全文获取类型
收费全文 | 13234篇 |
免费 | 1165篇 |
国内免费 | 395篇 |
专业分类
电工技术 | 668篇 |
综合类 | 480篇 |
化学工业 | 2324篇 |
金属工艺 | 506篇 |
机械仪表 | 564篇 |
建筑科学 | 710篇 |
矿业工程 | 156篇 |
能源动力 | 398篇 |
轻工业 | 1283篇 |
水利工程 | 213篇 |
石油天然气 | 267篇 |
武器工业 | 75篇 |
无线电 | 1770篇 |
一般工业技术 | 1781篇 |
冶金工业 | 1563篇 |
原子能技术 | 159篇 |
自动化技术 | 1877篇 |
出版年
2024年 | 64篇 |
2023年 | 232篇 |
2022年 | 470篇 |
2021年 | 680篇 |
2020年 | 489篇 |
2019年 | 411篇 |
2018年 | 466篇 |
2017年 | 438篇 |
2016年 | 477篇 |
2015年 | 511篇 |
2014年 | 649篇 |
2013年 | 800篇 |
2012年 | 829篇 |
2011年 | 945篇 |
2010年 | 680篇 |
2009年 | 640篇 |
2008年 | 652篇 |
2007年 | 574篇 |
2006年 | 463篇 |
2005年 | 369篇 |
2004年 | 310篇 |
2003年 | 272篇 |
2002年 | 293篇 |
2001年 | 235篇 |
2000年 | 192篇 |
1999年 | 212篇 |
1998年 | 522篇 |
1997年 | 333篇 |
1996年 | 257篇 |
1995年 | 139篇 |
1994年 | 153篇 |
1993年 | 132篇 |
1992年 | 80篇 |
1991年 | 80篇 |
1990年 | 67篇 |
1989年 | 78篇 |
1988年 | 42篇 |
1987年 | 40篇 |
1986年 | 43篇 |
1985年 | 47篇 |
1984年 | 39篇 |
1983年 | 39篇 |
1982年 | 38篇 |
1981年 | 29篇 |
1980年 | 29篇 |
1979年 | 23篇 |
1977年 | 43篇 |
1976年 | 62篇 |
1975年 | 16篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
V. Pichot M. Comet E. Fousson C. Baras A. Senger F. Le Normand D. Spitzer 《Diamond and Related Materials》2008,17(1):13-22
This article reports the purification process of detonation soot to obtain pure nanodiamond powder. Nanodiamonds are synthesized by detonation using a high explosive mixture composed of trinitrotoluene and hexogen. The detonation of the charge leads to a powder containing nanodiamonds as well as metallic impurities and sp2 carbon species. Further, to remove metallic particles, an unusual acidic treatment (hydrofluoric/nitric acids; i.e. fluorinated aqua regia) was set up. To eliminate sp2 carbon species such as graphite and amorphous carbon, a thermal oxidation treatment was performed at 420 °C under air in a furnace during several hours. Transmission Electronic Microscopy, Raman spectroscopy, X-ray diffraction and Thermo-Gravimetric Analysis showed that this purification process is very efficient. From TGA measurements, a model of the carbon grain combustion was developed by considering graphitic shells surrounding the nanodiamond particles, and was used to demonstrate that the selective oxidation of graphite was experimentally realistic. Moreover, another model was set up from specific area measurements to evaluate the thickness of the functional groups surrounding the nanodiamonds after the oxidation of sp2 carbonaceous species. The treatment described herein was achieved on several tens of grams of product and could be easily adapted to the industrial scale. 相似文献
92.
J Desaki M Kinutani K Tan-Takeuchi NM Le Douarin 《Canadian Metallurgical Quarterly》1996,45(5):448-452
The migration of leucocytes through the walls of venules was examined in detail in the posterior latissimus dorsi muscle of quail-chick spinal cord chimeras, in which flaccid paralysis of the wings was observed. Examinations were made from the 70th to 80th day after hatching. Muscle fibers were degenerated and intramuscular nerve bundles destroyed. Massive leucocytes (almost lymphocytes) were found around the venules, depending on the passage of wandering leucocytes through the endothelium. Lymphocytes penetrated and were encased in the cytoplasm of the venular endothelial cell, and did not pass through the interendothelial junction. These findings suggest that, in the venules of the atrophied chimeric muscle, wandering leucocytes in the blood may pass through the endothelial cell body and migrate into the inflamed extravascular space. 相似文献
93.
