全文获取类型
收费全文 | 1552篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 71篇 |
金属工艺 | 8篇 |
机械仪表 | 13篇 |
建筑科学 | 10篇 |
能源动力 | 18篇 |
轻工业 | 61篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 23篇 |
一般工业技术 | 56篇 |
冶金工业 | 1254篇 |
原子能技术 | 2篇 |
自动化技术 | 46篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 14篇 |
2021年 | 22篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 20篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 32篇 |
2012年 | 22篇 |
2011年 | 21篇 |
2010年 | 19篇 |
2009年 | 12篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 9篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 45篇 |
1998年 | 408篇 |
1997年 | 213篇 |
1996年 | 149篇 |
1995年 | 83篇 |
1994年 | 55篇 |
1993年 | 79篇 |
1992年 | 5篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 24篇 |
1987年 | 15篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 1篇 |
1978年 | 7篇 |
1977年 | 23篇 |
1976年 | 63篇 |
1975年 | 2篇 |
排序方式: 共有1569条查询结果,搜索用时 15 毫秒
81.
The Doppler technique has been used to evaluate venous reflux in the spermatic cord. Valsalva-induced reflux occurred on the left side in 83% and on the right side in 59% of 118 patients without clinical varicoceles and there was no difference in incidence between fertile and infertile men. The significance of Valsalva-induced reflux should be questioned. Greater importance should be attributed to the spontaneous venous reflux that occurred during quiet respiration in the majority of patients with varicoceles. Seven velocity waveform patterns are described and these are thought to represent increasing degrees of internal spermatic vein reflux and provide a basis on which it is possible to grade varicoceles. The Doppler grades correlated with the size of the varicocele, and with the internal spermatic vein diameter and testosterone concentrations. 相似文献
82.
Reversal of pretreatment hypotension and control of hemorrhage in trauma patients by a simple device
JM Civetta ST Nussenfeld EL Nagel BH Kaplan TR Rowe F Pettijohn 《Canadian Metallurgical Quarterly》1977,43(1):20-29
The injection of a suspension of Walker 256 carcinoma cells into the carotid artery of rats produced a model of hematogenously spread cerebral metastases. Most animals died from massive extracerebral tumors of the head and jaw; brain tumors were present in only one-quarter. External carotid artery ligation prior to tumor inoculation did not increase the incidence of fatal brain tumor. When cyclophosphamide, 15 mg/kg, was injected as a single dose on the fourteenth day after tumor inoculation, most of the extracerebral tumor disappeared. Fifty percent of the animals so treated were cured of tumor, but 90% of the remainder died of large intracerebral tumors. Severe cytopathic changes resulting from cyclophosphamide were present in extracerebral or choroid plexus tumors but were mild or nonexistent in intracerebral tumors. These selective effects of cyclophosphamide suggest that water-soluble agents are less effective against tumor in the brain than against extracerebral tumors despite the fact that metastatic tumor breaks down the blood-brain barrier. 相似文献
83.
Tatiana S. de Araujo Zélia S. Macedo Petrus A. S. C. de Oliveira Mário E. G. Valerio 《Journal of Materials Science》2007,42(7):2236-2243
Pure and Cr3+-doped hydroxyapatite (HAP) were prepared via chemical precipitation route. The XRD measurements revealed that the typical
HAP powder pattern was obtained. SEM analysis indicated that aggregates of nanoparticles were formed. EDX analysis indicates
that the [Ca]/[P] concentration ratio was higher than the expected values but can be explained by the presence of carbonate
groups as dopants. The optical absorption spectra of the doped samples presented absorption bands typical of Cr3+ occupying to different crystalline sites. From the position of the bands, it was possible to estimate the crystal field parameters
for both sites of Cr3+ in the HAP matrix. The emission spectra of the Cr-doped samples were also investigated and typical transitions of the dopant
ion, in trivalent state, were identified. The potential use of the Cr3+-HAP as fluorescent probes for medical applications was discussed. 相似文献
84.
Chiara Renso Miriam Baglioni Jose António F. de Macedo Roberto Trasarti Monica Wachowicz 《Knowledge and Information Systems》2013,37(2):331-362
The widespread use of mobile devices is producing a huge amount of trajectory data, making the discovery of movement patterns possible, which are crucial for understanding human behavior. Significant advances have been made with regard to knowledge discovery, but the process now needs to be extended bearing in mind the emerging field of behavior informatics. This paper describes the formalization of a semantic-enriched KDD process for supporting meaningful pattern interpretations of human behavior. Our approach is based on the integration of inductive reasoning (movement pattern discovery) and deductive reasoning (human behavior inference). We describe the implemented Athena system, which supports such a process, along with the experimental results on two different application domains related to traffic and recreation management. 相似文献
85.
Emerson de Araujo Macedo Alba Cristina Magalhaes Alves de Melo Gerson Henrique Pfitscher Azzedine Boukerche 《The Journal of supercomputing》2013,63(3):740-756
Multiple Sequence Alignment (MSA) is an important problem in Bioinformatics that aims to align more than two sequences in order to emphasize similarity regions. This problem is known to be NP-Hard, so heuristic methods are used to solve it. DIALIGN-TX is an iterative heuristic method for MSA that generates alignments by concatenating ungapped regions with high similarity. Usually, the first phase of MSA algorithms is parallelized by distributing several independent tasks among the nodes. Even though heterogeneous multicore clusters are becoming very common nowadays, very few task allocation policies were proposed for this type of architecture. This paper proposes an MPI/OpenMP master/slave parallel strategy to run DIALIGN-TX in heterogeneous multicore clusters, with several allocation policies. We show that an appropriate choice of the master node has great impact on the overall system performance. Also, the results obtained in a heterogeneous multicore cluster composed of 4 nodes (30 cores), with real sequence sets show that the execution time can be drastically reduced when the appropriate allocation policy is used. 相似文献
86.
