全文获取类型
收费全文 | 492篇 |
免费 | 5篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 74篇 |
金属工艺 | 4篇 |
机械仪表 | 9篇 |
建筑科学 | 13篇 |
矿业工程 | 2篇 |
能源动力 | 6篇 |
轻工业 | 24篇 |
水利工程 | 9篇 |
无线电 | 34篇 |
一般工业技术 | 70篇 |
冶金工业 | 150篇 |
原子能技术 | 7篇 |
自动化技术 | 83篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 6篇 |
2013年 | 21篇 |
2012年 | 9篇 |
2011年 | 26篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 21篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 50篇 |
1997年 | 33篇 |
1996年 | 28篇 |
1995年 | 13篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有497条查询结果,搜索用时 234 毫秒
1.
2.
Das Autobahnmautgesetz zeichnet sich durch eine strenge Zweckbindung für die Mautdaten aus. Diese dürfen ausschlie?lich für
die Zwecke des Mautgesetzes erhoben und verarbeitet werden. Diese Vorgabe hat das LG Magdeburg in einem Beschluss richtungsweisend
auch für die Verbindungsdaten der GSM-Kommunikation best?tigt. 相似文献
3.
Bayazit Mahmut; Hammer Tove Helland; Wazeter David L. 《Canadian Metallurgical Quarterly》2004,89(4):738
Methodological problems in studies of union commitment were identified and illustrated with data from 4,641 members and 479 stewards in 297 local teachers' unions. Using a 20-item union commitment scale, results confirmed the existence of 3 substantive factors and 1 method factor at the individual level of analysis: loyalty to the union, responsibility to the union, willingness to work for the union, and a factor of negatively worded items. Tests of measurement invariance showed that the scale captured commitment for rank-and-file members but not for union stewards. The authors also found partial measurement invariance between long-time and newer members and full measurement invariance between men and women. Finally, the authors found that violation of the statistical assumption of independence reduced model fit when individual commitment scores were analyzed without attention to the hierarchical nature of the data. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Fertilisers may contain pollutants that are applied to the field together with the nutrients. Comparing fertilisers is difficult because of their different concentrations of nutrients and pollutants. In this study an already existing model was taken. It was further developed to compare nutrient fluxes (N, P, K, Ca, Mg, S, humus) and pollutants (heavy metals and pharmaceuticals) of pig and cattle slurry as well as human urine. The data used is taken from literature and, in the case of pharmaceuticals in urine, daily excretion rates were calculated. An amount of 19 m3 ha(-1) a(-1) undiluted urine can be applied, limiting factor is sulphur. Without taking over-fertilisation into account, an addition of mineral fertiliser is required to any organic fertiliser application. In general, heavy metal, antibiotic, and hormone fluxes are higher by using animal manure then urine as fertiliser. However, additional loads of other pharmaceuticals consumed by humans have to be considered. Overall, the model is a suitable tool worthwhile to be extended in aspects of hygiene, environmental impacts as for example, degradation processes as well as ecotoxicology. 相似文献
5.
It is well known that horizontal surfaces of high strength concrete (HSC) are susceptible to cracking in the time before and
during setting. It appears that there are two critical time periods for such cracking: An early period ranging from placing
to an hour or two, and a late period that covers the setting time and early hardening. The latter is considered here. In this
period, the cracking risk may be assessed from the ratio between strain (the volume change) and tensile strain capacity, or
from the ratio between stress generated from the volume change at restraint, and the tensile strength. All these parameters
were measured. It is shown that relatively moderate volume changes of HSC-surfaces caused by drying plus cooling, generate
restraining stress that may exceed the tensile strength, and thus, generate failure. The results indicate that crack risk
assessment from stress/strength is more reliable than using strain/strain capacity. The starting point of tensile strength
evolution of hardened concrete seems to coincide fairly well with the initial setting time. Also, the tensile strain capacity
reaches a low level at this point, but continues descending for another hour or more. 相似文献
6.
A protein phosphatase was purified from the stroma of Pea (Pisum sativum L.) chloroplasts that is capable of dephosphorylating synthetic phosphopeptides. Following chromatographic purification of greater than 400-fold, two-dimensional electrophoresis indicated that the stromal protein phosphatase is a 29-kD protein. A similar molecular size was determined for the protein-phosphatase activity using gel-permeation chromatography, indicating that the stromal protein phosphatase is probably a monomer. The purified enzyme was able to dephosphorylate synthetic phosphopeptides, which mimic the thylakoid light-harvesting complex II (LHC-II) N terminus, as well as LHC-II in thylakoid membranes, but did not dephosphorylate the major 64-kD phosphoprotein in the stroma. The stromal protein phosphatase did not discriminate between dephosphorylation of phosphothreonine and phosphoserine residues in synthetic peptide substrates, providing further evidence that this enzyme is distinct from the protein phosphatase localized in thylakoid membranes. The exact physiological role of the stromal protein phosphatase has yet to be determined, but it may function in the dephosphorylation of LHC-II. 相似文献
7.
8.
9.
Lisa Goedtke Heike Sprenger Ute Hofmann Felix F. Schmidt Helen S. Hammer Ulrich M. Zanger Oliver Poetz Albrecht Seidel Albert Braeuning Stefanie Hessel-Pras 《International journal of molecular sciences》2021,22(1)
Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants produced by incomplete combustion of organic matter. They induce their own metabolism by upregulating xenobiotic-metabolizing enzymes such as cytochrome P450 monooxygenase 1A1 (CYP1A1) by activating the aryl hydrocarbon receptor (AHR). However, previous studies showed that individual PAHs may also interact with the constitutive androstane receptor (CAR). Here, we studied ten PAHs, different in carcinogenicity classification, for their potential to activate AHR- and CAR-dependent luciferase reporter genes in human liver cells. The majority of investigated PAHs activated AHR, while non-carcinogenic PAHs tended to activate CAR. We further characterized gene expression, protein abundancies and activities of the AHR targets CYP1A1 and 1A2, and the CAR target CYP2B6 in human HepaRG hepatoma cells. Enzyme induction patterns strongly resembled the profiles obtained at the receptor level, with AHR-activating PAHs inducing CYP1A1/1A2 and CAR-activating PAHs inducing CYP2B6. In summary, this study provides evidence that beside well-known activation of AHR, some PAHs also activate CAR, followed by subsequent expression of respective target genes. Furthermore, we found that an increased PAH ring number is associated with AHR activation as well as the induction of DNA double-strand breaks, whereas smaller PAHs activated CAR but showed no DNA-damaging potential. 相似文献
10.