全文获取类型
收费全文 | 1320篇 |
免费 | 30篇 |
国内免费 | 8篇 |
学科分类
工业技术 | 1358篇 |
出版年
2022年 | 8篇 |
2021年 | 14篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 22篇 |
2017年 | 13篇 |
2016年 | 15篇 |
2015年 | 25篇 |
2014年 | 31篇 |
2013年 | 89篇 |
2012年 | 43篇 |
2011年 | 54篇 |
2010年 | 57篇 |
2009年 | 55篇 |
2008年 | 87篇 |
2007年 | 59篇 |
2006年 | 48篇 |
2005年 | 40篇 |
2004年 | 42篇 |
2003年 | 39篇 |
2002年 | 28篇 |
2001年 | 31篇 |
2000年 | 24篇 |
1999年 | 25篇 |
1998年 | 34篇 |
1997年 | 36篇 |
1996年 | 30篇 |
1995年 | 22篇 |
1994年 | 27篇 |
1993年 | 27篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 20篇 |
1986年 | 23篇 |
1985年 | 18篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 18篇 |
1980年 | 24篇 |
1979年 | 20篇 |
1978年 | 17篇 |
1977年 | 5篇 |
1976年 | 12篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有1358条查询结果,搜索用时 15 毫秒
51.
Yasumasa?Minemoto Shuji?AdachiEmail author Yuji?Shimada Toshihiro?Nagao Toshio?Iwata Yoshie?Yamauchi-Sato Takaya?Yamamoto Tadashi?Kometani Ryuichi?Matsuno 《Journal of the American Oil Chemists' Society》2003,80(7):675-678
The autoxidation processes of the cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) isomers of CLA were separately observed at ca. 0% RH and different temperatures. The t10,c12 CLA oxidized faster than the c9,t11 isomer at all tested temperatures. The first half of the oxidation process of t10,c12 CLA obeyed an autocatalytic-type rate expression, but the latter half followed first-order kinetics. On the other hand,
the entire oxidation process of c9,t11 CLA could be expressed by the autocatalytic-type rate expression. The apparent activation energies and frequency factors
for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius
equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA
or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested
that the autoxidation mechanisms for the CLA and PUFA were essentially the same. 相似文献
52.
Contrasting effects of water-soluble and water-insoluble dietary fibers on bile acid conjugation and taurine metabolism in the rat 总被引:2,自引:0,他引:2
The effect of the type of dietary fiber on the bile acid and taurine metabolism was examined in rats. Diets containing 10%
of various water-soluble fibers (citrus pectin, konjak mannan, guar gum) as compared to a fiber-free diet increased biliary
excretion of total bile acids. In contrast, water-insoluble dietary fibers (cellulose, corn bran, chitin; 10% in the diets)
as well as cholestyramine (5% in the diet) considerably, decreased bile acid excretion. Water-soluble dietary fibermediated
increases in bile acid excretion were totally attributable to increases in glycine-conjugates. Thus, these fibers greatly
increased by the bile acid glycine-to-taurine ratio (G/T). Excretio of glycine conjugates decreased more than that of taurine
conjugates in rats fed various water-insoluble dietary fibers. As a results, G/T in rats fed water-insoluble fibers was significantly
lowered as compared to G/T in animals fed a fiber-free diet. Cholestyramine did not affect the G/T ratio of bile acids. Fecal
bile acid excretion and the activities of hepatic cholesterol 7α-hydroxylase (EC 1.14.13.17) in rats fed various water-soluble
dietary fibers approximately doubled as compared to the respective values for rats fed a fiber-free diet. Whereas cholestyramine
greatly increased these parameters, water-insoluble fibers did not significantly affect them. Various water-soluble fibers
decreased hepatic concentration and urinary excretion of taurine as well as the activity of hepatic cysteine dioxygenase (EC
1.13.11.20). In contrast, water-insoluble fibers considerably increased hepatic taurine concentrations and enzyme activities.
The parameters for taurine metabolism were unaffected by cholestyramine. It was suggested that the types of dietary fiber
affected hepatic taurine synthesis and thus modified bile acid glycine/taurine ratios. 相似文献
53.
54.
Tadashi Yoshihashi Nguyen Thi Thu Huong Vipa Surojanametakul Patcharee Tungtrakul Warunee Varanyanond 《Journal of food science》2005,70(1):S34-S37
ABSTRACT: The effect of package and temperature on 2–acetyl-1–pyrroline content in milled aromatic rice during storage was investigated. 2 -Acetyl-1 -pyrroline content was decreased faster at higher storage temperature. However, fat acidity of rice was increased during storage and inversely correlated with 2–acetyl-1–pyrroline content at an early stage of storage. The difference in 2–acetyl-1 -pyrroline recovery from the samples, which were extracted with ethanol at 40 °C and 75 °C, revealed that the starch bound and free forms of 2–acetyl-1–pyrroline may occur in aromatic rice. These results suggested that the biosynthesis of 2–acetyl-1 -pyrroline before starch structure formation in rice kernel could play a key role in the aroma quality of aromatic rice. 相似文献
55.
56.
