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   16339篇
  免费   877篇
  国内免费   28篇
电工技术   179篇
综合类   43篇
化学工业   3580篇
金属工艺   333篇
机械仪表   347篇
建筑科学   710篇
矿业工程   46篇
能源动力   521篇
轻工业   1398篇
水利工程   127篇
石油天然气   60篇
无线电   1150篇
一般工业技术   3060篇
冶金工业   2350篇
原子能技术   121篇
自动化技术   3219篇
  2023年   175篇
  2022年   381篇
  2021年   621篇
  2020年   403篇
  2019年   419篇
  2018年   546篇
  2017年   500篇
  2016年   569篇
  2015年   498篇
  2014年   626篇
  2013年   1118篇
  2012年   1020篇
  2011年   1215篇
  2010年   846篇
  2009年   785篇
  2008年   817篇
  2007年   805篇
  2006年   599篇
  2005年   529篇
  2004年   387篇
  2003年   388篇
  2002年   350篇
  2001年   226篇
  2000年   190篇
  1999年   215篇
  1998年   243篇
  1997年   208篇
  1996年   203篇
  1995年   187篇
  1994年   160篇
  1993年   157篇
  1992年   123篇
  1991年   75篇
  1990年   125篇
  1989年   118篇
  1988年   83篇
  1987年   95篇
  1986年   101篇
  1985年   101篇
  1984年   88篇
  1983年   76篇
  1982年   96篇
  1981年   90篇
  1980年   71篇
  1979年   71篇
  1978年   63篇
  1977年   74篇
  1976年   66篇
  1975年   45篇
  1974年   41篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
The authors report on the viscoelastic characterization of guar hydrogels obtained through complexation reactions with borax ions. These gels are compared with hydrogels obtained from poly(vinyl alcohol) of different degree of hydrolysis through complexation reactions with congo red. The effect of the degree of hydrolysis and both, the concentration of PVA and the concentration of congo red, on the viscoelastic properties of the hydrogels is analyzed. The potential use of the PVA‐based hydrogels as hydraulic fracturing liquids is discussed in relation to the commonly used fracturing liquid based on the guar–borax system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
62.
It's no longer just black hats or white hats in computer security. The more someone has to lose, the less likely they should be to trust the computer. It means that all people, all programs, all transactions are shades of grey. Black and white are just a memory.  相似文献   
63.
OBJECTIVE: The objective of this review was to evaluate the clinical and research literature on professionally-led support groups for cancer patients and to propose an approach that would address patients' needs from diagnosis through survivorship. METHOD: Computerized and manual searches, including Medline and Psychlit searches, were completed for reviews of the literature. Twelve research studies were identified that met our criteria for in-depth review. A clinical model emerged from discussions of an oncology study group based on theoretical formulations and clinical experience with oncology patients. RESULTS: We found that recent research suggests that professionally-led support groups are increasing in number and that participation in such groups seems to enhance patients' quality, and possibly even quantity, of survival. Despite this, little effort has been made to determine what type of group may be appropriate for which patients and when in their course of care. CONCLUSIONS: If psychosocial intervention, in the form of professionally-led support groups for cancer patients, is to be more effective, it should be guided by a model which takes into consideration the changing needs and concerns of patients over the course of illness and, in many cases, recovery. The authors present an outline delineating what such a model might entail.  相似文献   
64.
Parents (N?=?124) who had lost an infant to sudden infant death syndrome were interviewed 3 wks and 18 mo postloss. Two components of religion (religious participation and religious importance) were assessed, and their relations with 3 coping-process variables (perceived social support, cognitive processing of the loss, and finding meaning in the death) were examined. Greater religious participation was related to increased perception of social support and greater meaning found in the loss. Importance of religion was positively related to cognitive processing and finding meaning in the death. Furthermore, through these coping-process variables, religious participation and importance were indirectly related to greater well-being and less distress among parents 18 mo after their infants' deaths. Results suggest that further study of the social and cognitive aspects of religion would be profitable. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
65.
The distillation in the fine and high vacuum range requires not only appropriate vacuum pumps but also special apparatus and machines. The principle and the design of laboratory and industrial plants are explained. New mathematical methods are supporting laboratory and pilot testing required for process development and plant layout. An example was chosen for demonstration purposes.  相似文献   
66.
67.
68.
This paper describes interactive facilities for simulating abstract muscle actions using Rational Free Form Deformations (RFFD). The particular muscle action is simulated as the displacement of the control points of the control-unit for an RFFD defined on a region of interest. One or several simulated muscle actions constitute a Minimum Perceptible Action (MPA), which is defined as the atomic action unit, similar to Action Unit (AU) of the Facial Action Coding System (FACS), to build an expression.  相似文献   
69.
70.
Given integers m and n, we study the probability that structures of size n have all components of size at most m. The results are given in term of a generalized Dickman function of n/m.  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