全文获取类型
收费全文 | 429048篇 |
免费 | 7370篇 |
国内免费 | 1697篇 |
专业分类
电工技术 | 8120篇 |
综合类 | 891篇 |
化学工业 | 65132篇 |
金属工艺 | 14686篇 |
机械仪表 | 12468篇 |
建筑科学 | 12400篇 |
矿业工程 | 1048篇 |
能源动力 | 11595篇 |
轻工业 | 45424篇 |
水利工程 | 3521篇 |
石油天然气 | 2003篇 |
武器工业 | 40篇 |
无线电 | 57189篇 |
一般工业技术 | 78769篇 |
冶金工业 | 77981篇 |
原子能技术 | 5693篇 |
自动化技术 | 41155篇 |
出版年
2021年 | 3095篇 |
2020年 | 2047篇 |
2019年 | 2736篇 |
2018年 | 4170篇 |
2017年 | 4217篇 |
2016年 | 4507篇 |
2015年 | 3744篇 |
2014年 | 6191篇 |
2013年 | 20112篇 |
2012年 | 10895篇 |
2011年 | 15502篇 |
2010年 | 11918篇 |
2009年 | 13556篇 |
2008年 | 14597篇 |
2007年 | 14958篇 |
2006年 | 13344篇 |
2005年 | 12425篇 |
2004年 | 12150篇 |
2003年 | 12079篇 |
2002年 | 12000篇 |
2001年 | 12051篇 |
2000年 | 10752篇 |
1999年 | 11188篇 |
1998年 | 25038篇 |
1997年 | 18281篇 |
1996年 | 14399篇 |
1995年 | 11305篇 |
1994年 | 10016篇 |
1993年 | 9607篇 |
1992年 | 7251篇 |
1991年 | 6888篇 |
1990年 | 6486篇 |
1989年 | 6196篇 |
1988年 | 5956篇 |
1987年 | 4956篇 |
1986年 | 4919篇 |
1985年 | 6072篇 |
1984年 | 5661篇 |
1983年 | 4900篇 |
1982年 | 4550篇 |
1981年 | 4520篇 |
1980年 | 4279篇 |
1979年 | 4124篇 |
1978年 | 3810篇 |
1977年 | 4616篇 |
1976年 | 6237篇 |
1975年 | 3151篇 |
1974年 | 3030篇 |
1973年 | 2928篇 |
1972年 | 2339篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
A Stimulation Method to Assess the Contractile Status of the Lumbar Extensors in a Seated Posture
下载免费PDF全文
![点击此处可从《人机工程学与制造业中的人性因素》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The purpose of present study was to develop and evaluate methods to assess stimulation responses of the lumbar extensors, as part of a longer‐term goal of detecting fatigue during prolonged sitting. Three stimulation frequencies (2, 5, and 8 Hz) were tested in separate stages, which include 3 stimulation trains and 4 sampling blocks. Repeated measures analyses of variance were used to determine whether any significant differences in mean stimulation responses occurred with respect to stimulation frequency, sampling block, and stimulation train. Reliability of measured stimulation responses was assessed within and between sampling blocks using intraclass correlation coefficients. Stimulation frequencies significantly affected the stimulation responses and time‐to‐potentiation differed between the 3 stimulation frequencies; it was highest for 2 Hz stimulation. All 3 stimulation frequencies resulted in excellent reliability within and between sampling blocks. Use of the current protocol at 2 Hz is recommended as appropriate to measure the lumbar extensors status during prolonged sitting. 相似文献
95.
D. Solís-Cortés E. Navarrete-Astorga J.L. Costa-Krämer J. Salguero-Fernandez R. Schrebler D. Leinen E.A. Dalchiele J.R. Ramos-Barrado F. Martín 《Ceramics International》2019,45(5):5577-5587
C-axis textured thin films of gallium-doped indium zinc oxide (GIZO) with a 2% ratio of Ga/Zn, were obtained via RF-magnetron sputtering with high transparency and electrical conductivity. A Box-Behnken response surface design was used to evaluate the effects of the deposition parameters (In2O3 target power, deposition time, and substrate temperature) on the chemical composition, optical, electrical, and structural properties of the GIZO films. The optical constants and the electrical properties were obtained using optical models. The GIZO stoichiometry, and therefore the In/Zn atomic ratio, affected the crystallinity, crystalline parameters, band gap, and charge carrier mobility of the GIZO films. The charge carrier density was related to the change in the crystalline parameters of the hexagonal structure and the In/Zn atomic ratio. The best electrical conductivity values (1.75?×?103 Ω?1 cm?1) were obtained for GIZO films with In/Zn ratio ≥?1. Several figures of merit (FOM) defined for the visible and solar regions were comparatively used to select the optimal In/Zn atomic ratio that provided the best balance between the conductivity and the transparency. The optimal In/Zn ratio was in a range of 0.85–0.90 for the GIZO films. 相似文献
96.
