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   276212篇
  免费   4040篇
  国内免费   835篇
电工技术   5311篇
综合类   342篇
化学工业   39389篇
金属工艺   10447篇
机械仪表   8770篇
建筑科学   6939篇
矿业工程   1108篇
能源动力   6788篇
轻工业   24586篇
水利工程   2785篇
石油天然气   3932篇
武器工业   68篇
无线电   36086篇
一般工业技术   52117篇
冶金工业   51475篇
原子能技术   5521篇
自动化技术   25423篇
  2021年   2269篇
  2019年   2222篇
  2018年   3713篇
  2017年   3757篇
  2016年   3974篇
  2015年   2551篇
  2014年   4392篇
  2013年   11882篇
  2012年   7141篇
  2011年   9694篇
  2010年   7559篇
  2009年   8438篇
  2008年   9272篇
  2007年   9190篇
  2006年   8294篇
  2005年   7604篇
  2004年   7315篇
  2003年   7148篇
  2002年   6752篇
  2001年   6769篇
  2000年   6434篇
  1999年   6645篇
  1998年   15994篇
  1997年   11340篇
  1996年   8829篇
  1995年   6849篇
  1994年   6135篇
  1993年   5983篇
  1992年   4730篇
  1991年   4391篇
  1990年   4216篇
  1989年   3949篇
  1988年   3796篇
  1987年   3287篇
  1986年   3187篇
  1985年   3775篇
  1984年   3502篇
  1983年   3120篇
  1982年   2945篇
  1981年   3050篇
  1980年   2843篇
  1979年   2734篇
  1978年   2568篇
  1977年   3072篇
  1976年   3696篇
  1975年   2381篇
  1974年   2377篇
  1973年   2362篇
  1972年   1877篇
  1971年   1770篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Palmitoleic acid has been classified as an insulin-sensitizing lipokine, but evidence for this from human studies has been inconsistent. We hypothesized that this is related to either the types of samples or conditions under which samples are collected. We measured plasma palmitoleic acid and total free fatty acids (FFA) using ultra-performance liquid chromatography in blood samples collected from 34 adults under a variety of conditions. We collected duplicate samples of adipose (n = 10), FFA (n = 9), and very low density lipoprotein triacylglycerol (VLDL-TAG) (n = 7) to measure the palmitoleic acid as a percentage of total fatty acids. We tested whether the percentage of palmitoleic acid was correlated with insulin resistance, as measured by homeostatic model of insulin resistance (HOMA-IR). Adipose stearoyl-coenzyme A desaturase 1 (SCD-1) protein was measured by capillary Western blotting. FFA-palmitoleic acid percentage increased as a function of total FFA and was greater (p < 0.005) in females than males. Adipose palmitoleic acid percentage was greater in females than males (p < 0.001), as was adipose SCD-1. Palmitoleic acid was greater in femoral fat than in abdominal fat in both females and males (p < 0.001), and correlated positively with HOMA-IR only in females. The test–retest reliability values for percentage palmitoleic acid were 7 ± 10% for adipose, 24 ± 26% for VLDL, and 53 ± 31% for FFA. Because FFA-palmitoleic acid percentage varies as a function of total FFA, investigators should re-evaluate how palmitoleic acid data is presented. The positive relationship between adipose palmitoleic acid and HOMA-IR in females suggests that it is not a potent insulin-sensitizing lipokine in humans.  相似文献   
102.
103.
104.
105.
Processing lithium-ion battery (LIB) electrode dispersions with water as the solvent during primary drying offers many advantages over N-methylpyrrolidone (NMP). An in-depth analysis of the comparative drying costs of LIB electrodes is discussed for both NMP- and water-based dispersion processing in terms of battery pack $/kWh. Electrode coating manufacturing and capital equipment cost savings are compared for water vs. conventional NMP organic solvent processing. A major finding of this work is that the total electrode manufacturing costs, whether water- or NMP-based, contribute about 8–9% of the total pack cost. However, it was found that up to a 2?×?reduction in electrode processing (drying and solvent recovery) cost can be expected along with a $3–6?M savings in associated plant capital equipment (for a plant producing 100,000 10-kWh Plug-in Hybrid Electric Vehicle (PHEV) batteries) using water as the electrode solvent. This paper shows a different perspective in that the most important benefits of aqueous electrode processing actually revolve around capital equipment savings and environmental stewardship and not processing cost savings.  相似文献   
106.
The molten salt method was used to synthesise the MAX phase compounds Ti2AlC and Ti3AlC2 from elemental powders. Between 900–1000?°C, Ti2AlC was formed alongside ancillary phases TiC and TiAl, which decreased in abundance with increasing synthesis temperature. Changing the stoichiometry and increasing the synthesis temperature to 1300?°C resulted in formation of Ti3AlC2 alongside Ti2AlC and TiC. The type of salt flux used had little effect on the product formation. The reaction pathway for Ti2AlC was determined to be the initial formation of TiC1-x templating on the graphite and titanium aluminides.  相似文献   
107.
A novel glass-ceramic material based on albite type Na-rich feldspar has been synthesized by conventional ceramic process. High crystallinity, >94%?Vol.% is obtained by fast sintering which allows energy saving processing. Albite is the main crystalline phase and tetragonal SiO2 is a secondary phase. Electrical properties were examined by complex impedance, DC measurements, and dielectric breakdown test. Dielectric characterization shows a non-Debye type dielectric behavior with low dielectric constant, 4.6 at 1?MHz, low dielectric losses, (~10?3 at 1?MHz, and a large dielectric strength, ~60?kV/mm), that it is the largest value reported in ceramic insulators. Those dielectric properties are attained by the low glassy phase content in the samples and their unique micro-nanostructure. All these properties make this novel material a very promising candidate in the market of ceramic electrical insulator, highlighting for high-voltage applications.  相似文献   
108.
Russian Engineering Research - The theoretically possible reconfigurable parallel mechanisms are classified, in terms of the layout of guides on the base. Formulas are derived for the...  相似文献   
109.
110.
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