全文获取类型
收费全文 | 1065篇 |
免费 | 47篇 |
国内免费 | 5篇 |
学科分类
工业技术 | 1117篇 |
出版年
2023年 | 16篇 |
2022年 | 166篇 |
2021年 | 101篇 |
2020年 | 34篇 |
2019年 | 26篇 |
2018年 | 46篇 |
2017年 | 36篇 |
2016年 | 44篇 |
2015年 | 25篇 |
2014年 | 40篇 |
2013年 | 57篇 |
2012年 | 56篇 |
2011年 | 73篇 |
2010年 | 42篇 |
2009年 | 53篇 |
2008年 | 46篇 |
2007年 | 33篇 |
2006年 | 24篇 |
2005年 | 31篇 |
2004年 | 17篇 |
2003年 | 20篇 |
2002年 | 31篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有1117条查询结果,搜索用时 0 毫秒
101.
Jaakko Heikkinen Irina Kurganova Valentin Lopes de Gerenyu Taru Palosuo Kristiina Regina 《Nutrient Cycling in Agroecosystems》2014,98(1):97-106
The collapse of Soviet Union in early 1990s led to abandonment of large area of arable land which is assumed to act as a carbon (C) sink. We studied the ability of two dynamic soil C models (Yasso07 and RothC) to predict changes in soil C content after cropland abandonment. The performance of the models was compared using the results of a long-term experiment in Pushchino, Moscow region (54°50′N, 37°35′E) in Russia. The experiment was divided in four combinations of fertilizer or mowing treatments on former cropland soil. The soil C content was determined in the year of establishment (1980) and thereafter in 1999 and 2004. The soil C stocks increased by about 1.5- to 1.8-fold during the study period. Both models predicted the overall change in soil C relatively well (modelling efficiency of Yasso07 and RothC were 0.60 and 0.73, respectively). According to the models, the soil gained on average 140–150 g C m?2 year?1 during the first 5 years after conversion of cropland to grassland. The C sequestration rate decreased to 40–50 g C m?2 year?1 after 20 years of land use change. The sequestration rates estimated in this study are comparable to the rates observed in other studies. 相似文献
102.
Felix Rivkin Irina Kuznetsova Nadezhda Ivanova Sergey Suhodolsky 《Soil Mechanics and Foundation Engineering》2002,39(1):42-43
Soil Mechanics and Foundation Engineering - 相似文献
103.
Stefan M Marius S Hritcu L Lucian H Mihasan M Marius M Pricop D Daniela P Gostin I Irina G Olariu RI Romeo-Iulian O Dunca S Simona D Melnig V Viorel M 《Journal of materials science. Materials in medicine》2011,22(4):789-796
In the present study, we report enhanced antimicrobial properties of 29 and 23 nm silver nanoparticles (Ag NPs) obtained by
electrochemical synthesis in poly(amide-hydroxyurethane) media. Antibacterial activity assessed by disk diffusion method indicates
that silver nanoparticles produced inhibition zones for both Escherichia coli and Staphylococcus aureus depending on silver concentration. The bacterial growth curve performed in the presence of silver nanoparticles showed a
stronger antibacterial effect at lower concentrations than those described in the earlier reports. The effect was both dose
and size dependent and was more pronounced against Gram negative bacteria than Gram positive one. The smallest Ag NPs used
had a bactericidal effect resulting in killing E. coli cells. Scanning electron microscopy analysis indicated major damage and morphology changes of the silver nanoparticles treated
bacterial cells. The major mechanism responsible for the antibacterial effect probably consists in clusters formation and
nanoparticles anchorage to the bacterial cell surface. 相似文献
104.
