全文获取类型
收费全文 | 2832篇 |
免费 | 246篇 |
国内免费 | 60篇 |
专业分类
电工技术 | 10篇 |
综合类 | 117篇 |
化学工业 | 624篇 |
金属工艺 | 44篇 |
机械仪表 | 130篇 |
建筑科学 | 18篇 |
矿业工程 | 12篇 |
能源动力 | 24篇 |
轻工业 | 1793篇 |
水利工程 | 30篇 |
石油天然气 | 26篇 |
武器工业 | 2篇 |
无线电 | 49篇 |
一般工业技术 | 74篇 |
冶金工业 | 18篇 |
原子能技术 | 6篇 |
自动化技术 | 161篇 |
出版年
2024年 | 16篇 |
2023年 | 33篇 |
2022年 | 122篇 |
2021年 | 164篇 |
2020年 | 96篇 |
2019年 | 110篇 |
2018年 | 69篇 |
2017年 | 99篇 |
2016年 | 99篇 |
2015年 | 98篇 |
2014年 | 142篇 |
2013年 | 210篇 |
2012年 | 201篇 |
2011年 | 229篇 |
2010年 | 128篇 |
2009年 | 123篇 |
2008年 | 112篇 |
2007年 | 184篇 |
2006年 | 180篇 |
2005年 | 114篇 |
2004年 | 90篇 |
2003年 | 76篇 |
2002年 | 61篇 |
2001年 | 55篇 |
2000年 | 41篇 |
1999年 | 44篇 |
1998年 | 37篇 |
1997年 | 25篇 |
1996年 | 24篇 |
1995年 | 18篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有3138条查询结果,搜索用时 15 毫秒
1.
2.
3.
G Garrote J
M Cruz H Domínguez J
C Paraj 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):392-398
Non‐isothermal processing of lignocellulosic materials in aqueous media (autohydrolysis reaction) under mild conditions leads to solutions containing valuable chemicals (oligosaccharides, sugars and acetic acid) and other, undesired, compounds (belonging to the extractive and acid‐soluble lignin fractions) which have to be removed in further purification treatments. Liquors obtained by non‐isothermal autohydrolysis of Eucalyptus globulus wood and corncobs under a variety of operational conditions were extracted with ethyl acetate in order to remove non‐saccharide components, and the suitability of the fraction dissolved in the organic phase was assayed for possible utilisation as an antioxidant. The yield and antioxidant activity of ethyl acetate extracts (measured by the α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) radical scavenging capacity) showed a strong dependence on the autohydrolysis conditions. The antioxidant activity of extracts obtained under selected operational conditions compared well with synthetic antioxidants. © 2003 Society of Chemical Industry 相似文献
4.
将LambdaDNA引入活化的非洲爪蟾卵提取物中,在由磷酸肌酸与磷酸肌酸激酶构成的ATP再生系统的参与下,在这种非细胞体系中能够围绕由LambdaDNA诱导形成的染色质重建核被膜结构,同时在染色质外出现类似核被膜结构的环形片层。在这两种膜结构中核孔复合体的形成都与直径200nm左右的单层圆形小膜泡密切相关,这些小膜泡可以附着在染色质表面或独立于染色质之外相互融合成扁平囊状的双层膜片层,双层膜进一步融合形成核孔,与此同时,核孔复合体在核孔上完成装配。 相似文献
5.
198 6~ 1998年 ,在山东省的 3个灌溉试验站 ,对冬小麦、秋玉米进行了控制灌溉试验 ,对农作物的多个生育阶段 ,按高产的要求 ,分别给予适时、适量的灌溉水 ,来控制作物不同生长期的根层土壤含水量 ,从而控制作物不同生长期根系对水分的吸收 ,培植农作物的“丰产群体结构”和与之相适应的“高产理想株型” ,适当降低无效的蒸腾量 ,使农作物能在高产的基础上再增产 .该项控制灌溉技术获得了明显的节水、增产效果 ,灌溉水的生产效率超过了 10kg/m3,产量超过了 8t/hm2 . 相似文献
6.
