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   450629篇
  免费   7225篇
  国内免费   1417篇
电工技术   7838篇
综合类   263篇
化学工业   72412篇
金属工艺   18503篇
机械仪表   13197篇
建筑科学   11264篇
矿业工程   2582篇
能源动力   11068篇
轻工业   43513篇
水利工程   4794篇
石油天然气   9419篇
武器工业   19篇
无线电   48227篇
一般工业技术   87063篇
冶金工业   81911篇
原子能技术   10639篇
自动化技术   36559篇
  2021年   3768篇
  2019年   3590篇
  2018年   6378篇
  2017年   6319篇
  2016年   6708篇
  2015年   4595篇
  2014年   7342篇
  2013年   20463篇
  2012年   11910篇
  2011年   15665篇
  2010年   12748篇
  2009年   14285篇
  2008年   14643篇
  2007年   14353篇
  2006年   12369篇
  2005年   11481篇
  2004年   10793篇
  2003年   10322篇
  2002年   10284篇
  2001年   10033篇
  2000年   9521篇
  1999年   9716篇
  1998年   24348篇
  1997年   17685篇
  1996年   13662篇
  1995年   10300篇
  1994年   9066篇
  1993年   8915篇
  1992年   6637篇
  1991年   6550篇
  1990年   6288篇
  1989年   6317篇
  1988年   6233篇
  1987年   5366篇
  1986年   5342篇
  1985年   6123篇
  1984年   5783篇
  1983年   5293篇
  1982年   4985篇
  1981年   5155篇
  1980年   4897篇
  1979年   4829篇
  1978年   4903篇
  1977年   5674篇
  1976年   7360篇
  1975年   4397篇
  1974年   4211篇
  1973年   4293篇
  1972年   3703篇
  1971年   3413篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
102.
103.
Microbial fuel cell (MFC) is a promising technology for simultaneous wastewater treatment and energy harvesting. The properties of the anode material play a critical role in the performance of the MFC. In this study, graphene oxide was prepared by a modified hummer's method. A thin layer of graphene oxide was incorporated on the carbon brush using an electrophoretic technique. The deoxygenated graphene oxide formed on the surface of the carbon brush (RGO-CB) was investigated as a bio-anode in MFC operated with real wastewater. The performance of the MFC using the RGO-CB was compared with that using plain carbon brush anode (PCB). Results showed that electrophoretic deposition of graphene oxide on the surface of carbon brush significantly enhanced the performance of the MFC, where the power density increased more than 10 times (from 33 mWm?2 to 381 mWm?2). Although the COD removal was nearly similar for the two MFCs, i.e., with PCB and RGO-CB; the columbic efficiency significantly increased in the case of RGO-CB anode. The improved performance in the case of the modified electrode was related to the role of the graphene in improving the electron transfer from the microorganism to the anode surface, as confirmed from the electrochemical impedance spectroscopy measurements.  相似文献   
104.
Morozov  Yu. D.  Pemov  I. F.  Matrosov  M. Yu.  Zin’ko  B. F. 《Metallurgist》2020,63(9-10):933-950
Metallurgist - We consider domestic and foreign standards for rolled metals used in bridge building. Domestic standards contain elevated requirements to the reliability of rolled metals in terms of...  相似文献   
105.
ABSTRACT

In this paper, we review some algebraic control system. Precisely, linear and bilinear systems on Euclidean spaces and invariant and linear systems on Lie groups. The fourth classes of systems have a common issue: to any class, there exists an associated subgroup. From this object, we survey the controllability property. Especially, from those coming from our contribution to the theory.  相似文献   
106.
Wireless Personal Communications - In this article compact multiple input multiple output (MIMO) antenna with triple notch at the ultra-wideband application having two identical monopole antennas...  相似文献   
107.
Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis...  相似文献   
108.
Refractories and Industrial Ceramics - The article is devoted to the preparation of ecologically clean composites by powder metallurgy and the study of tribological properties. Tribological tests...  相似文献   
109.
N. Boukortt  S. Patan&#;  G. Crupi 《SILICON》2020,12(7):1585-1591
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra  相似文献   
110.
Context: The administration of pharmabiotics is a promising alternative to antimicrobial drugs for the treatment and/or prevention of female urogenital infections.

Objective: To design pharmabiotic formulations including bioactive ingredients of microbial origin combined with non-microbial substances and then to evaluate the stability of the combinations during freeze-drying and storage.

Materials and methods: Different formulations including Lactobacillus gasseri CRL 1263, Lactobacillus salivarius CRL 1328, salivaricin CRL 1328 (a bacteriocin) and non-microbial compounds (lactose, inulin and ascorbic acid) were assayed, and the ingredients were freeze-dried together or separately. The formulations were stored in gelatin capsules at 4?°C for 360?d.

Results: The viability of lactobacilli was affected to different extents depending on the strains and on the formulations assayed. L. salivarius and ascorbic acid were successfully combined only after the freeze-drying process. Salivaricin activity was not detected in formulations containing L. gasseri. However, when combined with ascorbic acid, lactose, inulin or L. salivarius, the bacteriocin maintained its activity for 360?d. The selected microorganisms proved to be compatible for their inclusion in multi-strain formulations together with lactose, inulin and ascorbic acid. Salivaricin could be included only in a L. salivarius CRL 1328 single-strain formulation together with non-microbial substances.

Conclusions: This study provides new insights into the design of urogenital pharmabiotics combining beneficial lactobacilli, salivaricin CRL 1328 and compounds with different functionalities.  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