全文获取类型
收费全文 | 8180篇 |
免费 | 410篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 117篇 |
综合类 | 17篇 |
化学工业 | 1564篇 |
金属工艺 | 236篇 |
机械仪表 | 372篇 |
建筑科学 | 266篇 |
矿业工程 | 11篇 |
能源动力 | 372篇 |
轻工业 | 716篇 |
水利工程 | 39篇 |
石油天然气 | 14篇 |
武器工业 | 2篇 |
无线电 | 1371篇 |
一般工业技术 | 1598篇 |
冶金工业 | 589篇 |
原子能技术 | 67篇 |
自动化技术 | 1259篇 |
出版年
2024年 | 12篇 |
2023年 | 98篇 |
2022年 | 139篇 |
2021年 | 248篇 |
2020年 | 191篇 |
2019年 | 176篇 |
2018年 | 234篇 |
2017年 | 219篇 |
2016年 | 275篇 |
2015年 | 251篇 |
2014年 | 356篇 |
2013年 | 561篇 |
2012年 | 538篇 |
2011年 | 568篇 |
2010年 | 457篇 |
2009年 | 437篇 |
2008年 | 461篇 |
2007年 | 392篇 |
2006年 | 318篇 |
2005年 | 287篇 |
2004年 | 257篇 |
2003年 | 243篇 |
2002年 | 195篇 |
2001年 | 155篇 |
2000年 | 154篇 |
1999年 | 146篇 |
1998年 | 236篇 |
1997年 | 159篇 |
1996年 | 150篇 |
1995年 | 102篇 |
1994年 | 73篇 |
1993年 | 77篇 |
1992年 | 53篇 |
1991年 | 44篇 |
1990年 | 35篇 |
1989年 | 36篇 |
1988年 | 34篇 |
1987年 | 34篇 |
1986年 | 10篇 |
1985年 | 27篇 |
1984年 | 19篇 |
1983年 | 18篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 18篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1974年 | 8篇 |
排序方式: 共有8610条查询结果,搜索用时 15 毫秒
31.
GS Bhudhikanok J Lim R Marcus A Harkins RB Moss LK Bachrach 《Canadian Metallurgical Quarterly》1996,97(1):103-111
The responses to heat shock in Tritrichomonas mobilensis, a squirrel monkey parasite and Tritrichomonas augusta, an amphibian trichomonad, were evaluated by means of metabolic labeling with [35S]methionine. Electrophoretically separated trichomonad proteins synthesized at different temperatures were visualized by autoradiography and the label incorporation quantitated by a trichloroacetic acid precipitation procedure. A considerable difference in thermotolerance between the two species was found as the protein synthesis reached a maximum at 41 C in T. mobilensis and 37 C in T. augusta. The latter tolerated temperature increases 13 C above normal cultivation temperatures as compared to only 4 C thermotolerance range above normal in T. mobilensis. Major heat shock proteins (Hsps) were expressed in both T. mobilensis (with apparent Mr 94, 72, and 58 kDa) and T. augusta (Mr 94, 70, and 56 kDa) as revealed by autoradiography. Western blot analysis with polyclonal antibody against DnaK of Escherichia coli showed the presence of antigenic Hsp70 homologs in both trichomonads. Similarly, a polyclonal antibody against Hsp60 with broad interspecies cross-reactivity detected Hsp60 homologs in both T. mobilensis and T. augusta. The anti-DnaK antibody cross-reacted with a T. mobilensis protein localized in Golgi apparatus as demonstrated by immunoelectron microscopy. Immunocytochemistry on trichomonad frozen sections revealed the presence of the Hsp60 homolog in light-microscopic granules corresponding to hydrogenosomes. 相似文献
32.
33.
Integrated Microfluidic CustomArray Device for Bacterial Genotyping and Identification 总被引:2,自引:0,他引:2
34.
This paper reports two cases of neotropical echinococcosis caused by Echinococcus oligarthrus and E. vogeli, neither of which has been reported from Suriname. Case 1, a six-year-old boy, presented a 15 x 25 mm retro-ocular cystic tumor (observed by ultrasound, computed tomography scan, and magnetic resonance imaging) causing exophthalmia, chemosis, palpebral ptosis, and blindness of the left eye. Of two tentative diagnoses, Echinococcus cyst or dermoid tumor, the former was shown to be correct at surgery when a clear liquid and detached protoscoleces were aspirated. Rostellar hooks of the protoscolex were characteristic of E. oligarthrus. Case 2, a 41-year-old man, had polycystic masses excised from the liver and abdomen. A presurgery diagnosis of E. vogeli infection was made due to calcifications seen in the lesions, positive serology, residence of the patient in the tropical forest, and later by the size and shape of rostellar hooks. The presence of these two parasites in one of the former Guianas is not surprising; both species are endemic in tropical forest in Central and South America wherever people have not exterminated wild canids, especially the bush dog, (Speothos venaticus), and felids (wild cats of several species), along with pacas, agoutis, and other rodents that serve as intermediate host of these two cestodes. Eighty-six cases of polycystic echinococcosis are known in people from 11 countries from Nicaragua to Argentina: 32 due to E. vogeli, three to E. oligarthrus, and 51 for which determination of the species was not possible because the hooks of the protoscolex were not found or described. Research to elucidate aspects of transmission of E. vogeli and E. oligarthrus is of practical importance for defining measures for preventing the severe and frequently fatal illnesses caused by these two cestodes. 相似文献
35.
