全文获取类型
收费全文 | 1544篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 284篇 |
金属工艺 | 35篇 |
机械仪表 | 24篇 |
建筑科学 | 53篇 |
矿业工程 | 10篇 |
能源动力 | 31篇 |
轻工业 | 155篇 |
水利工程 | 11篇 |
石油天然气 | 3篇 |
无线电 | 146篇 |
一般工业技术 | 217篇 |
冶金工业 | 418篇 |
原子能技术 | 9篇 |
自动化技术 | 172篇 |
出版年
2022年 | 16篇 |
2021年 | 31篇 |
2020年 | 24篇 |
2019年 | 16篇 |
2018年 | 36篇 |
2017年 | 19篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 28篇 |
2013年 | 67篇 |
2012年 | 34篇 |
2011年 | 67篇 |
2010年 | 44篇 |
2009年 | 48篇 |
2008年 | 57篇 |
2007年 | 46篇 |
2006年 | 55篇 |
2005年 | 43篇 |
2004年 | 29篇 |
2003年 | 29篇 |
2002年 | 43篇 |
2001年 | 31篇 |
2000年 | 17篇 |
1999年 | 30篇 |
1998年 | 95篇 |
1997年 | 57篇 |
1996年 | 52篇 |
1995年 | 31篇 |
1994年 | 35篇 |
1993年 | 43篇 |
1992年 | 27篇 |
1991年 | 22篇 |
1990年 | 33篇 |
1989年 | 20篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 12篇 |
1985年 | 24篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 23篇 |
1976年 | 23篇 |
1975年 | 14篇 |
1974年 | 14篇 |
1973年 | 12篇 |
排序方式: 共有1588条查询结果,搜索用时 15 毫秒
41.
42.
The anomeric alkylation of D-fructose is efficiently catalyzed by mild acid catalysts. Degradation of fructose is negligible under the conditions applied. 相似文献
43.
The objective of this study was to establish the relation between the calcium sequestering capacity (SC) of dicarboxy-starch and that of dicarboxy-inulin, and the oxidation degree of these products. An S-type curve is obtained when plotting the SC of oxidized starch versus the degree of oxidation. By contrast the sequestering capacity of dicarboxy-inulin increases linearly with the degree of oxidation. The difference in behaviour of these materials can be attributed to the fact that upon starch oxidation the favourable oxydiacetate structure is obtained only after substantial conversion, whereas in inulin this structure is obtained immediately and is present in each oxidized fructose unit. 相似文献
44.
45.
46.
Vesterlund S Vankerckhoven V Saxelin M Goossens H Salminen S Ouwehand AC 《International journal of food microbiology》2007,116(3):325-331
The widespread use of immunosuppressive therapy and antimicrobial agents as well as novel probiotics without a long history of safe use has increased requirements for safety assessment of probiotic lactobacilli. In this study 44 faecal, 52 blood and 15 probiotic isolates (including 3 dairy strains) of Lactobacillus were assayed for their adhesion properties to extracellular matrix proteins and mucus, hemolysis, ability to avoid the induction of respiratory burst in peripheral blood mononucleocytes (PMN) and resistance to human serum. Among tested strains adhesion to collagen, fibrinogen and mucus was isolate-specific and no statistically significant differences were obtained between faecal, blood and probiotic isolates. However, blood isolates showed a trend for higher adhesion to mucus than probiotic strains (P=0.07). Probiotic strains induced lower respiratory burst in PMN when compared to the blood isolates (P<0.05). Moreover, there was a positive correlation between adhesion to collagen and induction of respiratory burst for faecal isolates (P<0.05). In the determination of serum resistance, probiotic strains showed a trend for lower sensitivity to human serum-mediated killing when compared to the faecal isolates (P=0.07). None of the measurable virulence factors were found to be present at statistically higher level in clinical blood isolates when compared to faecal and/or probiotic isolates indicating that these factors do not cause risk when safety of probiotics is considered. However, the significance of adhesion to mucus, low induction of respiratory burst in PMN and resistance to human serum-mediated killing may need further evaluation in experimental animal models and in epidemiological data. 相似文献
47.
48.
This paper discusses the effect of additions of platinum group metals (PGMs) on the composition of the passive surface layer formed on stainless steels in reducing acid media. It has been shown that there is an accumulation of these noble metals on the surface of the alloy during the period of active dissolution. The morphology and factors influencing this accumulation of PGMs on the surface are discussed. It was also found that there are differences between passive films formed spontaneously and those formed under potentiostatic control. An interesting fact emerging from the investigations is that different PGMs form different types of oxides on the passivated surfaces. Areas for possible future research are mentioned. 相似文献
49.
Coordination‐Assisted Bioorthogonal Chemistry: Orthogonal Tetrazine Ligation with Vinylboronic Acid and a Strained Alkene
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Selma Eising Dr. Bo‐Tao Xin Fleur Kleinpenning Jurriaan J. A. Heming Dr. Bogdan I. Florea Prof. Dr. Herman S. Overkleeft Dr. Kimberly M. Bonger 《Chembiochem : a European journal of chemical biology》2018,19(15):1648-1652
Bioorthogonal chemistry can be used for the selective modification of biomolecules without interfering with any other functionality that might be present. Recent developments in the field include orthogonal bioorthogonal reactions to modify multiple biomolecules simultaneously. During our research, we observed that the reaction rates for the bioorthogonal inverse‐electron‐demand Diels–Alder (iEDDA) reactions between nonstrained vinylboronic acids (VBAs) and dipyridyl‐s‐tetrazines were exceptionally higher than those between VBAs and tetrazines bearing a methyl or phenyl substituent. As VBAs are mild Lewis acids, we hypothesised that coordination of the pyridyl nitrogen atom to the boronic acid promoted tetrazine ligation. Herein, we explore the molecular basis and scope of VBA–tetrazine ligation in more detail and benefit from its unique reactivity in the simultaneous orthogonal tetrazine labelling of two proteins modified with VBA and norbornene, a widely used strained alkene. We further show that the two orthogonal iEDDA reactions can be performed in living cells by labelling the proteasome by using a nonselective probe equipped with a VBA and a subunit‐selective VBA bearing a norbornene moiety. 相似文献
50.
Continuous operation of membrane bioreactor treating toluene vapors by Burkholderia vietnamiensis G4
Amit Kumar Jo Dewulf Munkhtsetseg Luvsanjamba Herman Van Langenhove 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2008,140(1-3):193-200
A laboratory-scale biofilm membrane bioreactor inoculated with Burkholderia vietnamiensis G4 was examined to treat toluene vapors in a waste gas stream. The gas feed side and nutrient solution were separated by a composite membrane consisting of a porous polyacrylonitrile (PAN) support layer coated with a very thin (0.3 μm) dense polydimethylsiloxane (PDMS) top layer. After inoculation, a biofilm developed on the dense layer. The biofilm membrane bioreactor was operated continuously at different residence times (28–2 s) and loading rates (1.2–26.7 kg m−3 d−1), with inlet toluene concentrations ranging from 0.21 to 4.1 g m−3. The overall performance of the membrane bioreactor was evaluated over a period of 165 days. Removal efficiencies ranging from 78% to 99% and elimination capacities from 4.2 to 14.4 kg m−3 d−1 were observed after start-up period depending on the mode of operation. A maximum elimination capacity of 14.4 kg m−3 d−1 was observed at a loading rate of 17.4 kg m−3 d−1. Overall, the results illustrate that biofilm membrane reactors can potentially be more effective than conventional biofilters and biotrickling filters for the treatment of air pollutants such as toluene. 相似文献