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   3346篇
  免费   485篇
  国内免费   53篇
电工技术   4篇
综合类   39篇
化学工业   1065篇
金属工艺   46篇
机械仪表   44篇
建筑科学   13篇
能源动力   23篇
轻工业   2263篇
水利工程   3篇
石油天然气   8篇
无线电   51篇
一般工业技术   272篇
冶金工业   24篇
原子能技术   4篇
自动化技术   25篇
  2024年   40篇
  2023年   147篇
  2022年   311篇
  2021年   317篇
  2020年   196篇
  2019年   220篇
  2018年   197篇
  2017年   182篇
  2016年   175篇
  2015年   155篇
  2014年   156篇
  2013年   196篇
  2012年   165篇
  2011年   149篇
  2010年   116篇
  2009年   100篇
  2008年   101篇
  2007年   86篇
  2006年   104篇
  2005年   109篇
  2004年   76篇
  2003年   83篇
  2002年   61篇
  2001年   54篇
  2000年   45篇
  1999年   40篇
  1998年   54篇
  1997年   37篇
  1996年   31篇
  1995年   30篇
  1994年   27篇
  1993年   29篇
  1992年   22篇
  1991年   18篇
  1990年   6篇
  1989年   9篇
  1988年   3篇
  1986年   5篇
  1985年   9篇
  1984年   4篇
  1983年   1篇
  1982年   2篇
  1981年   4篇
  1980年   4篇
  1979年   3篇
  1978年   4篇
  1976年   1篇
排序方式: 共有3884条查询结果,搜索用时 31 毫秒
91.
The chemical, amino acid and fatty acid compositions of Sterculia urens seeds are reported. The cotyledons were found to be rich in protein (30.88%) and lipids (39.2%). The major amino acids in defatted Sterculia urens cotyledon flour (DSCF) were determined as glutamic acid, arginine and aspartic acid. Cysteine, methionine, tyrosine and histidine were observed in minor quantities. The ratio of essential to non-essential amino acids was observed to be 0.45. Among the essential amino acids, isoleucine was found to be higher than the reported FAO/WHO requirements. The GC-FID and GC–MS analysis revealed that the major fatty acids of the total lipid were stearic acid (31.72%), linoleic acid (28.83%) and palmitic acid (26.79%). Eicosadienoic acid (4.98%) and eicosatrienoic acid (2.96%) were also found in the total lipid.  相似文献   
92.
Small-molecule amphiphilic species such as many drug molecules frequently exhibit low-to-negligible aqueous solubility, and generally have no identified transport proteins assisting their distribution, yet are able to rapidly penetrate significant distances into patient tissue and even cross the blood–brain barrier. Previous work has identified a mechanism of translocation driven by acid-catalysed lipid hydrolysis of biological membranes, a process which is catalysed by the presence of cationic amphiphilic drug molecules. In this study, the interactions of raclopride, a model amphiphilic drug, were investigated with mixtures of biologically relevant lipids across a range of compositions, revealing the influence of the chain-melting temperature of the lipids upon the rate of acyl hydrolysis.  相似文献   
93.
Diterpenoidal anti-cancer drug andrographolide (AD) was encapsulated into solid lipid nanoparticle (SLN) because of poor aqueous solubility and high lipophilicity. AD-SLNs were prepared by solvent injection method and characterized for droplet size, surface morphology, zeta potential, etc. In vitro drug release was carried out by dialysis-membrane method. A pharmacokinetic study was performed by UPLC/Q-TOF-MS method to determine the maximum plasma concentration (Cmax), area under the curve (AUC), etc. There was an improvement in Cmax and AUC of AD-SLNs when compared with AD, thereby enhancing the bioavailability of AD. The tmax was increased than that of AD suspension, indicating the sustained release pattern of AD-SLNs. The antitumor activity was carried out on Balb/c mice showing better results with AD-SLNs as compared to AD. Thus, the AD-loaded SLNs would be useful for delivering poorly water-soluble AD with enhanced bioavailability and improved antitumor activity.  相似文献   
94.
95.
Purpose: A novel brain targeting drug delivery system based on OX26 antibody conjugation on PEGylated cationic solid lipid nanoparticles (OX26-PEG-CSLN) was prepared.

Methods: The Baicalin-loaded PEGylated cationic solid lipid nanoparticles modified by OX26 antibody (OX26-PEG-CSLN) were prepared by emulsion evaporation–solidification at low temperature method. The immune-gold labeled OX26-PEG-CSLN was visualized by transmission electron microscopy. The mean diameter and zeta potential of OX26-PEG-CSLN, PEG-CSLN and CSLN were determined using a Zetasizer. The entrapment efficiency of OX26-PEG-CSLN, PEG-CSLN and CSLN was determined by ultrafiltration centrifugation method. And the solid-state characterization of OX26-PEG-CSLN and CSLN were analyzed by X-ray. Pharmacokinetics studies were conducted by in vivo microdialysis in rat cerebrospinal fluid.

