全文获取类型
收费全文 | 5235篇 |
免费 | 240篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 70篇 |
综合类 | 12篇 |
化学工业 | 1174篇 |
金属工艺 | 138篇 |
机械仪表 | 76篇 |
建筑科学 | 186篇 |
矿业工程 | 33篇 |
能源动力 | 108篇 |
轻工业 | 537篇 |
水利工程 | 40篇 |
石油天然气 | 14篇 |
无线电 | 414篇 |
一般工业技术 | 959篇 |
冶金工业 | 1114篇 |
原子能技术 | 42篇 |
自动化技术 | 564篇 |
出版年
2023年 | 48篇 |
2022年 | 53篇 |
2021年 | 215篇 |
2020年 | 108篇 |
2019年 | 115篇 |
2018年 | 143篇 |
2017年 | 117篇 |
2016年 | 139篇 |
2015年 | 119篇 |
2014年 | 149篇 |
2013年 | 298篇 |
2012年 | 227篇 |
2011年 | 296篇 |
2010年 | 207篇 |
2009年 | 192篇 |
2008年 | 197篇 |
2007年 | 177篇 |
2006年 | 179篇 |
2005年 | 139篇 |
2004年 | 126篇 |
2003年 | 120篇 |
2002年 | 121篇 |
2001年 | 88篇 |
2000年 | 84篇 |
1999年 | 87篇 |
1998年 | 278篇 |
1997年 | 191篇 |
1996年 | 150篇 |
1995年 | 92篇 |
1994年 | 98篇 |
1993年 | 95篇 |
1992年 | 55篇 |
1991年 | 39篇 |
1990年 | 43篇 |
1989年 | 57篇 |
1988年 | 42篇 |
1987年 | 35篇 |
1986年 | 35篇 |
1985年 | 35篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 28篇 |
1980年 | 18篇 |
1979年 | 27篇 |
1978年 | 30篇 |
1977年 | 34篇 |
1976年 | 67篇 |
1975年 | 29篇 |
1974年 | 19篇 |
排序方式: 共有5481条查询结果,搜索用时 15 毫秒
991.
Philipp Rahe Markus Kittelmann Julia L. Neff Markus Nimmrich Michael Reichling Philipp Maass Angelika Kühnle 《Advanced materials (Deerfield Beach, Fla.)》2013,25(29):3948-3956
Molecular self‐assembly constitutes a versatile strategy for creating functional structures on surfaces. Tuning the subtle balance between intermolecular and molecule‐surface interactions allows structure formation to be tailored at the single‐molecule level. While metal surfaces usually exhibit interaction strengths in an energy range that favors molecular self‐assembly, dielectric surfaces having low surface energies often lack sufficient interactions with adsorbed molecules. As a consequence, application‐relevant, bulk insulating materials pose significant challenges when considering them as supporting substrates for molecular self‐assembly. Here, the current status of molecular self‐assembly on surfaces of wide‐bandgap dielectric crystals, investigated under ultrahigh vacuum conditions at room temperature, is reviewed. To address the major issues currently limiting the applicability of molecular self‐assembly principles in the case of dielectric surfaces, a systematic discussion of general strategies is provided for anchoring organic molecules to bulk insulating materials. 相似文献
992.
Operations managers rely on the purchasing function to obtain production inputs from suppliers and to ensure supplier performance. The link between supplier development activities performed by buying firms with their suppliers, in terms of operational outcomes and impact on competitive advantage for the buying firm has been well documented. However, a buying firm should, prior to setting up a supplier development program and investing in supplier development activities, establish goals it wants to achieve and determine how to achieve these goals. Until now, supplier development goals in general and their relationship with supplier development activities have received little research attention. The results from this empirical study suggest that the relationship between the goal to improve a supplier's capabilities and knowledge transfer from the buyer to the supplier firm is moderated by the degree of human interaction. Buying firms pursuing the strategy to improve supplier capabilities rely more intensively on training and co-location of buyer and supplier employees to leverage the knowledge transfer to the supplier firm. 相似文献
993.
994.
