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   38123篇
  免费   1384篇
  国内免费   80篇
电工技术   405篇
综合类   41篇
化学工业   7537篇
金属工艺   831篇
机械仪表   803篇
建筑科学   2066篇
矿业工程   121篇
能源动力   1090篇
轻工业   3006篇
水利工程   446篇
石油天然气   140篇
武器工业   5篇
无线电   2622篇
一般工业技术   6359篇
冶金工业   7015篇
原子能技术   345篇
自动化技术   6755篇
  2023年   221篇
  2022年   463篇
  2021年   713篇
  2020年   479篇
  2019年   638篇
  2018年   805篇
  2017年   727篇
  2016年   865篇
  2015年   800篇
  2014年   1074篇
  2013年   2459篇
  2012年   1732篇
  2011年   2185篇
  2010年   1708篇
  2009年   1615篇
  2008年   1890篇
  2007年   1855篇
  2006年   1673篇
  2005年   1498篇
  2004年   1224篇
  2003年   1176篇
  2002年   1086篇
  2001年   729篇
  2000年   579篇
  1999年   633篇
  1998年   695篇
  1997年   630篇
  1996年   594篇
  1995年   609篇
  1994年   558篇
  1993年   542篇
  1992年   527篇
  1991年   311篇
  1990年   433篇
  1989年   407篇
  1988年   349篇
  1987年   391篇
  1986年   329篇
  1985年   441篇
  1984年   442篇
  1983年   330篇
  1982年   309篇
  1981年   296篇
  1980年   286篇
  1979年   285篇
  1978年   259篇
  1977年   247篇
  1976年   225篇
  1975年   203篇
  1974年   181篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
David Mills 《Granular Matter》2004,6(2-3):173-177
For fine powdered materials, capable of being conveyed in dense phase, a conveying region exists in which instability in flow and pipeline blockage can occur if the pressure gradient available is insufficient to maintain a minimum value of solids loading ratio. A reduction in material flow rate can also lead to pipeline blockage in this region. Conveying trials under-taken with cement are used to illustrate the nature of the problem.  相似文献   
72.
73.
Evaluating the design of flexible manufacturing systems is complex. Developing a measure of performance useful for evaluating alternate designs continues to be interesting. Here, total productivity of the system is proposed as an appropriate measure. Specification of parameters based upon strategic considerations for this measure are discussed. Finally, the usefulness of the measure is demonstrated through an example.  相似文献   
74.
Studied the differences in moral orientation in terms of gender specific modes of reasoning, in 2 experiments. In Exp 1, 32 Ss (aged 24–55 yrs) were read the "Heinz dilemma," and asked 3 questions regarding it. Deliberative and justificatory strategies were identified on the basis of the presence or absence of the higher level knowledge structures. In Exp 2, 40 undergraduates were presented with "Michael and Kohlberg Heinz dilemma," followed by a set of relevant questions. Male Ss preferred to apply a norm or rule in their solutions, while females rejected the application of a norm and sought alternative solutions. This was replicated in Exp 2, but the pattern was reversed with female Ss preferring to apply a norm. Males were divided in their use of either strategy indicating that although, genders differed in their judgments as to which norms or rules to apply; once adopted, norms and rules were used in similar ways. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
75.
A dicing process for GaAs MMIC (monolithic microwave integrated circuit) wafers using spin-on wax for wafer mounting and a hybrid process of wet chemical etching/mechanical sawing for chip dicing is described. This process minimizes ragged chip edges and reduces generation of microcracks in addition to the elimination of the plated gold burrs on the backside of the diced MMIC chips. This process gives a uniformity of -3 μm across a 2-in wafer following the completion of the whole backside process. This GaAs chip dicing technique is amenable to production because it exhibits both a very high chip yield (>90%) and nearly flawless edges  相似文献   
76.
77.
The effects of celebrity self-disclosure of HIV seropositivity on perceptions of HIV and AIDS were investigated. AIDS-related interest and knowledge measures were collected from 468 men before and after basketball star Earvin "Magic" Johnson's self-disclosure of HIV seropositivity. Increased interest in AIDS paralleled media coverage of the announcement, with the most substantial effects occurring within 2 wks. Perceived impact of the disclosure was greatest among African-American men and men who had not previously known someone with HIV/AIDS. Celebrity self-disclosure appears to affect perceptions through mechanisms similar to those involved in personally knowing someone infected with HIV. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
78.
Investigated relationships between the performance levels of incumbents on job skills and the importance attributed to those job skills. Supervisors and job incumbents rated both the performance of skill dimensions and the importance of those skills for respective incumbents' positions. Results indicate that the ratings of performance and importance on matched skill areas correlated positively, although relationships were somewhat stronger for incumbent data as compared with data provided by supervisors. Supervisors and incumbents agreed moderately on which skill areas were important for various positions, but the interrater agreement was much lower for performance ratings of the skill areas. For some skill areas, incumbent-rated importance and supervisor-rated performance, as well as incumbent-rated performance and supervisor-rated importance, were significantly correlated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
79.
80.
The photosensitizing properties of p-nitroacetophenone (PNAP), a well-known radiosensitizer, have been studied in near UV region. The mechanism of PNAP photosensitization has been investigated by testing the efficiency of singlet oxygen production using photooxidation of 2,2,6,6-tetramethylpiperidine (TEMP) and photodegradation of guanosine. In both the cases, the enhancement effect of deuterated solvents has been observed. Results of these experiments suggest the significant role of type II mechanisms in PNAP photosensitization.  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