全文获取类型
收费全文 | 7060篇 |
免费 | 415篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 100篇 |
综合类 | 28篇 |
化学工业 | 1955篇 |
金属工艺 | 184篇 |
机械仪表 | 152篇 |
建筑科学 | 418篇 |
矿业工程 | 39篇 |
能源动力 | 247篇 |
轻工业 | 478篇 |
水利工程 | 43篇 |
石油天然气 | 5篇 |
无线电 | 678篇 |
一般工业技术 | 1487篇 |
冶金工业 | 328篇 |
原子能技术 | 39篇 |
自动化技术 | 1302篇 |
出版年
2024年 | 14篇 |
2023年 | 101篇 |
2022年 | 154篇 |
2021年 | 268篇 |
2020年 | 187篇 |
2019年 | 191篇 |
2018年 | 190篇 |
2017年 | 187篇 |
2016年 | 283篇 |
2015年 | 299篇 |
2014年 | 350篇 |
2013年 | 508篇 |
2012年 | 474篇 |
2011年 | 626篇 |
2010年 | 413篇 |
2009年 | 421篇 |
2008年 | 413篇 |
2007年 | 359篇 |
2006年 | 286篇 |
2005年 | 255篇 |
2004年 | 201篇 |
2003年 | 151篇 |
2002年 | 152篇 |
2001年 | 77篇 |
2000年 | 109篇 |
1999年 | 94篇 |
1998年 | 104篇 |
1997年 | 87篇 |
1996年 | 91篇 |
1995年 | 58篇 |
1994年 | 52篇 |
1993年 | 54篇 |
1992年 | 48篇 |
1991年 | 34篇 |
1990年 | 24篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有7483条查询结果,搜索用时 15 毫秒
61.
62.
Seung Bum Kil Yannick Augros Yves Leterrier Jan‐Anders E. Mnson Andreas Christel Camille Borer 《Polymer Engineering and Science》2003,43(2):329-343
The rheological properties in solution, in shear and in uniaxial elongation of poly(ethylene terephthalate) (PET) reacted together with hyperbranched polymers (HBPs) were investigated. Two different PET grades, of low and high molecular weights, were compounded with sub‐ to over‐stoichiometric concentrations of HBPs of second and fourth pseudo‐generation, and subsequently subjected to a solid‐state polycondensation (SSP). The formation of microgels, which occurs at high HBP concentration, gave rise to a large increase in melt elasticity and a related decrease in melt strength. At low HBP concentrations, the complex viscosity of the unreacted HBP/PET was considerably reduced, thus demonstrating a lubrication effect of the HBP molecules. During SSP, the intrinsic and shear viscosities exhibited a gradual increase, which was similar for both PET and HBP/PET blends, and was correlated to an increase in molecular weight, through linear‐chain extension and branching reactions. The elongational viscosity of the reactive blends was also increased as a function of reaction time, and this increase was much larger in the case of the HBP/PET blends. A 400% increase in melt strength of the PET was obtained by combining SSP and trace amounts of an HBP of second generation, without any decrease in drawability. 相似文献
63.
Jens Cornelis Markus Ihmsen Andreas Peer Matthias Teschner 《Computer Graphics Forum》2014,33(2):255-262
We propose to use Implicit Incompressible Smoothed Particle Hydrodynamics (IISPH) for pressure projection and boundary handling in Fluid‐Implicit‐Particle (FLIP) solvers for the simulation of incompressible fluids. This novel combination addresses two issues of existing SPH and FLIP solvers, namely mass preservation in FLIP and efficiency and memory consumption in SPH. First, the SPH component enables the simulation of incompressible fluids with perfect mass preservation. Second, the FLIP component efficiently enriches the SPH component with detail that is comparable to a standard SPH simulation with the same number of particles, while improving the performance by a factor of 7 and significantly reducing the memory consumption. We demonstrate that the proposed IISPH‐FLIP solver can simulate incompressible fluids with a quantifiable, imperceptible density deviation below 0.1%. We show large‐scale scenarios with up to 160 million particles that have been processed on a single desktop PC using only 15GB of memory. One‐ and two‐way coupled solids are illustrated. 相似文献
64.
Wolfgang Knoll Mieko Matsuzawa Andreas Offenhäusser Jürgen Rühe 《Israel journal of chemistry》1996,36(4):357-369
Various strategies are described for the bio-functionalization of solid substrates by design of interfacial architectures. The first approach is based on the self-assembly process of long-chain thiol molecules from solution to a (noble) metal surface. If some of these building blocks carry a binding site (ligand) for proteins (receptors, antibodies, etc.) the metal surface can be tailored for maximum specific binding while simultaneously minimizing nonspecific adsorption. The second concept is based on polymers that are covalently attached to (oxide) surfaces. The preparation of these (end-) grafted functional polymers involves either the binding of preformed macromolecules to corresponding sites at the surface of the support or the recently introduced “grafting-from” method, by which an initiator molecule is first covalently bound to the surface and then activated — either by heat or light — in the presence of suitable monomer units such that a polymer chain grows from the solid/solution interface. Finally, the functionalization of patterned surfaces by peptide chains that mimic the binding domains of cell adhesion proteins is summarized. It is demonstrated that not only the selective adhesion of neuronal cells can then be controlled, but also their development with the outgrowth of dendrites and axons. 相似文献
65.
