全文获取类型
收费全文 | 263077篇 |
免费 | 3619篇 |
国内免费 | 829篇 |
专业分类
电工技术 | 5179篇 |
综合类 | 332篇 |
化学工业 | 37745篇 |
金属工艺 | 10480篇 |
机械仪表 | 8663篇 |
建筑科学 | 6121篇 |
矿业工程 | 1139篇 |
能源动力 | 6402篇 |
轻工业 | 22899篇 |
水利工程 | 2623篇 |
石油天然气 | 4082篇 |
武器工业 | 68篇 |
无线电 | 35003篇 |
一般工业技术 | 50917篇 |
冶金工业 | 46996篇 |
原子能技术 | 5751篇 |
自动化技术 | 23125篇 |
出版年
2021年 | 2086篇 |
2019年 | 2065篇 |
2018年 | 3547篇 |
2017年 | 3624篇 |
2016年 | 3855篇 |
2015年 | 2367篇 |
2014年 | 4122篇 |
2013年 | 11393篇 |
2012年 | 6672篇 |
2011年 | 9003篇 |
2010年 | 7084篇 |
2009年 | 7976篇 |
2008年 | 8796篇 |
2007年 | 8729篇 |
2006年 | 7886篇 |
2005年 | 7229篇 |
2004年 | 6940篇 |
2003年 | 6803篇 |
2002年 | 6439篇 |
2001年 | 6521篇 |
2000年 | 6228篇 |
1999年 | 6310篇 |
1998年 | 14320篇 |
1997年 | 10336篇 |
1996年 | 8169篇 |
1995年 | 6473篇 |
1994年 | 5748篇 |
1993年 | 5628篇 |
1992年 | 4585篇 |
1991年 | 4257篇 |
1990年 | 4091篇 |
1989年 | 3819篇 |
1988年 | 3654篇 |
1987年 | 3201篇 |
1986年 | 3105篇 |
1985年 | 3634篇 |
1984年 | 3421篇 |
1983年 | 3080篇 |
1982年 | 2891篇 |
1981年 | 2997篇 |
1980年 | 2793篇 |
1979年 | 2690篇 |
1978年 | 2567篇 |
1977年 | 3002篇 |
1976年 | 3629篇 |
1975年 | 2360篇 |
1974年 | 2359篇 |
1973年 | 2358篇 |
1972年 | 1887篇 |
1971年 | 1782篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Mauro D. Santos Ivonne Delgadillo Jorge A. Saraiva 《International Journal of Food Science & Technology》2020,55(3):1171-1179
Hyperbaric storage (HS) was evaluated as a new food preservation methodology at room temperature (RT) for beef and pork meat, both minced and in pieces, and compared to refrigeration (RF) storage. The meat samples were stored at 50, 75 and 100 MPa and variable RT up to 60 days. HS at 75 and 100 MPa could not only inhibit microbial growth but also inactivate microorganisms. Regarding physicochemical analyses, an overall equal to better pH maintenance in HS samples was achieved, and similar colour differences between HS and RF were observed. Generally, similarities in moisture content and drip loss between HS (mostly 75 and 100 MPa) and RF were detected (tendency for lower values in the former and higher values in the latter for the higher pressure level). Protein solubility revealed a decrease of sarcoplasmic protein values during storage with a pressure level dependency in some samples. 相似文献
92.
D. M. Mukhammadiev F. Kh. Ibragimov T. D. Mukhammadiev 《Journal of Machinery Manufacture and Reliability》2020,49(3):256-262
The dynamic characteristics of a saw gin as a subsystem with lumped and distributed parameters are considered in the paper. On the basis of investigation of the machine assembly, graphs are drawn that allow establishing the maximum values of the angle of relative rotation and the angle of rotation of the saw cylinder shaft under torsion. 相似文献
93.
C. G. Prosgolitis S. G. Lambrakos A. D. Zervaki 《Journal of Materials Engineering and Performance》2018,27(10):5102-5113
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size. 相似文献
94.
