全文获取类型
收费全文 | 95061篇 |
免费 | 10774篇 |
国内免费 | 6634篇 |
专业分类
电工技术 | 8239篇 |
技术理论 | 1篇 |
综合类 | 9518篇 |
化学工业 | 11131篇 |
金属工艺 | 6079篇 |
机械仪表 | 5895篇 |
建筑科学 | 6195篇 |
矿业工程 | 3927篇 |
能源动力 | 2529篇 |
轻工业 | 10936篇 |
水利工程 | 3066篇 |
石油天然气 | 3211篇 |
武器工业 | 1595篇 |
无线电 | 8368篇 |
一般工业技术 | 7134篇 |
冶金工业 | 11145篇 |
原子能技术 | 1469篇 |
自动化技术 | 12031篇 |
出版年
2024年 | 648篇 |
2023年 | 1653篇 |
2022年 | 3807篇 |
2021年 | 4784篇 |
2020年 | 3445篇 |
2019年 | 2348篇 |
2018年 | 2563篇 |
2017年 | 2867篇 |
2016年 | 2638篇 |
2015年 | 4161篇 |
2014年 | 5072篇 |
2013年 | 6008篇 |
2012年 | 7482篇 |
2011年 | 7687篇 |
2010年 | 7353篇 |
2009年 | 6686篇 |
2008年 | 6795篇 |
2007年 | 6586篇 |
2006年 | 5644篇 |
2005年 | 4358篇 |
2004年 | 3223篇 |
2003年 | 2203篇 |
2002年 | 1953篇 |
2001年 | 1808篇 |
2000年 | 1469篇 |
1999年 | 775篇 |
1998年 | 2735篇 |
1997年 | 1570篇 |
1996年 | 1015篇 |
1995年 | 594篇 |
1994年 | 494篇 |
1993年 | 546篇 |
1992年 | 113篇 |
1991年 | 118篇 |
1990年 | 119篇 |
1989年 | 117篇 |
1988年 | 93篇 |
1987年 | 84篇 |
1986年 | 78篇 |
1985年 | 53篇 |
1983年 | 17篇 |
1982年 | 39篇 |
1981年 | 41篇 |
1980年 | 72篇 |
1979年 | 17篇 |
1977年 | 158篇 |
1976年 | 283篇 |
1975年 | 13篇 |
1959年 | 36篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
在10 ̄(-5)_eV-20MeV中子能量范围内对天然汞的中子核数据进行评价。评价内容包括总的、弹性、去弹、总非弹、30条分立能级、连续非弹、(n,2n)、(n,3n,)、(n,n'P)、(n,n'α)、(n,P)、(n,α)、(n,d)、(n,t)和(n,γ)截面;次级中子角分布;双微分截面(DDCS);γ射线产生数据等。评价根据有效实验数据(至1993年)和UNF-92 ̄[1]理论计算。评价数据以ENDF/B6格式录入中国评价核数据库CENDL-2.1版(MAT=1800),并提供核工程有关部门使用。 相似文献
23.
MA Heneghan B Cleary M Murray TA O'Gorman CF McCarthy 《Canadian Metallurgical Quarterly》1998,43(6):1356-1361
Thromboembolic events frequently complicate the clinical course of patients with inflammatory bowel disease (IBD). Hereditary thrombophilia may contribute to this tendency. Resistance to activated protein C is the most recently described thrombophilic state and may account for up to 40% of patients with thrombophilia. Thirty-seven patients with IBD were studied (mean age 44 years, range 18-82 years). Three patients had a history of thrombotic episodes. The 37 controls included 23 men and 17 women (mean age 48 years, range 16-89 years). Disease activity was assessed using the Harvey Bradshaw index for patients with Crohn's disease and the Truelove and Witts grading system for patients with ulcerative colitis. Levels of fibrinogen, antithrombin III (ATIII), protein C, protein S, activated protein C resistance (APCR), and the presence of a lupus anticoagulant (LA) were determined. Median ATIII levels in patients with IBD were significantly lower than controls (98% vs 106%, P = 0.007), while fibrinogen was elevated (4.2 vs 3.3 g/liter, P = 0.026) despite quiescent disease activity. LA was detected in 7/37 patients in the IBD group compared to 0/37 controls. (chi2 = 5.68, P = 0.017). No significant difference was observed in levels of inherited thrombophilic factors and in particular APCR between IBD patients and controls. In conclusion, the presence of inherited thrombophilic defects, in particular APCR, is uncommon in patients with IBD and does not merit routine screening. 相似文献
24.
