全文获取类型
收费全文 | 1994篇 |
免费 | 53篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 50篇 |
综合类 | 38篇 |
化学工业 | 52篇 |
金属工艺 | 42篇 |
机械仪表 | 25篇 |
建筑科学 | 43篇 |
矿业工程 | 8篇 |
能源动力 | 6篇 |
轻工业 | 82篇 |
水利工程 | 25篇 |
石油天然气 | 10篇 |
武器工业 | 7篇 |
无线电 | 31篇 |
一般工业技术 | 60篇 |
冶金工业 | 1508篇 |
原子能技术 | 21篇 |
自动化技术 | 73篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 8篇 |
2020年 | 4篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 23篇 |
2012年 | 25篇 |
2011年 | 61篇 |
2010年 | 51篇 |
2009年 | 44篇 |
2008年 | 49篇 |
2007年 | 50篇 |
2006年 | 37篇 |
2005年 | 49篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 15篇 |
1999年 | 32篇 |
1998年 | 443篇 |
1997年 | 264篇 |
1996年 | 169篇 |
1995年 | 97篇 |
1994年 | 79篇 |
1993年 | 79篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 27篇 |
1988年 | 29篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 13篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1978年 | 3篇 |
1977年 | 58篇 |
1976年 | 115篇 |
1975年 | 2篇 |
1965年 | 2篇 |
1963年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有2081条查询结果,搜索用时 15 毫秒
101.
Lizards (Dipsosaurus dorsalis) were placed in a desertlike environment in which the ambient temperature (Ta) at night (1800-0600 h) was 12 degrees C and the day (0600-1800 h) Ta was between 30 and 55 degrees C depending on the location within the chamber. When dead Aeromonas hydrophila (4 X 10(9) organisms) was injected into nine lizards, an elevation in body temperature (Tb) of 2.7 degrees C was observed during the same day. On the day after bacterial injection the lizards' body temperatures averaged 41.6 degrees C, an increase of 4.2 degrees C over their control day Tb. Further investigations on the febrile response of D. dorsalis were conducted at the University of Wisconsin's Biotron, where there exists a simulated desert environment with the light intensity, temperature, and humidity closely parelleling a typical spring day in the southwestern desert of the United States (the natural habitat of Dipsosaurus). In this environment injection of dead bacteria into seven lizards led to an average febrile response of similar magnitude (Tb = 40.5 degrees C) but with a longer latency than that found at the University of Michigan. Injection of 13 lizards with live A. hydrophila (5 X 10(9) organism subcut.) in the simulated desert at Michigan led to a daytime fever averaging 2.3 degrees C (mean Tb = 40.6 degrees C) over a 5-day period. During the 6th and 7th day the lizards' body temperature returned to the normal or afebrile level. Injections of sodium salicylate along with dead A. hydrophila resulted in a dose-dependent attenuation of the febrile response. These results demonstrate that the reptilian febrile response is strikingly similar to avian and mammalian fever and suggest a common origin and perhaps function for the febrile mechanism. 相似文献
102.
103.
A 6-week-old breast-fed infant had obstructive jaundice and hepatomegaly. When a dry-cleaning solvent, tetrachloroethylene, was detected in the mother's milk and blood, breast-feeding was discontinued. Rapid clinical and biochemical improvement followed. The child grew normally and had normal liver function during 2 years of follow-up. 相似文献
104.
105.
This paper describes a study of the physico-chemical and radioimmunological properties of three antialdosterone antisera which permitted practical conclusions to be drawn. By its high degree of specificity, anti-aldo-3-oxime-BSA constitutes the most useful antiserum for the clinical assay of aldosterone. The principal advantage of this antiserum is that it allows both urinary and blood aldosterone radioimmunoassay without the necessity of including a chromatographic step. No problems arise with the blanks. This work also includes the study of two anti-deoxycorticosterone antisera. The aldosterone and deoxycorticosterone values, obtained from normal subjects under various physiological conditions, are in agreement with the values given in the literature. 相似文献
106.
107.
Gray scale B-scans in renal sinus lipomatosis show a variety of features which must be differentiated from clinically significant pathological processes. Normal kidneys show dense homogeneous central echoes. In renal sinus lipomatosis, however, the central echoes are divided and become more sparse (Type I), interspersed with small relatively echo-free areas (Type II), or outline a single relatively echo-free area resembling a mass (Type III). In contrast to similar features in hydronephrosis or multiple cysts, the relatively echo-free areas in lipomatosis are ill-defined and do present several weak internal echoes. 相似文献
108.
The outdating of units of blood can be reduced by decreasing the amount of time they spend in an assigned or crossmatched status. This reduction can be achieved in a hospital by establishing a maximum surgical blood order schedule (MSBOS) which reduces the excessive number of units of blood crossmatched preoperatively for patients undergoing elective surgery. The various steps which occurred in the development of a MSBOS in a large general hospital are detailed and the projected reduction in the number of crossmatched units which can be achieved with the MSBOS is illustrated. illustrated. The projected number of units of blood transfused to patients during their hospitalization for 50 common primary surgical procedures in the United States during 1974 is presented as a basis for defining maximum blood orders for each procedure. 相似文献
109.
应用一种新的近净成型技术——凝胶注模成型技术,成功制备大尺寸、复杂形状医用多孔钛人造骨替代材料,并研究了凝胶注模成型工艺参数对浆料流动特性、坯体强度及烧结体孔隙、力学性能的影响。研究结果表明:预混液中有机单体的浓度、单体/交联剂比例以及固相含量是决定钛粉浆料表观粘度、Gelcasting坯体强度的重要参数;对于医用多孔钛植入材料的凝胶注模成型工艺,适合的顸混液单体浓度为30%(质量分数),单体,交联剂比例为120:1,浆料固相含量为34%(体积分数);1100℃保温1.5h是凝胶注模成型多孔钛较为适合的烧结工艺路线;所制得孔隙度46.5%、开孔隙度40.7%多孔钛的抗压强度158.6MPa、弹性模量8.5GPa,与自然骨基本匹配,适合作为人造骨替代材料。 相似文献
110.
MH Kolk M van der Graaf CT Fransen SS Wijmenga CW Pleij HA Heus CW Hilbers 《Canadian Metallurgical Quarterly》1998,17(24):7498-7504
The solution structure of an RNA-hairpin present in the pseudoknot, which is found at the 3'-terminus of turnip yellow mosaic virus genomic RNA, has been solved by nuclear magnetic resonance spectroscopy. The loop, which contains the sequence 5'-GGGUCA-3', was found to be highly structured and, contrary to expectations, does not attain its stability through GA or GC base pair formation but by triple interactions between the tilted adenosine and the minor groove sides of the first two guanosines. Interestingly, a very similar conformation was found for the cognate pseudoknot, implying that the 3'-hairpin is preformed for folding into a pseudoknotted structure. These findings suggest a mechanism of 'predetermined-fit' as a principle in RNA folding. 相似文献