全文获取类型
收费全文 | 43651篇 |
免费 | 1957篇 |
国内免费 | 36篇 |
专业分类
电工技术 | 276篇 |
综合类 | 29篇 |
化学工业 | 7303篇 |
金属工艺 | 720篇 |
机械仪表 | 761篇 |
建筑科学 | 1252篇 |
矿业工程 | 73篇 |
能源动力 | 782篇 |
轻工业 | 5304篇 |
水利工程 | 368篇 |
石油天然气 | 171篇 |
武器工业 | 4篇 |
无线电 | 2273篇 |
一般工业技术 | 7126篇 |
冶金工业 | 13577篇 |
原子能技术 | 193篇 |
自动化技术 | 5432篇 |
出版年
2023年 | 347篇 |
2022年 | 329篇 |
2021年 | 871篇 |
2020年 | 728篇 |
2019年 | 666篇 |
2018年 | 1494篇 |
2017年 | 1493篇 |
2016年 | 1541篇 |
2015年 | 1096篇 |
2014年 | 1390篇 |
2013年 | 2710篇 |
2012年 | 2351篇 |
2011年 | 2164篇 |
2010年 | 1711篇 |
2009年 | 1515篇 |
2008年 | 1781篇 |
2007年 | 1545篇 |
2006年 | 1154篇 |
2005年 | 966篇 |
2004年 | 907篇 |
2003年 | 805篇 |
2002年 | 712篇 |
2001年 | 458篇 |
2000年 | 462篇 |
1999年 | 721篇 |
1998年 | 4402篇 |
1997年 | 2580篇 |
1996年 | 1702篇 |
1995年 | 959篇 |
1994年 | 802篇 |
1993年 | 828篇 |
1992年 | 218篇 |
1991年 | 261篇 |
1990年 | 262篇 |
1989年 | 245篇 |
1988年 | 222篇 |
1987年 | 197篇 |
1986年 | 198篇 |
1985年 | 225篇 |
1984年 | 182篇 |
1983年 | 134篇 |
1982年 | 171篇 |
1981年 | 176篇 |
1980年 | 179篇 |
1979年 | 128篇 |
1978年 | 121篇 |
1977年 | 263篇 |
1976年 | 540篇 |
1975年 | 90篇 |
1973年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
A human fibroblastic cell line transformed by the SV40-T antigen sequence and continuously cultured for 7 months displayed large periodic variations in cell proliferation. This contrasted with other characteristics of this cell line that remained constant: mosaic cell shape, absence of cell contact inhibition, and predominance of a hypodiploid population. Similar fluctuations in proliferative capacity were also found during the long-term growth of a transformed but nonimmortalized human fibroblastic line prior to senescence, and in the established hamster fibroblastic Nil cell line. This growth pattern suggests a recurrent stimulation of growth in these three transformed cell lines. The proliferation pattern from cultured transformed cells may thus be complex and requires further investigation. These variations presumably influence major cell functions. This observation has important implications for the analysis of data from such cell lines. 相似文献
13.
14.
The extinction coefficient ? at 2.9 μm for OH in fluoride glasses is measured by determining the amount of HF evolved during heating of the glass under steam and the corresponding intensity of the OH absorption band. This coefficient is respectively equal to 31 litre mole?1 cm?1 for BTYbZ glass (15 BaF2 - 29 ThF4 - 28 YbF3 - 28 ZnF2) and 19.5 litre mole?1 cm?1 for BALLA glass (34 BaF2 - 57 ZrF4 - 4 AlF3 - 5 LaF3). 相似文献
15.
