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   194605篇
  免费   3232篇
  国内免费   1011篇
电工技术   3728篇
综合类   644篇
化学工业   31066篇
金属工艺   8245篇
机械仪表   5771篇
建筑科学   5205篇
矿业工程   1050篇
能源动力   5180篇
轻工业   18183篇
水利工程   1916篇
石油天然气   3294篇
武器工业   29篇
无线电   21881篇
一般工业技术   35723篇
冶金工业   36074篇
原子能技术   4428篇
自动化技术   16431篇
  2021年   1745篇
  2019年   1560篇
  2018年   2441篇
  2017年   2409篇
  2016年   2561篇
  2015年   1894篇
  2014年   3213篇
  2013年   8678篇
  2012年   5278篇
  2011年   7217篇
  2010年   5720篇
  2009年   6607篇
  2008年   6586篇
  2007年   6545篇
  2006年   5626篇
  2005年   5212篇
  2004年   5095篇
  2003年   4982篇
  2002年   5203篇
  2001年   5076篇
  2000年   4459篇
  1999年   4504篇
  1998年   11408篇
  1997年   8091篇
  1996年   6155篇
  1995年   4611篇
  1994年   3873篇
  1993年   3862篇
  1992年   2761篇
  1991年   2659篇
  1990年   2540篇
  1989年   2552篇
  1988年   2487篇
  1987年   2215篇
  1986年   2164篇
  1985年   2492篇
  1984年   2258篇
  1983年   2090篇
  1982年   1954篇
  1981年   2028篇
  1980年   1882篇
  1979年   1864篇
  1978年   1819篇
  1977年   2194篇
  1976年   2844篇
  1975年   1604篇
  1974年   1572篇
  1973年   1652篇
  1972年   1379篇
  1971年   1289篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
Excessive energy intake may evoke complex biochemical processes characterized by inflammation, oxidative stress, and impairment of mitochondrial function that represent the main factors underlying noncommunicable diseases. Because cow milk is widely used for human nutrition and in food industry processing, the nutritional quality of milk is of special interest with respect to human health. In our study, we analyzed milk produced by dairy cows fed a diet characterized by a high forage:concentrate ratio (high forage milk, HFM). In view of the low n-6:n-3 ratio and high content of conjugated linoleic acid of HFM, we studied the effects of this milk on lipid metabolism, inflammation, mitochondrial function, and oxidative stress in a rat model. To this end, we supplemented for 4 wk the diet of male Wistar rats with HFM and with an isocaloric amount (82 kJ, 22 mL/d) of milk obtained from cows fed a diet with low forage:concentrate ratio, and analyzed the metabolic parameters of the animals. Our results indicate that HFM may positively affect lipid metabolism, leptin:adiponectin ratio, inflammation, mitochondrial function, and oxidative stress, providing the first evidence of the beneficial effects of HFM on rat metabolism.  相似文献   
62.
63.
64.
65.
66.
67.
68.
Enhancement of the dissolution rate of the poorly water-soluble hypoglycemic agent, gliclazide, by the aid of lyophilization was investigated. Mannitol, sodium lauryl sulfate (SLS) and polyvinyl pyrrolidone (PVP-k-30) were employed in different weight ratios (43%, 56% and 64% w/w, respectively) as water-soluble excipients in the formulation. Lyophilized systems were found to exhibit extremely higher in vitro dissolution rate compared to the unprocessed drug powder. Solid state characterization of the lyophilized systems using X-ray powder diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry techniques revealed that dissolution enhancement was attributable to transformation of gliclazide from the crystalline to an amorphous state in the solid dispersion formed during the lyophilization process. The gastrointestinal absorption and hypoglycemic effect of the lyophilized gliclazide/SLS system were investigated following oral administration to Albino rabbits. Cmax and area under the plasma concentration–time curve of gliclazide (AUC0–12) after administration of the lyophilized formulations were significantly higher than those obtained after administration of the unprocessed gliclazide.  相似文献   
69.
The high cost and potential toxicity of biodegradable polymers like poly(lactic‐co‐glycolic)acid (PLGA) has increased the interest in natural and modified biopolymers as bioactive carriers. This study characterized the physical stability (water sorption and state transition behavior) of selected starch and proteins: octenyl succinate–modified depolymerized waxy corn starch (DWxCn), waxy rice starch (DWxRc), phytoglycogen, whey protein concentrate (80%, WPC), whey protein isolate (WPI), and α‐lactalbumin (α‐L) to determine their potential as carriers of bioactive compounds under different environmental conditions. After enzyme modification and particle size characterization, glass transition temperature and moisture isotherms were used to characterize the systems. DWxCn and DWxRc had increased water sorption compared to native starch. The level of octenyl succinate anhydrate (OSA) modification (3% and 7%) did not reduce the water sorption of the DWxCn and phytoglycogen samples. The Guggenheim–Andersen–de Boer model indicated that native waxy corn had significantly (P < 0.05) higher water monolayer capacity followed by 3%‐OSA‐modified DWxCn, WPI, 3%‐OSA‐modified DWxRc, α‐L, and native phytoglycogen. WPC had significantly lower water monolayer capacity. All Tg values matched with the solid‐like appearance of the biopolymers. Native polysaccharides and whey proteins had higher glass transition temperature (Tg) values. On the other hand, depolymerized waxy starches at 7%‐OSA modification had a “melted” appearance when exposed to environments with high relative humidity (above 70%) after 10 days at 23 °C. The use of depolymerized and OSA‐modified polysaccharides blended with proteins created more stable blends of biopolymers. Hence, this biopolymer would be suitable for materials exposed to high humidity environments in food applications.  相似文献   
70.
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