25.
26.
27.
MA Dekich 《Canadian Metallurgical Quarterly》1998,77(8):1176-1180
The commercial broiler industry is a modern day agricultural success due to popular consumer demand, healthy flocks, and least cost production. Preventive medicine is the key for economical control of disease in integrated broiler companies, and includes quarantine-eradication, controlled-exposure, and preventive feed medication. Respiratory and enteric diseases present a continuing, potential threat for economic loss. Most exotic and egg-transmitted poultry diseases have been controlled by reduction or eradication policies. Endemic diseases are controlled by mass vaccination and preventive feed medication. Improvements in genetics, housing, equipment, and disease surveillance has allowed continued improvements in disease prevention. Attention to detail and management of risk is crucial to industry success. With fast industry growth and market maturity of the broiler industry, new challenges have risen. These challenges include increased poultry house density, increasing economic pressures, changing industry attitudes, and increased governmental regulations that will strain the continued success of today's control strategies. 相似文献
28.
MC Lipman D Stobbs S Madge R Miller MA Johnson 《Canadian Metallurgical Quarterly》1998,114(1):284-290
STUDY OBJECTIVES: Asymptomatic HIV-infected individuals are increasingly recruited for studies involving invasive procedures such as bronchoscopy. We sought to determine the response to and outcome of a request for a research bronchoscopy in HIV-positive individuals with no respiratory disease, and whether this would adversely affect future decisions to have a medically indicated bronchoscopy. DESIGN AND SETTING: Prospective, semistructured, questionnaire-based study in a London teaching hospital HIV outpatient clinic. PARTICIPANTS: One hundred and seven consecutive HIV-infected eligible individuals. Thirty-one healthy volunteers served as a control group for the subjective response to bronchoscopy. MAIN OUTCOME MEASURES: Subjects' attitudes and responses to requests for bronchoscopy and subsequent behavior when they required medically indicated bronchoscopy. RESULTS: Seventy-five patients (70%) agreed to the procedure in principle, predominantly for altruistic reasons. Thirty-nine subjects underwent bronchoscopy. Five percent found it worse than expected; and 79% agreed to another research bronchoscopy (performed in 11 subjects approximately 2 years later). All patients said they would undergo bronchoscopy again for diagnostic purposes (required in seven during the study). When compared to a healthy volunteer population within the same study, postbronchoscopy symptoms were similar in frequency although somewhat different in nature. Subjects felt that a clear explanation of what was involved enhanced their participation in this research. CONCLUSIONS: Invasive research procedures such as bronchoscopy can be performed and are repeatable in a healthy HIV-infected population. Performance of procedures for research purposes does not appear to adversely affect future health-care decisions. 相似文献
29.
研究了温度及气体压力对漂移室(工作于正比区)气体放大倍数的影响,温度和气体压力的变化范围分别是5 ̄40℃及90 ̄105kPa。用实验数据拟合得到了函数关系并测量了几种饱和度下函数中的参数值。 相似文献
30.
介绍了工作流的应用背景,分析了某校教务系统中采用的工作流技术的原理和设计思想。提出可编辑、管理和监控的工作流模型,并重点介绍了工作流程运行机制。工作流技术使单位内部业务流程自动化,信息流转逐步实现无纸化。利用其图形化定义流程的功能,在办公流程越来越严谨的前提下,办公效率也大幅提高。某校在教务系统中运用了工作流技术,取得了良好的效果。 相似文献