全文获取类型
收费全文 | 1287篇 |
免费 | 51篇 |
专业分类
电工技术 | 9篇 |
综合类 | 2篇 |
化学工业 | 249篇 |
金属工艺 | 32篇 |
机械仪表 | 25篇 |
建筑科学 | 53篇 |
矿业工程 | 8篇 |
能源动力 | 18篇 |
轻工业 | 154篇 |
水利工程 | 6篇 |
石油天然气 | 4篇 |
无线电 | 82篇 |
一般工业技术 | 258篇 |
冶金工业 | 291篇 |
原子能技术 | 14篇 |
自动化技术 | 133篇 |
出版年
2023年 | 21篇 |
2022年 | 34篇 |
2021年 | 52篇 |
2020年 | 22篇 |
2019年 | 24篇 |
2018年 | 30篇 |
2017年 | 24篇 |
2016年 | 32篇 |
2015年 | 23篇 |
2014年 | 25篇 |
2013年 | 76篇 |
2012年 | 51篇 |
2011年 | 73篇 |
2010年 | 51篇 |
2009年 | 46篇 |
2008年 | 61篇 |
2007年 | 44篇 |
2006年 | 55篇 |
2005年 | 34篇 |
2004年 | 30篇 |
2003年 | 21篇 |
2002年 | 31篇 |
2001年 | 23篇 |
2000年 | 27篇 |
1999年 | 13篇 |
1998年 | 61篇 |
1997年 | 51篇 |
1996年 | 25篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 31篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1970年 | 5篇 |
排序方式: 共有1338条查询结果,搜索用时 31 毫秒
41.
The use of the Internet for conducting research has found that the level of anonymity intrinsic to web-based surveys is useful in deterring various participant biases. Though, concerns about Internet privacy could interfere with the effects of perceived anonymity and influence how a person responds. In this study, participants were asked to take an Internet survey and then were randomly assigned to conditions with varying degrees of implied privacy in which they answered questions about their desire for casual sex (sociosexuality) and their lifetime sexual partners. Only in the condition without any threat to the participant’s anonymity was there no difference between men and women’s reports of their sexual behavior. However, in every condition men reported having a significantly higher sociosexuality than women. Findings are consistent with both the biologic and gender-biased explanations in differences of self-report for sexual information. Implications for social constraints and Internet based research are discussed. 相似文献
42.
Melanie Holzwarth Sabine Korhummel Reinhold Carle Dietmar R. Kammerer 《European Food Research and Technology》2012,234(2):207-222
Strawberry purées were prepared using a commercial polygalacturonase (PG) and a highly purified pectinesterase (PE) preparation,
respectively. To elucidate the effect of pectin on color stability following enzymatic pulp maceration, pectin composition
was studied by isolating and fractionating the alcohol-insoluble residue from the strawberry purées. The purées were stored
at +20 and +4 °C in the dark over a period of 24 weeks monitoring the amounts of monomeric and polymeric anthocyanins as well
as antioxidant activities (FRAP, TEAC). Individual anthocyanins were analyzed by HPLC–DAD–MS
n
, and color measurements were obtained in the CIE L*a*b* system. Pectin composition was significantly modified following enzymatic maceration of the purées. While PG treatment generally
resulted in pectin losses, oxalate-soluble pectins were increased in PE-treated purées. After 24 weeks of storage, the best
anthocyanin retention was observed in PE-treated purées. Such products also revealed greatest anthocyanin half-life values
and lowest proportion of polymeric pigments. Compared to an untreated control, enzymatic purée maceration using the PG was
also beneficial for pigment retention, but less effective than PE. In contrast, color and antioxidant activity were independent
of both enzymatic treatments. An initial heating step (90 °C, 10 s) for immediate inactivation of native enzymes such as polyphenoloxidases
slightly improved pigment stability, while lowered temperature during mash maceration was less effective. However, by far
best color and pigment retention were achieved when the purées were stored at 4 °C in the dark. 相似文献
43.
Houses in multiple occupation (HMOs) in which tenants share facilities are housing an increasing proportion of vulnerable adults who have limited affordable housing options. However, knowledge about how these types of property are managed is limited. In this paper, we examine the governance function of HMO landlords from the perspective of landlords/landlord agents and the tenants that live within their properties. The landlord exercises control through formal and informal risk assessment of tenants and close surveillance of them. These control mechanisms may also involve direct or indirect provision of support and care to some tenants. This illustrates the complex relationship between care and control and the extent to which both are integral to the housing management of vulnerable tenants living in HMOs. We suggest that this dual function calls for a critical examination of what constitutes a ‘good landlord’. 相似文献
44.
Morovič Peter Morovič Ján Tastl Ingeborg Gottwals Melanie Dispoto Gary 《Structural and Multidisciplinary Optimization》2019,60(3):895-908
Structural and Multidisciplinary Optimization - Controlling the composition of individual voxels allows for a co-optimization of 3D-printed part properties such as color and mechanical ones. As a... 相似文献
45.
