全文获取类型
收费全文 | 766篇 |
免费 | 26篇 |
专业分类
电工技术 | 4篇 |
综合类 | 3篇 |
化学工业 | 140篇 |
金属工艺 | 6篇 |
机械仪表 | 37篇 |
建筑科学 | 54篇 |
矿业工程 | 1篇 |
能源动力 | 10篇 |
轻工业 | 166篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
无线电 | 29篇 |
一般工业技术 | 171篇 |
冶金工业 | 71篇 |
原子能技术 | 5篇 |
自动化技术 | 86篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 7篇 |
2018年 | 16篇 |
2017年 | 15篇 |
2016年 | 12篇 |
2015年 | 23篇 |
2014年 | 19篇 |
2013年 | 46篇 |
2012年 | 70篇 |
2011年 | 66篇 |
2010年 | 29篇 |
2009年 | 27篇 |
2008年 | 61篇 |
2007年 | 56篇 |
2006年 | 43篇 |
2005年 | 25篇 |
2004年 | 37篇 |
2003年 | 30篇 |
2002年 | 23篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 6篇 |
1998年 | 20篇 |
1997年 | 23篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1956年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有792条查询结果,搜索用时 15 毫秒
21.
Vinderola G Marcó MB Guglielmotti DM Perdigón G Giraffa G Reinheimer J Quiberoni A 《International journal of food microbiology》2007,116(1):96-102
Three commercial phage sensitive Lactobacillus delbrueckii strains (identified as Ab(1), YSD V and Ib(3)), and four spontaneous phage-resistant mutants isolated from them were tested for their capacity to activate the gut mucosal immune response in mice, as indicated by the numbers of IgA-producing cells. Random Amplified Polymorphic DNA (RAPD) analysis revealed a strong genetic homology between the sensitive strains and their respective derivatives. The phage-resistant mutants exhibited high levels of phage resistance, elevated stability of this phenotype and technological properties comparable to those of their respective parent strains. The tolerance to acidic conditions, bile salts and lysozyme was strain dependent and total cell viability losses as a result of exposure to all three stresses ranged from 2.0 to 3.7 log units. All the strains were highly resistant to a simulated gastric solution of pH 3, while significant additional losses in cell viability were observed when acid treated cells were exposed to bile salts and lysozyme. BALB/c mice received pure cultures of Lb. delbrueckii sensitive and phage-resistant strains for 2, 5 or 7 consecutive days. The ability of the parent strains to activate the small intestine immune response was preserved or enhanced in phage-resistant mutants. The maximal proliferation of IgA(+) cells was observed at day 5 or 7, depending on the strain. Mutants isolated in this study using natural selection strategies had improved phage resistance, adequate technological properties and satisfactory gut mucosal immunostimulation ability, and so would be good candidates for industrial applications in functional foods. 相似文献
22.
23.
24.
Phenylalanine Ammonia‐Lyase‐Catalyzed Deamination of an Acyclic Amino Acid: Enzyme Mechanistic Studies Aided by a Novel Microreactor Filled with Magnetic Nanoparticles 下载免费PDF全文
Diána Weiser Dr. László Csaba Bencze Gergely Bánóczi Ferenc Ender Dr. Róbert Kiss Eszter Kókai Dr. András Szilágyi Prof. Dr. Beáta G. Vértessy Dr. Ödön Farkas Dr. Csaba Paizs Prof. Dr. László Poppe 《Chembiochem : a European journal of chemical biology》2015,16(16):2283-2288
Phenylalanine ammonia‐lyase (PAL), found in many organisms, catalyzes the deamination of l ‐phenylalanine (Phe) to (E)‐cinnamate by the aid of its MIO prosthetic group. By using PAL immobilized on magnetic nanoparticles and fixed in a microfluidic reactor with an in‐line UV detector, we demonstrated that PAL can catalyze ammonia elimination from the acyclic propargylglycine (PG) to yield (E)‐pent‐2‐ene‐4‐ynoate. This highlights new opportunities to extend MIO enzymes towards acyclic substrates. As PG is acyclic, its deamination cannot involve a Friedel–Crafts‐type attack at an aromatic ring. The reversibility of the PAL reaction, demonstrated by the ammonia addition to (E)‐pent‐2‐ene‐4‐ynoate yielding enantiopure l ‐PG, contradicts the proposed highly exothermic single‐step mechanism. Computations with the QM/MM models of the N‐MIO intermediates from l ‐PG and l ‐Phe in PAL show similar arrangements within the active site, thus supporting a mechanism via the N‐MIO intermediate. 相似文献
25.
