to assess the its duration and to optimize the procedure. The cool-down is driven by the helium flowing in both the outer cooling channel and in the windings connected hydraulically in parallel. We take into account limitations due to the pressure drop in the cooling circuit and the refrigerator capacity as well as heat conduction in the iron yoke. Two schemes of the hydraulic cooling circuit in the EDIPO windings are studied (coils connected in series and coils connected in parallel). The analysis is performed by means of an analytical model complemented by and numerical model. The results indicate that the cool-down to 5 K can be achieved in about 12 days. 相似文献
115.
Zusammenfassung In diesem Artikel beschreiben wir die Entwicklung von Interaktivit?t in der Medienkunst, die einhergeht mit der Entwicklung
von Vernetzungsstrukturen und der Herausbildung disziplinübergreifender Arbeitsweisen. Vorwiegend am Beispiel unserer eigenen
Arbeiten der vergangenen 20 Jahre zeichnen wir die Entwicklung interaktiver Kunst von einer neuartigen ?sthetischen Erfahrung
über eine verst?rkte Raumorientierung bis hin zum kulturellen Wissens- und Ged?chtnisspeicher nach. 相似文献
116.
117.
Hilal Şahin Ayhan Topuz Monika Pischetsrieder Feramuz Özdemir 《European Food Research and Technology》2009,230(1):155-161
Roasted carob powder was obtained using different time–temperature combinations and some quality characteristics such as total
phenolic content (TPC), total antioxidant activity (TAA), browning index (BI) at 420 nm, UV absorbance (UV-A) at 294 nm, and
pH has been investigated. Both the roasting temperature and time significantly (P < 0.01) affected the quality characteristics of the product. However, the roasting time was found to be a critical factor
in determining the overall quality of the product. While the TPC, TAA, BI and UV-A values of the samples increased with the
increasing roasting temperature and time, the pH of the samples decreased gradually. The quality characteristics of the carob
powders changed markedly in between 20 and 60 min of roasting which indicates that the heat-induced reactions accelerate particularly
in that period of roasting. The correlations between all these chemical properties of carob powder were found to be significant
(P < 0.0001) during roasting. 相似文献
118.
Marta Anna Lech Monika Lekiewicz Kinga Kamiska Zofia Rog Elbieta Lorenc-Koci 《International journal of molecular sciences》2021,22(12)
Growing body of evidence points to dysregulation of redox status in the brain as an important factor in the pathogenesis of schizophrenia. The aim of our study was to evaluate the effects of l-buthionine-(S,R)-sulfoximine (BSO), a glutathione (GSH) synthesis inhibitor, and 1-[2-Bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine dihydrochloride (GBR 12909), a dopamine reuptake inhibitor, given alone or in combination, to Sprague–Dawley pups during early postnatal development (p5–p16), on the time course of the onset of schizophrenia-like behaviors, and on the expression of brain-derived neurotrophic factor (BDNF) mRNA and its protein in the prefrontal cortex (PFC) and hippocampus (HIP) during adulthood. BSO administered alone decreased the levels of BDNF mRNA and its protein both in the PFC and HIP. Treatment with the combination of BSO + GBR 12909 also decreased BDNF mRNA and its protein in the PFC, but in the HIP, only the level of BDNF protein was decreased. Schizophrenia-like behaviors in rats were assessed at three time points of adolescence (p30, p42–p44, p60–p62) and in early adulthood (p90–p92) using the social interaction test, novel object recognition test, and open field test. Social and cognitive deficits first appeared in the middle adolescence stage and continued to occur into adulthood, both in rats treated with BSO alone or with the BSO + GBR 12909 combination. Behavior corresponding to positive symptoms in humans occurred in the middle adolescence period, only in rats treated with BSO + GBR 12909. Only in the latter group, amphetamine exacerbated the existing positive symptoms in adulthood. Our data show that rats receiving the BSO + GBR 12909 combination in the early postnatal life reproduced virtually all symptoms observed in patients with schizophrenia and, therefore, can be considered a valuable neurodevelopmental model of this disease. 相似文献
119.
Barbara Kolsch Prof. Dr. rer. nat. A. Rahmel Monika Schorr 《Materialwissenschaft und Werkstofftechnik》1989,20(11):369-384
Behaviour of gas turbine blade materials under mechanical long term loading and hot gas corrosion. Part 2: Metallographical and microanalytical investigations Results of metallographical and microanalytical investigations on selected specimens after mechanical long term creep and LCF-loading under hot gas corrosion conditions will be presented. Uncoated and MCrAlY or Al-diffusion coated specimens of the polycristalline materials IN-738 LC and IN-939 and the single crystal alloys M 002 mod., CM-SX-6 and B 1914 were investigated. The corrosion attack increases with increasing impurities of the hot gas. Internal nitridation and sulphidation of base material or coating is observed after deterioration of the protective scales rich in Cr2O3 and/or Al2O3. 相似文献
120.
Mittelorientierte Einkristalle verformen sich im Druckversuch über ihre Länge nicht homogen. Es wird ein Rechenverfahren angegeben, in dem diese Inhomogenitäten berücksichtigt werden und Schubspannungs-Abgleitungskurven für den homogen verformten Teil der Probe errechnet werden können. Die Rechnung wird an experimentellen Ergebnissen von Fe—6 Gew.% Si überprüft. 相似文献