全文获取类型
收费全文 | 2347篇 |
免费 | 98篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 132篇 |
综合类 | 3篇 |
化学工业 | 718篇 |
金属工艺 | 53篇 |
机械仪表 | 74篇 |
建筑科学 | 77篇 |
能源动力 | 107篇 |
轻工业 | 302篇 |
水利工程 | 13篇 |
石油天然气 | 1篇 |
无线电 | 107篇 |
一般工业技术 | 441篇 |
冶金工业 | 58篇 |
原子能技术 | 108篇 |
自动化技术 | 261篇 |
出版年
2023年 | 23篇 |
2022年 | 33篇 |
2021年 | 76篇 |
2020年 | 24篇 |
2019年 | 35篇 |
2018年 | 74篇 |
2017年 | 52篇 |
2016年 | 97篇 |
2015年 | 49篇 |
2014年 | 89篇 |
2013年 | 165篇 |
2012年 | 142篇 |
2011年 | 174篇 |
2010年 | 124篇 |
2009年 | 151篇 |
2008年 | 158篇 |
2007年 | 116篇 |
2006年 | 103篇 |
2005年 | 98篇 |
2004年 | 83篇 |
2003年 | 74篇 |
2002年 | 80篇 |
2001年 | 49篇 |
2000年 | 33篇 |
1999年 | 40篇 |
1998年 | 44篇 |
1997年 | 32篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有2455条查询结果,搜索用时 15 毫秒
201.
202.
Hidetaka Kawakita Hiroyasu Masunaga Kanako Nomura Kazuya Uezu Isamu Akiba Satoshi Tsuneda 《Journal of Porous Materials》2007,14(4):387-391
Protein adsorption was performed by a polymer brush prepared by atom-transfer radical polymerization (ATRP) to a porous inorganic
membrane. The porous inorganic membrane, Shirasu Porous Glass made from silica, was modified with a halogen-containing compound
to bind the active species for the polymerization. Glycidyl methacrylate was polymerized from the halogen compound by ATRP
for a prescribed time, and subsequently chemically modified. The progression of the chemical modification allowed the membrane
to lower the phosphate-buffer flux of the porous membrane due to the attachment of the polymer brush. Bovine serum albumin
(BSA), as a model protein, was adsorbed at 12 mg per gram of the membrane in permeating BSA solution through the polymer-brush-attached
porous membrane. 相似文献
203.
Takatoshi Shindo Hideki Motoyama Toru Miki Mikihisa Saito Akiyori Matsueda Noriyasu Honma Tomohito Hida Kazuo Shinjo Kiyotaka Hayashi Hayato Awazu Katsuhisa Makabe Masato Fujikawa Satoshi Kurihara Masashi Sato 《IEEJ Transactions on Electrical and Electronic Engineering》2016,11(Z2):S28-S33
Nine electric power companies in Japan have been collecting lightning data with lightning location systems. Five years of the lightning data (2009–2013) are summarized and analyzed in this paper. The recent annual number of lightning flashes of which the current is more than 10 kA in Japan is around 1 million. The variations of lightning occurrence characteristics by areas, seasons, and so on, are clarified. Meteorological conditions that may affect lightning occurrence are also discussed. Furthermore, we show that there is a clear correlation between the number of lightning strikes and the outage rate of transmission lines. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
204.
Satoshi Kubo Koh Hashida Shojiro Hishiyama Tatsuhiko Yamada Shuji Hosoya 《木材化学与工艺学杂志》2015,35(1):62-72
In the alkaline decomposition of a β-O-4 type lignin model compound (erythro-guaiacylglycerol-β-guaiacyl ether, compound 1), an isomeric pair of C6C2 enol-ether (2-methoxy-4-[2-(2-methoxyphenoxy)-vinyl]-phenol, compound 2) was detected as the main decomposition product with no trace of C6C3 enol-ether (4-[3-hydroxy-1-(2-methoxyphenoxy)-propenyl]-2-methoxy-phenol, compound 3) or other dimers. In contrast, compound 2 was not detected in the alkaline decomposition products of compound 3. Under alkaline conditions, the γ-hydroxymethyl group of compound 3 was reduced to form 2-methoxy-4-[1-(2-methoxyphenoxy)-propenyl]-phenol (compound 4). In the HSQC analysis of soda lignin, the formation of substructures of C6C2 type enol-ether (related to compound 2) was confirmed. However, no substructures related to compound 4, which could be formed if a substructure of C6C3 type enol-ether was formed under alkaline conditions, were detected. Therefore, it could be concluded that C6C3 type enol-ethers could not be intermediates of alkaline decomposition products of lignin. 相似文献
205.
206.
Eisuke Watanabe Junko Fujii Kaori Kojima Satoshi Iwatsuki Masahiko Inamo Hideo D. Takagi Koji Ishihara 《Inorganic chemistry communications》2010,13(12):1406-1409
Kinetic studies were performed on the reactions of phenylboronic acid with L-lactic acid and mandelic acid in acidic aqueous and alkaline solutions in order to specify reactive species in these reactions. It was confirmed that the diprotonated ligand (H2L: L-lactic acid or mandelic acid) is less reactive than the monoprotonated ligand (HL?: L-lactate ion or mandelate ion), which made possible direct determination of the rate constants of phenylboronic acid (PhB(OH)2) and its conjugate base, phenylboronate ion (PhB(OH)3?). It was found that PhB(OH)2 is more reactive than PhB(OH)3?. On the basis of kinetic results, it was concluded that the most reactive species are PhB(OH)2 and HL? at physiological pH 7.4, so the reaction in the boronic acid-based sensor for L-lactate mainly would occur between these species. 相似文献
207.