Results: The results showed that the OX26-PEG-CSLN, PEG-CSLN and CSLN had average diameters of 47.68?±?1.65, 27.20?±?1.70 and 33.89?±?5.74?nm, Zeta potentials of ?0.533?±?0.115?mV, 11.200?±?0.500?mV and 11.080?±?1.170?mV and entrapment efficiencies of 83.03?±?0.01%, 92.90?±?3.50% and 97.83?±?0.19%, respectively. In the pharmacokinetics studies, the AUC value of OX26-PEG-CSLN was11.08-fold higher than that of the Baicalin solution (SOL) (p?p?>?0.05); the Cmax value of OX26-PEG-CSLN was 7.88-fold higher than that of SOL (p?p?Conclusion: These results demonstrated OX26-PEG-CSLN could be a promising carrier to deliver drugs across the BBB for the treatment of brain diseases.  相似文献   
96.
为了增强运载辅酶Q10的纳米结构脂质载体(CoQ10-NLC)的透皮效果,采用促渗剂——壳聚糖季铵盐(QCS)对CoQ10-NLC进行了表面修饰,并结合QCS分子链的自聚集行为,明确了壳聚糖季铵盐修饰的包载辅酶Q10的纳米脂质体(QCS-CoQ10-NLC)的形成机制,得到了粒径在500 nm左右的脂质载体。进一步通过体外透皮实验,考察了QCS-CoQ10-NLC的透皮吸收效果。结果显示,经质量分数0.5%的QCS修饰后,脂质载体可将CoQ10在皮肤中的渗透总量由1.36μg/cm~2显著增加至5.14μg/cm~2。  相似文献   
97.
Three walnut (Juglans regia L.) drying methods (sun drying, direct oven drying, and intermittent oven drying) were employed, and the consequent changes in lipid oxidation attributes, such as acid value (AV), peroxide value (POV), saponification value (SV), fatty acid composition, and antioxidant activity [including reducing power, superoxide anion scavenging activity, 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activity (DPPH), lipoxygenase (LOX) activity, total phenols content (TPC), and total flavonoids content (TFC)] were investigated in this study. Sun drying resulted in the highest AV, POV, and SV, followed by direct oven drying and intermittent oven drying. Antioxidant activities and related compounds, TPC and TFC, were initially increased and then declined during drying, and a significant correlation was found between antioxidant activity and TPC and TFC. The LOX activities of all samples showed an increasing trend, although those of the sun-dried samples were the lowest. The walnuts dried with the intermittent oven drying method contained more linoleic acid than those dried by direct oven drying. Overall, intermittent oven drying appears to be a promising strategy for fresh walnut drying.  相似文献   
98.
Lipid metabolism, inflammation, oxidative stress and endothelial function play important roles in the pathogenesis of cardiovascular disease (CVD), which may be affected by an imbalance in the n‐6/n‐3 polyunsaturated fatty acid (PUFA) ratio. This study aimed to investigate the effects of the n‐6/n‐3 PUFA ratio on these cardiovascular risk factors in rats fed a high‐fat diet using plant oils as the main n‐3 PUFA source. The 1:1 and 5:1 ratio groups had significantly decreased serum levels of total cholesterol, low‐density lipoprotein cholesterol, and proinflammatory cytokines compared with the 20:1 group (p < 0.05). Additionally, the 20:1 group had significantly increased serum levels of E‐Selectin, von Willebrand factor (vWF), and numerous markers of oxidative stress compared with the other groups (p < 0.05). The 1:1 group had a significantly decreased lipid peroxide level compared with the other groups (p < 0.05). Serum levels of malondialdehyde, reactive oxygen species and vWF tended to increase with n‐6/n‐3 PUFA ratios increasing from 5:1 to 20:1. We demonstrated that low n‐6/n‐3 PUFA ratio (1:1 and 5:1) had a beneficial effect on cardiovascular risk factors by enhancing favorable lipid profiles, having anti‐inflammatory and anti‐oxidative stress effects, and improving endothelial function. A high n‐6/n‐3 PUFA ratio (20:1) had adverse effects. Our results indicated that low n‐6/n‐3 PUFA ratios exerted beneficial cardiovascular effects, suggesting that plant oils could be used as a source of n‐3 fatty acids to prevent CVD. They also suggested that we should be aware of possible adverse effects from excessive n‐3 PUFA.  相似文献   
99.
100.
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