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51.
Markus A. Durban Uwe T. Bornscheuer 《European Journal of Lipid Science and Technology》2007,109(5):469-473
Phospholipases C (PLC, EC 3.1.4.3) are enzymes that specifically hydrolyze the C‐O‐P bond in phospholipids, yielding sn‐1,2(2,3)‐diacylglycerides and the phosphate residue bearing the corresponding headgroup. The biochemical characterization of PLC requires methods for the reliable determination of their activity. Here, an assay is described in which the phosphate residue released by the PLC is cleaved with an alkaline phosphatase. The phosphate formed is then extracted with n‐butanol and quantified as phosphomolybate complex. The applicability of this method is demonstrated for a concentration range from 10 nM to 10 mM for a range of phospholipids bearing different headgroups in an aqueous and a two‐phase system. The method has the additional advantage that the crude enzyme can be used without the need for purification. 相似文献
52.
Imide‐containing ladder polyphenylsilsesquioxanes with high thermal stability and thermoplastic properties 下载免费PDF全文
This work reports for the first time the synthesis of ladder polyphenylsilsesquioxanes containing imide building blocks as parts of the main parallel chains. The ladder structure of the synthesized polymers was documented by means of small angle X‐ray scattering (SAXS) measurements. The obtained ladder polymers exhibit stability with respect to decomposition up to temperatures as high as 460°C; additionally, they have melting points far below their decomposition temperatures, which make them interesting candidate materials for thermoplastic processing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40085. 相似文献
53.
Conversion of a Mono‐ and Diacylglycerol Lipase into a Triacylglycerol Lipase by Protein Engineering 下载免费PDF全文
Dr. Dongming Lan Dr. Grzegorz Maria Popowicz Dr. Ioannis V. Pavlidis Pengfei Zhou Prof. Dr. Uwe T. Bornscheuer Prof. Dr. Yonghua Wang 《Chembiochem : a European journal of chemical biology》2015,16(10):1431-1434
Despite the fact that most lipases are believed to be active against triacylglycerides, there is a small group of lipases that are active only on mono‐ and diacylglycerides. The reason for this difference in substrate scope is not clear. We tried to identify the reasons for this in the lipase from Malassezia globosa. By protein engineering, and with only one mutation, we managed to convert this enzyme into a typical triacylglycerol lipase (the wild‐type lipase does not accept triacylglycerides). The variant Q282L accepts a broad spectrum of triacylglycerides, although the catalytic behavior is altered to some extent. From in silico analysis it seems that specific hydrophobic interactions are key to the altered substrate specificity. 相似文献
54.
Dominic Riedel Thomas Wurm Katharina Graf Matthias Rudolph Frank Rominger A. Stephen K. Hashmi 《Advanced Synthesis \u0026amp; Catalysis》2015,357(7):1515-1523
In a modular template synthesis, unsaturated NHC complexes of gold, palladium and platinum were synthesized from simple metal salts, isonitriles and amines with acetal or ketal groups. Upon the addition of amines with tethered acetal or ketal moieties to the metal‐activated isonitrile, first nitrogen acyclic carbene (NAC) complexes are formed. These undergo ring closure and elimination to the unsaturated NHC complexes upon addition of acid. This simple strategy opens an attractive and fast approach to NHC complexes of gold, palladium and platinum. The modular approach allows a fast modification and is well‐suited for the synthesis of unsymetrically and symmetrically substituted unsaturated NHC complexes.
55.
Mohamed M. Soumanou Uwe T. Bornscheuer Ulrich Menge Rolf D. Schmid 《Journal of the American Oil Chemists' Society》1997,74(4):427-433
Structured triglycerides (ST) that contain medium- and long-chain fatty acids were synthesized by lipase-catalyzed interesterification
between tricaprylin and peanut oil. To select appropriate enzymes, we investigated nine commercial lipase preparations for
their ability to hydrolyze pure triglycerides as well as natural oils. Three microbial lipases from Rhizomucor miehei (RML), Candida sp. (CSL), and Chromobacterium viscosum (CVL) gave good results, and immobilized preparations were used in the interesterification. RML gave the highest yields of
ST (73%, 40°C), although its hydrolytic activity toward triolein was low. As the temperature was raised to 50°C, the yield
of ST increased to 79%. After 120 h reaction time, remaining activities were high for CSL (71%), moderate for CVL (48%), and
low for RML (20%).
