全文获取类型
收费全文 | 1281篇 |
免费 | 25篇 |
专业分类
电工技术 | 112篇 |
综合类 | 2篇 |
化学工业 | 184篇 |
金属工艺 | 35篇 |
机械仪表 | 26篇 |
建筑科学 | 28篇 |
能源动力 | 32篇 |
轻工业 | 108篇 |
水利工程 | 1篇 |
石油天然气 | 6篇 |
无线电 | 147篇 |
一般工业技术 | 168篇 |
冶金工业 | 308篇 |
原子能技术 | 24篇 |
自动化技术 | 125篇 |
出版年
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 5篇 |
2019年 | 8篇 |
2018年 | 20篇 |
2017年 | 11篇 |
2016年 | 23篇 |
2015年 | 11篇 |
2014年 | 27篇 |
2013年 | 54篇 |
2012年 | 47篇 |
2011年 | 37篇 |
2010年 | 48篇 |
2009年 | 37篇 |
2008年 | 47篇 |
2007年 | 40篇 |
2006年 | 40篇 |
2005年 | 42篇 |
2004年 | 33篇 |
2003年 | 37篇 |
2002年 | 22篇 |
2001年 | 29篇 |
2000年 | 31篇 |
1999年 | 45篇 |
1998年 | 125篇 |
1997年 | 80篇 |
1996年 | 38篇 |
1995年 | 48篇 |
1994年 | 32篇 |
1993年 | 24篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有1306条查询结果,搜索用时 15 毫秒
961.
Tatsunori Yamagishi Fumio Yamauchi Kazuo Shibasaki 《Journal of the science of food and agriculture》1982,33(11):1092-1100
The precipitate (thermal aggregates) formed in the presence of sulphydryl compounds > 0.01M [β-mercaptoethanol (ME), gutathione (reduced form) (GSH), and cysteine (oxidised form) (Cys)] consisted of a basic monomer subunit and oligomerised sub units but did not contain polymerised subunits. The content of the basic subunits in the precipitate increased with increasing concentrations of sulphydryl compounds, and on addition of 0.5M ME reached a level of 90% or more of the precipitate. The time course of the formation of the basic monomer subunit and oligomerised subunits showed that basic monomer subunits tended to be precipitated at the initial stages of heating. This was followed by the formation of oligomerised subunits. Heating an 11S globulin solution containing sulphydryl compounds accelerated the precipitation reaction. However, this did not produce a high degree of polymerisation due to sulphydryl-disulphide interchange. A scanning electronmicroscope image of thermal aggregation induced in the absence of any sulphydryl compounds showed, however, that polymerisation has a major role in the formation of a network structure. The mechanism of oligomer and polymer formation is discussed here. 相似文献
962.
E Hara S Okamoto S Nakada Y Taya S Sekiya K Oda 《Canadian Metallurgical Quarterly》1993,8(4):1023-1032
The human embryonal carcinoma (EC) cell line NEC14 can be induced to differentiate morphologically by the addition of 10(-2) M N,N'-hexamethylene-bis-acetamide (HMBA). The N-myc gene is expressed at a high level in the undifferentiated cells, but the level decreased steeply after 12-24 h HMBA treatment, returning to its original level after 48 h. The alteration in the N-myc level was well correlated with the formation of complexes with the E2F motif in the N-myc promoter region, and no complex was formed with cell extracts prepared from cells treated with HMBA for 12-24 h. The absence of E2F complexes during this period was caused by an inhibitor generated by a phosphatase reaction. Treatment of the 12-h extract with a cyclic AMP-dependent protein kinase resulted in the formation of E2F complexes, and treatment of the undifferentiated (0 h) and 48-h extracts with a calf intestinal phosphatase abolished complex formation completely. An inhibitor generated by the 0-h extract after treatment with a phosphatase inhibited E2F complex formation by the untreated 0-h extract in the presence of phosphatase inhibitors, okadaic acid and sodium vanadate. One of the two E2F complexes in the undifferentiated cells contained cyclin A, but the complex with similar mobility, formed after the transient decrease in the N-myc level, did not. 相似文献
963.
The 2nd- and 3rd-order nonlinear distortion levels of light-emitting diodes used for analogue optical communication have been measured and found to be typically ?40 and ?75 dB, respectively. A method using three independent signal sources was employed in the measurement. 相似文献
964.
Hara Kazuo; Cornwell P. R.; Warren J. M.; Webster Ikuko H. 《Canadian Metallurgical Quarterly》1974,87(5):884
Reports results of 3 experiments with a total of 59 mongrel and 11 Siamese cats. Extensive ablations of posterior cortex which spared the primary visual areas severely impaired visual pattern discrimination, detour learning, and spatial reversal performance. Lesions in the posterior ecto- and suprasylvian gyri (EP) produced significant deficits in learning multiple object discrimination problems, repeated reversals on spatial or visual cues, and successive visual discriminations. Ss with cortical ablations that did not invade the EP region but did cause damage to the optic radiations were not impaired in reversal learning and were deficient in successive discriminations only when tested with nonsalient cues. Thus, some of the defects shown by EP cats are qualitatively different from the losses in cats with damage to the geniculostriate system. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
965.