A micellar electrokinetic capillary chromatographic (MECC) method has been developed and optimised for the separation of 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG). The running buffer consisted of a mixture of 20 mM sodium phosphate and 20 mM sodium borate containing 50 mM sodium dodecyl sulphate (SDS) adjusted to pH 9.5 with 1 M NaOH. The running voltage and temperature were 20-25 kV and 30 degrees C, respectively. The MECC method for the analysis of PBG is fast and simple and is useful for the screening of PBG in the urine of patients suspected to have acute intermittent porphyria (AIP), and for the confirmation of lead exposure by measuring red-cell ALA-dehydratase (ALA-D) activity with ALA as the enzyme substrate. 相似文献
36.
37.
Xu Y Xu D Lin S Han TX Cao X Li X 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2012,42(3):729-739
In this paper, we study the problem of detecting sudden pedestrian crossings to assist drivers in avoiding accidents. This application has two major requirements: to detect crossing pedestrians as early as possible just as they enter the view of the car-mounted camera and to maintain a false alarm rate as low as possible for practical purposes. Although many current sliding-window-based approaches using various features and classification algorithms have been proposed for image-/video-based pedestrian detection, their performance in terms of accuracy and processing speed falls far short of practical application requirements. To address this problem, we propose a three-level coarse-to-fine video-based framework that detects partially visible pedestrians just as they enter the camera view, with low false alarm rate and high speed. The framework is tested on a new collection of high-resolution videos captured from a moving vehicle and yields a performance better than that of state-of-the-art pedestrian detection while running at a frame rate of 55 fps. 相似文献
38.
Dave McKenney Tony White 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(2):247-259
This paper investigates the speed improvements available when using a graphics processing unit (GPU) for evaluation of individuals
in a genetic programming (GP) environment. An existing GP system is modified to enable parallel evaluation of individuals
on a GPU device. Several issues related to implementing GP on GPU are discussed, including how to perform tree-based GP on
a device without recursion support, as well as the effect that proper memory layout can have on speed increases when using
CUDA-enabled nVidia GPU devices. The specific GP implementation is designed to evolve stock trading strategies using technical
analysis indicators. The second goal of this research is to investigate the possible improvement in performance when training
individuals on a larger number of stocks and training days. This increased training size (nearly 100,000 training points)
is enabled due to the speedups realized by GPU evaluation. Several different scenarios were used to test various speed optimizations
of GP evaluation on the GPU device, with a peak speedup factor of over 600 (when compared to sequential evaluation on a 2.4 GHz
CPU). Also, it is found that increasing the number of stocks and the length of the training period can result in higher out-of-training
testing profitability. 相似文献
39.
A new bioglass ceramic with composition of Na2O 12%, CaO 28%, P2O5 10% and SiO2 50% with a high bending strength (120–140 MPa) and compressive strength (600–750 MPa) was studied. The crystallized phases of-Ca2P2P7 and Na2Ca3Si6O16 were determined by X-ray diffraction. Optical microscopy of the material revealed that a very uniform crystal size of about 30 m was obtained with high nucleation frequency. The nucleation and crystallization processes were also investigated. The rat shoulder test showed that the material formed a tight chemical bond with biological texture and had good biocompatibility. 相似文献
40.
A twin-plane re-entrant corner effect (TPRE) in growth of chemical vapour deposited (CVD) -SiC is described by the film and particles of gas-phase homogeneous nucleation. The structural morphology has been characterized by scanning electron microscopy and transmission electron microscopy. Morphological characteristics of the deposited crystals, such as triangularity, hexagons or facets have been explained in terms of the re-entrant corner effect at twin junctions, which were proposed as preferential growth sites for perfect crystals. For real deposits, screw dislocations and/or the re-entrant corner effect are not expected to be compatible. The majority of chemical vapour deposited SiC crystals have a high defect density comprised of {111} twins and dislocations associated with the process variables. Infrared transmission spectra and electron spectroscopy of chemical analysis indicated that the major chemical bonds of CVD -SiC were Si-C and C-H bonds. The positions of the 1s or 2p corelevel peaks for deposits are described. 相似文献