全文获取类型
收费全文 | 1326篇 |
免费 | 5篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 131篇 |
金属工艺 | 3篇 |
机械仪表 | 70篇 |
建筑科学 | 66篇 |
矿业工程 | 2篇 |
能源动力 | 3篇 |
轻工业 | 421篇 |
水利工程 | 8篇 |
石油天然气 | 16篇 |
武器工业 | 5篇 |
无线电 | 55篇 |
一般工业技术 | 485篇 |
冶金工业 | 9篇 |
原子能技术 | 4篇 |
自动化技术 | 47篇 |
出版年
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 118篇 |
2011年 | 135篇 |
2010年 | 22篇 |
2009年 | 4篇 |
2008年 | 107篇 |
2007年 | 120篇 |
2006年 | 93篇 |
2005年 | 116篇 |
2004年 | 91篇 |
2003年 | 69篇 |
2002年 | 82篇 |
2001年 | 58篇 |
2000年 | 64篇 |
1999年 | 26篇 |
1998年 | 10篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 22篇 |
1994年 | 16篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 13篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1970年 | 1篇 |
1967年 | 3篇 |
1965年 | 1篇 |
1948年 | 2篇 |
排序方式: 共有1334条查询结果,搜索用时 15 毫秒
1.
Interactions of metals and protons with algae 总被引:2,自引:0,他引:2
Crist RH Oberholser K Schwartz D Marzoff J Ryder D Crist DR 《Environmental science & technology》1988,22(7):755-760
2.
Bacon DR 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1988,35(2):152-161
A primary calibration method for ultrasonic hydrophones which uses a Michelson interferometer to determine the particle displacement in an ultrasonic field is discussed. The acoustic pressure is derived from this measurement and used to determine the free-field sensitivity of a hydrophone in the frequency range 0.5-15 MHz. The random uncertainty of the method is typically 1%, whereas the systematic uncertainty varies from 2.3 to 6.6% over the frequency range. To obtain this accuracy, the performance of the system has been carefully examined and appropriate correction factors derived. The greatest difficulty in the method lies in determining the frequency response of the optical detection system, and two different approaches have been used to measure this response. Several acoustical effects have also been studied and the calibration procedure modified to take account of them. The calibration results are in agreement with those of other methods and with the theoretically predicted frequency response of a hydrophone. The method has been used to determine the temporal stability of a hydrophone over a period of two years. 相似文献
3.
4.
5.
6.
Effects of early-postmortem glycolytic rate on beef tenderness 总被引:1,自引:0,他引:1
Electrical stimulation (ES) was applied at 500 V to one side from each of 60 beef carcasses at 30 to 40 min postmortem. Wide ranges of early-postmortem glycolytic and cooling rates were produced in the musculature by use of three different forms of ES (in addition to non-ES treatment of the contralateral sides) and application of chilling routines of four different degrees of severity. Panel and Warner-Bratzler shear evaluations of loin steaks from all 120 sides showed that tenderness was highest when glycolysis had proceeded at an intermediate rate (corresponding to the attainment of a 3-h pH of about 6·1) and was appreciably lower on both sides of this mid-value. The toughening effect of rapid glycolysis (relative to that of a moderately increased glycolytic rate) persisted through 14 days of aging at 2°C.
These observations appear to be incompatible with the view that lysosomal enzymes contribute significantly to ES-induced tenderization. They also indicate that the effect of ES on tenderness is highly dependent on the subsequent cooling rate, very slow chilling sometimes accelerating the already high rate of pH fall to such an extent that the tissue is significantly toughened. Finally, they suggest that the goal of maximizing the early-postmortem rate of pH decline in bovine muscle is misguided and, if attained, will cause sub-optimal tenderness. 相似文献
7.
