全文获取类型
收费全文 | 1534篇 |
免费 | 25篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 97篇 |
综合类 | 1篇 |
化学工业 | 199篇 |
金属工艺 | 21篇 |
机械仪表 | 20篇 |
建筑科学 | 15篇 |
能源动力 | 46篇 |
轻工业 | 112篇 |
水利工程 | 2篇 |
无线电 | 216篇 |
一般工业技术 | 237篇 |
冶金工业 | 386篇 |
原子能技术 | 73篇 |
自动化技术 | 139篇 |
出版年
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 21篇 |
2016年 | 27篇 |
2015年 | 17篇 |
2014年 | 24篇 |
2013年 | 57篇 |
2012年 | 38篇 |
2011年 | 53篇 |
2010年 | 31篇 |
2009年 | 48篇 |
2008年 | 60篇 |
2007年 | 57篇 |
2006年 | 48篇 |
2005年 | 41篇 |
2004年 | 45篇 |
2003年 | 47篇 |
2002年 | 37篇 |
2001年 | 54篇 |
2000年 | 27篇 |
1999年 | 51篇 |
1998年 | 176篇 |
1997年 | 89篇 |
1996年 | 66篇 |
1995年 | 48篇 |
1994年 | 36篇 |
1993年 | 31篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 24篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1967年 | 5篇 |
排序方式: 共有1564条查询结果,搜索用时 10 毫秒
131.
Mikihisa Saito Masaru Ishii Atsushi Ohnishi Fumiyuki Fujii Michihiro Matsui Daisuke Natsuno 《Electrical Engineering in Japan》2015,190(1):37-44
In recent years, frequent damage to wind turbines by winter lightning has been reported in the region along the Sea of Japan. It is a serious finding that lightning hits concentrate on wind turbines in this region. The authors investigated the increase rate of the frequency of lightning hits on wind turbines due to wind turbine construction by using LLS (lightning location system) data. As a result, an experimental formula to estimate the increase rate of the frequency of lightning hits on wind turbines as a function of parameters related to the construction conditions, namely the height of wind turbines, the height above sea level, and the latitude, is proposed. 相似文献
132.
Hiroaki Matsumori Toshihisa Shimizu Koushi Takano Hitoshi Ishii 《Electrical Engineering in Japan》2015,190(2):57-71
In recent years, remarkable advancement of new power semiconductor devices, such as SiC and GaN, enables the increase of switching frequency of power converters, and hence the volume of passive components, such as ac filters and transformers, can be reduced. However, temperature rise caused by the inductor loss is increasing, and hence iron loss evaluation of the inductor is one of the most important issues to realize high power density converters. Conventionally, an improved generalized Steinmetz equation (iGSE) has proposed in order to calculate the iron loss under a pulse voltage magnetizing condition. However, accurate iron loss calculation of the ac filter inductor used in a PWM inverter cannot be realized. The authors have proposed two methods of iron loss evaluation of ac filter inductors. The first one is a loss map method which can calculate the iron loss without using a real PWM inverter. Another one is an ILA (Inductor Loss Analyzer) which can measure the iron loss in every switching period in a real PWM inverter. In this paper, comparisons of the iron loss between the ILA and the loss map method on both the single‐phase and three‐phase inverters are studied. It is found that iron loss of the ac filter inductor in the three‐phase PWM inverter which is calculated by the loss map method cause a large error on a specific condition. In order to prevent the calculation error, the authors proposed a revised loss map method and proved the effectiveness of the method. 相似文献
133.
