全文获取类型
收费全文 | 616篇 |
免费 | 35篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 1篇 |
综合类 | 2篇 |
化学工业 | 243篇 |
金属工艺 | 9篇 |
机械仪表 | 8篇 |
建筑科学 | 15篇 |
矿业工程 | 4篇 |
能源动力 | 25篇 |
轻工业 | 59篇 |
水利工程 | 5篇 |
石油天然气 | 13篇 |
无线电 | 24篇 |
一般工业技术 | 163篇 |
冶金工业 | 21篇 |
原子能技术 | 1篇 |
自动化技术 | 64篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 38篇 |
2021年 | 70篇 |
2020年 | 13篇 |
2019年 | 19篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 40篇 |
2015年 | 18篇 |
2014年 | 37篇 |
2013年 | 52篇 |
2012年 | 43篇 |
2011年 | 45篇 |
2010年 | 24篇 |
2009年 | 31篇 |
2008年 | 31篇 |
2007年 | 23篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有657条查询结果,搜索用时 203 毫秒
81.
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
82.
油气藏铼-锇同位素定年的进展与挑战 总被引:1,自引:0,他引:1
铼(Re)、锇(Os)元素具有对氧化还原的敏感性和亲有机质特性,富集于烃源岩、油砂、原油、沥青等油气藏相关地质样品中,并被用于油气藏同位素定年。该方法既可通过Re-Os等时线直接获取油气成藏过程的绝对地质年龄,又可利用Os同位素初始值开展油源对比。分析近十余年来油气藏Re-Os同位素年代学研究的进展与不足,指出为推动该定年技术的发展及其在油气勘探实践中的应用,学术界和工业界应密切合作共同探索Re-Os同位素在油气系统中的分馏机理,全面评价硫酸盐热化学还原反应(TSR)、热解事件等后期地质过程对Re-Os同位素体系的潜在影响;综合运用无机和有机地球化学方法,建立判别油气来源的有效工具,以帮助合理选择满足同源特征的Re-Os同位素定年对象。这些问题的解决将有助于尽快建立油气藏Re-Os同位素定年的实用技术方案,并为业内的终端用户提供完整的使用指南。 相似文献
83.
Ivana Mašić Ilija Ilić Rok Dreu Svetlana Ibrić Jelena Parojčić Stanko Srčič 《Drug development and industrial pharmacy》2014,40(1):23-32
Objective: The aim of this study was to investigate the influence of process parameters, binder content and binder addition method on characteristics of the granules obtained by melt granulation (MG) in fluidized bed.Methods: Spray-on experiments were performed according to 23 full factorial design. The effect of binder content, molten binder feed rate, and spray air pressure on granule size and size distribution, granule shape, ?owability and drug release rate was investigated. In the in situ experiments, the influence of binder particle size and binder content was evaluated. Solid-state characterization was performed by means of differential scanning calorimetry, X-ray powder diffraction and Fourier transform infrared spectroscopy.Results: Size of the granules obtained by spray-on procedure was significantly influenced by binder content and spray air pressure, while the width of particle size distribution was mainly affected by binder feed rate. Spray air pressure showed the most significant influence on granule shape. It was shown that smooth and spherical particles with good flow properties may be obtained by both procedures, spray-on and in situ MG. The results obtained indicated the influence of agglomeration mechanism on granule sphericity, with higher degree of granule sphericity observed when immersion and layering was the dominant mechanism. Paracetamol release from granulates was very rapid, but after compression of the granules into tablets, drug release was considerably slower. Solid-state analysis confirmed that the physical form of the granulate components remained unaffected after the MG process.Conclusion: The results presented indicate that MG in fluidized bed could be a good alternative to conventional granulation techniques. 相似文献
84.
Aarthi Sundar Pouyan Farzinpour Kyle D. Gilroy Teng Tan Robert A. Hughes Svetlana Neretina 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(16):3379-3388
Pairs of immiscible elements with deep eutectics are used to synthesize periodic arrays of heterodimers and hollowed metal nanocrescents. In the devised route, substrate‐immobilized Au or Ag nanostructures act as heterogeneous nucleation sites for Ge adatoms. At elevated temperatures the adatoms collect in sufficient quantities to transform each site into a AuGe liquid alloy which, upon cooling, phase separates into elemental components sharing a common interface. The so‐formed Au‐Ge and Ag‐Ge heterodimers exhibit a complex morphology characterized by a noble metal nanocrescent which partially encapsulates one end of the Ge domain. Through the use of a selective etch the Ge component is removed, leaving behind a periodic array of hollow noble metal nanocrescents on the surface of the substrate. Optical characterization of both the heterodimers and nanocrescents indicates that the presence of Ge gives rise to a relative blue‐shift in the localized surface plasmon peak, a result that is in stark contrast to the red‐shifts typically observed when plasmonic nanostructures are in contact with a dielectric medium. Simulations are used to both rationalize the observed shift and show the potential for deriving unexpected behaviors when semishell‐like noble metal structures are in contact with high permittivity dielectric mediums. 相似文献
85.
Sitalo EI Raevski IP Lutokhin AG Blazhevich AV Kubrin SP Raevskaya SI Zakharov YN Malitskaya MA Titov VV Zakharchenko IN 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(9):1914-1919
Dielectric, X-ray, and piezoelectric studies of highly-resistive Li-doped (1-x)PbFe(1/2)Nb(1/2)O(3)-(x)PbTiO(3) (PFN-xPT) ceramics from the 0 ≤ x ≤ 0.2 range fabricated by solid-state synthesis and usual sintering have been carried out. Distinct anomalies of dielectric and piezoelectric parameters, corresponding to the transition between rhombohedral (monoclinic) and tetragonal ferroelectric phases, have been observed in pure PFN and PFN-xPT compositions with PbTiO(3) content up to 8 mol.%. The x,T-phase diagram of the PFN-xPT solid solution system has been constructed using these data. 相似文献
86.
