全文获取类型
收费全文 | 9058篇 |
免费 | 152篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 68篇 |
综合类 | 7篇 |
化学工业 | 959篇 |
金属工艺 | 118篇 |
机械仪表 | 168篇 |
建筑科学 | 133篇 |
矿业工程 | 6篇 |
能源动力 | 202篇 |
轻工业 | 284篇 |
水利工程 | 10篇 |
石油天然气 | 20篇 |
无线电 | 914篇 |
一般工业技术 | 935篇 |
冶金工业 | 4403篇 |
原子能技术 | 26篇 |
自动化技术 | 969篇 |
出版年
2023年 | 27篇 |
2022年 | 95篇 |
2021年 | 131篇 |
2020年 | 39篇 |
2019年 | 62篇 |
2018年 | 77篇 |
2017年 | 80篇 |
2016年 | 102篇 |
2015年 | 105篇 |
2014年 | 148篇 |
2013年 | 428篇 |
2012年 | 265篇 |
2011年 | 351篇 |
2010年 | 296篇 |
2009年 | 348篇 |
2008年 | 287篇 |
2007年 | 255篇 |
2006年 | 211篇 |
2005年 | 168篇 |
2004年 | 149篇 |
2003年 | 146篇 |
2002年 | 110篇 |
2001年 | 108篇 |
2000年 | 77篇 |
1999年 | 201篇 |
1998年 | 1386篇 |
1997年 | 796篇 |
1996年 | 586篇 |
1995年 | 302篇 |
1994年 | 298篇 |
1993年 | 309篇 |
1992年 | 81篇 |
1991年 | 104篇 |
1990年 | 99篇 |
1989年 | 92篇 |
1988年 | 88篇 |
1987年 | 75篇 |
1986年 | 59篇 |
1985年 | 59篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 36篇 |
1981年 | 27篇 |
1980年 | 40篇 |
1979年 | 22篇 |
1978年 | 22篇 |
1977年 | 111篇 |
1976年 | 267篇 |
1975年 | 14篇 |
1973年 | 9篇 |
排序方式: 共有9222条查询结果,搜索用时 15 毫秒
51.
52.
53.
AL Lindstrom SL Erlandsen JH Kersey CA Pennell 《Canadian Metallurgical Quarterly》1997,90(6):2323-2334
Vascular leak syndrome (VLS) is the dose-limiting toxicity observed in clinical trials of immunotoxins containing ricin toxin A chain (RTA). RTA itself is thought to cause VLS by damaging vascular endothelial cells, but the exact mechanism remains unclear. This is partially due to the paucity of appropriate models. To study VLS, we developed an in vitro model in which human umbilical vein-derived endothelial cells were first grown to confluence on microporous supports and then cultured under low pressure in the presence or absence of RTA. Endothelial cell barrier function was assessed by measuring the volume of fluid that passed through each monolayer per unit time. We found that RTA significantly increased monolayer permeability at times and concentrations consistent with the onset of VLS in patients treated with RTA-based immunotoxins. Scanning electron microscopy showed that intercellular gaps formed in endothelial monolayers exposed to RTA. Intercellular gap formation followed endothelial cell death caused by the enzymatic activity of RTA. We conclude that RTA is directly toxic to endothelial cells in vitro and speculate that this contributes to VLS in vivo. 相似文献
54.
L Struillou M Fiks-Sigaud JH Barrier E Blat G Magadur-Joly 《Canadian Metallurgical Quarterly》1993,60(7-8):524-526
The authors report an exceedingly rare complication of rheumatoid arthritis, i.e. acquired hemophilia due to anti-factor VIII autoantibody production. Treatment with intravenous immune globulin ensured control of hemorrhagic manifestations by inducing a transient rise in factor VIII level. 相似文献
55.
56.
57.
The incidence of stress fractures is increasing among competitive and recreational athletes as well as among children and the elderly. By understanding the continuum of bone's response to stress and maintaining an appropriate index of suspicion, the health care provider can diagnose these injuries appropriately. An accurate history and examination is essential and will differentiate stress fractures from other stress reactions. The more common stress fractures are discussed. 相似文献
58.
The purpose of this study was to identify family physicians' firearm safety counseling beliefs and behaviors. A survey was mailed to a random sample of 600 members of the American Academy of Family Physicians. A three wave mailing technique was used to maximize the response rate and yielded 271 usable surveys (55% response rate). Outcome measures included training experience in firearm safety counseling, the prevalence of firearm safety counseling by family physicians, and their perceptions regarding such counseling. The majority (78%) of family physicians lacked formal training on how to counsel patients about firearm safety and 49% believed more time should be spent in residency programs on firearm safety counseling. The majority (84%) of respondents never or rarely counseled patients on firearm safety and 50% believed firearm safety counseling should be a low priority in their delivery of primary care. The majority of respondents did not regularly counsel patients about firearm safety, did not believe firearm safety counseling should be a priority, and did not believe firearm safety counseling would be effective in reducing firearm-related trauma. 相似文献
59.
This concerns a patient with compression myelopathy following passive hyperextension of the cervical spine during a dental procedure. Although he had been asymptomatic prior to the procedure, subsequent cervical spinal imaging revealed advanced spondylosis and spinal stenosis. Spinal stenosis is often asymptomatic for a long time. However, when radiculomyelopathy occurs after minor trauma to the head or neck, the patient is often found to have spinal stenosis. Specifically, hyperextension of a cervical spine with spondylotic changes can lead to compression myelopathy. Acquired spinal stenosis correlates positively with aging. As the size of the elderly population continues to increase the prevalence of cervical spondylotic radiculo-myelopathy will likely increase as well. Since appropriate precautions against potential neurologic damage can be undertaken, we suggest radiographic screening for pre-existing spinal stenosis prior to a procedure requiring hyperextension of the neck. Preventive measures for individuals with asymptomatic spondylotic changes and education of all health-care professionals to avoid abrupt or prolonged hyperextension of the cervical spine is emphasized. 相似文献
60.
ME Goldberg BW Lex NK Mello JH Mendelson TA Bower 《Canadian Metallurgical Quarterly》1996,66(2):228-238
Research on achievement goal orientation in sport has relied primarily on traditional statistical methodology to examine group mean differences. Unfortunately, examination of the measurement model is generally ignored prior to means testing. This study reports an application of structural equation modeling (SEM) in testing measurement invariance and latent mean structure of the Task and Ego Orientation in Sport Questionnaire (TEOSQ; Duda & Nicholls, 1989) using male and female college students. A confirmatory factor analysis for testing invariance revealed invariant measurement properties and factor structures across gender, indicating that task and ego orientation are similarly conceptualized by male and female students. Subsequent testing of latent mean structures, however, showed significant gender differences with respect to ego orientation, but no difference in task orientation. The SEM procedures used in the present study demonstrate additional construct validity and internal consistency reliability for the TEOSQ and, by confirming its factor structure, provide a sound psychometric basis for its continued use in substantive studies focusing on the comparison of achievement goal orientation across gender. 相似文献