全文获取类型
收费全文 | 1524篇 |
免费 | 27篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 61篇 |
综合类 | 2篇 |
化学工业 | 291篇 |
金属工艺 | 46篇 |
机械仪表 | 25篇 |
建筑科学 | 25篇 |
能源动力 | 35篇 |
轻工业 | 74篇 |
水利工程 | 11篇 |
无线电 | 209篇 |
一般工业技术 | 320篇 |
冶金工业 | 325篇 |
原子能技术 | 35篇 |
自动化技术 | 99篇 |
出版年
2022年 | 3篇 |
2021年 | 18篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 56篇 |
2012年 | 41篇 |
2011年 | 65篇 |
2010年 | 42篇 |
2009年 | 60篇 |
2008年 | 51篇 |
2007年 | 48篇 |
2006年 | 57篇 |
2005年 | 36篇 |
2004年 | 26篇 |
2003年 | 35篇 |
2002年 | 47篇 |
2001年 | 36篇 |
2000年 | 45篇 |
1999年 | 38篇 |
1998年 | 131篇 |
1997年 | 87篇 |
1996年 | 75篇 |
1995年 | 41篇 |
1994年 | 42篇 |
1993年 | 39篇 |
1992年 | 27篇 |
1991年 | 26篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 21篇 |
1976年 | 22篇 |
1974年 | 4篇 |
1970年 | 5篇 |
1967年 | 3篇 |
排序方式: 共有1558条查询结果,搜索用时 312 毫秒
101.
H. Imai M. Okaji T. Kishii H. Sagara H. Aikawa R. Kato 《International Journal of Thermophysics》1990,11(5):937-947
An interlaboratory testing program on the measurement of the linear thermal expansion coefficient of low-expansion glasses has been carried out. Three different types of interferometric dilatometers, each located at three different organizations, and two kinds of low-expansion glass materials were selected for the experiments. As a result of the comparison, a reasonable agreement among the different measuring instruments was confirmed, and it was determined that the thermal expansion coefficient for low-expansion glasses can be measured with an accuracy of ±4×10–8 K–1 by using commercially available interferometric dilatometers. 相似文献
102.
103.
A homogeneous and disordered assembly of densely packed nanocrystals is generated without the assistance of organic molecules, from an aqueous solution at room temperature. The densely packed nanocrystals of tin dioxide (SnO2) and titanium dioxide (TiO2), 2–3 nm in size, form glassy macroscopic transparent objects of 2–10 mm. The monodisperse nanocrystals, which have a surface hydrated layer and are synthesized in aqueous solution, are densely packed in an homogeneous and disordered assembly through the evaporation of water as the dispersion medium. The formation of transparent bulk objects on the macroscopic scale originates from the homogeneous and disordered nature of the densely packed nanocrystals. The resultant homogeneous architectures are distinguishable from the typical inhomogeneous and disordered aggregates of nanoparticles observed after evaporation of the dispersion medium. Among superstructures based on nanocrystals, such as superlattices and mesocrystals, the resultant homogeneous and disordered assembly can be regarded as a new class of solid‐state material. 相似文献
104.
Kosodo Y Imai K Hirata A Noda Y Takatsuki A Adachi H Yoda K 《Yeast (Chichester, England)》2001,18(11):1003-1014
Saccharomyces cerevisiae Sly1 protein is a member of the Sec1/Munc18-family proteins, which are essential for vesicular trafficking, but their exact biological roles are yet to be determined. A temperature-sensitive sly1 mutant arrests the vesicular transport from the ER to Golgi compartments at 37 degrees C. We screened for multicopy suppressor genes that restore the colony formation of the sly1(ts) mutant to discover functionally interacting components. The suppressor genes obtained were classified as: (1) those that encode a multifunctional suppressor, SSD1; (2) heat shock proteins, SSB1 and SSB2; (3) cell surface proteins, WSC1, WSC2 and MID2; (4) ER-Golgi transport proteins, USO1 and BET1; and (5) an as-yet-uncharacterized protein, HSD1 (high-copy suppressor of SLY1 defect 1). By epitope tagging of the gene product, we found that Hsd1 protein is an ER-resident membrane protein. Its overproduction induced enlargement of ER-like membrane structures. 相似文献
105.
EDTA saturated with Ca(2+), Fe(3+) or Cu(2+) can induce parthenogenetic activation of pig oocytes at the germinal vesicle stage, whereas EDTA saturated with Zn(2+), which is unable to chelate Zn(2+), does not, indicating that chelation of Zn(2+) with EDTA saturated with Ca(2+) (Ca-EDTA) in maturing pig oocytes plays a pivotal role in the induction of parthenogenetic activation of oocytes. In the present study, the involvement of Zn(2+) chelation in the induction of parthenogenetic activation of pig oocytes at the germinal vesicle stage was confirmed first by examining the effects of concomitant addition of Zn(2+), Cu(2+) or Ni(2+) at various concentrations together with 1 mmol Ca-EDTA l(-1) to the maturation medium. The titration experiments revealed that the pronuclear formation induced by 1 mmol Ca-EDTA l(-1) was completely inhibited by the addition of > 30 micromol Zn(2+) l(-1) to the medium, but not by the addition of Cu(2+) and Ni(2+) at any concentration examined. Second, bovine and mouse oocytes at the germinal vesicle stage were cultured in medium with or without 1 mmol Ca-EDTA l(-1) for 48 h to examine the effects of Ca-EDTA treatment on these oocytes during maturation culture. Most (70-86%) of the bovine oocytes that underwent germinal vesicle breakdown matured to the MII stage via the MI phase, regardless of whether Ca-EDTA was present for the first 24 h of culture. However, 61% of oocytes that had been cultured with Ca-EDTA for 48 h formed a pronucleus without a second polar body, whereas oocytes cultured in the absence of Ca-EDTA were not observed to form a pronucleus at any time during culture. However, even when mouse oocytes at the germinal vesicle stage were cultured for up to 48 h in maturation medium containing Ca-EDTA, pronuclear formation was not observed. Finally, when bovine oocytes that had been cultured with 1 mmol Ca-EDTA l(-1) for 48 h from the germinal vesicle stage were cultured further in medium without Ca-EDTA that was supplemented with 5% fetal calf serum, only 26% of the oocytes developed to the cleaved stage, and none could develop further. 相似文献
106.
