全文获取类型
收费全文 | 2821篇 |
免费 | 59篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 13篇 |
综合类 | 4篇 |
化学工业 | 246篇 |
金属工艺 | 30篇 |
机械仪表 | 34篇 |
建筑科学 | 46篇 |
矿业工程 | 4篇 |
能源动力 | 57篇 |
轻工业 | 67篇 |
水利工程 | 32篇 |
石油天然气 | 33篇 |
无线电 | 71篇 |
一般工业技术 | 198篇 |
冶金工业 | 1921篇 |
原子能技术 | 12篇 |
自动化技术 | 131篇 |
出版年
2023年 | 9篇 |
2022年 | 25篇 |
2021年 | 49篇 |
2020年 | 38篇 |
2019年 | 51篇 |
2018年 | 83篇 |
2017年 | 53篇 |
2016年 | 73篇 |
2015年 | 43篇 |
2014年 | 51篇 |
2013年 | 106篇 |
2012年 | 58篇 |
2011年 | 55篇 |
2010年 | 59篇 |
2009年 | 39篇 |
2008年 | 27篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 15篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 56篇 |
1998年 | 666篇 |
1997年 | 303篇 |
1996年 | 223篇 |
1995年 | 117篇 |
1994年 | 102篇 |
1993年 | 123篇 |
1992年 | 14篇 |
1991年 | 25篇 |
1990年 | 32篇 |
1989年 | 34篇 |
1988年 | 35篇 |
1987年 | 28篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 15篇 |
1980年 | 15篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 26篇 |
1976年 | 105篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有2899条查询结果,搜索用时 15 毫秒
31.
JF Aloia I Zanzi K Ellis J Jowsey M Roginsky S Wallach SH Cohn 《Canadian Metallurgical Quarterly》1976,43(5):992-999
The effect of chronic administration of growth hormone (GH) to osteoporotic patients was studied using the techniques of total body neutron activation analysis, whole body counting, calcium tracer kinetics, photon absorptiometry, quantitative microradiography, and urinary hydroxyproline. Two dosage schedules were utilized for six months each: 2 units daily and 0.2 w3/4 units of GH daily (where W represents body weight expressed in kg). The lower dosage (2 units) did not produce any appreciable change in the indices studied. Following the higher dose, no evidence of any anabolic effect was apparent in most patients (i.e., no increase in total body levels of Ca, Na, K, P, or Cl). Increases were noted in the urinary calcium excretion rate and in the urinary hydroxyproline excretion. Bone mineral content decreased. The bone biopsies displayed an increase in bone formation and resorption surfaces in response to treatment, but these changes were not statistically significant. It may be concluded that under the conditions of this study, GH administration did not result in an increment in skeletal mass. Several side effects that are characteristic of acromegaly were observed, including hyperglycemia, hypertension, arthralgia, and the carpal tunnel syndrome. Because of the lack of demonstrated benefit and the associated complications of therapy, GH administration does not appear to be of value in the treatment of osteoporosis. 相似文献
32.
Nitrous oxide produced a dose-related "analgesia" in mice (median effective dose, 55 percent). The analgesia was evaluated by means of a phenylquinone writhing test. Narcotic antagonists or chronic morphinization reduced nitrous oxide analgesia. Either nitrous oxide releases an endogenous analgesic or narcotic antagonists have analgesic antagonist properties heretofore unappreciated. 相似文献
33.
34.
35.
36.
Mahmoud Omid Mahmoud SoltaniMohammad Hadi Dehrouyeh Seyed Saeid MohtasebiHojat Ahmadi 《Journal of food engineering》2013
The main purpose of this research was design and development of an intelligent system based on combined fuzzy logic and machine vision techniques for grading of egg using parameters such as defects and size of eggs. The detected defects were internal blood spots, cracks and breakages of eggshell. The Hue-Saturation-Value (HSV) color space was found useful in obtaining visual features during Image Processing (IP) stage. The fuzzy inference system (FIS) was designed based on triangular and trapezoidal membership functions, fuzzy rules with logical operator of AND inference system of Mamdani and method of center average for defuzzifier. The evaluation results of IP algorithms showed that use of IP technique has good performance for defects and size detection. The Correct Classification rate (CCR) was 95% for size detection, 94.5% for crack detection and 98% for breakage detection. The overall accuracy FIS model in grading of the eggs was 95.4. 相似文献
37.
Maryam Ghaderi‐Ghahfarokhi Amin Yousefvand Hassan Ahmadi Gavlighi Mehdi Zarei 《International Journal of Dairy Technology》2021,74(1):161-169
This study investigates the effect of supplementation of tragacanth gum (GT, 0.05% w/v), low molecular weight gum tragacanth (LMWGT, 0.5% w/v) and inulin (0.5% w/v) on the viability of Bifidobacterium bifidum and the quality parameters of low‐fat yoghurt during a three‐week storage period. The count of probiotics was found to be 7.8 log cfu/g in inulin, and LMWGT enriched yoghurts at the end of the storage period. The minimum water holding capacity and the maximum syneresis values were also obtained in the low‐fat yoghurt enriched with GT throughout the storage time. The samples containing inulin and LMWGT revealed sensory attributes that were judged superior compared to those in GT. 相似文献
38.
39.
40.
Thermal,mechanical, and corrosion resistance properties of vinyl ester/clay nanocomposites for the matrix of carbon fiber‐reinforced composites exposed to electron beam 下载免费PDF全文
Seyed Mohammad Razavi Negar Dehghanpour Seyed Javad Ahmadi Mahdi Rajabi Hamaneh 《应用聚合物科学杂志》2015,132(33)
Vinyl ester/clay nanocomposites with 1, 3, and 5% nanoclay contents were prepared. X‐ray diffractography patterns and Scanning Electron micrographs showed that nanocomposites with the exfoliated structure were formed. Thermogravimetric analysis, water absorption test, and Tafel polarization method, respectively, revealed the improvements in thermal resistance, water barrier properties, and corrosion resistance properties of the samples with an increase in the amount of the incorporated nanoclay. Tensile tests showed that nanoclay also enhanced the mechanical properties of the polymer, so that the tensile strength of the samples with 5% nanoclay was more than 3 times higher than tensile strength of pure vinyl ester samples. Overall, the best properties were observed for the samples containing 5% nanoclay. Pure vinyl ester and nanocomposite with 5% nanoclay content were exposed to the electron beam radiation and their mechanical properties improved up to 500 kGy irradiation dose. Finally, pure vinyl ester and vinyl ester/nanoclay (5%) matrixes were reinforced with carbon fiber and the effect of electron beam irradiation on their mechanical properties was examined. The tensile strength and the modulus of the samples initially increased after exposure to the radiation doses up to 500 kGy and then a decrease was observed as the irradiation dose rose to 1000 kGy. Moreover, nanoclay moderated the effect of the irradiation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42393. 相似文献