全文获取类型
收费全文 | 1530篇 |
免费 | 97篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 23篇 |
综合类 | 10篇 |
化学工业 | 300篇 |
金属工艺 | 37篇 |
机械仪表 | 37篇 |
建筑科学 | 45篇 |
矿业工程 | 1篇 |
能源动力 | 38篇 |
轻工业 | 129篇 |
水利工程 | 11篇 |
石油天然气 | 6篇 |
无线电 | 208篇 |
一般工业技术 | 281篇 |
冶金工业 | 239篇 |
原子能技术 | 9篇 |
自动化技术 | 260篇 |
出版年
2023年 | 13篇 |
2022年 | 34篇 |
2021年 | 52篇 |
2020年 | 29篇 |
2019年 | 38篇 |
2018年 | 46篇 |
2017年 | 52篇 |
2016年 | 49篇 |
2015年 | 54篇 |
2014年 | 52篇 |
2013年 | 92篇 |
2012年 | 74篇 |
2011年 | 76篇 |
2010年 | 65篇 |
2009年 | 69篇 |
2008年 | 80篇 |
2007年 | 66篇 |
2006年 | 58篇 |
2005年 | 32篇 |
2004年 | 41篇 |
2003年 | 38篇 |
2002年 | 27篇 |
2001年 | 41篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 70篇 |
1997年 | 39篇 |
1996年 | 29篇 |
1995年 | 27篇 |
1994年 | 36篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 10篇 |
1976年 | 15篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有1634条查询结果,搜索用时 25 毫秒
101.
An automated fluorescent PCR method for detection of shiga toxin-producing Escherichia coli in foods
S Chen R Xu A Yee KY Wu CN Wang S Read SA De Grandis 《Canadian Metallurgical Quarterly》1998,64(11):4210-4216
An automated fluorescence-based PCR system (a model AG-9600 AmpliSensor analyzer) was investigated to determine whether it could detect Shiga toxin-producing Escherichia coli (STEC). The AmpliSensor PCR assay involves amplification-mediated disruption of a fluorogenic DNA signal duplex (AmpliSensor) that is homologous to conserved target sequences in a 323-bp amplified fragment of Shiga toxin genes stx1, stx2, and stxe. Using the Amplisensor assay, we detected 113 strains of STEC belonging to 50 different serotypes, while 18 strains of non-Shiga-toxin-producing E. coli and 68 strains of other bacteria were not detected. The detection limits of the assay were less than 1 to 5 CFU per PCR mixture when pure cultures of five reference strains were used and 3 CFU per 25 g of food when spiked ground beef samples that were preenriched overnight were used. The performance of the assay was also evaluated by using 53 naturally contaminated meat samples and 48 raw milk samples. Thirty-two STEC-positive samples that were confirmed to be positive by the culture assay were found to be positive when the AmpliSensor assay was used. Nine samples that were found to be positive when the PCR assay was used were culture negative. The system described here is an automated PCR-based system that can be used for detection of all serotypes of STEC in food or clinical samples. 相似文献
102.
It has been widely asserted that low self-esteem causes violence, but laboratory evidence is lacking, and some contrary observations have characterized aggressors as having favorable self-opinions. In 2 studies, both simple self-esteem and narcissism were measured, and then individual participants were given an opportunity to aggress against someone who had insulted them or praised them or against an innocent third person. Self-esteem proved irrelevant to aggression. The combination of narcissism and insult led to exceptionally high levels of aggression toward the source of the insult. Neither form of self-regard affected displaced aggression, which was low in general. These findings contradict the popular view that low self-esteem causes aggression and point instead toward threatened egotism as an important cause. 相似文献
103.
The local strains in unmodified and rubber-modified epoxies under multiaxial stress states were examined. Matrix ductility was varied by using epoxide resins of different epoxide monomer molecular weights. The stress state was altered from a plane strain case to a plane stress case by varying the thickness of the test specimens. It was confirmed that, in the case of unmodified resins, the thinner specimens which experienced nearly uniaxial tensile stress exhibited much higher local strains at failure than the thicker counterparts which experienced highly triaxial tensile stress. Also, the cross-link density was reduced as monomer molecular weight increased, thus the increase in local plastic strain due to the stress state change also became greater. Furthermore, it was found that rubber modification markedly increased the plastic strain to failure, irrespective of the specimen dimensions, and that the extent of this plastic strain increased as cross-link density was lowered. These results are consistent with the concept that the cavitation of rubber particles relieves the initial multiaxial constraint in a thick specimen, induces a stress state closer to plane stress throughout the specimen, and consequently enables the matrix to deform to a larger extent. The results also show clearly that the toughenability of a matrix resin is not independent of the stress state and the matrix ductility. 相似文献
104.
We have used a diagrammatic approach first developed for nonlinear optical calculations of the density operator to obtain expressions for the transition probability in various laser-switched collision processes. Not only do these diagrams considerably simplify the algebra involved in such calculations, but they also afford a clear visualization of the interaction. In particular, pair absorption, laser-switched Raman scattering, and collisionally enhanced hot luminescence and four-wave mixing processes are considered. 相似文献
105.