Parts of this paper were presented as a poster at the Biochemical Engineering Conference IX, May 1995, Davos, Switzerland. 相似文献
56.
57.
Udo Schubert Uwe Kruger Günter Wozny Harvey Arellano‐Garcia 《American Institute of Chemical Engineers》2012,58(5):1513-1523
In this work, an input reconstruction scheme for detecting and isolating sensor, actuator, and process faults is proposed. The scheme uses model‐based and statistical‐based FDI methods, which yields an improved analysis of abnormal operation conditions in chemical processes. The main advantage of the proposed approach over existing works lies in the reconstruction of system inputs and the subsequent estimation of fault signatures. This advantage is demonstrated through simulation examples and the analysis of recorded process data from a reactive batch distillation column. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
58.
Emanuel Ionescu Benjamin Papendorf Hans-Joachim Kleebe Hergen Breitzke Katharina Nonnenmacher Gerd Buntkowsky Ralf Riedel 《Journal of the European Ceramic Society》2012,32(9):1873-1881
The polymer-to-ceramic transformation of a hafnium alkoxide-modified polysilazane was investigated via thermogravimetric analysis coupled with in situ mass spectrometry (TG/MS), nuclear magnetic resonance (MAS NMR) and transmission electron microscopy (TEM). The results indicate that the structural evolution of the polysilazane upon ceramization is strongly affected by the modification with hafnium alkoxide. Thus, the content of carbon in the ceramic backbone was relatively low, whereas a large amount of SiN4 sites and a segregated carbon phase was present in the sample. Furthermore, this study revealed the formation of a SiHfCNO amorphous single phase ceramic via pyrolysis of the polymer at 700 °C, whereas at higher pyrolysis temperatures precipitation of hafnia was observed, leading to an amorphous hafnia/silicon carbonitride ceramic nanocomposite. The precipitation of hafnia was shown to not rely on decomposition processes, but to be a result of rearrangement reactions occurring within the ceramic material. 相似文献
59.
Ulrich Degenhardt Frank Stegner Christian Liebscher Uwe Glatzel Karl Berroth Walter Krenkel Günter Motz 《Journal of the European Ceramic Society》2012,32(9):1893-1899
A flexible method is presented, which enables the fabrication of porous as well as dense Si3N4/nano-SiC components by using Si3N4 powder and a preceramic polymer (polycarbosilazane) as alternative ceramic forming binder. The SiCN polymer benefits consolidation as well as shaping of the green body and partially fills the interstices between the Si3N4 particles. Cross-linking of the precursor at 300 °C increases the mechanical stability of the green bodies and facilitates near net shape machining. At first, pyrolysis leads to porous ceramic bodies. Finally, subsequent gas pressure sintering results in dense Si3N4/nano-SiC ceramics. Due to the high ceramic yield of the polycarbosilazane binder, the shrinkage during sintering is significantly reduced from 20 to 15 lin.%. Investigations of the sintered ceramics reveal, that the microstructure of the Si3N4 ceramic contains approx. 6 vol.% nano-scaled SiC segregations, which are located both at the grain boundaries and as inclusions in the Si3N4 grains. 相似文献
60.
Williams CC Thang SH Hantke T Vogel U Seeberger PH Tsanaktsidis J Lepenies B 《ChemMedChem》2012,7(2):281-291
A series of well‐defined polymer–drug conjugates were prepared in order to modify the physical properties of a known cytotoxic drug, 7‐ethyl‐10‐hydroxycamptothecin (SN‐38), the active metabolite of irinotecan (CPT‐11). Reversible addition–fragmentation chain transfer (RAFT) polymerisation was used to covalently and site‐specifically append a defined N‐(2‐hydroxypropyl)methacrylamide (HPMA) polymer to SN‐38 using a graft‐from process. These poly‐HPMA–SN‐38 conjugates displayed excellent aqueous solubility and stability, whilst retaining the cytotoxic activity of the parent SN‐38. In vitro co‐culture assays containing both cancer and noncancer cell lines demonstrated the specificity of RAFT‐derived poly‐HPMA–SN‐38 conjugates for cancerous cells. The concept of post‐optimisation modification of small‐molecule drugs through a graft‐from polymer conjugation method is introduced. 相似文献