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   609篇
  免费   17篇
电工技术   104篇
化学工业   159篇
金属工艺   8篇
机械仪表   15篇
建筑科学   8篇
矿业工程   2篇
能源动力   25篇
轻工业   73篇
石油天然气   2篇
无线电   37篇
一般工业技术   124篇
冶金工业   12篇
原子能技术   17篇
自动化技术   40篇
  2023年   4篇
  2022年   2篇
  2021年   16篇
  2020年   6篇
  2019年   9篇
  2018年   9篇
  2017年   2篇
  2016年   12篇
  2015年   19篇
  2014年   12篇
  2013年   50篇
  2012年   26篇
  2011年   39篇
  2010年   31篇
  2009年   33篇
  2008年   45篇
  2007年   40篇
  2006年   32篇
  2005年   21篇
  2004年   19篇
  2003年   28篇
  2002年   14篇
  2001年   5篇
  2000年   9篇
  1999年   12篇
  1998年   13篇
  1997年   14篇
  1996年   10篇
  1995年   9篇
  1994年   6篇
  1993年   10篇
  1992年   5篇
  1991年   2篇
  1990年   5篇
  1989年   5篇
  1988年   2篇
  1987年   3篇
  1986年   6篇
  1985年   5篇
  1984年   4篇
  1983年   7篇
  1981年   6篇
  1980年   2篇
  1979年   1篇
  1978年   5篇
  1977年   3篇
  1976年   5篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有626条查询结果,搜索用时 31 毫秒
51.
Phosphorylation is a useful method for improving the functional properties of food proteins. In this article, various methods of phosphorylation are reviewed. Dry-heating phosphorylation, a method developed recently, is also introduced. Some characteristics of phosphate groups are involved, and the effects of phosphorylation on the structural changes, the functional properties, and the physiological functions in vitro of food proteins, are discussed. The types of phosphate linkages and the phosphopeptides from phosphorylated proteins are identified. The molten (partially unfolded) conformations of food proteins formed by phosphorylation are discussed. The phosphorylation of food proteins improved a number of functional properties, including heat stability, emulsifying properties, foaming properties, gelling properties, water absorption capacity, oil absorption capacity, and calcium phosphate-solubilizing ability. In vitro physiological function studies of protein (α-lactoalbumin) indicated that the digestibility (ovalbumin) was improved and the inflammatory response (α-lactoalbumin) was suppressed by phosphorylation. Experiments with animals are necessary to evaluate the toxicity and physiological functions of phosphorylated proteins.  相似文献   
52.
高档的通信设备曾一度只能在办公环境中才能使用,然而现在这种情况已经改变,家庭中已经普遍具备了互连能力,许多家用电子设备现在通过Ipv6和其他技术已经具备了上网能力。随着宽带通信应用的增加,调制解调器、各种DSL接入复用器以及其他类似设备的安装已经遍及办公室和家庭,消费者可以方便获得价廉的通信设备。对于设备制造商来说,这些装置必须满足安全标准,如IEC60950(InternationalElectrotechnicalCommission第三版),它要求在与数据通信线连接的设备上实现电话网络高压电路的隔离。一般情况下,人们采用传统的电磁通信继电器来开关内…  相似文献   
53.
Changes in water intake after intraperitoneal injection of a nitric oxide synthase (NOS) inhibitor was studied in the rat. Administration of NW-nitro-L arginine methyl ester (L-NAME) at a dose of 50 mg/kg attenuated osmotic thirst induced by intraperitoneal injection of hypertonic saline, but did not affect spontaneous intake of water and thirst induced by subcutaneous injection of angiotension II. Pretreatment with L-arginine significantly attenuated the inhibition of osmotic thirst evoked with subsequent L-NAME. Administration of NW-nitro-D-arginine methyl ester (D-NAME) altered neither the spontaneous nor the osmotic drinking behavior. These findings suggest that NO may affect the osmotically induced drinking.  相似文献   
54.
Any solution for an inverse heat conduction problem makes the estimation of surface temperature and surface heat flux worsen in the case where these values behave like a triangular shape change with time. In order to compensate for this defect, Monde and colleagues, who succeeded in obtaining analytical inverse solutions using the Laplace transform technique, introduce a new idea where these changes over the entire measurement time can be split into several parts depending on the behavior. Therefore, an approximate equation to trace the measured temperature change can be derived, resulting in good estimation of surface temperature and surface heat flux even in the case of the triangular shape change and sharp change. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(7): 630–638, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10117  相似文献   
55.
