全文获取类型
收费全文 | 136781篇 |
免费 | 16323篇 |
国内免费 | 11051篇 |
专业分类
电工技术 | 12663篇 |
技术理论 | 4篇 |
综合类 | 13026篇 |
化学工业 | 16398篇 |
金属工艺 | 9296篇 |
机械仪表 | 10052篇 |
建筑科学 | 10648篇 |
矿业工程 | 4970篇 |
能源动力 | 3709篇 |
轻工业 | 13163篇 |
水利工程 | 4790篇 |
石油天然气 | 5866篇 |
武器工业 | 1948篇 |
无线电 | 15834篇 |
一般工业技术 | 12151篇 |
冶金工业 | 6371篇 |
原子能技术 | 2394篇 |
自动化技术 | 20872篇 |
出版年
2024年 | 839篇 |
2023年 | 2252篇 |
2022年 | 5162篇 |
2021年 | 6741篇 |
2020年 | 4898篇 |
2019年 | 3573篇 |
2018年 | 3920篇 |
2017年 | 4594篇 |
2016年 | 4066篇 |
2015年 | 6329篇 |
2014年 | 7830篇 |
2013年 | 9203篇 |
2012年 | 11267篇 |
2011年 | 12025篇 |
2010年 | 11361篇 |
2009年 | 10486篇 |
2008年 | 11008篇 |
2007年 | 10502篇 |
2006年 | 9030篇 |
2005年 | 7280篇 |
2004年 | 5086篇 |
2003年 | 3495篇 |
2002年 | 3295篇 |
2001年 | 2902篇 |
2000年 | 2323篇 |
1999年 | 1196篇 |
1998年 | 778篇 |
1997年 | 519篇 |
1996年 | 425篇 |
1995年 | 357篇 |
1994年 | 269篇 |
1993年 | 219篇 |
1992年 | 153篇 |
1991年 | 105篇 |
1990年 | 96篇 |
1989年 | 101篇 |
1988年 | 55篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 24篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 28篇 |
1980年 | 42篇 |
1979年 | 26篇 |
1977年 | 44篇 |
1976年 | 81篇 |
1959年 | 21篇 |
1951年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
The majority of patients with soft tissue or bone sarcomas of the upper extremity can be treated today with limb-saving procedures using combined modality therapies. For patients with a tumor in the shoulder area, sometimes an interscapulothoracic amputation is the only radical surgical treatment. However, in selected cases, in which the tumor does not involve the neurovascular bundle, a limb-sparing alternative might be the Tikhoff-Linberg resection. Normal function of the hand and forearm, with reasonable function of the elbow, can be maintained by this procedure. Four case histories are reported. 相似文献
162.
矿化剂对氧化铬绿色釉呈色性能的影响 总被引:2,自引:0,他引:2
针对氧化铬绿色釉存在色调暗不够鲜艳的缺点,研究了矿化剂对其呈色性能的影响,经分光光度分析的扫描电镜测试,表明矿化剂具有一定的助熔作用和还原性,从而提高了氧化铬绿色釉的鲜艳度和着色力,增强了装饰性,同时矿化剂还能降低烧成温度,节约能源,具有应用价值。 相似文献
163.
用透射电镜观察了30CrMnSiNi2A钢等温的微观组织,疲劳裂纹扩展行为、裂纹尖端塑性区和位错结构,结果表明,等温状态组织由马氏体和贝氏体组成。在一个奥氏体晶粒内一般存在四个板条领域、裂纹尖端的塑性区内存在主位错带,疲劳断裂的基本组织单元为板条晶或板条束。裂纹遇到板条束界时方向发生较大偏斜。 相似文献
164.
为了适应电力工业发展和国家新兴产业政策的需要,本文扼要介绍了21世纪新建电厂在热控系统的规划设计方面应做的改进和注意的问题.并在此基础上阐述了一些个人的观点和看法供管理、设计和技术人员参考. 相似文献
165.
用溶胶-凝胶法制备TiO2及TiO2/SiO2复合纳米材料,作为PBT(聚对苯二甲酸丁二酯)合成的催化剂,与现在普通使用的催化剂钛酸丁酯进行了比较和研究。结果发现,TiO2/SiO2复合纳米材料催化性能最好,纳米TiO2次之。 相似文献
166.
