全文获取类型
收费全文 | 629篇 |
免费 | 21篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 105篇 |
金属工艺 | 34篇 |
机械仪表 | 27篇 |
建筑科学 | 8篇 |
能源动力 | 11篇 |
轻工业 | 42篇 |
水利工程 | 1篇 |
石油天然气 | 6篇 |
无线电 | 127篇 |
一般工业技术 | 112篇 |
冶金工业 | 68篇 |
原子能技术 | 6篇 |
自动化技术 | 92篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 17篇 |
2014年 | 13篇 |
2013年 | 38篇 |
2012年 | 27篇 |
2011年 | 34篇 |
2010年 | 31篇 |
2009年 | 43篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 16篇 |
2003年 | 28篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 19篇 |
1998年 | 27篇 |
1997年 | 29篇 |
1996年 | 10篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有657条查询结果,搜索用时 15 毫秒
31.
Hong Tsao Olga Rechkoblit Shantu Amin Nicholas E. Geacintov 《Polycyclic Aromatic Compounds》2013,33(1-4):1-10
Adducts derived from the binding of the (+)-7R,8S,9S,10R and (?)-7S,8R,9R,10S enantiomers of r7,t8-dihydrodiol-t9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) to 2′-deoxyguanosine residues in DNA are known to induce mutations due to error-prone DNA replication. Because the conformational properties of these lesions may be important in these phenomena, we have examined the effects of the stereoisomeric (+)- and (?)-trans-anti-[BP]-N 2-dG lesions positioned site-specifically at or near primer/template oligonucleotide junctions on DNA bending using high resolution gel electrophoresis. Remarkable differences in electrophoretic mobilities μ are observed in the two adducts derived from the tumorigenic (+)-anti-BPDE, and the non-tumorigenic (?)-anti-BPDE enantiomer. With the (+)-trans lesion positioned on the template strand adjacent to the 3′-end of the primer strand, a remarkable decrease in μ is observed. This suggests the existence of a bend at the single strand-double strand junction. Only modest decreases in μ are observed in the case of the (?)-trans lesion, or when the 3′-end is opposite to, or more distant from the lesion site. These observations are discussed in terms of the known NMR solution structures of these lesions in the same sequence context, and the properties of primer/template DNA in polymerases. 相似文献
32.
We employ self-consistent mean-field (SCMF) theory in studying the body-centered cubic (bcc) spheres of block copolymers in the presence of a neutral solvent. First we examine the accuracy of the dilution approximation then analyze the dependence of the bcc structural sizes with copolymer volume fraction ?, the interaction parameter χAB, and degree of copolymerization N. Our results reveal that both distribution of each component and the micro-structural length scales are greatly influenced by each parameter ?, χAB, and N. As expected, with decreasing ?, more solvent distributes non-uniformally in the segregated domains, therefore deviation from the dilution approximation increases. This also suggests that when the effective segregation parameter ?χABN is fixed, a larger deviation is expected as χABN increases (i.e. ? decreases). Although when both χABN and ? are fixed, decreasing N (i.e. increasing χAB) enlarges the deviation from the dilution approximation. Furthermore, this solvent non-uniformity behavior is so significant that it even affects the dependence of the domain spacing L* and the matrix length Λ* with respect to (χAB)effN=?χABN near the ODT. When the systems are in molten state and/or in the concentrated regime, both L* and Λ* exhibit a sharp increase behavior as ODT is approached, due to many of the minority blocks being pulled from the spherical domains and swelling the matrix. With increasing solvent amount and/or χABN, we observe that the increase of the degree for the minority blocks pulled from the spheres into the matrix near the ODT is not as significant as that in the melt. As such, the sharp increase behavior in L* as well as Λ* near the ODT smoothens and even disappears. 相似文献
33.
34.
Hsing-I Hsiang Li-Then Mei Shi-Wen Yang Wen-Chang Liao Fu-Su Yen 《Ceramics International》2011,37(7):2453-2458
The alumina addition effects on the crystallization, sintering behaviors and dielectric properties of BaO–ZnO–SrO–CaO–Nd2O3–TiO2–B2O3–SiO2 (Ba–Zn–Sr–Ca–Nd–Ti–B–Si) glass powder were investigated using the differential thermal analyzer (DTA), thermo-mechanical analyzer (TMA), X-ray diffractometer (XRD). The results showed that the addition of alumina powder into Ba–Zn–Sr–Ca–Nd–Ti–B–Si glass changed the crystallization sequence from Nd2Ti4O11–Nd0.66TiO3 to Nd2Ti3O8.7–Nd2Ti2O7–Nd2Ti4O11and increased the densification activation energy due to the dissolution of Al3+ ions into the glass structure. Fully densified 30 vol.% alumina-added Ba–Zn–Sr–Ca–Nd–Ti–B–Si glass can be obtained via glass viscous flow before the second and third crystalline phases, Nd2Ti2O7 and Nd2Ti4O11crystallization. The 30 vol.% alumina-added Ba–Zn–Sr–Ca–Nd–Ti–B–Si glass–ceramics sintered at 900 °C exhibited a high dielectric constant of 17 and a quality factor of about 820, which provided a promising candidate for LTCC applications. 相似文献
35.
