全文获取类型
收费全文 | 1005篇 |
免费 | 30篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 74篇 |
综合类 | 3篇 |
化学工业 | 312篇 |
金属工艺 | 31篇 |
机械仪表 | 21篇 |
建筑科学 | 22篇 |
能源动力 | 53篇 |
轻工业 | 95篇 |
石油天然气 | 1篇 |
无线电 | 48篇 |
一般工业技术 | 179篇 |
冶金工业 | 64篇 |
原子能技术 | 47篇 |
自动化技术 | 88篇 |
出版年
2023年 | 10篇 |
2022年 | 15篇 |
2021年 | 31篇 |
2020年 | 19篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 18篇 |
2016年 | 34篇 |
2015年 | 21篇 |
2014年 | 37篇 |
2013年 | 73篇 |
2012年 | 52篇 |
2011年 | 71篇 |
2010年 | 46篇 |
2009年 | 44篇 |
2008年 | 53篇 |
2007年 | 50篇 |
2006年 | 50篇 |
2005年 | 33篇 |
2004年 | 36篇 |
2003年 | 30篇 |
2002年 | 18篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1966年 | 1篇 |
1964年 | 2篇 |
排序方式: 共有1038条查询结果,搜索用时 15 毫秒
111.
Wen‐xue Zhang Zong‐wei Qiao Toru Shigematsu Yue‐qin Tang Cheng Hu Shigeru Morimura Kenji Kida 《Journal of the Institute of Brewing》2005,111(2):215-222
Denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene analysis were carried out to analyze the bacterial community in Zaopei during production of Chinese Luzhou‐flavor liquor. Primers PRBA338F and PRUN518R were used for DGGE. Polymerase chain reaction (PCR) for clone analysis was preformed with primers EU27F and 1490R. The results by DGGE showed that with increasing fermentation time the diversity of bacteria in Zaopei decreased and after one week, only one bacterium phylotype was dominant. Gene clone libraries (16S rRNA) containing 55 clonal sequences were constructed. The bacterial diversity shift observed by DGGE was also shown by the clone library analysis. Bacteria closely related to Lactobacillus acetotolerans appeared to play a key role during Chinese liquor fermentation. 相似文献
112.
A procedure for micro stereospecific analysis of triacyl-sn-glycerols (TGs) by high-performance liquid chromatography (HPLC) on a chiral column is presented. TGs were partially hydrolyzed
with ethyl magnesium bromide, and total products were immediately converted to 3,5-dinitro-phenylurethane derivatives. Each
of the 1- and 2-monoacylglycerol (MG) derivatives was isolated by HPLC on a silica column. The 1-MGs were resolved intosn-1 andsn-3 MG fractions by HPLC on a Sumichiral OA-4100 column (Sumitomo Chemical, Osaka, Japan). Fatty acid methyl esters obtained
from thesn-1,sn-2 andsn-3 MG fractions were analyzed by gas-liquid chromatography on a capillary column. Analyses of standard TGs showed that, even
with 1 mg of sample, accuracy was comparable to that obtained with 100-mg samples. Applying this procedure to the stereospecific
analysis of 5 mg of jujube pulp, TGs revealed the positional distribution of the (n-5) series of monounsaturated fatty acids
they contained.
Honored Student Award Address presented at the 83rd AOCS Annual Meeting held in Toronto, Canada, May 10–14, 1992. 相似文献
113.
Fountain flow for isothermal viscoelastic fluids is simulated by a numerical method based on a combination of a finite element method and a finite volume method. For the treatment of moving free surfaces, a fringe element generation method is used. Circulating flow and elongation in the transverse direction at the melt front are simulated well. Numerical results also suggest that circulation in fountain flow and viscoelastic retardation may give rise to symmetric V-shaped patterns of birefringence between the center-plane and wall. Such information on molecular orientation in fountain flow is important for physical properties of thick molded products. 相似文献
114.