Fabrication and characterization of potassium-sodium niobate piezoelectric ceramics by spark-plasma-sintering method 总被引:1,自引:0,他引:1
High density (Na1−xKx)NbO3 (x = 0.5, 0.6, and 0.7) ceramics were successfully prepared by spark-plasma-sintering (SPS) method. The dielectric and piezoelectric properties of the SPS samples were investigated and compared to that of hot-pressed samples. It is found that, the SPS-sintered (Na1−xKx)NbO3 samples show higher room temperature dielectric constant, higher coercive fields, lower remnant polarizations and lower electromechanical coefficients than that of the hot-pressed (Na1−xKx)NbO3 samples. The dielectric and piezoelectric property differences between the SPS-sintered and hot-pressed samples have been attributed to grain size effects. 相似文献
57.
Rintaro Aoyagi Hiroaki TakedaSoichiro Okamura Tadashi Shiosaki 《Materials Research Bulletin》2003,38(1):25-32
The crystal structure of Na0.5Bi2.5Nb2O9 was refined from its powder X-ray diffraction (XRD) data. Sodium bismuth niobate at 23 °C is orthorhombic, A21am, with a=5.4998(3) Å, b=5.4602(2) Å, c=24.952(1) Å, and Z=4. The piezoelectric properties were investigated using the dense bulk ceramics. The electromechanical coupling coefficients (kij) and electrical quality factors (Qm) are k31=3.2%, kt=10.0%, and Qm=3800. Single crystals were also grown from stoichiometric melts using a slow cooling technique. The dielectric and ferroelectric properties of the crystal indicates that a spontaneous polarization clearly occurs in the crystallographic a-b plane. 相似文献
58.
Tadashi Endo Naomichi Miyagawa Hirotsugu Takizawa Masahiko Shimada 《Journal of Materials Science》1994,29(9):2395-2400
Multiphase composites of yttria- and ceria-doped tetragonal zirconia agglomerates (10–50 m) dispersed into an alumina or alumina-zirconia matrix were sintered at 1500–1600 °C in air, followed by post-Hot Isostatic Pressing (HIP) at 1450°C and 150 MPa in an Ar gas atmosphere. The relative density of the recovered composites was above 98% of the theoretical density. By chemically etching on the surface of zirconia agglomerates, the sinterability of composites was apparently improved; and no microcracks nor pores were observed at the interface of agglomerate and matrix. According to scanning electron microscopy (SEM) observation, tetragonal and tetragonal-monoclinic zirconia agglomerates were highly dispersed into the alumina or alumina-zirconia matrix. The multiphase composites containing 10 vol% spherical agglomerates demonstrate the relatively low value of bending strength, < 400 MPa, and a high value of fracture toughness, > 11 MPa m1/2. The crack propagation introduced by Vickers indentation was efficiently suppressed and deflected by the agglomerates. 相似文献
59.
Tadashi Kusumoto Osamu Ishikawa Takao Mizusaki Akira Hirai 《Journal of Low Temperature Physics》1985,59(3-4):269-289
The nuclear spin dynamics in nuclear spin ordered solid3He in low magnetic fields on the melting curve has been studied by pulsed NMR down to 0.6 mK. The free induction decay signals (FID) were measured in single crystals of solid3He at three operating frequencies of 920, 1380, and 1840 kHz. The FIDs were nonexponential and dependent on the rf pulse strength
p
H
1
t
w
, where is the gyromagnetic ratio,H
1 is the rf field strength, andt
w
is the pulse width. At small
p
they decayed almost linearly in time with a small exponential tail at the end. When
p
was further increased they became shorter and neither exponential nor linear in time. At large
p
they decayed very rapidly and sometimes could not be observed at all because of the dead time of the NMR detection system. Such behavior of the FID was observed in many different single crystals in the given temperature range at 920 kHz. Tsubota and Tsuneto have shown by solving the nonlinear equations of motion numerically that the motion of the nuclear spin becomes chaotic when the tipping angle exceeds a critical value. Comparing their result with our experimental results, we concluded that some of the results of the rapid decay of the FID at large
p
might be attributed to the onset of the chaotic motion. At 1840 kHz it is expected that the nonlinear effects in the equations of motion become less effective than that at 920 kHz. In fact, at this operating frequency the FIDs even at large
p
and the tipping angle-dependent frequency shift could be observed. These frequency shifts were in rather good agreement with Namaizawa's theory provided an effective tipping angle was taken into account. 相似文献
60.
The effects of applied strain rate on the viscoelastic crack bifurcation phenomenon in Polymethyl Methacrylate (PMMA) were investigated. It was still verified that the product was constant, as was already observed by Congleton and Petch, and Anthony, Chubb and Congleton, for brittle elastic materials, for any strain rate, where σf = the gross fracture stress and Cb= the main crack length until the bifurcation starts. However, it was found that the higher strain rate increases the main crack length Cb resulting in the decrease in the gross fracture stress σf and vice versa. This might be interpreted that the higher stress concentration at the initiation crack tip, which is realized by becoming more brittle due to the higher strain rate owing to the predominance of the elastic element in the viscoelastic material, decreases the gross fracture stress leading to the longer main crack length. 相似文献