全文获取类型
收费全文 | 6410篇 |
免费 | 324篇 |
国内免费 | 246篇 |
专业分类
电工技术 | 219篇 |
综合类 | 218篇 |
化学工业 | 1547篇 |
金属工艺 | 582篇 |
机械仪表 | 267篇 |
建筑科学 | 199篇 |
矿业工程 | 50篇 |
能源动力 | 168篇 |
轻工业 | 377篇 |
水利工程 | 16篇 |
石油天然气 | 216篇 |
武器工业 | 28篇 |
无线电 | 390篇 |
一般工业技术 | 1636篇 |
冶金工业 | 201篇 |
原子能技术 | 60篇 |
自动化技术 | 806篇 |
出版年
2024年 | 16篇 |
2023年 | 116篇 |
2022年 | 309篇 |
2021年 | 265篇 |
2020年 | 105篇 |
2019年 | 113篇 |
2018年 | 108篇 |
2017年 | 130篇 |
2016年 | 137篇 |
2015年 | 158篇 |
2014年 | 214篇 |
2013年 | 318篇 |
2012年 | 331篇 |
2011年 | 430篇 |
2010年 | 351篇 |
2009年 | 425篇 |
2008年 | 392篇 |
2007年 | 446篇 |
2006年 | 417篇 |
2005年 | 294篇 |
2004年 | 227篇 |
2003年 | 237篇 |
2002年 | 217篇 |
2001年 | 153篇 |
2000年 | 132篇 |
1999年 | 122篇 |
1998年 | 94篇 |
1997年 | 68篇 |
1996年 | 70篇 |
1995年 | 64篇 |
1994年 | 49篇 |
1993年 | 45篇 |
1992年 | 76篇 |
1991年 | 48篇 |
1990年 | 57篇 |
1989年 | 35篇 |
1988年 | 23篇 |
1987年 | 45篇 |
1986年 | 55篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 2篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有6980条查询结果,搜索用时 15 毫秒
81.
Arnon Shani 《Journal of chemical ecology》1990,16(3):971-980
A cotton wool plug, used as the source for pheromone release, was placed in closed 1-quart Mason jars, either at the mouth or at the rear of the jar. Air sampling of the two components of the sex pheromone (total 2.2 mg at the source) of the almond moth (Ephestia cautella) female showed that the saturation period near the source in still air was 20–22 hr and that far from the source was 40–50 hr, reaching a level of less than 1 ng/ml air. The ratio between the components (Z,E)-9,12-tetradecadienyl acetate, designated D, and (Z)-9-tetradecenyl acetate designated M, in the air was close to the original ratio for both sampling sites, albeit somewhat richer in the more volatile (Z)-9-tetradecenyl acetate (source 77.023.0 DM, air 73.0– 74.327.0–25.7; source 80.119.9, air 77.622.4; source 25.174.9, air 23.976. 1 DM). The total amount of pheromone per milliliter of air was two to three times larger near the source than far from it at the early stages of the evaporation and saturation process. When the amount of pheromone applied to the source was tripled (7 mg), the amount far from the source was almost tripled, or the saturation time was cut by factor of two to three. 相似文献
82.
A novel technique of immobilizing indicator dyes by electrostatic adsorption and covalent bonding to fabricate optical sensors
was developed. 3-Amino-9-ethylcarbazole (AEC) was attached to the outmost surface of quartz glass slide via aminosilanizing
the slide, crosslinking chitosan, adsorbing Au nanoparticle, self-assembling HS(CH2)11OH, and coupling AEC. Thus, an AEC-immobilized optical sensor was obtained. The sensor exhibits a wide linear response range
from 7.0×10−7 to 1.0×10−4 mol/L and a correlation coefficient of 0.995 9 for the detection of 2-nitrophenol. The detection limit and response time
of the sensor are 1.0×10−7 mol/L and less than 10 s, respectively. The fluorescence intensity of the used sensor can be restored to the blank value
by simply rinsing with blank buffer. A very effective matrix for immobilizing indicator dye is provided by the proposed technique,
which is adaptable to other indicator dyes with amino groups besides AEC.
Foundation item: Project(20775010) supported by the National Natural Science Foundation of China; Project(208095) supported by the Key Project
of Ministry of Education, China; Project(07A006) supported by the Scientific Research Fund of Hunan Provincial Education Department,
China; Project(07JJ3020) supported by Hunan Provincial Natural Science Foundation of China 相似文献
83.
通过添加不同含量的稀土元素,对比研究稀土含量对9Cr2Mo钢奥氏体晶粒度、相变点、抗拉强度及耐磨性的影响。研究结果表明,稀土元素可以有效细化9Cr2Mo钢的奥氏体晶粒,当稀土加入量为0.10%时,晶粒长大速率降低最明显。添加质量分数为0.1%的稀土后,9Cr2Mo钢的抗拉强度明显提高,塑性和延展性也有所改善。加入稀土元素后,9Cr2Mo钢在磨损过程中可以避免出现大块疲劳剥落现象,提高了耐磨性。 相似文献
84.
袁秀莲 《河南机电高等专科学校学报》2010,18(5):20-23
随着嵌入式系统的迅速发展,其游戏娱乐功能越来越受到重视。ARM系统是一种典型的嵌入式系统,在ARM微处理器S3C2410硬件平台和WinCE操作系统上,设计并实现了"俄罗斯方块"游戏,包括总体设计、算法实现、游戏测试等,着重介绍了游戏中的数据结构、图形处理、游戏控制等的实现技术。 相似文献
85.
86.
