全文获取类型
收费全文 | 1642篇 |
免费 | 71篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
综合类 | 17篇 |
化学工业 | 404篇 |
金属工艺 | 37篇 |
机械仪表 | 23篇 |
建筑科学 | 68篇 |
矿业工程 | 5篇 |
能源动力 | 36篇 |
轻工业 | 204篇 |
水利工程 | 7篇 |
石油天然气 | 1篇 |
无线电 | 176篇 |
一般工业技术 | 224篇 |
冶金工业 | 277篇 |
原子能技术 | 23篇 |
自动化技术 | 200篇 |
出版年
2023年 | 20篇 |
2022年 | 45篇 |
2021年 | 51篇 |
2020年 | 34篇 |
2019年 | 31篇 |
2018年 | 39篇 |
2017年 | 42篇 |
2016年 | 41篇 |
2015年 | 38篇 |
2014年 | 49篇 |
2013年 | 83篇 |
2012年 | 58篇 |
2011年 | 90篇 |
2010年 | 58篇 |
2009年 | 65篇 |
2008年 | 65篇 |
2007年 | 58篇 |
2006年 | 55篇 |
2005年 | 64篇 |
2004年 | 44篇 |
2003年 | 28篇 |
2002年 | 37篇 |
2001年 | 26篇 |
2000年 | 24篇 |
1999年 | 33篇 |
1998年 | 83篇 |
1997年 | 53篇 |
1996年 | 46篇 |
1995年 | 29篇 |
1994年 | 36篇 |
1993年 | 37篇 |
1992年 | 6篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 16篇 |
1976年 | 17篇 |
1974年 | 8篇 |
1940年 | 6篇 |
排序方式: 共有1714条查询结果,搜索用时 15 毫秒
61.
T. Zimmermann G. W. Fischer B. Olk M. Findeisen 《Advanced Synthesis \u0026amp; Catalysis》1989,331(2):306-318
Pyrylium Compounds. 42. Benzocycloalkenones and Dihydro-2H,7H-1-benzopyranones from 2,4,6-Triarylpyrylium Salts and Cycloalkane-1,2-diones 2,4,6-Triarylpyrylium salts 1 react with cycloalkane-1,2-diones 2 in the presence of an appropriate condensing agent to yield benzocycloalkenones 3 . Thus, sodium acetate and cyclo-hexane-1,2-dione ( 2a ) lead to the dihydro-2H-naphthalenones 3a – i , whereas with cycloheptane-1,2-dione ( 2b ) and piperidine acetate, triethylamine or sodium acetate the tetrahydro-5H-benzo-cyclohepten-5-ones 3j – r are formed. As shown for the example 3a, j → 4a, b , benzocycloalkenones of type 3 can be converted into phthalazines 4 on heating with hydrazine in ethanol. By reaction of the dione 2a and an equimolar mixture of triethylamine and acetic acid or morpholine acetate with the salts 1 5,6-dihydro-2H,7H-1-benzopyran-8-ones 5 are obtained as a result of a new type of ring transformation. The pyrans 5 can be cleaved with perchloric acid in ethanol to 5,6,7,8-tetrahydro-8-oxo-1-benzopyrylium perchlorates 6 . If the pyrans 5 are heated with sodium acetate in ethanol, a conversion to benzocycloalkenones 3 is achieved (cf. 5a → 3a ). The structure of the new compounds was established by spectroscopic methods. 相似文献
62.
汽车钢板回收冶炼过程中涂覆油漆的裂变行为 总被引:4,自引:0,他引:4
采用单光子离子化/共振增强的多光子离子化-飞行时间质谱法(SPI/REMPI-TOFMS)研究了在汽车钢板的回收冶炼过程中,涂覆油漆的裂变行为.在模拟实验装置中,在线跟踪监测了裂解炉气中的有机裂变产物的演变过程.发现与其它有机材料不同,汽车钢板的涂覆油漆不仅在合成空气中,而且在氮气中也产生酚类有机污染物.从300 ℃到1 190 ℃都有多环芳烃(PAHs)产生,但在700~800 ℃时,产生的数量最多,在1 000~1 190 ℃,趋于完全燃烧. 相似文献
63.
64.
T. Zimmermann G. W. Fischer J. Teller H. Dehne B. Olk 《Advanced Synthesis \u0026amp; Catalysis》1990,332(5):723-730
Substituted N,N′-Bis(thiazol-2-yl)-diaminoalkanes from α-Thiocyanato-acetophenones and N,N′-Dialkyl-diaminoalkanes α-Thiocyanato-acetophenones 1 react with N,N′-dialkyl-diaminoalkanes 2 in the presence of an appropriate weak acid (acetic acid, propionic acid, benzoic acid) to give the hitherto unknown N,N′-dialkyl-N,N′-bis(4-aryl-thiazol-2-yl)-diaminoalkanes 3 . As reaction medium aliphatic alcohols (ethanol, methanol), halogenated hydrocarbons (methylene chloride, chloroform, carbon tetrachloride) or dipolar-aprotic solvents (acetonitrile, dimethylformamide) can be used. - I.r., u.v., n.m.r. and mass spectroscopic data of the novel bisthiazoles 3 are reported. 相似文献
65.
