全文获取类型
收费全文 | 1504篇 |
免费 | 83篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 21篇 |
综合类 | 7篇 |
化学工业 | 526篇 |
金属工艺 | 34篇 |
机械仪表 | 31篇 |
建筑科学 | 100篇 |
矿业工程 | 4篇 |
能源动力 | 30篇 |
轻工业 | 93篇 |
水利工程 | 12篇 |
无线电 | 98篇 |
一般工业技术 | 288篇 |
冶金工业 | 142篇 |
原子能技术 | 2篇 |
自动化技术 | 207篇 |
出版年
2023年 | 29篇 |
2022年 | 23篇 |
2021年 | 53篇 |
2020年 | 33篇 |
2019年 | 31篇 |
2018年 | 42篇 |
2017年 | 29篇 |
2016年 | 61篇 |
2015年 | 45篇 |
2014年 | 63篇 |
2013年 | 86篇 |
2012年 | 83篇 |
2011年 | 99篇 |
2010年 | 60篇 |
2009年 | 66篇 |
2008年 | 78篇 |
2007年 | 71篇 |
2006年 | 61篇 |
2005年 | 53篇 |
2004年 | 39篇 |
2003年 | 34篇 |
2002年 | 43篇 |
2001年 | 16篇 |
2000年 | 31篇 |
1999年 | 27篇 |
1998年 | 21篇 |
1997年 | 29篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 21篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 12篇 |
1973年 | 6篇 |
1969年 | 6篇 |
排序方式: 共有1595条查询结果,搜索用时 156 毫秒
71.
Contribution to the Biosynthesis of High-amylose Pea Starches Biosynthesis of starch is a complex process but few details are still unknown. This paper describes an investigation upon pea starch biosynthesis. Peas as a source of starch offer two qualities, a pea starch with 40% amylose content (smooth pea starch) and a pea starch with more than 60% amylose content (wrinkled pea starch). Samples for analysis were taken during growth. According to the quantitative determination of starch and amylose the accuracy of amylose detection was tested. Furthermore a qualitative analysis was carried out by molecular weight estimation of the starch. Both kinds of peas showed a high amylose synthesis during the last few days of growth, whereas amylopectin synthesis was highly in earlier stages. Wrinkled peas have shown only little synthesis activity of amylopectin during maturity. Therefore the amylose content of these peas was higher, instead of equal amylose synthesis quotas of both smooth and wrinkled peas. 相似文献
72.
Biocatalysis offers a broad spectrum of possible ecological and economic advantages over conventional chemical catalysis processes, e.g., lower energy consumption and high enantio selectivity. The focus of this work is on gas-liquid reactions. These are of great importance in the chemical and biochemical industry and subject of current research since they are often limited by mass transfer or show low selectivity. Different suitable biocatalytically gas-liquid reaction systems were tested in capillary reactor designs in order to obtain information about the interaction between reaction and fluid mechanics. Furthermore, an optical measuring method was established. The experiments were performed in batch mode in a glass beaker with a flow cuvette for UV/Vis measurement of product concentration. 相似文献
73.
Investigations on the Amylose Determination in High Protein Starch Source Materials, Especially Peas. The proposed utilization of amylose rich starches requires different methods of amylose determination. In addition to laboratory methods also simple tests are important to that. Because the discussed legume starches are hardly investigated, first of all the suitability of the amperometric iodine titration had to be checked. Then a more easier work was described. In the case of routine analyses a modified test procedure was compared with the method of iodine titration. 相似文献
74.
75.
Akylbek Sydykov Himal Luitel Argen Mamazhakypov Malgorzata Wygrecka Kabita Pradhan Oleg Pak Aleksandar Petrovic Baktybek Kojonazarov Norbert Weissmann Werner Seeger Friedrich Grimminger Hossein Ardeschir Ghofrani Djuro Kosanovic Ralph Theo Schermuly 《International journal of molecular sciences》2020,21(23)
Although the response of the right ventricle (RV) to the increased afterload is an important determinant of the patient outcome, very little is known about the underlying mechanisms. Mast cells have been implicated in the pathogenesis of left ventricular maladaptive remodeling and failure. However, the role of mast cells in RV remodeling remains unexplored. We subjected mast cell-deficient WBB6F1-KitW/W-v (KitW/KitW-v) mice and their mast cell-sufficient littermate controls (MC+/+) to pulmonary artery banding (PAB). PAB led to RV dilatation, extensive myocardial fibrosis, and RV dysfunction in MC+/+ mice. In PAB KitW/KitW-v mice, RV remodeling was characterized by minimal RV chamber dilatation and preserved RV function. We further administered to C57Bl/6J mice either placebo or cromolyn treatment starting from day 1 or 7 days after PAB surgery to test whether mast cells stabilizing drugs can prevent or reverse maladaptive RV remodeling. Both preventive and therapeutic cromolyn applications significantly attenuated RV dilatation and improved RV function. Our study establishes a previously undescribed role of mast cells in pressure overload-induced adverse RV remodeling. Mast cells may thus represent an interesting target for the development of a new therapeutic approach directed specifically at the heart. 相似文献
76.
