全文获取类型
收费全文 | 1287篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 16篇 |
综合类 | 1篇 |
化学工业 | 259篇 |
金属工艺 | 53篇 |
机械仪表 | 18篇 |
建筑科学 | 24篇 |
矿业工程 | 2篇 |
能源动力 | 20篇 |
轻工业 | 121篇 |
水利工程 | 13篇 |
石油天然气 | 1篇 |
无线电 | 68篇 |
一般工业技术 | 223篇 |
冶金工业 | 335篇 |
原子能技术 | 24篇 |
自动化技术 | 130篇 |
出版年
2023年 | 9篇 |
2021年 | 13篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 27篇 |
2013年 | 47篇 |
2012年 | 45篇 |
2011年 | 52篇 |
2010年 | 40篇 |
2009年 | 36篇 |
2008年 | 47篇 |
2007年 | 37篇 |
2006年 | 39篇 |
2005年 | 34篇 |
2004年 | 38篇 |
2003年 | 34篇 |
2002年 | 32篇 |
2001年 | 20篇 |
2000年 | 22篇 |
1999年 | 27篇 |
1998年 | 101篇 |
1997年 | 64篇 |
1996年 | 40篇 |
1995年 | 25篇 |
1994年 | 38篇 |
1993年 | 31篇 |
1992年 | 16篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 13篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 16篇 |
1976年 | 18篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1972年 | 8篇 |
1971年 | 7篇 |
1970年 | 7篇 |
1966年 | 8篇 |
排序方式: 共有1308条查询结果,搜索用时 86 毫秒
71.
72.
H. P. Röser R. Wattenbach G. V. Schultz 《Journal of Infrared, Millimeter and Terahertz Waves》1983,4(1):1-14
The radiation of optically pumped submillimeter lasers has been investigated using a heterodyne system with a Schottky barrier diode in a quasi optical mixer. The laser frequency, the mode purity and the total linewidth was determined by mixing experiments between two submillimeter lasers. The uncertainty of the measured laser frequency is about 200 kHz. 相似文献
73.
Capillary electrophoresis/electrospray ionization-mass spectrometry (CE/ESI-MS) was applied to the analysis of underivatized amino acids and the separation of their D/L-enantiomers. Under full-scan mode, all standard protein amino acids were separated and detected at low-femtomole levels using a 130-cm-long, 20-microm-i.d., 150-microm-o.d. underivatized fused-silica capillary with 1 M formic acid as the background electrolyte. The CE/ESI-MS technique was also applied to the separation of L-arginine from L-canavanine (a close analogue of arginine where the terminal methylene linked to the guanidine group of arginine is replaced by an oxygen atom) in a complex mixture containing all standard protein amino acids. The utility of CE/ESI-MS in the analysis of real-world samples was demonstrated by the identification of two metabolic diseases (PKU and tyrosinemia) through blood analysis with minimal sample preparation. In addition, the on-line separation of 11 underivatized L-amino acids from their D-enantiomers was achieved by using a 30 mM solution of (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as the background electrolyte. 相似文献
74.
A new capillary electrophoresis/mass spectrometry technique is introduced for attomole detection of primary amines (including several neurotransmitters), amino acids, and their d/l enantiomers in one run through the use of a complexation reagent while using only approximately 1 nL of sample. The technique uses underivatized amino acids in conjunction with an underivatized capillary, which significantly reduces cost and analysis time. It was found that when (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TCA, MW 440) was used as the background electrolyte/complexation reagent during the capillary electrophoresis/electrospray ionization-mass spectrometry (CE/ESI-MS) analysis of underivatized amino acids, stable complexes were formed between the amino acids and the 18-C-6-TCA molecules. These complexes, which exhibited high ionization efficiencies, were detectable at attomole levels for most amino acids. The detection limits of the AA/18-C-6-TCA complexes were on the average more than 2 orders of magnitude lower than that of the free amino acids in solution. In addition to lower detection limits under CE/ESI-MS, a solution of 18-C-6-TCA in the concentration range of 5-30 mM provided high separation efficiency for mixtures of l-amino acids as well as mixtures of d/l-amino acids. By using a solution of 18-C-6-TCA as the background electrolyte in conjunction with an underivatized, 130-cm-long, 20-microm-i.d., 150-microm-o.d. fused-silica capillary and by monitoring the m/z range of the amino acid/18-C-6-TCA complexes (m/z 515-700), most of the standard amino acids and many of their enantiomers were separated and detected with high separation efficiency and high sensitivity (nanomolar concentration detection limits) in one run. The solutions of 18-C-6-TCA also worked well as the CE/ESI-MS BGE for low-level detection of several neurotransmitters and some of their d/l enantiomers as well as for the analysis of amino acids at endogenous levels in lysed red blood cells. 相似文献
75.
