全文获取类型
收费全文 | 1282858篇 |
免费 | 83356篇 |
国内免费 | 48332篇 |
专业分类
电工技术 | 47591篇 |
综合类 | 21230篇 |
化学工业 | 190396篇 |
金属工艺 | 65209篇 |
机械仪表 | 38239篇 |
建筑科学 | 38804篇 |
矿业工程 | 18712篇 |
能源动力 | 36983篇 |
轻工业 | 114486篇 |
水利工程 | 18624篇 |
石油天然气 | 31615篇 |
武器工业 | 3558篇 |
无线电 | 154226篇 |
一般工业技术 | 240968篇 |
冶金工业 | 222673篇 |
原子能技术 | 23368篇 |
自动化技术 | 147864篇 |
出版年
2022年 | 10750篇 |
2021年 | 14454篇 |
2020年 | 15287篇 |
2019年 | 26769篇 |
2018年 | 34368篇 |
2017年 | 35714篇 |
2016年 | 36473篇 |
2015年 | 29950篇 |
2014年 | 35649篇 |
2013年 | 68423篇 |
2012年 | 44292篇 |
2011年 | 51464篇 |
2010年 | 42176篇 |
2009年 | 43100篇 |
2008年 | 42500篇 |
2007年 | 41801篇 |
2006年 | 36344篇 |
2005年 | 33178篇 |
2004年 | 35243篇 |
2003年 | 33390篇 |
2002年 | 32016篇 |
2001年 | 30538篇 |
2000年 | 28310篇 |
1999年 | 29598篇 |
1998年 | 67608篇 |
1997年 | 48957篇 |
1996年 | 38517篇 |
1995年 | 29940篇 |
1994年 | 26504篇 |
1993年 | 25796篇 |
1992年 | 19484篇 |
1991年 | 18016篇 |
1990年 | 17427篇 |
1989年 | 16839篇 |
1988年 | 15802篇 |
1987年 | 13609篇 |
1986年 | 13366篇 |
1985年 | 15401篇 |
1984年 | 14116篇 |
1983年 | 12846篇 |
1982年 | 11943篇 |
1981年 | 12081篇 |
1980年 | 11466篇 |
1979年 | 11306篇 |
1978年 | 10979篇 |
1977年 | 12846篇 |
1976年 | 17076篇 |
1975年 | 9675篇 |
1974年 | 9158篇 |
1973年 | 9165篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
R.N. ARNOLD K.K. SCHELLER S.C. ARP S.N. WILLIAMS D.M. SCHAEFER 《Journal of food science》1993,58(1):28-33
The effect of long-term feeding (252 days) of three supplemental levels of α-tocopheryl acetate (actual 0, 360 and 1290 IU/head/day) on meat quality was evaluated in Holstein and beef breed steers. Tissue vitamin E concentrations were increased by each increment of supplementation. The color display life of fresh beef under simulated retail conditions was extended 2 to 5 days by vitamin E and lipid oxidation was markedly reduced. Microbial population was not affected by level of supplementation. No deterioration in sensory quality occurred for steaks from supplemented steers that were displayed until the time steaks from unsupplemented steers discolored. 相似文献
992.
R. Borkowska J. Laskowski J. Płocharski J. Przyłuski W. Wieczorek 《Journal of Applied Electrochemistry》1993,23(10):991-995
Results for the performance of lithium/Mn02 batteries containing solid polymer electrolytes based on poly(ethylene oxide) blends with some acrylic derivatives are presented. The ionic conductivities of the electrolytes are promising for battery application. It was found, however, that interfacial phenomena impair the battery efficiency. Impedance spectroscopy shows resistive limitations at the anode interface of the batteries, caused either by formation of an electrically distinguishable resistive layer or by chemical interaction between the polymer and lithium, influencing, most probably, the kinetics of the lithium oxidation reaction. 相似文献
993.