Nikos Mavrogiannopoulos Andreas Pashalidis Bart Preneel 《International Journal of Information Security》2014,13(3):217-228
Public key Kerberos (PKINIT) is a standard authentication and key establishment protocol. Unfortunately, it suffers from a security flaw when combined with smart cards. In particular, temporary access to a user’s card enables an adversary to impersonate that user for an indefinite period of time, even after the adversary’s access to the card is revoked. In this paper, we extend Shoup’s key exchange security model to the smart card setting and examine PKINIT in this model. Using this formalization, we show that PKINIT is indeed flawed, propose a fix, and provide a proof that this fix leads to a secure protocol. 相似文献
66.
Mingjun Yuan Andreas Winardi Shaoqin Gong Lih‐Sheng Turng 《Polymer Engineering and Science》2005,45(6):773-788
The effects of submicron core‐shell rubber (CSR) particles, nanoclay fillers, and molding parameters on the mechanical properties and cell structure of injection‐molded microcellular polyamide‐6 (PA6) composites were studied. The experimental results of PA6 nanocomposites with 5.0 and 7.5 wt% nanoclay loadings and of CSR‐modified PA6 composites with 0.5 and 3.1 wt% CSR loadings were compared to their neat resin counterparts. This study found that nanoclay was more efficient in promoting a smaller cell size, larger cell density, and higher tensile strength for microcellular injection molding parts. A higher nanoclay loading led to more brittle behavior for microcellular parts. It was found that a proper amount of CSR particles could be added to the microcellular injection‐molded PA6 to reduce the cell size, increase the cell density, and enhance the toughness of the molded part. However, CSR particles were less effective cell nucleation agents as compared to nanoclay for producing desirable cell structures, and a higher CSR loading was found to have diminishing effects on the process and on the properties of the parts. POLYM. ENG. SCI., 45:773–788, 2005. © 2005 Society of Plastics Engineers 相似文献
67.
68.
Philipp Hauck Andreas Jentys Johannes A. Lercher 《Applied catalysis. B, Environmental》2007,70(1-4):91-99
In order to meet the stricter NOx and particulate emission limits for commercial vehicles, the selective catalytic reduction (SCR) with urea is currently seen having the highest potential. The conversion of urea into ammonia and carbon dioxide consists of two consecutive reactions, in which isocyanic acid is an intermediate that is hydrolyzed over TiO2. The intrinsic kinetics and the surface chemistry for this reaction are explored. Up to a temperature of 132 °C the reaction was in the intrinsic kinetic regime (EA = 73 kJ/mol), while at higher temperatures the reaction was limited by pore and external diffusion constraints, respectively. In the presence of NO, NH3 and NO2, the catalytic activity was negatively influenced, increasing in severity in the sequence mentioned indicating that nitrates formed from NO2 were most effective in blocking cations and anions of TiO2. IR spectroscopy indicates that dissociative adsorption of HNCO on TiO2 forms Ti–NCO and hydrogen bonded OH species. In the presence of water, isocyanic acid was so rapidly hydrolyzed that only adsorbed ammonia was observed on the catalyst surface. The presence of NO, NH3 and NO2 retards hydrolysis leading to the appearance of isocyanate species on the surface. 相似文献
69.
Ribosome display of mammalian receptor domains 总被引:2,自引:0,他引:2
Many mammalian receptor domains, among them a large number of potential therapeutic target proteins, are highly aggregation-prone upon heterologous expression in bacteria. This severely limits functional studies of such receptor domains and also their engineering towards improved properties. One of these proteins is the Nogoreceptor, which plays a central role in mediating the inhibition of axon growth and functional recovery after injury of the adult mammalian central nervous system. We show here that the ligand binding domain of the Nogoreceptor folds to an active conformation in ternary ribosomal complexes, as formed in ribosome display. In these complexes the receptor is still connected, via a C-terminal tether, to the peptidyl tRNA in the ribosome and the mRNA also stays connected. The ribosome prevents aggregation of the protein, which aggregates as soon as the release from the ribosome is triggered. In contrast, no active receptor was observed in phage display, where aggregation appears to prevent incorporation of the protein into the phage coat. This strategy sets the stage for rapidly studying defined mutations of such aggregation-prone receptors in vitro and to improve their properties by in vitro evolution using the ribosome display technology. 相似文献
70.
Johannes Konnerth Andreas Jger Josef Eberhardsteiner Ulrich Müller Wolfgang Gindl 《应用聚合物科学杂志》2006,102(2):1234-1239
Seven different polymers used frequently as adhesives and/or matrix polymers in wood, wood composites, and natural fiber‐reinforced composites were studied by uniaxial tensile tests and nanoindentation. It was shown that the elastic modulus, the hardness, the creep factor, and the elastic‐, plastic‐, and viscoelastic work of indentation of the seven different polymers is essentially the same regardless whether the polymers were tested in the form of pure films or in situ, i.e., in an adhesive bond line with spruce wood. An excellent correlation was found between the elastic modulus measured by tensile tests and the elastic modulus measured by nanoindentation. In spite of the good correlation, the elastic modulus measured by nanoindentation is significantly higher than the elastic modulus measured by tensile tests. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1234–1239, 2006 相似文献