Kausik Umanath Mohammed Sika Robert Niecestro Carolyn Connelly Gerald Schulman Mark J. Koury Julia B. Lewis Jamie P. Dwyer Collaborative Study Group 《Hemodialysis international. International Symposium on Home Hemodialysis》2013,17(1):67-74
Chronic kidney disease associated mineral and bone disorders arise as a result of aberrant bone mineral metabolism in patients with advancing levels of renal dysfunction and end‐stage renal disease. One of the cornerstones of treatment is the use of phosphate‐binding agents. We describe the rationale and study design for a clinical trial to assess the safety and efficacy of ferric citrate as a phosphate binder. This trial is a three‐period, international, multicenter, randomized, controlled clinical trial to assess the safety and efficacy of ferric citrate as a phosphate binder, consisting of a 2‐week washout period, a 52‐week safety assessment period in which subjects are randomized to ferric citrate or active control, and a 4‐week efficacy assessment period in which subjects randomized to ferric citrate in the safety assessment period are randomized to ferric citrate or placebo. Eligible subjects include end‐stage renal disease patients who have been treated with thrice‐weekly hemodialysis or peritoneal dialysis for at least 3 months in dialysis clinics in the United States and Israel. Primary outcome measure will be the effect of ferric citrate vs. placebo on the change in serum phosphorus. Safety assessments will be performed by monitoring adverse events, concomitant medication use, and sequential blood chemistries (including iron parameters, phosphorus, and calcium). This three‐period trial will assess the efficacy of ferric citrate as a phosphate binder. If proven safe and efficacious, ferric citrate will likely provide an additional phosphate binder to treat chronic kidney disease associated mineral and bone disorders. 相似文献
995.
996.
Janine Pfetzing-Micklich Christoph Somsen Antonin Dlouhy Christoph Begau Alexander Hartmaier Martin F.-X. Wagner Gunther Eggeler 《Acta Materialia》2013,61(2):602-616
We use a nanoindenter with a Berkovich tip to study local mechanical properties of two polycrystalline intermetallics with a B2 crystal structure, NiAl and NiTi. We use orientation imaging scanning electron microscopy to select a relevant number of grains with appropriate sizes and surface normals parallel to 〈0 0 1〉, 〈1 0 1〉 and 〈1 1 1〉. As a striking new result, we find a strong crystallographic orientation dependence for NiTi. This anisotropy is less pronounced in the case of NiAl. For NiTi, the indentation force required to impose a specific indentation depth is highest for indentation experiments performed in the 〈0 0 1〉 direction and lowest along the 〈1 1 1〉 direction. We consider transmission electron microscopy results from cross-sections below the indents and use molecular dynamics simulations and resolved shear stress calculations to discuss how this difference can be accounted for in terms of elementary deformation and transformation processes, related to dislocation plasticity (NiAl and NiTi), and in terms of the stress-induced formation and growth of martensite (NiTi). Our results show that the crystallographic anisotropy during nanoindentation of NiTi is governed by the orientation dependence of the martensitic transformation; dislocation plasticity appears to be less important. 相似文献
997.
Despite significant interest on the topic of knowledge workers, the understanding of how they influence certain aspects of firm innovativeness remains limited. In particular, while different types of knowledge workers exist, their particular synergistic effects on new and improved product development within smaller firms has received less attention. Drawing on the knowledge-based view (KBV), we posit that innovation strategy plays an instrumental role in linking the effects of knowledge workers, thereby leading to greater product development outcomes from different types of knowledge workers. Moreover, some suggest that beyond a certain point, there is a diminishing return to increasing the proportion of knowledge workers in an organisation; however, the basis of this finding is within larger firms. This study investigates whether high-level (e.g. engineers and scientists) and low-level (e.g. technicians and machine operators) knowledge workers exert varying effects on performance in terms of new and improved product development. Data from 205 small and medium-sized high-tech manufacturing firms provide support that distinguishing among types of knowledge workers is important given that they impact new and improved product development differently. Furthermore, innovation strategy plays a synergistic role, positively mediating the effects of different types of knowledge workers on innovation outcomes. 相似文献
998.
