全文获取类型
收费全文 | 33683篇 |
免费 | 1771篇 |
国内免费 | 42篇 |
专业分类
电工技术 | 252篇 |
综合类 | 21篇 |
化学工业 | 6714篇 |
金属工艺 | 643篇 |
机械仪表 | 713篇 |
建筑科学 | 940篇 |
矿业工程 | 72篇 |
能源动力 | 591篇 |
轻工业 | 5500篇 |
水利工程 | 329篇 |
石油天然气 | 119篇 |
武器工业 | 5篇 |
无线电 | 1281篇 |
一般工业技术 | 5688篇 |
冶金工业 | 8001篇 |
原子能技术 | 135篇 |
自动化技术 | 4492篇 |
出版年
2024年 | 78篇 |
2023年 | 296篇 |
2022年 | 316篇 |
2021年 | 789篇 |
2020年 | 669篇 |
2019年 | 760篇 |
2018年 | 1352篇 |
2017年 | 1322篇 |
2016年 | 1379篇 |
2015年 | 1057篇 |
2014年 | 1236篇 |
2013年 | 2628篇 |
2012年 | 1963篇 |
2011年 | 1773篇 |
2010年 | 1462篇 |
2009年 | 1300篇 |
2008年 | 1270篇 |
2007年 | 1201篇 |
2006年 | 803篇 |
2005年 | 684篇 |
2004年 | 650篇 |
2003年 | 565篇 |
2002年 | 563篇 |
2001年 | 417篇 |
2000年 | 388篇 |
1999年 | 442篇 |
1998年 | 2374篇 |
1997年 | 1624篇 |
1996年 | 1044篇 |
1995年 | 621篇 |
1994年 | 475篇 |
1993年 | 564篇 |
1992年 | 210篇 |
1991年 | 205篇 |
1990年 | 155篇 |
1989年 | 158篇 |
1988年 | 163篇 |
1987年 | 137篇 |
1986年 | 123篇 |
1985年 | 144篇 |
1984年 | 130篇 |
1983年 | 100篇 |
1982年 | 134篇 |
1981年 | 148篇 |
1980年 | 159篇 |
1979年 | 84篇 |
1978年 | 88篇 |
1977年 | 282篇 |
1976年 | 627篇 |
1973年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Dr. Z. Zemánek 《Acta Mechanica》1996,115(1-4):151-159
Summary The use of holographic interferometry for the measurement of large deformations is described. From the nature of holographic interferometry it is evident that large deformations exceed the wave length of the light source used by at least ten times of this size. To obtain holographically identifiable values of large deformations, a method of successive partial lighting is used. It shows how it is possible to keep all the advantages of the holographic method and use it even under conditions which apparently exceed its possibilities of application. 相似文献
102.
The universal bio-optical algorithm of the Coastal Zone Color Scanner (CZCS) for case I waters implicitly contains an average covariance of the absorption by phytoplankton and colored dissolved organic matter (CDOM) and detritus. We made that covariance explicit by combining the CZCS algorithm with an expression for reflectance. The spectral variation of absorption by CDOM plus detritus for case I waters may be estimated by the expression a(gd(λ)) = 2a(ph)(443)*chl{exp[-0.013(λ - 443)]. 相似文献
103.
104.
JA Ortu?o-Cortés L Quintana-Tomás A García-García 《Canadian Metallurgical Quarterly》1996,19(2):47-51
1.5% Capsaicin (Cap) or Vehicle was respectively used to treat the right or left sciatic nerve in 20 Sprague-Dawley rats. On the seventh day, the 20 rats were at random divided into electroacupuncture (EA) group and non-EA group, the spinal cord corresponding to the afferent segments of sciatic nerve was taken out for observing the changes of acetylcholinesterase (AChE) activity and [3H]-quinuelidinylbenzylate (QNB) binding sites in the spinal dorsal horn (SDH). The results were as follows: (1) EA "Huantiao" could enhance AChE activity in the SDH and decrease [3H]-QNB binding sites; (2) Cap treating sciatice nerve could weaken AChE activity in the SDH and merease [3H]-QNB binding sites; (3) Cap treatment could inhibit or partially inhibit the actions of EA as above. The results indicated that ACh participated in the primary afferent of acupuncture information and might exist in Cap-sensitive neurons. 相似文献
105.
