全文获取类型
收费全文 | 1824篇 |
免费 | 37篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 83篇 |
综合类 | 1篇 |
化学工业 | 377篇 |
金属工艺 | 47篇 |
机械仪表 | 29篇 |
建筑科学 | 24篇 |
能源动力 | 86篇 |
轻工业 | 173篇 |
水利工程 | 1篇 |
无线电 | 163篇 |
一般工业技术 | 348篇 |
冶金工业 | 384篇 |
原子能技术 | 35篇 |
自动化技术 | 119篇 |
出版年
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 18篇 |
2020年 | 6篇 |
2019年 | 22篇 |
2018年 | 22篇 |
2017年 | 21篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 26篇 |
2013年 | 79篇 |
2012年 | 76篇 |
2011年 | 77篇 |
2010年 | 57篇 |
2009年 | 68篇 |
2008年 | 62篇 |
2007年 | 74篇 |
2006年 | 53篇 |
2005年 | 50篇 |
2004年 | 52篇 |
2003年 | 66篇 |
2002年 | 46篇 |
2001年 | 49篇 |
2000年 | 37篇 |
1999年 | 38篇 |
1998年 | 145篇 |
1997年 | 80篇 |
1996年 | 73篇 |
1995年 | 52篇 |
1994年 | 52篇 |
1993年 | 53篇 |
1992年 | 24篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1974年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有1870条查询结果,搜索用时 15 毫秒
121.
Purification and characterization of a protease from Pseudomonas aeruginosa grown in cutting oil 总被引:2,自引:0,他引:2
The Pseudomonas aeruginosa san-ai strain was isolated from water-soluble cutting oil used for cooling and lubrication during industrial metal-working processes. This strain, which is grown in a high alkaline (pH 10) mixture of surfactants and mineral oil, produces an extracellular proteolytic enzyme. We have purified and characterized this 18 kDa protease. The P. aeruginosa san-ai protease functions optimally at pH 9.0 and 60 degrees C. Additionally, it is a Zn-containing metalloenzyme, and its monomeric structure contains at least one disulfide bond. Because the enzyme is stable in the presence of organic solvents, it is suitable for peptide synthesis. Furthermore, the P. aeruginosa san-ai protease could be used in an intelligent drug delivery system (DDS) designed for applications in the metal industry for prevention of putrefaction of cutting oil. 相似文献
122.
An extracellular exoinulinase from the filamentous fungus Penicillium sp. strain TN-88 has a 14-fold higher specific activity of 743 U/mg toward inulin than its equivalent from the Aspergillus niger strain 12 and possesses an internal 157-amino-acid sequence whose corresponding region is absent in the A. niger enzyme. On the basis of sequence alignment, the internal region D' encoding the 157-amino-acid sequence in the Penicillium exoinulinase gene inuD cDNA was inserted into the site between the nucleotides 897 and 898 of the A. niger exoinulinase gene inuE cDNA. The resultant inuE::D' fusion was expressed in the methylotrophic yeast Pichia pastoris. The K(m) value of the secreted hybrid enzyme InuE::D' for inulin hydrolysis was about 1/15 that of the A. niger InuE, whereas its k(cat) value did not differ greatly from that of the InuE. These observations indicate that the Penicillium exoinulinase has evolved by the horizontal transfer and integration of a relevant DNA segment and that the internal sequence D' functions as an additional noncatalytic inulin-affinity region. 相似文献
123.
Atomic force microscopy (AFM) can dynamically detect the adhesion or affinity force between a sample surface and a cantilever. This feature is useful as a detection method using aptamers--single-strand DNA that recognizes its target with very high affinity. The present study proposes a novel DNA aptamer-based sensing system using AFM. In this study, thrombin was chosen as the target molecule, and a DNA aptamer-based AFM sensing system based on competition was developed. The affinity force between the gold chip and the cantilever decreased as the concentration of thrombin increased. Moreover, a low detection limit of 0.2 nM was achieved. Therefore, the AFM sensing system used would be appropriate for the measurement of various chemical compounds. 相似文献
124.
Shigeki Harada Akihiko Iwata Heiju Uchiike 《Journal of the Society for Information Display》2005,13(6):537-543
Abstract— In order to lower development costs and to shorten development time, small panels, under 10‐in on the diagonal, are used for the experiments to improve the luminous efficiency of plasma‐display panels. However, it is difficult to show the same results as those of large panels, over 40 in. on the diagonal. In this paper, first, we show that the luminous efficiency and the voltage margin of mini‐panels are not obtained with large panels by using an actual 46‐in. PDP. The reason is that the resistance in the large panels is larger than that in the mini panels and the voltage drop in the large panels are larger than in mini‐panels. Therefore, we conclude that the bus electrode width and the transparent electrode width are important factors in the design of large PDPs. Next, we show the technique of designing large panels by using a database obtained from mini‐panels. The estimated cell‐design results show good agreement with an actual 46‐in. PDP in luminous efficiency and minimum sustain voltage. We show that a desired large PDP can be obtained by using the cell design proposed in the present paper. 相似文献
125.
