全文获取类型
收费全文 | 1599篇 |
免费 | 76篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 303篇 |
金属工艺 | 13篇 |
机械仪表 | 25篇 |
建筑科学 | 119篇 |
矿业工程 | 3篇 |
能源动力 | 22篇 |
轻工业 | 206篇 |
水利工程 | 14篇 |
石油天然气 | 7篇 |
无线电 | 94篇 |
一般工业技术 | 290篇 |
冶金工业 | 373篇 |
原子能技术 | 3篇 |
自动化技术 | 200篇 |
出版年
2023年 | 16篇 |
2022年 | 27篇 |
2021年 | 59篇 |
2020年 | 33篇 |
2019年 | 55篇 |
2018年 | 30篇 |
2017年 | 51篇 |
2016年 | 55篇 |
2015年 | 46篇 |
2014年 | 58篇 |
2013年 | 113篇 |
2012年 | 73篇 |
2011年 | 122篇 |
2010年 | 91篇 |
2009年 | 82篇 |
2008年 | 105篇 |
2007年 | 70篇 |
2006年 | 63篇 |
2005年 | 54篇 |
2004年 | 40篇 |
2003年 | 49篇 |
2002年 | 41篇 |
2001年 | 23篇 |
2000年 | 16篇 |
1999年 | 22篇 |
1998年 | 36篇 |
1997年 | 35篇 |
1996年 | 28篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1971年 | 3篇 |
1966年 | 3篇 |
1956年 | 4篇 |
排序方式: 共有1677条查询结果,搜索用时 296 毫秒
991.
Russell AP Thomas Alan J Beswick Gabriela Basnakova Rachel Moller Lynne E Macaskie 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2000,75(3):187-195
The use of citrate as a chelating agent in decontamination operations is of environmental concern as it can mobilize toxic heavy metals if discharged into the environment. Many heavy metal‐citrate complexes are recalcitrant to biodegradation. Citrate‐utilizing strains of Pseudomonas aeruginosa and Pseudomonas putida were isolated from a mixed culture which had been maintained with EDTA as the carbon source for 2 years. Citrate (5 mM ) was used as the sole carbon source in medium supplemented with 5 mM Cd, Zn, Cu, Fe, Co, or Ni. Removal of the metals from the medium was promoted by the incorporation of inorganic phosphate as a precipitant, with formation of nickel and cobalt phosphates confirmed by X‐ray powder diffraction analysis. The potential of P putida to biodegrade citrate in a nickel–citrate secondary waste was illustrated using a fill‐and‐draw reactor supplied with effluent from a bioinorganic ion exchange column that had been used previously to concentrate nickel from aqueous solution. © 2000 Society of Chemical Industry 相似文献
992.
Harvey Elizabeth A.; Friedman-Weieneth Julie L.; Miner Amy L.; Bartolomei Rachel J.; Youngwirth Sara D.; Hashim Rebecca L.; Arnold David H. 《Canadian Metallurgical Quarterly》2009,45(6):1497
This study examined the role of ethnicity in untrained observers’ ratings of videotaped mother–child interactions. Participants were Black, White, and Latino undergraduates (N = 109), who rated videotapes of 4 Black, 4 White, and 4 Latino mother–child dyads. Overall, participants of different ethnicities showed more similarities than differences in their ratings of parent–child behavior. There was, however, evidence that participant ethnicity and parent–child ethnicity interacted for ratings of child defiance/negative emotion. Black and White participants differed in their ratings of Black and White children’s defiance/negative emotion, with members of each ethnic group favoring children of their own ethnic group. Intergroup contact appeared to play a role in ratings of parent behavior among Black observers. Black observers who reported low intergroup contact tended to rate Black mothers high on strictness and low on permissiveness. More research is needed to better understand the role of ethnicity in observers’ ratings of parent and child behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Resnicow Ken; Davis Rachel; Zhang Nanhua; Strecher Victor; Tolsma Dennis; Calvi Josephine; Alexander Gwen; Anderson Julia P.; Wiese Cheryl; Cross William E. Jr. 《Canadian Metallurgical Quarterly》2009,28(4):394
Objective: Many targeted interventions have been developed and tested with African Americans (AA); however, AAs are a highly heterogeneous group. One characteristic that varies across AAs is Ethnic Identity (EI). Little research has been conducted on how to incorporate EI into the design of health messages and programs. Design: We tested whether tailoring a print-based fruit and vegetable (F & V) intervention on EI would enhance program impact. AA adults were recruited from two integrated healthcare delivery systems and then randomized to receive three newsletters focused on F & V behavior change over three months. One set of newsletters was tailored only on demographic and social cognitive variables (control condition), whereas the other (experimental condition) was additionally tailored on EI. Main Outcome Measures: The primary outcome for the study was F & V intake, assessed at baseline and three months later using the composite of two brief self-report frequency measures. Results: A total of 560 eligible participants were enrolled, of which 468 provided complete 3-month follow-up data. The experimental group increased their daily mean F & V intake by 1.1 servings compared to .8 servings in the control group (p = .13). Afrocentric experimental group participants showed a 1.4 increase in F & V servings per day compared to a .43 servings per day increase among Afrocentric controls (p 相似文献
994.
