全文获取类型
收费全文 | 2962篇 |
免费 | 130篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 43篇 |
综合类 | 12篇 |
化学工业 | 498篇 |
金属工艺 | 114篇 |
机械仪表 | 84篇 |
建筑科学 | 141篇 |
矿业工程 | 9篇 |
能源动力 | 58篇 |
轻工业 | 210篇 |
水利工程 | 25篇 |
石油天然气 | 28篇 |
无线电 | 237篇 |
一般工业技术 | 447篇 |
冶金工业 | 830篇 |
原子能技术 | 85篇 |
自动化技术 | 290篇 |
出版年
2022年 | 33篇 |
2021年 | 49篇 |
2020年 | 21篇 |
2019年 | 28篇 |
2018年 | 46篇 |
2017年 | 50篇 |
2016年 | 48篇 |
2015年 | 61篇 |
2014年 | 49篇 |
2013年 | 130篇 |
2012年 | 83篇 |
2011年 | 150篇 |
2010年 | 96篇 |
2009年 | 90篇 |
2008年 | 146篇 |
2007年 | 123篇 |
2006年 | 125篇 |
2005年 | 101篇 |
2004年 | 78篇 |
2003年 | 91篇 |
2002年 | 62篇 |
2001年 | 61篇 |
2000年 | 52篇 |
1999年 | 71篇 |
1998年 | 211篇 |
1997年 | 115篇 |
1996年 | 91篇 |
1995年 | 75篇 |
1994年 | 58篇 |
1993年 | 53篇 |
1992年 | 40篇 |
1991年 | 33篇 |
1990年 | 36篇 |
1989年 | 28篇 |
1988年 | 54篇 |
1987年 | 50篇 |
1986年 | 35篇 |
1985年 | 31篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 25篇 |
1978年 | 13篇 |
1977年 | 33篇 |
1976年 | 36篇 |
1974年 | 12篇 |
1971年 | 14篇 |
1970年 | 16篇 |
排序方式: 共有3111条查询结果,搜索用时 15 毫秒
1.
Lance Charles E.; Lambert Tracy A.; Gewin Amanda G.; Lievens Filip; Conway James M. 《Canadian Metallurgical Quarterly》2004,89(2):377
The authors reanalyzed assessment center (AC) multitrait-multimethod (MTMM) matrices containing correlations among postexercise dimension ratings (PEDRs) reported by F. Lievens and J. M. Conway (2001). Unlike F. Lievens and J. M. Conway, who used a correlated dimension-correlated uniqueness model, we used a different set of confirmatory-factor-analysis-based models (1-dimension-correlated Exercise and 1-dimension-correlated uniqueness models) to estimate dimension and exercise variance components in AC PEDRs. Results of reanalyses suggest that, consistent with previous narrative reviews, exercise variance components dominate over dimension variance components after all. Implications for AC construct validity and possible redirections of research on the validity of ACs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
2.
X. Wang S. B. Lambert 《Fatigue & Fracture of Engineering Materials & Structures》1997,20(12):1637-1655
Abstract— A Fourier series approach is proposed to calculate stress intensity factors using weight functions for semi-elliptical surface cracks in flat plates subjected to two-dimensional stress distributions. The weight functions were derived from reference stress intensity factors obtained by three-dimensional finite element analyses. The close form weight functions derived are suitable for the calculation of stress intensity factors for semi-elliptical surface cracks in flat plates under two-dimensional stress distributions with the crack aspect ratio in the range of 0.1 ≤ a/c ≤ 1 and relative depth in the range of 0 ≤ a/t ≤ 0.8. Solutions were verified using several two-dimensional non-linear stress distributions; the maximum difference being 6%. 相似文献
3.
Dean Gillette 《Information Systems Management》1991,8(2):76-79
As most IS managers know, time is often wasted during most business meetings. As technological advances in the various types of teleconferencing systems continue, teleconferencing will serve as the preferred method of conducting meetings because of the resulting time and cost savings. 相似文献
4.
Dean Gillette 《Information Systems Management》1991,8(4):65-67
Designing a geographically extensive corporate network at the lowest cost means dealing with the vagaries of handling multiple carriers and widely varying levels of service. Further complicating matters are tariff structures that often dictate optimum corporate network infrastructures. This column reviews some of the available and emerging services and the best network structure options. 相似文献
5.
