全文获取类型
收费全文 | 718860篇 |
免费 | 11307篇 |
国内免费 | 2187篇 |
专业分类
电工技术 | 13280篇 |
综合类 | 873篇 |
化学工业 | 108200篇 |
金属工艺 | 27168篇 |
机械仪表 | 20830篇 |
建筑科学 | 17902篇 |
矿业工程 | 3058篇 |
能源动力 | 20099篇 |
轻工业 | 63415篇 |
水利工程 | 6930篇 |
石油天然气 | 11528篇 |
武器工业 | 55篇 |
无线电 | 84293篇 |
一般工业技术 | 140081篇 |
冶金工业 | 139527篇 |
原子能技术 | 13962篇 |
自动化技术 | 61153篇 |
出版年
2022年 | 4300篇 |
2021年 | 6802篇 |
2020年 | 5023篇 |
2019年 | 6193篇 |
2018年 | 10629篇 |
2017年 | 10355篇 |
2016年 | 10955篇 |
2015年 | 7644篇 |
2014年 | 12535篇 |
2013年 | 33715篇 |
2012年 | 19677篇 |
2011年 | 26870篇 |
2010年 | 21355篇 |
2009年 | 23984篇 |
2008年 | 24691篇 |
2007年 | 24231篇 |
2006年 | 21193篇 |
2005年 | 18999篇 |
2004年 | 18275篇 |
2003年 | 18098篇 |
2002年 | 17152篇 |
2001年 | 17436篇 |
2000年 | 16184篇 |
1999年 | 17176篇 |
1998年 | 44244篇 |
1997年 | 30949篇 |
1996年 | 23722篇 |
1995年 | 17822篇 |
1994年 | 15558篇 |
1993年 | 15341篇 |
1992年 | 10990篇 |
1991年 | 10430篇 |
1990年 | 10172篇 |
1989年 | 9747篇 |
1988年 | 9178篇 |
1987年 | 8092篇 |
1986年 | 7939篇 |
1985年 | 8829篇 |
1984年 | 8250篇 |
1983年 | 7480篇 |
1982年 | 6982篇 |
1981年 | 6981篇 |
1980年 | 6716篇 |
1979年 | 6438篇 |
1978年 | 6094篇 |
1977年 | 7449篇 |
1976年 | 10001篇 |
1975年 | 5194篇 |
1974年 | 4945篇 |
1973年 | 5007篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
A. Kathalingam S. Valanarasu Tansir Ahamad Saad M. Alshehri Hyun-Seok Kim 《Ceramics International》2021,47(6):7608-7616
Herein, we report the photosensing property of CdS thin films. CdS thin films were coated onto glass substrates via a spray pyrolysis method using different spray pressures. Prepared films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical and photoluminescence spectroscopy. XRD analysis demonstrated the growth of crystalline CdS films with crystallite sizes varying from 26 to 29 nm depending on the pressure. The SEM and EDAX analyses revealed nearly-stoichiometric CdS films with smooth surfaces and slight variation in grain morphology due to pressure changes. Optical measurements showed a direct bandgap varying from 2.37 eV to 2.42 eV due to pressure changes. A photodetector was also fabricated using the grown CdS films; the fabricated photodetector exhibited good performance depending on the spray pressure. A spray pressure of 1.5 GPa resulted in high photoresponsivity and external quantum efficiency. 相似文献
72.
73.
Golubev N. V. Ignat’eva E. S. Maurus A. A. Ziyatdinova M. Z. Lopatina E. V. Lorenzi R. Paleari A. Sigaev V. N. 《Glass and Ceramics》2021,77(11-12):415-418
Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence... 相似文献
74.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
75.
Catalysis Letters - A new zirconium based carbonaceous solid acid catalyst Zr@CC-PA with both Lewis and Bronsted acidic sites was prepared by simultaneous carbonization and phosphonation of glucose... 相似文献
76.
World Wide Web - Rule mechanism has been widely used in many areas, such as databases, artificial intelligent and pervasive computing. In a rule mechanism, rule activation decides which rules are... 相似文献
77.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations. 相似文献
78.
Salim Hengky K. Padfield Rory Lee Chew Tin Syayuti Khadijah Papargyropoulou Effie Tham Mun Hou 《Clean Technologies and Environmental Policy》2018,20(3):529-538
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food... 相似文献
79.
Christoph Gottschalk Aiko Huckauf Arne Dübecke Florian Kaltner Matthias Zimmermann Ines Rahaus 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(7):1366-1383
The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment. 相似文献
80.