全文获取类型
收费全文 | 1562篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 22篇 |
金属工艺 | 3篇 |
机械仪表 | 5篇 |
建筑科学 | 8篇 |
能源动力 | 4篇 |
轻工业 | 7篇 |
无线电 | 5篇 |
一般工业技术 | 31篇 |
冶金工业 | 1468篇 |
自动化技术 | 11篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 8篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 37篇 |
1998年 | 384篇 |
1997年 | 254篇 |
1996年 | 161篇 |
1995年 | 90篇 |
1994年 | 80篇 |
1993年 | 81篇 |
1992年 | 14篇 |
1991年 | 40篇 |
1990年 | 32篇 |
1989年 | 31篇 |
1988年 | 41篇 |
1987年 | 38篇 |
1986年 | 22篇 |
1985年 | 19篇 |
1984年 | 1篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 15篇 |
1978年 | 6篇 |
1977年 | 44篇 |
1976年 | 92篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1969年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1568条查询结果,搜索用时 15 毫秒
51.
A van Teunenbroek SM de Muinck Keizer-Schrama T Stijnen M Jansen BJ Otten HA Delemarre-van de Waal T Vulsma JM Wit CW Rouwé HM Reeser JJ Gosen C Rongen-Westerlaken SL Drop 《Canadian Metallurgical Quarterly》1996,81(11):4013-4021
To optimize the growth promoting effect of growth hormone (GH), 65 previously untreated girls with Turner syndrome (TS), chronological age (CA) 2-11 yr, were randomized into 3 dosage regimen groups: A, B, and C, with a daily recombinant-human GH dose during 4 study years of 4-4-4-4, 4-6-6-6, and 4-6-8-8 IU/m2 b.s. The first GH dosage increase in groups B and C resulted in a significantly higher mean height velocity (HV) compared with constant dose group A. During the third year, when the dose was raised again only in group C, mean HV was significantly higher in groups B and C than in group A, and in group C compared with group B. In year 4 only group C mean HV remained significantly higher than group A. The pattern of change in HSDSCA (Dutch-Swedish-Danish Turner references) was identical; however, in year 4 mean delta HSDSCA in group B also remained significantly higher than group A. After 4 yr GH treatment, the following was determined. 1) The mean delta HSDSCA was significantly higher for groups B and C compared with group A, but not significantly different between groups B and C. 2) Although significantly higher compared with estimated values for untreated Dutch girls with TS, bone maturation of the GH treated girls was not significantly different between groups. 3) It was positively related with the degree of bone age (BA) retardation at start of study and negatively with baseline CA. 4) Both the modified Index of Potential Height (mIPHRUS) and a recently developed Turner-specific final height (FH) prediction method (PTSRUS), based on regression coefficients for H, CA, and bone age, showed significant increases in mean FH prediction, without significant differences between groups. PTSRUS values were markedly higher than the mIPHRUS values. Dose dependency could be shown for the area under the curve (AUC) for GH, but delta HSDSCA was not linearly related with AUC. Baseline GH binding protein (BP) levels were in 84% of the cases within the normal age range; the decrease in mean levels after 6 months GH was not significant. Mean insulin-like growth factor I (IGF-I) and IGFBP-3 plasma levels increased significantly, without significant differences between groups. delta HSDSCA during GH was dependent on IGF-I plasma levels at baseline and during the study period, beta-0.002 and beta-0.0004. Thus, a stepwise GH-dosing approach reduced the "waning" effect of the growth response after 4 yr treatment without undue bone maturation. FH prediction was not significantly different between treatment groups. Irrespective of the GH dose used, initiation of GH treatment at a younger age was beneficial after 4 yr GH when expressed as actual cm gained or as gain in FH prediction, but was not statistically significant when expressed as delta HSDSCA over the study period. 相似文献
52.
As the sensitivity of the new in vitro cancer detection techniques increases, a larger number of "false positive" results can be expected from control populations apparently free from malignant disease at the time of the test. An attempt is made to predict the number of unexplained positives, together with the expected age and sex distribution, using published cancer registration statistics. The predicted numbers are compared with the observed numbers of unexplained positives in two clinical trials of the MEM test. 相似文献
53.
G. Welsch Y-T. Lee P. C. Eloff D. Eylon F. H. Froes 《Metallurgical and Materials Transactions A》1983,14(3):761-769
A blended elemental Ti-6A1-4V alloy powder, sintered to 99 pct theoretical density, was tested in tension and fatigue and characterized by optical, scanning, and transmission electron microscopy and by X-ray energy dispersive analysis. The microstructure consisted of a combination of equiaxed and low aspect ratio lamellar alpha phase. Two types of pores were observed: macropores at grain boundaries or triple points, and micropores within alpha regions. Chemical homogeneity was achieved within individual alpha or beta regions with slight compositional fluctuations between different grains. The deformation modes in alpha regions were investigated by transmission electron microscopy on thin foils prepared from tensile and cyclically deformed specimens. Tensile deformation occurred by homogeneous slip on both prismatic and pyramidal alpha slip planes. In cyclic deformation, on the other hand, little slip activity was found except for some heterogeneous slip on the basal plane associated with a relatively large micropore. Micropores of ?0.5 μm size were found to act as dislocation pinning sites. 相似文献
54.
