全文获取类型
收费全文 | 228篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 31篇 |
金属工艺 | 5篇 |
机械仪表 | 6篇 |
建筑科学 | 2篇 |
能源动力 | 2篇 |
轻工业 | 17篇 |
无线电 | 36篇 |
一般工业技术 | 44篇 |
冶金工业 | 46篇 |
原子能技术 | 2篇 |
自动化技术 | 34篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 6篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 12篇 |
2006年 | 3篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 18篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有233条查询结果,搜索用时 31 毫秒
91.
S Noguchi T Shuin Y Kubota S Watanabe Y Nagashima M Masuda M Yao M Hosaka 《Canadian Metallurgical Quarterly》1998,131(2):223-227
Some immortal human cell lines lack telomerase activity. These cell lines were found to contain small dispersed DNA hybridizing to TTAGGG repeats. Such DNA was located in their cytoplasm and nuclei. Normal human fibroblasts or telomerase-positive cell lines did not contain such DNA. Upon cloning and sequencing, it was shown to consist of TTAGGG repeats. When electrophoresed on neutral and alkaline agarose gels, it behaved as double-stranded and linear DNA. These results suggest that telomeric DNA is released from chromosomes in association with maintenance of telomeres in telomerase-negative cell lines. 相似文献
92.
We theoretically derived the rate equation of drug release from a simple model in a heterogeneous system. Four assumptions were used to simplify the model. Two kinds of rate equations for drug release derived from two possible limiting cases, that the rate-determining step is a diffusion or hydrolysis controlled process, can predict the experimental results up to 50% hydrolysis. However, the predictions at the later stage by these equations are insufficient. These results suggest that the process of drug release from powdered polymeric prodrugs in a heterogeneous system must be described by both diffusion and hydrolysis. The rate equation derived from a model considering both the diffusion and hydrolysis processes can successfully predict the experimental results for several kinds of polymeric prodrugs. It is also shown that the diffusion coefficient and rate constant for hydrolysis calculated from this equation thoroughly express the character of the comonomer. The rate equation derived from the model that considers both diffusion and hydrolysis is very useful to analyze drug release from various kinds of polymeric prodrugs in a heterogeneous system. 相似文献
93.
Kikkawa Sho Yamaguchi Takami Tanishita Kazuo Sugawara Motoaki 《IEEE transactions on bio-medical engineering》1987,(5):388-391
It is shown that time-varying velocity produces frequency modulation of the backscattered signal in ultrasonic Doppler flowmeters. Further, for blood flow in the ascending aorta, it is estimated that the spectrum of the backscattered signal would have a very wide bandwidth in the acceleration phase. 相似文献
94.
Y Lin H Miyamoto K Fujinami H Uemura M Hosaka Y Iwasaki Y Kubota 《Canadian Metallurgical Quarterly》1996,2(6):929-932
Telomerase can synthesize telomeric DNA repeats onto chromosome ends. Telomere length and telomerase activity have recently been implicated in the control of the proliferative capacity of normal and malignant cells. The expression of telomerase activity is concomitant with the attainment of immortality in tumor tissues and cells. Thus, enzyme activity may indicate a prevalent or even ubiquitous tumor producer. In this report, telomerase activity was analyzed in 40 human bladder cancers, 7 normal tissues, and 2 bladder epithelia with dysplasia using a PCR-based telomeric repeat amplification protocol assay. Telomerase activity was detected in almost all bladder tumors (97.5%); only one sample, which was in an early stage, did not express telomerase activity. None of the normal tissues displayed telomerase activity. One of the two bladder epithelia with dysplasia expressed low telomerase activity. The expression of telomerase activity has a clear association with the pathological grade and clinical stage. Most of the tumors with high telomerase activity were in an advanced grade and had deep invasion. Thus, telomerase activity might be suggested to represent an additional required event in the multigenetic process of tumorigenesis in human bladder cancer. 相似文献
95.
96.
H Sakagami K Satoh Y Ida M Hosaka H Arakawa M Maeda 《Canadian Metallurgical Quarterly》1998,25(9):1013-1020
The interaction between sodium ascorbate and dopamine was investigated by three different parameters: radical intensity, prooxidant action, and cytotoxicity induction. Sodium ascorbate and dopamine produced the doublet and quartet ESR signals under alkaline conditions (pH 8.0-9.5), respectively. Addition of increasing concentrations of sodium ascorbate completely scavenged the dopamine radical and replaced the latter with its own radical. Similarly, dopamine slightly, but significantly reduced the radical intensity of sodium ascorbate. These two compounds stimulated the methionine oxidation and hydrogen peroxide generation in culture medium, but in combination, their stimulation activities were weakened. Both of these two compounds dose-dependently reduced the viable cell number of human oral squamous carcinoma HSC-4 cells, and their cytotoxic activity was significantly reduced by catalase. When these two compounds were mixed together before adding to HSC-4 cells, both of their cytotoxic activities were diminished. The present study demonstrates the interaction between sodium ascorbate and dopamine, which might modify their biological activities and generation of nerve disorders such as Parkinson's disease. 相似文献
97.
