全文获取类型
收费全文 | 21061篇 |
免费 | 284篇 |
国内免费 | 598篇 |
学科分类
工业技术 | 21943篇 |
出版年
2023年 | 64篇 |
2022年 | 82篇 |
2021年 | 88篇 |
2020年 | 54篇 |
2019年 | 95篇 |
2018年 | 112篇 |
2017年 | 69篇 |
2016年 | 82篇 |
2015年 | 114篇 |
2014年 | 208篇 |
2013年 | 204篇 |
2012年 | 1942篇 |
2011年 | 2470篇 |
2010年 | 654篇 |
2009年 | 373篇 |
2008年 | 1693篇 |
2007年 | 1618篇 |
2006年 | 1360篇 |
2005年 | 1185篇 |
2004年 | 1036篇 |
2003年 | 857篇 |
2002年 | 764篇 |
2001年 | 641篇 |
2000年 | 674篇 |
1999年 | 419篇 |
1998年 | 293篇 |
1997年 | 232篇 |
1996年 | 264篇 |
1995年 | 279篇 |
1994年 | 215篇 |
1993年 | 207篇 |
1992年 | 282篇 |
1991年 | 278篇 |
1990年 | 252篇 |
1989年 | 209篇 |
1988年 | 210篇 |
1987年 | 263篇 |
1986年 | 249篇 |
1985年 | 241篇 |
1984年 | 229篇 |
1983年 | 172篇 |
1982年 | 205篇 |
1981年 | 163篇 |
1980年 | 142篇 |
1979年 | 106篇 |
1978年 | 68篇 |
1976年 | 38篇 |
1965年 | 47篇 |
1964年 | 38篇 |
1956年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions. 相似文献
2.
John F.MOXNES Anne K.PRYTZ ?yvind FR?YLAND Stian SKRIUDALEN Steinar B?RVE Gard ?DEG?RDSTUEN 《兵工学报(英文版)》2015,(1):1-9
For the characterization of the behaviors of a metal material in events like expanding warheads, it is necessary to know its strength and ductility at high strain rates, around 104e105/s. The flyer plate impact testing produces the uniform stress and strain rates but the testing is expensive. The Taylor test is relatively inexpensive but produces non-uniform stress and strain fields, and the results are not so easily inferred for material modeling. In the split-Hopkinson bar(SHB), which may be used in compression, tension and torsion testing, the strain rates never exceeds 103/s. In the present work, we use the expanding ring test where the strain rate is 104e105/s. A streak camera is used to examine the expanding ring velocity, and a water tank is used to collect the fragments. The experimental results are compared with the numerical simulations using the hydrocodes AUTODYN, IMPETUS Afea and a regularized smooth particle(RSPH) software. The number of fragments increases with the increase in the expansion velocity of the rings. The number of fragments is similar to the experimental results. The RSPH software shows much the same results as the AUTODYN where the Lagrangian solver is used for the ring. The IMPETUS Afea solver shows a somewhat different fragmentation characteristic due to the node splitting algorithm that induces pronounced tensile splitting. 相似文献
3.
4.
This paper presents an overview of our recent work on the use of soft lithography and two-phase fluid flow to form arrays of droplets. The crucial issues in the formation of stable arrays of droplets and alternating droplets of two sets of aqueous solutions include the geometry of the microchannels, the capillary number, and the water fraction of the system. Glass capillaries could be coupled to the PDMS microchannels and droplets could be transferred into glass capillaries for long-term storage. The arrays of droplets have been applied to screen the conditions for protein crystallization with microbatch and vapor diffusion techniques. 相似文献
5.
A.Molin K.GhanbariAhari B.Josiek J.Molint 《中国耐火材料》2003,12(4):7-10
Physical properties and microstructural evolution on firing of 3 types of bauxite based refractory bricks were carried out using techniques such as porosimetry,XRD and SEM.The groups differed from each other by progressive refining of the matrix or bond phase.It is revealed that such a refinement of the matrix can improve the high temperature properties of the bricks made from poor grade materials. 相似文献
6.
7.
8.
在cdma20001x前向信道中,要对一段信号进行传送,一般选用QPSK调制,因为QPSK调制比QAM更适合噪音环境。采用TI6000系列的TMS320C6711芯片处理前向信道信号,可以对复杂性和实时性较高的信号做采集、量化、编码、调制等实时处理,主要功能通过软件编程实现,从而使系统具有结构灵活、可靠性高、可扩展等优点。 相似文献
9.
在2005年SPE的拉丁美洲和加勒比海石油工程会议上.阿尔伯塔大学的科研人员介绍了加拿大稠油、超稠油资源的开发情况,以及开发适用技术和面临的挑战,其提供的信息对世界其他地区的稠油资源的开发也会起到一定的借鉴作用。[编者按] 相似文献
10.
Marks L D Ciston J Deng B Rondinelli J 《电子显微学报》2006,25(B08):1-2
Many areas of structure analysis have focused on finding the locations of the atoms. If, instead of the atoms, we knew the positions of the electrons we would in fact know much more, and in most respects knowing where the nuclei are is not important. There is a long history of measurements using precise electron diffraction or X-ray diffraction of the average charge density in materials, but extending beyond to local charge density is, as yet, an unexplored area. 相似文献