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   23632篇
  免费   1039篇
  国内免费   167篇
电工技术   392篇
综合类   39篇
化学工业   5099篇
金属工艺   730篇
机械仪表   735篇
建筑科学   421篇
矿业工程   60篇
能源动力   1645篇
轻工业   1397篇
水利工程   185篇
石油天然气   110篇
武器工业   1篇
无线电   2958篇
一般工业技术   5404篇
冶金工业   2122篇
原子能技术   206篇
自动化技术   3334篇
  2024年   110篇
  2023年   481篇
  2022年   1088篇
  2021年   1310篇
  2020年   1026篇
  2019年   1041篇
  2018年   1356篇
  2017年   1080篇
  2016年   1086篇
  2015年   695篇
  2014年   993篇
  2013年   1890篇
  2012年   1083篇
  2011年   1295篇
  2010年   1043篇
  2009年   1064篇
  2008年   885篇
  2007年   698篇
  2006年   590篇
  2005年   475篇
  2004年   365篇
  2003年   338篇
  2002年   269篇
  2001年   246篇
  2000年   232篇
  1999年   233篇
  1998年   434篇
  1997年   345篇
  1996年   341篇
  1995年   249篇
  1994年   239篇
  1993年   226篇
  1992年   163篇
  1991年   199篇
  1990年   166篇
  1989年   143篇
  1988年   126篇
  1987年   132篇
  1986年   116篇
  1985年   132篇
  1984年   105篇
  1983年   95篇
  1982年   85篇
  1981年   104篇
  1980年   67篇
  1979年   61篇
  1978年   56篇
  1977年   54篇
  1976年   68篇
  1975年   27篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.  相似文献   
9.
Context and objective: The aim of this study was to develop, characterize and evaluate a mucoadhesive caplet resulting from a polymeric blend (polymeric caplet) for intravaginal anti-HIV-1 delivery.

Materials and methods: Poly(lactic-co-glycolic) acid, ethylcellulose, poly(vinylalcohol), polyacrylic acid and modified polyamide 6, 10 polymers were blended and compressed to a caplet-shaped device, with and without two model drugs 3′-azido-3′-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Thermal analysis, infrared spectroscopy and microscopic analysis were carried out on the caplets employing temperature-modulated DSC (TMDSC), Fourier transform infra-red (FTIR) spectrometer and scanning electron microscope, respectively. In vitro and in vivo drug release analyses as well as the histopathological toxicity studies were carried out on the drug-loaded caplets. Furthermore, molecular mechanics (MM) simulations were carried out on the drug-loaded caplets to corroborate the experimental findings.

Results and discussion: There was a big deviation between the Tg of the polymeric caplet from the Tg's of the constituent polymers indicating a strong interaction between constituent polymers. FTIR spectroscopy confirmed the presence of specific ionic and non-ionic interactions within the caplet. A controlled near zero-order drug release was obtained for AZT (20 d) and PSS (28 d). In vivo results, i.e. the drug concentration in plasma ranged between 0.012–0.332?mg/mL and 0.009–0.256?mg/mL for AZT and PSS over 1–28 d.

Conclusion: The obtained results, which were corroborated by MM simulations, attested that the developed system has the potential for effective delivery of anti-HIV-agents.  相似文献   
10.
The present work is an attempt to investigate the adoption of sustainable supply chain management (SSCM) practices amongst manufacturing and process based organisations in India and its impact on organisational performance encompassing all three dimensions of sustainability. SSCM practices conceived in the present study include environmental management practices (EMP), socially inclusive practices for employees (SPE), socially inclusive practices for community (SPC), operations practices (OP) and supply chain integration (SCI) which were treated as exogenous variables. Organisational performance considered in this study includes five dimensions, namely environmental performance (EPR), employee-centred social performance (ESP), community-centred social performance (CSP), operations performance (OPR) and competitiveness, which were regarded as endogenous variables. The analysis was carried out with the help of structural equation modelling considering natural logarithm of manpower as a control variable. Few major findings are mentioned. EMP does not have any significant association with OPR, nor does it result in competitiveness. However, when jointly mediated through both EPR and OPR, EMP leads to competitiveness. SPC has significant negative association with competitiveness, when only direct relationship is considered. However, indirect relationship between SPC and competitiveness shows significant positive association when mediated through CSP. The resultant total effect between SPC and competitiveness turns out to be insignificant. Further, OPR fully mediates the relationship between OP and competitiveness. Managerial implications of the findings are discussed.  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