全文获取类型
收费全文 | 3109篇 |
免费 | 149篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 37篇 |
综合类 | 16篇 |
化学工业 | 942篇 |
金属工艺 | 62篇 |
机械仪表 | 40篇 |
建筑科学 | 120篇 |
矿业工程 | 4篇 |
能源动力 | 56篇 |
轻工业 | 312篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 188篇 |
一般工业技术 | 675篇 |
冶金工业 | 337篇 |
原子能技术 | 25篇 |
自动化技术 | 442篇 |
出版年
2023年 | 39篇 |
2022年 | 19篇 |
2021年 | 59篇 |
2020年 | 44篇 |
2019年 | 63篇 |
2018年 | 49篇 |
2017年 | 54篇 |
2016年 | 89篇 |
2015年 | 89篇 |
2014年 | 101篇 |
2013年 | 167篇 |
2012年 | 171篇 |
2011年 | 207篇 |
2010年 | 152篇 |
2009年 | 163篇 |
2008年 | 160篇 |
2007年 | 142篇 |
2006年 | 120篇 |
2005年 | 118篇 |
2004年 | 83篇 |
2003年 | 75篇 |
2002年 | 57篇 |
2001年 | 50篇 |
2000年 | 39篇 |
1999年 | 56篇 |
1998年 | 70篇 |
1997年 | 64篇 |
1996年 | 45篇 |
1995年 | 49篇 |
1994年 | 51篇 |
1993年 | 38篇 |
1992年 | 36篇 |
1991年 | 45篇 |
1990年 | 26篇 |
1989年 | 34篇 |
1988年 | 35篇 |
1987年 | 33篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 32篇 |
1983年 | 17篇 |
1981年 | 30篇 |
1980年 | 21篇 |
1979年 | 22篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1976年 | 28篇 |
1975年 | 18篇 |
1974年 | 15篇 |
1973年 | 14篇 |
排序方式: 共有3261条查询结果,搜索用时 15 毫秒
1.
Keran Su Kim Huey Ee Jingcan Sun Shao Quan Liu Benjamin Lassabliere Ulrich Feiter Yunle Huang Rui Min Vivian Goh Aileen Pua Bin Yu 《International Journal of Food Science & Technology》2022,57(3):1666-1678
The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min−1 of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study. 相似文献
2.
Michael Lommel Vera Froese Moritz Sieber Marvin Jentzsch Tim Bierewirtz Ümit Hasirci Tim Rese Josef Seefeldt Sebastian Schimek Ulrich Kertzscher Christian Oliver Paschereit 《Indoor air》2021,31(6):1860-1873
The SARS-CoV-2 pandemic has created a great demand for a better understanding of the spread of viruses in indoor environments. A novel measurement system consisting of one portable aerosol-emitting mannequin (emitter) and a number of portable aerosol-absorbing mannequins (recipients) was developed that can measure the spread of aerosols and droplets that potentially contain infectious viruses. The emission of the virus from a human is simulated by using tracer particles solved in water. The recipients inhale the aerosols and droplets and quantify the level of solved tracer particles in their artificial lungs simultaneously over time. The mobile system can be arranged in a large variety of spreading scenarios in indoor environments and allows for quantification of the infection probability due to airborne virus spreading. This study shows the accuracy of the new measurement system and its ability to compare aerosol reduction measures such as regular ventilation or the use of a room air purifier. 相似文献
3.
Shamila Vibhushan Manuela Bratti Juan Eduardo Montero-Hernndez Alaa El Ghoneimi Marc Benhamou Nicolas Charles Eric Daugas Ulrich Blank 《International journal of molecular sciences》2021,22(1)
A sizable part (~2%) of the human genome encodes for proteases. They are involved in many physiological processes, such as development, reproduction and inflammation, but also play a role in pathology. Mast cells (MC) contain a variety of MC specific proteases, the expression of which may differ between various MC subtypes. Amongst these proteases, chymase represents up to 25% of the total proteins in the MC and is released from cytoplasmic granules upon activation. Once secreted, it cleaves the targets in the local tissue environment, but may also act in lymph nodes infiltrated by MC, or systemically, when reaching the circulation during an inflammatory response. MC have been recognized as important components in the development of kidney disease. Based on this observation, MC chymase has gained interest following the discovery that it contributes to the angiotensin-converting enzyme’s independent generation of angiotensin II, an important inflammatory mediator in the development of kidney disease. Hence, progress regarding its role has been made based on studies using inhibitors but also on mice deficient in MC protease 4 (mMCP-4), the functional murine counterpart of human chymase. In this review, we discuss the role and actions of chymase in kidney disease. While initially believed to contribute to pathogenesis, the accumulated data favor a more subtle view, indicating that chymase may also have beneficial actions. 相似文献
4.
Aamer Saeed Muhammad Naeem Mustafa Muhammad Zain-ul-Abideen Ghulam Shabir Mauricio F. Erben Ulrich Flörke 《Journal of Sulfur Chemistry》2019,40(3):312-350
1-(acyl/aroyl)-3-(substituted)thioureas are exciting structures in the fields of organic synthesis, material sciences, and biomedical research. Of particular significance is the fact that acyl thiourea derivatives have been demonstrated to be highly exceptional ligands and their coordination compounds have extensively been investigated in the synthesis of pharmaceuticals and agrochemical ingredients. Moreover, these structural motifs are enjoying the prestigious status as versatile synthons in heterocyclic syntheses. Therefore, the progress to introduce functionalization on the backbone of 1-(acyl/aroyl)-3-(substituted)thioureas is highly desirable. This account summarizes our efforts to capture recent documented achievements by various research groups. 相似文献
5.
6.
7.
Due to increasing energy requirements for buildings, thermal insulation composite systems (TICS) have been used to insulate building facades since the 1970s. In view of the longevity of these composite materials, there has been an increased amount of TICS waste in recent years. Since there is no current recycling concept for these systems, an enormous resource efficiency potential remains unused. Due to the complexity of composite materials this study focuses on the pretreatment and discusses different processing steps in detail. 相似文献
8.
The curing of wood adhesives has so far been evaluated on a basis of parameters, which offer process optimization only to a small degree. However, the curing becomes analyzable in detail by using oscillation measurements and a test setup adapted to the bonding process. With time sweep measurements, the adhesion process can be divided into characteristic ranges of molecular and structural processes. This method is presented and analyzed using a polyurethane prepolymer for joining wood-based materials. 相似文献
9.
Makrina A. Chairopoulou Fabian Kratzer Roland Gross Michael Herrmann Ulrich Teipel 《化学工程与技术》2020,43(5):904-912
Thermogravimetric analysis of a coccolith-containing biogenic broth showed a three-step degradation process. According to this system behavior, the biogenic broth was heated to specific temperatures and characterized in terms of its morphology, surface chemistry, and crystallinity. The elemental and organic composition of the treated samples was also evaluated and compared to the reference material. The presented results were acquired in an effort to exploit pretreatment scenarios for such a biogenic system that would improve and support a separation process. 相似文献
10.
The impact of total solid (TS) content in combination with the feed rate and air inlet temperature on the survival of Lactobacillus paracasei ssp. paracasei F19 after spray drying in a skim milk matrix has been investigated and correlated with the capsule size. Depending on the experimental conditions, the survival rates ranged from 64 to 0.2%. The higher the air inlet temperature, the lower was the survival rate and an inversely correlation between the TS content and particle size has been determined. These results clearly indicate that process stress analyses and product-related characteristics must not be regarded separately. 相似文献