全文获取类型
收费全文 | 1861篇 |
免费 | 124篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 587篇 |
金属工艺 | 28篇 |
机械仪表 | 55篇 |
建筑科学 | 90篇 |
矿业工程 | 2篇 |
能源动力 | 88篇 |
轻工业 | 202篇 |
水利工程 | 10篇 |
石油天然气 | 13篇 |
无线电 | 129篇 |
一般工业技术 | 309篇 |
冶金工业 | 77篇 |
原子能技术 | 10篇 |
自动化技术 | 368篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 60篇 |
2021年 | 102篇 |
2020年 | 52篇 |
2019年 | 58篇 |
2018年 | 63篇 |
2017年 | 71篇 |
2016年 | 79篇 |
2015年 | 61篇 |
2014年 | 87篇 |
2013年 | 128篇 |
2012年 | 97篇 |
2011年 | 166篇 |
2010年 | 92篇 |
2009年 | 103篇 |
2008年 | 108篇 |
2007年 | 90篇 |
2006年 | 75篇 |
2005年 | 53篇 |
2004年 | 64篇 |
2003年 | 61篇 |
2002年 | 49篇 |
2001年 | 25篇 |
2000年 | 30篇 |
1999年 | 27篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 20篇 |
1995年 | 16篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1965年 | 4篇 |
排序方式: 共有1988条查询结果,搜索用时 312 毫秒
211.
Massimo Conti Paolo Crippa Simone Orcioni Marcello Pesare Claudio Turchetti Loris Vendrame Silvia Lucherini 《Analog Integrated Circuits and Signal Processing》2003,37(2):85-102
In this paper a novel CAD methodology for yield enhancement of VLSI CMOS circuits including random device variations is presented. The methodology is based on a preliminary characterization of the technological process by means of specific test chips for accurate mismatch modeling. To this purpose, a very accurate position-dependent parameter mismatch model has been formulated and extracted. Finally a CAD tool implementing this model has been developed. The tool is fully integrated in an environment of existing commercial tools and it has been experimented in the STMicroelectronics Flash Memory CAD Group.As an example of application, a bandgap reference circuit has been considered and the results obtained from simulations have been compared with experimental data. Furthermore, the methodology has been applied to the read path of a complex Flash Memory produced by STMicroelectronics, consisting of about 16,000 MOSFETs. Measurements of electrical performances have confirmed the validity of the methodology, and the accuracy of both the mismatch model and the simulation flow. 相似文献
212.
Syndiotactic propylene-ethylene copolymers have been synthesized with a single-center Cs-symmetric syndiospecific metallocene catalyst. A study of the effect of the presence of ethylene comonomeric units on the polymorphic behavior of syndiotactic polypropylene (sPP) and on the structural transitions occurring during stretching is reported. For copolymer samples with low ethylene contents, in the range 2-7 mol%, crystals of the helical form I, present in the melt-crystallized samples, transform into the trans-planar form III by stretching at high deformation. Form III transforms in part into the helical form II by releasing the tension, as it occurs for sPP. Samples with ethylene contents in the range 8-10 mol% are crystallized from the melt as a mixture of crystals of helical form I and form II. Both helical forms transform by stretching at low values of deformation (lower than 300%) into the trans-planar mesomorphic form, which transforms into the trans-planar form III by further stretching at higher deformations (higher than 500%). For these samples form III transforms back into the mesomorphic form, rather than into the helical forms, by releasing the tension. Unoriented samples of copolymers with ethylene content in the range 13-18 mol% are mainly crystallized in the helical form II, which transforms into the trans-planar mesomorphic form by stretching. Upon releasing the tension the mesomorphic form remains stable and no polymorphic transition is observed. The presence of ethylene comonomeric units stabilizes the trans-planar forms in fibers of the copolymer samples. This has been confirmed by the result that for high ethylene contents the trans-planar form III and the mesomorphic form do not transform in helical forms by annealing of fibers stretched at high deformations. 相似文献
213.
We consider the representable equational theory of binary relations, in a language expressing composition, converse, and lattice operations. By working directly with a presentation of relation expressions as graphs we are able to define a notion of reduction which is confluent and strongly normalizing and induces a notion of computable normal form for terms. This notion of reduction thus leads to a computational interpretation of the representable theory. 相似文献
214.
215.
Gustavo H. B. Donato Rodrigo Magnabosco Claudio Ruggieri 《International Journal of Fracture》1991,49(4):I-ii
Contents of volume 49 (1991) 相似文献
216.
Klein Claudio; Vogel Wolfgang; Bender Hans; Schulz Georg E. 《Protein engineering, design & selection : PEDS》1990,4(1):65-67
Based on a preliminary structural model of cyclodextrin glycosyltransferasefrom Bacillus circulans (EC 2.4.1.19
[EC]
), Ser428 and Ser475 ofthe enzyme were mutated to cysteines in order to produce suitableheavy atom derivatives. Mutant Ser475 - Cys could not be expressedas protein. Mutant Ser428 - Cys was expressed in Escherichiacoli and purified. It crystallized isomorphously and gave riseto a mercury derivative that improved the electron density map.The structural results show that the new mercury-binding siteis in a pocket at the protein surface. 相似文献
217.