Jagadeesh Nagendra Manda Milica Markovic Prof. Ellen M. Zimmermann Prof. Shimon Ben-Shabat Prof. Arik Dahan Prof. Aaron Aponick 《ChemMedChem》2020,15(17):1639-1644
Novel phospholipid (PL)-cyclosporine conjugates were prepared and studied as potential prodrugs for inflammatory bowel disease (IBD). Our approach relies on phospholipase A2 (PLA2), which is overexpressed in the inflamed intestinal tissues, as the prodrug activator to potentially release cyclosporine at the site of inflammation. PL-cyclosporine prodrug conjugates with methylene linkers of various lengths between the sn-2 position of the PL and cyclosporine were synthesized and evaluated for in vitro activation. Surprisingly, despite previous work indicating that conjugates with six methylene linkers between the lipid and drug would suffer rapid enzymatic hydrolysis, with cyclosporine this was not observed. However, compounds with longer linkers (n=10, 12 methylene units) display complete release of the drug by PLA2-catalyzed hydrolysis, thus demonstrating the importance and profound impact of structural fine-tuning. This study represents a proof-of-concept for our hypothesis and a first step towards a truly targeted IBD treatment with cyclosporine that could be administered throughout the GI tract. 相似文献
66.
67.
Glycation of the Major Milk Allergen β‐Lactoglobulin Changes Its Allergenicity by Alterations in Cellular Uptake and Degradation 下载免费PDF全文
Marija Perusko Manon van Roest Dragana Stanic‐Vucinic Peter J. Simons Raymond H. H. Pieters Tanja Cirkovic Velickovic Joost J. Smit 《Molecular nutrition & food research》2018,62(17)
1 Scope
During food processing, the Maillard reaction (МR) may occur, resulting in the formation of glycated proteins. Glycated proteins are of particular importance in food allergies because glycation may influence interactions with the immune system. This study compared native and extensively glycated milk allergen β‐lactoglobulin (BLG), in their interactions with cells crucially involved in allergy.2 Methods and results
BLG was glycated in MR and characterized. Native and glycated BLG were tested in experiments of epithelial transport, uptake and degradation by DCs, T‐cell cytokine responses, and basophil cell degranulation using ELISA and flow cytometry. Glycation of BLG induced partial unfolding and reduced its intestinal epithelial transfer over a Caco‐2 monolayer. Uptake of glycated BLG by bone marrow–derived dendritic cells (BMDC) was increased, although both BLG forms entered BMDC via the same mechanism, receptor‐mediated endocytosis. Once inside the BMDC, glycated BLG was degraded faster, which might have led to observed lower cytokine production in BMDC/CD4+ T‐cells coculture. Finally, glycated BLG was less efficient in induction of degranulation of BLG‐specific IgE sensitized basophil cells.3 Conclusions
This study suggests that glycation of BLG by MR significantly alters its fate in processes involved in immunogenicity and allergenicity, pointing out the importance of food processing in food allergy. 相似文献68.
Green tea seems to have a positive impact on health due to the therein-found flavanols. The amounts of these substances depend on tea preparation. In this paper, the influence of steeping time (3–7 min) and temperature (70–100 °C) on the content of the main flavanols in green tea (epicatechin EC, epicatechin gallate ECg, epigallocatechin EGC, and epigallocatechin gallate EGCg) is presented. Furthermore, additives (phosphate buffers, ascorbic acid in different amounts, and citric acid) are used to investigate the influence of pH, antioxidative, and chelating agents, simulating the addition of lemon juice or pure vitamin C. 相似文献
69.
Benno F. Zimmermann Ursula Woelwer-Rieck Menelaos Papagiannopoulos 《Food Analytical Methods》2012,5(2):266-271
Stevia rebaudiana Bertoni contains several steviol glycosides with sweet flavour. They all are sweeter than sucrose (up to factor 450). The
various steviol glycosides are difficult to separate by reversed-phase chromatography. In this paper, five different hydrophilic
liquid interaction chromatography columns are characterized using isocratic elution (5–20% water in acetonitrile with buffer
or formic acid). Separation of the steviol glycosides is possible with all but one of the tested columns, but the robustness
of the separation against changes of buffer concentration and percentage of water differ. Aqueous percentage and ion strength
of the eluent are the main factors to be optimized in method development. 相似文献
70.
James W. Zimmermann Gregory E. Hilmas William G. Fahrenholtz Ralph B. Dinwiddie Wallace D. Porter Hsin Wang 《Journal of the American Ceramic Society》2008,91(5):1405-1411
Thermophysical properties were investigated for zirconium diboride (ZrB2 ) and ZrB2 –30 vol% silicon carbide (SiC) ceramics. Thermal conductivities were calculated from measured thermal diffusivities, heat capacities, and densities. The thermal conductivity of ZrB2 increased from 56 W (m K)−1 at room temperature to 67 W (m K)−1 at 1675 K, whereas the thermal conductivity of ZrB2 –SiC decreased from 62 to 56 W (m K)−1 over the same temperature range. Electron and phonon contributions to thermal conductivity were determined using electrical resistivity measurements and were used, along with grain size models, to explain the observed trends. The results are compared with previously reported thermal conductivities for ZrB2 and ZrB2 –SiC. 相似文献