全文获取类型
收费全文 | 484篇 |
免费 | 28篇 |
专业分类
化学工业 | 127篇 |
金属工艺 | 11篇 |
机械仪表 | 9篇 |
建筑科学 | 21篇 |
矿业工程 | 1篇 |
能源动力 | 11篇 |
轻工业 | 56篇 |
水利工程 | 6篇 |
无线电 | 43篇 |
一般工业技术 | 70篇 |
冶金工业 | 85篇 |
原子能技术 | 2篇 |
自动化技术 | 70篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 30篇 |
2012年 | 42篇 |
2011年 | 40篇 |
2010年 | 26篇 |
2009年 | 21篇 |
2008年 | 19篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 17篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 12篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1998年 | 27篇 |
1997年 | 7篇 |
1996年 | 16篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1971年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有512条查询结果,搜索用时 15 毫秒
51.
52.
Marcos A. Couto dos Santos Laure Beaury Jacqueline Derouet Pierre Porcher 《Journal of Alloys and Compounds》1997,250(1-2):336-341
Measurements and simulation of the Zeeman effect in NdOCl and 1%Nd3+:LiYF4 single crystals were carried out. The rare earth local symmetries are C4v and D2d respectively. The isomorphism between these two point groups allows discussion on symmetry assignments. The attention is focused on the 4G7/2 and 4G9/2 levels for NdOCl and on the 4F9/2 and 4G7/2 levels for Nd3+:LiYF4, because they are representative of the general splitting behaviour. We have first revisited the simulation of the energy level scheme in order to deal with confident wave functions. In the experimental magnetic field (B) range we have obtained linear, non-linear, undefined crossing and anti-crossing levels. These features depend on the orientation of B, on the irreducible representation and on the transition closeness. The line widths have been the main obstacle in confirming crossing regions, because their average values are 8 cm−1 at liquid helium temperature. The simulations were performed by introducing the magnetic Hamiltonian μBB(L+geS) in the secular determinant before diagonalisation. A magnetic accidental degeneracy is considered when discussing the crossing and anti-crossing cases. 相似文献
53.
Beatrice Paillassa Benoît Escrig Riadh Dhaou Marie‐Laure Boucheret Caroline Bes 《International Journal of Satellite Communications and Networking》2011,29(6):479-500
This paper proposes new transmission schemes for the delivery of satellite services. In the proposed scenarios, mobile terminals are allowed to forward the signal received from the satellite. This scheme provides spatial diversity just like MIMO transmission schemes. Moreover, the coverage area is extended because masked terminals have an additional opportunity to get the service from neighboring terminals. We use the paradigm of cooperative communications to compare the advantages and limitations of several scenarios in hybrid terrestrial/satellite systems. In particular, we study the following basic transmission scheme: in a first time slot, the satellite sends its signal and, in a second time slot, mobile terrestrial terminals are relaying the satellite signal. An analysis framework is proposed and applied to this cooperation scenario at the destination terminal. The framework is modeling the cooperation process and clearly separates the control part from the data user part. The paper outlines the importance of the control part by evaluating the relay selection policy on a basic hybrid satellite/ad hoc system. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
54.
Magnetization Reversal in CsNiIICrIII(CN)6 Coordination Nanoparticles: Unravelling Surface Anisotropy and Dipolar Interaction Effects
下载免费PDF全文
![点击此处可从《Advanced functional materials》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yoann Prado Sandra Mazerat Eric Rivière Guillaume Rogez Alexandre Gloter Odile Stéphan Laure Catala Talal Mallah 《Advanced functional materials》2014,24(34):5402-5411
CsNiCr(CN)6 coordination nanoparticles with sizes ranging from 6 to 30 nm are highly diluted in an organic polymer matrix. Their static and dynamic magnetic behaviour allows unravelling of surface anisotropy and interparticle dipolar interaction effects. The single magnetic domain critical size is thus evaluated to be around 22 nm with a blocking temperature of 21 K (at ν = 1 Hz) and an effective energy barrier for the reversal of the magnetization of 426 K. 相似文献
55.
