全文获取类型
收费全文 | 614篇 |
免费 | 33篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 220篇 |
金属工艺 | 2篇 |
机械仪表 | 16篇 |
建筑科学 | 19篇 |
能源动力 | 19篇 |
轻工业 | 69篇 |
水利工程 | 1篇 |
无线电 | 28篇 |
一般工业技术 | 70篇 |
冶金工业 | 76篇 |
原子能技术 | 2篇 |
自动化技术 | 122篇 |
出版年
2023年 | 13篇 |
2022年 | 55篇 |
2021年 | 54篇 |
2020年 | 18篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 25篇 |
2015年 | 22篇 |
2014年 | 33篇 |
2013年 | 39篇 |
2012年 | 30篇 |
2011年 | 25篇 |
2010年 | 21篇 |
2009年 | 35篇 |
2008年 | 19篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 21篇 |
2004年 | 13篇 |
2003年 | 15篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1993年 | 10篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有647条查询结果,搜索用时 0 毫秒
1.
Five studies examined the hypotheses that when people experience positive affect, those low in self-esteem are especially likely to dampen that affect, whereas those high in self-esteem are especially likely to savor it. Undergraduate participants' memories for a positive event (Study 1) and their reported reactions to a success (Study 2) supported the dampening prediction. Results also suggest that dampening was associated with worse mood the day after a success (Study 2), that positive and negative affect regulation are distinct, that self-esteem is associated with affect regulation even when Neuroticism and Extraversion are controlled (Studies 3 and 4), and that self-esteem may be especially important for certain types of positive events and positive affect regulation (Study 5). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
Mixtures of fly ash, bottom ash and Flue Gas Desulphurized (FGD) gypsum, all solid wastes from coalfired electric generating plants, can be combined with lime and 10% of water to produce a damp powder which can be moulded at a pressure of 20–40 MPa and then steam-cured in less than 1 day at 35–80°C. The resulting building materials-in the form of bricks, blocks or slabs-produced by this Pressure Forming (PF) process, are stronger and sounder than the corresponding materials produced by a slip casting (SC) process. The physical and mechanical properties of the materials manufactured through the PF process are based on the reaction of amorphous silica and alumina of the ash with lime or lime and gypsum respectively, so that calcium silicate hydrate and ettringite are produced. When the temperature of the steam curing is as low as 35°C, the hardened material is sound in the air, but it swells and is quickly destroyed by the action of water. This effect can be ascribed to the formation of ill-crystallized ettringite. On the other hand, with thermal treatment at higher temperatures (60–80°C), the material is stronger and sound even in the presence of water in service. The well-crystallized ettringite fibers, favoured by the higher temperature of the steam curing treatment, are considered to be responsible for the better mechanical performances and the lower change in length. In general, the physical and mechanical properties of the ash-gypsym-lime cementitious system are better than those of the traditional clay-based ceramic products manufactured at temperatures as high as 1000°C. Therefore, this process based on steam curing at 60–80°C appears to be very useful for both the re-utilization of solid wastes and the saving of energy in the production of building materials. 相似文献
3.
4.
Muscetti Michela Rinaldi Antonio M. Russo Cristiano Tommasino Cristian 《Knowledge and Information Systems》2022,64(5):1283-1303
Knowledge and Information Systems - The rapid increase of available data in different complex contexts needs automatic tasks to manage and process contents. Semantic Web technologies represent the... 相似文献
5.
Progressive Transmission of Vector Map Data over the World Wide Web 总被引:17,自引:0,他引:17
Within distributed computing environments, access to very large geospatial datasets often suffers from slow or unreliable network connections. To allow users to start working with a partially delivered dataset, progressive transmission methods are a viable solution. While incremental and progressive methods have been applied successfully to the transmission of raster images over the World Wide Web, and, in the form of prototypes, of triangular meshes, the transmission of vector map datasets has lacked a similar attention. This paper introduces a solution to the progressive transmission of vector map data that allows users to apply analytical GIS methods to partially transmitted data sets. The architecture follows a client-server model with multiple map representations at the server side, and a thin client that compiles transmitted increments into a topologically consistent format. This paper describes the concepts, develops an architecture, and discusses implementation concerns. 相似文献
6.
