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   2868篇
  免费   34篇
电工技术   12篇
综合类   1篇
化学工业   208篇
金属工艺   17篇
机械仪表   16篇
建筑科学   46篇
矿业工程   1篇
能源动力   14篇
轻工业   109篇
水利工程   9篇
石油天然气   9篇
无线电   135篇
一般工业技术   226篇
冶金工业   1981篇
原子能技术   18篇
自动化技术   100篇
  2021年   12篇
  2020年   9篇
  2019年   9篇
  2018年   10篇
  2017年   22篇
  2016年   16篇
  2015年   14篇
  2014年   30篇
  2013年   50篇
  2012年   34篇
  2011年   41篇
  2010年   29篇
  2009年   34篇
  2008年   35篇
  2007年   43篇
  2006年   24篇
  2005年   37篇
  2004年   31篇
  2003年   34篇
  2002年   35篇
  2001年   32篇
  2000年   25篇
  1999年   78篇
  1998年   598篇
  1997年   381篇
  1996年   249篇
  1995年   122篇
  1994年   108篇
  1993年   120篇
  1992年   30篇
  1991年   32篇
  1990年   36篇
  1989年   47篇
  1988年   42篇
  1987年   43篇
  1986年   31篇
  1985年   34篇
  1984年   17篇
  1983年   19篇
  1982年   18篇
  1981年   14篇
  1980年   27篇
  1979年   14篇
  1978年   24篇
  1977年   39篇
  1976年   87篇
  1974年   6篇
  1973年   8篇
  1972年   10篇
  1968年   7篇
排序方式: 共有2902条查询结果,搜索用时 15 毫秒
141.
Objective: To examine the relationship between adult attachment style and physical disability in intimate romantic relationships. Method: Participants were 50 individuals with adult-onset spinal cord injuries (SCI) and 50 individuals with congenital disabilities (CON) living in the community. The main outcome measures were adult attachment style and dyadic relationship adjustment. Results: Participants with SCI and CON did not differ in rates of secure versus insecure attachment, and the rates of neither group differed significantly from rates reported for persons without disability. Dyadic adjustment was clearly predicted by attachment variables and differed between the participants with SCI and those with CON; individuals with SCI reported greater total dyadic adjustment. Avoidance showed a strong negative association with dyadic satisfaction, but no association was found with dyadic cohesion. Social participation variables were associated with dyadic adjustment. For instance, mobility was positively associated with dyadic satisfaction. Conclusions: Dyadic adjustment in people with disabilities, as in other groups, is affected by attachment style, but disability and social participation variables may also affect dyadic adjustment. Clinicians should consider differences in attachment styles among persons with disabilities and their implications for intimate close relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
142.
Professional engineering licensure is important in the career development of engineers who undertake work critical to protecting public health, safety, and welfare. The knowledge and experience of construction engineers has not previously been well represented in professional engineering licensure evaluation. The ASCE-CI Construction Engineering Education Committee identified recognition of construction engineering in the professional engineering licensure process as one of its missions when it was organized in 1995. With the support of the states and the receptiveness of the National Council of Examiners for Engineering and Surveying (NCEES), improvements were gradually achieved in recognition of construction engineering experience by changes in NCEES Model Rules. In 2003, the NCEES Board decided to evaluate modification of the Civil Engineering PE exam to include a Construction Engineering module. The evaluation included a Professional Activities and Knowledge Study (PAKS) of the skills appropriate for construction engineers. Following approval of the NCEES Board in 2005, exam development has been underway with implementation planned for April 2008. An additional benefit of the PAKS is the improved understanding of knowledge needed by construction engineers in completing their work activities. These results should be valuable to construction engineering education and industry in identifying critical subject matter for inclusion in courses, curriculums, and continuing education.  相似文献   
143.
