全文获取类型
收费全文 | 3380篇 |
免费 | 23篇 |
专业分类
电工技术 | 20篇 |
综合类 | 1篇 |
化学工业 | 255篇 |
金属工艺 | 28篇 |
机械仪表 | 13篇 |
建筑科学 | 32篇 |
矿业工程 | 1篇 |
能源动力 | 14篇 |
轻工业 | 69篇 |
水利工程 | 13篇 |
无线电 | 105篇 |
一般工业技术 | 175篇 |
冶金工业 | 2510篇 |
原子能技术 | 8篇 |
自动化技术 | 159篇 |
出版年
2018年 | 15篇 |
2017年 | 13篇 |
2015年 | 13篇 |
2014年 | 12篇 |
2013年 | 45篇 |
2012年 | 34篇 |
2011年 | 49篇 |
2010年 | 26篇 |
2009年 | 27篇 |
2008年 | 34篇 |
2007年 | 48篇 |
2006年 | 28篇 |
2005年 | 27篇 |
2004年 | 19篇 |
2003年 | 34篇 |
2002年 | 26篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 105篇 |
1998年 | 829篇 |
1997年 | 484篇 |
1996年 | 290篇 |
1995年 | 155篇 |
1994年 | 156篇 |
1993年 | 158篇 |
1992年 | 40篇 |
1991年 | 36篇 |
1990年 | 18篇 |
1989年 | 32篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 19篇 |
1985年 | 29篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 25篇 |
1980年 | 26篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1977年 | 56篇 |
1976年 | 113篇 |
1975年 | 16篇 |
1974年 | 16篇 |
1973年 | 13篇 |
1972年 | 16篇 |
1971年 | 14篇 |
1970年 | 13篇 |
1969年 | 19篇 |
1968年 | 13篇 |
排序方式: 共有3403条查询结果,搜索用时 15 毫秒
51.
Christopher L Brown Gillian Bushell Michael W Whitehouse DS Agrawal SG Tupe KM Paknikar Edward RT Tiekink 《Gold bulletin》2007,40(3):245-250
Nanosized gold particles (27 +/− 3 nm) have been proven to be effective in ameliorating the symptoms of mycobacterial-, collagen-
and pristane-induced arthritis in rat models. This contrasts with the drug sodium aurothiomalate that was only effective against
mycobacterial-induced arthritis but not to the same extent as Au0. Gold in the traditional Indian Ayurvedic medicine,Swarna bhasma (gold ash), has been characterized as globular particles of gold with an average size of 56–57 nm. 相似文献
52.
The reaction of H atoms (produced by nanosecond pulse radiolysis) with ferri-cytochrome-c in aqueous solution results in the second order formation of an absorption spectrum due to the addition of H atoms to the enzyme protein. This spectrum is not specific to the iron moiety. The rate constant of the addition is 1×1010M?1 sec?1. This is followed by two first order intramolecular processes with specific rates of ~ 1×105 sec?1 and ~ 2×104 sec?1. In these processes, specific spectra related to the α and β bands of ferro-cytochrome-c appear. The results are interpreted to show reduction equivalent transfer through the protein to the iron moiety. 相似文献
53.
W. Stein H. Weiß O. Koch P. Neuhausen H. Baumann 《European Journal of Lipid Science and Technology》1970,72(11):956-959
Preparation of Esters of α-Sulfo-Fatty Acids A process for the continuous α-sulfonation of saturated fatty acid esters with SO3 was worked out and a special bleaching process was developed for these products. The conversion, i. e. the degree of sulfonation is of the order of 95–99%. Solvents, further processing steps or purification operations for the separation of by-products are not required. 相似文献
54.
In principle, the oil milling process is straightforward. The wide variety of equipment in use reflects, however, a multiparametric
process. The main limiting parameters are kind of seed, oil content, particle strength, particle structure, temperature, moisture,
particle size, residence time, mechanical forces, etc. Additionally, the seed specific parameters vary not only between kinds
of seed but also for the same seed, due to different conditions in climate, soil, and harvesting. Therefore, equipment design
must be widely based on statistical averages of the limiting parameters. In other words, exact precalculation of the single
technological steps is impossible. As a consequence, for more than 5,000 years, the oil milling process has been in the stage
of being optimized. The acutal technical standard is very satisfying, but there is still a strong need for further research
and development. Currently, as in the past, the oil milling process seems to be not so much a science as an art. 相似文献
55.