Yasuda K Nakamoto T Yasuhara M Okada H Nakajima T Kanzaki H Hori M Ozaki H 《Reproduction (Cambridge, England)》2007,133(4):797-806
To assess the role of protein kinase Cbeta (PKCbeta) in human myometrial contractions during pregnancy, we evaluated the effect of a PKCbeta inhibitor (LY333531) on the pregnant and nonpregnant myometrial contractions and compared the level of PKCbeta in the pregnant myometrium with that in the nonpregnant myometrium. The effects of LY333531 on the myometrial contractions were examined by measuring contractile activity (frequency and amplitude). PKCbeta in human myometrium was assessed at mRNA level using real-time PCR method. The characteristics of contractile activity were different between the pregnant and the nonpregnant myometrium. The amplitude of rhythmic contractions in the preterm and term myometrium was increased 2- to 2.5-fold when compared with that in the nonpregnant myometrium, but the frequency of rhythmic contractions was decreased by about half. LY333531 (10(-6) M) reduced the increased amplitude in the preterm and term myometrium by about 50%, and the inhibitory effects of LY333531 in the pregnant myometrium were significantly greater than that in the nonpregnant myometrium (about 50 vs 25%). However, the frequency in the pregnant and nonpregnant myometrium was not influenced by LY333531. Real-time PCR revealed a significant, five- to sevenfold increase in the expression of PKCbeta mRNA in the preterm and term myometrium when compared with the nonpregnant myometrium. These findings suggest that the increased amplitude of human myometrial contractions during pregnancy is related to the increased level of PKCbeta. A PKCbeta inhibitor may reduce preterm uterine contractions and prevent preterm delivery. 相似文献
107.
In this paper, a back propagation neural network (BPNN) has been applied to predict the corner wear of a high speed steel (HSS) drill bit for drilling on different workpiece materials. Specially defined static and dynamic features extracted by a wavelet packet transform (WPT) from the resultant force converted from thrust and torque together with the cutting conditions (workpiece material, spindle speed, drill diameter, feed rate) are used as inputs to train the network to obtain a better output, drill corner wear. Drilling experiments have been carried out over a wide range and, features newly defined and conventional ones, features extracted from different frequency bands are compared. 相似文献
108.
Isolation and characterization of poly(butylene succinate-co-butylene adipate)-degrading microorganism 总被引:1,自引:0,他引:1
Hayase N Yano H Kudoh E Tsutsumi C Ushio K Miyahara Y Tanaka S Nakagawa K 《Journal of Bioscience and Bioengineering》2004,97(2):131-133
Poly(butylene succinate-co-butylene adipate) (PBSA)-degrading bacterium, strain 1-A, was isolated from soil. Strain 1-A was identified as Bacillus pumilus on the basis of its physiological properties and partial 16S rRNA gene sequence. Strain 1-A also degraded poly(butylene succinate) (PBS) and poly(epsilon-caprolactone). On the other hand, poly(butylene adipate terephthalate) and poly(lactic acid) were minimally degraded by strain 1-A. The NMR spectra of degradation products from PBSA indicated that the adipate units were more rapidly degraded than 1,4-butanediol and succinate units. This seems to be one of the reasons why strain 1-A degraded PBSA faster than PBS. 相似文献
109.
S. Baunack D. Balaguer Ríos L. Capozza J. Diefenbach R. Frascaria B. Glser D.v. Harrach Y. Imai R. Kothe R. Kunne J.H. Lee F.E. Maas M.C. Mora Espí M. Morlet S. Ong E. Schilling J. van de Wiele C. Weinrich 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,640(1):561
110.
Kazuhiko Suzuki S. Seto A. Iwata M. Bingo T. Sawada K. Imai 《Journal of Electronic Materials》2000,29(6):704-707
The electron drift mobility of undoped Cd0.9Zn0.1Te grown by high-pressure Bridgman method is measured by a time-of-flight technique. The sample shows a room temperature mobility
and mobility lifetime product of 950 cm2/Vs and 1.6 × 10−4cm2/V, respectively. The mobility increases monotonically with decreasing temperature to 3000 cm2/Vs at 100 K. The dominant scattering mechanism for the electron transport is discussed by comparing with the theoretical
mobility obtained by iterative solution of the Boltzmann equation. 相似文献