全文获取类型
收费全文 | 3581篇 |
免费 | 82篇 |
专业分类
电工技术 | 44篇 |
综合类 | 7篇 |
化学工业 | 831篇 |
金属工艺 | 92篇 |
机械仪表 | 73篇 |
建筑科学 | 173篇 |
矿业工程 | 25篇 |
能源动力 | 106篇 |
轻工业 | 206篇 |
水利工程 | 33篇 |
石油天然气 | 7篇 |
无线电 | 223篇 |
一般工业技术 | 546篇 |
冶金工业 | 889篇 |
原子能技术 | 37篇 |
自动化技术 | 371篇 |
出版年
2022年 | 35篇 |
2021年 | 49篇 |
2019年 | 28篇 |
2018年 | 34篇 |
2017年 | 25篇 |
2016年 | 66篇 |
2015年 | 47篇 |
2014年 | 62篇 |
2013年 | 213篇 |
2012年 | 95篇 |
2011年 | 139篇 |
2010年 | 111篇 |
2009年 | 120篇 |
2008年 | 122篇 |
2007年 | 121篇 |
2006年 | 115篇 |
2005年 | 110篇 |
2004年 | 80篇 |
2003年 | 77篇 |
2002年 | 73篇 |
2001年 | 69篇 |
2000年 | 32篇 |
1999年 | 65篇 |
1998年 | 169篇 |
1997年 | 129篇 |
1996年 | 90篇 |
1995年 | 80篇 |
1994年 | 78篇 |
1993年 | 73篇 |
1992年 | 61篇 |
1991年 | 39篇 |
1990年 | 34篇 |
1989年 | 44篇 |
1988年 | 31篇 |
1987年 | 43篇 |
1986年 | 44篇 |
1985年 | 58篇 |
1984年 | 49篇 |
1983年 | 49篇 |
1982年 | 41篇 |
1981年 | 46篇 |
1980年 | 41篇 |
1979年 | 43篇 |
1978年 | 30篇 |
1977年 | 41篇 |
1976年 | 51篇 |
1975年 | 47篇 |
1974年 | 47篇 |
1972年 | 26篇 |
1970年 | 32篇 |
排序方式: 共有3663条查询结果,搜索用时 10 毫秒
21.
22.
23.
24.
Although the basal ganglia have been shown to be critical for the expression of emotion in prosody and facial expressions, it is unclear whether they are also critical for recognition of emotions. Selective pathology of parts of the basal ganglia is a hallmark of individuals with Parkinson's disease, and such patients have been examined in several studies of emotion. We examined 18 patients with Parkinson's disease (11 men, 7 women) and 13 age-, education-, gender ratio-, and IQ-matched normal controls on their ability to recognize emotions signaled by facial expressions. Parkinson's patients performed entirely normally on a quantitative task of recognizing emotional facial expressions. The findings do not support the notion that the sectors of basal ganglia that are dysfunctional in Parkinson's disease are essential for recognizing emotion in facial expressions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
The specific heat at constant volume cv shows a weak singularity at the critical point. Renormalization group techniques have been applied, predicting a universal critical behavior which has to be experimentally confirmed for different systems. In this paper an experiment is presented to measure the specific heat of SF6 along the critical isochore (c=0.737 g·cm–3), applying a continuous heating method. The results cover a temperature span of –1.5×10–2< <1.70×10–2 [=(T–T
c)/T
c] and were strongly affected by gravity effects that emerge in the sample of 1-mm hydrostatic height near the critical point. Using regression analysis, data were fitted with functions of the form c
v/R=A × ¦¦– + B for the one-phase state and c
v/R=A × ¦¦– + B for the twophase state. Within their error bounds the critical values (==0.098, A/A=1.83) represent the measurements for the temperature span 3.5×10–5< ¦¦<2.0×10
–3, in good agreement with theoretical predictions. In order to exclude density profiles in the specimen, which are unavoidable in terrestrial experiments due to the high compressibility of fluids at the critical point and the gravity force, a space-qualified scanning ratio calorimeter has been constructed, which will permit long-term cv measurements under microgravity (-g) conditions. The experiment will be part of the German Spacelab mission in October 1985. The significant features of the apparatus are briefly sketched.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献
26.