T Takikawa H Hayashi N Nishimura M Yano T Isomura N Sakamoto 《Canadian Metallurgical Quarterly》1994,29(5):593-597
Chronic hepatitis C has been demonstrated to be associated with hepatic iron overload, and the hypothesis that the disease activity of hepatitis C is associated with iron cytotoxicity was tested in male volunteer blood donors. Sera with either antibody to hepatitis C virus or hepatitis B surface antigen were selected for determination of ferritin concentration and alanine aminotransferase activity. A correlation between serum ferritin concentration (Y; microgram/l) and alanine aminotransferase activity (X; IU/l) was found in donors with antibody to hepatitis C (log Y = 0.65 x log X + 0.98, r = 0.53, and P < 0.01). The correlation was lower in donors with hepatitis B surface antigen (r = 0.37; P < 0.01). Hepatitis C virus infection probably induces time-dependent iron accumulation associated with the progression of disease activity, while hepatitis B virus infection results in a variety of iron loads with different clinical features. The high disease activity related to hyperferritinemia suggests the presence of iron-induced liver damage in donors with hepatitis C. 相似文献
994.
Ipratropium bromide is a synthetic derivative of atropine with little absorption when used in inhalation, and therefore little secondary effects. The authors review its pharmacological properties and therapeutic efficacy in the treatment of asthma in children. Combined nebulized inhalation of ipratropium bromide and beta 2 sympathomimetic results in a more efficient and more sustained bronchodilatation than beta 2 sympathicomimetic alone in the treatment of acute asthma in children. Ipratropium bromide should be usefully introduced in the therapeutic scheme of acute asthma in children. Further studies will be necessary in order to determine its efficacy and tolerance in infants. 相似文献
995.
S Harino M Motokura N Nishikawa M Fukuda A Sasaoka JE Grunwald 《Canadian Metallurgical Quarterly》1994,117(3):302-307
We studied the ocular findings of two adult patients with the Eisenmenger's syndrome who had atrial septal defects that were diagnosed before the age of 10 years but not operated on and pulmonary hypertension. Both eyes of these patients showed microaneurysms, multiple small blot hemorrhages, or capillary dilation in the temporal peripheral fundus. Multiple microaneurysms and retinal collaterals were confirmed by fluorescein angiography. One of the patients developed bilateral rubeosis iridis with slow progression. These retinal lesions and the rubeosis iridis are probably related to chronic ocular ischemia caused by chronic systemic hypoxia. 相似文献
996.
N. M. Sanghavi Hema Venkatesh Varsha Tandel 《Drug development and industrial pharmacy》1994,20(7):1275-1283
Gilbenclamide, a widely used potent hypoglycaemic agent was solubllized using β -Cyclodextrin and β -Cyclodextrin derivatives. Complexes were prepared by kneading method in a molar ratio of 1:1 of the drug and the cyclodextrlns respectively. The Glibenclamide β -Cyelocextrin complex was characterized and evaluated by I.R. studies, Differential Scanning Calorimotry 6 X-ray diffractometry. The in-vitro dissolution rates of drug from inclusion complexes of β Cyclodextrins and its derivatives were compared. A significant Improvement In dissolution lor, rates of Gllbenclamide was observed with Inclusion complexes of all the Cyclodextrins. However, the solubilizing effect was more in case of β-Cyclodextrin derivatives. 相似文献
997.
998.
The author focusses on advances in equipment that offset physically functional limitations. He discusses how disabled and elderly people are using aids that enhance mobility (walking a certain distance, lifting a weight, or climbing stairs) as well as sensory faculties (seeing print, hearing conversation, and speaking intelligibly) 相似文献
999.
Fractal error for detecting man-made features in aerial images 总被引:3,自引:0,他引:3
A technique is proposed for aiding photointerpreters in detecting man-made features in aerial reconnaissance images. The technique, which uses a metric called fractal error, is based on the observed propensity of natural image features to fit a fractional Brownian motion model. Man-made features usually do not fit this model well, and consequently the fractal error metric may be used as a discriminant function for detecting man-made scene features 相似文献
1000.
Kawai S. Iwatsuki K. Suzuki K. Nishi S. Saruwatari M. Sato K. Wakita K. 《Electronics letters》1994,30(3):251-252
The authors demonstrate 10 Gbit/s optical soliton transmission in a recirculating loop through the use of a monolithically integrated MQW-DFB-LD/MQW-EA modulator light source. The timing jitter due to the Gordon-Haus effect is successfully reduced by the optical bandpass filters conventionally used in the cascaded EDFAs to avoid the accumulation of amplified spontaneous emission. The transmission distance of 7200 km is achieved at a bit error rate of 10-9 相似文献