曹长娥 《焊管》1997,20(6):57-61
试验了彩色聚乙烯涂覆钢管的耐腐蚀性和耐气候性,由于聚乙烯涂层隔绝水的作用,聚乙烯涂覆钢管具有优良的耐腐蚀性能,电阻绝缘值和优良的机械性能。建立了一个新的方式去研究分析聚乙烯抗老化剂消耗和在聚乙烯中的扩散。用有效测定的方法定量地预测彩色聚乙烯涂覆层的寿命,应用这些分析结果,不仅可使新的有色聚乙烯涂覆钢管在恶劣腐蚀环境介质情况下具有高的耐腐蚀性,而且有长的耐气候性。  相似文献   
56.
In vitro mammalian cytogenetic tests detect chromosomal aberrations and are used for testing the genotoxicity of compounds. This study aimed to identify a supportive genomic biomarker could minimize the risk of misjudgments and aid appropriate decision making in genotoxicity testing. Human lymphoblastoid TK6 cells were treated with each of six DNA damage-inducing genotoxins (clastogens) or two genotoxins that do not cause DNA damage. Cells were exposed to each compound for 4 h, and gene expression was comprehensively examined using Affymetrix U133A microarrays. Toxicogenomic analysis revealed characteristic alterations in the expression of genes included in cyclin-dependent kinase inhibitor 1A (CDKN1A/p21)-centered network. The majority of genes included in this network were upregulated on treatment with DNA damage-inducing clastogens. The network, however, also included kinesin family member 20A (KIF20A) downregulated by treatment with all the DNA damage-inducing clastogens. Downregulation of KIF20A expression was successfully confirmed using additional DNA damage-inducing clastogens. Our analysis also demonstrated that nucleic acid constituents falsely downregulated the expression of KIF20A, possibly via p16 activation, independently of the CDKN1A signaling pathway. Our results indicate the potential of KIF20A as a supportive biomarker for clastogenicity judgment and possible mechanisms involved in KIF20A downregulation in DNA damage and non-DNA damage signaling networks.  相似文献   
57.
A Chen-type correlation for flow boiling heat transfer of R-134a in horizontal tubes was modified taking into account the effect of tube diameter. The effect of tube diameter on flow boiling heat transfer coefficient was characterized by the Weber number in gas phase. Results showed that this correlation could be applied to a wide range of tube diameters (0.5–11-mm-ID). In addition, the dryout point and the heat transfer characteristics after the dryout point were also investigated based on the annular flow model. The proposed experimental expressions to predict both the dryout quality and the post-dryout heat transfer coefficient could also be applied to a wide range of tube diameter (0.5–11-mm-ID).  相似文献   
58.
An analytical method using Laplace transformation has been developed for one‐dimensional heat conduction. This method succeeded in explicitly deriving the analytical solution by which the surface temperature for the first kind of boundary condition can be well predicted. The analytical solutions for the surface temperature and heat flux are applied to the second and third of the boundary conditions. These solutions are also found to estimate the corresponding surface conditions with a high degree of accuracy when the surface conditions smoothly change. On the other hand, when these conditions erratically change such as the first derivative of temperature with time, the accuracy of the estimation becomes slightly less than that for a smooth condition. This trend in the estimation is similar irrespective of any kind of boundary condition. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(1): 29–41, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10069  相似文献   
59.
Crystallization of 4He in aerogels of 90 and 96% porosities shows a dynamical phase transition at around 600 mK due to the competition between thermal fluctuation and disorder: crystals grow via creep at high temperatures and via avalanche at low temperatures. In a very high porosity 99.5% aerogel, however, the transition had not been observed in our previous publication (Nomura et al. in Phys. Rev. Lett. 101:175703, 2008). We improved the spatial resolution of the video image and found that the 99.5% aerogel did have the transition at around 200 mK, which is much lower than those of the lower porosities. The avalanche size is significantly smaller in the 99.5% aerogel. The reduction in the transition temperature and avalanche size may be the consequence of weaker disorder for the crystallization in the very high porosity aerogel.  相似文献   
60.
In general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage-source inverters. Rectifiers of this type, however, cause many problems such as poor power factor and harmonics. Recently, voltage-source PWM rectifier-inverters have been studied to provide the following advantages: (1) harmonic-free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. However, it is difficult for a conventional voltage-source PWM rectifier-inverter to regulate the capacitor voltage on transient states because it has only a voltage feedback loop. This paper describes a voltage-source PWM rectifier-inverter with feedforward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feedforward control of instantaneous power contributes greatly to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed, and some interesting experimental results of a laboratory model are shown.  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