全文获取类型
收费全文 | 1970篇 |
免费 | 22篇 |
专业分类
电工技术 | 11篇 |
化学工业 | 125篇 |
金属工艺 | 10篇 |
机械仪表 | 17篇 |
建筑科学 | 46篇 |
矿业工程 | 2篇 |
能源动力 | 24篇 |
轻工业 | 117篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 129篇 |
一般工业技术 | 157篇 |
冶金工业 | 1175篇 |
原子能技术 | 10篇 |
自动化技术 | 155篇 |
出版年
2021年 | 7篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 16篇 |
2013年 | 58篇 |
2012年 | 20篇 |
2011年 | 47篇 |
2010年 | 34篇 |
2009年 | 25篇 |
2008年 | 35篇 |
2007年 | 29篇 |
2006年 | 37篇 |
2005年 | 32篇 |
2004年 | 46篇 |
2003年 | 34篇 |
2002年 | 30篇 |
2001年 | 27篇 |
2000年 | 20篇 |
1999年 | 54篇 |
1998年 | 318篇 |
1997年 | 187篇 |
1996年 | 138篇 |
1995年 | 93篇 |
1994年 | 68篇 |
1993年 | 84篇 |
1992年 | 41篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 25篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 19篇 |
1985年 | 34篇 |
1984年 | 12篇 |
1983年 | 18篇 |
1982年 | 16篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 22篇 |
1978年 | 11篇 |
1977年 | 42篇 |
1976年 | 59篇 |
1975年 | 8篇 |
1973年 | 10篇 |
1972年 | 6篇 |
1968年 | 5篇 |
1967年 | 6篇 |
排序方式: 共有1992条查询结果,搜索用时 0 毫秒
31.
PURPOSE: To determine the frequency of remission in patients with essential blepharospasm and Meige syndrome. METHOD: Retrospective analysis of patients by means of questionnaire in an institutional setting. RESULTS: Among 238 patients diagnosed in a single institution as having essential blepharospasm or Meige syndrome, 27 (11.3%) claimed to be symptom free without curative surgery. The average time between onset and resolution in the patients who claimed remission was 4.85 years (range, 3 months to 22 years). Among these patients, the duration of remission averaged 6.33 years (range, 1 year to 14 years). CONCLUSION: Patients with essential blepharospasm or Meige syndrome have a small but definite potential for spontaneous remission of symptoms, particularly within the first 5 years after onset of symptoms. 相似文献
32.
Hunter S Howard M Marki P Gelpi MJ Francone J Reed G McGinty K Mayes B Ysmael R Johnson C 《Food management》1992,27(1):92-5, 98
Consumer confidence is at its lowest ebb since 1980. Economic growth is at a standstill & unemployment & inflation are both rising. Here's a front-line report from more than three dozen operators who are fending off the recession's dual pressures of slow sales & rising costs. They are using discount pricing, partnering with vendors, setting pay for performance standards & a variety of other recession-beating practices. 相似文献
33.
Damien Hunter Kee Heng Navdeep Mann Ravinder Anand-Ivell Richard Ivell 《International journal of molecular sciences》2021,22(8)
Xenobiotic exposure during pregnancy and lactation has been linked to perinatal changes in male reproductive outcomes and other endocrine parameters. This pilot study wished to assess whether brief maternal exposure of rats to xenobiotics dibutyl phthalate (DBP) or diethylstilbestrol (DES) might also cause long-term changes in hypothalamic gene expression or in reproductive behavior of the resulting offspring. Time-mated female Sprague Dawley rats were given either DBP (500 mg/kg body weight, every second day from GD14.5 to PND6), DES (125 µg/kg body weight at GD14.5 and GD16.5 only), or vehicle (n = 8–12 per group) and mild endocrine disruption was confirmed by monitoring postnatal anogenital distance. Hypothalamic RNA from male and female offspring at PND10, PND24 and PND90 was analyzed by qRT-PCR for expression of aromatase, oxytocin, vasopressin, ER-alpha, ER-beta, kisspeptin, and GnRH genes. Reproductive behavior was monitored in male and female offspring from PND60 to PND90. Particularly, DES treatment led to significant changes in hypothalamic gene expression, which for the oxytocin gene was still evident at PND90, as well as in sexual behavior. In conclusion, maternal xenobiotic exposure may not only alter endocrine systems in offspring but, by impacting on brain development at a critical time, can have long-term effects on male or female sexual behavior. 相似文献
34.
The “hardness” components in sea water can be considerably reduced by means of a new economical fixed bed technique called “Reciprocating Flow Ion Exchange”, when used in conjunction with a closed cycle exchanger-evaporator system. Removal of 87.9% of the calcium and 54.5% of the magnesium in sea water has been obtained with an overall flow rate of 5.0 U. S. g. p. m./sq. ft. Results from bench scale and a 5,000 g. p. d. pilot plant were identical. The virtually continuous cyclic steady-state process requires a small amount of exchanger (0.5 to 2% of the usual ion exchange methods, such as conventional fixed beds or fluidized beds). The effects of variation in operating parameters are discussed. 相似文献
35.
