全文获取类型
收费全文 | 6742篇 |
免费 | 330篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 57篇 |
综合类 | 5篇 |
化学工业 | 1230篇 |
金属工艺 | 124篇 |
机械仪表 | 138篇 |
建筑科学 | 289篇 |
矿业工程 | 15篇 |
能源动力 | 211篇 |
轻工业 | 593篇 |
水利工程 | 70篇 |
石油天然气 | 19篇 |
武器工业 | 2篇 |
无线电 | 663篇 |
一般工业技术 | 1144篇 |
冶金工业 | 1567篇 |
原子能技术 | 45篇 |
自动化技术 | 912篇 |
出版年
2023年 | 48篇 |
2022年 | 88篇 |
2021年 | 144篇 |
2020年 | 108篇 |
2019年 | 127篇 |
2018年 | 167篇 |
2017年 | 147篇 |
2016年 | 187篇 |
2015年 | 137篇 |
2014年 | 184篇 |
2013年 | 345篇 |
2012年 | 329篇 |
2011年 | 396篇 |
2010年 | 283篇 |
2009年 | 318篇 |
2008年 | 354篇 |
2007年 | 358篇 |
2006年 | 280篇 |
2005年 | 287篇 |
2004年 | 222篇 |
2003年 | 178篇 |
2002年 | 196篇 |
2001年 | 128篇 |
2000年 | 95篇 |
1999年 | 104篇 |
1998年 | 265篇 |
1997年 | 181篇 |
1996年 | 151篇 |
1995年 | 99篇 |
1994年 | 102篇 |
1993年 | 114篇 |
1992年 | 56篇 |
1991年 | 54篇 |
1990年 | 60篇 |
1989年 | 69篇 |
1988年 | 63篇 |
1987年 | 54篇 |
1986年 | 58篇 |
1985年 | 60篇 |
1984年 | 42篇 |
1983年 | 50篇 |
1982年 | 46篇 |
1981年 | 27篇 |
1980年 | 34篇 |
1979年 | 30篇 |
1978年 | 37篇 |
1977年 | 32篇 |
1976年 | 42篇 |
1975年 | 19篇 |
1974年 | 23篇 |
排序方式: 共有7084条查询结果,搜索用时 78 毫秒
991.
Rapid and successful introduction of new products is a potentially significant source of competitive advantage for manufacturing firms. Organizations need to identify and manage those critical elements of the product development process (PDP) that have a positive influence on new product success. This research identifies the distinctive product development and design practices, policies and tools currently followed by companies (Navy contractors) that participated in an empirical research study known as the Best Manufacturing Practices Program. A summary of practices reported in the case studies is compiled using content analysis techniques, and the most interesting practices by individual companies are highlighted. We find numerous examples of sophisticated CAD techniques being used to enhance the development process, including expert system design advisers, computer simulation, and design databases. Companies are emphasizing the design policies of concurrent engineering and teamwork, and documenting design process knowledge into design manuals. Company effort still appear focused primarily on the phase of detailed design rather than the concept selection phase. 相似文献
992.
Piotrkowski Chaya S.; Collins Raymond C.; Knitzer Jane; Robinson Ruth 《Canadian Metallurgical Quarterly》1994,49(2):133
Steps must be taken to strengthen mental health services by building on Head Start's philosophy and by translating innovations in mental health services for older children and adolescents into improved services for young children and their families. Recommendations for strengthening Head Start's mental health program include creating a unified vision that reaffirms a holistic, family-focused, and comprehensive services approach; ensuring that mental health services are responsive to the diversity in families served; increasing coordination of mental health services and linkages with new initiatives; increasing resources and providing assistance in gaining access to new sources of funding; supporting innovation; and integrating the new paradigm for children's mental health services into more traditional approaches to intervention within Head Start. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
This study describes the translocation of the brain specific protein kinase C gamma isoenzyme (PKCgamma) in the hippocampus during food rewarded spatial learning. The holeboard test was used for spatial orientation, and immunoblot analysis was used for assessment of PKCgamma in cytosolic, membrane-inserted and membrane-associated fractions. Membrane-associated PKCgamma was increased during early acquisition of spatial learning, but not in a later phase of training. This transient and apparently temporary intracellular PKCgamma translocation was only observed in the posterior but not in the anterior hippocampus, and was only detected within 10 min after termination of the learning trial. This study supports the idea that PKCgamma is significantly involved in the biochemical events underlying learning and memory, notably during the period of novel information processing. The results further promote the hypothesis that the hippocampus is specifically involved in temporal information processing, which requires the engagement of PKCgamma. 相似文献
994.