H Muratani K Fukiyama T Kamiyama Y Kimura K Abe M Ishii J Fujii I Kuwajima T Shiomi Y Kawano H Mikami S Ibayashi T Omae 《Canadian Metallurgical Quarterly》1996,19(4):281-290
To assess how elderly Japanese hypertensive patients are treated by specialists, we conducted a cross-sectional survey. A total of 1,163 outpatients aged 50 years or older were studied. Hypertension was diagnosed in 939 of these patients, and 827 were receiving drug therapy. The average blood pressure during therapy was 143 +/- 16/81 +/- 10 mmHg. In patients aged 70 years or older, systolic blood pressure during antihypertensive therapy was significantly higher (p < 0.01) and diastolic blood pressure was significantly lower (p < 0.01) than the corresponding values in those aged 50 to 59 years or 60 to 69 years. The calculated mean blood pressures were similar in the different age groups. The rate of monotherapy in the patients aged 70 years or older was 58.8%, which was significantly higher (p < 0.01) than the rates of monotherapy in the other age groups. Calcium channel blockers were prescribed in about 80% of patients, irrespective of age or comorbidity. Of the patients receiving calcium channel blockers, 43.5% were treated with monotherapy. This rate significantly (p < 0.01) increased with advancing age. Diastolic blood pressures were significantly lower (p < 0.05) in patients with stroke and in those with ischemic heart disease, diabetes mellitus, or dyslipidemia, as compared with patients with no comorbidity. Among patients aged 70 years or older, the difference in systolic blood pressure between those with ischemic heart disease and those with no comorbidity was not significant. Blood pressure in elderly hypertensive patients was reduced to a level similar to that in younger patients. The target blood pressure was influenced by the presence of comorbidity. Furthermore, specialists showed a high preference for the use of calcium channel blockers in the management of hypertension. 相似文献
134.
Ishii K. Nosaka H. Nakajima H. Kurishima K. Ida M. Watanabe N. Yamane Y. Sano E. Enoki T. 《Solid-State Circuits, IEEE Journal of》2002,37(9):1146-1151
Using InP-InGaAs heterojunction bipolar transistor (HBT) technology, we have successfully designed and fabricated a low-power 1:16 demultiplexer (DEMUX) integrated circuit (IC) and one-chip clock and data recovery (CDR) with a 1:4 DEMUX IC for 10-Gb/s optical communications systems. The InP-InGaAs HBTs were fabricated by a nonself-aligned process for high uniformity of device characteristics and producibility. The 1:16 DEMUX IC and the one-chip CDR with the 1:4 DEMUX IC consist of approximately 1200 and 460 transistors, respectively. We have confirmed error-free operation at 10 Gb/s for all data outputs of both ICs. The 1:16 DEMUX IC and the one-chip CDR with the 1:4 DEMUX IC consume only 1 W and 950 mW, respectively. These results demonstrate the feasibility of InP-InGaAs HBTs for low power high-integration optical communication ICs. 相似文献
135.
H Nakata Y Kikuchi T Tode J Hirata T Kita K Ishii K Kudoh I Nagata N Shinomiya 《Canadian Metallurgical Quarterly》1998,89(7):733-740
Ginsenoside Rh2 (Rh2), isolated from an ethanol extract of the processed root of Panax ginseng CA Meyer, inhibits the growth of B16 melanoma cells. This study was designed to evaluate the ability of Rh2 to inhibit growth of human ovarian cancer cells (HRA) in vitro and in nude mouse. Rh2 inhibited proliferations of various established human ovarian cancer cell lines in a dose-dependent manner between 10 and 60 microM in vitro and induced apoptosis at around the IC50 dose. When HRA cells were inoculated s.c. into the right flank of nude mice, all mice formed a palpable tumor within 14 days. Although i.p. administration of Rh2 alone hardly inhibited the tumor growth, when Rh2 was combined with cis-diamminedichloroplatinum(II) (CDDP) the tumor growth was significantly inhibited, compared to treatment with CDDP alone. When mice were treated p.o. with Rh2 daily (but not weekly), the tumor growth was significantly (P<0.01) inhibited, compared to CDDP treatment alone. When Rh2 was combined with CDDP, the degree of tumor growth retardation was not potentiated. The survival time was significantly (P<0.05) longer than that of medium alone-treated controls or the group treated with CDDP alone. Then, we examined whether p.o. administration of Rh2 has a dose-dependent inhibitory effect on the tumor growth. I.p. and weekly administration of CDDP had more potent antitumor activity in the order of 1 mg/kg, 2 mg/kg and 4 mg/kg, whereas p.o. and daily administration of Rh, (0.4 to 1.6 mg/kg) not only had antitumor activity comparable to that of 4 mg/kg CDDP, but also resulted in a significant increase of the survival. Doses of Rh2 used in this study did not result in any adverse side-effects as confirmed by monitoring hematocrit values and body weight, unlike 4 mg/kg CDDP, which had severe side-effects. It is noteworthy that p.o. but not i.p. treatment with Rh2 resulted in induction of apoptotic cells in the tumor in addition to augmentation of the natural killer activity in spleen cells from tumor-hearing nude mice. Thus, particularly in view of the toxicity of CDDP, Rh2 alone would seem to warrant further evaluation for treatment of recurrent or refractory ovarian tumor. 相似文献
136.
