全文获取类型
收费全文 | 1854篇 |
免费 | 81篇 |
专业分类
电工技术 | 9篇 |
综合类 | 2篇 |
化学工业 | 407篇 |
金属工艺 | 26篇 |
机械仪表 | 14篇 |
建筑科学 | 125篇 |
矿业工程 | 2篇 |
能源动力 | 51篇 |
轻工业 | 184篇 |
水利工程 | 13篇 |
石油天然气 | 11篇 |
无线电 | 107篇 |
一般工业技术 | 391篇 |
冶金工业 | 300篇 |
原子能技术 | 12篇 |
自动化技术 | 281篇 |
出版年
2023年 | 14篇 |
2022年 | 22篇 |
2021年 | 26篇 |
2020年 | 24篇 |
2019年 | 20篇 |
2018年 | 31篇 |
2017年 | 44篇 |
2016年 | 54篇 |
2015年 | 41篇 |
2014年 | 48篇 |
2013年 | 106篇 |
2012年 | 88篇 |
2011年 | 115篇 |
2010年 | 69篇 |
2009年 | 80篇 |
2008年 | 98篇 |
2007年 | 75篇 |
2006年 | 67篇 |
2005年 | 62篇 |
2004年 | 50篇 |
2003年 | 57篇 |
2002年 | 47篇 |
2001年 | 35篇 |
2000年 | 29篇 |
1999年 | 30篇 |
1998年 | 29篇 |
1997年 | 27篇 |
1996年 | 41篇 |
1995年 | 34篇 |
1994年 | 32篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 11篇 |
1990年 | 16篇 |
1989年 | 23篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 17篇 |
1985年 | 40篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 30篇 |
1981年 | 28篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 16篇 |
1977年 | 20篇 |
1975年 | 14篇 |
1974年 | 6篇 |
1973年 | 16篇 |
排序方式: 共有1935条查询结果,搜索用时 15 毫秒
1.
2.
Geoffrey Rowden Shirley Dean James Campbell Philip Belitsky 《Microscopy research and technique》1985,2(6):547-555
Aspiration biopsy of tumors and transplanted organs is a popular atraumatic method for diagnosis and also for the management of patients. Apart from the cytological analyses, it is clear that large aggregates of cells are obtained and these may be examined by electron microscopy. A study was carried out with dogs to assess the yield of intact glomeruli and tubules, resulting from a standard fine-needle aspiration procedure. Employing a 20-gauge needle, yields of approximately ten intact glomeruli were obtained with a tissue processing protocol that utilized filtration through a nylon mesh and backwashing, to resuspend the trapped aggregates. Processing for electron microscopy was carried out in microcentrifuge tubes. The ultrastructural preservation was excellent and the extension of these studies to investigations of not only renal transplantation, but also for diagnosis in human renal diseases of a broad spectrum, is suggested. 相似文献
3.
4.
This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Three experiments investigated the suggestion that a predicted or primed stimulus commands less processing and consequently elicits a weaker CR than a stimulus that is not primed. In each experiment rats received initial training in which the presentation of each of 2 serial compounds, A-X and B-Y, was followed by the delivery of food. Subsequently, X's capacity to elicit the CR, approaching the site of food delivery, was assessed when X was preceded by Stimulus A (i.e., primed) or was presented after Stimulus B. Stimulus X elicited a more vigorous response when it was presented after B than when it followed A. These results show that the ability of one event to elicit its CR is reduced if its presentation has been predicted by some other event. This negative priming effect supports one aspect of A. R. Wagner's (1981) model of Pavlovian conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
Marina Fomina Geoffrey M Gadd 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(1):23-34
The sorption of toxic metals by fungal mycelia grown in clay‐containing medium is reported in this work. Biomass of melanin‐producing microfungi of the genus Cladosporium (C cladosporioides, C resinae and C herbarum) and Aureobasidium pullulans, clay minerals and fungal mycelia grown in clay‐containing medium were compared for their equilibrium Cu and Cd uptake from pH‐buffered solutions using experimental sorption isotherms. Bentonite (Cherkassy) in the natural form was shown to be the best Cu sorbent compared with the other clays and clay minerals tested. Cu sorption isotherms fitted the Langmuir sorption model for all cases. Comparison of Cu and Cd uptake for biomass and bentonite showed a lower biomass uptake capacity but a considerably higher affinity of the biosorbent for the solute. The presence of kaolinite and palygorskite in the medium generally reduced both Cu and Cd sorption capacity and the metal‐binding ability of the fungal–clay mixtures. In contrast, addition of bentonite into the medium did not appreciably alter the Cd sorption ability but increased the sorption of Cu by A pullulans and C cladosporioides grown in this medium. A common feature for all fungi grown in the presence of bentonite was an increase in the Cu sorption capacity (Qmax) of the biomineral sorbents and a reduction in their affinity (Langmuir parameter b) compared with control biomass. A difference between predicted and experimental data obtained for biomass grown on bentonite medium was also observed. The connection between the sorption capacity of biomass grown in clay‐containing medium, mycelial morphology and the structure of fungal pellets is discussed and a mechanism for the changed sorption capacity of the combined biomineral sorbents is proposed which involves blocking or modification of binding sites on biotic and abiotic components of the ‘biomineral’ association. © 2002 Society of Chemical Industry 相似文献
7.