995.
CJ Morrell SJ Walters S Dixon KA Collins LM Brereton J Peters CG Brooker 《Canadian Metallurgical Quarterly》1998,316(7143):1487-1491
OBJECTIVES: To establish the relative cost effectiveness of community leg ulcer clinics that use four layer compression bandaging versus usual care provided by district nurses. DESIGN: Randomised controlled trial with 1 year of follow up. SETTING: Eight community based research clinics in four trusts in Trent. SUBJECTS: 233 patients with venous leg ulcers allocated at random to intervention (120) or control (113) group. INTERVENTIONS: Weekly treatment with four layer bandaging in a leg ulcer clinic (clinic group) or usual care at home by the district nursing service (control group). MAIN OUTCOME MEASURES: Time to complete ulcer healing, patient health status, and recurrence of ulcers. Satisfaction with care, use of services, and personal costs were also monitored. RESULTS: The ulcers of patients in the clinic group tended to heal sooner than those in the control group over the whole 12 month follow up (log rank P=0.03). At 12 weeks, 34% of patients in the clinic group were healed compared with 24% in the control. The crude initial healing rate of ulcers in intervention compared with control patients was 1.45 (95% confidence interval 1.04 to 2. 03). No significant differences were found between the groups in health status. Mean total NHS costs were 878.06 pounds per year for the clinic group and 859.34 pounds for the control (P=0.89). CONCLUSIONS: Community based leg ulcer clinics with trained nurses using four layer bandaging is more effective than traditional home based treatment. This benefit is achieved at a small additional cost and could be delivered at reduced cost if certain service configurations were used. 相似文献
996.
Members of the system Pd1-xMxSe2 (M=Ru,Co,Ni), prepared at ambient pressure, consisted of mixtures of PdSe2 and pyrite phases. Compositions with x > 0.4 for Ru and x > 0.3 for Co and Ni, prepared at a pressure of 50 Kbars and 1000°C, gave a single phase region crystallizing with the pyrite structure. 相似文献
997.
Examined the occurrence of individual behavioral differences in wolf cubs and the stability of the differences over the 1st 6 mo of life despite variations in the social environment. A litter of 5 male wolves was tested for reaction to unfamiliar people and unfamiliar objects and in a bone competition situation. The social environment was varied by housing the Ss alternately as a group, in pairs, and in isolation. Although there was a general tendency for less stability to be shown prior to 6 wks of age than after, the behaviors showed high stability over the course of the experiment. Results from the tests with unfamiliar objects indicate less stability when Ss were tested individually than when tested as a group, an effect suggesting that social structure may be a factor that increases the stability of responses to unfamiliar objects. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
999.
Successful modelling of the thermal behaviour of food products requires accurate knowledge of both the thermal properties of the product and the cooling media to which it is exposed to and a correct approach to validation of the model output against experimental temperature histories. This procedure is complicated where there is uncertainty in the location at which temperature is measured in the product. The cooling of a soft cylindrical cheese product that is partially immersed in brine and air is examined. As the cheese is very deformable, it is not possible to exactly identify the measurement location of the temperature-recording thermocouples. The Uniform and Exponential probability distributions were found to best represent the variability in thermocouple location at the centre and surface of the product, respectively. Expressions for the mean measured temperature at the centre and surface that result from the distributed nature of thermocouple location were obtained. These expressions were used to derive equivalent locations in the cheese which should be used when comparing model and experimental temperature predictions. The theoretical approach was also checked against Monte Carlo simulations and there was excellent agreement between them. It was shown that when validating model temperature histories against experimental readings that this phenomenon must be taken into account. 相似文献
1000.