全文获取类型
收费全文 | 2658篇 |
免费 | 67篇 |
国内免费 | 6篇 |
学科分类
工业技术 | 2731篇 |
出版年
2021年 | 29篇 |
2020年 | 12篇 |
2019年 | 20篇 |
2018年 | 25篇 |
2017年 | 33篇 |
2016年 | 43篇 |
2015年 | 40篇 |
2014年 | 63篇 |
2013年 | 111篇 |
2012年 | 88篇 |
2011年 | 117篇 |
2010年 | 84篇 |
2009年 | 99篇 |
2008年 | 110篇 |
2007年 | 110篇 |
2006年 | 96篇 |
2005年 | 87篇 |
2004年 | 86篇 |
2003年 | 79篇 |
2002年 | 85篇 |
2001年 | 63篇 |
2000年 | 53篇 |
1999年 | 77篇 |
1998年 | 149篇 |
1997年 | 121篇 |
1996年 | 64篇 |
1995年 | 64篇 |
1994年 | 49篇 |
1993年 | 48篇 |
1992年 | 32篇 |
1991年 | 30篇 |
1990年 | 28篇 |
1989年 | 32篇 |
1988年 | 39篇 |
1987年 | 41篇 |
1986年 | 40篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 23篇 |
1982年 | 40篇 |
1981年 | 29篇 |
1980年 | 35篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 23篇 |
1976年 | 26篇 |
1974年 | 10篇 |
1967年 | 13篇 |
1966年 | 12篇 |
1965年 | 13篇 |
排序方式: 共有2731条查询结果,搜索用时 15 毫秒
991.
H Kamei N Adati Y Arai K Yamamura M Takayama S Nakazawa Y Ebihara Y Gondo M Akechi T Noguchi N Hirose Y Sakaki T Kojima 《Canadian Metallurgical Quarterly》2003,81(11):724-728
The SHC1 gene encodes a signaling and transforming protein that has been implicated in the aging process in worms and mammals. In this study we examined 230 Japanese centenarians and 180 healthy younger controls and looked at the SHC1 locus as a candidate region that may be associated with longevity. We identified 12 single nucleotide polymorphisms (SNPs) within a 10-kb region encompassing the entire SHC1 gene from the DNA of 30 centenarians and 24 healthy younger controls. Five SNPs, including three nonsynonymous sites, lay within coding elements, six were located within introns, and one was in the 3' untranslated region. All of these SNPs were relatively rare, with a minor allele frequency of less than 5% in our subjects. A pairwise linkage disequilibrium analysis using the r2 statistic showed that two of the SNP pairs are in tight linkage disequilibrium at this locus. We investigated the possible association of SHC1 with longevity using association analyses with allelotypes and haplotypes but found that the SNPs identified in SHC1 had no impact on longevity for Japanese centenarians. 相似文献
992.
993.
The graft copolymerization of methyl methacrylate onto collagen initiated by tributylborane was investigated in aqueous medium. The total conversion, percentage of grafting and efficiency of grafting increased with increasing collagen content. The optimum conditions on the percentage of grafting and efficiency of grafting were determined by varying initiator concentration, monomer concentration, and polymerization temperature. The grafting onto denaturated collagen was also studied. It has been suggested that the grafting onto collagen proceeds by a radical mechanism via a complex of TBB and hydrated collagen. 相似文献
994.
The hydrostatic extrusion of high density polyethylene rod was studied over a wide range of temperatures. The extrudates had smooth surfaces. Those with high extrusion ratios possessed unusual properties being highly transparent and fibrous. The molecular orientation and structural changes due to the hydrostatic extrusion were investigated using wide- and small-angle X-ray diffraction techniques and birefringence. The partial transformation from the orthorhombic to the monoclinic structure occurred in the extrudate obtained at low temperatures (especially at room temperatures). The small-angle X-ray scattering pattern of extrudate for low extrusion ratio showed a diagram with six intensity maxima. On the other hand, for the high extrusion ratio, a diagram with two meridional intensity maxima elongated perpendicular to meridian was observed. At the extrusion ratio R E?6, the chain axes of polyethylene became aligned to the extrusion direction. Small-angle X-ray scattering patterns showed that the new fibre structure began to appear at an extrusion ratio as low as R′E=3.0. The structure of the extrudate at a high extrusion ratio was accounted for by the highly-oriented fibre structure consisting of stacks of folded chain crystallites and the interfibrillar amorphous chain bundles. 相似文献
995.
996.