Kevin E. Spaulding Geoffrey J. Woolfe Rajan L. Joshi 《Color research and application》2003,28(4):251-266
Image sources, such as digital camera captures and photographic negatives, typically have more information than can be reproduced on a photographic print or a video display. The information that is lost during the tone/color rendering process relates to both the extended dynamic range and color gamut of the original scene. In conventional photographic systems, most of this additional information is archived on the photographic negative and can be accessed by adjusting the way the negative is printed. However, most digital imaging systems have traditionally archived only a rendered video RGB image. As a result, it is not possible to make the same sorts of image manipulations that historically have been possible with conventional photographic systems. This suggests that there would be an advantage to storing images using an extended dynamic range/color gamut color encoding. However, because of file compatibility issues, digital imaging systems that store images using color encoding other than a standard video RGB representation (e.g., sRGB) would be significantly disadvantaged in the marketplace. In this article, we describe a solution that has been developed to maintain compatibility with existing file formats and software applications, while simultaneously retaining the extended dynamic range and color gamut information associated with the original scenes. With this approach, the input raw digital camera image or film scan is first transformed to the scene‐referred ERIMM RGB color encoding. Next, a rendered sRGB image is formed in the usual way and stored in a conventional image file (e.g., a standard JPEG file). A residual image representing the difference between the original extended dynamic range image and the final rendered image is formed and stored in the image file using proprietary metadata tags. This provides a mechanism for archiving the extended dynamic range/color gamut information, which is normally discarded during the rendering process, without sacrificing interoperability. Appropriately enabled applications can decode the residual image metadata and use it to reconstruct the ERIMM RGB image, whereas applications that are not aware of the metadata will ignore it and only have access to the sRGB image. The residual image is formed such that it will have negligible pixel values for those portions of the image that lie within the sRGB gamut, and will therefore be highly compressible. Tests on a population of 950 real customer images have demonstrated that the extended dynamic range scene information can be stored with an average file size overhead of about 8% compared to the sRGB images alone. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 251–266, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10160 相似文献
8.
Ian G. Richardson Adrian R. Brough Rik Brydson Geoffrey W. Groves Christopher M. Dobson 《Journal of the American Ceramic Society》1993,76(9):2285-2288
Solid-state 27 Al and 29 Si magic angle spinning NMR spectroscopy has been combined with electron energy loss spectroscopy carried out in the transmission electron microscope to determine the location of Al substituting in a semicrystalline C-S-H gel present in a hydrated synthetic slag glass. The gel is found to contain mainly pentameric silicate chains in which the central silicon is substituted by aluminum. 相似文献
9.
Exp I, with 12 male hooded rats, demonstrated that Ss with caudate-putamen lesions exhibited an impairment in the acquisition and reversal of a spatial maze task when compared with unoperated control Ss. Exp II, with 24 Ss, investigated leverpress responding supported by a VI schedule in 3 groups of Ss: a group with caudate-putamen lesions, a group with lesions of the posterior cortex, and an unoperated control group. The presentation of a 0.5-sec, response-contingent light correlated with reinforcement generated an elevated response rate in the 2 operated groups but tended to suppress responding in the control group, perhaps by overshadowing the response–reinforcer relation. Only the group with cortical lesions maintained the elevated rate when the light was uncorrelated with food delivery. Exp III confirmed for these same Ss that caudate-putamen lesions produced a spatial learning deficit. No deficit was observed in the posterior cortex group. It is suggested that caudate-putamen lesions disrupt the mechanism underlying the response–reinforcer association on which spatial maze learning and free operant responding in part depend. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Basicity values have been determined for series of monoazo dyes incorporating a pyrrolidino or a piperidino moiety. In general, the pKa value is found to decrease as the donor capacity of the terminal nitrogen atom decreases.The basicities of the 4'-substituted piperidinoazobenzenes decrease as the electron withdrawing strength of the 4'-substituent increases. However, the pKa values of the related pyrrolidino compounds appear to be insensitive to the substituent. 相似文献