Kataeva IA Uversky VN Brewer JM Schubot F Rose JP Wang BC Ljungdahl LG 《Protein engineering, design & selection : PEDS》2004,17(11):759-769
Cellobiohydrolase CbhA from Clostridium thermocellum cellulosome is a multi-modular protein composed starting from the N-terminus of a carbohydrate-binding module (CBM) of family 4, an immunoglobulin(Ig)-like module, a catalytic module of family 9 glycoside hydrolases (GH9), X1(1) and X1(2) modules, a CBM of family 3 and a dockerin module. Deletion of the Ig-like module from the Ig-GH9 construct results in complete inactivation of the GH9 module. The crystal structure of the Ig-GH9 module pair reveals the existence of an extensive module interface composed of over 40 amino acid residues of both modules and maintained through a large number of hydrophilic and hydrophobic interactions. To investigate the importance of these interactions between the two modules, we compared the secondary and tertiary structures and thermostabilities of the individual Ig-like and GH9 modules and the Ig-GH9 module pair using both circular dichroism (CD) spectroscopy and differential scanning calorimetry (DSC). Thr230, Asp262 and Asp264 of the Ig-like module are located in the module interface of the Ig-GH9 module pair and are suggested to be important in 'communication' between the modules. These residues were mutated to alanyl residues. The structure, stability and catalytic properties of the native Ig-GH9 and its D264A and T230A/D262A mutants were compared. The results indicate that despite being able to fold relatively independently, the Ig-like and GH9 modules interact and these interactions affect the final fold and stability of each module. Mutations of one or two amino acid residues lead to destabilization and change of the mechanism of thermal unfolding of the polypeptides. The enzymatic properties of native Ig-GH9, D264A and T230A/D262A mutants are similar. The results indicate that inactivation of the GH9 module occurs as a result of multiple structural disturbances finally affecting the topology of the catalytic center. 相似文献
105.
Irina Georgescu 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2010,15(4):795-801
In this paper a possibilistic model of risk aversion based on the lower and upper possibilistic expected values of a fuzzy
number is studied. Three notions of possibilistic risk premium are defined for which calculation formulae in terms of Arrow–Pratt
index and a possibilistic variance are established. A possibilistic version of Pratt theorem is proved. 相似文献
106.
Valentina E. Smirnova Iosif V. Gofman Vladimir E. Yudin Irina P. Dobrovolskaya Alexander N. Shumakov Andrey L. Didenko Valentine M. Svetlichnyi Ellen Wachtel Rinat Shechter Hannah Harel Gad Marom 《Polymer Engineering and Science》2009,49(2):217-222
The solid state crystallization in drawn thermoplastic polyimide films is studied as a function of draw ratio (DR) under the effect of vapor grown carbon fiber nanoinclusions. The nucleating effect of the nanoinclusions coupled with the orientation effect of drawing generates a unique orientated layered lamellar structure, characteristic of smectic‐like mesophase. The degree of draw induced orientated crystallization increases with the content of nanoinclusions and with the DR, and is reflected in the mechanical behavior of the film. Generally, the Young's modulus and the yield point of the drawn crystalline films in the drawing direction are significantly higher compared with the noncrystalline counterparts. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers 相似文献
107.
Andrei E Filonov Irina F Puntus Alexander V Karpov Irina A Kosheleva Konstantin I Kashparov Anatoly V Slepenkin Alexander M Boronin 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(6):562-569
The efficiency of naphthalene degradation by Pseudomonas putida G7 in soil was assessed using a mathematical model. The number of microorganisms and the concentration of naphthalene in soil samples were monitored. The feasibility of a spectrofluorometric method for naphthalene assay in soil samples was compared with high pressure liquid chromatography. A proposed mathematical model described the growth of the naphthalene‐degrading strains and the consumption of substrates (naphthalene, naphthalene degradation intermediates and soil organic substances) in soil. To describe the growth kinetics of microorganisms having high affinity to substrates with low solubility, two differential equations with substrate exponent 2/3 were proposed. These equations were used to describe utilization of soil organic matter. The model parameters characterize the growth rates for different substrates and respective yield coefficients, specific bacterial death and adaptation rates, and also the rates of PAHs degradation and evaporation. These characteristics can be used in choosing the bacterial strains for biopreparations and efficient clean‐up biotechnology of polluted soils. Copyright © 2004 Society of Chemical Industry 相似文献
108.
