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   5639篇
  免费   460篇
  国内免费   110篇
电工技术   244篇
综合类   202篇
化学工业   966篇
金属工艺   194篇
机械仪表   191篇
建筑科学   348篇
矿业工程   49篇
能源动力   307篇
轻工业   460篇
水利工程   95篇
石油天然气   178篇
武器工业   5篇
无线电   645篇
一般工业技术   818篇
冶金工业   410篇
原子能技术   21篇
自动化技术   1076篇
  2024年   11篇
  2023年   89篇
  2022年   152篇
  2021年   215篇
  2020年   170篇
  2019年   170篇
  2018年   209篇
  2017年   196篇
  2016年   237篇
  2015年   213篇
  2014年   231篇
  2013年   434篇
  2012年   331篇
  2011年   421篇
  2010年   341篇
  2009年   340篇
  2008年   283篇
  2007年   242篇
  2006年   237篇
  2005年   192篇
  2004年   133篇
  2003年   147篇
  2002年   195篇
  2001年   146篇
  2000年   105篇
  1999年   63篇
  1998年   111篇
  1997年   78篇
  1996年   62篇
  1995年   62篇
  1994年   53篇
  1993年   44篇
  1992年   25篇
  1991年   8篇
  1990年   19篇
  1989年   10篇
  1988年   15篇
  1987年   15篇
  1986年   13篇
  1985年   11篇
  1984年   25篇
  1983年   14篇
  1982年   18篇
  1981年   15篇
  1980年   10篇
  1979年   13篇
  1978年   14篇
  1977年   12篇
  1976年   20篇
  1975年   9篇
排序方式: 共有6209条查询结果,搜索用时 46 毫秒
51.
Bilirubin toxicity to the central nervous system (CNS) is responsible for severe and permanent neurologic damage, resulting in hearing loss, cognitive, and movement impairment. Timely and effective management of severe neonatal hyperbilirubinemia by phototherapy or exchange transfusion is crucial for avoiding permanent neurological consequences, but these therapies are not always possible, particularly in low-income countries. To explore alternative options, we investigated a pharmaceutical approach focused on protecting the CNS from pigment toxicity, independently from serum bilirubin level. To this goal, we tested the ability of curcumin, a nutraceutical already used with relevant results in animal models as well as in clinics in other diseases, in the Gunn rat, the spontaneous model of neonatal hyperbilirubinemia. Curcumin treatment fully abolished the landmark cerebellar hypoplasia of Gunn rat, restoring the histological features, and reverting the behavioral abnormalities present in the hyperbilirubinemic rat. The protection was mediated by a multi-target action on the main bilirubin-induced pathological mechanism ongoing CNS damage (inflammation, redox imbalance, and glutamate neurotoxicity). If confirmed by independent studies, the result suggests the potential of curcumin as an alternative/complementary approach to bilirubin-induced brain damage in the clinical scenario.  相似文献   
52.
一种针对信息网格RBAC模型私有权限问题的有效解决方案*   总被引:3,自引:0,他引:3  
针对信息网格RBAC(Role-Based Access Control)模型中由于继承关系产生的子角色不能拥有私有权限的问题进行了研究,并分析了当前提出的使用私有角色和深度指示符这两种解决方法.通过分析得出这两种方法分别存在角色膨胀和组合爆炸的缺点.在此基础上,提出了一种带有权限传播深度的新解决方法,即角色中的每个权限分别具有公有和私有属性以及权限传播深度,同时提供了一个算法求解每个角色的权限集.  相似文献   
53.
Faltakh  Hana  Bourguiga  Ramzi  Ahmed  Amira Ben 《SILICON》2021,13(12):4201-4213
Silicon - This paper presents recent progress in computational modeling on blend morphology of silicon nanowires (SiNWs) dispersed in a conjugated polymer poly(3-hexylthiophene) P3HT hybrid solar...  相似文献   
54.
Utilizing CO2 in an electro-chemical process and synthesizing value-added chemicals are amongst the few viable and scalable pathways in carbon capture and utilization technologies.CO2 electro-reduction is also counted as one of the main options entailing less fossil fuel consumption and as a future electrical energy storage strategy.The current study aims at developing a new electrochemical platform to produce low-carbon e-biofuel through multifunctional electrosynthesis and integrated co-valorisation of biomass feedstocks with captured CO2.In this approach,CO2 is reduced at the cathode to produce drop-in fuels(e.g.,methanol)while value-added chemicals(e.g.,selective oxidation of alcohols,aldehydes,carboxylic acids and amines/amides)are produced at the anode.In this work,a numerical model of a continuous-flow design considering various anodic and cathodic reactions was built to determine the most techno-economically feasible configurations from the aspects of energy efficiency,environment impact and economical values.The reactor design was then optimized via parametric analysis.  相似文献   
55.
