全文获取类型
收费全文 | 5503篇 |
免费 | 109篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 282篇 |
综合类 | 7篇 |
化学工业 | 1112篇 |
金属工艺 | 159篇 |
机械仪表 | 103篇 |
建筑科学 | 76篇 |
矿业工程 | 3篇 |
能源动力 | 119篇 |
轻工业 | 302篇 |
水利工程 | 8篇 |
石油天然气 | 17篇 |
无线电 | 563篇 |
一般工业技术 | 1091篇 |
冶金工业 | 1298篇 |
原子能技术 | 174篇 |
自动化技术 | 318篇 |
出版年
2023年 | 20篇 |
2022年 | 53篇 |
2021年 | 102篇 |
2020年 | 37篇 |
2019年 | 60篇 |
2018年 | 60篇 |
2017年 | 67篇 |
2016年 | 83篇 |
2015年 | 60篇 |
2014年 | 92篇 |
2013年 | 212篇 |
2012年 | 188篇 |
2011年 | 252篇 |
2010年 | 172篇 |
2009年 | 172篇 |
2008年 | 180篇 |
2007年 | 196篇 |
2006年 | 162篇 |
2005年 | 162篇 |
2004年 | 147篇 |
2003年 | 151篇 |
2002年 | 112篇 |
2001年 | 108篇 |
2000年 | 117篇 |
1999年 | 144篇 |
1998年 | 541篇 |
1997年 | 291篇 |
1996年 | 221篇 |
1995年 | 170篇 |
1994年 | 141篇 |
1993年 | 123篇 |
1992年 | 81篇 |
1991年 | 82篇 |
1990年 | 65篇 |
1989年 | 75篇 |
1988年 | 52篇 |
1987年 | 55篇 |
1986年 | 62篇 |
1985年 | 62篇 |
1984年 | 56篇 |
1983年 | 40篇 |
1982年 | 44篇 |
1981年 | 51篇 |
1980年 | 49篇 |
1979年 | 35篇 |
1978年 | 31篇 |
1977年 | 29篇 |
1976年 | 77篇 |
1975年 | 19篇 |
1974年 | 15篇 |
排序方式: 共有5632条查询结果,搜索用时 11 毫秒
991.
Yoshiyuki Mizushina Yoshihiro Takahashi Yoshihiro Sato Yasuhiro Yamaguchi Toshifumi Takeuchi Isoko Kuriyama Fumio Sugawara Hiromi Yoshida 《Food chemistry》2012
During the screening of selective DNA polymerase (pol) inhibitors, we isolated two glucosyl compounds, a cerebroside (glucosyl ceramide, AS-1-4, compound 1) and a steroidal glycoside (eleutheroside A, compound 2) from soybean (Glycine max L.). Compounds 1 and 2 selectively inhibited the activity of eukaryotic pol λ in vitro, with IC50 values of 12.2 and 9.1 μM, respectively. These compounds did not influence the activities of other eukaryotic pols including those from the A-family (pol γ), B-family (pols α, δ and ε), and Y-family (pols η, ι and κ), and also showed no effect on the activity of pol β which is of the same family (X) as pol λ. The tendency for in vitro pol λ inhibition by these compounds showed a positive correlation with the in vivo suppression of TPA (12-O-tetradecanoylphorbol-13-acetate)-induced inflammation in mouse ear. These results suggest that these glucosyl compounds from soybean may be useful for their anti-inflammatory properties. 相似文献
992.
Eun Young Park Yasushi Nakamura Kenji Sato Yasuki Matsumura 《Journal of the American Oil Chemists' Society》2012,89(3):477-484
We investigated the effects of amino acids and peptide on lipid oxidation in emulsion systems. For comparative purposes, we
also tested the antioxidant activity of ferulic acid, a typical phenolic antioxidant. Histidine and cysteine retarded lipid
oxidation (the amount of thiobarbituric acid [TBA]-reactive substances reached approximately 13 and 18 μM after 7 days, respectively),
whereas arginine, methionine, and tryptophan did not inhibit the progression of oxidation. Soy peptide also inhibited lipid
oxidation. Ferulic acid was found to be the most effective suppressor of lipid oxidation (TBA-reactive substances were suppressed
to <3 μM over 7 days). The antioxidant activities of soy peptide and ferulic acid were related to the purity of the emulsifier
used. The radical scavenging activities of soy peptide and ferulic acid were closely related to their inhibitory effects on
lipid oxidation. However, this was not the case for amino acids. Decreases in the turbidity of emulsions were closely related
to increases in TBA values. 相似文献
993.
Carbon nanohorns (CNHs) functionalized with aryl units, possessing ethylene glycol chains terminated to amine groups, were condensed with modified C60 carrying a free carboxylic acid group. Direct evidence for the covalent functionalization of CNHs was given by high-resolution transmission electron microscopy (HR-TEM) imaging of C60 present in that CNH hybrid material. In addition, it was found that C60 remained unaffected even after prolonged exposure to the electron beam. Finally, monitoring the wave motion of the connecting ethylene glycol chains, through sequential HR-TEM images, further proved the stability of the covalent bond that links the two carbon nanostructures. 相似文献
994.