Bowers Jeffrey S.; Davis Colin J.; Mattys Sven L.; Damian Markus F.; Hanley Derek 《Canadian Metallurgical Quarterly》2009,35(5):1585
Three picture-word interference (PWI) experiments assessed the extent to which embedded subset words are activated during the identification of spoken superset words (e.g., bone in trombone). Participants named aloud pictures (e.g., brain) while spoken distractors were presented. In the critical condition, superset distractors contained a semantically related embedded word (e.g., charm, which contains arm). In Experiment 1, supersets and subsets differed by one phoneme (charm/arm) and interference effects were obtained when subsets were embedded at the beginning or end of the superset. In Experiment 2, the subsets and supersets differed by three or more phonemes. Interference was obtained for final embedded words aligned with a syllable boundary of the superset (acrobat/bat) but not otherwise (pioneer/ear). In Experiment 3, the size of these PWI effects was compared to the effects obtained with the subset words presented in isolation. The implication of these findings for theories of speech perception and production are discussed. We also consider the possible advantages of the PWI task over cross-modal priming and “visual-world” procedures when studying these issues. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
Rachel O'Reilly Nga Sze Ieong Pei Cheng Chua Malcolm A. Kelland 《Chemical engineering science》2011,(24):6555
Poly(N-vinyl pyrrolidone) (PVP) containing the 5-ring lactam and poly(N-vinyl caprolactam) (PVCap) containing the 7-ring lactam are well-known kinetic hydrate inhibitors (KHIs). For the first time we have synthesised and studied the performance of poly(N-vinyl piperidone) (PVPip), containing the 6-ring lactam, as a kinetic hydrate inhibitor. In the first part of the study we have investigated the ability of PVPip to inhibit the growth of tetrahydrofuran SII hydrate crystals. The results are compared to those of PVP and PVCap. Various polymer molecular weights have been investigated at varying subcoolings. PVPip shows an intermediate growth inhibition performance compared to PVP and PVCap at similar polymer molecular weights. In addition, the weight percentage concentration of polymer needed to achieve complete THF hydrate crystal growth inhibition increases as the polymer molecular weight decreases. 相似文献
996.
Rachel Becker 《Building Simulation》2008,1(4):356-371
The paper formulates some fundamental principles of performance-based design (PBD), suggesting a conceptual framework and
systematic approach suitable for application in most areas of building design, and in the development of simulation tools
and performance test methods required in the design and assessment processes. A schematic algorithm, which has been developed
for the common engineering approach, was helpful in identifying the inter-relation with the required knowledge-based databases
and tools that are needed for proper implementation of PBD. It is also shown that this schematic algorithm can serve not only
as a conceptual model but also as the basic framework for developing or adapting simulation tools that are intended for PBD
and assessment. The last part of the paper demonstrates the application of the fundamental approach in several areas of building
performance (fire safety, acoustics, moisture safety, indoor air quality, and durability), outlining in each area the main
user needs, ensuing performance requirements, and the most significant capabilities required of adequate simulation tools,
with an emphasis on input/output. 相似文献
997.
The programmable array microscope (PAM) uses a spatial light modulator (SLM) to generate an arbitrary pattern of conjugate illumination and detection elements. The SLM dissects the fluorescent light imaged by the objective into a focal conjugate image, Ic, formed by the ‘in-focus’ light, and a nonconjugate image, Inc, formed by the ‘out-of-focus’ light. We discuss two different schemes for confocal imaging using the PAM. In the first, a grid of points is shifted to scan the complete image. The second, faster approach, uses a short tiled pseudorandom sequence of two-dimensional patterns. In the first case, Ic is analogous to a confocal image and Inc to a conventional image minus Ic. In the second case Ic and Inc are the sum and the difference, respectively, of a conventional and a confocal image. The pseudorandom sequence approach requires post-processing to retrieve the confocal part, but generates significantly higher signal levels for an equivalent integration time. 相似文献
998.