A good performance of the solid‐liquid unit operation is required for the economical exploitation of the Bayer process. A computational fluid dynamics (CFD) model simulating the operation of the last washing stage mud thickener of a large Canadian alumina plant is presented. The parametric study of the impact of changes in four parameters shows that the diameter of flocculated red mud particles, the feed flow rate and the radius of the feed well are critical parameters for the operation of the thickener. 相似文献
87.
An experimental method is proposed to characterize the diffusional transfer of adsorbable gaseous solute medium in a porous medium. Three types of experimental measurements are used to successively access to the solute apparent diffusivity in the gas phase, in the adsorbed phase and to check whether the hypothesis of the thermodynamic equilibrium between the gas phase solute and the adsorbed solute is verified during the transient transfer process. This methodology is applied to a longitudinal section of a beech wood sample for the water transfer in the wood hygroscopic domain. 相似文献
88.
Ashraf El-Sayed Josef Gödde Peter Witzgall Heinrich Arn 《Journal of chemical ecology》1999,25(2):389-400
The behavioral responses of Lobesia botrana males to calling females, pheromone gland extracts, and synthetic sex pheromones were recorded in a wind tunnel. Gland extracts and synthetic pheromones were released from a pheromone evaporator. The numbers of males reaching the source and their flight tracks in response to calling females and pheromone gland extracts were compared to those of synthetic blends. Upwind flights to natural sex pheromone were straighter and faster than to a three-component blend of (E)-7,(Z)-9-dodecadienyl acetate (E7,Z9–12:Ac), (E)-7,(Z)-9-dodecadien-1-ol (E7,Z9–12:OH), and (Z)-9-docecenyl acetate (Z9–12:Ac) (100:20:5). The optimum ratio of E7,Z9–12:OH and Z9–12:Ac to E7,Z9–12:Ac was found to be 5% and 1%, respectively. An additional seven compounds identified in the sex pheromone gland were investigated for their biological activity. Two unsaturated acetates, i.e., (E)-9-dodecenyl acetate (E9–12:Ac) and 11-dodecenyl acetate (11–12:Ac), increased the number of males reaching the source as well as straightness, linear velocity, and decreased the track angle of upwind flight. Optimum response was obtained by releasing 10 pg/min E7,Z9–12:Ac in a mixture with 0.5 pg/min E7,Z9–12:OH, 0.1 pg/min Z9–12:Ac, 0.1 pg/min E9– 12:Ac and 1 pg/min 11-12–Ac. The saturated acetates previously identified in the female glands were biologically inactive. 相似文献
89.
Gerhard Gries John Clearwater Regine Gries Grigori Khaskin Skip King Paul Schaefer 《Journal of chemical ecology》1999,25(5):1091-1104
In 1996, the exotic white-spotted tussock moth (WSTM), Orgyia thyellina (Lepidoptera: Lymantriidae), was discovered in Auckland, New Zealand. Because establishment of WSTM would threaten New Zealand's orchard industry and international trade, eradication of WSTM with microbial insecticide was initiated. To monitor and complement eradication of WSTM by capture of male moths in pheromone-baited traps, pheromone components of female WSTM needed to be identified. Coupled gas chromatographic–electroantennographic detection analysis of pheromone gland extract revealed several compounds that elicited responses from male moth antennae. Mass spectra of the two most EAD-active compounds suggested, and comparative GC-MS of authentic standards confirmed, that they were (Z)-6-heneicosen-11-one (Z6–11-one) and (Z)-6-heneicosen-9-one, the latter termed here thyellinone. In field experiments in Japan, Z6–11-one plus thyellinone at a 100:5 ratio attracted WSTM males, whereas either ketone alone failed to attract a single male moth. Addition of further candidate pheromone components did not enhance attractiveness of the binary blend. Through the 1997–1998 summer, 45,000 commercial trap lures baited with 2000 g of Z6–11-one and 100 g of thyellinone were deployed in Auckland towards eradication of the residual WSTM population.Dedicated to my dear mother in honor of her 75th birthday 相似文献
90.
Yorianta Sasaerila Regine Gries Gerhard Gries Grigori Khaskin Skip King Teo Chor Boo 《Journal of chemical ecology》2000,26(8):1969-1981
This study was undertaken to identify sex pheromone components of nettle caterpillars Darna trima and Darna bradleyi (Lepidoptera: Limacodidae) whose larvae defoliate oil palm, Elaeis guineensis, in southeast Asia. Coupled gas chromatographic–electroantennographic detection (GCEAD) analyses of pheromone gland extracts revealed two antennally active compounds produced by female D. trima and two by female D. bradleyi. Molecular structures of these candidate pheromone components were identified by electron-impact and chemical-ionization mass spectrometry; retention-index calculations on DB-5, DB-23, and DB-210 columns; microanalytical treatments, as well as syntheses of "auxilliary" compounds that facilitated identification of the compounds. The compounds from D. trima were 2-methylbutyl (E)-7,9-decadienoate (A) and (E)-2-hexenyl (E)-7,9decadienoate (B); from D. bradleyi we identified methyl (E)-7,9-decadienoate (C), and isobutyl (E)-7,9-decadienoate (D). In field experiments in Malaysia, (S)-2-methylbutyl (E)-7,9-decadienoate (SA) in combination with B proved to be essential and synergistic pheromone components for attraction of male D. trima. (R)-2-Methylbutyl (E)-7,9-decadienoate (RA) had no behavioral activity. Compound D singly attracted male D. bradleyi, but addition of C to D at a 1 : 10 ratio significantly enhanced attractiveness of the bait. Synthetic pheromone blends were more effective trap baits than unmated female moths and could be developed for monitoring populations of D. trima and D. bradleyi in Asian oil palm plantations. 相似文献