The Neurospora crassa Asm-1+ (ascospore maturation 1) gene encodes an abundant nucleus-localized protein required for formation of female structures and for ascospore maturation. Deletion mutants of Asm-1+ are "ascus-dominant," i.e., when crossed to wild type, neither Asm-1+ nor Asm-1 delta spores mature. To explain this behavior, we considered three models: an effect of reduced dosage of the gene product, failure of internuclear communication, and failure of transvection (regulation dependent on pairing of alleles). We found that for proper regulation of subsequent sexual sporulation, Asm-1+ must be in proximity, probably paired, to its allelic counterpart in the zygote: i.e., transvection must occur. Disruption of pairing causes failure of ascospore progeny to mature. Transvection in Neurospora, unlike in Drosophila, occurs immediately before meiosis, and can be demonstrated between wild-type alleles. 相似文献
106.
The effect of the removal of pineal gland, performed in adult age or during perinatal life, was investigated in the neonatal androgen sterility (NA-CEA) syndrome, in combination with drugs acting on serotonergic neurons. Perinatal pinealectomy (Px) was more potent in preventing the development of NA-CEA state than Px performed in the adult age. These data indicate that the masculinized hypothalamus becomes less sensitive to pineal influences during the lifespan. Effect of Px was potentiated by drugs increasing the central serotonergic tone. The results lead to the assumption that pineal hormones are influential on the maturation of serotonergic neurons, which might interfere with the sterilizing property of neonatal androgen treatment during the "critical" period of sexual differentiation. 相似文献
107.
Monoclonal antibodies (MoAbs) against potato virus A (PVA) were examined in their reactivity with PVA and its denatured capsid protein (PVA-CP) bound to the nitrocellulose membrane. Five MoAbs reacted with native PVA, three of them also with PVA-CP. One MoAb gave no reaction in dot-blot test. In polyacrylamide electrophoresis in the presence of sodium dodecyl sulphate (SDS-PAGE) PVA-CP migrated as two major bands. In immunoblot analysis, two MoAbs reacted only with the slower band, one only with the faster one. We presume that those bands do not correspond to the intact CP but they do to truncated N- and C-terminal CP molecules, respectively, and that the corresponding epitopes reacting with MoAbs are localized near to both termini of CP molecules. After mild trypsinolysis of PVA particles no MoAb reacted with resulting "core" CP. 相似文献
108.
109.
An adaptive, real-time, traffic monitoring system 总被引:1,自引:0,他引:1
In this paper we describe a computer vision-based traffic monitoring system able to detect individual vehicles in real-time.
Our fully integrated system first obtains the main traffic variables: counting, speed and category; and then computes a complete
set of statistical variables. The objective is to investigate some of the difficulties impeding existing traffic systems to
achieve balanced accuracy in every condition; i.e. day and night transitions, shadows, heavy vehicles, occlusions, slow traffic
and congestions. The system we present is autonomous, works for long periods of time without human intervention and adapts
automatically to the changing environmental conditions. Several innovations, designed to deal with the above circumstances,
are proposed in the paper: an integrated calibration and image rectification step, differentiated methods for day and night,
an adaptive segmentation algorithm, a multistage shadow detection method and special considerations for heavy vehicle identification
and treatment of slow traffic. A specific methodology has been developed to benchmark the accuracy of the different methods
proposed. 相似文献
110.
M. Fernández-Delgado M. Reboreda E. Cernadas S. Barro 《Neural computing & applications》2010,19(5):741-754
In the industrial environment, specifically in the automotive industry, an accurate prediction of execution times for each
production task is very useful in order to plan the work and to optimize the human, technical and material resources. In this
paper, we applied several regression neural networks to predict the execution times of the tasks in the production of parts
for plastic injection molds. These molds are used to make a variety of car components in automotive industry. The prediction
is based on the geometric features of the mold parts to be made. The accuracy of the predicted times is high enough to be
used as a tool for the design stage of the mold parts, e.g. guiding the design process in order to get the lowest production
time. 相似文献