全文获取类型
收费全文 | 618760篇 |
免费 | 113593篇 |
国内免费 | 79052篇 |
专业分类
电工技术 | 65069篇 |
综合类 | 70994篇 |
化学工业 | 75567篇 |
金属工艺 | 54627篇 |
机械仪表 | 38690篇 |
建筑科学 | 45699篇 |
矿业工程 | 31979篇 |
能源动力 | 18763篇 |
轻工业 | 69347篇 |
水利工程 | 22190篇 |
石油天然气 | 27078篇 |
武器工业 | 10247篇 |
无线电 | 73839篇 |
一般工业技术 | 62526篇 |
冶金工业 | 24478篇 |
原子能技术 | 9120篇 |
自动化技术 | 111192篇 |
出版年
2024年 | 5244篇 |
2023年 | 11358篇 |
2022年 | 22572篇 |
2021年 | 28235篇 |
2020年 | 24063篇 |
2019年 | 25664篇 |
2018年 | 27400篇 |
2017年 | 31339篇 |
2016年 | 29313篇 |
2015年 | 36607篇 |
2014年 | 40672篇 |
2013年 | 44991篇 |
2012年 | 53008篇 |
2011年 | 51563篇 |
2010年 | 49286篇 |
2009年 | 45495篇 |
2008年 | 44508篇 |
2007年 | 43231篇 |
2006年 | 36944篇 |
2005年 | 30185篇 |
2004年 | 25656篇 |
2003年 | 17809篇 |
2002年 | 16647篇 |
2001年 | 15095篇 |
2000年 | 12633篇 |
1999年 | 7032篇 |
1998年 | 4450篇 |
1997年 | 3858篇 |
1996年 | 3639篇 |
1995年 | 3653篇 |
1994年 | 3023篇 |
1993年 | 2851篇 |
1992年 | 2753篇 |
1991年 | 2015篇 |
1990年 | 1597篇 |
1989年 | 1516篇 |
1988年 | 1127篇 |
1987年 | 401篇 |
1986年 | 354篇 |
1985年 | 260篇 |
1984年 | 192篇 |
1983年 | 152篇 |
1982年 | 184篇 |
1981年 | 233篇 |
1980年 | 241篇 |
1979年 | 139篇 |
1976年 | 225篇 |
1975年 | 203篇 |
1972年 | 235篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
岩心PI值试验研究及应用 总被引:5,自引:0,他引:5
主要论述了在多功能采油化学用剂评价仪上进行的岩心PI值试验的步骤,现象及结论。重点考察了岩心PI值与渗透率、流量及注入截面面积的关系;平行管岩心复合PI值和其中单管岩心PI值的关系。 相似文献
992.
This paper discusses the seafloor thermalwater spout sedimentary activity in South Yongmei Depression according to the following
evidences: the Yongmei region was in an extended tectonic environment of metaplateform and locally developed intracontinental
rift aulacogen in company with the activity of rich alkali, high potassium volcanics of double-peak type. Several kinds of
hydrothermal sedimentary rocks and the ore-bearing sedimentary formations of copper-polymetals, iron and manganese exist in
this region with a zoning feature of the seafloor thermalwater spout sedimentation.
Project supported by the Science Foundation of NECC for Returns
Synopsis of the first author Wu Chengjian, associated professor, born in 1957, majoring in ore deposit and mineralgraphy. 相似文献
993.
M. Balata L. Cadonati M. Laubenstein G. Heusser M. G. Giammarchi R. Scardaoni V. Torri G. Cecchet A. de Bari A. Perotti 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,370(2-3):605-608
The Borexino experiment, for the study of solar neutrino physics, requires radiopurity at the level of 5 × 10−16 g/g 238U equivalent (or 6 × 10−9 Bq/kg) on a detector mass of many tons of scintillator. Feasibility studies are performed in a counting test facility now operating at LNGS, which consists of 4 t of liquid scintillator viewed by 100 photomultipliers and shielded by 100 t of water. The accomplishment of this goal requires the shielding liquid, water, to be at the 10−13 g/g contamination level (1.2 × 10−6 Bq/kg) or better. This paper describes the water purification system; it consists of a combination of several purification processes to remove particulate, radioactive ions, dissolved gases and other impurities. Residual contaminations are measured by analytical or direct-counting techniques. For radon measurement, particularly challenging at this low activity levels, a low background counting method has been developed. 相似文献
994.
High-T
c
Bi(Pb)-Sr-Ca-Cu-O thin films have been made on single-crystal MgO substrates using high-pressure dc sputtering technique. X-ray studies confirm the crystallinity and highly oriented structure withc-axis perpendicular to the substrate. By optimizing the annealing schedule the formation of the high-T
c
phase is stabilized. The best film exhibited superconducting transition temperature with zero-resistance temperature,T
c(0), as high as 101 K. Temperature dependence ofJ
c
indicates the presence of Josephson-type weak links. 相似文献
995.
The temperature dependence of a marginal Fermi liquid has been calculated. We showed that the expectedT lnT correction is characteristic for the low-temperature domain. The high-temperature domain has a supplementary correction. The results are in agreement with the non-Fermi behavior of some metallic systems the in low-temperature domain. 相似文献
996.
997.
Ben J. A. Kr se Kai M. Compagner Franciscus C. A. Groen 《Robotics and Autonomous Systems》1993,11(3-4):221-230
This paper describes a robust and accurate ultrasonic sensing system for a mobile robot. The system continuously updates a local map of the environment in which obstacles are represented by straight lines or points in a robot centered coordinate frame. The presented algorithms use a Kalman filter for the reduction of the noise in the ultrasonic data and use a systematical error correction (‘bundle correction’) to reduce the uncertainty in obstacle direction. Experiments are carried out in simulation and with a real mobile robot system. Results show that the accuracy with which line parameters can be estimated is in the order of 1 degree for the orientation and about 2 cm for the position. The effect of the bundle correction is significant and maximal when the robot approaches walls under a small angle. 相似文献
998.
999.
1000.
含淀粉聚乙烯膜的时控光降解研究 总被引:2,自引:0,他引:2
使用复合光降解剂,得到了可光降解的生物降解膜。对膜的光降解进行了考察,并对影响光降解的因素进行了讨论,结果表明,我们所制得的膜是一种较好的时控光降解膜。 相似文献