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   28635篇
  免费   1086篇
  国内免费   110篇
电工技术   373篇
综合类   228篇
化学工业   5141篇
金属工艺   631篇
机械仪表   583篇
建筑科学   977篇
矿业工程   93篇
能源动力   936篇
轻工业   3879篇
水利工程   242篇
石油天然气   150篇
武器工业   6篇
无线电   2255篇
一般工业技术   4125篇
冶金工业   6215篇
原子能技术   239篇
自动化技术   3758篇
  2024年   50篇
  2023年   152篇
  2022年   504篇
  2021年   791篇
  2020年   544篇
  2019年   606篇
  2018年   694篇
  2017年   770篇
  2016年   727篇
  2015年   561篇
  2014年   863篇
  2013年   1420篇
  2012年   1273篇
  2011年   1601篇
  2010年   1168篇
  2009年   1210篇
  2008年   1103篇
  2007年   963篇
  2006年   778篇
  2005年   841篇
  2004年   905篇
  2003年   811篇
  2002年   792篇
  2001年   690篇
  2000年   540篇
  1999年   525篇
  1998年   2026篇
  1997年   1318篇
  1996年   919篇
  1995年   598篇
  1994年   471篇
  1993年   528篇
  1992年   217篇
  1991年   282篇
  1990年   224篇
  1989年   190篇
  1988年   205篇
  1987年   158篇
  1986年   163篇
  1985年   178篇
  1984年   128篇
  1983年   90篇
  1982年   116篇
  1981年   120篇
  1980年   114篇
  1979年   90篇
  1978年   74篇
  1977年   138篇
  1976年   224篇
  1975年   82篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
Fractal dimension applied to plant identification   总被引:2,自引:0,他引:2  
This article discusses methods to identify plants by analysing leaf complexity based on estimating their fractal dimension. Leaves were analyzed according to the complexity of their internal and external shapes. A computational program was developed to process, analyze and extract the features of leaf images, thereby allowing for automatic plant identification. Results are presented from two experiments, the first to identify plant species from the Brazilian Atlantic forest and Brazilian Cerrado scrublands, using fifty leaf samples from ten different species, and the second to identify four different species from genus Passiflora, using twenty leaf samples for each class. A comparison is made of two methods to estimate fractal dimension (box-counting and multiscale Minkowski). The results are discussed to determine the best approach to analyze shape complexity based on the performance of the technique, when estimating fractal dimension and identifying plants.  相似文献   
84.
This paper reports results of research into the definition of requirements for new consumer products––specifically, electro-mechanical products. The research dealt with the derivation of design requirements that are demonstrably aligned with stakeholder needs. The paper describes a comprehensive process that can enable product development teams to deal with statements of product requirements, as originally collected through market research activities, in a systematic and traceable manner from the early, fuzzy front end, stages of the design process. The process described has been based on principles of systems engineering. A case study from its application and evaluation drawn from the power sector is described in this paper. The case study demonstrates how the process can significantly improve product quality planning practices through revision of captured product requirements, analysis of stakeholder requirements and derivation of design requirements. The paper discusses benefits and issues from the use of the process by product development teams, and identifies areas for further research. Finally, the conclusions drawn from the reported research are presented.
Vassilis AgouridasEmail:
  相似文献   
85.
86.
Bacterial populations associated with poultry processing were determined on neck skin samples, equipment surfaces and environmental samples by replicate surveys. Aerobic plate counts, Enterobacteriaceae counts, Enterobacteriaceae counts and Pseudomonas counts were performed by standard procedures and the prevalence of Listeria, presumptive Salmonella and Staphylococcus aureus determined. Statistically significant (P < 0.05) increases in counts of all types of bacteria were obtained on product samples as a result of processing. Although bacterial counts on neck skin samples decreased by 0.3 to 0.4 log CFU g-1 after spray washing of carcasses, subsequent spinchilling and packaging of whole carcasses resulted in 0.7 to 1.2 log CFU g-1 increases. Bacterial numbers on equipment surfaces, however, decreased significantly from the "dirty" to the "clean" areas of the abattoir. Transport cages, "rubber fingers", defeathering curtains, shackles and conveyor belts repeatedly showed aerobic plate counts in excess of 5.0 log CFU 25 cm-2. Aerobic plate counts of scald tank and spinchiller water were 2 log CFU ml-1 higher than those of potable water samples. Bacterial numbers of the air in the "dirty" area were higher than those of the "clean" area. Listeria, presumptive Salmonella and Staphylococcus aureus were isolated from 27.6, 51.7 and 24.1% of all product samples, respectively, and Listeria and Staphylococcus aureus were also isolated from selected equipment surfaces.  相似文献   
87.
Pouliquen  M.  Denoual  M.  Jorel  C.  Radu  C.  Robbes  D.  Grand  J.  Awala  H.  Mintova  S.  Harnois  M.  Sagazan  O. de  Inoue  S.  Lebrasseur  E.  Yamada  K.  Okamoto  Y.  Mita-Tixier  A.  Mita  Y. 《Microsystem Technologies》2022,28(6):1313-1319
Microsystem Technologies - We demonstrate a new operation mode of thermal gas sensor based on thermal capacity extraction with identification algorithm. The system is a silicon microstructure...  相似文献   
88.
International Journal of Computer Vision - Semantic scene completion (SSC) aims to jointly estimate the complete geometry and semantics of a scene, assuming partial sparse input. In the last years...  相似文献   
89.
Although enthusiasm for measuring health-related quality of life (HRQL) in clinical trials exists, information is limited on the meaning of scores. We examined the relation between scores from the 34-item Medical Outcomes Study HIV Health Survey (MOS-HIV) and the more detailed HIV Overview of Problems-Evaluation System (HOPES) using the responses of 318 HIV-infected outpatients being treated in Los Angeles and Baltimore. With the HOPES problem statements as independent variables, statistically significant predictors of the variation in MOS-HIV scores for the Physical Function, Mental Health, and Energy/Fatigue scales were identified using stepwise regression. Approximately 60% to 70% of the variation in each of the scores was explained by five to seven different HOPES problem statements, with a single item explaining 47% to 59% of the variation. We created illustrative profiles for each of the three MOS-HIV scales using the HOPES items identified in the regressions. Independent of the scale, persons scoring in the top MOS-HIV quartile tended to report few if any problems, whereas a decline in score to the next quartile was characterized by functional difficulties (e.g., "HIV interferes with work"). The onset of specific problems might trigger further evaluation and potential intervention from health care providers to help maintain patient functioning.  相似文献   
90.
Ferromagnetic and perovskite-like thin films (<1m) of La1–xCaxMnO3+ have been routinely prepared by heat treatment of an amorphous La–Ca–Mn precursor. The precursor was electrodeposited cathodically in the absence of oxygen and water onto polished silver substrates from a nonaqueous solution of the components' nitrates. Analysis by X-ray diffraction and SQUID magnetometry shows these materials exhibit the appropriate structural and magnetic phases indicative of colossal magnetoresistance.  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