P Cugini L Di Palma P Battisti A Coppola F Cipriano G Leone 《M.D. computing : computers in medical practice》1991,8(1):26-31
Clinical research has defined the criteria for identifying "curable" renovascular hypertension. The prediction is based on the measurement of plasma renin activity in peripheral veins, renal veins, and the aorta. Renin profiles can be examined with the method of Laragh and coworkers (the so-called incremental method), in which values for plasma renin activity are incorporated into formulas to compute indexed parameters. A score is attributed to each index and the prediction is based on the final score. Because the identification of curable renovascular hypertension is made according to numerical rules, the method is easily transformed into a computer-assisted process. The program is written in BASIC, and it is short enough to run on a personal computer. 相似文献
7.
Its more refined congestion control mechanisms, also based on the estimation of round trip delays, allow TCP Vegas to outperform the more widespread TCP Reno congestion control, based only on the packet loss detection, in a number of network environments. However, these mechanisms make TCP Vegas less aggressive with respect to TCP Reno; thereby TCP Vegas sources show high weakness in taking the available bandwidth when competing with other TCP Reno sources. This is a major reason that hinders the spread of TCP Vegas among Internet users. In this work, after a preliminary analytic study about the limits of TCP Vegas in mixed network environments, we describe a new adaptive mechanism for TCP Vegas, called TCP NewVegas, designed in order to improve its performance even in heterogeneous network scenarios. The large number of simulations, presented in this paper, show that TCP NewVegas guarantees good performance even in mixed network environments, without canceling the desirable features (e.g. fairness) that TCP Vegas exhibits in homogeneous environments. 相似文献
8.
Alessandro Ricci Michela Fratini Antonio Bianconi 《Journal of Superconductivity and Novel Magnetism》2009,22(3):305-308
We report the temperature-dependent x-ray powder diffraction of the FeAs-based superconductors in the range between 300 and
95 K. In the case of NdOFeAs we have detected the structural phase transition from the tetragonal phase, with P4/nmm space
group, to the orthorhombic phase, with Cmma space group, over a broad temperature range from 150 to 120 K, centered at T
0∼137 K. This transition is reduced, by about ∼30 K, by the internal chemical pressure going from LaOFeAs to NdOFeAs. On the
contrary, the superconducting critical temperature increases from 27 to 51 K going from LaOFeAs to NdOFeAs doped samples.
The FeAs layers in all undoped “1111” and “122” systems suffer a tensile misfit strain. The tensile misfit strain is reduced
in “1111” and in “122” samples and at optimum doping the misfit strain is close to zero. This result shows that the normal
striped orthorhombic Cmma phase competes with the superconducting tetragonal phase. In the orthorhombic clusters the charges
can move only along the stripes in the b direction and are localized by the magnetic interaction. 相似文献
9.
Veronica Conti Claudio Cantini Marco Romi Maria Michela Cesare Luigi Parrotta Stefano Del Duca Giampiero Cai 《International journal of molecular sciences》2022,23(10)
Future climate scenarios suggest that crop plants will experience environmental changes capable of affecting their productivity. Among the most harmful environmental stresses is drought, defined as a total or partial lack of water availability. It is essential to study and understand both the damage caused by drought on crop plants and the mechanisms implemented to tolerate the stress. In this study, we focused on four cultivars of tomato, an economically important crop in the Mediterranean basin. We investigated the biochemical mechanisms of plant defense against drought by focusing on proteins specifically involved in this stress, such as osmotin, dehydrin, and aquaporin, and on proteins involved in the general stress response, such as HSP70 and cyclophilins. Since sugars are also known to act as osmoprotectants in plant cells, proteins involved in sugar metabolism (such as RuBisCO and sucrose synthase) were also analyzed. The results show crucial differences in biochemical behavior among the selected cultivars and highlight that the most tolerant tomato cultivars adopt quite specific biochemical strategies such as different accumulations of aquaporins and osmotins. The data set also suggests that RuBisCO isoforms and aquaporins can be used as markers of tolerance/susceptibility to drought stress and be used to select tomato cultivars within breeding programs. 相似文献
10.
The problem of automatically selecting the pose of a 3D object that corresponds to the most informative and intuitive view of the shape is known as the best view problem. In this paper we address the selection of the best view driven by the meaningful features of the shape, in order to maximize the visibility of salient components from the context or from the application point of view. Meaningful features can be automatically detected by means of semantic-oriented segmentations: we tested several approaches with very pleasant results in the automatic generation of thumbnails for large 3D model databases. 相似文献