全文获取类型
收费全文 | 3010篇 |
免费 | 103篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 142篇 |
综合类 | 10篇 |
化学工业 | 749篇 |
金属工艺 | 80篇 |
机械仪表 | 100篇 |
建筑科学 | 103篇 |
矿业工程 | 9篇 |
能源动力 | 108篇 |
轻工业 | 232篇 |
水利工程 | 17篇 |
石油天然气 | 15篇 |
无线电 | 261篇 |
一般工业技术 | 571篇 |
冶金工业 | 446篇 |
原子能技术 | 104篇 |
自动化技术 | 185篇 |
出版年
2024年 | 9篇 |
2023年 | 35篇 |
2022年 | 69篇 |
2021年 | 88篇 |
2020年 | 42篇 |
2019年 | 38篇 |
2018年 | 46篇 |
2017年 | 42篇 |
2016年 | 66篇 |
2015年 | 45篇 |
2014年 | 60篇 |
2013年 | 170篇 |
2012年 | 110篇 |
2011年 | 174篇 |
2010年 | 118篇 |
2009年 | 128篇 |
2008年 | 118篇 |
2007年 | 116篇 |
2006年 | 106篇 |
2005年 | 96篇 |
2004年 | 68篇 |
2003年 | 90篇 |
2002年 | 91篇 |
2001年 | 70篇 |
2000年 | 72篇 |
1999年 | 65篇 |
1998年 | 200篇 |
1997年 | 115篇 |
1996年 | 84篇 |
1995年 | 61篇 |
1994年 | 54篇 |
1993年 | 54篇 |
1992年 | 33篇 |
1991年 | 28篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 29篇 |
1985年 | 31篇 |
1984年 | 22篇 |
1983年 | 22篇 |
1982年 | 19篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 36篇 |
1975年 | 8篇 |
排序方式: 共有3132条查询结果,搜索用时 15 毫秒
111.
啤酒酵母吸附重金属离子铬的研究 总被引:4,自引:1,他引:4
将啤酒酵母自制成生物吸附剂,用于吸附重金属离子铬,考察了啤酒酵母吸附Cr^3+过程中的影响因素,即pH值、初始Cr^3+质量浓度、吸附时间、菌体浓度及酸碱预处理方法等因素。结果表 明,啤酒酵母对Cr^3+的吸附量随pH值的增加而增大,吸附的最佳pH值范围是4~7,当pH7时达到吸附最大值;随着初始Cr^3+质量浓度增加,吸附量有所提高,当溶液初始Cr^3+质量浓度为80mg/L吸附效果最佳;最佳吸附时间为1h;菌体的最佳浓度为50mg/L;及啤酒酵母经碱处理后吸附量增大:正交试验确定反应时间为反应过程的显著因素,确定啤酒酵母对Cr^3+的吸附过程遵循Langmuir方程。 相似文献
112.
Takashi Kitaguchi Yasumitsu Ogra Yuji Iwashita Kazuo T. Suzuki 《European Food Research and Technology》2008,227(5):1455-1460
Buckwheat (Fagopyrum esculentum Moench) and quinoa (Chenopodium quinoa Willdenow) are widely used as food ingredients. The nutritional characteristics of these plants, i.e., high contents of proteins
and amino acids suggest that selenium (Se) is preserved as selenoamino acid derivatives, in particular, selenomethionine (SeMet)
in proteins, similar to selenized yeast. Therefore, buckwheat and quinoa are expected to be a good nutritional source of Se.
Selenized buckwheat and quinoa were cultivated on Se-fortified soil using sparingly soluble Se salts, such as barium selenate
and barium selenite. Se concentration in the edible parts of these plants was determined, and Se extraction efficiency with
enzyme or alkali was evaluated. In addition, the chemical species of Se in the low molecular weight fraction of these plants
were determined by HPLC-ICP-MS. Total Se concentrations in the edible parts of selenized buckwheat and quinoa were 170.4 ± 2.9 μg/g
and 102.7 ± 2.4 μg/g wet weight, respectively. Thus, these selenized seeds were found to be Se accumulators. The results indicate
that Se in selenized buckwheat exists mainly as SeMet, while Se in selenized quinoa exists not only as SeMet but also as selenate
(Se(VI)) and non-protein forms. 相似文献
113.
