全文获取类型
收费全文 | 235295篇 |
免费 | 4624篇 |
国内免费 | 1622篇 |
专业分类
电工技术 | 4965篇 |
技术理论 | 2篇 |
综合类 | 1838篇 |
化学工业 | 36739篇 |
金属工艺 | 12061篇 |
机械仪表 | 8987篇 |
建筑科学 | 6316篇 |
矿业工程 | 3147篇 |
能源动力 | 5414篇 |
轻工业 | 14577篇 |
水利工程 | 3436篇 |
石油天然气 | 9743篇 |
武器工业 | 235篇 |
无线电 | 24619篇 |
一般工业技术 | 48772篇 |
冶金工业 | 35919篇 |
原子能技术 | 6969篇 |
自动化技术 | 17802篇 |
出版年
2022年 | 2039篇 |
2021年 | 3258篇 |
2020年 | 2543篇 |
2019年 | 2744篇 |
2018年 | 4612篇 |
2017年 | 4653篇 |
2016年 | 4895篇 |
2015年 | 3353篇 |
2014年 | 5199篇 |
2013年 | 10488篇 |
2012年 | 7540篇 |
2011年 | 9104篇 |
2010年 | 7558篇 |
2009年 | 8156篇 |
2008年 | 8166篇 |
2007年 | 8022篇 |
2006年 | 7212篇 |
2005年 | 6471篇 |
2004年 | 5495篇 |
2003年 | 5382篇 |
2002年 | 5107篇 |
2001年 | 5092篇 |
2000年 | 4847篇 |
1999年 | 4994篇 |
1998年 | 10857篇 |
1997年 | 7790篇 |
1996年 | 6046篇 |
1995年 | 4585篇 |
1994年 | 3943篇 |
1993年 | 4096篇 |
1992年 | 3177篇 |
1991年 | 3147篇 |
1990年 | 3002篇 |
1989年 | 2948篇 |
1988年 | 2941篇 |
1987年 | 2556篇 |
1986年 | 2616篇 |
1985年 | 2876篇 |
1984年 | 2705篇 |
1983年 | 2568篇 |
1982年 | 2316篇 |
1981年 | 2278篇 |
1980年 | 2352篇 |
1979年 | 2360篇 |
1978年 | 2382篇 |
1977年 | 2487篇 |
1976年 | 2876篇 |
1975年 | 2188篇 |
1974年 | 2068篇 |
1973年 | 2166篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
101.
Abdou Safaa N. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):3962-3975
Journal of Inorganic and Organometallic Polymers and Materials - The reaction of potassium tetracyanocupprate(I) with triethyltin bromide in presence of phenanthroline (Phen) and quinoxaline (Qox)... 相似文献
102.
Byakova O. V. Stepanov G. V. Vlasov A. O. Danylyuk V. E. Semenov N. V. Berezovs’kyi O. M. Gnyloskurenko S. V. 《Strength of Materials》2019,51(5):726-734
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to... 相似文献
103.
Weigang Liang Beibei Wang Guofeng Shen Suzhen Cao Bertrand Mcswain Ning Qin Liyun Zhao Dongmei Yu Jicheng Gong Shanshan Zhao Yawei Zhang Xiaoli Duan 《Indoor air》2020,30(2):264-274
Stunting adversely affects physical and mental outcomes of children. It has not been examined whether household air pollution from solid fuel combustion is a risk factor for stunting in children. In a total of 41,439 children aged 6-17 across China, height was measured using a unified protocol. Multivariable linear regression models and logistic regression models were used to assess the associations of solid fuel use for cooking/heating with stunting in children. Adjusted for covariates, cooking/heating with solid fuel was significantly associated with a lower z-score for height for age and sex (β = −0.21 [−0.32 to −0.09] and −0.17 [−0.31 to −0.03], respectively) and an increased risk of stunting with an estimated ORs of 1.34 [1.07~1.68] and 1.37 [1.02~1.83], respectively. The risk of stunting associated with solid fuel use was statistically significant in high-age children. And the effect was greater on girls than on boys, though the difference was not statistically significant. Our study suggested that Chinese children living in households using solid fuel had a significantly higher risk of stunting than those living in households using cleaner fuel. 相似文献
104.
105.
E. G. Kulapina N. M. Makarova O. I. Kulapina I. A. Utc V. V. Baraguzina 《Petroleum Chemistry》2015,55(10):892-900
Potentiometric sensors with plasticized poly(vinyl chloride) membranes based on β-lactam–tetraalkylammonium ion associates sensitive to penicillin antibiotics are proposed. The physicochemical characteristics (solubility product constants and dissociation constants) of active membrane components and the electrode, transport, and selective properties of the membranes of liquidand solid-contact sensors have been studied. The quantitative characteristics of membrane transport (penetrability, ion flux, and transport rate) have been evaluated. The main charge carriers in the membranes and at the membrane/solution interface have been determined from the membrane transport characteristics. The potentiometric sensors are shown to be applicable to the determination of penicillin antibiotics in biological fluids (blood serum and oral fluid) from patients with urinary tract infection. 相似文献
106.
107.
V. N. Oparin V. I. Vostrikov O. M. Usol’tseva P. A. Tsoi V. N. Semenov 《Journal of Mining Science》2015,51(3):624-633
The authors have developed a procedure and a test bench for studying evolution of various nature physical fields in modeling geomedium fracture by fluids. The test bench performs synchronous recording of macro- and micro-deformation, heat and acoustic emission induced in physical models of geomedium under loading to discontinuity. The experimental procedure has been trialed. The analysis of the synchronized test data allows a conclusion on the existence of time–space relationship between different nature physical fields induced during failure of solids. 相似文献
108.
109.
A Synthetic Transcriptional Activator of Genes Associated with the Retina in Human Dermal Fibroblasts
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
110.
P.Y. Raval P.R. Pansara A.R. Makadiya N.H. Vasoya S.N. Dolia K.B. Modi 《Ceramics International》2018,44(15):17667-17674
The consequences of high energy mechanical milling, microwave-assisted heating and rapid thermal cooling on magnetic ordering in polycrystalline CaCu3Ti4O12 cubic perovskite have been investigated by means of X-ray powder diffractometry (300?K), dc magnetization in field – cooled and zero – field cooled modes (H = 100?Oe and 1000?Oe, T?=?5–300?K) (M – T curves) and M – H loop characteristics (T?=?5?K and 300?K, Hmax = 70?kOe). The M – T curves of unmilled and 16?h milled samples show pure antiferromagnetic and weak ferromagnetic ordering, respectively, 1?h and 6?h milled samples demonstrate the coexistence of both the phases while microwave-assisted and quenched samples exhibit classic antiferromagnetic transition and a low temperature paramagnetic–like contribution with different weights, well supported by the M – H loop characteristics. The observed transformations in the magnetic ordering are attributed to the ball-milling induced stress which curtails hybridization of empty Ti-3d orbitals with Cu-3d and O-2p orbitals and secondary phase formation. Oxygen vacancies associated with bound magnetic polarons originate ferromagnetism in the milled samples while unpaired electrons inhabited at the empty sites are the cause of paramagnetic centers. The low-temperature Curie – tail in M – T curve for quenched and microwave assisted samples is attributed to Ti3+ cations. 相似文献