Titania-based ceramics with adjustable anatase-rutile fractions were obtained by milling of anatase, quartz and corundum precursors, uniaxial pressing and firing at 1100?°C. The influence of silica and alumina, combined with milling time and compaction pressure, was studied by design of experiments. The L9 orthogonal array with a three-level noise factor was employed. Firing of pure titania at 1100?°C yielded complete anatase to rutile transformation (ART), whereas stabilized samples show that an optimum amount of 9% silica and 33% alumina reduces phase transformation to only about 5?wt% rutile. An extended correlation matrix combined with analysis of variance (ANOVA) was applied to assess the combined effects of quartz, alumina, milling time and uniaxial compressing pressure on relative density, and anatase to rutile transformation. Results show absence of ART after milling, and controlled partial conversion of anatase to rutile after firing. Very good fitting was obtained by multivariate analysis on considering first and second order terms for dependence on silica contents and interactions between silica and each of the remaining factors, including milling time. This empirical dependence could be interpreted on a sound physicochemical basis, allowing the prediction of suitable compositions and processing conditions to obtain rutile-free samples by conventional ceramic processing, and to design ceramic samples with controlled fractions of anatase and rutile. 相似文献
97.
Load testing of applications is an important and costly activity for software provider companies. Classical solutions are very difficult to set up statically, and their cost is prohibitive in terms of both human and hardware resources. Virtualized cloud computing platforms provide new opportunities for stressing an application's scalability, by providing a large range of flexible and less expensive (pay‐per‐use model) computation units. On the basis of these advantages, load testing solutions could be provided on demand in the cloud. This paper describes a Benchmark‐as‐a‐Service solution that automatically scales the load injection platform and facilitates its setup according to load profiles. Our approach is based on: (i) virtualization of the benchmarking platform to create self‐scaling injectors; (ii) online calibration to characterize the injector's capacity and impact on the benched application; and (iii) a provisioning solution to appropriately scale the load injection platform ahead of time. We also report experiments on a benchmark illustrating the benefits of this system in terms of cost and resource reductions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
98.
Gina Cavaliere Giovanna Trinchese Nadia Musco Federico Infascelli Chiara De Filippo Vincenzo Mastellone Valeria Maria Morittu Pietro Lombardi Raffaella Tudisco Micaela Grossi Vincenzo Monda Monica I. Cutrignelli Antonietta Messina Serena Calabrò Heleena B. Moni Luigi Stradella Giovanni Messina Marcellino Monda Maria Pina Mollica 《Journal of dairy science》2018,101(3):1843-1851
Excessive energy intake may evoke complex biochemical processes characterized by inflammation, oxidative stress, and impairment of mitochondrial function that represent the main factors underlying noncommunicable diseases. Because cow milk is widely used for human nutrition and in food industry processing, the nutritional quality of milk is of special interest with respect to human health. In our study, we analyzed milk produced by dairy cows fed a diet characterized by a high forage:concentrate ratio (high forage milk, HFM). In view of the low n-6:n-3 ratio and high content of conjugated linoleic acid of HFM, we studied the effects of this milk on lipid metabolism, inflammation, mitochondrial function, and oxidative stress in a rat model. To this end, we supplemented for 4 wk the diet of male Wistar rats with HFM and with an isocaloric amount (82 kJ, 22 mL/d) of milk obtained from cows fed a diet with low forage:concentrate ratio, and analyzed the metabolic parameters of the animals. Our results indicate that HFM may positively affect lipid metabolism, leptin:adiponectin ratio, inflammation, mitochondrial function, and oxidative stress, providing the first evidence of the beneficial effects of HFM on rat metabolism. 相似文献
99.
100.