There are some foods that contain mutagenic or carcinogenic agents, some of which occur naturally and others that may be formed during preparation or cooking. Several foods such as legumes, also contain natural antimutagens and/or anticarcinogens. Lupine is one such legume that contains high amounts of protein (40%) and oils (14%). About 90 species of lupine have been reported throughout Mexico. However, the use of this crop as a source of food has been limited by the presence of antinutritional agents such as phenolic compounds (PC), carbohydrates (CH) and quinolizidinic alkaloids (Qas). It has also been suggested that consuming these compounds can affect human health and may even reduce the risk of disease. The objective of this work was to determine the effect of PC, CH and Qas, isolated and quantified from Lupinus campestris on the mutagenicity of 1-nitropyrene (1-NP) as a model mutagen and we used the Salmonella typhimurium tester strain YG1024 by the Kado microsuspension method. The results indicate that L. campestris seeds have 11 mg (+)catechin equivalent g(-1) seed coat; 120.3 mg g(-1) seeds and 2.13 mg g(-1) seeds of PC, CH and Qas, respectively. 1-NP mutagenicity was inhibited by 86% for PC, 76% for CH and 75% for Qas at concentrations of 200, 512 and 13.6 microg/tube, respectively. 相似文献
16.
Daniel X. Gouveia Odair P. Ferreira Antonio G. Souza Filho M. G. da Silva J. A. C. de Paiva Oswaldo L. Alves Josué Mendes Filho 《Journal of Materials Science》2007,42(2):534-538
The thermal decomposition properties of Mg–Fe hydrotalcites were studied through in situ 57Fe Mössbauer spectroscopy and in situ X-ray diffraction. Abrupt changes in the quadrupolar splitting measured in the Mössbauer spectra revealed a phase transition from the starting lamellar structure to a new crystalline arrangement. By analyzing the Mössbauer parameters we show that the material is highly disordered in the 300–400 °C temperature range. This hypothesis is confirmed by the X-ray results whose diffractograms indicated the collapse of the lamellar structure and the formation of a solid solution. 相似文献
17.
Mamiko Hori Cécile Pagnoux Jean-François Baumard Masayuki Nogami 《Journal of Materials Science》2007,42(1):80-86
A new method is proposed to produce gold nanoparticles (GNP) by in situ reduction of a gold salt dissolved in water. The reducing
agent used is Tiron instead of the citrate anion most often mentioned in literature. The influence of various parameters has
been investigated, such as the content of Tiron with respect to that of the precursor of gold HAuCl4, or the initial pH of the solution after mixing of reactants. It is shown that Tiron also exerts a positive influence as
a dispersant, which impedes agglomeration of gold nanoparticles. The typical average size of GNP synthesized in the present
work is close to 7 nm. 相似文献
18.
David Alleysson Sabine Süsstrunk Jeanny Hérault 《IEEE transactions on image processing》2005,14(4):439-449
There is an analogy between single-chip color cameras and the human visual system in that these two systems acquire only one limited wavelength sensitivity band per spatial location. We have exploited this analogy, defining a model that characterizes a one-color per spatial position image as a coding into luminance and chrominance of the corresponding three colors per spatial position image. Luminance is defined with full spatial resolution while chrominance contains subsampled opponent colors. Moreover, luminance and chrominance follow a particular arrangement in the Fourier domain, allowing for demosaicing by spatial frequency filtering. This model shows that visual artifacts after demosaicing are due to aliasing between luminance and chrominance and could be solved using a preprocessing filter. This approach also gives new insights for the representation of single-color per spatial location images and enables formal and controllable procedures to design demosaicing algorithms that perform well compared to concurrent approaches, as demonstrated by experiments. 相似文献
19.
This publication consists of an analysis and a synthesis by the amplitude law of linear and planar ring printed antennas array. The analysis of the structure is based on the modified cavity model which allows taking into account the fringing fields effects. The synthesis problem is solved by the simulated annealing method based on a random process research controlled by temperature parameter. The feeding network amplitude permitting to produce an optimal radiation pattern is then given. Various synthesis results for linear and planar arrays are presented. 相似文献
20.
O Bernard B Chachuat A Hélias B Le Dantec B Sialve J-P Steyer L Lardon P Neveu S Lambert J Gallop M Dixon P Ratini A Quintabà S Frattesi J M Lema E Roca G Ruiz J Rodriguez A Franco P Vanrolleghem U Zaher D J W De Pauw K De Neve K Lievens D Dochaine O Schoefs H Fibrianto R Farina V Alcaraz Gonzalez V Gonzalez Alvarez P Lemaire J A Martinez F Esandi O Duclaud J F Lavigne 《Water science and technology》2005,52(1-2):457-464
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem. 相似文献