全文获取类型
收费全文 | 7643篇 |
免费 | 166篇 |
国内免费 | 27篇 |
学科分类
工业技术 | 7836篇 |
出版年
2023年 | 33篇 |
2022年 | 23篇 |
2021年 | 139篇 |
2020年 | 68篇 |
2019年 | 79篇 |
2018年 | 100篇 |
2017年 | 79篇 |
2016年 | 141篇 |
2015年 | 99篇 |
2014年 | 196篇 |
2013年 | 418篇 |
2012年 | 249篇 |
2011年 | 383篇 |
2010年 | 308篇 |
2009年 | 354篇 |
2008年 | 405篇 |
2007年 | 358篇 |
2006年 | 269篇 |
2005年 | 291篇 |
2004年 | 225篇 |
2003年 | 219篇 |
2002年 | 236篇 |
2001年 | 151篇 |
2000年 | 142篇 |
1999年 | 179篇 |
1998年 | 386篇 |
1997年 | 272篇 |
1996年 | 172篇 |
1995年 | 150篇 |
1994年 | 156篇 |
1993年 | 137篇 |
1992年 | 84篇 |
1991年 | 118篇 |
1990年 | 86篇 |
1989年 | 107篇 |
1988年 | 89篇 |
1987年 | 63篇 |
1986年 | 90篇 |
1985年 | 85篇 |
1984年 | 75篇 |
1983年 | 72篇 |
1982年 | 79篇 |
1981年 | 64篇 |
1980年 | 61篇 |
1979年 | 62篇 |
1978年 | 56篇 |
1977年 | 55篇 |
1976年 | 56篇 |
1975年 | 24篇 |
1973年 | 25篇 |
排序方式: 共有7836条查询结果,搜索用时 114 毫秒
1.
Shouko Nishida Masaya Shibano Hiroshi Kamitakahara Toshiyuki Takano 《International journal of molecular sciences》2015,16(12):29093-29102
We recently observed that the decanoylation of N-phenylthiocarbamoyl chitosan (2) with a mixture of decanoic anhydride and pyridine at 60 °C for 24 h afforded N,N-(decanoyl)phenythiocarbamoyl-/2-isothiocynato chitosan decanoate (3b) rather than the expected product N,N-(decanoyl)phenylthiocarbamoyl chitosan decanoate (3a). This result suggested that some of the N,N-(decanoyl)phenylthiocarmbamoyl groups had been converted to isothiocyanate groups during the decanoylation process. The subsequent reaction of compound 3b with aniline gave N,N-(decanoyl)phenylthiocarbamoyl/N-phenylthiocarbamoyl chitosan decanoate (4) in high yield. A solution of compound 4 in CHCl3 was then added to a solution of copper decanoate (5) in the same solvent, and the resulting mixture was cast onto a glass plate to give a cast film. The film was annealed at 200 °C in an oven to give a greenish film, which showed good near-infrared absorption characteristic in the range of 800–2200 nm. 相似文献
2.
3.
Liu Yong-Fang Matsumoto Hiroshi Gu Ming Zhou Xiao-Xuan Wu Yong-Hua Chen Zhi-Hao 《核技术(英文版)》2019,30(7):1-6
Longitudinal injection is a promising on-axis injection scheme for diffraction-limited storage rings. In the latest version of the Hefei advanced light source(HALS), both the dynamic aperture and momentum aperture have been optimized. A longitudinal injection scheme was investigated on the HALS using a doublefrequency radio frequency system. To evaluate the injection performance, various errors were considered. A series of tracking simulations were conducted, and the injection efficiency was obtained under different error levels. 相似文献
4.
A Synthetic Transcriptional Activator of Genes Associated with the Retina in Human Dermal Fibroblasts 下载免费PDF全文
5.
Adele Boccuto Filippo Dragoni Francesca Picarazzi Alessia Lai Carla Della Ventura Carla Veo Federica Giammarino Francesco Saladini Gianguglielmo Zehender Maurizio Zazzi Mattia Mori Ilaria Vicenti 《International journal of molecular sciences》2021,22(5)
The nucleotide analog sofosbuvir, licensed for the treatment of hepatitis C, recently revealed activity against the Zika virus (ZIKV) in vitro and in animal models. However, the ZIKV genetic barrier to sofosbuvir has not yet been characterized. In this study, in vitro selection experiments were performed in infected human hepatoma cell lines. Increasing drug pressure significantly delayed viral breakthrough (p = 0.029). A double mutant in the NS5 gene (V360L/V607I) emerged in 3 independent experiments at 40–80 µM sofosbuvir resulting in a 3.9 ± 0.9-fold half- maximal inhibitory concentration (IC50) shift with respect to the wild type (WT) virus. A triple mutant (C269Y/V360L/V607I), detected in one experiment at 80 µM, conferred a 6.8-fold IC50 shift with respect to the WT. Molecular dynamics simulations confirmed that the double mutant V360L/V607I impacts the binding mode of sofosbuvir, supporting its role in sofosbuvir resistance. Due to the distance from the catalytic site and to the lack of reliable structural data, the contribution of C269Y was not investigated in silico. By a combination of sequence analysis, phenotypic susceptibility testing, and molecular modeling, we characterized a double ZIKV NS5 mutant with decreased sofosbuvir susceptibility. These data add important information to the profile of sofosbuvir as a possible lead for anti-ZIKV drug development. 相似文献
6.