Some organic phosphines labeled with 117mSn(Ⅳ) have been provedpromising for imaging and pain palliation of bone tumor. In this paper, a prelimi-nary investigation on the adsorption characteristics of EDTMP (ethelenediaminete-tramethylene phosphoric acid) labeled with 117mSn(Ⅳ) on HA(hydroxyapatite) andcollagen, and an investigation on the adsorption mechanism of 117mSn(Ⅳ)-EDTMPon HA was presented.`` 相似文献
167.
M. S. Han S. R. Hahn H. C. Kwon Y. Bin T. W. Kang J. H. Leem Y. B. Hou H. C. Jeon J. K. Hyun Y. T. Jeoung H. K. Kim J. M. Kim T. W. Kim 《Journal of Electronic Materials》1998,27(6):680-683
Double-crystal x-ray rocking curve (DCRC) and secondary-ion mass-spectroscopy (SIMS) measurements have been performed to investigate the effect of rapid thermal annealing on the interdiffusion behavior of Hg in HgTe/CdTe superlattices grown on Cd0.96Zn0.04Te (211)B substrates by molecular beam epitaxy. The sharp satellite peaks of the DCRC measurements on a 100-period HgTe/CdTe (100Å/100Å) superlattice show a periodic arrangement of the superlattice with high-quality interfaces. The negative direction of the entropy change obtained from the diffusion coefficients as a function of the reciprocal of the temperature after RTA indicates that the Hg diffusion for the annealed HgTe/CdTe superlattice is caused by an interstitial mechanism. The Cd and the Hg concentration profiles near the annealed HgTe/CdTe superlattice interfaces, as measured by SIMS, show a nonlinear behavior for Hg, originating from the interstitial diffusion mechanism of the Hg composition. These results indicate that a nonlinear interdiffusion behavior is dominant for HgTe/CdTe superlattices annealed at 190°C and that the rectangular shape of HgTe/CdTe superlattices may change to a parabolic shape because of the intermixing of Hg and Cd due to the thermal treatment. 相似文献
168.
169.
本文提出了一种新的限制输出个数减少随机多变量自适应控制中辨识参数的方法,并给出了减少辨识参数的极点配置自适应算法。虽然采用n个输入1个输出的减少辨识参数的模型来设计控制器,但所提出的控制器能够保证被控系统的几个输出跟踪参考输入信号,仿真结果表明,所提出的方法是成功的。 相似文献
170.
HE Montgomery P Clarkson CM Dollery K Prasad MA Losi H Hemingway D Statters M Jubb M Girvain A Varnava M World J Deanfield P Talmud JR McEwan WJ McKenna S Humphries 《Canadian Metallurgical Quarterly》1997,96(3):741-747
PURPOSE: To determine the radiologic characteristics of cystic dystrophy of the duodenal wall. MATERIALS AND METHODS: Ten patients with cystic dystrophy of the duodenal wall and chronic pancreatitis underwent ultrasonography (US) (n = 10), computed tomography (CT) (n = 10), endoscopic US (n = 5), and endoscopic retrograde cholangiopancreatography (ERCP) (n = 9). Cystic dystrophy of the duodenal wall was classified as either cystic or solid. The imaging findings were retrospectively analyzed and compared with findings at pancreatoduodenectomy (n = 10). RESULTS: The more frequent cystic type (n = 7) of cystic dystrophy of the duodenal wall was characterized by the presence of easily recognizable cystic lesions (diameter, more than 1 cm), located within the thickened wall of the second portion of the duodenum. The solid type (n = 3) of cystic dystrophy of the duodenal wall demonstrated fibrous thickening of the duodenal wall within which small cysts (diameter, less than 1 cm) were present. The intraduodenal cysts were usually elongated or bilobate with a thick wall. The thickening of the duodenal wall appeared as a solid layer between the duodenal lumen and the pancreas, hypoechoic at US, isoattenuating at unenhanced CT, and hypoattenuating in the early phase (after initiation of infusion of contrast material) and isoattenuating in the late phase (after completion of infusion) at contrast material-enhanced CT. Findings at retrospective analysis of CT and endoscopic US images were characteristic. CONCLUSION: Imaging modalities, notably CT and endoscopic US, helped establish the diagnosis of cystic dystrophy of the duodenal wall. 相似文献