Hiromasa Higasa Fumihiko Ishikawa Motoaki Shibayama Takeshi Ono Shoichi Yokoyama Shirou Nakamura Tadatoshi Yamada Yasuo Yoshida 《Electrical Engineering in Japan》1994,114(7):20-31
When combined with a magnet having a magnetic field gradient (for example, a permanent magnet), a Y-based oxide superconductor is capable of forming a noncontact bearing with a strong levitational force. Since this bearing exhibits low rotational loss, it is very likely to form a highly efficient power storage system in combination with a flywheel. In this paper, an 8-MWh power storage system utilizing a flywheel was designed conceptually to examine its applicability and the possible effects of its introduction. It was found that this system was an effective power storage. 相似文献
98.
A series of polymers with wide ranges of water absorptivity were prepared and utilized as matrices for the controlled release of drugs. The drugs were introduced into the matrices by use of an appropriate organic solvent. Release rates of erythromycin and erythromycin estolate from hydrogel were analyzed kinetically and found to conform to Higuchi's equation, that is, Mt = A(2DtCsC0)1/2, where Mt is the accumulated amount of released drug at time t, A is the surface area, D is the diffusion coefficient, Cs is the solubility of drug in the hydrogel matrix, and Co is the initial drug content of the preparation in the swollen state. The relationship between the water content of hydrogel and the diffusion coefficient of erythromycin in hydrogel is expressed by the equation D = 3.03 × 10?10 W3.03 (cm2/sec), where W is the water content (%). The release rate of drug can be controlled quantitatively by adjustment of the water content of the hydrogel matrix. A guide to the design for the preparation is suggested. 相似文献
99.
Effects of an oxygen flow rate on film formation and nanometre-sized particle generation in the gas phase were examined simultaneously in an atmospheric-pressure chemical vapour deposition reactor using tetraethylorthosilicate (TEOS). The critical temperature for particle generation decreased rapidly to 340C from 740C with increasing oxygen flow rate, but it decreased slightly to 600C from 700C for film formation. There were no conditions where film was deposited without particle generation in a TEOS/O2 system. The nanometre-sized particles generated in the systems were amorphous and non-spherical, and their size distributions were polydisperse. The Fourier transform infrared (FT-IR) and thermal desorption (TDS) spectra of the particles were not affected by oxygen flow rate, and showed that the particles contained a small amount of an ethoxy group and a relatively large amount of a hydroxyl group. It was found from comparisons between FT-IR and TDS spectra of particles and films that the SiO2 films were formed by -elimination reactions, where C2H4 and H2O are released from the ethoxy group. 相似文献
100.
N Hosaka M Nose M Kyogoku N Nagata S Miyashima RA Good S Ikehara 《Canadian Metallurgical Quarterly》1996,93(16):8558-8562
MRL/MP-+/+ (MRL/+) mice develop pancreatitis and sialoadenitis after they reach 7 months of age. Conventional bone marrow transplantation has been found to be ineffective in the treatment of these forms of apparent autoimmune disease. Old MRL/+ mice show a dramatic thymic involution with age. Hematolymphoid reconstitution is incomplete when fetal liver cells (as a source of hemopoietic stem cells) plus fetal bone (FB; which is used to recruit stromal cells) are transplanted from immunologically normal C57BL/6 donor mice to MRL/+ female recipients. Embryonic thymus from allogeneic C57BL/6 donors was therefore engrafted along with either bone marrow or fetal hematopoietic cells (FHCs) plus fragments of adult or fetal bone. More than seventy percent of old MRL/+ mice (> 7 months) that had been given a fetal thymus (FT) transplant plus either bone marrow or FHCs and also bone fragments survived more than 100 days after treatment. The mice that received FHCs, FB, plus FT from allogeneic donors developed normal T cell and B cell functions. Serum amylase levels decreased in these mice whereas they increased in the mice that received FHCs and FB but not FT. The pancreatitis and sialoadenitis already present at the time of transplantations were fully corrected according to histological analysis by transplants of allogeneic FHCs, FB and FT in the MRL/+ mice. These findings are taken as an experimental indication that perhaps stem cell transplants along with FT grafts might represent a useful strategy for treatment of autoimmune diseases in aged humans. 相似文献