Tantalum powder production by magnesiothermic reduction of tantalum pentachloride (TaCl5) through an electronically mediated reaction (EMR) has been examined. Feed material, TaCl5, and reductant magnesium alloy were charged into electronically isolated locations in the molten salt (e.g. NaCl–KCl–MgCl2) at 1073 K. After providing external path for electron flow, the current flow between the feed and the reductant locations was monitored. A large current, more than 1 A, was detected during the reaction and tantalum powder with low nickel and silver content was obtained, although liquid Mg–Ag–Ni alloy was used as the reductant. This clearly demonstrates that tantalum powder can be produced by electronically mediated reaction (EMR) without direct physical contact between the feed (TaCl5) and the reductant (magnesium). The feasibility of tantalum reduction using Dy2+ ions dissolved in molten salt has also been demonstrated by utilizing molten salt containing DyCl2 as a reaction mediator. The mechanism of magnesiothermic reduction of TaCl5 in the molten salt is discussed using isothermal chemical potential diagrams. 相似文献
115.
Fumi Osawa Toshio Fujii Takehisa Nishida Nobuki Tada Toru Ohnishi Osamu Kobayashi Toshihiro Komeda Satoshi Yoshida 《Yeast (Chichester, England)》2009,26(9):485-496
Industrial production of L ‐lactic acid, which in polymerized form as poly‐lactic acid is widely used as a biodegradable plastic, has been attracting world‐wide attention. By genetic engineering we constructed a strain of the Crabtree‐negative yeast Candida boidinii that efficiently produced a large amount of L ‐lactic acid. The alcohol fermentation pathway of C. boidinii was altered by disruption of the PDC1 gene encoding pyruvate decarboxylase, resulting in an ethanol production that was reduced to 17% of the wild‐type strain. The alcohol fermentation pathway of the PDC1 deletion strain was then successfully utilized for the synthesis of L ‐lactic acid by placing the bovine L ‐lactate dehydrogenase‐encoding gene under the control of the PDC1 promoter by targeted integration. Optimizing the conditions for batch culture in a 5 l jar‐fermenter resulted in an L ‐lactic acid production reaching 85.9 g/l within 48 h. This productivity (1.79 g/l/h) is the highest thus far reported for L ‐lactic acid‐producing yeasts. DDBJ/EMBL/GenBank nucleotide database with Accession Nos. AB440630 and AB440631. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
116.
Ralph A. Dalla Betta James C. Schlatter David K. Yee Daniel G. Loffler Toru Shoji 《Catalysis Today》1995,26(3-4):329-335
A catalytic combustion system has been developed which feeds full fuel and air to the catalyst but avoids exposure of the catalyst to the high temperatures responsible for deactivation and thermal shock fracture of the supporting substrate. The combustion process is initiated by the catalyst and is completed by homogeneous combustion in the post catalyst region where the highest temperatures are obtained. Catalysts have been demonstrated that operate at inlet temperatures as low as 320°C at 11 atm total pressure and conditions typical of high performance industrial gas turbines. The ignition temperature is shown to correlate with the specific catalytic activity of the washcoat layer over a rather broad range of activities. A reaction model has been developed that can predict ignition behavior from the measured catalytic activity. 相似文献
117.
Protein import into the nucleus is generally considered to involve specific nuclear localization signals (NLS) though it is becoming increasingly clear that efficient and well controlled import of proteins which lack a canonical NLS also occurs in cells. Human immunodeficiency virus type 1 (HIV-1) Vpr is one such protein which does not have an identifiable canonical NLS and yet efficiently localizes to the nuclear compartment. Here, we use confocal microscopy to demonstrate that mutations in the putative central hydrophobic helix of Vpr result in the retention of the protein in highly localized ring-like structures around the nuclear periphery with striking impairment in their ability to enter the nuclear interior. By characterizing other biological activities associated with this protein, such as its ability to incorporate into budding virions and its ability to arrest cells in G2, we show that this helical domain is specific for the nuclear translocation of the protein with very little effect on these other functions. Interestingly, however, perturbation of this helical motif also perturbs the protein's ability to augment viral replication in primary human macrophages indicating that the integrity of this secondary structure is essential for optimal infection in these non-dividing cells. 相似文献
118.