J. G. M. de Jong H. N. Stein J. M. Stevels 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1969,19(1):25-28
Amorphous silica influences tricalcium aluminate (C3A) hydration both in pastes and in suspensions. Two heat peaks are found by isothermal calorimetry during the paste hydration of C3A. The addition of amorphous silica causes the second heat peak to shift towards shorter reaction times and become more pronounced. In suspensions, the change in ion concentration in the water phase is not influenced by the presence of amorphous silica except that the change in concentration occurs more quickly. Quantitative X-ray analysis shows that more 3CaO.Al2O3.6H2O is present in suspensions containing amorphous silica than in silica-free suspensions at equal hydration times. 相似文献
56.
It is shown that in thermal polymerization of styrene four dimers and six trimers are formed by parallel occurring oligomerization reactions. With increasing temperature the rate of oligomerization increases more rapidly than the rate of polymerization. The relativ yields of the different oligomers depend on temperature, too. 相似文献
57.
Stein K 《Architectural record》1991,179(2):72-77
Two recent projects by Jeffrey Hildner for a private nursing home in Princeton, New Jersey, reconcile the architect's interest in art and the client's emphasis on utility. 相似文献
58.
A preliminary study of materials exposed in space in a low-earth orbit for nearly 6 years (in the NASA Long-Duration Exposure Facility) has revealed a wide range of micrometeorite or microparticle impact craters ranging in size from 1–100 m diameter, debris particles from adjacent and distant materials systems, reaction products and other growth features on the specimen surfaces, and related phenomena. The exposed-surface features included finegrained and nearly amorphous materials as well as single-crystal particles. A replication-type, lift-off technique was developed to remove reaction products and debris from the specimen surfaces in order to isolate them from the background substrate without creating microchemical or microstructural artefacts or alterations. This resulted in surface features resting on a carbon support film which was virtually invisible to observation by electron microscopy and non-dispersive X-ray analysis. Characterization of these surface features involved observations by optical metallography, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis; including an analytical transmission electron microscope with a STEM attachment. The results illustrate a wide variety of materials phenomena which must be addressed in the evaluation of materials exposure in space, and the formidable materials characterization effort which will be necessary to understand these features. 相似文献
59.
We developed a visual analysis tool to support the verification, assessment, and presentation of alleged cases of plagiarism. The analysis of a suspicious document typically results in a compilation of categorized “finding spots”. The categorization reveals the way in which the suspicious text fragment was created from the source, e.g. by obfuscation, translation, or by shake and paste. We provide a three‐level approach for exploring the finding spots in context. The overview shows the relationship of the entire suspicious document to the set of source documents. A glyph‐based view reveals the structural and textual differences and similarities of a set of finding spots and their corresponding source text fragments. For further analysis and editing of the finding spot's assessment, the actual text fragments can be embedded side‐by‐side in the diffline view. The different views are tied together by versatile navigation and selection operations. Our expert reviewers confirm that our tool provides a significant improvement over existing static visualizations for assessing plagiarism cases. 相似文献
60.
Abstract. We consider two fundamental problems in dynamic scheduling: scheduling to meet deadlines in a preemptive multiprocessor setting,
and scheduling to provide good response time in a number of scheduling environments. When viewed from the perspective of traditional
worst-case analysis, no good on-line algorithms exist for these problems, and for some variants no good off-line algorithms
exist unless P = NP .
We study these problems using a relaxed notion of competitive analysis, introduced by Kalyanasundaram and Pruhs, in which
the on-line algorithm is allowed more resources than the optimal off-line algorithm to which it is compared. Using this approach,
we establish that several well-known on-line algorithms, that have poor performance from an absolute worst-case perspective,
are optimal for the problems in question when allowed moderately more resources. For optimization of average flow time, these
are the first results of any sort, for any NP -hard version of the problem, that indicate that it might be possible to design good approximation algorithms. 相似文献