A. T. Sousa P. S. Fialho C. A. Nieto de Castro R. Tufeu B. Le Neindre 《International Journal of Thermophysics》1996,17(3):551-560
The density of HCFC 141b has been measured at several temperatures between 260 and 320 K, Mid pressures up to 20 MPa, with a mechanical oscillator densimeter. The densimeter was calibrated with 2,2,4-trimethylpentane, whose density was obtained from a correlating cyuation with 0.3% uncertainty. The density data obtained for HCFC 14H) hits a reproducibility of 0.05% and an uncertainty of 0.3%. The data obtained were fitted to a Tait-type equation. which reproduced the experimental densities within 0.11 % and were compared with the data obtained in other works.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
94.
95.
MT Le Cam P Wolkenstein A Cosnes H Bocquet P Gaulard M Tulliez C Cordonnier JC Roujeau M Bagot J Revuz 《Canadian Metallurgical Quarterly》1997,124(9):621-622
INTRODUCTION: Acute mast cell leukemia is a rare and severe disease. We report herein a case associated with a flush syndrome. CASE REPORT: A 44-year-old man, presented with a flush of face and trunk. Bone marrow was infiltrated with immature mast cells. In spite of chemotherapy and bone marrow transplantation the patient deceased. DISCUSSION: Pheochromocytoma, carcinoid tumor, and mastocytosis are associated with a flush syndrome. In our patient the diagnosis was an acute mast cell leukemia. Acute mast cell leukemia can follow systemic mastocytosis or occur de novo. This disease is of poor prognosis. No treatment is available. 相似文献
96.
D. Le Masne 《Geothermics》1985,14(5-6)
Within the framework of an EEC project involving ten European laboratories, research on the application of several electric and electromagnetic methods to a geothermal field (Travale, Tuscany), has been undertaken by the B.R.G.M. The objective was to refine the conceptual model of the Travale field and, therefore, to describe the morphology of the basement (down to 2 km depth) and of the Rhaetian reservoir covered by impermeable series.The method best suited to this type of prospection appeared to be electrical dipole — dipole profiling, combined with a 2-D interpretation. Contrasts at more than 2 km depth (500 m long dipoles) could be seen and compared to the depths measured in the boreholes. The EM Melos method (Syscal equipment) should be improved (lower frequencies) to increase the depth penetration. It is, however, a good complementary method for the surface layers. An attempt at a computational interpretation of the self potential profiles gave promising results. To make full advantage of the bipole — dipole measurements efforts should be devoted to their computational interpretation. 相似文献
97.
本文自行设计和制作了1.30μmDFB激光器组件的讨论了光隔离和光耦合原理。由于采用的激光器-光隔离器-光纤的一体化结构,大大增加了该组件的可用性。在实验中得到高达55%的耦合效率。 相似文献
98.
Pascal Le Gauffre Hatem Haidar David Poinard Katia Laffréchine Rolf Baur Marcello Schiatti 《Computer-Aided Civil and Infrastructure Engineering》2007,22(7):478-488
Abstract: This article provides an overview of a multicriteria decision support methodology for annual rehabilitation programs of water networks. A first set of criteria is formulated for the purpose of comparing and ranking rehabilitation projects. Each proposed criterion is a measure of a particular impact of the condition of a pipe. The ELECTRE TRI method is implemented for defining rehabilitation priorities . Two reference profiles are used to define the limits of three categories associated with three increasing priority levels. With these two reference profiles, applying the ELECTRE TRI method to an asset stock ( a set of pipes that are candidates for rehabilitation ) means assigning each pipe to one of six possible priority groups. A second set of criteria, based on the concept of efficiency, is proposed for comparing alternative rehabilitation programs ( subsets of the asset stock ). 相似文献
99.
The International Telecommunication Union (ITU) has completed work on a series of standards on asynchronous transfer mode (ATM) equipment functional operations and network element management. The objective of these standards is to enable flexible design and interoperability of network elements for use in a global ATM network, independent of any specific implementation. This article discusses these standards with respect to their development and application in planning ATM networks. Specifically, it addresses the following: the modeling approach taken in the development of the ITU standards, key operational features specified in the ATM network element functional model, and the capabilities of the ATM network element management interface. Examples of ATM equipment are provided to illustrate how the functional models specified in the ITU standards may be used by network planners and equipment manufacturers to specify and develop ATM equipment tailored to specific needs, while ensuring network interoperability. The article concludes with some points on the future enhancement of these and related ATM equipment operations standards 相似文献
100.