全文获取类型
收费全文 | 202651篇 |
免费 | 15544篇 |
国内免费 | 7678篇 |
专业分类
电工技术 | 11101篇 |
技术理论 | 14篇 |
综合类 | 11149篇 |
化学工业 | 34672篇 |
金属工艺 | 10443篇 |
机械仪表 | 11982篇 |
建筑科学 | 16239篇 |
矿业工程 | 4852篇 |
能源动力 | 5845篇 |
轻工业 | 12568篇 |
水利工程 | 3167篇 |
石油天然气 | 10894篇 |
武器工业 | 1345篇 |
无线电 | 25268篇 |
一般工业技术 | 26449篇 |
冶金工业 | 10658篇 |
原子能技术 | 2104篇 |
自动化技术 | 27123篇 |
出版年
2024年 | 578篇 |
2023年 | 3065篇 |
2022年 | 4775篇 |
2021年 | 7594篇 |
2020年 | 5639篇 |
2019年 | 4875篇 |
2018年 | 5320篇 |
2017年 | 6056篇 |
2016年 | 5597篇 |
2015年 | 7233篇 |
2014年 | 9457篇 |
2013年 | 12220篇 |
2012年 | 12225篇 |
2011年 | 13864篇 |
2010年 | 11608篇 |
2009年 | 11454篇 |
2008年 | 10871篇 |
2007年 | 10463篇 |
2006年 | 10856篇 |
2005年 | 9628篇 |
2004年 | 6562篇 |
2003年 | 5773篇 |
2002年 | 5251篇 |
2001年 | 4723篇 |
2000年 | 4868篇 |
1999年 | 5627篇 |
1998年 | 5264篇 |
1997年 | 4321篇 |
1996年 | 3928篇 |
1995年 | 3292篇 |
1994年 | 2754篇 |
1993年 | 2172篇 |
1992年 | 1684篇 |
1991年 | 1257篇 |
1990年 | 996篇 |
1989年 | 863篇 |
1988年 | 665篇 |
1987年 | 481篇 |
1986年 | 372篇 |
1985年 | 318篇 |
1984年 | 193篇 |
1983年 | 180篇 |
1982年 | 155篇 |
1981年 | 138篇 |
1980年 | 129篇 |
1979年 | 96篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
951.
952.
本文以ispLISI1000系列为例,对isp技术及ispLSI器件进行了较为详细的介绍,并结合具体设计实例,介绍ispLS开发工具的使用。 相似文献
953.
陈仕文 《北京印刷学院学报》1993,(1)
本文根据人眼视觉特性、孟塞尔方程及彩色复制理论,并结合实际工艺路线和工艺条件,推导出标准阶调复制曲线和标准电分工作曲线。它与德国Hell公司所绘的电分标准工作曲线基本一致。并做到了各工序有数据,有质量标准,使平印制版做到有规可循。 相似文献
954.
This paper describes the implementation and experimental studies of an adaptive self-optimizing pole shifting power system stabilizer. Using an Intel iSBC386/21 single-board computer, the adaptive power system stabilizer has been tested on a physical model of a single-machine infinite-bus power system. Under different operating conditions and disturbances, the behavior of the proposed adaptive stabilizer was investigated. Comparison has also been made to a digital-type conventional fixed-parameter power system stabilizer. Results of the experimental studies show that the proposed adaptive stabilizer outperforms the conventional stabilizer. 相似文献
955.
露天矿山裂隙岩体爆破孔距变化的研究 总被引:1,自引:0,他引:1
文中指出裂隙岩体大孔距爆破在一点条件下与结构面的特性变化关系密切,并按两组三结构面建立了孔距计算公式。 相似文献
956.
By using scanning polarization force microscopy,the deliquescence process and the atomic steps on the cleavage surface of CaCO3 in air were studied in situ.Under an exposure to medium umidity(-57%),the sloiw step movement has been observed. 相似文献
957.