Expression and effect of resistin on bovine and rat granulosa cell steroidogenesis and proliferation
Maillard V Froment P Ramé C Uzbekova S Elis S Dupont J 《Reproduction (Cambridge, England)》2011,141(4):467-479
Resistin, initially identified in adipose tissue and macrophages, was implicated in insulin resistance. Recently, its mRNA was found in hypothalamo-pituitary axis and rat testis, leading us to hypothesize that resistin may be expressed in ovary. In this study, we determined in rats and cows 1) the characterization of resistin in ovary by RT-PCR, immunoblotting, and immunohistochemistry and 2) the effects of recombinant resistin (10, 100, 333, and 667 ng/ml) ± IGF1 (76 ng/ml) on steroidogenesis, proliferation, and signaling pathways of granulosa cells (GC) measured by enzyme immunoassay, [(3)H]thymidine incorporation, and immunoblotting respectively. We observed that resistin mRNA and protein were present in several bovine and rat ovarian cells. Nevertheless, only bovine GC abundantly expressed resistin mRNA and protein. Resistin treatment decreased basal but not IGF1-induced progesterone (P<0.05; whatever the dose) and estradiol (P<0.005; for 10 and 333 ng/ml) production by bovine GC. In rats, resistin (10 ng/ml) increased basal and IGF1-induced progesterone secretion (P<0.0001), without effect on estradiol release. We found no effect of resistin on rat GC proliferation. Conversely, in cows, resistin increased basal proliferation (P<0.0001; for 100-667 ng/ml) and decreased IGF1-induced proliferation of GC (P<0.0001; for 10-333 ng/ml) associated with a decrease in cyclin D2 protein level (P<0.0001). Finally, resistin stimulated AKT and p38-MAPK phosphorylation in both species, ERK1/2-MAPK phosphorylation in rats and had the opposite effect on the AMPK pathway (P<0.05). In conclusion, our results show that resistin is expressed in rat and bovine ovaries. Furthermore, it can modulate GC functions in basal state or in response to IGF1 in vitro. 相似文献
87.
In countries with unstable conditions, negotiations regarding construction work takes place under conditions of great uncertainty with both sides, the purchaser and the investor, trying to minimize the difficulties. This paper gives an insight of how matters relating to costing are looked at by professionals when faced with such conditions. 相似文献
88.
Garegin R. Karagedov Svetlana S. Shatskaya Nikolai Z. Lyakhov 《Journal of Materials Science》2007,42(18):7964-7971
Reasons for a phase transition in zirconia subjected to intensive mechanical treatment in planetary mill have been considered.
If steel balls and vials are used for milling the comminution is accompanied by oxidation of wear metal particles and successive
mechanochemical reaction with ZrO2. Aluminum has been shown to behave similarly and, being deliberately added to zirconia powder, to form solid solutions. Foreign
metal cations introduced into the lattice stabilize a modification with higher crystal symmetry thus increasing the threshold
size above which the monoclinic modification is stable. An increase of surface energy contribution to the Gibbs’ energy of
zirconia plays an important role in phase transformation at the initial stages of mechanical treatment, while henceforth thermodynamic
stability is more and more determined by the stabilizing effect of the impurity cations. Under the conditions that rule out
contamination of ZrO2 with wear material or other metal additives, dynamic equilibrium sets in between the direct transition to the tetragonal
phase and the reverse transition to the monoclinic form. 相似文献
89.
The three-dimensional (3D) model of a feedforward neural network(NN) based on so called N-hypercube topology isproposed. The N-hypercube is different from theclassical hypercube used in communication theory, and in Booleanalgebra. This new structure has been created based on a novelalgorithm for embedding a binary decision tree and binary decisiondiagram into a N-hypercube. It is shown thatN-hypercube topology is a reasonable solution toimplement NN of threshold gates, in particular, on thesingle-electron devices. The 3D design methodology of feedforwardNN is oriented to technology mapping to nanodevices. Results ofextensive experimental study of feedforward networks consistingof over 3500 N-hypercubes are presented. 相似文献
90.
Jaroslav Stejskal Mária OmastováSvetlana Fedorova Jan ProkešMiroslava Trchová 《Polymer》2003,44(5):1353-1358
Polyaniline and polypyrrole have been prepared by chemical oxidative polymerization of the corresponding monomers in an aqueous medium containing an anionic surfactant—sodium bis(2-ethylhexyl) sulfosuccinate, dodecylbenzenesulfonic acid and its sodium salt, and sodium dodecyl sulfate. Determination of the yield, elemental composition and density proved, and FTIR spectroscopy confirmed, that the anionic surfactants become incorporated in the conducting polymers. The polymerizations in the presence of a cationic surfactant, tetradecyltrimethylammonium bromide, were carried out for comparison. While the conductivity of polypyrrole became enhanced after the introduction of an anionic surfactant, the changes in the conductivity of polyaniline were marginal. The conductivity changes in both polymers during thermal ageing were measured at 175 °C. The electrical stability of polyaniline was better than that of polypyrrole. The presence of a surfactant improved the stability of conductivity of polypyrrole but reduced the electrical stability of polyaniline. 相似文献