全文获取类型
收费全文 | 1576篇 |
免费 | 73篇 |
国内免费 | 5篇 |
学科分类
工业技术 | 1654篇 |
出版年
2023年 | 25篇 |
2021年 | 40篇 |
2020年 | 26篇 |
2019年 | 25篇 |
2018年 | 33篇 |
2017年 | 21篇 |
2016年 | 42篇 |
2015年 | 35篇 |
2014年 | 50篇 |
2013年 | 53篇 |
2012年 | 57篇 |
2011年 | 92篇 |
2010年 | 69篇 |
2009年 | 58篇 |
2008年 | 77篇 |
2007年 | 48篇 |
2006年 | 53篇 |
2005年 | 39篇 |
2004年 | 35篇 |
2003年 | 32篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 22篇 |
1998年 | 112篇 |
1997年 | 62篇 |
1996年 | 37篇 |
1995年 | 33篇 |
1994年 | 28篇 |
1993年 | 33篇 |
1992年 | 14篇 |
1991年 | 26篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 19篇 |
1985年 | 16篇 |
1984年 | 27篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1977年 | 10篇 |
1976年 | 27篇 |
1975年 | 18篇 |
1974年 | 10篇 |
1972年 | 9篇 |
1942年 | 6篇 |
排序方式: 共有1654条查询结果,搜索用时 15 毫秒
1.
2.
Pavel Strunz Debashis Mukherji Přemysl Beran Ralph Gilles Lukas Karge Michael Hofmann Markus Hoelzel Joachim Rösler Gergely Farkas 《Metals and Materials International》2018,24(5):934-944
An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr2Re3 type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content. 相似文献
3.
ABSTRACTChebyshev interpolation is a highly effective, intensively studied method and enjoys excellent numerical properties which provides tremendous application potential in mathematical finance. The interpolation nodes are known beforehand, implementation is straightforward and the method is numerically stable. For efficiency, a sharp error bound is essential, in particular for high-dimensional applications. For tensorized Chebyshev interpolation, we present an error bound that improves existing results significantly. 相似文献
4.
Dr. Kathrin Schindl Dr. Deepika Sharma Prof. Dr. Dieter Spiteller 《Chembiochem : a European journal of chemical biology》2020,21(21):3151-3157
When Streptomyces violaceoruber grows together with Streptomyces sp. MG7-G1, it reacts with strongly induced droplet production on its aerial mycelium. Initially the metabolite profile of droplets from S. violaceoruber in co-culture with Streptomyces sp. MG7-G1 was compared to samples from S. violaceoruber in single-culture by using high-performance liquid chromatography-mass spectrometry (HPLC-MS). Then, the exudate from agar plates of co-cultures and single cultures (after freezing and thawing) was also analysed. Several compounds were only observed when S. violaceoruber was grown in co-culture. Based on their high-resolution ESI mass spectra and their comparable retention times to the calcium-dependent antibiotics (CDAs) produced by S. violaceoruber, the new compounds were suspected to be deacylated calcium-dependent antibiotics (daCDAs), lacking the 2,3-epoxyhexanoyl residue of CDAs. This was verified by detailed analysis of the MS/MS spectra of the daCDAs in comparison to the CDAs. The major CDA compounds present in calcium ion-supplemented agar medium of co-cultures were daCDAs, thus suggesting that Streptomyces sp. MG7-G1 expresses a deacylase that degrades CDAs. 相似文献
5.
This paper does two main contributions to 2D time-dependent vector field topology. First, we present a technique for robust, accurate, and efficient extraction of distinguished hyperbolic trajectories (DHT), the generative structures of 2D time-dependent vector field topology. It is based on refinement of initial candidate curves. In contrast to previous approaches, it is robust because the refinement converges for reasonably close initial candidates, it is accurate due to its adaptive scheme, and it is efficient due to its high convergence speed. Second, we provide a detailed evaluation and discussion of previous approaches for the extraction of DHTs and time-dependent vector field topology in general. We demonstrate the utility of our approach using analytical flows, as well as data from computational fluid dynamics. 相似文献
6.