溃疡性结肠炎(UC)是一种特发性肠道疾病,发病率不断上升,且治疗药物都存在不同程度的副作用。研究发现胶原蛋白肽可缓解UC症状,并且安全、健康。然而,目前研究主要局限于UC的预防作用,缺少对其治疗作用的研究。鳗鱼皮富含胶原蛋白,而鳗鱼头一般在加工中被丢弃,造成资源浪费,目前缺少对鳗鱼皮胶原蛋白水解物的研究。本研究尝试利用鳗鱼头中的鱼皮提取胶原蛋白并进行水解,希望得到对UC具有治疗作用的鳗鱼皮胶原蛋白水解物(CH),提高鳗鱼加工副产物的利用价值。研究发现鳗鱼皮所含胶原蛋白丰富,占鱼皮湿重的27.87%,纯度较高且主要为Ⅰ型胶原蛋白,可作为胶原蛋白的优质来源。对胶原蛋白进行酶解,得到具有抗氧化活性的CH,并给药UC模型小鼠,结果显示:与阳性对照和模型组相比,CH可以安全健康地降低UC模型小鼠的DAI评分至0,并改善结肠状态;结肠组织病理切片表明CH可以恢复黏膜上皮完整性,减轻炎性细胞浸润;结肠组织氧化应激指标表明CH可以降低结肠组织MDA含量(0.75 nmol/mg pro)和MPO活性(0.11 U/g tissue),并通过提高GSH含量(22.92 umol/g pro)和SOD(693.61 U/g pro)、CAT(1.69 U/g pro)、GPx(141.29 U/g pro)3种抗氧化酶活性来提高结肠组织抗氧化能力,降低氧化应激水平,从而治疗UC。 相似文献
114.
Feng Ren Shingo Ishida Nobuyuki Takeuchi 《Journal of the American Ceramic Society》1993,76(7):1825-1831
The distribution and chemical states of vanadium in V-doped ZrO2 were studied to clarify the origin of the color of vanadium-zirconium yellow pigment in comparison with vanadium-tin yellow pigment. ESCA data and measurements of lattice constants of V-doped ZrO2 revealed that vanadium was dissolved mainly as V4+ substituting for Zr in ZrO2 lattice, and its solubility limit was 0.5 wt% as V2 O5 . It was found that the yellow color of vanadium-zirconium yellow was produced predominantly by the dissolved vanadium and that the contribution of vanadium oxide on ZrO2 grains to the yellow color was about 1/30 of that of the dissolved vanadium when compared on the basis of equimolar quantity of vanadium. Most of the undissolved vanadium oxide was in an amorphous or a poorly crystallized state. 相似文献
115.
Yuji Sasaki Philippe Rapold Makoto Arisaka Masaru Hirata Takaumi Kimura Clément Hill 《溶剂提取与离子交换》2013,31(2):187-204
Abstract Extraction of Eu(III) and Am(III) from HNO3 into the organic solvents using N,N,N′,N′‐tetraoctyl‐diglycolamide (TODGA) was investigated in order to study the detailed extraction reaction. The chemical species: 1:2 for metal:TODGA complex is present in polar diluents. On the other hand, the metal complexes need three or more TODGA molecules to remain stable in non‐polar diluents. The HNO3 concentration dependence on the distribution ratio suggests that HNO3 participates in the metal extraction. Infrared spectra indicate that the carbonyl oxygen coordinates with Eu(III), and luminescence lifetimes suggest that there are no water molecules in the inner coordination sphere of the extracted Eu‐complex. 相似文献
116.
AbstractA method for low-temperature drying with high drying rate was developed for heat-sensitive foods and agricultural products. A freezing pretreatment was combined with fluidized bed drying under reduced pressure. Cylindrical carrot samples were frozen and then placed without thawing in a fluidized bed of hygroscopic porous silica gel particles that adsorbed water from the sample during the drying process. The effects of the freezing pretreatment and hygroscopicity of fluidizing particles on the drying characteristics of carrots were examined. A higher drying rate was achieved when carrots samples were subjected to freezing pretreatment than without it. At 12?kPa, the volume change was smaller in carrots subjected to freezing pretreatment than in untreated samples. A larger amount of water was absorbed during rehydration by carrots dried at 12?kPa than at 101?kPa within 120?min. The properties of dried carrots were affected not only by freezing pretreatment but also by the pressure applied during the drying process. 相似文献
117.