Anderson James R.; Kuwahata Hiroko; Kuroshima Hika; Leighty Katherine A.; Fujita Kazuo 《Canadian Metallurgical Quarterly》2005,31(1):71
Three experiments assessed whether capuchin monkeys (Cebus apella) and squirrel monkeys (Saimiri sciureus) prefer regular and symmetrical visual patterns. Pictorial representations of faces were included in 1 stimulus set. When the monkeys could pick up and manipulate small cards bearing the stimuli, all preferences expressed by capuchins and most of those expressed by squirrel monkeys were for regular stimuli. Symmetry of the patterns was influential but not essential. Some preferences were also found for faces. When images of the patterns were presented on a touch screen, capuchins continued to express preferences especially for regular and symmetrical stimuli, but they showed some avoidance of faces. Squirrel monkeys responded less discriminatingly to the touch screen stimuli. The findings provide support for B. Rensch's (1957) claim that monkeys prefer visual stimuli that humans find aesthetically pleasing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
In order to evaluate magnetic saturation under subtransient and transient states of a large‐sized salient‐pole synchronous machine, the currents and leakage inductances after sudden three‐phase short circuits are analyzed by a two‐dimensional nonlinear transient finite element method (FEM). The currents are calculated both by direct and indirect methods. The direct method uses the FEM and considers fluctuation of the magnetic saturation after the short circuit. The indirect method solves Park's differential equations without fluctuation. Results of the direct method agree well with measurements. When the preshort voltage is large, fluctuation of the leakage inductances after the short is large and it greatly affects values of the short‐circuit currents. As the preshort voltage becomes large, the damper leakage inductances saturate at first, then the field leakage inductances, and finally the armature leakage inductances saturate. Although the indirect method considers saturation under the preshort condition, it gives inaccurate results and they are nearly the same as the results by the linear FEM. In general, it is thought that saturation of the leakage flux should be considered when subtransient conditions with large disturbance are analyzed. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(4): 46–55, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10240 相似文献
998.
Kuniaki Takagi Tatsumi Inamura Masahiro Kawajiri Kazuo Noya Yoshitugu Hagiwara Yasunobu Suketa 《Water research》2002,36(1):239-247
Deep seawater has recently been under trial as a fundamental material for mineral water, food, face lotion and an efficacious reagent for the cure of atopic dermatitis in Japan. However, little is known about the biologically effective substances, including toxic compounds in deep seawater. In this study, we investigated the effects of deep seawater on the function of murine macrophages in vitro, and examined the endotoxin-like substances in seawater. Mitochondrial activity and NO production in macrophage cells cultured with stimulants were enhanced in a depth dependent manner by pretreatment with deep seawater. In addition, fractions from deep seawater, enriched by hydrophobic column chromatography, activated the macrophage cells much more than the corresponding fractions from surface seawater. Furthermore, the effects of the fractions on macrophage cells remained significant, even with the addition of polymyxin B. which is a specific inhibitor of endotoxins. These results indicate that endotoxins and unknown substances, which affect macrophage functions, exist in a depth dependent manner in seawater. 相似文献
999.
Trihalomethane formation potential of dissolved organic matter in a shallow eutrophic lake 总被引:11,自引:0,他引:11
Dissolved organic matter (DOM) in water samples from the shallow eutrophic Lake Kasumigaura, the second largest lake in Japan, was fractionated and characterized by using resin adsorbents into 5 classes: aquatic humic substances (AHS), hydrophobic neutrals, hydrophilic acids (HiA), bases (BaS) and hydrophilic neutrals (HiN). Subsequently, the trihalomethane formation potential (THMFP), ultraviolet absorbance to dissolved organic carbon (UV:DOC) ratio, and molecular size distribution of the DOM, AHS and hydrophilic fractions (HiF) (HiF=HiA+BaS+HiN) were examined. The THMFP of HiF, normalized on a DOC basis, was found to be comparable to that of AHS (0.176 microM THM mg C(-1) vs. 0.195 microM THM mg C(-1), respectively). The importance of HiF over AHS as a THM precursor became more pronounced when THMFP was evaluated in terms of concentration. In this case, the THMFP of HiF was much greater than that of AHS (0.374 microM THM l(-1) vs. 0.229 microM THM l(-1), respectively). Molecular size distributions all exhibited a narrow size range and relatively low molecular weights. The weight-averaged molecular weights of DOM, AHS and HiF were 780, 957 and 606 g M(-1), respectively. 相似文献
1000.
Takekazu Ishida Masatoshi Nishikawa Yoshifumi Fujita Satoru Okayasu Masaki Katagiri Kazuo Satoh Tsutomu Yotsuya Hisashi Shimakage Shigehito Miki Zhen Wang Masahiko Machida Takuma Kano Masaru Kato 《Journal of Low Temperature Physics》2008,151(3-4):1074-1079
The superconducting neutron detector using high-quality 10B-enriched MgB2 thin films at higher operating temperatures has been proposed, where a resistance change induced by the nuclear reaction
of neutron and 10B in MgB2 is used to detect a neutron. Cold neutrons from a nuclear research reactor irradiated the MgB2 detector, and the output voltage was clearly observed through a low-noise amplifier by using a digital oscilloscope. The
out-of-equilibrium thermodynamics was investigated by means of the time-dependent Ginzburg-Landau equations by using the Earth
Simulator.
相似文献