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561.
液氮和液氦在低温电子显微镜中都可以作为冷冻剂来保持样品处于含水冷冻状态.本文分析了收集于一台300千伏的日本电子(JEOL)低温电镜和样品处于液氦温度4 K的两组生物大分子单颗粒数据:第一组为噬菌体epsilon 15的数据,成像于Gatan 4 k×4 k电荷耦合器件;第二组是记录在Kodak SO-163底片上的噬菌体P22的数据.对这两组数据的频谱分析显示这些数据的信号分辨率均可达5~6埃.并用实验B因子对这两组数据的质量进行了定量分析.本文结果显示液氦冷冻电镜可用来收集单颗粒生物大分子的高分辨三维结构重构所需的数据. 相似文献
562.
Wenlin Chen Yang Ge Jie Lu Joshua Melo Yee Wah So Romi Juneja Lidong Liu Yu Tian Wang 《International journal of molecular sciences》2022,23(5)
Mutations of GABAAR have reportedly led to epileptic encephalopathy and neurodevelopmental disorders. We have identified a novel de novo T292S missense variant of GABRA1 from a pediatric patient with grievous global developmental delay but without obvious epileptic activity. This mutation coincidentally occurs at the same residue as that of a previously reported GABRA1 variant T292I identified from a pediatric patient with severe epilepsy. The distinct phenotypes of these two patients prompted us to compare the impacts of the two mutants on the receptor function and to search for suitable therapeutics. In this study, we used biochemical techniques and patch-clamp recordings in HEK293 cells overexpressing either wild-type or mutated rat recombinant GABAARs. We found that the α1T292S variant significantly increased GABA-evoked whole-cell currents, shifting the dose–response curve to the left without altering the maximal response. In contrast, the α1T292I variant significantly reduced GABA-evoked currents, shifting the dose–response curve to the right with a severely diminished maximum response. Single-channel recordings further revealed that the α1T292S variant increased, while the α1T292I variant decreased the GABAAR single-channel open time and open probability. Importantly, we found that the T292S mutation-induced increase in GABAAR function could be fully normalized by the negative GABAAR modulator thiocolchicoside, whereas the T292I mutation-induced impairment of GABAAR function was largely rescued with a combination of the GABAAR positive modulators diazepam and verapamil. Our study demonstrated that α1T292 is a critical residue for controlling GABAAR channel gating, and mutations at this residue may produce opposite impacts on the function of the receptors. Thus, the present work highlights the importance of functionally characterizing each individual GABAAR mutation for ensuring precision medicine. 相似文献
563.
Qiwei Wang Marcus Chun‐Wah Yuen Prof. Guo‐Liang Lu Dr. Cheuk‐Lam Ho Dr. Gui‐Jiang Zhou Dr. Oi‐Mei Keung Kim‐Hung Lam Dr. Roberto Gambari Prof. Xiao‐Ming Tao Prof. Raymond Siu‐Ming Wong Dr. See‐Wai Tong Kit‐Wah Chan Fung‐Yi Lau Dr. Filly Cheung Dr. Gregory Yin‐Ming Cheng Prof. Chung‐Hin Chui Dr. Wai‐Yeung Wong Prof. 《ChemMedChem》2010,5(4):559-566
A homologous set of 9,9‐dialkyl‐4,5‐diazafluorene compounds were prepared by alkylation of 4,5‐diazafluorene with the appropriate alkyl bromide and under basic conditions. The structures of these simple organic compounds were confirmed by spectroscopic techniques (FTIR, NMR, and FABMS). Their biological effects toward a panel of human carcinoma cells, including Hep3B hepatocellular carcinoma, MDAMB‐231 breast carcinoma, and SKHep‐1 hepatoma cells, were investigated; a structure–activity correlation was established with respect to the length of the alkyl chain and the fluorene ring structure. The relationship between the mean potency [log(1/IC50)] and alkyl chain length was systematically studied. The results show that compounds with butyl, hexyl, and octyl chains exhibit good growth inhibitory effects toward these three human carcinoma cell lines, and the 9,9‐dihexyl‐4,5‐diazafluorene further exhibits antitumor activity in athymic nude mice Hep3B xenograft models. For the structurally related dialkylfluorenes that lack the diaza functionality, in vitro cytotoxicity was not observed at clinically relevant concentrations. 相似文献
564.
An experimental investigation was presented on the separation of Cu (II), Zn (II), and Cd (II) from a rich sulfate leachate of zinc slag by solvent extraction. The results of orthogonal experiments indicate that LIX 984N is highly selective and very efficient in the extraction of Cu (II), and the analysis of variance indicates that the sequence of parameters according to their influence on the separation efficiency is phase ratio>LIX 984N concentration>pH value>extraction time. The optimal condition for copper extraction is obtained as 25% of LIX 984N concentration, 7 min of extraction time, 3:2 of phase ratio O/A, and pH=1.7. The separation of Zn (II) and Cd (II) was performed after the copper extraction from the raffinate. Comparative analysis of the separation with di-2-ethylhexyl phosphoric acid (D2EHPA), D2EHPA-tributyl-phosophate (TBP) synergistic extracting system, and 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (HEHEHP) was made at pH=2.0. It is demonstrated that the extraction efficiency with D2EHPA is improved after being saponified by sodium hydroxide, and D2EHPA-TBP synergistic extracting, as well as HEHEHP, has a superior selectivity to Zn (II) over Cd (II). 相似文献
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Classification of geothermal resources by exergy 总被引:2,自引:0,他引:2
Geothermal resources have been classified as low, medium and high enthalpy resources according to their reservoir fluid temperatures. There is no general agreement on the arbitrary temperature ranges used. Classification of a geothermal resource by its reservoir fluid temperature can be ambiguous because two independent properties are required to define the thermodynamic state of a fluid. Geothermal resources should be classified to reflect their ability to do thermodynamic work. In this paper, it is proposed that geothermal resources be classified as low, medium and high quality resources with reference to their specific exergy indices (SExI), SExI<0.05, 0.05SExI<0.5 and SExI0.5, respectively. The demarcation limits for these indices are exergies of saturated water and dry saturated steam at 1 bar absolute. These demarcation lines can be plotted on a Mollier diagram to form a classification map of geothermal resources. 相似文献