全文获取类型
收费全文 | 2992篇 |
免费 | 87篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 55篇 |
综合类 | 37篇 |
化学工业 | 261篇 |
金属工艺 | 112篇 |
机械仪表 | 43篇 |
建筑科学 | 72篇 |
矿业工程 | 9篇 |
能源动力 | 48篇 |
轻工业 | 164篇 |
水利工程 | 27篇 |
石油天然气 | 12篇 |
武器工业 | 7篇 |
无线电 | 106篇 |
一般工业技术 | 213篇 |
冶金工业 | 1780篇 |
原子能技术 | 34篇 |
自动化技术 | 132篇 |
出版年
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 25篇 |
2018年 | 30篇 |
2017年 | 26篇 |
2016年 | 36篇 |
2015年 | 17篇 |
2014年 | 32篇 |
2013年 | 66篇 |
2012年 | 64篇 |
2011年 | 111篇 |
2010年 | 83篇 |
2009年 | 77篇 |
2008年 | 97篇 |
2007年 | 79篇 |
2006年 | 58篇 |
2005年 | 65篇 |
2004年 | 52篇 |
2003年 | 28篇 |
2002年 | 34篇 |
2001年 | 32篇 |
2000年 | 36篇 |
1999年 | 59篇 |
1998年 | 534篇 |
1997年 | 309篇 |
1996年 | 197篇 |
1995年 | 134篇 |
1994年 | 108篇 |
1993年 | 99篇 |
1992年 | 24篇 |
1991年 | 23篇 |
1990年 | 31篇 |
1989年 | 37篇 |
1988年 | 38篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 28篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 65篇 |
1976年 | 129篇 |
1971年 | 6篇 |
1967年 | 10篇 |
排序方式: 共有3112条查询结果,搜索用时 46 毫秒
71.
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
72.
ES van Waalwijk van Doorn AH Meier AW Ambergen RA Janknegt 《Canadian Metallurgical Quarterly》1996,23(3):345-371
This article elucidates the clinical applicability and state of the art of ambulatory urodynamics. Ambulatory urodynamics have evolved into practical investigations like EAC, HFM, and EAC combined with renal pelvimetry. EAC has been shown to be the method of preference if detrusor overactivity is involved. Conventional filling cystometry has proved to be an unreliable way to exclude detrusor instability. De novo instability after suspension surgery often indicates that an existing detrusor overactivity was not identified preoperatively. EAC including flowmetry has shown considerable variance in obstructive and contractility parameters in males with LUTS indicative for BPH. This raises doubt whether the clinical flow analysis is the suitable "gold standard" as advocated by the ICS. For a real break through of EAC, less complex automatic analysis is necessary. HFM is a newer method within the range of ambulatory urodynamic tests. It has not yet been completely evaluated. But, because the technique is analogous to the office flowmetry, noninvasive and very well accepted by the patients, it is expected to be widely used. This expectation is strengthened by the fact that HFM seems to show individual therapeutic efficacy of drugs, such as alpha-blockers. As a research tool to evaluate efficacy, it is far more powerful than conventional methods because of the reduction of within-patient standard deviation to about 10%. Finally, EAC combined with pelvimetry offers a promising method for the clinical evaluation of a combined dysfunction of upper and lower urinary tract. 相似文献
73.
Spectral element spatial discretization error in solving highly anisotropic heat conduction equation
This paper describes a study of the effects of the overall spatial resolution, polynomial degree and computational grid directionality on the accuracy of numerical solutions of a highly anisotropic thermal diffusion equation using the spectral element spatial discretization method. The high-order spectral element macroscopic modeling code SEL/HiFi has been used to explore the parameter space. It is shown that for a given number of spatial degrees of freedom, increasing polynomial degree while reducing the number of elements results in exponential reduction of the numerical error. The alignment of the grid with the direction of anisotropy is shown to further improve the accuracy of the solution. These effects are qualitatively explained and numerically quantified in 2- and 3-dimensional calculations with straight and curved anisotropy. 相似文献
74.
Patrick Duessel Christian Gehl Ulrich Flegel Sven Dietrich Michael Meier 《International Journal of Information Security》2017,16(5):475-490
Anomaly detection allows for the identification of unknown and novel attacks in network traffic. However, current approaches for anomaly detection of network packet payloads are limited to the analysis of plain byte sequences. Experiments have shown that application-layer attacks become difficult to detect in the presence of attack obfuscation using payload customization. The ability to incorporate syntactic context into anomaly detection provides valuable information and increases detection accuracy. In this contribution, we address the issue of incorporating protocol context into payload-based anomaly detection. We present a new data representation, called \({c}_n\)-grams, that allows to integrate syntactic and sequential features of payloads in an unified feature space and provides the basis for context-aware detection of network intrusions. We conduct experiments on both text-based and binary application-layer protocols which demonstrate superior accuracy on the detection of various types of attacks over regular anomaly detection methods. Furthermore, we show how \({c}_n\)-grams can be used to interpret detected anomalies and thus, provide explainable decisions in practice. 相似文献
75.
76.
77.
78.
哈达 《数码设计:surface》2008,(3X):5-6
设计的功能是以人为本,丰富和升华人们的生理体验和心理体验以提升生活品质,传递信息和新的思维方式;设计作品的优劣从某种角度来说是设计思维深入程度决定的;设计思维是以个人对世界的认识为基础的;人对世界认识的程度实际上也就是设计思维深入的程度,因此我们应弄清自己思维的渊源,树立正确的世界观。 相似文献
79.
哈达 《数码设计:surface》2008,(3):5-6
设计的功能是以人为本,丰富和升华人们的生理体验和心理体验以提升生活品质,传递信息和新的思维方式;设计作品的优劣从某种角度来说是设计思维深入程度决定的;设计思维是以个人对世界的认识为基础的;人对世界认识的程度实际上也就是设计思维深入的程度,因此我们应弄清自己思维的渊源,树立正确的世界观。 相似文献
80.
J. Meier P. Egelhof C. Fischer A. Himmler G. Kirchner A. v. Kienlin G. Kraus W. Henning K. W. Shepard 《Journal of Low Temperature Physics》1993,93(3-4):231-238
Status and results of a research project are reported, which aims at developing calorimetric low temperature detectors for heavy ions. The special conditions for the detection of energetic heavy ions are discussed. The response of an aluminium transition edge calorimeter, operated at about1.5K, to the impact of heavy ions was investigated. The observed energy resolutions E/E=3.9×10–3for5.9MeV/u
208
Pb-ions, E/E=1.6×10–3for4.8MeV/u
58
Ni-ions and E/E=4.3×10–3for100MeV/u
20
Ne-ions are most probably not yet limited by the intrinsic detector resolution. The present results already represent an improvement over conventional solid state detectors and ionization chambers. 相似文献