Shionoiri N Sato T Fujimori Y Nakayama T Nemoto M Matsunaga T Tanaka T 《Journal of Bioscience and Bioengineering》2012,113(5):580-586
This study demonstrated the antiviral properties of copper iodide (CuI) nanoparticles against the non-enveloped virus feline calicivirus (FCV) as a surrogate for human norovirus. The effect of CuI nanoparticles on FCV infectivity to Crandell-Rees feline kidney (CRFK) cells was elucidated. The infectivity of FCV to CRFK cells was greatly reduced by 7 orders of magnitude at 1000μgml(-1) CuI nanoparticles. At the conditions, electron spin resonance (ESR) analysis proved hydroxyl radical production in CuI nanoparticle suspension. Furthermore, amino acid oxidation in the viral capsid protein of FCV was determined by nanoflow liquid chromatography-mass spectrometric (nano LC-MS) analysis. The use of CuI nanoparticles showed extremely high antiviral activity against FCV. The high antiviral property of CuI nanoparticles was attributed to Cu(+), followed by ROS generation and subsequent capsid protein oxidation. CuI nanoparticles could be proposed as useful sources of a continuous supply of Cu(+) ions for efficient virus inactivation. Furthermore, this study brings new insights into toxic actions of copper iodide nanoparticles against viruses. 相似文献
995.
J.C. Ribierre M. Sato A. Ishizuka T. Tanaka S. Watanabe M. Matsumoto S. Matsumoto M. Uchiyama T. Aoyama 《Organic Electronics》2012,13(6):999-1003
We report on the fabrication and the characterization of p-type organic field-effect transistors based on vapor-deposited J-aggregate bisazomethine dye thin films. The absorption spectra of this non-ionic organic semiconductor in the solid state show a strong influence of the film thickness on the J-aggregate formation. However, the electrical characteristics of the devices demonstrate that the hole transport properties do not vary significantly in films thicker than 100 nm. This is due to the fact that the J-aggregates are formed in this material at the surface of the crystalline grains and do not influence the semiconductor/gate dielectric interface and the charge transport properties of the devices. Hole field-effect mobilities as high as 2.4 × 10?4 cm2 V?1 s?1 were obtained and could be slightly improved by a solvent vapor treatment due to changes in the film crystallinity. Overall, this study demonstrates that J-aggregate bisazomethine dye thin films are good candidates for the realization of organic electronic devices. 相似文献
996.
We describe new heterologous modules for PCR-based gene targeting in the fission yeast Schizosaccharomyces pombe. Two bacterial genes, hph and nat, which display dominant drug-resistance phenotypes, are used as new selectable markers in these modules. Both genes have been used successfully in the budding yeast Saccharomyces cerevisiae, in which hph confers resistance to hygromycin B, while nat confers nourseothricin resistance (Goldstein and McCusker, 1999). Vector modules for gene disruption and C-terminal tagging with 3HA, 13Myc and GFP(S65T) are constructed using previously constructed pFA6a-MX6-derived plasmids (B?hler et al., 1998; Wach et al., 1997). In combination with the existing systems that are based upon the G418-resistance gene (kan), triple gene deletions or tags could be constructed. In addition a vector for one-step integration of a monomeric RFP (mRFP) to the C-terminus of proteins of interest is developed. Finally, oligonucleotides that allow a simple marker switch from kan to hph or nat, and vice versa, are described. The new constructs developed here should facilitate post-genomic molecular analysis of protein functions in fission yeast. 相似文献
997.
Dioscin Derived from Solanum melongena L. “Usukawamarunasu” Attenuates α‐MSH–Induced Melanogenesis in B16 Murine Melanoma Cells via Downregulation of Phospho‐CREB and MITF
下载免费PDF全文
![点击此处可从《Journal of food science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
998.
Effect of corn steep liquor on lettuce root rot (Fusarium oxysporum f.sp. lactucae) in hydroponic cultures 总被引:1,自引:0,他引:1
999.
Nakai M Ito J Sato K Noguchi J Kaneko H Kashiwazaki N Kikuchi K 《Reproduction (Cambridge, England)》2011,142(2):285-293
In pigs, although ICSI is a feasible fertilization technique, its efficiency is low. In general, injected pig sperm are insufficient to induce oocyte activation and embryonic development. Pretreatments for disrupting sperm membranes have been applied to improve the fertility of ICSI oocytes; however, we hypothesize that such pretreatment(s) may reduce the ability of the sperm to induce oocyte activation. We first evaluated the effects of sperm pretreatments (sonication (SO) to isolate the sperm heads from the tails, Triton X-100 (TX), and three cycles of repeated freezing/thawing (3×-FT) for disrupting sperm membranes) on the rate of pronucleus (PN) formation after ICSI. We found that oocytes injected with control (whole) sperm had higher rates of PN formation than those obtained after subjecting the sperm to SO, TX, and 3×-FT. The amounts of phospholipase Cζ (PLCζ), which is thought to be the oocyte-activating factor in mammalian sperm, in sperm treated by each method was significantly lower than that in whole untreated sperm. Furthermore, using immunofluorescence, it was found that in pig sperm, PLCζ was localized to both the post-acrosomal region and the tail area. Thus we demonstrated for the first time that sperm pretreatment leads to a reduction of oocyte-activating capacity. Our data also show that in addition to its expected localization to the sperm head, PLCζ is also localized in the tail of pig sperm, thus raising the possibility that injection of whole sperm may be required to attain successful activation in pigs. 相似文献
1000.
Potassium tungsten oxide nanofibers were successfully synthesized via a facile hydrothermal reaction route in the presence of sulfate. After reduction under a reductive atmosphere of H(2)(5 vol %)/N(2), the potassium tungsten oxide transformed to potassium tungsten bronze. Because of the lack of free electrons, the potassium tungsten oxide (K(x)WO(3+x/2)) showed no NIR shielding performance; however, the potassium tungsten bronze (K(x)WO(3)) showed promising optical characteristics such as high transmittance for visible light, as well as high shielding performance for near-infrared lights, indicating its potential application as a solar filter. Meanwhile, the potassium tungsten bronze (K(x)WO(3)) showed strong absorption of near-infrared light and instantaneous conversion of photoenergy to heat. 相似文献