Effect of tinidazole, metronidazole and nitrofurazone on nucleic acid synthesis in Clostridium bifermentans 总被引:1,自引:0,他引:1
Coplanar lines of different orientations rotating in depth and viewed in parallel projection may appear to rotate in different directions and reverse independently of each other, or they may appear coplanar and all reverse together. The frequency of the latter "grouped" appearance for lines with an orientation range of 30 degrees was a function of the number of lines in a given space. Grouping was greater for lines converging to an implicit vanishing point and for lines with collinear edges regardless of their orientations. Line length, and by inference, interline separation also had effect of the nature of the response. 相似文献
55.
The quadrupole resonator, designed to measure the surface resistance of superconducting samples at 400 MHz has been refurbished. The accuracy of its RF-dc compensation measurement technique is tested by an independent method. It is shown that the device enables also measurements at 800 and 1200 MHz and is capable to probe the critical RF magnetic field. The electric and magnetic field configuration of the quadrupole resonator are dependent on the excited mode. It is shown how this can be used to distinguish between electric and magnetic losses. 相似文献
56.
Hans-Joachim Nees Harald Keller Thomas Facklam Albert Herrmann Jochen Welsch Uwe Bergstrßer Heinrich Heydt Manfred Regitz 《Advanced Synthesis \u0026amp; Catalysis》1993,335(7):589-598
Diazo Compounds. 72. Diazoalkylphosphanes – Synthesis by Electrophilic Diazoalkane Substitution and Oxidative Addition Reactions at Phosphorus Electrophilic diazoalkane substitution of the diazomethyl compounds 1a,b with the chloro phosphanes 2a-o in the presence of lithium diethylamide yields the diazoalkyl phosphanes 3a-z . Oxidative addition of oxygen, sulfur and selenium at phosphorus leads into the series of oxo, thioxo and selenoxo phosphanes having diazoalkyl substituents ( 4a-d, 5a-m and 7a-d ). The silyl group of 5n,o is cleaved by chromatography on aluminium oxide to yield the (diazomethyl)phosphane sulfides 6a,b . 相似文献
57.
58.
J Foden-Shroff CW Redman H Tucker J Millinship E Thomas A Warwick PW Jones 《Canadian Metallurgical Quarterly》1998,105(9):1022-1025
AIMS: To determine functional results after unilateral and bilateral cataract surgery in children with different aphakic optical correction. METHODS: In this retrospective study, we evaluated visual acuity and binocular vision in 107 children who underwent cataract surgery during the 10 year period from 1985 to 1995. Aphakia was corrected by an intracapsular intraocular lens (IOL), spectacles or contact lenses. RESULTS: Mean visual acuity was > 20/40 (< 0.3 log MAR) with normal binocular vision in 58 children over 7 months of age operated on for bilateral cataracts. Pseudophakic eyes regained visual acuity > 20/63 (< 0.5 log MAR) more often (90%) than aphakic eyes (46%) (p < 0.001). Binocular vision was also achieved more often after IOL implantation (p < 0.001). Visual outcome of early bilateral cataracts was less satisfactory in children with abnormal foveolar function. For 49 children who had surgery for unilateral cataracts, prognosis was poor when surgery was performed before the age of 7 months. For cataract surgery in older children (> or = 7 months) mean visual acuities were better with IOL implantation (p < 0.05). CONCLUSION: Cataract surgery with unilateral and bilateral IOL implantation can provide a beneficial effect on final visual outcome in children who are operated on before abnormal foveolar function develops. 相似文献
59.
FI Meredith RT Riley CW Bacon DE Williams DB Carlson 《Canadian Metallurgical Quarterly》1998,61(8):1034-1038
The purpose of this study was (i) to determine whether pure fumonisin B1 could be incorporated into, recovered, and detected by high-pressure liquid chromatographic analysis from the semipurified Oregon test diet (OTD) used in rainbow trout feeding studies, and (ii) to determine if the incorporated fumonisin B1 was biologically available using the change in free sphingoid bases in liver, kidney, and serum as a mechanism-based biomarker. The results indicate that fumonisin is not easily quantified in the OTD. Recoveries ranged from 12 to 81% of the calculated concentrations based on the fumonisin B1 added to the OTD. However, the fumonisin B1 in the OTD was readily absorbed and biologically active as evidenced by marked increases in free sphinganine in liver, kidney, and serum. The magnitude of the increase in free sphinganine at 100 ppm in the OTD was comparable to that known to be associated with liver toxicity in rats, pigs, and ponies. 相似文献
60.