Buryakov A. M. Khusyainov D. I. Mishina E. D. Khabibullin R. A. Yachmenev A. E. Ponomarev D. S. 《Technical Physics Letters》2018,44(12):1115-1119
Technical Physics Letters - The influence of excitation photons energy on the relaxation times of photoexcited carriers is studied. The involved relaxation mechanisms are evaluated and the... 相似文献
95.
Fominski V. Yu. Nevolin V. N. Fominski D. V. Romanov R. I. Gritskevich M. D. 《Technical Physics Letters》2020,46(1):83-86
Technical Physics Letters - We present the results of a comparative investigation of the friction and wear characteristics of MoSx and MoSex coatings in an oxidizing medium (argon–air... 相似文献
96.
Kovchavtsev A. P. Aksenov M. S. Nastov’yak A. E. Valisheva N. A. Gorshkov D. V. Sidorov G. Yu. Dmitriev D. V. 《Technical Physics Letters》2020,46(5):469-472
Technical Physics Letters - The C–V characteristics of Au/Al2O3/In0.52Al0.48As and Au/SiO2/In0.52Al0.48As metal–insulator–semiconductor structures have been studied. It has been... 相似文献
97.
Detailed study on fusion characteristics of rigid poly(vinyl chloride) nanocomposites: The comparison of using multiple regression analysis and artificial neural network 下载免费PDF全文
Fusion behavior of poly(vinyl chloride) (PVC) compounds plays an important role in the development of physical properties of processed material. The fusion characteristics in PVC processing are governed by material variables that affect the fusion with some interactions. In this research, the aim was to characterize the effects of formulation ingredients on fusion characteristics of PVC. Four material parameters, including the contents of nanoclay (NC), azodicarbonamide, calcium stearate, and processing aid, are proposed as affecting variables. The fusion time (FT) as well as fusion factor (FF) are considered fusion indicators and are experimentally determined in some different levels of affecting parameters. The multivariable regression analysis (MRA) and the Artificial Neural Network (ANN) modeling are considered as two analytical methods. The regression analysis result for the FT denotes, in part, significant linear and quadratic effects of NC and also its significant interactions with azodicarbonamide and calcium stearate, whereas that of FF indicates only a linear effect of NC. ANN modeling is performed with a three‐layer (input, hidden, and output) neural network. The results of the comparison of the MRA and ANN predictions with experimental values are reported as the correlation coefficient (R2), mean‐square error, and mean absolute percentage error for both FF and FT parameters. The obtained values clearly denote that the ANN results are more precise and especially more general than those of MRA. However, in the case of FT, improvement of the ANN modeling is much greater than that of FF. J. VINYL ADDIT. TECHNOL., 21:147–155, 2015. © 2014 Society of Plastics Engineers 相似文献
98.
Jonathan K. Dozier Mark D. Distefano 《International journal of molecular sciences》2015,16(10):25831-25864
The use of proteins as therapeutics has a long history and is becoming ever more common in modern medicine. While the number of protein-based drugs is growing every year, significant problems still remain with their use. Among these problems are rapid degradation and excretion from patients, thus requiring frequent dosing, which in turn increases the chances for an immunological response as well as increasing the cost of therapy. One of the main strategies to alleviate these problems is to link a polyethylene glycol (PEG) group to the protein of interest. This process, called PEGylation, has grown dramatically in recent years resulting in several approved drugs. Installing a single PEG chain at a defined site in a protein is challenging. Recently, there is has been considerable research into various methods for the site-specific PEGylation of proteins. This review seeks to summarize that work and provide background and context for how site-specific PEGylation is performed. After introducing the topic of site-specific PEGylation, recent developments using chemical methods are described. That is followed by a more extensive discussion of bioorthogonal reactions and enzymatic labeling. 相似文献
99.
The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ~4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015. 相似文献
100.