全文获取类型
收费全文 | 6863篇 |
免费 | 433篇 |
国内免费 | 54篇 |
专业分类
电工技术 | 100篇 |
综合类 | 22篇 |
化学工业 | 1988篇 |
金属工艺 | 167篇 |
机械仪表 | 254篇 |
建筑科学 | 180篇 |
矿业工程 | 4篇 |
能源动力 | 412篇 |
轻工业 | 638篇 |
水利工程 | 97篇 |
石油天然气 | 56篇 |
无线电 | 717篇 |
一般工业技术 | 1280篇 |
冶金工业 | 326篇 |
原子能技术 | 87篇 |
自动化技术 | 1022篇 |
出版年
2024年 | 26篇 |
2023年 | 130篇 |
2022年 | 354篇 |
2021年 | 453篇 |
2020年 | 350篇 |
2019年 | 389篇 |
2018年 | 451篇 |
2017年 | 352篇 |
2016年 | 379篇 |
2015年 | 231篇 |
2014年 | 379篇 |
2013年 | 616篇 |
2012年 | 382篇 |
2011年 | 392篇 |
2010年 | 331篇 |
2009年 | 286篇 |
2008年 | 206篇 |
2007年 | 165篇 |
2006年 | 159篇 |
2005年 | 112篇 |
2004年 | 99篇 |
2003年 | 91篇 |
2002年 | 84篇 |
2001年 | 54篇 |
2000年 | 50篇 |
1999年 | 49篇 |
1998年 | 88篇 |
1997年 | 72篇 |
1996年 | 60篇 |
1995年 | 61篇 |
1994年 | 27篇 |
1993年 | 36篇 |
1992年 | 35篇 |
1991年 | 28篇 |
1990年 | 26篇 |
1989年 | 27篇 |
1988年 | 18篇 |
1987年 | 33篇 |
1986年 | 33篇 |
1985年 | 23篇 |
1984年 | 33篇 |
1983年 | 29篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 16篇 |
1975年 | 12篇 |
排序方式: 共有7350条查询结果,搜索用时 15 毫秒
21.
RM Campbell EP Heimer M Ahmad HG Eisenbeis TJ Lambros Y Lee RW Miller PR Stricker AM Felix 《Canadian Metallurgical Quarterly》1997,49(6):527-537
In the present study, human growth hormone-releasing factor (hGRF) and analogs were successfully pegylated at the carboxy-terminus using a novel solid- and solution-phase strategy. Following synthesis, these pegylated hGRF analogs were evaluated for in vitro and in vivo biological activity. Specifically, hGRF (1-29)-NH2, [Ala15]-hGRF (1-29)-NH2, [desNH2Tyr1, D-Ala2, Ala15]-hGRF(1-29)-NH2 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-OH were each C-terminally extended using a Gly-Gly-Cys-NH2 spacer (previously demonstrated not to alter intrinsic biological activity), and then monopegylated via coupling to an activated dithiopyridyl-PEG reagent. PEG moieties of 750, 2000, 5000 or 10,000 molecular weight (MW) were examined to determine the effect of polymer weight on activity. Initial biological evaluations in vitro revealed that all C-terminally pegylated hGRF analogs retained high growth hormone (GH)-releasing potencies, regardless of the MW of PEG polymer employed. Two of these pegylated hGRF analogs, [desNH2Tyr1, D-Ala2, Ala15]-hGRF (1-29)-Gly-Gly-Cys(NH2)-S-Nle-PEG5000 and [His1, Val2, Gln8, Ala15, Leu27]-hGRF(1-32)-Gly-Cys(NH2)-S-Nle-PEG5000, were subsequently evaluated in both pig and mouse models and found to be highly potent (in vivo potency range = 12-55-fold that of native hGRF). Relative to their non-pegylated counterparts, these two pegylated hGRF analogs exhibited enhanced duration of activity. 相似文献
22.
