首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1505篇
  免费   193篇
  国内免费   64篇
电工技术   21篇
技术理论   1篇
综合类   49篇
化学工业   245篇
金属工艺   44篇
机械仪表   97篇
建筑科学   39篇
矿业工程   8篇
能源动力   67篇
轻工业   629篇
水利工程   29篇
石油天然气   53篇
武器工业   3篇
无线电   78篇
一般工业技术   150篇
冶金工业   13篇
原子能技术   4篇
自动化技术   232篇
  2024年   15篇
  2023年   61篇
  2022年   84篇
  2021年   76篇
  2020年   76篇
  2019年   66篇
  2018年   73篇
  2017年   46篇
  2016年   61篇
  2015年   77篇
  2014年   129篇
  2013年   98篇
  2012年   173篇
  2011年   152篇
  2010年   133篇
  2009年   108篇
  2008年   64篇
  2007年   119篇
  2006年   67篇
  2005年   24篇
  2004年   10篇
  2003年   9篇
  2002年   10篇
  2001年   14篇
  2000年   5篇
  1999年   7篇
  1998年   5篇
排序方式: 共有1762条查询结果,搜索用时 15 毫秒
1.
为提高Western Blotting结果的可靠性,以蛋白溶出率和凝胶电泳蛋白条带完整性为指标,比较提取液种类、研磨方式、酶抑制剂种类及其体积分数和提取时间对南美白对虾肝胰腺蛋白提取效果的影响。采用优化后的提取方法获得高质量蛋白样品,并采用Western Blotting法分析无水环境胁迫后南美白对虾肝胰腺组织中细胞凋亡信号通路相关蛋白的表达水平。结果表明:RIPA裂解液作为提取溶剂所得的蛋白溶出率高于水提和磷酸盐缓冲液,电动匀浆和液氮研磨所得蛋白条带更完整,4%蛋白酶磷酸酶混合抑制剂能有效抑制肝胰腺内源酶引起的蛋白降解;采用Western Blotting法分析无水保活期间南美白对虾肝胰腺蛋白,发现低温诱导休眠的同时会引起细胞轻微凋亡,且凋亡水平呈应激时间依赖性增加,环境胁迫解除后有所回调。  相似文献   
2.
《Ceramics International》2022,48(6):8325-8330
In this work, we propose a facile approach to fabricate Ti4+-doped Li3V2(PO4)3/C (abbreviated as C-LVTP) nanofibers using an electrospinning route followed by a high temperature treatment. In this designed nanocomposite, the ultrafine LVTP dots are homogeneously dispersed into one-dimensional carbon nanofibers and the Ti4+ doping does not destroy the crystal structure of monoclinic Li3V2(PO4)3. Compared to the undoped Li3V2(PO4)3/C (abbreviated as C-LVP), the as-fabricated C-LVTP fibers present higher reversible capacity, superior high-rate capability as well as better cyclic property. Especially, the C-LVT7%P cathode delivers not only high capacities of 187.2 and 160.3 mAh g?1 at 0.5 and 10 C respectively, but also stable cyclic property with the reversible capacity of 135.8 mAh g?1 at 20 C following 500-cycle spans. The good battery characteristics of C-LVT7%P can be mainly ascribed to Ti4+ doping, which can increase the electrical conductivity and Li+ diffusion coefficient.  相似文献   
3.
4.
The microstructure of ZrFe2-based alloys were modified by alloying with the Mn, Ti, and V, aiming to obtain proper hydriding/dehydriding plateau features for the high-pressure application. The multi-component ZrFe2-based alloys show a wide tunable range in the plateau pressure via the interaction of Ti, Mn, and V. Further, the V addition plays the best role to improve the hysteresis in absorption-desorption isotherms, while the proper addition amount Ti helps to realize a low plateau slope as well as a high plateau pressure. Among the investigated alloys, Zr1.05Fe1.6Mn0.4 shows a relatively high dehydriding pressure of 20.58 atm at 298 K, while Zr1.05Fe1.7Mn0.2V0.1 with C15 structure shows the lowest hysteresis. Overall, too much of Ti and Mn would promote the transformation of the C15 to C14 structure with large hysteresis and low plateau pressure.  相似文献   
5.
This research is concerned with the problem of 4 degrees of freedom (DOF) ship manoeuvring identification modelling with the full-scale trial data. To avoid the multi-innovation matrix inversion in the conventional multi-innovation least squares (MILS) algorithm, a new transformed multi-innovation least squares (TMILS) algorithm is first developed by virtue of the coupling identification concept. And much effort is made to guarantee the uniformly ultimate convergence. Furthermore, the auto-constructed TMILS scheme is derived for the ship manoeuvring motion identification by combination with a statistic index. Comparing with the existing results, the proposed scheme has the significant computational advantage and is able to estimate the model structure. The illustrative examples demonstrate the effectiveness of the proposed algorithm, especially including the identification application with full-scale trial data.  相似文献   
6.
