全文获取类型
收费全文 | 8140篇 |
免费 | 133篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 116篇 |
综合类 | 3篇 |
化学工业 | 982篇 |
金属工艺 | 97篇 |
机械仪表 | 144篇 |
建筑科学 | 263篇 |
矿业工程 | 16篇 |
能源动力 | 122篇 |
轻工业 | 487篇 |
水利工程 | 56篇 |
石油天然气 | 9篇 |
武器工业 | 1篇 |
无线电 | 693篇 |
一般工业技术 | 946篇 |
冶金工业 | 3608篇 |
原子能技术 | 70篇 |
自动化技术 | 675篇 |
出版年
2022年 | 37篇 |
2021年 | 43篇 |
2019年 | 40篇 |
2018年 | 77篇 |
2017年 | 56篇 |
2016年 | 67篇 |
2015年 | 72篇 |
2014年 | 97篇 |
2013年 | 259篇 |
2012年 | 159篇 |
2011年 | 196篇 |
2010年 | 142篇 |
2009年 | 157篇 |
2008年 | 199篇 |
2007年 | 201篇 |
2006年 | 199篇 |
2005年 | 194篇 |
2004年 | 176篇 |
2003年 | 156篇 |
2002年 | 146篇 |
2001年 | 145篇 |
2000年 | 150篇 |
1999年 | 187篇 |
1998年 | 984篇 |
1997年 | 558篇 |
1996年 | 422篇 |
1995年 | 255篇 |
1994年 | 243篇 |
1993年 | 238篇 |
1992年 | 133篇 |
1991年 | 121篇 |
1990年 | 107篇 |
1989年 | 117篇 |
1988年 | 122篇 |
1987年 | 113篇 |
1986年 | 120篇 |
1985年 | 136篇 |
1984年 | 105篇 |
1983年 | 80篇 |
1982年 | 97篇 |
1981年 | 92篇 |
1980年 | 83篇 |
1979年 | 72篇 |
1978年 | 73篇 |
1977年 | 122篇 |
1976年 | 242篇 |
1975年 | 40篇 |
1974年 | 42篇 |
1973年 | 51篇 |
1972年 | 43篇 |
排序方式: 共有8288条查询结果,搜索用时 14 毫秒
31.
Cuddihy P. Hinman R.T. Avestruz A. Lupton E.C. Livshin G. Rodriguez J.I. Leeb S.B. Clark C.M. Horvath K.J. Volicer L. Landfeldt B. Kay J. Kummerfeld R. Quigley A. West D. Apted T. Sinclair G. Haniff D.J. Kalawsky R. Atkins D. Lewin M. Brown S.J. Shahmehri N. Aberg J. Maciuszek D. Chisalita I. 《Pervasive Computing, IEEE》2004,3(2):48-50
This issue's Works in Progress department presents six abstracts for projects that are developing interesting solutions to the elderly's quality of life challenges. The first two abstracts discuss projects that will help provide the elderly with freedom and independence by instrumenting their environments with supportive technology. The next two abstracts discuss projects building specialized user interfaces for addressing some of the challenges associated with aging, such as vision impairment. The final two abstracts present projects that will aid independence for the elderly by providing remote monitoring and assistance. 相似文献
32.
Myers Mark G.; MacPherson Laura; McCarthy Denis M.; Brown Sandra A. 《Canadian Metallurgical Quarterly》2003,15(2):163
The goal of the present studies was to construct and validate a short form of the 50-item Smoking Consequences Questionnaire (SCQ; T. H. Brandon & T. B. Baker, 1991), a measure of smoking outcome expectancies. In Study 1, a 21-item short form (S-SCQ) was derived from a sample of 107 young adults previously treated for substance abuse. In Study 2, the measure was cross-validated on 125 adolescents in treatment for substance abuse. Confirmatory factor analyses revealed good model fit and factorial invariance for the 4 S-SCQ subscales across both samples. Validation analyses on each sample found that subscale scores generally correlated significantly with smoking-related variables. The present studies provide initial evidence for the utility of the S-SCQ when used with young adults and adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
Baeyer-Villiger monooxygenases (BVMOs) are enzymes able to perform highly regio-plus steroselective nucleophilic and electrophilic biooxygenations on various substrates. The resultant chiral products (lactones and sulfoxides) can be valuable for the chemoenzymatic synthesis of a wide range of useful compounds. Recent studies have provided a number of alternative active-site models that attempt to explain the exquisite and unusual selectivity of BVMOs. This article reviews some of the established applications, and considers the merits of the various predictive models. 相似文献
34.
