全文获取类型
收费全文 | 85400篇 |
免费 | 9355篇 |
国内免费 | 5083篇 |
专业分类
电工技术 | 4669篇 |
技术理论 | 1篇 |
综合类 | 4923篇 |
化学工业 | 22271篇 |
金属工艺 | 7367篇 |
机械仪表 | 7324篇 |
建筑科学 | 1557篇 |
矿业工程 | 1089篇 |
能源动力 | 2603篇 |
轻工业 | 9211篇 |
水利工程 | 473篇 |
石油天然气 | 3483篇 |
武器工业 | 641篇 |
无线电 | 11589篇 |
一般工业技术 | 14049篇 |
冶金工业 | 3482篇 |
原子能技术 | 1779篇 |
自动化技术 | 3327篇 |
出版年
2024年 | 371篇 |
2023年 | 1574篇 |
2022年 | 2232篇 |
2021年 | 2922篇 |
2020年 | 3081篇 |
2019年 | 3112篇 |
2018年 | 2852篇 |
2017年 | 3313篇 |
2016年 | 3392篇 |
2015年 | 3321篇 |
2014年 | 4501篇 |
2013年 | 5408篇 |
2012年 | 5547篇 |
2011年 | 5966篇 |
2010年 | 4219篇 |
2009年 | 4562篇 |
2008年 | 4340篇 |
2007年 | 4978篇 |
2006年 | 4617篇 |
2005年 | 3891篇 |
2004年 | 3246篇 |
2003年 | 3141篇 |
2002年 | 2763篇 |
2001年 | 2330篇 |
2000年 | 2150篇 |
1999年 | 1804篇 |
1998年 | 1569篇 |
1997年 | 1454篇 |
1996年 | 1145篇 |
1995年 | 1057篇 |
1994年 | 852篇 |
1993年 | 692篇 |
1992年 | 652篇 |
1991年 | 502篇 |
1990年 | 451篇 |
1989年 | 402篇 |
1988年 | 285篇 |
1987年 | 183篇 |
1986年 | 161篇 |
1985年 | 187篇 |
1984年 | 179篇 |
1983年 | 123篇 |
1982年 | 111篇 |
1981年 | 52篇 |
1980年 | 46篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1951年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
Tadashi Hano Michiaki Matsumoto Takahisa Kawazu Takaaki Ohtake 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):60-63
The extraction equilibria of various di- and tripeptides with di-2-ethylhexylphosphoric acid (D2EHPA) were studied at low pH values. The complex extracted to organic phase consisted of one molecule of peptide and two molecules of D2EHPA dimer. The extraction constants of the peptides correlated well with the distribution coefficients of peptides between 1-octanol and water, which is a measure of hydrophobicity. The permeation rates of peptides through an emulsion liquid membrane were examined by using D2EHPA as a carrier, Span 80 as an emulsifier and kerosene as a diluent. The rates varied considerably with peptide type, depending upon the hydrophobicity. 相似文献
112.
通过金相、硬度、耐磨性等测试分析表明,在“603”液体渗碳基础上研制出的新型中温低氰液体碳氮共渗剂对薄片件进行薄层碳氮共渗.能完全满足技术要求,并且取得了良好经济和社会效益. 相似文献
113.
本文提出了用一个标样进行系列试样 X 射线定量相分析的方法.它克服了一般 X 射线定量方法需要混合研磨和手续烦复的缺点以及无标样 X 射线定量方法存在病态方程不易解决的问题.该方法对常规 X 射线定量分析具有普遍的实用性. 相似文献
114.
115.
陈小余 《中国计量学院学报》1997,(2)
用相干态的方法得到旋转磁场中自旋为j的粒子的态矢量的严格表达式,由此可计算相干态和叠加相干态的Abaronov-Anandan相位(AA相让).并具有清楚的物理图象. 相似文献
116.
K. Konstantinov N. Balchev G. Gyurov I. Stambolova I. Khristova 《Journal of Superconductivity》1993,6(6):381-386
The superconducting properties and the phase and chemical composition of Bi
x
Pb0.3Sb0.1Sr
y
Ca2Cu3Oz (x=1.5, 1.6, and 1.7;y=1.9, 2.0, and 2.1) materials synthesized by one-step and multistep thermal treatments have been investigated. The multistep annealing between 825–875°C promotes the 2223 phase. The change of Bi concentration has little effect on the 2223 phase formation, regardless of the kind of thermal treatment used, but increasing the Sr concentration (y> 2) strongly inhibits this phase. It has also been established that the loss of Pb after synthesis depends on the initial Bi concentration. The loss of Pb decreases when the initial Bi content is lower. 相似文献
117.
相转移催化合成芳基烷基醚 总被引:7,自引:0,他引:7
报道了以四丁基溴化铵为相转移催化剂,简便地合成了10个芳基烷基醚,反应几乎是定量地快速进行。 相似文献
118.
本法采用同一色谱条件反相高效液相色谱法测定棉铃宝中甲基对硫磷和辛硫磷的含量,方法简单易行,具有较高的精密度和准确度,其回收率分析为甲基对硫磷99.59%,辛硫磷101.0%。 相似文献
119.
The ElectroScan environmental scanning electron microscope (ESEM) enables wet samples to be observed by eliminating air but allowing water vapour into the sample chamber. However, evaporation from, and condensation on, the sample may occur during the pumpdown sequence used to reach this state, which means that the sample may not be in its natural state when viewed if due care is not taken. In this paper, the pumping system of the ESEM is described mathematically and expressions are derived for the evaporation and condensation. This treatment is then used to calculate the optimum pumpdown sequence. The importance of using the optimized procedure is illustrated by micrographs of fat emulsions. 相似文献
120.
The abrasion characteristics of Tencel fabrics were evaluated by Martindale abrasion and laundering, and the breakdown mechanism of fibers was surveyed by scanning electron microscopy. The fabric was subjected to pad‐dry‐cure treatment with two different types of modified dimethyloldihydroxyethylene urea resins (Reaktant DH and Reaktant FC). Although the degree of dry abrasion varied with different resins, the damage exhibited by individual fibers differed little from untreated to resin‐treated; the major mechanism of abrasion was through friction, and the mechanism of fiber failure was multiple splitting and transverse cracking. In untreated Tencel, the characteristic feature of wet abrasion was massive fibrillation, and in crosslinked fabrics, the wet abrasion mechanism was through fiber slippage and slicing action, although in the Reaktant FC‐treated fabric, the wet abrasion mechanism was more through slicing than through fiber splitting. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1391–1398, 2006 相似文献