Aboitiz N Vila-Perelló M Groves P Asensio JL Andreu D Cañada FJ Jiménez-Barbero J 《Chembiochem : a European journal of chemical biology》2004,5(9):1245-1255
HEV32, a 32-residue, truncated hevein lacking eleven C-terminal amino acids, was synthesized by solid-phase methodology and correctly folded with three cysteine bridge pairs. The affinities of HEV32 for small chitin fragments--in the forms of N,N',N"-triacetylchitotriose ((GlcNAc)3) (millimolar) and N,N',N",N"',N",N"'-hexaacetylchitohexaose ((GlcNAc)6) (micromolar)--as measured by NMR and fluorescence methods, are comparable with those of native hevein. The HEV32 ligand-binding process is enthalpy driven, while entropy opposes binding. The NMR structure of ligand-bound HEV32 in aqueous solution was determined to be highly similar to the NMR structure of ligand-bound hevein. Solvated molecular-dynamics simulations were performed in order to monitor the changes in side-chain conformation of the binding site of HEV32 and hevein upon interaction with ligands. The calculations suggest that the Trp21 side-chain orientation of HEV32 in the free form differs from that in the bound state; this agrees with fluorescence and thermodynamic data. HEV32 provides a simple molecular model for studying protein-carbohydrate interactions and for understanding the physiological relevance of small native hevein domains lacking C-terminal residues. 相似文献
26.
László Lőrincz Máté Zsemberi György Bánsághi Tamás Sohajda Edit Székely 《化学工程与技术》2018,41(7):1466-1472
Chiral molecules, especially enantiomers and diastereomers of purity > 99 %, present a significant market share within the chemical, pharmaceutical, and flavor industries. Antisolvent precipitations, both batch and semicontinuous operations to serve the current trends in flow chemistry were demonstrated to be environmentally benign and efficient tools in achieving high optical purities. Although salts are known to be insoluble in supercritical CO2, instabilities of the nascent salts were detected and applied for increasing efficiency. Diastereomeric excess values of the crystalline products exceeded 99 % in maximum of three consecutive steps both by repeated resolution with half molar equivalent of the amine to the acid and by direct recrystallization of the salts. 相似文献
27.
Copper(II) complexes of several hydroxyflavones were prepared and characterised through their physico-chemical properties. The nuclease activity of three synthesised complexes is reported. These copper(II) complexes present more nuclease activity than the ligands and the copper(II) ion. 相似文献
28.
Laura E. Pedró Rosa D. Rajasekhar Reddy Dr. Sherry F. Queener Prof. Lawrence W. Miller Prof. 《Chembiochem : a European journal of chemical biology》2009,10(9):1462-1464
Antifolate labels : Molecules that bind specifically and with high affinity to proteins can be developed into powerful tools for chemical biology. The interaction between substituted 5‐benzyl pyrimidines and dihydrofolate reductase can be exploited for chemically labeling fusion proteins in mammalian cells.
29.
István Szilágyi Ottó Berkesi Mónika Sipiczki László Korecz Antal Rockenbauer István Pálinkó 《Catalysis Letters》2009,127(3-4):239-247
In order to find highly active and selective oxygen-transfer catalysts with appreciable durability, Cu(II)–histidine complexes were covalently grafted onto a chlorinated polystyrene resin as copper-containing enzyme mimics. The Cu(II)-histidine complexes and the mobile polymer were to resemble the active center and the proteomic skeleton of the enzymes, respectively. The resulting heterogenized complexes were expected to be nearly so active and more durable catalysts that are easier to recycle than their homogeneous counterparts. The substances were tested in a superoxide radical anion dismutation reaction. Control for the syntheses was exerted by protecting either the N-terminal or the C-terminal of the covalently grafted l-histidine molecules. During the preparative work generally applied methods of synthetic organic chemistry (alkylation or esterification) were used. Various anchored complexes were prepared and characterized by classical analytical methods, different forms of spectroscopy as well as molecular modeling. The covalently grafted complexes having the protected amino acids as ligands displayed remarkably high activities in the superoxide dismutase (SOD) test reaction. 相似文献
30.
Pettersson S Pérez-Nueno VI Ros-Blanco L Puig de La Bellacasa R Rabal MO Batllori X Clotet B Clotet-Codina I Armand-Ugón M Esté J Borrell JI Teixidó J 《ChemMedChem》2008,3(10):1549-1557
HIV cell fusion and entry have been validated as targets for therapeutic intervention against infection. Bicyclams were the first low-molecular-weight compounds to show specific interaction with CXCR4. The most potent bicyclam was AMD3100, in which the two cyclam moieties are tethered by a 1,4-phenylenebis(methylene) bridge. It was withdrawn from clinical trials owing to its lack of oral bioavailability and cardiotoxicity. We have designed a combinatorial library of non-cyclam polynitrogenated compounds by preserving the main features of AMD3100. At least two nitrogen atoms on each side of the p-phenylene moiety, one in the benzylic position and the other(s) in the heterocyclic system were maintained, and the distances between them were similar to the nitrogen atom distances in cyclam. A selection of diverse compounds from this library were prepared, and their in vitro activity was tested in cell cultures against HIV strains. This led to the identification of novel potent CXCR4 coreceptor inhibitors without cytotoxicity at the tested concentrations. 相似文献