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   5696篇
  免费   138篇
  国内免费   87篇
电工技术   56篇
综合类   125篇
化学工业   448篇
金属工艺   218篇
机械仪表   100篇
建筑科学   308篇
矿业工程   30篇
能源动力   42篇
轻工业   293篇
水利工程   38篇
石油天然气   38篇
武器工业   24篇
无线电   294篇
一般工业技术   562篇
冶金工业   2922篇
原子能技术   42篇
自动化技术   381篇
  2023年   23篇
  2022年   58篇
  2021年   61篇
  2020年   50篇
  2019年   59篇
  2018年   56篇
  2017年   50篇
  2016年   39篇
  2015年   63篇
  2014年   83篇
  2013年   142篇
  2012年   141篇
  2011年   160篇
  2010年   127篇
  2009年   129篇
  2008年   140篇
  2007年   153篇
  2006年   189篇
  2005年   140篇
  2004年   104篇
  2003年   108篇
  2002年   111篇
  2001年   84篇
  2000年   63篇
  1999年   142篇
  1998年   802篇
  1997年   504篇
  1996年   338篇
  1995年   205篇
  1994年   180篇
  1993年   220篇
  1992年   67篇
  1991年   47篇
  1990年   69篇
  1989年   69篇
  1988年   48篇
  1987年   52篇
  1986年   44篇
  1985年   50篇
  1984年   29篇
  1983年   26篇
  1982年   36篇
  1981年   31篇
  1980年   39篇
  1979年   26篇
  1978年   31篇
  1977年   84篇
  1976年   177篇
  1975年   26篇
  1974年   18篇
排序方式: 共有5921条查询结果,搜索用时 31 毫秒
1.
近年来澜沧江公司对安全生产工作采取了强有力手段,安全生产基础不断夯实。如何将安全工作推进更深的层次,如何把控"准入关",将信用评价纳入安全生产不失为一个行之有效的方式。安全信用评价是建立水电工程施工安全信用体系的重要手段,能够促进整体行业安全管理水平的提升。  相似文献   
2.
Primary care physicians can easily incorporate efforts toward the primary and secondary prevention of family violence into their practices. By designing a preventive effort using the phases of the family life cycle, a developmentally appropriate system of prevention is created. The anticipatory guidance at each (annual) visit acknowledges family transitions and assures the family that abuse is a health issue and that the physician is a resource for issues of violence prevention. Using the FLC, the first phase is Coupling, when there is a risk of partner violence that continues as long as there is a partnership. Pregnancy and childbirth bring concerns of child neglect and battery. Older children are at additional risk for child sexual abuse. As families age, risks develop for elder abuse, too. The regular discussion of these issues raises the awareness that the potential for family violence continues over the life span and allows the physician opportunities to assess the risk of violence in that family and make appropriate preventive referrals. Primary care physicians are optimally positioned to address violence and its prevention in the office: they know and care for family units over time. Physicians are respected and trusted advisors who can become effective in preventing violence.  相似文献   
3.
Two experiments with Sprague Dawley rats tested their ability to hydrolyse myristoyl-methionine (M-M) into myristic acid and L-methionine (M). In the first experiment, lasting for 3 days. male rats were orally administered [9,10-3H]myristoyl-L-[35S]methionine. The recovery of radioactivity was approximately 90% for both isotopes; 19% of the administered 3H was recovered in the urine and 16% in the faeces, while the recovered 35S activity was 13 and 12%, respectively. The balance of the radioactivity was found among the tissues, organs and blood. In the second experiment, male and female rats received soybean-based diets which were supplemented with either 0.305% M-M or 0.2% M (both diets contained equal amounts of M) for periods up to 4 weeks. The growth rate of the rats receiving the 0.305% M-M diets was slightly slower than that for the rats on the 0.2% M diet, but the difference was not statistically significant (P > 0.05). The M-M rats had a transitory decrease in feed consumption, suggesting that palatability may have contributed to the growth difference and that a somewhat greater amount of M-M was necessary for the rat to attain the same growth rate as that produced by 0.2% M. When the amount of dietary M-M was increased to 3.05% M-M, a greater reduction in feed consumption and body weight gain was observed. This latter diet was an initial attempt to study the potential toxicity of M-M. None of the haematological, clinical chemistry or organ weight data suggested that M-M was overtly toxic per se, but longer-term feeding studies are needed to evaluate the potential toxicity of M-M more fully.  相似文献   
4.
5.
水蒸汽喷射泵系统实用设计软件的开发   总被引:3,自引:0,他引:3  
本文在Turboc环境下开发了多级蒸汽喷射泵系统的设计软件,该软件包括了压缩比优化分配、单级喷射泵结构尺寸设计和冷凝器的结构尺寸设计等内容,使设计人员能够根据具体的工艺条件,快速地完成多级喷射泵系统的设计,对于提高多级喷射泵系统的工作稳定性、节省能源具有实际意义。  相似文献   
6.
It is well known that tile-boundary artifacts occur in wavelet-based lossy image coding. However, until now, their cause has not been understood well. In this paper, we show that boundary artifacts are an inescapable consequence of the usual methods used to choose tile size and the type of symmetric extension employed in a wavelet-based image decomposition system. This paper presents a novel method for reducing these tile-boundary artifacts. The method employs odd tile sizes (2N + 1 samples) rather than the conventional even tile sizes (2N samples). It is shown that, for the same bit rate, an image compressed using an odd tile length low-pass first (OTLPF) convention has significantly less boundary artifacts than an image compressed using even tile sizes. The OTLPF convention can also be incorporated into the JPEG 2000 image compression algorithm using extensions defined in Part 2 of this standard.  相似文献   
7.
We discuss some different ideas about the sort of formalism appropriate for translation (more specifically, transfer) that have been explored within Eurotra. The intention is not to evaluate these different ideas, but to outline the issues of general interest and relevance that they raise. Section 1 describes some common assumptions, section 2 describes the different ways they have been interpreted, and section 3 considers some further implications.  相似文献   
8.
9.
10.
We report the evaluation of 1036 bovine microsatellite primer pairs for their suitability as linkage markers in sheep. Approximately 58% (605/1036) of bovine primer pairs amplified a locus in sheep. Sixty-seven per cent (409/605) of amplified loci were detected as polymorphic. Marker heterozygosity, allele number and range of allele sizes were significantly lower in sheep than cattle sampled in this study. However, median fragment size was similar. These data suggest that high-resolution comparative linkage maps between closely related species can be constructed relatively efficiently.  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