K Ishii S Sakamoto M Sasaki H Kitagaki S Yamaji M Hashimoto T Imamura T Shimomura N Hirono E Mori 《Canadian Metallurgical Quarterly》1998,39(11):1875-1878
Frontotemporal dementia (FTD) is a dementia syndrome characterized by peculiar behavioral changes arising from frontotemporal involvement and distinct from Alzheimer's disease (AD). The purpose of this study was to elucidate the specific patterns in cerebral glucose metabolism in patients with FTD and to compare them with the patterns in patients with AD and normal elderly subjects using fluorodeoxyglucose (FDG) and PET. METHODS: Twenty-one patients with a clinical diagnosis of FTD [mean age 67.0 +/- 7.0 yr, Mini Mental State Examination (MMSE) score 18.7 +/- 5.7], 21 age-, sex- and dementia-severity-matched patients with probable AD (mean age 66.9 +/- 7.1 yr, MMSE score 20.2 +/- 5.5) and 21 age- and sex-matched normal control subjects (mean age 66.8 +/- 5.7 yr) were studied. The cerebral metabolic rate for glucose (CMRglc) was measured with FDG and PET. Absolute measures of regional CMRglc were compared among the three groups. One-way ANOVA and the posthoc Tukey HSD test were used for statistical analyses. RESULTS: In the FTD group, CMRglc was preserved only in the left cerebellum, right sensorimotor area and occipital lobes. The CMRglc was significantly lower in the FTD group as opposed to the AD group in the hippocampi, orbital gyri, anterior temporal lobes, anterior cingulate gyri, basal ganglia, thalami, middle and superior frontal gyri and left inferior frontal gyrus. CONCLUSION: Although metabolic abnormality in FTD is predominant in the frontal and anterior temporal lobes and the subcortical structures, it is more widespread than has been previously stressed. These findings document an FTD-specific cerebral involvement and facilitate differential diagnosis of degenerative dementias. 相似文献
137.
Novak Zuber Gary E. Wilson Mamoru Ishii Wolfgang Wulff B. E. Boyack A. E. Dukler P. Griffith J. M. Healzer R. E. Henry J. R. Lehner S. Levy F. J. Moody M. Pilch B. R. Sehgal B. W. Spencer T. G. Theofanous J. Valente 《Nuclear Engineering and Design》1998,186(1-2)
Scaling has been identified as a particularly important element of the Severe Accident Research Program because of its relevance not only to experimentation, but also to analyses based on code calculations or special models. Recognizing the central importance of severe accident scaling issues, the United States Regulatory Commission implemented a Severe Accident Scaling Methodology (SASM) development program involving a lead laboratory contractor and a Technical Program Group to guide the development and to demonstrate its practicality via a challenging application. The Technical Program Group recognized that the Severe Accident Scaling Methodology was an integral part of a larger structure for technical issue resolution and, therefore, found the need to define and document this larger structure, the Integrated Structure for Technical Issue Resolution (ISTIR). The larger part of the efforts have been devoted to the development and demonstration of the Severe Accident Scaling Methodology, which is Component II of the ISTIR. The ISTIR and the SASM have been tested and demonstrated, by their application to a postulated direct containment heating scenario. The ISTIR objectives and process are summarized in this paper, as is its demonstration associated directly with the SASM. The objectives, processes and demonstration for the SASM are also summarized in the paper. The full body of work is referenced. 相似文献
138.