Analysis of amino acids is complicated by treatment with ampicillin. High voltage electrophoresis, which is convenient for the qualitative assessment of metabolic diseases, yields smears of ampicillin that mask the bands of citrulline, homocitrulline, phenylalanine, cystine, and homocystine. The addition of penicillinase prior to high voltage electrophoresis eliminates ampicillin and other penicillins and reveals these key amino acids. 相似文献
35.
William C. Brown 《Solar Energy》1996,56(1):3-21
The history of wireless power transmission at microwave frequencies is reviewed with emphasis upon the time period starting with the post World War II efforts to use the new microwave technology developed during the war. A nationally televised demonstration of a microwave powered helicopter at the Spencer Laboratory of the Raytheon Co., in 1964 was the result of these early efforts and broadly introduced the concept of wireless power transmission to scientific and engineering communities and to the public. Subsequent development efforts centered on improving the efficiency of the interconversion of d.c. and microwave power at the ends of the system to reach a demonstrated overall d.c. to d.c. system efficiency of 54% in 1974. The response to the requirements of applications such as the Solar Power Satellite and high altitude microwave powered aircraft have changed the direction of technology development and greatly expanded the technology base. Recent and current efforts are centered on examining the use of higher frequencies than the baseline 2.45 GHz, and in reducing the system costs at 2.45 GHz. 相似文献
36.
Recent research suggests that implementing information systems presents considerable difficulties and that many implementations are total or partial failures. This paper argues that what both practitioners and students require are richer and more acceptable models of information systems implementation. Accordingly, case study data concerning the introduction of manufacturing resource planning (MRP II) are used to illustrate five patterns of behaviour (rites) which capture important social actions; and four components of changing psychological orientation. It is argued that appreciation of the rites and psychological developments identified here will support effective change programmes. Guidelines based on our model are provided for practitioners. 相似文献
37.
38.
LM Brown 《Canadian Metallurgical Quarterly》1993,154(1-2):43-46
Developmental alterations in N-methyl-D-aspartate (NMDA)-stimulated[3H]norepinephrine release from rat brain cortical and hippocampal slices were studied. NMDA (10-1000 microM) resulted in a concentration-dependent increase in [3H]norepinephrine efflux; maximal responses (% released) in the cortex were: (1.53 +/- 0.12, 3.68 +/- 0.20, 2.94 +/- 0.20, 4.60 +/- 0.28 and 5.28 +/- 0.33) and the hippocampal responses were: (1.90 +/- 0.18, 3.84 +/- 0.23, 3.60 +/- 0.28, 5.16 +/- 0.38 and 5.81 +/- 0.45) at varying postnatal ages (1, 7, 14, 21 and 90 days) respectively. Cortical tissue from 7-day-old pups exhibited a transient increase in maximal efflux and a decrease in EC50. These results indicated that developmental alterations in the NMDA receptor appear to be translated into differences in NMDA stimulated [3H]norepinephrine release. 相似文献
39.
We compared the effects of an allergen challenge on airway responsiveness to methacholine, the slope of the dose-response curve (DRC) and post-methacholine fall in forced vital capacity (FVC) or forced expiratory volume in 1 s (FEV1)/FVC, and determined whether any changes in these parameters were related to the presence and magnitude of the late asthmatic response (LAR) in mild stable asthma. Twenty-three allergic asthmatic subjects had an allergen challenge, preceded and followed 24 (n = 12) and/or 48 (n = 22) h later by a methacholine challenge. Sixteen subjects had a dual asthmatic response to the allergen. On the post-allergen methacholine challenge, as compared with the pre-allergen test, differences in mean fall in FVC or FEV1/FVC at 20% fall in FEV1 and the slope of the DRC did not achieve statistical significance, even in the group with LAR, which showed a significant increase in airway responsiveness at 24 h. There was, however, a correlation between allergen-induced changes in PC20 and (1) the change in post-methacholine FVC fall in the LAR group at 48 h, and (2) the change in the slope of the DRC in the early-asthmatic-response group at 24 h. In conclusion, allergen-challenge-induced changes in airway response to methacholine are heterogeneous among asthmatic subjects and although it may increase airway responsiveness (PC20), particularly in late responders, it minimally affects the other aspects of airway response to methacholine, suggesting that a more powerful or sustained allergic stimulus is required to modify the latter. 相似文献
40.