The purpose of the ozone process at the Sebago Lake Water Treatment Facility (SLWTF) is to meet the disinfection requirements of the Surface Water Treatment Rule with ozone and without filtration. The start-up experience is presented including initial operating strategies to meet disinfection requirements. An ozone system performance test conducted during the first month of plant operation is described and the results are reviewed. The initial and proposed activities of an ozone optimization project are discussed. 相似文献
36.
Studies on effects of dietary fatty acids as related to their position on triglycerides 总被引:9,自引:0,他引:9
This article reviews published literature on how the stereospecific structure of dietary triglycerides may affect lipid metabolism
in humans. Animal studies have shown enhanced absorption of fatty acids in the sn-2 position of dietary triglycerides. Increasing the level of the saturated fatty acid palmitic acid in the sn-2 position (e.g., by interesterification of the fat to randomize the positions of the fatty acids along the glycerol backbone)
has been shown in rabbits to increase the atherogenic potential of the fat without impacting levels of blood lipids and lipoproteins.
In contrast, enhancing the level of stearic acid in the sn-2 position has not been found to affect either atherogenic potential or levels of blood lipids and lipoproteins in rabbit.
Fatty acids other than palmitic and stearic have not been studied systematically with respect to possible positional effects.
A limited number of human studies have shown no significant effects of interesterified fats on blood lipid parameters. However,
it is unknown whether modifying the stereospecific structure of dietary triglycerides would affect atherogenicity or other
long-term health conditions in humans. It is possible that incorporation of palmitic acid into the sn-2 position of milk fat is beneficial to the human infant (as a source of energy for growth and development) but not to human
adults. Additional research is needed to determine whether processes like interesterification, which can be used to alter
physical parameters of dietary fats (e.g., melting characteristics), may result in favorable or unfavorable long-term effects
in humans. 相似文献
37.
J. Edward Hunter 《Journal of the American Oil Chemists' Society》1981,58(3):283-287
A major objective of commercial processing of soybean oil into edible products is to remove unwanted impurities from the oil
with the least possible effect on nutritional quality of the oil. Soybean oil is an excellent dietary source of essential
linoleic acid and also of tocopherols, which serve as sources of vitamin E and natural antioxidants. The data presented in
this report indicate that the nutritional quality of soybean oil is largely retained after typical commercial processing conditions.
Hydrogenation does reduce the level of essential fatty acids; however, typical commercial salad and cooking oils and shortenings
made from partially hydrogenated soybean oil retain nutritionally significant levels of essential fatty acids. Tocopherols
also are present at high levels in the finished oil. Among the unwanted components of crude soybean oil which are effectively
removed by processing are pesticide residues, phosphatides, free fatty acids, color pigments, and compounds causing objectionable
odors and flavors. 相似文献
38.
R. Hunter J. Rios J.M. Perez A. Vizan 《International Journal of Machine Tools and Manufacture》2006,46(6):683-697
The design of machining fixtures is a highly complex process that relies on designer experience and his/her implicit knowledge to achieve a good design. In order to facilitate its automation by the development of a knowledge-based application, the explicit definition of the fixture design process and the knowledge involved is a prior and a fundamental task to undertake. Additionally, a fundamental and well-known engineering principle should be considered: the functional requirements and their associated constraints should be the first input to any design process. Considering these two main ideas, this paper presents the development undertaken to facilitate the automation of the fixture design process based on a functional approach.In this context, the MOKA methodology has been used to elicit fixtures knowledge. IDEF0 and UML have been used to represent the fixture design process. A methodology based on the function concept and aiming to formalize such design process is proposed. Fixture functional requirements have been defined and formalized. Functional fixtures elements have been used to create a functional design solution, the link of these elements with the functional requirements and with typical commercial fixture components has been defined via tables and rules mapping. And finally, a prototype knowledge-based application has been developed in order to make an initial validation of the proposed methodology. 相似文献
39.
The purpose of this study was to measure the team skills of operational crime scene examiners (CSEs). The techniques used were based on established methods and helped to gain a greater understanding of the domain of forensic investigation. The research begins with a hierarchical task analysis and then adapts pre-established methods for measuring the performance of CSEs in four UK Police Forces. The process supports comparison between prescribed methods of 'good practice' and real world practice. This has allowed the identification of the distributed skills and tasks of the CSE. Using Annett et al.'s HTA(T), crime scene examination can be categorised and the communications and coordination structures occurring between teams investigating a burglary considered. This makes it possible to generalise the method to situations involving ad hoc teams. 相似文献
40.
The MatSeek system is an ontology-based federated search interface to key materials science databases and analytical tools. By combining Semantic Web and Web 2.0 technologies, MatSeek provides materials scientists with a single Web interface that enables them to search across disparate databases containing crystal-structure data, ionic-conductivity data, and phase stability data; render 3D crystal-structure images; calculate bond lengths and angles; retrieve relevant scholarly references; and identify potential new materials with the structure and properties required to satisfy specific applications. The MatOnto ontology underlying MatSeek enables integration of data across disparate databases, and Web 2.0 technologies enable iterative searching across the databases. The results retrieved from searching the previous database are used as input to the query on the next database. By providing materials scientists with a single, integrated Web interface to the critical materials science databases and analytical tools, MatSeek represents a significant advance toward a full-fledged materials-informatics workbench. 相似文献