Exposing neonatal rat heart myocytes to the redox cycling quinone naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) for 15 to 45 minutes led to a time-dependent release of cathepsin D from many secondary lysosomes to the cytosol, as analyzed by morphometry. Cathepsin D was detected electron microscopically using a pre-embedding immunostaining technique that utilizes antibodies conjugated to ultra-small (0.8-nm) gold particles and subsequent silver enhancement. The exposure to naphthazarin also caused a decrease in both the pH and the ATP level of the cells within the same time frame. Lipid peroxidation was, however, not detected. Pretreatment of the cultures with alpha-tocopherol succinate prevented cathepsin D relocation, as shown by immunofluorescence. After exposure to naphthazarin, cells were washed, and normal culture conditions were re-established for 18 hours. Many cells then showed apoptotic morphology (ie, cellular shrinkage and chromatin condensation) as analyzed by Giemsa staining. Also, 41% of the cells stained positive with the TUNEL technique, and DNA fragmentation was detected by separation of intact and fragmented DNA. Apoptosis was significantly decreased in cultures pretreated with alpha-tocopherol succinate. 相似文献
139.
A bacterium isolated from a polluted stream, capable of metabolizing biphenyl, naphthalene, phenanthrene, and higher-molecular-weight polycyclic aromatic hydrocarbons (D. Gibson, V. Mahadevan, D. Jerina, H. Yagi, and H. Yeh, Science 189:295-297, 1975), was previously identified as Beijerinckia sp. strain B1. In this investigation, 16S rRNA gene sequencing, biochemical tests, fatty acid methyl ester analysis, polyacrylamide gel electrophoresis of protein, and DNA-DNA hybridization were used to determine the taxonomic relationship of Beijerinckia sp. strain B1. The sequence of the 16S rRNA gene of B1 was identical to that of Sphingomonas yanoikuyae ATCC 51230T. The biochemical tests, fatty acid analysis, and sodium dodecyl sulfate-polacrylamide gel electrophoresis profile of soluble proteins of strain B1 showed results similar to those of S. yanoikuyae. DNA-DNA hybridization indicated that B1 and S. yanoikuyae ATCC 51230T are 75% homologous at the DNA level. We propose that Beijerinckia sp. strain B1 be reclassified as S. yanoikuyae. 相似文献
140.
T Nakagomi H Kanemitsu K Narita H Nakayama T Ishii A Tamura 《Canadian Metallurgical Quarterly》1998,95(6):565-570
The purpose of this randomised single blinded study was to determine the optimal size of laryngeal mask airway in the normal adult population, to test the validity of the current selection criteria and to determine if any externally measured anatomical variable correlated with optimal size. In each of 30 apnoeic anaesthetised adults weighting less than 100 kg, size 3, 4 and 5 laryngeal mask airways were inserted in random order by a skilled user and the cuff inflated to a standard pressure (60 cm H2O). Optimal size was based on four criteria in order of priority: number of attempts at placement, oropharyngeal leak pressure, fiberoptic score and percentage of vocal cords seen. The size 5 laryngeal mask airway was optimal in 19/30 and the size 4 in 11/30. In no patient was the size 3 the optimal fit. Oropharyngeal leak pressure was significantly higher for each progressively large size and the fiberoptic view was significantly better for the size 4 and size 5. There was no significant predictive value in any externally measured anatomical variable, but height was the most useful. The best current selection strategy was to choose a size 5 for males and size 4 for females. Potentially useful new strategies may be to use the size 5 in all adults, or a size 5 > or = 165 cm in height and size 4 for < 165 cm. We conclude that predicting the optimal size of laryngeal mask airway for individual adult patients is complex. The best size selection strategies involve use of the size 4 and 5 laryngeal mask airways in adults. 相似文献