Hallah Ahmad Alyosef André Eilert Julia Welscher Suzan S. Ibrahim Reinhard Denecke Wilhelm Schwieger 《Particulate Science and Technology》2013,31(5):524-532
This study presents two routes to produce amorphous silica from an Egyptian rice husk under conditions optimized for least environmental impact and low cost. The first route includes thoroughly washing of the husk sample with water, dry milling and leaching with citric acid. The leaching process was applied in two stages, that is, at 323 K for 180 min and then at 353 K for 60 min. After washing and drying, the leached sample was subjected to a heat treatment in a muffles furnace at four sequential steps. The second route includes all the previously mentioned steps, except the citric acid leaching. The final products were characterized using x-ray fluorescence analysis, carbon content analysis, x-ray diffraction, differential thermal analysis, nitrogen adsorption, mercury intrusion, and scanning electron microscopy. The results show that the citric acid leaching has many advantages with respect to silica yield and porosity as well. 相似文献
999.
Dietz J Koch J Kaur A Raja C Stein S Grez M Pustowka A Mensch S Ferner J Möller L Bannert N Tampé R Divita G Mély Y Schwalbe H Dietrich U 《ChemMedChem》2008,3(5):749-755
The interaction of the nucleocapsid NCp7 of the human immunodeficiency virus type 1 (HIV-1) Gag polyprotein with the RNA packaging signal Psi ensures specific encapsidation of the dimeric full length viral genome into nascent virus particles. Being an essential step in the HIV-1 replication cycle, specific genome encapsidation represents a promising target for therapeutic intervention. We previously selected peptides binding to HIV-1 Psi-RNA or stem loops (SL) thereof by phage display. Herein, we describe synthesis of peptide variants of the consensus HWWPWW motif on membrane supports to optimize Psi-RNA binding. The optimized peptide, psi-pepB, was characterized in detail with respect to its conformation and binding properties for the SL3 of the Psi packaging signal by NMR and tryptophan fluorescence quenching. Functional analysis revealed that psi-pepB caused a strong reduction of virus release by infected cells as monitored by reduced transduction efficiencies, capsid p24 antigen levels, and electron microscopy. Thus, this peptide shows antiviral activity and could serve as a lead compound to develop new drugs targeting HIV-1. 相似文献
1000.
Douglas L. Schulz Robert A. Sailer Chris Braun Andrew Wagner Natalie Klaverkamp Kevin Mattson Joseph Sandstrom David Bunzow Scott Payne Jie He Jun Li Bret Chisholm 《Progress in Organic Coatings》2008
A trimethylsilane-based coating was investigated as a pretreatment for Al-2024 T3 in a novel Mg-rich primer corrosion prevention system. SiC-based thin films were deposited onto Al substrates by plasma-enhanced chemical vapor deposition (PECVD). A screening study of the pressure (P) dependence of films deposited at 350 °C showed an increase in growth rate from 0.6 to 1.9 Torr. A second screening study where P was fixed at 1.9 Torr and temperature (T) was varied from 125 to 550 °C showed decreasing growth rates with increasing temperature with an apparent transition around 300 °C. Electrochemical impedance spectroscopy (EIS) of the SiC-based films on Al-2024 after exposure to a corrosive environment (i.e., dilute Harrison solution) indicated that samples coated using SiC-based films exhibit higher low frequency impedance (i.e., 100–1000× higher) than bare Al-2024 with open circuit potential remaining 0.1 V higher for the former suggesting the SiC-based films slow the corrosion process. A Mg-rich primer was coated onto the SiC on Al-2024 with the galvanic function of the system determined by EIS. As compared to SiC on Al-2024, a similar behavior for the low frequency impedance was observed for the Mg-rich primer-coated samples with some films exhibiting 1E + 8 Ω at 0.1 Hz indicating a strong barrier property. Initial gas jet erosion using acrylic media indicates the Mg-rich primer coatings are removed in preference to the Si–C films—the first step toward demonstrating a permanent pretreatment. When successfully developed and optimized, the value of such a hard, protective coating is the reduction of a three-component coatings system (i.e., pretreatment, primer, and topcoat) to a two-component system (i.e., primer and topcoat). 相似文献