全文获取类型
收费全文 | 951篇 |
免费 | 6篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 959篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 4篇 |
2014年 | 17篇 |
2013年 | 26篇 |
2012年 | 22篇 |
2011年 | 41篇 |
2010年 | 18篇 |
2009年 | 40篇 |
2008年 | 32篇 |
2007年 | 42篇 |
2006年 | 39篇 |
2005年 | 39篇 |
2004年 | 44篇 |
2003年 | 39篇 |
2002年 | 35篇 |
2001年 | 31篇 |
2000年 | 25篇 |
1999年 | 19篇 |
1998年 | 93篇 |
1997年 | 53篇 |
1996年 | 58篇 |
1995年 | 19篇 |
1994年 | 32篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1970年 | 3篇 |
1968年 | 1篇 |
排序方式: 共有959条查询结果,搜索用时 15 毫秒
921.
The influence of martensite content, prestraining and ageing on near-threshold fatigue crack growth in dual-phase (DP) steels was studied. The experiments were performed on fine-grained, commercially available DP-steels with volume fractions of martensite from 2–42 %. No influence of martensite volume fraction on the nominal or effective threshold values was found. Cold deformation prior to testing resulted in a decrease of both the nominal and effective thresholds, other than for DP-steels with a high martensite content where no such influence was found. A subsequent peak-ageing of either the initial or the prestrained conditions did not result in any further changes of the threshold values. Again an exception was found for the DP-steel with high martensite content where combined straining and ageing caused a lowering of the nominal level, leaving the effective value unaffected. The crack closure was determined for all structural variants and related to results from quantitative fractographic measurements. 相似文献
922.
Kylemark P. Karlsson M. Torounidis T. Andrekson P.A. 《Lightwave Technology, Journal of》2007,25(2):612-620
In this paper, we show both theoretically and experimentally that the probability density function of the intensity of an amplified signal by parametric amplifiers subject to a pump with excess noise is highly asymmetric. This is due to the nonlinear relationship between the optical pump power and the parametric gain. Because of this, the relationship between the noise figure (NF) and the bit error rate (BER) is modified, compared with that predicted by the chi2 theory, which is an effect that is notable at large NFs and low BERs. The difference in predicted BER can be of several orders of magnitudes between the correct theory and the chi2 approximation in single-stage parametric amplifiers. We also show that in the limit of many cascaded parametric amplifiers, the statistics of the noise of an amplified optical signal approaches chi2. Furthermore, the BER of a parametric amplifier is generally lower compared with erbium-doped fiber amplifiers for the same NF values if we assume quantum-limited amplification 相似文献
923.
Munich M.E. Pirjanian P. Di Bernardo E. Goncalves L. Karlsson N. Lowe D. 《Robotics & Automation Magazine, IEEE》2006,13(3):72-77
Recent advances in computer vision have given rise to a robust and invariant visual pattern recognition technology that is based on extracting a set of characteristic features from an image. Such features are obtained with the scale invariant feature transform (SIFT) which represents the variations in brightness of the image around the point of interest. Recognition performed with these features has been shown to be quite robust in realistic settings. This paper describes the application of this particular visual pattern recognition (ViPR) technology to a variety of robotics applications: object recognition, navigation, manipulation, and human-machine interaction. The paper also describes the technology in more detail and presents a business case for visual pattern recognition in the field of robotics and automation. 相似文献
924.
Lena Karlsson Thomas Thelin Björn Regnell Patrik Berander Claes Wohlin 《Empirical Software Engineering》2007,12(1):3-33
The process of selecting the right set of requirements for a product release is dependent on how well the organisation succeeds
in prioritising the requirements candidates. This paper describes two consecutive controlled experiments comparing different
requirements prioritisation techniques with the objective of understanding differences in time-consumption, ease of use and
accuracy. The first experiment evaluates Pair-wise comparisons and a variation of the Planning game. As the Planning game
turned out as superior, the second experiment was designed to compare the Planning game to Tool-supported pair-wise comparisons.
The results indicate that the manual pair-wise comparisons is the most time-consuming of the techniques, and also the least
easy to use. Tool-supported pair-wise comparisons is the fastest technique and it is as easy to use as the Planning game.
The techniques do not differ significantly regarding accuracy.
Editor: Daniel Berry 相似文献
925.
Nilsson CL Larsson T Gustafsson E Karlsson KA Davidsson P 《Analytical chemistry》2000,72(9):2148-2153
Helicobacter pylori is an important human gastric pathogen for which the entire genome sequence is known. This microorganism displays a uniquely complex pattern of binding to complex carbohydrates presented on host mucosal surfaces and other tissues, through adhesion molecules (adhesins) on the microbial cell surface. Adhesins and other membrane-associated proteins are important targets for vaccine development. The identification and characterization of cell-surface proteins expressed by H. pylori is a prerequisite for the development of vaccines designed to interfere with bacterial colonization of host tissues. However, identification of membrane proteins is difficult using a traditional proteomics approach employing 2D-PAGE. We have used a novel approach in the identification of microbial proteins that employs a rapid preparative two-dimensional electrophoretic separation followed by mass spectrometry and database searches. No pre-enrichment of bacterial membranes was required. The entire process, from sample preparation to protein identification, can be completed in less than 18 hours, and the presence of proteins can be monitored after both the first- and second-dimensional separations using mass spectrometry. We were able to identify 40 proteins from a detergent-solubilized H. pylori preparation; over one-third of these were membrane or membrane-associated proteins. A functionally characterized low-abundance membrane protein, the Leb-binding adhesin, was found in this group. The use of this rapid 2D electrophoretic separation in proteomic studies of H. pylori is expected to speed up the identification of expressed virulence proteins and vaccine targets in this and other microbial pathogens. 相似文献
926.