Nadia Nedjah Luneque Silva Junior Luiza de Macedo Mourelle 《Expert systems with applications》2013,40(16):6661-6673
Networks-on-Chip (NoC) is an interesting option in design of communication infrastructures for embedded systems. It provides a scalable structure and balanced communication between the cores. Parallel applications that take advantage of the NoC architectures, are usually are communication-intensive. Thus, a big deal of data packets is transmitted simultaneously through the network. In order to avoid congestion delays that deteriorate the execution time of the implemented applications, an efficient routing strategy must be thought of carefully. In this paper, the ant colony optimization paradigm is explored to find and optimize routes in a mesh-based NoC. The proposed routing algorithms are simple yet efficient. The routing optimization is driven by the minimization of total latency during packets transmission between the tasks that compose the application. The presented performance evaluation is threefold: first, the impact of well-known synthetic traffic patterns is assessed; second, randomly generated applications are mapped into the NoC infrastructure and some synthetic communication traffics, that follow known patterns, are used to simulate real situations; third, sixteen real-world applications of the E3S and one specific application for digital image processing are mapped and their execution time evaluated. In both cases, the obtained results are compared to those obtained with known general purpose algorithms for deadlock free routing. The comparison avers the effectiveness and superiority of the ant colony inspired routing. 相似文献
87.
Surendran Rajesh Daniel A. Macedo Rubens M. Nascimento Graziele L. Souza Filipe M.L. Figueiredo Fernando M.B. Marques 《International Journal of Hydrogen Energy》2013
Europium-doped ceria (EDC, Ce0.9Eu0.1O2−δ)/alkaline carbonate (LNC, (Li,Na)2CO3) composite ceramics prepared through a one-step citrate-based route were analyzed by powder X-ray diffraction, infrared and laser Raman spectroscopies as well as scanning and transmission electron microscopy. The electrochemical behavior of the electrolyte material was studied by impedance spectroscopy in air, CO2 and N2 + H2 (90/10 vol%, respectively) gas mixtures, in the temperature range 300–600 °C. The sub micrometric and even nanosized ceramic particles appeared as merged inside the mixed carbonates, with modest grain to grain necking. The EDC/LNC composite electrolytes showed a conductivity of 0.27 S cm−1 at 600 °C in air, amongst the best ever reported, exceeding the usual requirements for fuel cell applications. 相似文献
88.
N Noviski JP Brewer WA Skornik SJ Galli JM Drazen TR Martin 《Canadian Metallurgical Quarterly》1999,86(1):202-210
Exposure to ambient ozone (O3) is associated with increased exacerbations of asthma. We sought to determine whether mast cell degranulation is induced by in vivo exposure to O3 in mice and whether mast cells play an essential role in the development of pulmonary pathophysiological alterations induced by O3. For this we exposed mast cell-deficient WBB6F1-kitW/kitW-v (kitW/kitW-v) mice and the congenic normal WBB6F1 (+/+) mice to air or to 1 or 3 parts/million O3 for 4 h and studied them at different intervals from 4 to 72 h later. We found evidence of O3-induced cutaneous, as well as bronchial, mast cell degranulation. Polymorphonuclear cell influx into the pulmonary parenchyma was observed after exposure to 1 part/milllion O3 only in mice that possessed mast cells. Airway hyperresponsiveness to intravenous methacholine measured in vivo under pentobarbital anesthesia was observed in both kitW/kitW-v and +/+ mice after exposure to O3. Thus, although mast cells are activated in vivo by O3 and participate in O3-induced polymorphonuclear cell infiltration into the pulmonary parenchyma, they do not participate detectably in the development of O3-induced airway hyperresponsiveness in mice. 相似文献
89.
90.
Angela C. Macedo F. X. Malcata 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1997,204(3):173-179
Experimental Serra cheeses were manufactured from raw ewe’s milk and thistle flowers following a two-way factorial design.
The content of nitrogen soluble in water (WSN), in 2% trichloroacetic acid (2% TCA-N), in 12% TCA (TCA-N) and in 5% phosphotungstic
acid (5% PTA-N), and the pH and salt-in-moisture concentration were measured throughout the ripening period (sampling at 0,
7, 21 and 35 days) and the cheese-making season (sampling in November, February and May). Proteolysis in 35-day-old Serra
cheese was quantitatively high [average values of 34.6% and 11.9% for WSN/TN (total nitrogen) and 2% TCA-N/TN, respectively],
but qualitatively low (average values of 5.8% and 1.2% for 12% TCA-N/TN and 5% PTA-N/TN, respectively). The ratios WSN/TN
and 2% TCA-N/TN were lowest for cheeses ripened in February, whereas the ratio 12% TCA-N/TN was highest for cheeses ripened
in November. By 35 days of ripening, the average pH and salt-in-moisture concentration values were 5.2 and 4.8%, respectively.
No correlation was found to occur between the measured pH or salt-in-moisture concentration and the values of soluble nitrogen
fractions throughout the cheese-making season.
Received: 14 February 1996/Revised version: 4 June 1996 相似文献