J.D. Rasmussen T.-C. Tsao R.D. Hanson S.G. Kapoor 《International Journal of Machine Tools and Manufacture》1994,34(3)
This paper describes the design of a piezoelectric actuated cutting tool and implementation of digital servo controls for machining surfaces with dynamically varying depth of cut. Through a flexure hinge, the tool holder could generate 50 μm travel at the tip of the cutting insert. Tool motion errors of less than 0.5 μm were achieved in tracking cyclic waveforms by employing a digital repetitive servo control. When applied to turning aluminum and steel workpieces with variable depth of cut using carbide tools, less than 5 μm machined surface errors were measured. 相似文献
36.
Wen-Ya Lee Kai-Fang Cheng Cheng-Liang Liu Sung-Tso Lin Chu-Chen Chueh Feng-Yu Tsai Wen-Chang Chen 《Journal of Polymer Research》2009,16(3):239-244
Surface morphologies and thin film transistor characteristics of three thiophene (TH)-thieno[3,4-b]pyrazine (TP) donor–acceptor
conjugated copolymers (PTHTP-C7, PTHTP-C12, and PBTHTP-C7) are reported. The long alkyl side chain probably promoted PTHTP-C12
to become a fibrillar-like structure on the hexamethyldisilazane (HMDS)-modified surface and resulted in better charge transport
properties than the other two copolymers. However, a nodule-like morphology on the octyltrichlorosilane (OTS)-modified surface
was observed due to the strong interaction between the non-polar alkyl chains of PTHTP-C12 and highly hydrophobic surface.
By further annealing at a higher temperature, a densely packed grain morphology on octyltrichlorosilane (OTS) modified SiO2 surface was shown and led to the field effect mobility of 1.1 × 10−2 cm2 V−1 s−1 with the on/off ratio of 227. The present study suggests that thiophene based donor–acceptor conjugated polymers could have
a high FET mobility through the manipulation of polymer morphology. 相似文献
37.
Tzi-Yi Wu Ming-Hsiu Tsao Fu-Lin Chen Shyh-Gang Su Cheng-Wen Chang Hong-Paul Wang Yuan-Chung Lin Wen-Chung Ou-Yang I-Wen Sun 《International journal of molecular sciences》2010,11(1):329-353
New organic dyes comprising carbazole, iminodibenzyl, or phenothiazine moieties, respectively, as the electron donors, and cyanoacetic acid or acrylic acid moieties as the electron acceptors/anchoring groups were synthesized and characterized. The influence of heteroatoms on carbazole, iminodibenzyl and phenothiazine donors, and cyano-substitution on the acid acceptor is evidenced by spectral, electrochemical, photovoltaic experiments, and density functional theory calculations. The phenothiazine dyes show solar-energy-to-electricity conversion efficiency (η) of 3.46–5.53%, whereas carbazole and iminodibenzyl dyes show η of 2.43% and 3.49%, respectively. 相似文献
38.
This paper examines the optimization of the process parameters of GZO films deposited on polyethylene terephthalate substrates by R.F. magnetron sputtering using the Taguchi method, aiming to obtain highly transparent and conductive films. The influences of the various sputtering factors (R.F. power, sputtering pressure, deposition time, substrate temperature and post-annealing temperature) on electrical resistivity and structural, morphological and optical transmittance of GZO films are analyzed. The electrical resistivity and the optical transmittance of GZO films were improved by post-annealing the substrate during the deposition process. Experimental results indicate the optimal process parameters in GZO films deposited on polyethylene terephthalate substrates can be determined effectively. The electrical resistivity of GZO films is decreased from 1.194 × 10−3 Ω cm to 8.627 × 10−4 Ω cm and the optical transmittance is increased from 86.148% to 90%, leading to multiple performance characteristics in deposition qualities through the Grey–Taguchi method. 相似文献
39.
Drilling is an indispensible machining process for building a load-carrying structure of composite materials. Delamination defect is often produced at the exit of drilling, which threatens the service safety of the structure. There are back-up methods to reduce delamination when drilling the open flat-plate composite structure, but none for drilling into the curved-surface or hollow-shape structures. This study describes an innovative method using electromagnet and the deformable inexpensive colloid mixed with iron powder to produce magnetic back-up force at drilling exit to suppress delamination in industrial tube parts. The delamination extent can be reduced by 60–80%. The optimal volume ratio of powder-to-colloid is found 1:3. 相似文献
40.
T. L. Su L. C. Tsao S. Y. Chang T. H. Chuang 《Journal of Materials Engineering and Performance》2002,11(5):481-486
The interfacial reactions of liquid Sn and Sn-3.5Ag solders with Ag thick films are investigated in the temperature range
from 250–325 °C, and the morphology of intermetallic compounds formed after such soldering reactions is observed. In kinetics
analysis of the growths of intermetallic compounds, it was found that both Sn/Ag and Sn-3.5Ag/Ag reactions were interfacial-controlled,
and the growth rates for both cases were similar. The rate of Ag dissolution into liquid solder attendant on the formation
of interfacial intermetallic compounds after Sn/Ag reaction was about four times higher than that after Sn-3.5Ag/Ag reaction,
as evidenced by experimental results. 相似文献