频率捷变脉冲雷达用快速捕获锁相环路

本文叙述锁相环在变容管控制的脉冲式微波固态源同步方面的用途。它适用于必须反复建立锁定的雷达系统和某些形式的数字通信系统。特别重要的是锁定的速度,因而把主要注意力放在设计群延迟低的环路放大器上,为的是依靠一阶环特性来获得最大的锁定范围。文章介绍了一个中心频率为3GHz,相对可调带宽大于10%的信号源的锁定特性,并且表明,锁定时间在20ns左右是可以达到的。另外还证明,甚至极低电平的泄漏信号也可能影响环路的锁定性能,因为在脉冲上升阶段泄漏信号可能牵动信号源的相位,其结果可能利于锁定,也可能妨碍锁定。     

工贸结合是发展对外贸易的重要途径

在我国对外贸易体制改革中,出现了各种工贸结合的组织形式。目前,主要的形式是:“四联合、两公开”、工贸联合企业、专业系统工贸合一公司、工商外贸合一的专业公司等。这些组织形式对外贸的发展在不同程度上都起了推动作用:较快地增加了出口货源,特别是适销对路货源;提高产品质量、改进包装装潢、降低生产成本;打开一些新商品的销路、巩固市场;有利于引进先进技术,发展生产,扩大贸易;促进进口、带动出口。为了促进工贸结合健康地向前发展,目前要认真总结经验,搞好出口商品长期规划。稳定货源供应,提高劳动生产率。降低生产成本,搞好工贸关系。在搞活外贸的同时,加强协调管理,坚持统一对外,保证我国对外贸易顺利地向前发展。     

Continental Airlines and China Southern Airlines Announce Strategic Partnership

Frequent flyer reciprocity to start in Septem- ber;coclesharing to start in November. Continental Airlines and China Southern Airlines.the largest airline in the People's Repub- lic of China.announced on June 18.2007 that they have entered into a strategic partnership for     

Fashion Week,More than Fashion

From August 31 to September 2,the splen- did Beijing Industrial Distinguished Brand Expo 2007 was held in Beijing Exhibition Center.The hosts of this well-known Expo were Beijing Municipal Bureau of Industrial Development,Beijing Bureau of Quality and Technology Supervision,Beijing Branch of the China Council for the Promotion of International Trade.The strong organizing team has made this grand event a great hit to public.     

China and Portugal Strengthen Comprehensive Strategic Partnership

Wan stressed that Chinese enterprises attach great importance to Portugal＇s unique geographic advantages, and those of Portuguese- speaking countries and areas as well. He looks forward to further cooperation with Portuguese industrial and commercial society.     

发扬中俄经济的互补性开创两国贸易的新领域

21世纪伊始，中国和俄罗斯的经贸关系得到了快速的发展。但其中也存在着一系列的实际问题。例如，两国贸易额增长幅度不大，相互投资额也不大，大多数规模较大的技术经济类项目不能付诸实施以及双边贸易结构过于单一等。     

Further Promote and Expand sino-African Trade Cooperation——Interview with CCPIT Chairman Wan Jifei

As an important part of the 2^nd Forum of Sino-African Cooperation, the 2^nd Conference of Chinese and African Entrepreneurs, jointly organized by CCPIT （China Council for the Promotion of International Trade） and the Ministry of Commerce was held from November 4 to 5 in Beijing. Premier Wen Jiabao, 27 African presidents and 6 African government leaders attended the conference. Over 1800 Chinese and African representatives from various industries participated in the conference.     

围产期奶牛的生理变化及其与代谢紊乱的关系

奶牛大多数代谢疾病如产乳热、酮病、胎衣不下、真胃移胃等都发生在产后两周,这其中许多代谢病在分娩后两周不表现临床症状,但却会对泌乳早期牛带来很大危害.除了代谢病外,绝大多数传染性疾病,特别是乳腺炎,在分娩后头两周会产生临床症状.在围产期,为了预防疾病,必须保证三项生理功能的正常发挥(1)调整瘤胃适应产后高能量日粮;(2)维持正常的血钙水平;(3)激发免疫系统,保持强大的免疫功能.这三个功能中任何一个受到抑制都会大大增加代谢病与传染病的发生.本文阐述在奶牛围产期,与这三个因素有关疾病的发病机理.     

Enhancing the IPR System and Building An Innovation Society——Interview with Tian Lipu,Commissioner of the State Intellectual Property Office

Intellectual property rights（IPR）, a key issue in China＇s process of internationalization, has attracted extensive attention, both abroad and at home and has been more and more frequently discussed by the Chinese people, especially since the admittance of China into the WTO in 2001.     

A Future with Hope：China Agriculture Outlook 2007

China's macro economy has remained in a good and stable condition overall,experiencing an annual GDP growth of over 10% for several consecutive years.Under this basic condition, the main focus of the Outlook was China's current grain and oil supply,and the demand market with its probable future prices.