Protein sizing on a microchip 总被引:6,自引:0,他引:6
We have developed a microfabricated analytical device on a glass chip that performs a protein sizing assay, by integrating the required separation, staining, virtual destaining, and detection steps. To obtain a universal noncovalent fluorescent labeling method, we have combined on-chip dye staining with a novel electrophoretic dilution step. Denatured protein-sodium dodecyl sulfate (SDS) complexes are loaded on a chip and bind a fluorescent dye as the separation begins. At the end of the separation channel, an intersection is used to dilute the SDS below its critical micelle concentration before the detection point. This strongly reduces the background due to dye molecules bound to SDS micelles and also increases the peak amplitude by 1 order of magnitude. Both the on-chip staining and SDS dilution steps occur in the 100-ms time scale and are approximately 10(4) times faster than their conventional counterparts in SDS-PAGE. This represents a much greater speed increase due to microfabrication than has been obtained in other assay steps such as electrophoretic separations. We have designed and tested a microchip capable of sequentially analyzing 11 different samples, with sizing accuracy better than 5% and high sensitivity (30 nM for carbonic anhydrase). 相似文献
106.
107.
Singer Philipp; Boison Detlev; M?hler Hanns; Feldon Joram; Yee Benjamin K. 《Canadian Metallurgical Quarterly》2007,121(5):815
Selective deletion of glycine transporter 1 (GlyT1) in forebrain neurons enhances N-methyl-D-aspartate receptor (NMDAR)-dependent neurotransmission and facilitates associative learning. These effects are attributable to increases in extracellular glycine availability in forebrain neurons due to reduced glycine re-uptake. Using a forebrain- and neuron-specific GlyT1-knockout mouse line (CamKIIαCre; GlyT1tm1.2fl/fI), the authors investigated whether this molecular intervention can affect recognition memory. In a spontaneous object recognition memory test, enhanced preference for a novel object was demonstrated in mutant mice relative to littermate control subjects at a retention interval of 2 hr, but not at 2 min. Furthermore, mutants were responsive to a switch in the relative spatial positions of objects, whereas control subjects were not. These potential procognitive effects were demonstrated against a lack of difference in contextual novelty detection: Mutant and control subjects showed equivalent preference for a novel over a familiar context. Results therefore extend the possible range of potential promnesic effects of specific forebrain neuronal GlyT1 deletion from associative learning to recognition memory and further support the possibility that mnemonic functions can be enhanced by reducing GlyT1 function. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
Tso Yee Fan Ripin D.J. Aggarwal R.L. Ochoa J.R. Bien Chann Tilleman M. Spitzberg J. 《IEEE journal of selected topics in quantum electronics》2007,13(3):448-459
Cryogenically cooled solid-state lasers promise a revolution in power scalability while maintaining a good beam quality because of significant improvements in efficiency and thermo-optic properties. This is particularly true for Yb lasers because of their relatively low quantum defect and relatively broadband absorption even at cryogenic temperatures. Thermo-optic properties of host materials, including thermal conductivity, thermal expansion, and refractive index at low temperature, are reviewed and data presented for YAG (ceramic and single crystal), GGG, GdVO4, and Y2O3. Spectroscopic properties of Yb:YAG and Yb:LiYF4 (YLF) including absorption cross sections, emission cross sections, and fluorescence lifetimes at cryogenic temperatures are characterized. Recent experiments have pushed the power from an end-pumped cryogenically cooled Yb:YAG laser to 455-W continuous-wave output power from 640-W incident pump power at an of M2 1.4. 相似文献
109.
Facile Preparation of Multifunctional WS2/WOx Nanodots for Chelator‐Free 89Zr‐Labeling and In Vivo PET Imaging 下载免费PDF全文
Liang Cheng Anyanee Kamkaew Sida Shen Hector F. Valdovinos Haiyan Sun Reinier Hernandez Shreya Goel Teng Liu Cyrus R. Thompson Todd E. Barnhart Zhuang Liu Weibo Cai 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(41):5750-5758
While position emission tomography (PET) is an important molecular imaging technique for both preclinical research and clinical disease diagnosis/prognosis, chelator‐free radiolabeling has emerged as a promising alternative approach to label biomolecules or nanoprobes in a facile way. Herein, starting from bottom‐up synthesized WS2 nanoflakes, this study fabricates a unique type of WS2/WOx nanodots, which can function as inherent hard oxygen donor for stable radiolabeling with Zirconium‐89 isotope (89Zr). Upon simply mixing, 89Zr can be anchored on the surface of polyethylene glycol (PEG) modified WS2/WOx (WS2/WOx‐PEG) nanodots via a chelator‐free method with surprisingly high labeling yield and great stability. A higher degree of oxidation in the WS2/WOx‐PEG sample (WS2/WOx (0.4)) produces more electron pairs, which would be beneficial for chelator‐free labeling of 89Zr with higher yields, suggesting the importance of surface chemistry and particle composition to the efficiency of chelator‐free radiolabeling. Such 89Zr‐WS2/WOx (0.4)‐PEG nanodots are found to be an excellent PET contrast agent for in vivo imaging of tumors upon intravenous administration, or mapping of draining lymph nodes after local injection. 相似文献
110.
Intrinsically Zirconium‐89 Labeled Gd2O2S:Eu Nanoprobes for In Vivo Positron Emission Tomography and Gamma‐Ray‐Induced Radioluminescence Imaging 下载免费PDF全文