The coating of soybean seeds with bacteria and micronutrients favours the vigorous growth of the plant, dispensing with the use of ammoniacal fertilizers. The optimum thickness of the coating should allow the fundamental gaseous interchanges for the germination and the ideal conditions for the activity of the bacteria. The objective of this work was to simulate dynamic mass distribution of soybean seeds covered with bacteria and macronutrients in spouted bed through a specific program developed in Maple V®. The validation of the model is done through 16 experiments carried out in a spouted bed with spray at the top. 相似文献
218.
Prototype calculations in ternary ordering systems based on the b.c.c. lattice have been carried out with the Cluster Variation Method (CVM) in the irregular tetrahedron approximation including tetrahedron interactions. The systems under investigations were characterized by strong ordering tendencies (i.e. with large, negative first neighbour interactions in all binary sub-systems) which resulted in the opening of a miscibility gap inside the B2 single-phase field. This miscibility gap is shown to be produced by frustration of the B2 cluster by a calculation using a hypothetical system with identical first neighbour interactions in the three binary sub-systems. This phase diagram presents as a key feature a central three-phase miscibility gap, which transforms into an ordinary two-phase miscibility gap involving two B2 phases after the symmetry of the interactions is broken. The results are discussed in connection with the experimental Fe–Ti–Rh phase diagram. 相似文献
219.
Giovanni Fronza Claudio Fuganti Hanns-Ludwig Schmidt Roland A. Werner 《European Food Research and Technology》2002,215(1):55-58
The biosynthesis of L-tyrosine in plants by the shikimate pathway via arogenate implies that the oxygen atom in the p-position originates from D-erythrose with a d18O \delta{}^{18}{\rm O} -value near +30 above leaf water, while its synthesis in animals by hydroxylation of external L-phenylalanine with O2 as oxygen source and a kinetic isotope effect k16/k18ɏ.018 demands a d18O \delta{}^{18}{\rm O} -value near +6. These expectations are fully confirmed by experimental data from the 18O-pattern analysis of natural aromatic compounds. The result is considered as a basis for the assignment of L-tyrosine and L-tyrosine-derived material of plant or animal origin, respectively, and for the determination of the relative amounts of plant and animal material in food and animal feed. 相似文献
220.
Combined Mutagenesis and Kinetics Characterization of the Bilin‐Binding GAF Domain of the Protein Slr1393 from the Cyanobacterium Synechocystis PCC6803
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Xiu‐Ling Xu Alexander Gutt Jonas Mechelke Dr. Sarah Raffelberg Kun Tang Dan Miao Lorena Valle Prof. Claudio D. Borsarelli Prof. Kai‐Hong Zhao Prof. Wolfgang Gärtner 《Chembiochem : a European journal of chemical biology》2014,15(8):1190-1199
The gene slr1393 from Synechocystis sp. PCC6803 encodes a protein composed of three GAF domains, a PAS domain, and a histidine kinase domain. GAF3 is the sole domain able to bind phycocyanobilin (PCB) as chromophore and to accomplish photochemistry: switching between a red‐absorbing parental and a green‐absorbing photoproduct state (λmax=649 and 536 nm, respectively). Conversions in both directions were followed by time‐resolved absorption spectroscopy with the separately expressed GAF3 domain of Slr1393. Global fit analysis of the recorded absorbance changes yielded three lifetimes (3.2 μs, 390 μs, and 1.5 ms) for the red‐to‐green conversion, and 1.2 μs, 340 μs, and 1 ms for the green‐to‐red conversion. In addition to the wild‐type (WT) protein, 24 mutated proteins were studied spectroscopically. The design of these site‐directed mutations was based on sequence alignments with related proteins and by employing the crystal structure of AnPixJg2 (PDB ID: 3W2Z), a Slr1393 orthologous from Anabaena sp. PCC7120. The structure of AnPixJg2 was also used as template for model building, thus confirming the strong structural similarity between the proteins, and for identifying amino acids to target for mutagenesis. Only amino acids in close proximity to the chromophore were exchanged, as these were considered likely to have an impact on the spectral and dynamic properties. Three groups of mutants were found: some showed absorption features similar to the WT protein, a second group showed modified absorbance properties, and the third group had lost the ability to bind the chromophore. The most unexpected result was obtained for the exchange at residue 532 (N532Y). In vivo assembly yielded a red‐absorbing, WT‐like protein. Irradiation, however, not only converted it into the green‐absorbing form, but also produced a 660 nm, further‐red‐shifted absorbance band. This photoproduct was fully reversible to the parental form upon green light irradiation. 相似文献