Jakob PM Wang T Schultz G Hebestreit H Hebestreit A Elfeber M Hahn D Haase A 《Magma (New York, N.Y.)》2002,15(1-3):10-17
The unique characteristics of the human lung arising from low proton density and multiple air-tissue interfaces of the alveoli
cause difficulty in1H lung magnetic resonance imaging. In addition, the dominating signal from sources such as the thoracic muscle and subcutaneous
fat hampers the visualization of the lung parenchyma. In this contribution, an efficient tissue suppression technique is presented
which allows one to significantly enhance lung parenchyma visibility. A short inversion time inversion recovery (STIR) experiment
combined with a magnetization transfer (MT) experiment was used for magnetization preparation in order to suppress the signal
from muscle. A half-Fourier single-shot turbo spin-echo sequence was used as acquisition module. This approach was used to
perform lung anatomical imaging in eight healthy human subjects and five patients withcystic fibrosis. The results obtained demonstrate that with MT-STIR approach high quality human lung images can be obtained and that this
approach has the potential for the evaluation of lung pathologies. 相似文献
76.
Simeon Keates Ray Adams Cathy Bodine Sara Czaja Wayne Gordon Peter Gregor Emily Hacker Vicki Hanson John Kemp Mark Laff Clayton Lewis Michael Pieper John Richards David Rose Anthony Savidis Greg Schultz Paul Snayd Shari Trewin Philip Varker 《Universal Access in the Information Society》2007,5(4):329-339
In October 2005, the IBM Human Ability and Accessibility Center and T.J. Watson Research Center hosted a symposium on “cognitive
and learning difficulties and how they affect access to IT systems”. The central premise of the symposium was the recognition
that cognitive and learning difficulties have a profound impact on a person’s ability to interact with information technology
(IT) systems, but that little support is currently being offered by those systems. By bringing together internationally renowned
experts from a variety of different, but complementary, research fields, the symposium aimed to provide a complete overview
of the issues related to this topic. This paper summarises the discussions and findings of the symposium. 相似文献
77.
We propose a novel approach to cross-lingual language model and translation lexicon adaptation for statistical machine translation
(SMT) based on bilingual latent semantic analysis. Bilingual LSA enables latent topic distributions to be efficiently transferred
across languages by enforcing a one-to-one topic correspondence during training. Using the proposed bilingual LSA framework,
model adaptation can be performed by, first, inferring the topic posterior distribution of the source text and then applying
the inferred distribution to an n-gram language model of the target language and translation lexicon via marginal adaptation. The background phrase table is
enhanced with the additional phrase scores computed using the adapted translation lexicon. The proposed framework also features
rapid bootstrapping of LSA models for new languages based on a source LSA model of another language. Our approach is evaluated
on the Chinese–English MT06 test set using the medium-scale SMT system and the GALE SMT system measured in BLEU and NIST scores.
Improvement in both scores is observed on both systems when the adapted language model and the adapted translation lexicon
are applied individually. When the adapted language model and the adapted translation lexicon are applied simultaneously,
the gain is additive. At the 95% confidence interval of the unadapted baseline system, the gain in both scores is statistically
significant using the medium-scale SMT system, while the gain in the NIST score is statistically significant using the GALE
SMT system. 相似文献
78.
Subramanya Sarma Vadlamani Joerg Eickemeyer Ludwig Schultz Bernhard Holzapfel 《Journal of Materials Science》2007,42(17):7586-7591
The development of strongly cube textured Cu based substrates is important in the cost effective production of long lengths
of high temperature superconducting cables. The present paper reports textures (deformation and recrystallisation) development
in pure Cu, Cu–Al, Cu–Mn (with a solute content of 1–3 at.%) and Cu–35 at.% Ni alloys. 相似文献
79.
Greegor R.B. Parazzoli C.G. Nielsen J.A. Thompson M.A. Tanielian M.H. Vier D.C. Schultz S. Smith D.R. Schurig D. 《Microwaves, Antennas & Propagation, IET》2007,1(1):108-115
Negative index of refraction materials (NIMs) were first postulated by Veselago in 1968 and have recently been realised using structures formed with rings and wires deposited on printed circuit boards. The proof of the existence of negative index of refraction was established using a Snell's law experiment with a wedge. The predicted and measured refraction angles were found to be consistent for a negative index material and in excellent agreement with the theoretical expectations. For microwave lenses NIMs have the advantage of being lighter, having better focusing properties and potentially lower aberrations. Simulation and experimental results on NIM configurations including gradient index of refraction and spherical 3D lenses are presented. Both focusing and beam collimating applications will be considered. These results will be compared to normal positive index of refraction material lenses 相似文献
80.
An undergraduate design project is described in which a free-space optical communications link is constructed. The interest and motivation for the students is achieved by using a visible laser and constructing a complete system by using the digital output of a CD/DVD player and an audio receiver to transmit music over the free-space link. In addition to providing a high-level technical experience, the project also teaches multidisciplinary teamwork and emulates a real working environment; it is relatively low cost, divisible into modules, and adaptable. An overview of the project is included with representative designs and information. 相似文献