S Nonoyama A Etzioni H Toru DP Ruggerie D Lewis S Pollack A Aruffo JI Yata HD Ochs 《Canadian Metallurgical Quarterly》1998,28(2):589-598
Major histocompatibility complex (MHC) class II deficiency (bare lymphocyte syndrome, BLS) is a rare primary immunodeficiency classified as a subgroup of severe combined immunodeficiency. We studied T and B lymphocyte function by examining the CD40 ligand/CD40 system in three BLS patients from two unrelated families. CD40 ligand expression by maximally activated BLS T cells was diminished. This abnormality may represent immunological na?veté rather than a general T cell defect, since expression of activation marker CD69 and proliferative responses to PHA or anti-CD3 were normal, and BLS T cells primed and restimulated in vitro expressed normal amounts of CD40 ligand. BLS B cells proliferated and produced IgE if stimulated with anti-CD40 or soluble CD40 ligand and IL-4. Activation of BLS B cells with soluble CD40 ligand and IL-4 induced normal expression of activation markers, although MHC class II expression remained absent. Depressed antibody titers, lack of amplification and failure to undergo isotype switching in response to immunization with bacteriophage phi x 174 demonstrated defective T cell help. We conclude that BLS B cells are functionally normal if appropriately stimulated, and that the defective humoral immunity observed may be related to diminished expression of CD40 ligand on BLS T cells. 相似文献
119.
Rapid and practical separations of 1,2-and 2,3-diacyl-and dialkyl-sn-glycerol enantimers as their 3,5-dinitrophenylurethane derivatives were carried out by normal-phase high performance liquid
chromatography on a chiral stationary phase, N-(R)-1-(α-naphthyl)ethylaminocarbonyl-(S)-valine chemically bonded to γ-aminopropyl silanized silica. Complete separations of the racemates into enantiomers were
achieved for both of the diacyl-and dialkylglycerols within 10 min using a stainless steel column (25 cm long) packed with
the 5-μ particles, an isocratic elution with a mixture of hexane/ethylene dichloride/ethanol as a mobile phase and a UV detector.
Thesn-1,2-enantiomers were eluted ahead of the correspondingsn-2,3-enantiomers. Satisfactory separation of thesn-1,3-diacylglycerols from the corresponding enantiomers and the separation of the homologues differing in acyl and alkyl groups
were also observed. The formations of hydrogen bonding and charge transfer complex between the urethane derivatives and the
stationary phase may contribute to the enantiomer separations. 相似文献
120.
Toru Takagi Naoko Wakasa Kazuo Miyashita 《Journal of the American Oil Chemists' Society》1987,64(9):1320-1323
The determination of conjugated diene formation revealed that the mol % conversions of allcis-6,9,12-octadecatrienoic acid [γ-linolenic, 18:3(n-6)], allcis-5,8,11,14-eicosatetraenoic acid [arachidonic, 20:4(n-6)], allcis-5,8,11,14,17-eicosapentaenoic acid [20:5(n-3)], and allcis-4,7,10,13,16,19-docosahexaenoic acid [22:6(n-3)] into conjugated diene products by soybean lipoxygenase-1 at pH 9.0 were
84, 86, 60 and 40% of that of allcis-9,12-octadecadienoic acid [linoleic, 18:2(n-6)], respectively. On the other hand, the conversions of allcis-9,12,15-octadecatrienoic acid [α-linolenic, 18:3(n-3)], allcis-5,9,12-octadecatrienoic acid (c5,c9,c12-18:3), andtrans-5,cis-9,cis-12-octadecatrienoic acid (t5,c9,c12-18:3) were equal to that of 18:2(n-6). The lowering of the conjugated diene formation
in the oxidation of 18:3(n-6), 20:4(n-6), 20:5(n-3), and 22:6(n-3) by the lipoxygenase was thought to be caused by the further
oxidation of conjugated diene monohydroperoxides to yield conjugated triene products. For this reason, the conventional lipoxygenase
method gave erroneous values forcis,cis-methylene interrupted polyunsaturated fatty acids (PUFA) in oils containing a large amount of 20:5(n-3) and 22:6(n-3) such
as fish oils. However, by changing the pH of reaction mixtures from 9.0 to 11.0, the secondary oxidation of conjugated diene
monohydroperoxides was completely inhibited, and the PUFA values in fish oils obtained by this improved method were in good
agreement with those obtained by a GLC method. 相似文献