全文获取类型
收费全文 | 2375篇 |
免费 | 96篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 52篇 |
综合类 | 43篇 |
化学工业 | 272篇 |
金属工艺 | 43篇 |
机械仪表 | 79篇 |
建筑科学 | 146篇 |
矿业工程 | 8篇 |
能源动力 | 34篇 |
轻工业 | 256篇 |
水利工程 | 23篇 |
石油天然气 | 21篇 |
武器工业 | 2篇 |
无线电 | 109篇 |
一般工业技术 | 138篇 |
冶金工业 | 1147篇 |
原子能技术 | 14篇 |
自动化技术 | 116篇 |
出版年
2021年 | 25篇 |
2019年 | 7篇 |
2018年 | 20篇 |
2017年 | 30篇 |
2016年 | 16篇 |
2015年 | 32篇 |
2014年 | 83篇 |
2013年 | 104篇 |
2012年 | 51篇 |
2011年 | 138篇 |
2010年 | 62篇 |
2009年 | 76篇 |
2008年 | 77篇 |
2007年 | 79篇 |
2006年 | 53篇 |
2005年 | 49篇 |
2004年 | 44篇 |
2003年 | 47篇 |
2002年 | 33篇 |
2001年 | 29篇 |
2000年 | 28篇 |
1999年 | 42篇 |
1998年 | 307篇 |
1997年 | 183篇 |
1996年 | 141篇 |
1995年 | 105篇 |
1994年 | 63篇 |
1993年 | 85篇 |
1992年 | 28篇 |
1991年 | 15篇 |
1990年 | 27篇 |
1989年 | 30篇 |
1988年 | 23篇 |
1987年 | 22篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 27篇 |
1981年 | 11篇 |
1980年 | 17篇 |
1979年 | 11篇 |
1978年 | 18篇 |
1977年 | 46篇 |
1976年 | 73篇 |
1975年 | 16篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1971年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有2503条查询结果,搜索用时 15 毫秒
1.
2.
The Telecommunications Information Networking Architecture (TINA) Consortium is an international collaboration aiming at defining and validating an open architecture for telecommunication services for the broadband, multimedia, and information era. The architecture is based on distributed computing, object orientation, and other concepts and standards from the telecommunications and computing industries. This paper provides an introduction to TINA. First, it presents an overall view of TINA, followed by a brief introduction to the main parts of the architecture, namely the computing, network, service, and management architectures. This is followed by a brief overview of interworking and migration scenarios for legacy systems. Finally, an overview of a tool-set to aid service specification and design is presented 相似文献
3.
H Reznik-Wolf TA Treves M Davidson J Aharon-Peretz PH St George Hyslop J Chapman AD Korczyn B Goldman E Friedman 《Canadian Metallurgical Quarterly》1996,98(6):700-702
Germline mutations in the presenilin 1 (PS1) gene apparently account for the majority of early-onset, familial Alzheimer's disease (AD). Using a mutation-screening strategy (denaturing gradient gel electrophoresis; DGGE), we analyzed a large family with early onset AD and seizures. The patients in this family showed a novel missense mutation in exon 5 of the PS1 gene (A to T change in codon 120, altering glutamine to aspartic acid). This novel mutation is located within the second hydrophilic domain of the molecule, a region not particularly involved in previously described germline mutations, and is of unknown biological significance. These results also demonstrate that DGGE can be used effectively to screen for mutations within this gene. 相似文献
4.
5.
The response people have to vaccination varies because their immune systems differ and vaccine failures occur. Here we consider the effect that a random response, independent for each vaccinee, has on the vaccination coverage required to prevent epidemics in a large community. For a community of uniformly mixing individuals an explicit expression is found for the critical vaccination coverage (CVC) and the effect of the vaccine response is determined entirely by the mean E(AB), where A and B, respectively, reflect the infectivity and susceptibility of a vaccinated individual. This result shows that the usual concept of vaccine efficacy, which focuses on the amount of protection the vaccine provides the vaccinee against infection, is not adequate to describe the requirements for preventing epidemics when vaccination affect infectivity. The estimation of E(AB) poses a problem because A and B refer to the vaccine response of the same individual. Similar results are found when there are different types of individual, but now the mean E(AB) may differ between types. However, for a community made up of households it is shown that the CVC also depends on other characteristics of the vaccine response distribution. In practice this means that estimating a single measure of vaccine effectiveness is generally not enough to determine the CVC. For a specific community of households it is found that the vaccination coverage required to prevent epidemics decreases as the variation in the vaccine response increases. 相似文献
6.
The monoenoic methyl esters from numerous fats and oils which contained appreciablecis-9-hexadecenoic acid (cis-9-16∶1) were isolated by liquid-solid chromatography on silver nitrate-silica gel. Analysis of the monoenes by packed and
capillary column gas-liquid chromatography showed that significant amounts ofcis-11-octadecenoic acid (cis-11-18∶1) were present in all samples. The amount ofcis-11-18∶1 found in the monoenoic methyl esters increased proportionally to logarithmic increases in thecis-9-16∶1 level. Most analyses reported in the literature also show this proportionality. This mathematical relationship suggests
that chain elongation ofcis-9-16∶1 tocis-11-18∶1 is a biosynthetic pathway operative in a wide variety of species. 相似文献
7.
The influence of silicate and phosphate anions on the performance of Pt/Sn electrodeposited catalysts for the electro-oxidation of methanol has been studied. Both anions were found to have serious poisoning effects on the catalyst, whereas platinum catalysts were unaffected. The poisoning mechanism in both cases was thought to be initiated by the formation of either stannosilicates or stannophosphates species followed by the build-up of polymeric silicate or phosphate that ultimately blocks the active sites. The origin of the poisoning mechanism in both cases was found to be chemical rather than electrochemical. In the case of silicate, the poisoning species could be removed and the catalytic activity restored by chemical treatment with sulphuric acid. 相似文献
8.
9.
R. T. Santoro R. G. Alsmiller Jr. J. M. Barnes G. T. Chapman 《Journal of Fusion Energy》1982,2(3):237-249
Measured and calculated neutron and gamma-ray energy spectra resulting from the transport of 14 MeV neutrons through a 0.30-m-thick lithium hydride slab and through a 0.05-m-thick lead slab followed by 0.30 m of lithium hydride are compared. Also reported are comparisons of the measured and calculated neutron energy spectra behind an 0.80-m-thick assembly comprised of stainless steel type 304 and borated polyethylene. The spatial dependence of the gamma-ray energy deposition rate measured using thermoluminescent detectors is compared with calculated data. The calculated data obtained using two-dimensional radiation transport methods and ENDF/B-IV cross-section data are in good agreement for all of the experimental configurations. Calculated integral neutron energy spectra agree with the measured data within 5 to 20% depending on neutron energy for the LiH and Pb plus LiH assemblies. The gamma-ray spectra agree within 20% for these slabs. The measured and calculated neutron energy spectra behind the SS-304-borated polyethylene assembly agree within 5% except at neutron energies below 5 MeV where background radiation influences the measured spectra. The gamma-ray energy deposition rates as a function of depth agree within a factor of two at all detector locations. 相似文献
10.
Temperature measurement by IR (infrared) camera was performed oll HT-T tokamak. particularly during long pulse discharges, during which the temperature of the hot spots on the belt limiter exceeded 1000℃. The heat load on the surface of the movable limiter could be obtained through ANSYS with the temperature measured by IR-camera. This work could be important for the temperature measurement and heat load study on the first wall of EAST device. 相似文献