Isabell Kemker Rebecca C. Feiner Prof. Dr. Kristian M. Müller Prof. Dr. Norbert Sewald 《Chembiochem : a European journal of chemical biology》2020,21(4):496-499
Monomeric RGD peptides show unspecific fluid-phase uptake in cells, whereas multimeric RGD peptides are thought to be internalized by integrin-mediated endocytosis. However, a potential correlation between uptake mechanism and molecular mass has been neglected so far. A dual derivatization of peptide c(RGDw(7Br)K) was performed to investigate this. A fluorescent probe was installed by chemoselective Suzuki–Miyaura cross-coupling of the 7-bromotryptophan and a poly(ethylene glycol) (PEG) linker was attached to the lysine residue. Flow cytometry and live cell imaging confirmed unspecific uptake of the small, non-PEGylated peptide, whereas the PEG5000 peptide conjugate unveiled a selective internalization by M21 cells overexpressing αvβ3 and no uptake in αv-deficient M21L cells. 相似文献
77.
A non-conserved sequence in the 5'region of the CYH2 intron from Saccharomyces cerevisiae controls splicing efficiency of the pre-mRNA 总被引:2,自引:0,他引:2
Ulrike Swida Eduardo Thüroff Edith Steindert Norbert F. Kufer 《Yeast (Chichester, England)》1988,4(3):209-217
The CYH2 gene from Saccharomyces cerevisiae containing one 510 bp intron is spliced inefficiently. We have shown previously that a non-conserved sequence within the intron is responsible for this low splicing efficiency. Using synthetic oligonucleotides comprising the identified region we show in this report that a very short region contains the specificity to act negatively on the splicing efficiency of the CYH2 gene. Furthermore, this sequence influences the splicing efficiency only when it is placed close to the 5' splice site of the gene. Investigations with chimeric CYH2/beta-actin genes show that this sequence acts independent from its natural surroundings. We propose that this sequence might interact with splicing factor(s). 相似文献
78.
Covaci A Gerecke AC Law RJ Voorspoels S Kohler M Heeb NV Leslie H Allchin CR De Boer J 《Environmental science & technology》2006,40(12):3679-3688
Hexabromocyclododecanes (HBCDs) are brominated aliphatic cyclic hydrocarbons used as flame retardants in thermal insulation building materials, upholstery textiles, and electronics. As a result of their widespread use and their physical and chemical properties, HBCDs are now ubiquitous contaminants in the environment and humans. This review summarizes HBCD concentrations in several environmental compartments and analyzes these data in terms of point sources versus diffuse sources, biomagnification potential, stereoisomer profiles, time trends, and global distribution. Generally, higher concentrations were measured in samples (air, sediment, and fish) collected near point sources (plants producing or processing HBCDs), while lower concentrations were recorded in samples from locations with no obvious sources of HBCDs. High concentrations were measured in top predators, such as marine mammals and birds of prey (up to 9600 and 19 200 ng/g lipid weight, respectively), suggesting a biomagnification potential for HBCDs. Relatively low HBCD concentrations were reported in the few human studies conducted to date (median values varied between 0.35 and 1.1 ng/g lipid weight). HBCD levels in biota are increasing slowly and seem to reflect the local market demand. One important observation is the shiftfrom the high percentage of the gamma-HBCD stereoisomer in the technical products to a dominance of the alpha-HBCD stereoisomer in biological samples. A combination of factors such as variations in solubility, partitioning behavior, uptake, and, possibly, selective metabolism of individual isomers may explain the observed changes in stereoisomer patterns. Recommendations for further work include research on how HBCDs are transferred from products into the environment upon production, use, and disposal. Time trends need to be analyzed more in detail, including HBCD stereoisomers, and more data on terrestrial organisms are needed, especially for humans. Whenever possible, HBCDs should be analyzed as individual stereoisomers in order to address their fate and effects. 相似文献
79.
Coal-derived liquids are susceptible to oxidative degradation. Two different weight ratios of SRC-I/SRC-II blends, with or without phenol derivatives, have been subjected to accelerated ageing studies. Viscosity, infrared, elemental analysis, molecular weight determination, and solvent analysis are used to examine the properties of the degradation products. On ageing, there is a large increase in the amount of toluene-insoluble material, decrease in oil components, and a relatively constant amount of asphaltenes. The oxygen content increases in the aged toluene-insoluble and asphaltene fractions, and a new absorption at ≈1700 cm?1 (the C = 0 group) appears in these two fractions only. On the addition of phenol itself and the less hindered phenol derivatives, the original hydrogen-bonding between the acidic and basic fuctional groups in the coal liquids is apparently disrupted because the added phenol can now interact with the proton-accepting species in the liquids, thus leading to a lower viscosity. This does not mean that the unhindered phenols retard the rate of ageing. The original hydrogen-bonding in the coal-derived liquid now gives way to a new hydrogen-bonding, and ageing occurs with the latter. The more hindered phenol derivatives are not as effective as phenol in disrupting the original hydrogen-bonding in the coal-derived liquids. 相似文献
80.
Inf rarotspektroskopie von Wasser in Schlacken. Chemischer Bindungszustand von Wasser in Schlacken, Abhängigkeit der integralen Extinktion der OH-Banden vom Wasserdampfpartialdruck. Wasserstoff beim ESU-Verfahren. 相似文献