Yoshinobu Ohyama Shigehiko Masaki Shin-Ichiro Hara 《Journal of the science of food and agriculture》1975,26(8):1137-1147
In five separate experiments, silages made from Italian ryegrass by eight treatments were transferred into expanded polystyrene containers and the occurrence of deterioration was observed at 25–30 °C and 10–15 °C or 5–10 °C by measuring changes in temperature during 7 days. The treatments were: heavily wilted, slightly wilted, unwilted, and 2% glucose added to unwilted grass—all carried out with and without addition of 0.5% sodium propionate (in one experiment a mixture of 0.08% sodium nitrite and 0.04% hexamethylenetetramine was used instead). Silages tended to be less stable at 25–30 °C than at 10–15 °C ambient temperature, although some were stable even at the higher temperature. At 5–10 °C, no deterioration occurred. No definite relationship was found between occurrence of deterioration and the contents of dry matter or WSC in silage or density in the container. Although deterioration took place more often at pH lower than 4.0, no relationship between pH and deterioration was recognised in the range 4.0–7.0. Silages tended to be more stable when contents of total or lactic acid in fresh matter were high. Silages with no added propionic acid were more susceptible to deterioration but some were unstable even at high propionic acid levels. No aerobic deterioration took place with silages containing more than 0.5% butyric acid. With the deteriorated silages, rises in pH value (except for those with originally high pH), marked decreases in lactic acid and/or WSC were observed. Propionic acid content tended to remain constant in the stable silages but there were a few exceptions. Losses of WSC plus organic acids during deterioration were found to be higher with the silages of high WSC contents. Although changes with the stable silages were generally small, a few of them showed some decrease in WSC and/or organic acids. 相似文献
966.
M Oishi Y Mochizuki M Hara H Uryu S Osaka M Maejima S Sawada T Takasu 《Canadian Metallurgical Quarterly》1995,34(12):1215-1219
The patient, a 61-year-old woman, received a blood transfusion at the age of 33 years. Weakness of the lower extremities developed at the age of 42 and the diagnosis of human T-lymphotropic virus type I (HTLV-I) associated myelopathy was made. Somatosensory evoked potential examination showed that the latency of P27 evoked by peroneal nerve stimulation was 44 msec. Lymphocytapheresis was performed 3 times with one-week intervals using a leukocyte removal filter. The muscle weakness began to improve on the second day after the second lymphocytapheresis and the sensory impairment began to improve on the third day after the third lymphocytapheresis. The delayed latency of P27 improved after the lymphocytapheresis. The effectiveness of lymphocytapheresis in this case suggests that lymphocytes are involved in the pathogenesis of HTLV-I associated myelopathy. 相似文献
967.
Reasoning about keys for XML 总被引:6,自引:0,他引:6
Peter Buneman Susan Davidson Wenfei Fan Carmem Hara Wang-Chiew Tan 《Information Systems》2003,28(8):1037-1063
We study absolute and relative keys for XML, and investigate their associated decision problems. We argue that these keys are important to many forms of hierarchically structured data including XML documents. In contrast to other proposals of keys for XML, we show that these keys are always (finitely) satisfiable, and their (finite) implication problem is finitely axiomatizable. Furthermore, we provide a polynomial time algorithm for determining (finite) implication in the size of keys. Our results also demonstrate, among other things, that the analysis of XML keys is far more intricate than its relational counterpart. 相似文献
968.
The structural requirement has been studied for apolipoproteins in their free form to interact with cells, to generate high
density lipoprotein (HDL), and to cause cellular lipid efflux (J. Biol. Chem. 266, 3080–3086, 1991). It is shown that human apolipoprotein (apo) A-IV and apolipophorin III ofManduca sexta cause cholesterol efflux from cholesterol-loaded mouse peritoneal macrophages and reduce intracellularly accumulated cholesteryl
ester as a results of forming HDL-like particles with cellular lipids, as do apoA-I, A-II and E. On the other hand, similar
to apoC-III, reduced-and-carboxymethylated human apoA-II had no such effect. Thus, apolipoproteins seem to require at least
four amphiphilic helical segments per molecule to express this function. 相似文献
969.
Osamu Ohtaka Takamitsu Yamanaka Shoichi Kume† Naoki Hara Hajime Asano Fujio Izumi 《Journal of the American Ceramic Society》1995,78(1):233-237
The crystal structure of orthorhombic HfO2 synthesized at 600°C and 6 GPa was investigated by a time-of-flight neutron powder diffraction experiment. Rietveld analysis of these data revealed that the space group of this phase is Pbca. The refined lattice parameters are a 0 = 1.00177, b 0 = 0.52276, and c 0 = 0.50599 nm. The structure is derived from a distorted fluorite (CaF2 ) structure by a b -glide parallel to the a -axis. The hafnium atom is in seven-fold coordination. The structure of orthorhombic HfO2 is found to be the same as that of an orthorhombic ZrO2 , which occurs under high pressure above 3 GPa. 相似文献
970.
Matsukawa T. Kishida A. Koh M. Hara K.-I. Horita K. Goto M. Matsuda S. Kuboyama S. Ohdomari I. 《Electron Device Letters, IEEE》1994,15(6):199-201
Soft-error sensitive junctions have been identified in a memory cell of a 63 kbit SRAM. The technique for hitting a micron-size area with a single ion enables us to get a soft-error map in a memory cell. A dependence of the maps on the supply voltage to the memory has been investigated. The errors due to the upset of an n-MOSFET have been observed at higher supply voltage than for a p-MOSFET. This result suggests that the n-MOSFET's are more error-sensitive than the p-MOSFET's for the reason that the n-MOSFET's have a higher efficiency of charge collection and a larger “on” current 相似文献