全文获取类型
收费全文 | 1518篇 |
免费 | 98篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 19篇 |
综合类 | 12篇 |
化学工业 | 518篇 |
金属工艺 | 35篇 |
机械仪表 | 34篇 |
建筑科学 | 119篇 |
矿业工程 | 2篇 |
能源动力 | 47篇 |
轻工业 | 121篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 104篇 |
一般工业技术 | 299篇 |
冶金工业 | 63篇 |
原子能技术 | 14篇 |
自动化技术 | 229篇 |
出版年
2023年 | 18篇 |
2022年 | 33篇 |
2021年 | 40篇 |
2020年 | 26篇 |
2019年 | 39篇 |
2018年 | 37篇 |
2017年 | 30篇 |
2016年 | 55篇 |
2015年 | 63篇 |
2014年 | 61篇 |
2013年 | 72篇 |
2012年 | 76篇 |
2011年 | 123篇 |
2010年 | 84篇 |
2009年 | 90篇 |
2008年 | 67篇 |
2007年 | 81篇 |
2006年 | 53篇 |
2005年 | 60篇 |
2004年 | 51篇 |
2003年 | 41篇 |
2002年 | 39篇 |
2001年 | 19篇 |
2000年 | 24篇 |
1999年 | 31篇 |
1998年 | 26篇 |
1997年 | 17篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1972年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1622条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
Daniel Stubba Dr. Dennis Bensinger Janika Steinbacher Lilia Proskurjakov Álvaro Salcedo Gómez Dr. Uwe Schmidt Prof. Dr. Stefan Roth Prof. Dr. Katja Schmitz Prof. Dr. Boris Schmidt 《ChemMedChem》2019,14(23):2005-2022
The ubiquitin-proteasome system (UPS) is an established therapeutic target for approved drugs to treat selected hematologic malignancies. While drug discovery targeting the UPS focuses on irreversibly binding epoxyketones and slowly-reversibly binding boronates, optimization of novel covalent-reversibly binding warheads remains largely unattended. We previously reported α-ketoamides to be a promising reversible lead motif, yet the cytotoxic activity required further optimization. This work focuses on the lead optimization of phenoxy-substituted α-ketoamides combining the structure-activity relationships from the primed and the non-primed site of the proteasome β5 subunit. Our optimization strategy is accompanied by molecular modeling, suggesting occupation of P1′ by a 3-phenoxy group to increase β5 inhibition and cytotoxic activity in leukemia cell lines. Key compounds were further profiled for time-dependent inhibition of cellular substrate conversion. Furthermore, the α-ketoamide lead structure 27 does not affect escape response behavior in Danio rerio embryos, in contrast to bortezomib, which suggests increased target specificity. 相似文献
46.
Daniel Ortiz Morales Simon Westerberg Pedro X. La Hera Uwe Mettin Leonid Freidovich Anton S. Shiriaev 《野外机器人技术杂志》2014,31(3):343-363
Working with forestry machines requires a great deal of training to be sufficiently skilled to operate forestry cranes. In view of this, it would be desirable within the forestry industry to introduce automated motions, such as those seen in robotic arms, to shorten the training time and make the work of the operator easier. Motivated by this fact, we have developed two experimental platforms for testing control systems and motion‐planning algorithms in real time. They correspond to a laboratory setup and a commercial version of a hydraulic manipulator used in forwarder machines. The aim of this article is to present the results of this development by providing an overview of our trajectory‐planning algorithm and motion‐control method, with a subsequent view of the experimental results. For motion control, we design feedback controllers that are able to track reference trajectories based on sensor measurements. Likewise, we provide arguments to design controllers in an open‐loop for machines that lack sensing devices. Relying on the tracking efficiency of these controllers, we design time‐efficient reference trajectories of motions that correspond to logging tasks. To demonstrate performance, we provide an overview of extensive testing done on these machines. 相似文献
47.
48.
I. Raffeis U. Vroomen F. Adjei-Kyeremeh D. Großmann H. Hammelrath E. Westhoff S. Bremen D. Boscolo Bozza A. Bührig-Polaczek 《Materialwissenschaft und Werkstofftechnik》2020,51(4):432-444
A methodology is presented that compares the microstructural and mechanical properties of as-cast and additive-made ferritic-austenitic duplex steel 1.4517. Microstructure of approximately equal amounts of ferrite and austenite measured in as-cast material could not be replicated in post heat-treated laser powder bed fusion samples after 30 min and 60 min of post heat treatment. This is attributed to nitrogen loss during powder atomization which left fewer austenite formers. Post-heat treated laser powder bed fusion samples of duplex structure had its austenite content repeatedly adjusted between 38 % and 40 %. As-built laser powder bed fusion tensile specimens which had a ferritic microstructure recorded high tensile and yield strength but had very poor elongation. Post heat-treated duplex laser powder bed fusion tensile specimen built in both horizontal and vertical orientations had good tensile and yield strength comparable to conventional casting processes; Tensile strength – 739 MPa (horizontal), 759 MPa (vertical); Yield strength (Rp0.2) – 489 MPa (horizontal), 525 MPa (vertical). The horizontally built duplex specimen had a very high elongation of 32 % than the vertical (11 %) or conventionally reported (22 %). This work establishes the 1.4517 duplex steel as a good candidate with good mechanical properties when processed by additive manufacturing. 相似文献
49.
50.
The development of innovative metal catalysis for selective bond formation is an important task in organic chemistry. The group 13 metal indium is appealing for catalysis because indium-based reagents are minimally toxic, selective, and tolerant toward various functional groups. Among elements in this group, the most stable oxidation state is typically +3, but in molecules with larger group 13 atoms, the chemistry of the +1 oxidation state is also important. The use of indium(III) compounds in organic synthesis has been well-established as Lewis acid catalysts including asymmetric versions thereof. In contrast, only sporadic examples of the use of indium(I) as a stoichiometric reagent have been reported: to the best of our knowledge, our investigations represent the first synthetic method that uses a catalytic amount of indium(I). Depending on the nature of the ligand or the counteranion to which it is coordinated, indium(I) can act as both a Lewis acid and a Lewis base because it has both vacant p orbitals and a lone pair of electrons. This potential ambiphilicity may offer unique reactivity and unusual selectivity in synthesis and may have significant implications for catalysis, particularly for dual catalytic processes. We envisioned that indium(I) could be employed as a metallic Lewis base catalyst to activate Lewis acidic boron-based pronucleophiles for selective bond formation with suitable electrophiles. Alternatively, indium(I) could serve as an ambiphilic catalyst that activates both reagents at a single center. In this Account, we describe the development of low-oxidation state indium catalysts for carbon-carbon bond formation between boron-based pronucleophiles and various electrophiles. We discovered that indium(I) iodide was an excellent catalyst for α-selective allylations of C(sp(2)) electrophiles such as ketones and hydrazones. Using a combination of this low-oxidation state indium compound and a chiral semicorrin ligand, we developed catalytic highly enantioselective allylation, crotylation, and α-chloroallylation reactions of hydrazones. These transformations proceeded with rare constitutional selectivities and remarkable diastereoselectivities. Furthermore, indium(I) triflate served as the most effective catalyst for allylations and propargylations of C(sp(3)) electrophiles such as O,O-acetals, N,O-aminals, and ethers, and we applied this methodology to carbohydrate chemistry. In addition, a catalyst system composed of indium(I) chloride and a chiral silver BINOL-phosphate facilitated the highly enantioselective allylation and allenylation of N,O-aminals. Overall, these discoveries demonstrate the versatility, efficiency, and sensitivity of low-oxidation state indium catalysts in organic synthesis. 相似文献