Infrared study of catalytic reduction of lean NOx with alcohols over alumina-supported silver catalyst 总被引:3,自引:0,他引:3
Two intense IR absorption bands due to surface isocyanate (-NCO) species have been observed at 2262 and 2232 cm–1 when an alumina-supported silver catalyst is exposed to a mixture of NO, O2 and ethanol at 150°C and subsequently heated to > 300°C in vacuum. The intensity of the isocyanate band is hardly affected by the water existing in the mixture. Methanol is less reactive than ethanol for the formation of isocyanate species. The reaction mechanism of catalytic reduction of lean NOx with alcohols is discussed based on these IR spectroscopic findings. 相似文献
118.
用普通小球藻Chlorella vulgaris C9-JN2010处理氨基酸工业废水,实现废水无害化利用。在微型鼓泡式光反应器中,(25±1)℃,pH(6.5±0.5),0.1 vvm空气流速,4 000 lux,16 h:8 h光暗比条件下,分别考察小球藻在体积分数为20%、40%、60%、80%及100%的氨基酸废水中培养生物量变化及TN、TP、COD的去除率。结果表明,体积分数40%氨基酸废水处理效果最好,停留时间3~4 d,藻细胞干重、比生长速率和最大生产强度分别为0.731 g/L、0.565 d-1、0.243 g/(L.d);废水中TN、TP及COD的去除率分别为92.0%、98.0%及80.0%,对应去除强度分别为30.7、3.28、133.3mg/(L.d)。利用小球藻可以较彻底的去除氨基酸废水中氮、磷及COD等营养,达到污水处理效果。 相似文献
119.
Soichiro Ogi Tomohiro Ikeda Masayuki Takeuchi 《Journal of Inorganic and Organometallic Polymers and Materials》2013,23(1):193-199
New rotary molecular machines (1 and 2) were synthetically constructed from two distinct porphyrin-based rotors, a cerium(IV) bis(porphyrinate)s double-decker (CeDD) and a porphyrinatorhodium(III)-based rotor. These rotors are adjacently mounted on rotational axes aligned to near vertical as resembling the bevel-gear-shaped structure. Structural study using NMR analysis reveals that these distinct rotors are connected through a coordination bond between rhodium(III) and a pyridyl group. At temperature from 193 to 393 K, each rotor represents rotational motion driven by heat fluctuation without decomposition into the corresponding precursors in dichloromethane-d 2 and tetrachloroethane-d 4. Importantly, the mechanical interaction between the teeth of these rotors is strongly dependent on the central metal atom in a DD rotor and the teeth structure in a porphyrinatorhodium(III)-based rotor. Understanding such relationship between the chemical structures and mechanical interaction is of importance for generating cooperative motion in the hybrid machinery system. 相似文献
120.
Rina Sakai Yuji Morikawa Chiaki Kondo Hiroyuki Oka Hirofumi Miyajima Kihei Kubo Takeki Uehara 《International journal of molecular sciences》2014,15(10):17256-17269
In vitro mammalian cytogenetic tests detect chromosomal aberrations and are used for testing the genotoxicity of compounds. This study aimed to identify a supportive genomic biomarker could minimize the risk of misjudgments and aid appropriate decision making in genotoxicity testing. Human lymphoblastoid TK6 cells were treated with each of six DNA damage-inducing genotoxins (clastogens) or two genotoxins that do not cause DNA damage. Cells were exposed to each compound for 4 h, and gene expression was comprehensively examined using Affymetrix U133A microarrays. Toxicogenomic analysis revealed characteristic alterations in the expression of genes included in cyclin-dependent kinase inhibitor 1A (CDKN1A/p21)-centered network. The majority of genes included in this network were upregulated on treatment with DNA damage-inducing clastogens. The network, however, also included kinesin family member 20A (KIF20A) downregulated by treatment with all the DNA damage-inducing clastogens. Downregulation of KIF20A expression was successfully confirmed using additional DNA damage-inducing clastogens. Our analysis also demonstrated that nucleic acid constituents falsely downregulated the expression of KIF20A, possibly via p16 activation, independently of the CDKN1A signaling pathway. Our results indicate the potential of KIF20A as a supportive biomarker for clastogenicity judgment and possible mechanisms involved in KIF20A downregulation in DNA damage and non-DNA damage signaling networks. 相似文献