全文获取类型
收费全文 | 3014篇 |
免费 | 52篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 119篇 |
综合类 | 9篇 |
化学工业 | 740篇 |
金属工艺 | 140篇 |
机械仪表 | 84篇 |
建筑科学 | 45篇 |
矿业工程 | 1篇 |
能源动力 | 96篇 |
轻工业 | 169篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
无线电 | 272篇 |
一般工业技术 | 499篇 |
冶金工业 | 654篇 |
原子能技术 | 73篇 |
自动化技术 | 171篇 |
出版年
2023年 | 13篇 |
2022年 | 24篇 |
2021年 | 45篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 34篇 |
2017年 | 18篇 |
2016年 | 31篇 |
2015年 | 36篇 |
2014年 | 51篇 |
2013年 | 124篇 |
2012年 | 62篇 |
2011年 | 132篇 |
2010年 | 96篇 |
2009年 | 122篇 |
2008年 | 136篇 |
2007年 | 100篇 |
2006年 | 89篇 |
2005年 | 102篇 |
2004年 | 77篇 |
2003年 | 78篇 |
2002年 | 78篇 |
2001年 | 76篇 |
2000年 | 68篇 |
1999年 | 75篇 |
1998年 | 242篇 |
1997年 | 170篇 |
1996年 | 131篇 |
1995年 | 85篇 |
1994年 | 70篇 |
1993年 | 70篇 |
1992年 | 47篇 |
1991年 | 42篇 |
1990年 | 35篇 |
1989年 | 38篇 |
1988年 | 32篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1984年 | 30篇 |
1983年 | 34篇 |
1982年 | 35篇 |
1981年 | 29篇 |
1980年 | 33篇 |
1979年 | 39篇 |
1978年 | 20篇 |
1977年 | 24篇 |
1976年 | 38篇 |
1975年 | 11篇 |
1974年 | 7篇 |
排序方式: 共有3082条查询结果,搜索用时 8 毫秒
21.
H Miyachi Y Koiso R Shirai S Niwayama JO Liu Y Hashimoto 《Canadian Metallurgical Quarterly》1998,46(7):1165-1168
The synthesis and tumor necrosis factor (TNF)-alpha production enhancing activity of substituted 3'-methylthalidomides on human leukemia cell line HL-60 stimulated with 12-O-tetradecanoyl-phorbol 13-acetate (TPA) are described. Though the introduction of an electron-donating amino group at the phthaloyl moiety of alpha-methylthalidomides enhanced the activity, substituted alpha-methylthalidomides showed decreased stereoselectivity as compared to that of non-substituted alpha-methylthalidomide. The data indicates that the TNF-alpha production enhancing activity of thalidomide derivatives depends on both the electronic-state of substituents at the fused benzene ring and the stereochemistry of the glutarimide moiety. 相似文献
22.
23.
24.
Importance of initial surface film in the degradation of stainless steels by atmospheric exposure 总被引:1,自引:0,他引:1
The surface compositions of stainless steels types 304, 316, 430, and 444 combined with four types of surface finishes, 2B finish, hairline polishing, mirror polishing, and bright annealing, were measured by ICP-AES, EPMA, and XPS before exposure. The surface finish that most enriched the chromic species in the surface film was mirror polishing, followed by bright annealing, 2B finish, and hairline polishing. The order of corrosion-resistance was type 444, type 316, type 304, and type 430. The surface compositions were correlated with the rating number and pitting depth after exposure to atmospheric environments. The rating number had a high positive correlation with the concentration of Cr in the surface film, and had a slight correlation with the near-surface composition measured by EPMA at 12 kV, but did not show any correlation with bulk composition within the composition range covered in the present work. This same trend was observed for pitting depth. It was concluded that the cationic concentration of Cr in the surface film before atmospheric exposure is the prime factor in controlling the resistance of stainless steels to atmospheric corrosion. 相似文献
25.
Minoru Ueno Satoshi Yamamoto Kenjiro Meguro 《Journal of the American Oil Chemists' Society》1974,51(8):373-376
Several salts of α,ω-sulfates, MO3SO(CH2)n OSO3M(n=12, 14, 16, 18, and M=Li, Na, and K) were prepared from the corresponding α,ω-alkane diols. The Krafft points of these
α,ω-sulfates with common counterion as estimated by electroconductivity measurements increased with the increase of the hydrocarbon
chain length, and the effect of the counterions on the Krafft points of the α,ω-sulfates with the same hydrocarbon chain length
was in the order : Li<Na<K. Solutions of the α,ω-sulfates, except disodium dodecanediol disulfate, showed two break points
corresponding to the first and second critical micelle concentration in each plot of the electroconductivity as a function
of the concentration. The existence of the second break point suggested that another aggregation of rearrangement of the existing
aggregates occurs in α,ω-sulfate solutions in addition to the usual micelle formation. The first and second break points of
α,ω-sulfates with sodium counterion decreased logarithmically with increasing total number of methylene groups. The relationships
were given as follows: log(first break point)=−0.138Nc−0.095; log(second break point)=−0.104Nc−0.251. The effect of the counterions
upon the break points of α,ω-sulfates with the same hydrocarbon chain length was in accordance with their positions in the
lyotropic series. 相似文献
26.