Okada M Makino A Nakajima M Okuyama S Furukawa S Furukawa Y 《International journal of molecular sciences》2010,11(10):4114-4123
Our previous study indicated that both 17β-estradiol (E2), known to be an endogenous estrogen, and bisphenol A (BPA), known to be a xenoestrogen, could positively influence the proliferation or differentiation of neural stem/progenitor cells (NS/PCs). The aim of the present study was to identify the signal transduction pathways for estrogenic activities promoting proliferation and differentiation of NS/PCs via well known nuclear estrogen receptors (ERs) or putative membrane-associated ERs. NS/PCs were cultured from the telencephalon of 15-day-old rat embryos. In order to confirm the involvement of nuclear ERs for estrogenic activities, their specific antagonist, ICI-182,780, was used. The presence of putative membrane-associated ER was functionally examined as to whether E2 can activate rapid intracellular signaling mechanism. In order to confirm the involvement of membrane-associated ERs for estrogenic activities, a cell-impermeable E2, bovine serum albumin-conjugated E2 (E2-BSA) was used. We showed that E2 could rapidly activate extracellular signal-regulated kinases 1/2 (ERK 1/2), which was not inhibited by ICI-182,780. ICI-182,780 abrogated the stimulatory effect of these estrogens (E2 and BPA) on the proliferation of NS/PCs, but not their effect on the differentiation of the NS/PCs into oligodendroglia. Furthermore, E2-BSA mimicked the activity of differentiation from NS/PCs into oligodendroglia, but not the activity of proliferation. Our study suggests that (1) the estrogen induced proliferation of NS/PCs is mediated via nuclear ERs; (2) the oligodendroglial generation from NS/PCs is likely to be stimulated via putative membrane-associated ERs. 相似文献
208.
Byappanahalli MN Whitman RL Shively DA Ferguson J Ishii S Sadowsky MJ 《Water research》2007,41(16):3649-3654
We previously reported that the macrophytic green alga Cladophora harbors high densities (up to 10(6) colony-forming units/g dry weight) of the fecal indicator bacteria, Escherichia coli and enterococci, in shoreline waters of Lake Michigan. However, the population structure and genetic relatedness of Cladophora-borne indicator bacteria remain poorly understood. In this study, 835 E. coli isolates were collected from Cladophora tufts (mats) growing on rocks from a breakwater located within the Indiana Dunes National Lakeshore in northwest Indiana. The horizontal fluorophore enhanced rep-PCR (HFERP) DNA fingerprinting technique was used to determine the genetic relatedness of the isolates to each other and to those in a library of E. coli DNA fingerprints. While the E. coli isolates from Cladophora showed a high degree of genetic relatedness (92% similarity), in most cases, however, the isolates were genetically distinct. The Shannon diversity index for the population was very high (5.39). Both spatial and temporal influences contributed to the genetic diversity. There was a strong association of isolate genotypes by location (79% and 80% for lake- and ditch-side samplings, respectively), and isolates collected from 2002 were distinctly different from those obtained in 2003. Cladophora-borne E. coli isolates represented a unique group, which was distinct from other E. coli isolates in the DNA fingerprint library tested. Taken together, these results indicate that E. coli strains associated with Cladophora may be a recurring source of indicator bacteria to the nearshore beach. 相似文献
209.
Relationships between Bacteroides 16S rRNA genetic markers and presence of bacterial enteric pathogens and conventional fecal indicators 总被引:1,自引:0,他引:1
Occurrence and prevalence of different bacterial enteric pathogens as well as their relationships with conventional (total and fecal coliforms) and alternative fecal indicators (host-specific Bacteroides 16S rRNA genetic markers) were investigated for various water samples taken from different sites with different degrees of fecal contamination. The results showed that a wide range of bacterial pathogens could be detected in both municipal wastewater treatment plant samples and in surface water samples. Logistic regression analysis revealed that total and human-specific Bacteroides 16S rRNA genetic markers showed significant predictive values for the presence of Escheriachia coli O-157, Salmonella, heat-labile enterotoxin (LT) of enterotoxigenic E. coli (ETEC), and heat-stable enterotoxin for human (STh) of ETEC. The probability of occurrence of these pathogenic bacteria became significantly high when the concentrations of human-specific and total Bacteroides 16S rRNA genetic markers exceeded 10(3) and 10(4) copies/100 mL. In contrast, Clostridium perfringens was detected at high frequency regardless of sampling sites and levels of Bacteroides 16S rRNA genetic markers. No genes related to Shigella spp., Staphylococcus aureus and Vibrio cholerae were detected in any samples analyzed in this study. Conventional indicator microorganisms had low levels of correlation with the presence of pathogens as compared with the alternative fecal indicators. These results suggested that real-time PCR-based measurement of alternative Bacteroides 16S rRNA genetic markers was a rapid and sensitive tool to identify host-specific fecal pollution and probably associated bacterial pathogens. However, since one fecal indicator might not represent the relative abundance of all pathogenic bacteria, viruses and protozoa, combined application of alternative indicators with conventional ones could provide more comprehensive pictures of fecal contamination, its source and association with pathogenic microorganisms. 相似文献
210.