Two lignite samples, Beulah No. 3 and Big Brown No. 1, were liquefied at 420 °C using H2 and synthesis gas to determine the optimum beneficial amount of H2S in the batch autoclave reactor. Under the conditions employed, 50–100 psi partial pressure of H2S, nominally 4–10 wt% of daf lignite, was optimum for both samples. Synthesis gas outperformed H2 with and without H2S for the liquefaction of the two coals. 相似文献
6.
O Bernard B Chachuat A Hélias B Le Dantec B Sialve J-P Steyer L Lardon P Neveu S Lambert J Gallop M Dixon P Ratini A Quintabà S Frattesi J M Lema E Roca G Ruiz J Rodriguez A Franco P Vanrolleghem U Zaher D J W De Pauw K De Neve K Lievens D Dochaine O Schoefs H Fibrianto R Farina V Alcaraz Gonzalez V Gonzalez Alvarez P Lemaire J A Martinez F Esandi O Duclaud J F Lavigne 《Water science and technology》2005,52(1-2):457-464
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem. 相似文献
7.
Geoffrey Rowden Shirley Dean James Campbell Philip Belitsky 《Microscopy research and technique》1985,2(6):547-555
Aspiration biopsy of tumors and transplanted organs is a popular atraumatic method for diagnosis and also for the management of patients. Apart from the cytological analyses, it is clear that large aggregates of cells are obtained and these may be examined by electron microscopy. A study was carried out with dogs to assess the yield of intact glomeruli and tubules, resulting from a standard fine-needle aspiration procedure. Employing a 20-gauge needle, yields of approximately ten intact glomeruli were obtained with a tissue processing protocol that utilized filtration through a nylon mesh and backwashing, to resuspend the trapped aggregates. Processing for electron microscopy was carried out in microcentrifuge tubes. The ultrastructural preservation was excellent and the extension of these studies to investigations of not only renal transplantation, but also for diagnosis in human renal diseases of a broad spectrum, is suggested. 相似文献
8.
Somatotrophs become a significant population by day 16 of chicken embryonic development. We have previously demonstrated that an earlier induction of GH cell differentiation is possible with the addition of day 16 embryonic serum to cultures of day 12 pituitary cells, an age when somatotrophs are rare. The present study was designed to identify the blood-borne signal(s) responsible for the serum activity, using reverse hemolytic plaque assays to identify individual GH-secreting cells. The activity was found to be a heat-stable, ether-soluble compound(s) that is bound or inhibited by a trypsin-sensitive protein. The extent of GH cell differentiation was greater (P < 0.05; n = 3) in response to the ether phases of heated day 16 (14.1 +/- 0.4% of all cells) and day 12 sera (9.3 +/- 0.4%) than with untreated serum from days 16 and 12 (6.1 +/- 0.4% and 0.82 +/- 0.4%, respectively). Furthermore, ether-extracted day 16 serum was more effective than ether-extracted day 12 serum, which was also different from basal (0.85 +/- 0.4%; P < 0.05). Based on this biochemical profile, the abilities of various steroids to stimulate differentiation were tested. Three steroids were found to stimulate somatotroph differentiation in vitro: 17beta-estradiol, corticosterone, and progesterone. However, the estradiol receptor antagonist, tamoxifen, while abolishing the effect of estradiol, had no effect on the induction of differentiation by day 16 serum. In contrast, RU486, a specific glucocorticoid receptor antagonist in chickens, blocked the stimulatory effects of corticosterone, progesterone, and day 16 serum on somatotroph differentiation. We next tested whether the active compound in day 16 embryonic serum was corticosterone, the predominant glucocorticoid in chickens. Incubation of day 16 serum with corticosterone antiserum, but not control antiserum, suppressed day 16 serum-induced GH cell differentiation. Therefore, we conclude that corticosterone is the blood-borne signal capable of stimulating somatotroph differentiation in vitro. The present findings together with previous reports indicate that somatotroph differentiation during embryonic development may result from an increase in circulating glucocorticoid concentrations. 相似文献
9.
Zemon S. Pedersen B. Lambert G. Miniscalco W.J. Hall B.T. Folweiler R.C. Thompson B.A. Andrews L.J. 《Photonics Technology Letters, IEEE》1992,4(3):244-247
The performance of Nd3+-doped fibre amplifiers is limited by strong excited-state absorption (ESA) of the signal, and, even for fluorozirconate glasses, ESA prevents the important region below 1320 nm from being used. To quantify this limitation and explore alternative host materials, ESA and stimulated-emission cross sections have been measured for a representative group of glass compositions. These parameters have been used in an accurate fiber-amplifier model to provide the first quantitative comparisons of performance for Nd3+ -doped glasses in the 1300-nm band as a function of host 相似文献
10.