The maturation of HIV-1 virions is accomplished through the proteolytic cleavage of Gag and GagPol precursor polyproteins by the viral-encoded protease (PR). Since virions are assembled from unprocessed polyproteins, the intracellular activation of PR must be limited. An experimental system was established that allows the investigation of the intracellular regulation of PR activity. By expressing Gag in trans with the GagPol precursor, downregulation of the intracellular PR activity associated with GagPol was demonstrated. Inhibition of PR activity was dependent upon the context of PR expression. Sequences capable of mediating this inhibition were localized to capsid. A mechanism through which Gag regulates PR activity is proposed whereby the disproportionate synthesis of Gag inhibits the activation of PR in the cytoplasm. Further elucidation of the mechanism of intracellular inhibition of PR activity may facilitate the development of novel PR inhibitors capable of inhibiting viral replication in vivo. 相似文献
56.
Bourgeois P.Y. Lardet-Vieudrin F. Kersale Y. Bazin N. Chaubet M. Giordano V. 《Electronics letters》2004,40(10):605-606
The operation of a microwave cryogenic sapphire resonator oscillator presenting an exceptional frequency stability for long integration times has been demonstrated. Based on a very simple design the 11.5 GHz oscillator presents a fractional frequency instability lower than 6/spl times/10/sup -14/ over one day. 相似文献
57.
M Bourgeois 《Canadian Metallurgical Quarterly》1994,71(1):29-30
A total of 74 patients with suspected discal hernia were studied. To clarify its diagnosis, epidural scintigraphy along with routine studies was used. The established diagnosis was verified during surgery. Carbonic acid laser was applied to 22 patients in addition to the conventional procedures. 相似文献
58.
Gisèle Laure Lecomte Jean Pierre Bonnet Philippe Blanchart 《Journal of Materials Science》2007,42(20):8745-8752
Global thermal transformation of kaolinite–muscovite mixtures containing at most 25 mass % of muscovite was studied up to
1,100 °C. Quantitative and qualitative DTA analysis reveals a great intereaction between the two phylosilicates above 900 °C,
which is characterized by an enhancement of spinodal demixion contribution during the structural reorganization of metakaolinite.
The corresponding enthalpy variation are respectively −32 ± 1 kJ/mol and −15 ± 1 kJ/mol of kaolinite for pure kaolinite and
for the mixture containing 15 mass % of muscovite. This interaction is mainly correlated with the diffusion of potassium ions
from muscovite platelets into metakaolinite structure. The resulting consequence is an enhancement of mullite crystallization
and grain growth at 1,050 °C (earlier than in the case of pure kaolinite mineral). 相似文献
59.
A Lellouch-Tubiana M Bourgeois M Vekemans O Robain 《Canadian Metallurgical Quarterly》1995,90(3):319-322
The quality of clinical trials in Japan has been improving through clear protocol preparation, improvements in methodology, coordinating systems, and so forth. In order to further improvement, the following are discussed: 1) dilemmas regarding adherence of treatment determined by protocol, 2) hospital policy and physician's discretion, 3) systems to support randomized controlled trials in hospital, and 4) systems to help obtain informed consent from subjects. 相似文献
60.
E Kohli L Maurice C Bourgeois JB Bour P Pothier 《Canadian Metallurgical Quarterly》1993,194(1):110-116
Nucleic acid amplification by polymerase chain reaction (PCR) is a very powerful technique in terms of sensitivity but is limited in terms of ability to perform accurate quantitation. While there is a theoretical correlation between copies of input target sequence and those of PCR product, the quantitative nature of this relationship is obscured by unpredictable variations in reaction conditions and by inhibitory and/or stimulatory substances which might be present in sample preparations, especially those derived from biological fluids. To reliably estimate copies of input DNA target from PCR product, we designed a combination of internal and external control systems coupled to DNA/RNA hybridization and enzymatic immunodetection techniques. The internal control system served to monitor amplification efficiency and to correct for the effects of inhibitors or stimuli on the efficiency of the DNA amplification. The assay is quantitative, nonisotopic, and can be widely applied to assessment of the quantity of DNA present in a wide range of preparations. 相似文献