Accurate reporting of sources of income is needed in studies of intergenerational transfers and welfare of the elderly. The objective of this paper is to investigate how memory in the elderly is related to the reporting of remittances received from their children in Thailand. Using data from a longitudinal study of 1036 persons age 60 to 93 in a province in Thailand, the influence of a word recall (verbal learning and recall), and nickname recall (verbal learning and recall) on reporting of remittance was assessed. Initially, both measures were positively and significantly related to the reporting of remittance. The results remained significant only for the nickname task after controlling for education, wealth, living arrangements and disability. The results highlight the importance of cognitive issues in the quality of data and the need for attention to memory in questionnaire design. 相似文献
46.
Sand dune migration poses serious environmental and social problems for both the infrastructure and communities in the Saudi Arabian Peninsula. In order to monitor and better understand dune migration, a new method is proposed to estimate sand dune displacement/migration by using satellite laser altimetry data from the ICESat mission in the Rub Al-Khali. This method will exploit not only the differences in the observed ICESat elevation profiles, but also the phase differences between two co-located tracks when observed at different times. By using the phase differences, the proposed method will be able to estimate dune displacement vectors with an accuracy of 5 m root mean square. This accuracy has been validated using synthetic data with known displacements. The major causes for dune migration are the wind regime and the type of dunes (e.g. grain size and vegetation cover). A comparison of estimated dune displacement correlated well with the prevailing wind regime during the observation time period. A comparison with satellite imagery revealed that the dune shape and direction (i.e. the representative parameters of dune migration) are in agreement with the estimated displacement vectors. This method represents one of the first attempts to monitor dune migration using space observations only. 相似文献
47.
The requirements concerning the technical availability as part of the overall equipment effectiveness increase constantly in production nowadays. Unplanned downtimes have to be prevented via efficient methods. Predictive, condition-based maintenance represents a valuable approach for fulfilling these demands, but precise models for state estimation are missing. From the manufacturers’ point of view the challenge consists in wear models with the capability of specifying the correct component’s state as well as providing reliable failure forecasts. Unfortunately, nowadays creation of wear models is based on specific stress tests or design of experiments from the manufacturer. The integration of the production phase or even data feedback and user knowledge does not take place. New potential is promised by cross-cutting technologies from ICT like cloud technologies—in general virtual platform concepts—or approaches of machine learning as enabling technologies. The objective of this paper is to adopt existing algorithms to the new application of condition monitoring in order to evaluate the applicability for automated training of robust wear models. In that context the most commonly used algorithms are described and the reader gets an impression what challenges have to be met when dealing with machine learning. A selection of about ten algorithms with 45 variants is evaluated for four different features within a packaging machine. In the outlook the embedding of the trained model in a cloud architecture is presented. 相似文献
48.
Melanie Montgomery Allan Enemark Anders Hangaard 《Journal of Failure Analysis and Prevention》2014,14(5):554-563
The titanium condenser has been in operation for 24 years at Amager unit 3 power plant. In February 2012, the plant was contaminated by seawater due to a failed condenser tube and some tubes were plugged. A month later, the plant tripped again. Small leaks were found again and finally approx. 200 tubes were plugged before the condenser was in service again. A series of inspections, NDT, and destructive examinations were conducted to try and understand the cause of failure in the tubes within the condenser. After such investigations, degradation mechanisms such as inner fouling, steam impingement, and fretting/erosion around the supports could be discounted. Ductile cracks were found in the tube within the tubesheet. From circumstantial evidence, it was concluded that failure was caused by a semi-filled condenser which led to a mismatch in expansion coefficients of filled tubes and unfilled tubes during a plant trip. In addition, small amounts of titanium hydride were revealed to be present in the tubes within the tubesheet indicating that the carbon steel tubesheet was corroding due to ingress of salt water. Although this was not the reason for the failure, it indicated the need for repair of the epoxy coating in the waterbox. 相似文献
49.
Stefan Alexander Tennigkeit Raziye Karapinar Till Rudack Max-Aylmer Dreier Philipp Althoff Dennis Eickelbeck Tatjana Surdin Michelle Grömmke Melanie D. Mark Katharina Spoida Mathias Lübben Udo Höweler Prof. Dr. Stefan Herlitze Prof. Dr. Klaus Gerwert 《Chembiochem : a European journal of chemical biology》2019,20(14):1766-1771
The primary goal of optogenetics is the light-controlled noninvasive and specific manipulation of various cellular processes. Herein, we present a hybrid strategy for targeted protein engineering combining computational techniques with electrophysiological and UV/visible spectroscopic experiments. We validated our concept for channelrhodopsin-2 and applied it to modify the less-well-studied vertebrate opsin melanopsin. Melanopsin is a promising optogenetic tool that functions as a selective molecular light switch for G protein-coupled receptor pathways. Thus, we constructed a model of the melanopsin Gq protein complex and predicted an absorption maximum shift of the Y211F variant. This variant displays a narrow blue-shifted action spectrum and twofold faster deactivation kinetics compared to wild-type melanopsin on G protein-coupled inward rectifying K+ (GIRK) channels in HEK293 cells. Furthermore, we verified the in vivo activity and optogenetic potential for the variant in mice. Thus, we propose that our developed concept will be generally applicable to designing optogenetic tools. 相似文献
50.