全文获取类型
收费全文 | 85665篇 |
免费 | 1081篇 |
国内免费 | 408篇 |
专业分类
电工技术 | 789篇 |
综合类 | 2320篇 |
化学工业 | 11739篇 |
金属工艺 | 4816篇 |
机械仪表 | 3053篇 |
建筑科学 | 2297篇 |
矿业工程 | 569篇 |
能源动力 | 1147篇 |
轻工业 | 3789篇 |
水利工程 | 1279篇 |
石油天然气 | 342篇 |
武器工业 | 1篇 |
无线电 | 9447篇 |
一般工业技术 | 16636篇 |
冶金工业 | 3040篇 |
原子能技术 | 284篇 |
自动化技术 | 25606篇 |
出版年
2023年 | 28篇 |
2022年 | 31篇 |
2021年 | 76篇 |
2020年 | 37篇 |
2019年 | 45篇 |
2018年 | 14491篇 |
2017年 | 13403篇 |
2016年 | 10000篇 |
2015年 | 650篇 |
2014年 | 305篇 |
2013年 | 293篇 |
2012年 | 3237篇 |
2011年 | 9495篇 |
2010年 | 8356篇 |
2009年 | 5627篇 |
2008年 | 6843篇 |
2007年 | 7834篇 |
2006年 | 173篇 |
2005年 | 1285篇 |
2004年 | 1183篇 |
2003年 | 1199篇 |
2002年 | 577篇 |
2001年 | 147篇 |
2000年 | 198篇 |
1999年 | 106篇 |
1998年 | 177篇 |
1997年 | 113篇 |
1996年 | 117篇 |
1995年 | 44篇 |
1994年 | 52篇 |
1993年 | 42篇 |
1992年 | 33篇 |
1991年 | 34篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 25篇 |
1969年 | 35篇 |
1968年 | 50篇 |
1967年 | 35篇 |
1966年 | 45篇 |
1965年 | 48篇 |
1963年 | 31篇 |
1962年 | 24篇 |
1960年 | 31篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 38篇 |
1956年 | 35篇 |
1955年 | 64篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Dr. Adarshi P. Welegedara Dr. Ansis Maleckis Ruchira Bandara Dr. Mithun C. Mahawaththa Iresha Dilhani Herath Yi Jiun Tan Dr. Angeliki Giannoulis Prof. Daniella Goldfarb Prof. Gottfried Otting Prof. Thomas Huber 《Chembiochem : a European journal of chemical biology》2021,22(8):1480-1486
The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. GdIII−GdIII distances measured by double electron–electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-GdIII were indistinguishable from GdIII−GdIII distances measured of MBP containing cysteine reacted with 4Br-MDPA tags. 相似文献
2.
Dr. Raysa Khan Tareque Dr. Storm Hassell-Hart Dr. Tobias Krojer Dr. Anthony Bradley Dr. Srikannathasan Velupillai Dr. Romain Talon Dr. Michael Fairhead Dr. Iain J. Day Kamlesh Bala Dr. Robert Felix Dr. Paul D. Kemmitt Prof. Paul Brennan Prof. Frank von Delft Dr. Laura Díaz Sáez Prof. Kilian Huber Prof. John Spencer 《ChemMedChem》2020,15(24):2513-2520
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified. 相似文献
3.
Landsiedel Justus Root Waleri Schramm Christian Menzel Alexander Witzleben Steffen Bechtold Thomas Pham Tung 《Nano Research》2020,13(10):2658-2664
Nano Research - Development of colored surfaces by formation of nano-structured aggregates is a widely used strategy in nature to color lightweight structures (e.g. butterflies) without the use of... 相似文献
4.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
5.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献
6.
Annika Jahn Anton Hoffmann Luisa Blaesing Fabian Kunde Martin Bertau Martina Bremer Steffen Fischer 《化学,工程师,技术》2020,92(11):1733-1740
The enzymatic conversion of lignins, possibly in combination with electrochemical oxidation, makes aromatics such as syringol, guaiacol, vanillin and catechol available in the qualities required by the fragrance industry. The lignins were obtained by soda digestion from wheat straw and Miscanthus, characterized and then converted with laccases. The overall yield amounted up to 9 wt % with a product spectrum confined to four substances. Catechol was the major product, with a fraction of ≈75 %. It can easily be isolated by extraction with acetone. 相似文献
7.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards. 相似文献
8.
9.
10.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献