With the emergence of distributed ledger technology (DLT), numerous practitioners and researchers have proclaimed its beneficial impact on supply chain transactions in the future. However, the vast majority of DLT initiatives are discontinued after a short period. With the full potential of DLT laying far down the road, especially managers in supply chain management (SCM) seek for short-term cost-saving effects of DLT in order to achieve long-term benefits of DLT in the future. However, the extant research has bypassed grounding long-term as well as short-term effects of DLT on supply chain transaction with empirical data. We address this shortcoming, following an abductive research approach and combining empirical data from a multiple case study design with the corresponding literature. Our study reveals that the effects of DLT on supply chain transactions are two-sided. We found six effects of DLT solutions that have a cost-reducing or cost avoidance impact on supply chain transactions. In addition, we found two effects that change the power distribution between buyers and suppliers in transactions and a single effect that reduces the dependency of supply chain transactions on third parties. While cost-reducing and avoidance as well as dependency-reducing effects are positive effects, the change in power distribution might come with disadvantages. With these findings, the paper provides the first empirical evidence of the impact of DLT on supply chain transactions, which will enable managers to improve their assessment of DLT usage in supply chains. 相似文献
7.
8.
Athanassios Ziogas Christian Hofmann Sebastian Baranyai Patrick Löb Gunther Kolb 《化学,工程师,技术》2020,92(5):513-524
A novel flexible electrochemical microreactor has been developed. Flexibility is reached by a modular design, suitability for a broad process parameter range including high pressure operation, and accessibility of production scale. Selected reactor aspects have been validated by applying the reactor to three different electrosyntheses: synthesis of tailor-made mixtures of paraffins by Kolbe electrolysis, cation flow method, and synthesis of peroxodicarbonate. High conversion rates, yields, selectivities, and Faraday efficiency levels have been observed, showing precise process control. 相似文献
9.
Digitally reconstructing Van Gogh's Field with Irises near Arles part 3: Determining the original colors 下载免费PDF全文
Eric Kirchner Ivo van der Lans Frank Ligterink Muriel Geldof Luc Megens Teio Meedendorp Kathrin Pilz Ella Hendriks 《Color research and application》2018,43(3):311-327
In earlier articles, we determined the spatial distributions and concentrations of all pigments used by Van Gogh in his painting Field with Irises near Arles. The colors of some pigments are expected to have changed over time, especially those of chrome yellow, cochineal, and eosin lake. For all pigments in this painting, we made physical paint reconstructions by following historical sources on raw materials and production processes, and we determined their optical properties. We combined this with pigment concentration maps to reconstruct the original colors of the painting digitally. When substituting the reconstruction paints into the calculations, we found that technical‐scientific data was not sufficient to resolve several issues. In those cases, discussions within the broad interdisciplinary team allowed us to make informed decisions. These issues refer to the representation of the sky area, and the original contributions of the red lake pigments to local colors. The digitally reconstructed colors of the painting show that due to discoloring of red lake pigments, the irises in the field have changed from a warm purple to purplish blue, and many pink spots in the field have turned to white. The range of yellows in the field has decreased and partly turned to dark brown. The digital reconstruction gives a better understanding of the color scheme used by Van Gogh when compared to remarks the artist made in letters when describing this painting. Also, the original color composition is seen to be aligned with color theories on which Van Gogh based his work. 相似文献
10.
Anat Akiva Johanna Melke Sana Ansari Nalan Liv Robin van der Meijden Merijn van Erp Feihu Zhao Merula Stout Wouter H. Nijhuis Cilia de Heus Claudia Muñiz Ortera Job Fermie Judith Klumperman Keita Ito Nico Sommerdijk Sandra Hofmann 《Advanced functional materials》2021,31(17):2010524
Bone formation (osteogenesis) is a complex process in which cellular differentiation and the generation of a mineralized organic matrix are synchronized to produce a hybrid hierarchical architecture. To study the mechanisms of osteogenesis in health and disease, there is a great need for functional model systems that capture in parallel, both cellular and matrix formation processes. Stem cell-based organoids are promising as functional, self-organizing 3D in vitro models for studying the physiology and pathology of various tissues. However, for human bone, no such functional model system is yet available. This study reports the in vitro differentiation of human bone marrow stromal cells into a functional 3D self-organizing co-culture of osteoblasts and osteocytes, creating an organoid for early stage bone (woven bone) formation. It demonstrates the formation of an organoid where osteocytes are embedded within the collagen matrix that is produced by the osteoblasts and mineralized under biological control. Alike in in vivo osteocytes, the embedded osteocytes show network formation and communication via expression of sclerostin. The current system forms the most complete 3D living in vitro model system to investigate osteogenesis, both in physiological and pathological situations, as well as under the influence of external triggers (mechanical stimulation, drug administration). 相似文献