全文获取类型
收费全文 | 88229篇 |
免费 | 7619篇 |
国内免费 | 3900篇 |
专业分类
电工技术 | 5011篇 |
技术理论 | 11篇 |
综合类 | 5661篇 |
化学工业 | 14959篇 |
金属工艺 | 4837篇 |
机械仪表 | 5586篇 |
建筑科学 | 6609篇 |
矿业工程 | 2818篇 |
能源动力 | 2514篇 |
轻工业 | 5304篇 |
水利工程 | 1544篇 |
石油天然气 | 6273篇 |
武器工业 | 818篇 |
无线电 | 10111篇 |
一般工业技术 | 10470篇 |
冶金工业 | 4239篇 |
原子能技术 | 882篇 |
自动化技术 | 12101篇 |
出版年
2024年 | 474篇 |
2023年 | 1683篇 |
2022年 | 2946篇 |
2021年 | 3994篇 |
2020年 | 3036篇 |
2019年 | 2425篇 |
2018年 | 2800篇 |
2017年 | 3021篇 |
2016年 | 2595篇 |
2015年 | 3555篇 |
2014年 | 4462篇 |
2013年 | 5236篇 |
2012年 | 5596篇 |
2011年 | 6171篇 |
2010年 | 5332篇 |
2009年 | 4808篇 |
2008年 | 5030篇 |
2007年 | 4561篇 |
2006年 | 4568篇 |
2005年 | 3995篇 |
2004年 | 2552篇 |
2003年 | 2274篇 |
2002年 | 2136篇 |
2001年 | 1888篇 |
2000年 | 1987篇 |
1999年 | 2369篇 |
1998年 | 1863篇 |
1997年 | 1529篇 |
1996年 | 1402篇 |
1995年 | 1227篇 |
1994年 | 1014篇 |
1993年 | 723篇 |
1992年 | 594篇 |
1991年 | 432篇 |
1990年 | 345篇 |
1989年 | 251篇 |
1988年 | 221篇 |
1987年 | 139篇 |
1986年 | 110篇 |
1985年 | 72篇 |
1984年 | 59篇 |
1983年 | 59篇 |
1982年 | 46篇 |
1981年 | 37篇 |
1980年 | 33篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Follicular dendritic cell tumour of the liver is a recently recognized entity. To date, only two cases have been described, both in the pathology literature. Histologically, it resembles an inflammatory pseudotumour and immunohistochemical and ultrastructural studies are required for its diagnosis. The ultrasound, computed tomography and angiographic features of two cases of follicular dendritic cell tumour of the liver are described in detail. One of the patients had multiple recurrences of this tumour. The imaging features are very similar to those of hepatocellular carcinoma. As follicular dendritic cell tumour is considered to be of low-grade malignant potential, in contrast to the dismal prognosis for hepatocellular carcinoma, it is important to be able to accurately distinguish between the two types of tumour prior to initiating definitive therapy. 相似文献
102.
A new minimum zone method for evaluating flatness errors 总被引:1,自引:0,他引:1
A new minimum zone method for flatnes error analyis is proposed in this article. Based on the criteria for the minimum zone solution and strict rules for data exchange, a simple and rapid algorithm, called the control plane rotation scheme, is developed for the flatness analysis of a flat surface. Experimental work was performed, and some examples are given in terms of the minimum zone and least-squares solutions. 相似文献
103.
小秦岭地区金矿床严格受构造控制,各成矿阶段及矿物学特征明显,通过对矿物学特征的研究找出矿物学标志,认为今后找矿要注意各阶段石英的颜色、黄铁矿中金的含量以及矿石中银的含量,这些与金有密切关系. 相似文献
104.
结合当前我国建材市场的形势 ,就建材市场“涨价风潮”的起因 ,从经济增长的结果、市场运行的规律等方面进行了论述 ,提出了涨价风潮对近期全国建材市场的影响 相似文献
105.
粘土作为高放废物处置回填材料的可行性研究 总被引:5,自引:0,他引:5
本文以西北粘土为对象,对其压实行为、热传导、膨胀特性,以及吸附和渗透性能进行了初步研究,借以探讨西北粘土在高放废物处置中用作回填材料的可行性。试验表明,以西北粘土为基材,经过适当的热改性和吸附改性,在初始含水量约为9%,于70MPa 下成型,用作高放废物处置中的回填材料是可行的。 相似文献
106.
本文重点讨论了硫氰酸钠湿纺腈纶设备因钝化膜缺陷和Cl-侵入而产生孔蚀的机理及环境因素对孔蚀的影响,并针对产生孔蚀的主要原因提出了防护措施。 相似文献
107.
Li Xi Zuoyan Peng Wei Fan Kui Guo Gu Jianmin Muyu Zhao Wu Guoqiang 《Materials Science and Engineering: B》1996,40(2-3):147-152
SrMgxTi1 - xO3 nanocrystals (x = 0.1–0.6) were synthesized by the stearic acid gel method. Powder samples were characterized by X-ray diffraction and X-ray photoelectron (XP) spectroscopy. The results showed that the lattice parameter a and the O 1s XP spectrum changed not only with the Mg content x but also with the grain size d of the samples. The conductivity of a thick film specimen fabricated on an aluminium oxide wafer was investigated in a nitrogen—oxygen atmosphere. 相似文献
108.
Experiments were conducted to investigate the fate of ethylbenzoate and soil microorganisms in shallow aquifers. Biodegradation and volatilization have been identified as the major mechanisms in attenuating ethylbenzoate in contaminated soils. The rate of volatilization was experimentally found to be limited by gas-phase diffusion. The parameters of an available model, i.e., the maximum specific growth rate and the saturation constant, have been estimated by fitting the model to the experimental data obtained with ethylbenzoate as the carbon source; the former was 0.49 h−1, and the latter was 62 mg L−1. Various facets of biodegradation, including the effects of mass-transfer resistance and initial distribution of microorganisms, have been numerically analyzed on the basis of the model. 相似文献
109.
Preparation of nanosized titania powder via the controlled hydrolysis of titanium alkoxide 总被引:7,自引:0,他引:7
Jinyuan Chen Lian Gao Junghua Huang Dongsheng Yan 《Journal of Materials Science》1996,31(13):3497-3500
By controlling the hydrolysis of titanium butoxide, followed with or without an ethanol washing process, the preparation of nanoscale titania powder was studied in detail. The characteristics of different powders produced by the direct precipitation (without an ethanol wash) and ethanol wash processes were studied by X-ray diffraction, transmission electron microscopy, BET, thermogravimetry and differential thermal analysis techniques. By comparison, it was found that both the direct precipitation and ethanol wash methods can obtain slightly agglomerated nanoscale titania powders of less than 15 nm, but the ethanol wash can further reduce the agglomeration. The particle sizes of titania powders can be modified while still retaining the anatase structure. 相似文献
110.
Jian -Ping Wang He -Lie Luo Nai -Fei Gao Yuan -Yuan Liu 《Journal of Materials Science》1996,31(3):727-730
The Fe-Ag granular metal solid samples with 10% and 30% weight iron have been successfully fabricated using a sol-gel method, which are characterized by X-ray diffraction and transmission electron micrography. The average diameters of iron particles are from about a few nanometres to a few tens of nanometres controlled by the reducing temperature. The evolution of magnetic properties and microstructure during heat treating are described in detail and explained by using the superparamagnetism, single domain and multi domain theories. The magnetic anisotropy of the Fe-Ag granular solid is studied by using the law of approach to saturation. It is found that the magnetic anisotropy constant is in the order of 105 J m–3 which is higher than the value of the bulk iron and increases with the increase of reducing temperature. 相似文献