Eicosapentaenoic acid (EPA) production by an oleaginous fungus Mortierella alpina expressing heterologous the Δ17‐desaturase gene under ordinary temperature 下载免费PDF全文
7.
Dr. Yan Shan Ang Dr. Toshikazu Bando Prof. Hiroshi Sugiyama Dr. Lin-Yue Lanry Yung 《Chembiochem : a European journal of chemical biology》2020,21(20):2912-2915
We used N-methylpyrrole (Py)-N-methylimidazole-(Im) polyamide as an exogenous agent to modulate the formation of DNA assemblies at specific double-stranded sequences. The concept was demonstrated on the hybridization chain reaction that forms linear DNA. Through a series of melting curve analyses, we demonstrated that the binding of Py−Im polyamide positively influenced both the HCR initiation and elongation steps. In particular, Py−Im polyamide was found to drastically stabilize the DNA duplex such that its thermal stability approached that of an equivalent hairpin structure. Also, the polyamide served as an anchor between hairpin pairs in the HCR assembly, thus improving the originally weak interstrand stability. We hope that these proof-of-concept results can inspire future use of Py−Im polyamide as a molecular tool to modulate the formation of DNA assemblies. 相似文献
8.
Koizumi H. Kurokawa K. Mori S. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(3):677-687
This paper presents an analysis of Class D inverter when irregular driving patterns are given to the gate drive of the switch devices. The analysis has been carried out with focusing on the waveforms, harmonics, low-frequency components, output power, and equivalent dc resistance, which are numerically analyzed and discussed. Class D inverters with six different Q factors from 0.1 to 20 are analyzed about 2/sup 16/ driving patterns for each Q. Superior four models of the six inverters are built and tested in circuit experiments. The calculated waveforms are compared to the experimental results. Both of them are agreed well in time domain and frequency domain. Analytical results show a possibility of a novel control method with irregular driving patterns. In spite of discontinuous control, the output power or voltage can be strictly changed as if continuous using the selected driving patterns in some ranges. 相似文献
9.
Hiroshi Takamatsu Hikaru Yamashiro Nobuo Takata Hiroshi Honda 《International Journal of Refrigeration》2003,26(6):79
Heat and mass transfer in a falling film vertical in-tube absorber was studied experimentally with LiBr aqueous solution. The presented results include the effect of solution flow rate, solution subcooling and cooling water temperature on the absorption in a smooth copper tube 16.05 mm I.D. and 400 mm long. The experimental data in the previous report for a 1200-mm-long tube was also re-examined and compared. It was demonstrated by the observation of the flow in the tube that the break down of the liquid film into rivulets leads to deterioration of heat and mass transfer at lower film Reynolds number or in longer tubes. An attempt to evaluate physically acceptable heat and mass transfer coefficients that are defined with estimated temperature and concentration at the vapor–liquid interface was also presented. 相似文献
10.
Takauchi H. Tamura H. Matsubara S. Kibune M. Doi Y. Chiba T. Anbutsu H. Yamaguchi H. Mori T. Takatsu M. Gotoh K. Sakai T. Yamamura T. 《Solid-State Circuits, IEEE Journal of》2003,38(12):2094-2100
We describe a CMOS multichannel transceiver that transmits and receives 10 Gb/s per channel over balanced copper media. The transceiver consists of two identical 10-Gb/s modules. Each module operates off a single 1.2-V supply and has a single 5-GHz phase-locked loop to supply a reference clock to two transmitter (Tx) channels and two receiver (Rx) channels. To track the input-signal phase, the Rx channel has a clock recovery unit (CRU), which uses a phase-interpolator-based timing generator and digital loop filter. The CRU can adjust the recovered clock phase with a resolution of 1.56 ps. Two sets of two-channel transceiver units were fabricated in 0.11-/spl mu/m CMOS on a single test chip. The transceiver unit size was 1.6 mm /spl times/ 2.6 mm. The Rx sensitivity was 120-mVp-p differential with a 70-ps phase margin for a common-mode voltage ranging from 0.6 to 1.0 V. The evaluated jitter tolerance curve met the OC-192 specification. 相似文献