For quality verification, an X-ray inspection process is commonly being used for evaluating obscured and defective solder joints in surface-mount technologies, such as ball grid arrays and flip chips. Integrated circuits subjected to any form of radiation, i.e., ionizing or nonionizing, may incur some amount of damage depending on the absorbed dose. Though most X-ray inspections for high-quality imaging require ionizing dose amounts that are considered inconsequential for device failure or non-functionality, the degree of latent damage must be carefully considered. This paper discusses X-ray-induced vulnerabilities of high-density dynamic random access memory exposed to low ionizing radiation levels typical in X-ray inspection systems. We look at critical parameters and their sensitivity in relation to varying dose amounts of X-ray irradiation. In consideration of different methodologies of reducing radiation dose amounts and limiting device exposure, we propose a procedure for attenuating potentially harmful X-ray radiation levels while preserving quality images.  相似文献   
144.
Development of behavioral pattern recognition and analysis skills is an essential element of Counter-Terrorism training, particularly in the field. Three classes of behavioral measures were collected in an assessment of skill acquisition during a US Joint Forces Command-sponsored course consisting of Combat Tracking and Combat Profiling segments. Measures included situational judgment tests, structured behavioral observation checklists, and qualitative assessments of the emergence of specific knowledge–skills–attitudes over the course of the training. The paper describes statistical evidence across the three types of measures that indicate that behavioral pattern recognition and analysis skills were successfully acquired by most students (a mix of Army and civilian law enforcement personnel) during the field training exercises. Implications for broader training of these critical skills are also discussed.  相似文献   
145.

The ability to transmit particles into the ablation region of an aerosol mass spectrometer determines in part the lower size limit for particles that can be analyzed. A large fraction of small particles (< 100 nm) are lost due to processes such as Brownian diffusion that broaden the particle beam. In this work, electrostatic focusing is used to overcome the limits of aerodynamic focusing in the analysis of nanometer-sized particles by aerosol mass spectrometry. A simple tube lens is used to focus charged particles into the ablation laser beam path. The diameter of the focused beam is smaller than the fundamental aerodynamic limit imposed by Brownian motion. Measured enhancements of the hit rate for particles between 21 and 33 nm diameter are between 3 and 6. These values are lower limits for the true enhancements. The lens is also energy selective and can be used to select the mass (size) of the particles being analyzed.  相似文献   
146.
A study of 83 firms in the North American electronics industry that have implemented environmentally “clean” process technology found that social networks have a significant positive impact on implementation success. This paper presents evidence that some types of social networks influence implementation success more than others. More specifically, interfirm networks composed of both suppliers and competitors were significantly correlated with the routinization and incorporation of alternative technical solutions to reducing ozone depleting chlorofluorocarbons (CFCs). This only held in situations where the complexity of the implementation was relatively high. Intrafirm and local social networks were not significant. The utilization of a network of publicly accessible sources of information and expertise had a negative impact. Brief case studies from field research are provided to help explain these results  相似文献   
147.
148.
Compared initial and 3-yr follow-up peer ratings of 19 boys, who were in Grades 1–3 at the beginning of the study, who had attention deficit disorder with hyperactivity (ADDH). When the entire group was considered, nominations on the Aggression and Likability factors of a pupil evaluation inventory improved. Subgroups were created using teacher ratings on an aggression scale. Peer ratings of Aggression improved for Ss whom teachers rated below the median on the aggression scale but not for Ss rated above the median. Subgroups reflecting other teacher and peer ratings were less effective in predicting differential change in peer ratings of ADDH Ss. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
149.
A novel feed technique for a hybrid resonator antenna is proposed and developed. The antenna consists of microstrip-patch radiator and a pair of twin resonator slots. The proposed feed mechanism is based on a new coupling aperture technique, in which a single microstrip feed line is etched on the same side of the substrate as the radiating patches. The patches are coupled to the feed line through a twin slots located in the ground plane. By selecting suitable structure parameters for the slots and the patches, multifrequency operation is obtained. The proposed antenna structure is suitable for the development of large antenna arrays.  相似文献   
150.
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