Koki Murano Tomoyoshi Shimobaba Atsushi Sugiyama Naoki Takada Takashi Kakue Minoru Oikawa Tomoyoshi Ito 《Computer Physics Communications》2014
We report fast computation of computer-generated holograms (CGHs) using Xeon Phi coprocessors, which have massively x86-based processors on one chip, recently released by Intel. CGHs can generate arbitrary light wavefronts, and therefore, are promising technology for many applications: for example, three-dimensional displays, diffractive optical elements, and the generation of arbitrary beams. CGHs incur enormous computational cost. In this paper, we describe the implementations of several CGH generating algorithms on the Xeon Phi, and the comparisons in terms of the performance and the ease of programming between the Xeon Phi, a CPU and graphics processing unit (GPU). 相似文献
27.
Shin'ichiro Asai Ueki Saruta Masayuki Tobita Minoru Takano Yasuo Miyashita 《应用聚合物科学杂志》1995,56(7):769-777
A thermoset type anisotropic conductive adhesive film (ACAF), which electrically connects an ITO glass and a flex circuit both having conducting pattersn of less than 100 μm in pitch, has been developed. In this development, bisphenol A and bisphenol F epoxy resins were tested to formulate an ACAF with easy-to-handle tackiness, flexibility, and strenght. A curing agent that gives fast cure and long shelf-life properties to the epoxy resin was also selected. The tensile stress–strain responses of obtained adhesive films were successfully used for determining the formulation. Good aftercure physical properties (electrical and mechanical) were obtained. Durability against high temperature and high humidity were also tested to confirm long-term stability of the conduction of this ACAF. © 1995 John Wiley & Sons, Inc. 相似文献
28.
To model the molten globule structure of -lactalbumin, moleculardynamics (MD) simulations were carried out for the protein inexplicit water at high temperature. In these simulations, long-rangeCoulomb interactions were evaluated explicitly with an originalmethod (particleparticle and particlecell: PPPC)to avoid artifacts caused by the cut-off. The MD simulationswere started from two initial conditions to verify that similarresults would be obtained. From the last 150 ps trajectoriesof the two MD simulations, two partially unfolded average structureswere obtained. These structures had the following common structuralfeatures which are characteristic of the molten globule state.The radii of gyration for these conformations were 7.4 and 9.6%larger than that of the native state. These values were almostthe same as the experimental value (9.6%) observed recentlyby small-angle X-ray scattering (Kataoka,M., Kuwajima,K., Tokunaga,F.and Goto,Y., 1997, Protein Sci., 6, 422430). Furthermore,aromatic residues of clusters I and II in these structures werefar apart from each other except for Try103Trp104. Thisresult is in good agreement with NMR experimental results forthe acid-denatured molten globule state (Alexandrescu et al.,1992, 1993); that is, NOE signals between the aromatic residueswere not observed, except for that of Try103Trp104 inthe molten globule state. Other structural features of thesemodels for the molten globule state are discussed with referenceto native state structures. 相似文献
29.
The NMR spectra of olefinic protons in the four representative conjugated fatty acid methyl esters, methylcis-9,trans-11-octadecadienoate, methyltrans-9,trans-11-octadecadienoate, methyl α eleostearate, and methyl β eleostearate, were studied. The chemical shift of each olefinic
proton in these compounds was determined by considering their intramolecular environment. Coupling constants were also obtained
as the results of spectral analysis. 相似文献
30.
In order to improve the fracture properties of p, p′-diaminodiphenylmethane-cured epoxy resin, various kinds of aromatic and aliphatic glycidyl compounds were investigated as a modifier at an amount of 30 wt %. Several compounds promoted the fracture toughness. In any glycidyl compounds, however, heat resistance was decreased by the modification. The dynamic mechanical properties of the modified epoxy resins were measured. The crosslinking density ρ was calculated from the theory of rubber elasticity, and the mechanical properties of the resins were discussed in regard to the crosslinking density. Tensile strength was scarcely affected by the crosslinking density. Elongation at break and Izod impact strength increased remarkably with decrease in crosslinking density. The fracture toughness KIc- increased with decrease in crosslinking density except at small ρ. 相似文献