Occlusion of large atrial septal defects with a centering buttoned device: early clinical experience
EB Sideris M Leung JH Yoon CR Chen R Lochan AM Worms C Rey B Meier 《Canadian Metallurgical Quarterly》1996,131(2):356-359
A feasibility clinical study was conducted for the transcatheter occlusion of large ostium secundum atrial septal defects with the centering buttoned device. The centering buttoned device is a modification of the regular buttoned device in which a centering counter-occluder is sutured at the central 40% portion of the occluder. During centering it is stretched, forming a parachute-shaped structure and pulling the occluder over the center of the defect. During buttoning, the counter-occluder forms a double figure eight, opposing the right atrial side of the atrial septum. Occlusion was performed in 12 patients aged 6 to 56 years. All had been rejected for transcatheter occlusion by the regular buttoned device, because of either their defect size or the lack of adequate septal rim. The defect size varied between 23 and 31 mm, and the device size varied between 45 and 60 mm. Nine had immediate effective occlusions of their defects and three residual shunts. One patient with unbuttoning had hemolysis at 2 weeks and underwent surgery. Early results of the transcatheter occlusion of large atrial septal defects are promising, and larger clinical trials are justified. 相似文献
958.
G Han T Chen J Yang J Dai R Xu Y Zhang J Okano R Yui H Nakajima T Hamasaki 《Canadian Metallurgical Quarterly》1996,21(10):591-4, 639
This paper reports the GC determination of 20 organochlorine pesticides in Chinese drugs Flos Ionicerae and Moluodan etc by the present method of Japan for determinaing pesticide residues. The results suggest that except Folium Isatidis, Radix Codonopsis and Sanqi Pian all accord with the for provisions pesticide residues in Japanese foodstuffs. 相似文献
959.
OBJECTIVE: To examine the relative contribution of polymorphonuclear neutrophil (PMN) vs endothelial cell (EC) activation on the adherence and subsequent killing of ECs by PMNs. DESIGN: In vitro comparative studies of PMN-EC adherence and cytotoxicity. SETTING: Research laboratory and the surgical intensive care unit of a tertiary-level university hospital. PATIENTS: Patients with systemic inflammatory response syndrome admitted to the surgical intensive care unit and hospitalized preoperative noninfected surgical patients. INTERVENTION: None. METHODS: Polymorphonuclear neutrophils were isolated from 21 healthy volunteers, 22 preoperative patients, and 30 patients from the surgical intensive care unit with systemic inflammatory response syndrome. The PMNs were activated with lipopolysaccharide, 100 ng/mL (Escherichia coli 0111:b4), for 40 minutes at 37 degrees C before the adherence and cytotoxicity assays. Human umbilical vein endothelial monolayers were stimulated with tumor necrosis factor alpha, 25 ng/mL, and interleukin 1 beta, 15 U/mL, for 3 hours. The PMNs or EC cells were labeled with sodium chromate Cr 51 and used in a standard adherence or killing assay as required. RESULTS: Control and preoperative patient PMN treatment with lipopolysaccharide produced a modest increase in adherence. The PMNs from patients with systemic inflammatory response syndrome showed moderately increased human umbilical vein endothelial cell adherence, and this could not be augmented further with lipopolysaccharide stimulation. There was a marked increase in PMN adherence to EC after EC activation in all study groups (P < .001). Similar to the adherence data, human umbilical vein endothelial cell cytotoxicity was significantly increased in all groups after human umbilical vein endothelial cell activation (P < .01) but not after PMN stimulation with lipopolysaccharide. CONCLUSION: These data suggest that stimulation of ECs is far more important in producing increased adherence and cytotoxicity of EC than PMN stimulation with lipopolysaccharide in all study groups. Therapeutic efforts in patients with systemic inflammatory response syndrome should be focused on the EC. 相似文献
960.
Weitang Li Zhenghui Li Shifu Zhu Shujun Yin Beijun Zhao Guanxiong Chen 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,370(2-3):435-437
Instead of the temperature oscillation method (TOM), a modified vapor growth method was applied in this paper to grow large HgI2 crystals with fewer lattice defects by providing a relatively stable temperature field during growth. And a new processing technique of HgI2 crystals was developed for detector fabrication by merging solution string-sawing and hand-cleaving. The lattice deformations caused during cleaving were reduced greatly by eliminating passivated layers on the sawed crystal platelets before cleaving. 相似文献