The white pine cone beetle, Conophthorus coniperda, exhibited dose and enantiospecific responses to -pinene in stands of mature eastern white pine, Pinus strobus, in a seed orchard near Murphy, North Carolina, USA. (–)--Pinene significantly increased catches of cone beetles to traps baited with (± )-trans-pityol. (+)--Pinene did not increase catches of beetles to pityol-baited traps and interrupted the response of beetles to traps baited with (±)-trans-pityol and (–)--pinene. Maximal attraction of cone beetles to pityol-baited traps was obtained with lures releasing (–)--pinene at a rate of 103 mg/day at 23°C. Lures releasing (–)--pinene at rates lower or higher than 103 mg/day resulted in reduced catches to traps baited with (±)-trans-pityol. The sex ratio in all catches was heavily male biased. Attraction of the clerid predator, Thanasimus dubius, to traps baited with (±)-trans-pityol increased significantly with the presence of -pinene, irrespective of enantiomeric composition. Maximal attraction of T. dubius to pityol-baited traps occurred with devices releasing (–)--pinene at the highest rate tested, 579 mg/d at 23°C, a sub optimal rate for cone beetles. 相似文献
8.
Downham MC Hall DR Chamberlain DJ Cork A Farman DI Tamò M Dahounto D Datinon B Adetonah S 《Journal of chemical ecology》2003,29(4):989-1011
The legume podborer, Maruca vitrata (syn. M. testulalis) (F.) (Lepidoptera: Pyralidae) is a pantropical pest of legume crops. Sex pheromone was collected by gland extraction or trapping of volatiles from virgin female moths originating in India, West Africa, or Taiwan. Analysis by GC-EAG and GC-MS confirmed previously published findings that (E,E)-10,12- hexadecadienal is the most abundant EAG-active component with 2–5% of (E,E)-10,12-hexadecadienol also present. At least one other EAG response was detected at retention times typical of monounsaturated hexadecenals or tetradecenyl acetates, but neither could be detected by GC-MS. Laboratory wind-tunnel bioassays and a field bioassay of blends of (E,E)-10,12-hexadecadienal with (E,E)-10,12-hexadecadienol and a range of monounsaturated hexadecenal and tetradecenyl acetate isomers indicated greatest attraction of males was to those including (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal as minor components. In subsequent trapping experiments in cowpea fields in Benin, traps baited with a three-component blend of (E,E)-10,12-hexadecadienal and these two minor components in a 100:5:5 ratio caught significantly more males than traps baited with the major component alone, either two-component blend, or virgin female moths. Further blend optimization experiments did not produce a more attractive blend. No significant differences in catches were found between traps baited with polyethylene vials or rubber septa, or between lures containing 0.01 and 0.1 mg of synthetic pheromone. Significant numbers of female M. vitrata moths, up to 50% of total catches, were trapped with synthetic blends but not with virgin females. At present there is no clear explanation for this almost unprecedented finding, but the phenomenon may improve the predictive power of traps for population monitoring. 相似文献
9.
Sinharoy S Buhay H Burke MG Lampe DR Pollak TM 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1991,38(6):663-671
The growth of ferroelectric BaMgF(4) thin films on Si(100), sapphire, and other substrates under ultrahigh vacuum (UHV) conditions is reported. Microstructural characterization of the films using transmission electron microscopy (TEM) revealed that they were oriented crystalline films, although not epitaxial. Ferroelectric hysteresis measurements yielded spontaneous polarization and coercivity values of almost 1.0 muC/cm(2) and 160 kV/cm, respectively. The discrepancy with the bulk ferroelectric values were attributed to the electrical contacts, impurities in the film, and lack of polar axis orientation. Preliminary capacitance-voltage (C-V) hysteresis measurements on a 480-nm-thick BaMgF(4) film yielded a 10.8-V threshold shift (memory window) in response to a +/-10-V programming voltage for a MIS gate structure similar to that of the ferroelectric memory field-effect transistor (FEMFET). 相似文献
10.
Jackson I Schijns H Schmitt DR Mu J Delmenico A 《The Review of scientific instruments》2011,82(6):064501
Novel laboratory equipment has been modified to allow both torsional and flexural oscillation measurements at sub-microstrain amplitudes, thereby providing seismic-frequency constraints on both the shear and compressional wave properties of cylindrical rock specimens within the linear regime. The new flexural mode capability has been tested on experimental assemblies containing fused silica control specimens. Close consistency between the experimental data and the results of numerical modelling with both finite-difference and finite-element methods demonstrates the viability of the new technique. The capability to perform such measurements under conditions of independently controlled confining and pore-fluid pressure, with emerging strategies for distinguishing between local (squirt) and global (specimen-wide) fluid flow, will have particular application to the study of frequency-dependent seismic properties expected of cracked and fluid-saturated rocks of the Earth's upper crust. 相似文献