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   9656篇
  免费   1448篇
  国内免费   461篇
电工技术   90篇
技术理论   1篇
综合类   257篇
化学工业   4531篇
金属工艺   295篇
机械仪表   209篇
建筑科学   174篇
矿业工程   55篇
能源动力   86篇
轻工业   926篇
水利工程   141篇
石油天然气   70篇
武器工业   16篇
无线电   852篇
一般工业技术   2395篇
冶金工业   612篇
原子能技术   44篇
自动化技术   811篇
  2024年   65篇
  2023年   311篇
  2022年   706篇
  2021年   899篇
  2020年   498篇
  2019年   548篇
  2018年   499篇
  2017年   474篇
  2016年   514篇
  2015年   573篇
  2014年   661篇
  2013年   981篇
  2012年   617篇
  2011年   597篇
  2010年   504篇
  2009年   478篇
  2008年   380篇
  2007年   415篇
  2006年   358篇
  2005年   321篇
  2004年   259篇
  2003年   206篇
  2002年   183篇
  2001年   105篇
  2000年   72篇
  1999年   66篇
  1998年   33篇
  1997年   41篇
  1996年   25篇
  1995年   21篇
  1994年   13篇
  1993年   14篇
  1992年   18篇
  1991年   8篇
  1990年   9篇
  1989年   8篇
  1988年   7篇
  1987年   6篇
  1986年   12篇
  1985年   4篇
  1984年   6篇
  1983年   4篇
  1982年   4篇
  1981年   7篇
  1980年   7篇
  1979年   3篇
  1967年   2篇
  1966年   2篇
  1964年   2篇
  1961年   2篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
Because of their size, service times, and drain on server resources, multimedia objects require specialized replication systems in order to meet demand and ensure content availability. We present a novel method for creating replication systems where the replicated objects' sizes and/or per-object service times are large. Such replication systems are well-suited to delivering multimedia objects on the Internet. Assuming that user request patterns to the system are known, we show how to create replication systems that distribute read load to servers in proportion to their contribution to system capacity and experimentally show the positive load distribution properties of such systems. However, when user request patterns differ from what the system was designed for, system performance will be affected. Therefore, we also report on results that reveal (i) how server loads are affected and (ii) the impact two system design parameters (indicators of a system's load distribution qualities) have on server load when request patterns differ from that for which a system was designed.  相似文献   
82.
Recombinant approaches for tapping into the biodiversity present in nature for the discovery of novel enzymes and biosynthetic pathways can result in large gene libraries. Likewise, laboratory evolution techniques can result in large but potentially valuable libraries. Thorough screening of these libraries requires ultra high-throughput methods. The GigaMatrix screening platform addresses this opportunity using reusable high-density plates with 100,000 to 1,000,000 through-hole wells in a microplate footprint. In addition to throughputs of over 107 wells per day, the platform offers a significant reduction in reagent use and waste, has fully integrated automated “cherry picking,” and uses no complicated dispensing equipment. Wells containing putative hits from targeted fluorescent liquid phase assays are revealed by a fluorescent imaging system. Vision-guided robotics are utilized to recover hits by accessing individual 200 μm and smaller wells with a disposable sterile needle. The GigaMatrix platform has proven to be an effective and efficient tool for screening gene libraries for both discovery and evolution applications.  相似文献   
83.
This study investigates the coverage of federally mandated information on over‐the‐counter (OTC) drug labels by electronic article surveillance (EAS) tags applied to the exterior of cartons. Using adult‐strength analgesics containing acetaminophen as a case study, researchers investigated the issue in Houston, Texas (24 stores) and Lansing, Michigan (33 stores). The information obscured by EAS tags was identified and classified for a total of 849 packages using a standardized data collection instrument. The results indicated that 293 packages examined, or 34.5%, had information mandated by the US Food and Drug Administration (US FDA) fully or partially obscured by the EAS tags. Retailers and manufacturers should be aware of such practices to reduce potential liability. Recommendations for improving EAS tag usage on OTC products are presented. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
84.
This article provides an overview of the factors that may contribute to the effective term of protection for a pharmaceutical product in the USA––by patent and by FDA market exclusivities, identifies public and commercial sources for collecting relevant patent term and exclusivity data, and provides a strategy for ensuring that the effective term of protection has been calculated accurately.  相似文献   
85.
Although several studies have examined the relationship between intimate partner violence (IPV) and drug use among women in drug treatment programs, more information is needed to delineate differences, as a function of the specific drug used. Data from a random sample of 416 women attending methadone programs were analyzed to elucidate the differential associations between IPV and use of the following: marijuana only, cocaine only, heroin only, or cocaine and heroin. Prevalence of IPV among this sample far exceeded estimates from the general population. After adjusting for sociodemographic variables, use of cocaine only was significantly associated with an increased likelihood of experiencing IPV compared with no drug use. Similar results were found for women using both cocaine and heroin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
86.
In a nonclinical sample of 395 young adults, the authors evaluated the relations between major personality traits, Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) personality disorder symptoms, and DSM-IV alcohol use disorders (AUDs). Consistent with previous findings, traits related to disinhibition and negative affectivity were consistently associated with AUDs, as were Cluster B personality disorder symptoms (especially antisocial and borderline disorder symptoms). Multivariate analyses revealed that Cluster B symptoms were significantly associated with AUDs above and beyond what was accounted for by personality traits. Further, the authors found differential patterns of relations between other substance use disorders (SUDs; i.e., tobacco dependence and drug use diagnoses) and personality disorder symptoms. Overall, these results suggest that personality disorder symptoms predict unique variance in SUDs that reflect maladaptive aspects of personality traits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
87.
As the population of American Indians and Alaska Natives continues to expand in the 21st century United States, an increasing number of professional psychologists will be called upon to provide culturally appropriate mental health services for Native American people and their communities. This article provides a general overview of contemporary tribal America before describing the legal, political, and institutional contexts for mental health service delivery administered through the federally sponsored Indian Health Service. Recommendations for mental health professionals who desire to avoid a subtle but profound Western cultural proselytization in their therapeutic service to Native clients and their communities are presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
88.
The magnetic liquid was prepared with ferric salt by inorganic gel technology. The effect of the doped rare earth elements on the properties of magnetic particles was analyzed. The magnetic liquid was composed with clay mineral into magnetic mineral composites. The crystal structure and micro-morphology of the nanoparticles were studied by XRD and TEM. The results show that the crystal structure of the magnetic particles doped 0.5 % of lanthanum is more complete, and the magnetic response capability is higher with doping agent. At the same time, the possibility of the clay mineral magnetic composites as the carrier of target drug was probed.  相似文献   
89.
采用元胞自动机模型预测了西非36个地区埃博拉患者的未来人数,针对抗埃博拉病毒药物保质期较短的特点,根据所需药物数量设计出了该药物的二级配送系统,提出了最短时间配送系统、最低成本配送系统2种模型,并进一步阐述了运行效率更为高效的跨国界最低成本配送系统。更多还原  相似文献   
90.
结合唐钢连铸坯热送热装工作实践,提出做好生产组织协调提高企业整体管理水平是热送热装工作的关键,多品种,批量生产是提高热送热装率的有利条件。  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