L
P Fonseca J
M
S Cabral 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(10):1176-1185
An integrated process strategy for the recovery of penicillin acylase was developed, based on precipitation of non‐enzymatic proteins directly from Escherichia coli homogenates or crude extracts using Rolquat (quaternary ammonium salt) and adsorption of the enzyme on Amp‐Seph (3.8 µmole ampicillin cm?3) under pseudo‐affinity conditions. The effect of pH, concentrations of ammonium sulfate and Rolquat, and also concentrations of protein and cell debris on the precipitation of non‐enzymatic proteins from homogenates and crude extracts of penicillin acylase were analysed. The method of addition of Rolquat to homogenates and crude extracts significantly influenced the size of the precipitated particles. Improved results on the specific activity of penicillin acylase were obtained for 22% and 1% (w/v) of ammonium sulfate and Rolquat, respectively, added sequentially to enzyme solutions and at room temperature. Under these experimental conditions, the specific activity of penicillin acylase in homogenates and crude extracts was enhanced 2.5–3.0‐fold. Finally, the integrated process strategy was implemented first by precipitation of non‐enzymatic proteins and recovery of penicillin acylase directly from the enzyme solution treated with Rolquat using an adsorption/filtration system with an overall yield of 86%. This system allows simultaneously the filtration of cell debris and fine precipitated particles, in situ recovery of penicillin acylase by its adsorption on Amp‐Seph, and selective desorption of the enzyme with a specific activity of 11 IU (mg prot)?1 and a desorption yield of 95%. © 2002 Society of Chemical Industry 相似文献
7.
8.
Myeongjoo Son Seyeon Oh Junwon Choi Ji Tae Jang Kuk Hui Son Kyunghee Byun 《International journal of molecular sciences》2021,22(8)
Hypertension induces renal fibrosis or tubular interstitial fibrosis, which eventually results in end-stage renal disease. Epithelial-to-mesenchymal transition (EMT) is one of the underlying mechanisms of renal fibrosis. Though previous studies showed that Ecklonia cava extracts (ECE) and dieckol (DK) had inhibitory action on angiotensin (Ang) I-converting enzyme, which converts Ang I to Ang II. It is known that Ang II is involved in renal fibrosis; however, it was not evaluated whether ECE or DK attenuated hypertensive nephropathy by decreasing EMT. In this study, the effect of ECE and DK on decreasing Ang II and its down signal pathway of angiotensin type 1 receptor (AT1R)/TGFβ/SMAD, which is related with the EMT and restoring renal function in spontaneously hypertensive rats (SHRs), was investigated. Either ECE or DK significantly decreased the serum level of Ang II in the SHRs. Moreover, the renal expression of AT1R/TGFβ/SMAD was decreased by the administration of either ECE or DK. The mesenchymal cell markers in the kidney of SHRs was significantly decreased by ECE or DK. The fibrotic tissue of the kidney of SHRs was also significantly decreased by ECE or DK. The ratio of urine albumin/creatinine of SHRs was significantly decreased by ECE or DK. Overall, the results of this study indicate that ECE and DK decreased the serum levels of Ang II and expression of AT1R/TGFβ/SMAD, and then decreased the EMT and renal fibrosis in SHRs. Furthermore, the decrease in EMT and renal fibrosis could lead to the restoration of renal function. It seems that ECE or DK could be beneficial for decreasing hypertensive nephropathy by decreasing EMT and renal fibrosis. 相似文献
9.
10.
Larvae and adults of the Colorado potato beetle,Leptinotarsa decemlineata (Say), are shown to have galeal gustatory cells that are highly sensitive to distillate of potato leaf extracts, (E)-2-hexen-1-ol, (E)-2-hexenal, and other saturated and unsaturated six-carbon alcohols. In larvae and adults, the sensory response patterns elicited by leaf homogenate, leaf distillate and a mixture of these two extracts differ in subtle ways. Beetle larvae feed most readily on Millipore disks treated with leaf homogenate and the mixture, but they did not feed on disks treated with leaf distillate. The differences in behavioral response and sensory input are used to derive a potential gustatory code that may stimulate different levels of feeding. This code may be disrupted by compounds present in nonhost leaves, thus leading to reduced feeding. Possible interactions of sapid leaf volatiles, amino acids, sugars, and potentially deterrent plant compounds are discussed. 相似文献