Journal of Inorganic and Organometallic Polymers and Materials - Nanoporous carbon matrix was prepared by the sol–gel process from pyrogallol-formaldehyde (PF) mixtures in water using picric...  相似文献   
56.
印刷线路板电镀废水综合治理   总被引:6,自引:1,他引:6  
简述线路板电镀废水中氰、铜氨、油墨废水治理方法和混合废水综合治理工艺流程及原理。  相似文献   
57.
The molecular orientation at the outer surface of injection–stretch–blow‐molded bottles made from poly(ethylene terephthalate) was characterized and quantified by means of front‐surface reflection infrared spectroscopy based on a method developed previously. Results were obtained for two different bottle shapes (cylindrical and rectangular) molded at different injection mold temperatures (16, 38, and 60°C). For the cylindrical bottles, the preferred molecular chain orientation was found to be in the axial direction, with the Hermans orientation function near 0.3 for all three mold temperatures. For the less symmetrical rectangular bottles, a significant difference was observed between the large and small faces. For the large face, the orientation was mainly in the hoop direction; the Hermans orientation function was in the range of 0.3–0.5 and was essentially the same at all mold temperatures and positions along the bottle height. For the small face, on the other hand, the preferred orientation changed from the hoop direction near the bottom to the axial direction near the top, and the variation was more pronounced at lower mold temperatures. The utility of the front‐surface reflection technique was clearly demonstrated. It was also applied, with the use of an infrared microscope, to examine the orientation gradient across the wall thickness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1319–1327, 2007  相似文献   
58.
对反应器网络综合问题进行了研究,分析了瞬时选择性对关键组份组成的偏导数与最佳反应器类型之间的关系,给出了确定最优反应器的三条规则。对δS/δC符号不变的反应体系,用这些规则可获得最优反应器网络。对一般的反应体系,假设了五种典型S-CA曲线所对应的反应过程,分别对不同曲线类型给出了确定最优反应器网络的方法。此外,按本文方法所得的最优反应器网络结构是一个CSTR或PFR或由CSTR、PFR组成的串联结构。由dS/dCA的符号及其变化情况决定。给出了两个说明本文方法的例子,结果表明本文方法简单并可获得与文献相同或相似的结果。  相似文献   
59.
High molecular weight polyacetylenes bearing nonlinear chromophoric pendants poly[4-ethynyl-4′-(N,N-diethylamino)azobenzene-co-phenylacetylene]s [poly(EAAB-co-PA)s] were synthesized in moderate yields by [Rh(nbd)Cl]2-Et3N. The azo unit in the copolymers can be effectively controlled by the monomer feed ratio. Whereas the homopolymer of EAAB possessed low solubility, all the copolymers, however, dissolved readily in common organic solvents when the poly(EAAB) molar content was less than 41.7%. The structures and properties of the polymers were characterized and evaluated by UV, NMR, optical limiting, and nonlinear optical analyses. All the copolymers possessed high stereoregularity and thermal stability (≥300 °C). They can attenuate intense laser pulses, with solutions of high concentrations showing better performances. The third-order nonlinear susceptibility of the copolymers was as high as 4.62×10−11 esu, which are two orders of magnitude larger than those of poly(PA), and larger than that of poly(N-carbazoylacetylene), and poly(1-naphthylacetylene).  相似文献   
60.
The objective of this work is to study the transfer of oxygen from gas to liquid phase in an electroflotation cell. The measurements were performed in a laboratory scale cell using insoluble electrodes, titanium coated with ruthenium oxide as anode and stainless steel as cathode. The volumetric mass transfer coefficient K L a, was characterized for clean tap water as liquid phase for different values of current density (J). The global coefficient of mass transfer based on the liquid film, K L , and the specific interfacial area, a, were characterized. A model which relates K L a to current density was established. Different evaluation criteria of oxygen transfer in electroflotation process were determined and compared with other aeration process.  相似文献   
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