Saturation pressure is a vital parameter of oil reservoir which can reflect the oilfield characteristics and determine the oilfield development process, and it is determined by experiments in the laboratory in general. However, there was only one well with saturation pressure test in this target reservoir, and it is necessary to determine whether this parameter is right or not.In this work, we present a new method for quickly determining saturation pressure using machine learning algorithms, including random forest regressor (RF), support vector machine (SVM), decision trees (DT), and artificial neural network (ANN or NN). Using these approaches, saturation pressure was obtained by using the initial solution gas-oil ratio (GOR), temperature, API gravity and other reservoir-fluid data available in the oilfields. Compared with the empirical formula for saturation pressure calculation, the calculated result shows that the accuracy given from machine learning is higher than that from other formulas at home and abroad, and has a good match with the lab test. On the basis of the calculated saturation pressure, it can determine whether the reservoir enters into the stage of dissolved gas drive or not, which also provides the basis for maintaining the reservoir pressure by water injection in advance, rational development decision-making and work over measures.This approach above can provide technical guidance for predicting the saturation pressure in the development of different kinds of reservoirs, including the sandstone reservoirs and carbonate reservoirs.  相似文献   
7.
滴定-凝胶法制备球形水凝胶吸附材料具有3D倒漏斗状微观形貌结构,孔径分布宽泛,对水体中重金属、染料等污染物具有快速响应机制,已被广泛用于水处理过程研究。综述了滴制法制备球形水凝胶吸附材料的主要过程机理、水凝胶具有的特殊形貌结构及其在水处理过程中的应用,分析了球形水凝胶吸附材料在水处理应用过程中存在的问题和局限,并指出了其在水处理领域的应用前景及发展方向。  相似文献   
8.
Thermal effects in a H2O and CO2 assisted tubular direct carbon solid oxide fuel cell (DC-SOFC) are numerically investigated. Parametric simulations are further conducted to study the effects of operating potential, the distance between carbon and anode, inlet gas temperature, and anode inlet gas flow rate on the thermal behaviors of the fuel cell. It is found that the fuel cell with H2O as gasification agent performs considerably better than the cell with CO2 as gasification agent in all cases. It is also found that the temperature field of the fuel cell is highly uneven. The breakdown of the heat sources in the fuel cell shows that the H2O assisted DC-SOFC has much higher heat generation and consumption than the CO2 assisted cell. Interestingly, a thermal neutral voltage is observed, at which no heating or cooling of the cell is needed. In addition, the distance between the anode and the carbon layer is required to be as small as possible, which improves the temperature uniformity of the fuel cell. The results of this study demonstrates the importance of thermal effects in DC-SOFCs and form a solid foundation for DC-SOFC thermal management.  相似文献   
9.
The aim of this work was to assess the effect of several melanosis-inhibiting formulations on quality of deepwater pink shrimp (Parapenaeus longirostris) during storage. The formulations tested were as follows: one containing 4-hexylresorcinol (0.1%) in combination with organic acids (citric, ascorbic and acetic) and chelating agents (ethylenediaminetetraacetic acid [EDTA] and di-sodium di-hydrogen pyrophosphate [PPi]); a commercial formula based on sulphites (3%), and another formulation containing a mixture of chitosan (0.3%) and commercial sulphites. Non-treated shrimp were used as control. The 4-hexylresorcinol-based formulation was more effective than 3% of commercial sulphite solutions in preventing melanosis. This treatment prolonged the sensory acceptability of shrimp by up to six days in ice storage. During chilled storage, the treatment with the 4-hexylresorcinol-based formula inhibited the growth of microorganisms by 1.5–2 log cycles as compared to commercial sulphites, especially H2S-producers and pseudomonads. At the end of the experimental period, TVB-N levels were slightly higher in the lot treated with 4-hexylresorcinol (33 mg/100 mg) and reflected greater endogenous enzymatic activity, since the counts of the spoiler microorganisms remained around log 5 cfu/g or even lower. In general, the incorporation of chitosan to sulphites did not improve or produce a marked effect on shrimps during storage. During the sensory analysis, the panellists rated all the lots very similar, although the 4-hexylresorcinol formulation was the only one with a neutral odour at the end of the period. The 4-hexylresorcinol-based formulation induced yellow-green colorations to some extent in the cephalothorax, possibly due to the effect of organic acids and chelants, while the rest of the lots presented greyish/blackish colorations. Therefore, the formulation based on 4-hexylresorcinol may safely substitute traditional sulphites to improve the quality of fresh shrimp and prolong their shelf life during storage.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号