全文获取类型
收费全文 | 56032篇 |
免费 | 5503篇 |
国内免费 | 1341篇 |
专业分类
电工技术 | 1226篇 |
综合类 | 3403篇 |
化学工业 | 15288篇 |
金属工艺 | 832篇 |
机械仪表 | 1596篇 |
建筑科学 | 3345篇 |
矿业工程 | 319篇 |
能源动力 | 365篇 |
轻工业 | 19793篇 |
水利工程 | 413篇 |
石油天然气 | 464篇 |
武器工业 | 211篇 |
无线电 | 7986篇 |
一般工业技术 | 5336篇 |
冶金工业 | 396篇 |
原子能技术 | 185篇 |
自动化技术 | 1718篇 |
出版年
2024年 | 352篇 |
2023年 | 898篇 |
2022年 | 2159篇 |
2021年 | 2364篇 |
2020年 | 1779篇 |
2019年 | 1702篇 |
2018年 | 1548篇 |
2017年 | 2050篇 |
2016年 | 1892篇 |
2015年 | 2188篇 |
2014年 | 2877篇 |
2013年 | 3233篇 |
2012年 | 3805篇 |
2011年 | 3725篇 |
2010年 | 2935篇 |
2009年 | 2950篇 |
2008年 | 2650篇 |
2007年 | 3627篇 |
2006年 | 3467篇 |
2005年 | 2967篇 |
2004年 | 2417篇 |
2003年 | 1947篇 |
2002年 | 1760篇 |
2001年 | 1389篇 |
2000年 | 1109篇 |
1999年 | 986篇 |
1998年 | 681篇 |
1997年 | 536篇 |
1996年 | 502篇 |
1995年 | 464篇 |
1994年 | 446篇 |
1993年 | 365篇 |
1992年 | 303篇 |
1991年 | 237篇 |
1990年 | 148篇 |
1989年 | 118篇 |
1988年 | 67篇 |
1987年 | 64篇 |
1986年 | 41篇 |
1985年 | 35篇 |
1984年 | 28篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 36篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Robben J.; der Schueren J.Van; Verhasselt P.; Aert R.; Volckaert G. 《Protein engineering, design & selection : PEDS》1995,8(2):159-165
The deletion of nine residues from the C-terminus of the bacterialchloramphenicol acetyltransferase (CAT) results in depositionof the mutant protein in cytoplasmic inclusion bodies and lossof chloramphenicol resistance in Escherichia coli. This foldingdefect is relieved by C-terminal fusion of the polypeptide withas few as two residues. Based on these observations, efficientpositive selection for the cloning of DNA fragments has beendemonstrated. The cloning vector encodes a C-terminally truncatedCAT protein. Restriction sites in front of the stop codon allowthe insertion of target DNA, resulting in the production ofproperly folded CAT fusion proteins and regained chloramphenicolresistance. The positive selection of recombinants is accomplishedby growth of transformants on chloramphenicol-containing agarplates. The method appears particularly convenient for the cloningof DNA fragments amplified by the PCR because minimal informationto restore CAT folding can be included in the primers. The cloningof random sequences shows that the folding defect can be relievedby fusion to a wide variety of peptides, providing great flexibilityto the positive selection system. This vector may also contributeto the determination of the role of the C-terminus in CAT folding. 相似文献
82.
本文报导一种新型的光纤氧、二氧化碳复合传感器.通过在同一敏感膜载体上固定两种不同的荧光试剂——芘丁酸及羟基芘三磺酸,制作了一种对氧和二氧化碳敏感的复合敏感膜.该传感器在医学临床检验范围内具有良好的线性,其测氧的分辩率是0.1%,测二氧化碳的分辩率是0.5%,响应时间短于1min.文中还讨论了三种敏感膜载体的比较及复合传感器测量进程中氧和二氧化碳的相互干扰问题. 相似文献
83.
天然多糖类/蛋白质复合材料的研究进展 总被引:5,自引:0,他引:5
在参考了 31篇文献的基础上 ,详述了天然多糖类与蛋白质复合材料的研究进展 相似文献
84.
ABSTRACT: :
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献
85.
Maribel Plascencia‐Jatomea Miguel A Olvera‐Novoa Jos Luis Arredondo‐Figueroa George M Hall Keiko Shirai 《Journal of the science of food and agriculture》2002,82(7):753-759
This study provides information on the use of shrimp head silage protein hydrolysate (SPH) as an alternative protein source for tilapia feeding. Six diets (28% protein, 12% lipid) were prepared where fishmeal protein was replaced at levels of 0 (control), 10, 15, 20, 25 and 30% with the hydrolysate. The diets were supplied to Nile tilapia fry (338 mg initial weight) stocked in plastic recirculating 20 l tanks (10 animals per tank), with three replicates per treatment. After an 8 week experimental period, fish fed the diets containing 10 and 15% SPH showed significantly better performance in terms of final body weight, weight gain (%), mean daily weight gain (mg day?1), specific growth ratio and feed conversion ratio than those fed the control diet (fishmeal as protein source) and higher‐SPH diets. It is concluded that shrimp head hydrolysate is a promising alternative protein source for tilapia feeding, improving growth ratio at dietary inclusion levels as high as 15%. In addition, the diets with added shrimp silage protein were well accepted by the fish, which avidly consumed the feed during the experiment. © 2002 Society of Chemical Industry 相似文献
86.
腈纶纤维上油率的稳定控制 总被引:1,自引:0,他引:1
从油剂泵、皮辊和钢罗拉等设备构件运行状态考虑,探讨了腈纶纤维上油率的稳定控制问题。 相似文献
87.
88.
89.
介绍一种新型光纤燃煤炉火焰检测器,阐述其系统组成及特点,并提出了基于模糊推理的多信号融合处理方法。 相似文献
90.