S. Ahmad B.E. Bonner W. Gere G.S. Mutchler P. Rambo S. Toshkov E. Platner H.J. Crawford J.M. Engelage 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1993,330(3):416-421
The performance of Bicron BC404, BC408 and BC420 scintillators coupled to a Hamamatsu R3432 proximity mesh dynode photomultiplier tube was studied using pion beams from the TRIUMF cyclotron and the Brookhaven National Laboratory AGS accelerator. A system resolution of better than 100 ps seems feasible. This will satisfy the requirement for charged particle identification in the STAR detector at RHIC. 相似文献
23.
This paper examines Total Quality Management (TQM) as defined by Dr. W. Edwards Deming including Deming's fourteen points and explains how the United States' Department of Defense (DOD) defines TQM and why TQM is necessary. It also covers how the DOD is planning on implementing TQM and the policy that has been established as guidance in the implementation process. 相似文献
24.
Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable
sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L−1 sodium tungstate, potassium iodate and 1 mol L−1 orthophosphoric acid to aqueous solution of 0·1 mol L−1 zirconium(IV) oxychloride. Its ion exchange capacity for Na+ and K+ was found to be 2·20 and 2·35 meq g−1 dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier
transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger
at different temperatures has been studied. The analytical importance of the material has been established by quantitative
separation of Pb2+ from other metal ions. 相似文献
25.
Dielectric and thermal characteristics of gel grown single crystals of ytterbium tartrate trihydrate
Dielectric and thermal characteristics of gel grown single crystals of ytterbium tartrate trihydrate have been carried out.
The dielectric constant has been measured as a function of frequency in the range 2 kHz–1 MHz and temperature range 30–300 °C.
The dielectric constant increases with temperature, attains a peak near 215 °C, and then decreases as the temperature exceeds
215 °C. The dielectric anomaly at 215 °C is suggested to be due to phase transition brought about in the material. The dielectric
behaviour of the material is correlated with the results on thermal analysis. Thermogravimetric and differential thermal analysis
have been used to study the thermal characteristics of the material. The experimental results show that the material is thermally
stable up to 200 °C. The decomposition process occurs in two stages until ytterbium oxide is formed at 700 °C. The non-isothermal
kinetic parameters e.g., activation energy and the frequency factor have been evaluated for each stage of thermal decomposition
by using the integral method, applying the Coats–Redfern approximation. 相似文献
26.
5(4H)-Oxazolones react with ammonium acetate under microwave irradiation and using graphite as support in an eco-friendly process.
The reaction was carried out under solvent-free conditions and the imidazolones were obtained quantitatively. Moreover the
reaction time was reduced too. 相似文献
27.
The study suggests improvements in the design of new houses to conserve energy and enhance indoor thermal comfort. Summer temperature records show that a new house has an average indoor temperature of 35°C with the ambient average 31°C. The traditional house in the old city recorded 28°C for the same period. Winter temperatures in both types of houses were similar (12°C) when not occupied. Architectural features of the two houses were compared to identify those responsible for difference in the thermal performance. Larger exposed surface and window areas, higher overall heat transfer coefficient and weaker thermal coupling with the ground for the new houses seems to contribute to their inferior thermal performance. 相似文献
28.
29.
30.
The optical method of caustics has been utilised to measure both the stress intensity factor for a crack lying along the interface of an aluminium/epoxy bimaterial specimen, and the mode mixity arising from the difference in the elastic properties across the interface. Measurements were carried out by using a novel modification to the method whereby caustics are produced and measured from both sides of the specimen, so compensating automatically for the distortion induced in the specimen due to misaligned loading fixtures. A flat reflective surface across the interface was obtained by adhering a reflective coating to the specimen. Verification that this coating does not affect measurement accuracy was obtained by comparing stress intensity factors measured from coated and uncoated monolithic aluminium specimens where good agreement was found to exist between both measurements. 相似文献