Control of post mortem pH decrease in pig muscles: experimental design and testing of animal models 总被引:1,自引:0,他引:1
From a series of experiments aimed at manipulating and relating the resting levels of glycogen and creatine phosphate (CP) in the live muscle four models were selected to induce different rates and extents of pH decrease post mortem in pig muscle. Model A served as the control, animals being slaughtered under minimal stress, in model B animals were subjected to 10 min treadmill exercise at 3.8 km/h immediately prior to stunning, in model C, animals were given 0.2 mg adrenaline/kg live weight 16 h prior to slaughter, and in model D they were given 0.3 mg adrenaline/kg live weight 16 h before slaughter and subjected to 5 min of treadmill exercise immediately before stunning. After slaughter, the decline in pH and temperature post mortem was recorded in M. longissimus dorsi (LD), M. biceps femoris (BF), M. semimembranosus (SM) and M. psoas major (PM) from 1 min to 24 h after bleeding. Significant differences in ultimate pH and the time course of pH decrease were observed, both as an effect of model as well as type of muscle. No differences in ultimate pH between model A and model B were observed in any of the muscles. Ultimate pH in the C and the D models were significantly higher than in A and B. In the B model lower pH values were observed from 1 min to 6 h post bleeding compared to the other three models. No differences in rate of pH decrease were observed between the A and the B models in any of the muscles. Within the A model no differences in ultimate pH between muscles were seen, indicating that the frequently observed differences in ultimate pH are caused by environmental factors rather than by differences in physiological and morphological characteristics. The exercise bouts caused elevated temperatures during the first hour after bleeding (model B and D). The BF muscle in all the models displayed the fastest rate of pH decrease and SM the slowest; a slower rate of temperature decline occurred in the BF than in the SM. 相似文献
927.
Diode-Pumped Er-Yb:Glass Laser Passively Q Switched by Use of Co(2+):MgAl(2)O(4) as a Saturable Absorber 总被引:1,自引:0,他引:1
Karlsson G Pasiskevicius V Laurell F Tellefsen JA Denker B Galagan BI Osiko VV Sverchkov S 《Applied optics》2000,39(33):6188-6192
We report on passively Q-switched operation of a diode-pumped Er-Yb:glass laser with a Co(2+):MgAl(2)O(4) plate as a saturable absorber. Optical pulses with peak power exceeding 2 kW and a pulse length of 2.3 ns have been generated. Single-longitudinal-mode Q-switched operation at 1.53 mum has been obtained by use of the Co(2+):MgAl(2)O(4) plate as an intracavity etalon. A discussion of the optimal Er(3+) concentration as well as optimization of the cavity design is included. 相似文献
928.
Design guidelines of actively mode-locked fiber ring lasers 总被引:1,自引:0,他引:1
This letter presents guidelines of how to design actively mode-locked fiber ring lasers to generate nearly transform-limited soliton pulses. The minimum fiber cavity length and/or dispersion, with which nearly transform-limited soliton pulses can be generated, need to satisfy an additional condition besides two previously known conditions of stability 相似文献
929.
G. Karlsson 《Journal of microscopy》2001,203(3):326-328
Lacey carbon filmed grids interact differently with liquid samples during plunging and subsequent studies in cryo-TEM depending on type and manufacture. One important parameter is the thickness of the film, which is investigated here by ultrathin sectioning. The film thickness of the carbon-Formvar type is found to be 100–200 nm, with the variation of the thickness occurring in the polymer layer. The pure carbon type is found to be 20–30 nm thick. Knowing the thickness makes it easier to choose the optimal type for each cryo-TEM sample. 相似文献
930.
Pontus Cronholm Hanna L. Karlsson Jonas Hedberg Troy A. Lowe Lina Winnberg Karine Elihn Inger Odnevall Wallinder Lennart Möller 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(7):970-982
An increased understanding of nanoparticle toxicity and its impact on human health is essential to enable a safe use of nanoparticles in our society. The aim of this study is to investigate the role of a Trojan horse type mechanism for the toxicity of Ag‐nano and CuO‐nano particles and their corresponding metal ionic species (using CuCl2 and AgNO3), i.e., the importance of the solid particle to mediate cellular uptake and subsequent release of toxic species inside the cell. The human lung cell lines A549 and BEAS‐2B are used and cell death/membrane integrity and DNA damage are investigated by means of trypan blue staining and the comet assay, respectively. Chemical analysis of the cellular dose of copper and silver is performed using atomic absorption spectroscopy. Furthermore, transmission electron microscopy, laser scanning confocal microscopy, and confocal Raman microscopy are employed to study cellular uptake and particle‐cell interactions. The results confirm a high uptake of CuO‐nano and Ag‐nano compared to no, or low, uptake of the soluble salts. CuO‐nano induces both cell death and DNA damage whereas CuCl2 induces no toxicity. The opposite is observed for silver, where Ag‐nano does not cause any toxicity, whereas AgNO3 induces a high level of cell death. In conclusion: CuO‐nano toxicity is predominantly mediated by intracellular uptake and subsequent release of copper ions, whereas no toxicity is observed for Ag‐nano due to low release of silver ions within short time periods. 相似文献