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   387726篇
  免费   6197篇
  国内免费   1398篇
电工技术   6648篇
综合类   637篇
化学工业   58127篇
金属工艺   17971篇
机械仪表   14330篇
建筑科学   9074篇
矿业工程   2325篇
能源动力   8822篇
轻工业   31224篇
水利工程   4369篇
石油天然气   7255篇
武器工业   50篇
无线电   41450篇
一般工业技术   80439篇
冶金工业   64216篇
原子能技术   8648篇
自动化技术   39736篇
  2021年   3416篇
  2020年   2560篇
  2019年   3130篇
  2018年   12705篇
  2017年   13209篇
  2016年   9731篇
  2015年   4247篇
  2014年   6088篇
  2013年   15344篇
  2012年   11884篇
  2011年   19964篇
  2010年   16985篇
  2009年   16876篇
  2008年   16909篇
  2007年   18555篇
  2006年   9194篇
  2005年   11652篇
  2004年   10004篇
  2003年   9387篇
  2002年   8183篇
  2001年   7524篇
  2000年   7216篇
  1999年   7423篇
  1998年   18788篇
  1997年   13274篇
  1996年   10089篇
  1995年   7555篇
  1994年   6587篇
  1993年   6710篇
  1992年   4651篇
  1991年   4452篇
  1990年   4253篇
  1989年   4266篇
  1988年   3946篇
  1987年   3564篇
  1986年   3537篇
  1985年   3937篇
  1984年   3617篇
  1983年   3347篇
  1982年   3169篇
  1981年   3197篇
  1980年   3196篇
  1979年   2921篇
  1978年   2959篇
  1977年   3450篇
  1976年   4759篇
  1975年   2482篇
  1974年   2430篇
  1973年   2475篇
  1972年   2047篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Wireless Personal Communications - Chronic kidney disease (CKD) is a gradual loss of kidney function over the period of time and it is irrevocable once functionality reaches the critical state....  相似文献   
3.
4.
Food Science and Biotechnology - A rich source of nutrients, figs have a number of clinically validated benefits. This study aimed to evaluate the in vitro simulated gastrointestinal digestion, and...  相似文献   
5.
Multimedia Tools and Applications - In this work, a new fuzzy logic-based algorithm is proposed for the enhancement of low light color images. A generalization of a fuzzy set known as an...  相似文献   
6.

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.

  相似文献   
7.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
8.
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in...  相似文献   
9.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials.  相似文献   
10.
Our aim was to investigate the subset distribution and function of circulating monocytes, proinflammatory cytokine levels, gut barrier damage, and bacterial translocation in chronic spinal cord injury (SCI) patients. Thus, 56 SCI patients and 28 healthy donors were studied. The levels of circulating CD14+highCD16, CD14+highCD16+, and CD14+lowCD16+ monocytes, membrane TLR2, TLR4, and TLR9, phagocytic activity, ROS generation, and intracytoplasmic TNF-α, IL-1, IL-6, and IL-10 after lipopolysaccharide (LPS) stimulation were analyzed by polychromatic flow cytometry. Serum TNF-α, IL-1, IL-6 and IL-10 levels were measured by Luminex and LPS-binding protein (LBP), intestinal fatty acid-binding protein (I-FABP) and zonulin by ELISA. SCI patients had normal monocyte counts and subset distribution. CD14+highCD16 and CD14+highCD16+ monocytes exhibited decreased TLR4, normal TLR2 and increased TLR9 expression. CD14+highCD16 monocytes had increased LPS-induced TNF-α but normal IL-1, IL-6, and IL-10 production. Monocytes exhibited defective phagocytosis but normal ROS production. Patients had enhanced serum TNF-α and IL-6 levels, normal IL-1 and IL-10 levels, and increased circulating LBP, I-FABP, and zonulin levels. Chronic SCI patients displayed impaired circulating monocyte function. These patients exhibited a systemic proinflammatory state characterized by enhanced serum TNF-α and IL-6 levels. These patients also had increased bacterial translocation and gut barrier damage.  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