Lipopeptides carrying a farnesyl thioether or a palmitic acid thioester and a farnesyl thioether were prepared from S-farnesyl cysteine methyl ester by N-terminal extension of the peptide chain employing the base labile Fmoc blocking group of the palladium(0) sensitive Aloc urethane. By means of this technique a lipohexapeptide representing the completely functionalized, i.e. palmitoylated and farnesylated C-terminus of the human N-Ras protein, was prepared. If acid labile blocking functions like the Boc group were used, upon deprotection an undesired addition of the acid to the double bonds of the farnesyl residue occurred. Therefore, acid labile blocking groups should not be employed in the synthesis of farnesylated lipopeptides. The lipopeptide methyl esters which carry only a farnesyl group do not inhibit protein farnesyl transferase, whereas palmitoylated peptides are weak inhibitors of this enzyme. 相似文献
126.
Iterative Path Integral Approach to Nonlinear Stochastic Optimal Control Under Compound Poisson Noise 下载免费PDF全文
Nonlinear stochastic optimal control theory has played an important role in many fields. In this theory, uncertainties of dynamics have usually been represented by Brownian motion, which is Gaussian white noise. However, there are many stochastic phenomena whose probability density has a long tail, which suggests the necessity to study the effect of non‐Gaussianity. This paper employs Lévy processes, which cause outliers with a significantly higher probability than Brownian motion, to describe such uncertainties. In general, the optimal control law is obtained by solving the Hamilton–Jacobi–Bellman equation. This paper shows that the path‐integral approach combined with the policy iteration method is efficiently applicable to solve the Hamilton–Jacobi–Bellman equation in the Lévy problem setting. Finally, numerical simulations illustrate the usefulness of this method. 相似文献
127.
Ternary rare-earth sulfides NdGd1+x
S3, where 0 ≤ x ≤ 0.08, were prepared by sulfurizing Ln2O3 (Ln = Nd, Gd) with CS2 gas, followed by reaction sintering. The sintered samples have full density and homogeneous compositions. The Seebeck coefficient,
electrical resistivity, and thermal conductivity were measured over the temperature range of 300 K to 950 K. All the sintered
samples exhibit a negative Seebeck coefficient. The magnitude of the Seebeck coefficient and the electrical resistivity decrease
systematically with increasing Gd content. The thermal conductivity of all the sintered samples is less than 1.9 W K−1 m−1. The highest figure of merit ZT of 0.51 was found in NdGd1.02S3 at 950 K. 相似文献
128.
Yoshiki Hoshide Yusuke Komura Akimori Tabata Akihiko Kitagawa Akihiro Kondo 《Thin solid films》2009,517(12):3520-3523
Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition from SiH4/CH4/H2 and the influence of H2 gas flow rate (F(H2)) on the film properties was investigated. The SiH4 gas flow rate was 1 sccm. At the CH4 gas flow rate (F(CH4)) of 1 sccm, nanocrystalline cubic SiC (nc-3C-SiC) grew even without H2. On the other hand, at F(CH4) = 2 sccm, amorphous SiC grew without H2 and nc-3C-SiC grew above F(H2) = 50 sccm. As F(H2) was increased, the crystallinity improved both at F(CH4) = 1 and 2 sccm. However, the mean crystallite size decreased at F(CH4) = 1 sccm and increased at F(CH4) = 2 sccm. We discuss growth mechanisms of nc-3C-SiC. 相似文献
129.
Hyunjeong Kim Kouji Sakaki Itoko Saita Hirotoshi Enoki Kazuo Noguchi Akihiko Machida Tetsu Watanuki Yumiko Nakamura 《International Journal of Hydrogen Energy》2014
The effect of the vanadium content on the cyclic stability of V–Ti binary alloys was investigated. V1−xTix, x = 0.2 and 0.5 samples were hydrogenated and dehydrogenated at 410 K and 553 K respectively, for more than 100 times. During hydrogen cycling, reduction in the reversible hydrogen storage capacity was clearly observed from both samples. No prominent V-effect was found. In fact, the reduction rates of two samples were similar; both samples showed a ∼25% reduction in the reversible hydrogen storage capacity after 100 cycles. In addition, the shape of the pressure–composition-isotherm (PCT) curves was significantly altered over the testing cycle period; the absorption and desorption plateaus got markedly inclined and the hysteresis became evidently smaller. We found that even after the hydrogen storage capacity of V1−xTix was significantly reduced, at low enough temperature V1−xTix was able to absorb hydrogen as much as it did at the first cycle. Furthermore, the reversible hydrogen storage capacity of V0.8Ti0.2 at 410 K was recovered to a certain degree after hydrogenating the sample at low temperatures. 相似文献
130.
Koichi Hatada Tatsuki Kitayama Kinzo Fujikawa Koji Ohta Heimei Yuki 《Polymer Bulletin》1978,1(2):97-102
Summary Copolymer of methyl methacrylate-d8(M1) with a small amount of trityl methacrylate(M2) was radically prepared in tetrahydrofuran and converted into the copolymer of methyl methacrylate-d8 with a small amount of undeuterated methyl methacrylate by the selective hydrolysis of the trityl group and subsequent methylation with diazomethane. From the 1H NMR spectrum of the derived copolymer the assigned coisotactic parameters 12 and 21 were determined to be 0.14 and 0.61, respectively. This may be the first example of the unequivocal determination of assigned configurational parameters in cross propagation for copolymerization. 相似文献