Electrochemical and thermal properties of graphite electrodes with imidazolium- and piperidinium-based ionic liquids 总被引:1,自引:0,他引:1
Irina A. Profatilova Nam-Soon Choi Sae Weon Roh Sung Soo Kim 《Journal of power sources》2009,192(2):636-643
The electrochemical and thermal properties of graphite electrodes with electrolytes containing 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMITFSI) and N-methyl,N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (MPPpTFSI) ionic liquids are investigated. The ionic liquids undergo extensive reductive decomposition on a graphite electrode during the first charge. The effect of a fluoroethylene carbonate (FEC) additive on the reductive decomposition of the ionic liquids is examined by electrochemical, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. Thermal reactions between a lithiated graphite electrode and an ionic liquid-containing electrolyte are investigated with differential scanning calorimetry (DSC). The introduction of an ionic liquid can effectively reduce the exothermic heat evolution from the thermal reactions between a lithiated graphite electrode and an electrolyte. 相似文献
109.
Elena N Konyushenko Jaroslav Stejskal Ivana ednkov Miroslava Trchov Irina Sapurina Miroslav Cieslar Jan Proke 《Polymer International》2006,55(1):31-39
The courses of aniline oxidation with ammonium peroxydisulfate in aqueous solutions of strong (sulfuric) and in weak (acetic) acids, followed by temperature and acidity changes, are different. In solutions of sulfuric acid, granular polyaniline (PANI) was produced; in solutions of acetic acid, PANI nanotubes were obtained. The external diameter of the nanotubes was 100–300 nm, the internal cavity 20–100 nm, and the length extended to several micrometres. The morphology of PANI, granular or tubular, depends on the acidity conditions during the reaction rather than on the chemical nature of the acid. PANI nanotubes were also produced when aniline was oxidized in the absence of any acid. The bulk conductivity of PANI prepared in solutions of acetic acid was 0.08–0.27 S cm?1, depending on the acid concentration. Protonated PANI prepared in sulfuric and acetic acids were deprotonated with ammonium hydroxide to obtain PANI bases and the ammonium salt of the protonating acid. FTIR spectroscopy showed the differences in the molecular structure of the PANI bases. Irrespective of whether the polymerization was performed in solutions of sulfuric or acetic acid, PANI had hydrogen sulfate counter‐ions only. The PANI morphology is thus not controlled by the nature of counter‐ions. The acidity of the reaction medium determines the protonation of monomer, oligomer and polymer species. The chemistry of aniline oxidation is likely to be affected especially by the protonation of an intermediate in the pernigraniline form. It is proposed that, in the course of aniline oxidation, pH‐dependent self‐assembly of aniline oligomers predetermines the final PANI morphology. Copyright © 2005 Society of Chemical Industry 相似文献
110.
Vitaly V. Kushnirov Michael D. Ter-Avanesyan Svetlana A. Didichenko Vladimir N. Smirnov Yuri O. Chernoff Irina L. Derkach Olga N. Novikova Sergey G. Inge-Vechtomov Michael A. Neistat Ilya I. Tolstorukov 《Yeast (Chichester, England)》1990,6(6):461-472
SUP2(SUP35) is an omnipotent suppressor gene, coding for an EF-1α-like protein factor, intimately involved in the control of translational accuracy in yeast Saccharomyces cerevisiae. In the present study a SUP2 gene analogue from yeast Pichia pinus was isolated by complementation of the temperature-sensitive sup2 mutation of S. cerevisiae. The nucleotide sequence of the SUP2 gene of P. pinus codes for a protein of 82·4 kDa, exceeding the Sup2 protein of S. cerevisiae by 6 kDa. Like the SUP2 gene product of S. cerevisiae, the Sup2 protein of P. pinus represents a fusion of a unique N-terminal part of a region homologous to EF-1α. The comparison of amino acid sequences of the Sup2 proteins reveals high conservations (76%) of the C-terminal region and low conservation (36%) of the N-terminal part where, in addition, the homologous correspondence is ambiguous. Proteins related to the Sup2 of S. cerevisiae where found in P. pinus and some other yeast species by the immunoblotting technique. The relation between the evolutionary conservation of different regions of the Sup2 protein and their functional significance is discussed. 相似文献