Rachel J. Kulchar Bridget R. Denzer Bharvi M. Chavre Mina Takegami Jennifer Patterson 《International journal of molecular sciences》2021,22(19)
Tissue and organ failure has induced immense economic and healthcare concerns across the world. Tissue engineering is an interdisciplinary biomedical approach which aims to address the issues intrinsic to organ donation by providing an alternative strategy to tissue and organ transplantation. This review is specifically focused on cartilage tissue. Cartilage defects cannot readily regenerate, and thus research into tissue engineering approaches is relevant as a potential treatment option. Cells, scaffolds, and growth factors are three components that can be utilized to regenerate new tissue, and in particular recent advances in microparticle technology have excellent potential to revolutionize cartilage tissue regeneration. First, microspheres can be used for drug delivery by injecting them into the cartilage tissue or joint space to reduce pain and stimulate regeneration. They can also be used as controlled release systems within tissue engineering constructs. Additionally, microcarriers can act as a surface for stem cells or chondrocytes to adhere to and expand, generating large amounts of cells, which are necessary for clinically relevant cell therapies. Finally, a newer application of microparticles is to form them together into granular hydrogels to act as scaffolds for tissue engineering or to use in bioprinting. Tissue engineering has the potential to revolutionize the space of cartilage regeneration, but additional research is needed to allow for clinical translation. Microparticles are a key enabling technology in this regard. 相似文献
999.
S. Boateng S.S. Lateef C. Crot D. Motlagh T. Desai A.M. Samarel B. Russell L. Hanley 《Advanced materials (Deerfield Beach, Fla.)》2002,14(6):461-463
Mechanical load and stress are exerted upon heart muscle tissue in vivo, leading to changes in cellular biochemistry and physiology. Understanding the fundamental mechanisms of mechanical transduction at the cellular level requires the development of physiologically relevant models of cells in vitro. Silicone elastomers are widely used as flexible cell culture substrates for in‐vitro cardiac mechano‐biological studies. We describe here the use of peptide binding to and microfabrication of silicone elastomer membranes. We utilize these chemically and morphologically modified silicone membranes as improved flexible cell culture substrates in studies of cardiac mechano‐biology. We also discuss advances in surface modification and microfabrication that promise further development of improved heart cell cultures. 相似文献
1000.
Rachel C. Knopp Kristen K. Baumann Miranda L. Wilson William A. Banks Michelle A. Erickson 《International journal of molecular sciences》2022,23(4)
Systemic inflammation has been implicated in the progression of Alzheimer’s disease (AD); however, less is understood about how existing AD pathology contributes to adverse outcomes following acute inflammatory insults. In the present study, our goal was to determine how AD-associated amyloid beta (Aβ) pathology influences the acute neuroinflammatory and behavioral responses to a moderate systemic inflammatory insult. We treated 16–18-month-old female Tg2576 (Tg) mice, which overproduce human Aβ and develop plaques, and age-matched wild-type (WT) littermate mice with an intraperitoneal injection of 0.33 mg/kg lipopolysaccharide (LPS) or saline. Mice were then evaluated over the next 28 h for sickness/depressive-like behaviors (food intake, weight loss, locomotion, and sucrose preference), systemic inflammation (serum amyloid A, SAA), blood-brain barrier (BBB) disruption, astrogliosis (glial fibrillary acidic protein/GFAP), Aβ, and cytokine levels in the brain. We found that LPS caused a larger reduction in body weight in Tg vs. WT mice, but that other behavioral responses to LPS did not differ by genotype. BBB disruption was not apparent in either genotype following LPS. Concentrations of the systemic inflammatory marker, SAA, in the blood and brain were significantly increased with LPS but did not significantly differ by genotype. GFAP was increased in Tg mice vs. WT but was not significantly affected by LPS in either genotype. Finally, LPS-induced increases of eight cytokines (IL-1β, IL-6, IL-12 (p40), IL-10, IL-17A, MIP-1α/CCL3, MIP-1β/CCL4, and RANTES/CCL5) were found to be significantly higher in Tg mice vs. WT. In summary, our data show that Aβ pathology exacerbates the neuroinflammatory response to LPS and identifies cytokines that are selectively regulated by Aβ. The association of worse neuroinflammation with greater weight loss in Tg mice suggests that Aβ pathology could contribute to poor outcomes following a systemic inflammatory insult. 相似文献