Ralph W. Howard C. A. McDaniel Dennis R. Nelson Gary J. Blomquist Leslie T. Gelbaum Leon H. Zalkow 《Journal of chemical ecology》1982,8(9):1227-1239
The cuticular hydrocarbon components of four castes ofReticulitermes virginicus (Banks) have been identified and quantitated. Components identified includen-alkanes; 2-, 3-, 11-, 13-, and 15-methyl-alkanes; 11,15-dimethylalkanes, (Z)-9-alkenes; (Z,Z)-7,9-dienes; and (E/Z)-6,9-dienes ranging in carbon number from C21 to C40. All caste forms ofR.virginicus contained the same components, but showed caste-specific proportions. Comparison of these hydrocarbons with those of the sympatric termiteR. flavipes (Kollar) suggest that cuticular hydrocarbons might serve as species- and caste-recognition cues. A bioassay was developed to test this species-recognition hypothesis, with the experimental results supporting the hypothesis.Isoptera: Rhinotermitidae. 相似文献
27.
Mass transfer rates were determined in a 3.4 cm i.d. trickle-bed reactor in the absence of reaction by absorption measurements and in presence of reaction. Gas flow rates were varied from 0-100 l/h and liquid flow rates from 0-1.5 l/h. The catalyst particles were crushed to an average diameter of 0.054 and 0.09 cm. Mass transfer coefficients remained unaffected by change in gas flow rate but increased with liquid rate. The data from absorption measurements were evaluated with predictions based upon plug-flow and axial dispersion model. Mass transfer coefficients were found greater in case of axial dispersion model than that of plug-flow model specially at low Reynolds number (Re1 < 1).Hydrogenation of α-methylstyrene to cumene using a Pd/Al2O3 catalyst was taken as a model reaction. Intrinsic kinetic studies were made in a laboratory-stirred-autoclave. Mass transfer coefficients were determined using these intrinsic kinetic data from the process kinetic measurements in trickle-bed reactor. Mass transfer coefficients under reaction conditions were found to be considerably higher than those obtained by absorption measurements.Correlations were suggested for predicting mass transfer coefficients at low Reynolds number.The gas to liquid mass transfer coefficients for lower gas and liquid flow rates were determined in a laboratory trickle-bed reactor. The effect of axial dispersion on mass transfer was considered in order to evaluate the experimental data. Three correlations were formulated to calculate the mass transfer coefficients, which included the effect of liquid loading, particle size and the properties of the reacting substances. The gas flow rate influences the gas to liquid mass transfer only in the region of low gas velocities. In the additional investigations of gas to liquid mass transfer without reaction in trickle-bed reactor, the mass transfer coefficients were determined under reaction conditions and the intrinsic kinetics was studied in a laboratory scale stirred autoclave with suspended catalyst. A few correlations are formulated for the mass transfer coefficients. A comparison with the gas-liquid mass transfer coefficient obtained by absorption measurements showed considerable deviations, which were illustrated phenomenologically. 相似文献
28.
The existence of fullerenes (as allotropes of carbon) was established in the mid-1980s and during the last 15–18 years, systematic efforts have been devoted to improve the methods of their synthesis, including plasma-based system methods. The work presented here is focused on the investigation of fullerenes synthesis, using a radio frequency plasma reactor. The main objectives were to explore the use of induction plasma technology for the synthesis in-continuo of carbon fullerenes and to predict their formation conditions through conduct of theoretical studies. Thus, a thermodynamic study was carried out to predict the equilibrium composition of fullerenes produced at several combinations of operating conditions. Additionally, a statistical factorial design experiment, employing four factors at two levels, was also developed, in order to study the influence of the system’s operating parameters on the eventual C60 fullerene yield. The results obtained showed that the reactor pressure, the electrical power and the raw material feed rates all have an important effect on the synthesis of fullerenes. The highest C60 concentration in the products was found to be about 7.7 wt.%. Various other carbon nanostructures, such as nanotubes and nano-onions, were also successfully produced. 相似文献
29.
Summary The preparation of epoxy fatty acid ester plasticizers has been reviewed. These plasticizers can be prepared by epoxidation
reactions, utilizing a preformed peracid or anin-situ technique. A newin-situ epoxidation process, utilizing hydrogen peroxide and acetic acid in the presence of strong acid catalyst, has been described.
Excellent conversions to epoxide have been achieved with a series of monounsaturated and polyunsaturated esters.
Epoxy fatty acid esters are excellent plasticizers for vinyl resins. Their performance in a series of additional epoxy plasticizers
of vegetable and marine origin is described. Novel epoxy plasticizers based upon mixed acetylated mono- and di-glyceride have
been prepared and are found to have excellent plasticizer performance.
Presented at the 28th fall meeting, American Oil Chemists’ Society, October 1954, Minneapolis, Minn. 相似文献
30.