全文获取类型
收费全文 | 13391篇 |
免费 | 1240篇 |
国内免费 | 215篇 |
专业分类
电工技术 | 419篇 |
技术理论 | 1篇 |
综合类 | 286篇 |
化学工业 | 3022篇 |
金属工艺 | 625篇 |
机械仪表 | 670篇 |
建筑科学 | 423篇 |
矿业工程 | 96篇 |
能源动力 | 492篇 |
轻工业 | 1367篇 |
水利工程 | 96篇 |
石油天然气 | 239篇 |
武器工业 | 48篇 |
无线电 | 2022篇 |
一般工业技术 | 2699篇 |
冶金工业 | 815篇 |
原子能技术 | 155篇 |
自动化技术 | 1371篇 |
出版年
2024年 | 32篇 |
2023年 | 219篇 |
2022年 | 373篇 |
2021年 | 586篇 |
2020年 | 421篇 |
2019年 | 386篇 |
2018年 | 456篇 |
2017年 | 525篇 |
2016年 | 557篇 |
2015年 | 540篇 |
2014年 | 729篇 |
2013年 | 947篇 |
2012年 | 966篇 |
2011年 | 1208篇 |
2010年 | 889篇 |
2009年 | 840篇 |
2008年 | 710篇 |
2007年 | 608篇 |
2006年 | 554篇 |
2005年 | 437篇 |
2004年 | 391篇 |
2003年 | 301篇 |
2002年 | 275篇 |
2001年 | 233篇 |
2000年 | 215篇 |
1999年 | 219篇 |
1998年 | 304篇 |
1997年 | 184篇 |
1996年 | 146篇 |
1995年 | 94篇 |
1994年 | 90篇 |
1993年 | 69篇 |
1992年 | 49篇 |
1991年 | 31篇 |
1990年 | 36篇 |
1989年 | 34篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1974年 | 7篇 |
1971年 | 7篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Research in CASE environments has focused on two kinds of integration: tool and object. A higher level of integration, process integration, which represents development activities explicitly in a software process model to guide and coordinate development and to integrate tools and objects, is proposed. Process integration uses software process models (SPMs) a process driver, a tool set, and interfaces for both developers and managers to form the backbone of a process-driven CASE environment. The developer's interface, a working environment that lets developers enact an SPM, and the manager's interface which gives managers and analysts the tools to define, monitor, and control the SPMs that developers are working on concurrently are discussed. The Softman environment experiment, an implementation of process-driven CASE environments with existing CASE environments, is reviewed 相似文献
42.
混合结构楼房爆破拆除倒塌范围的确定 总被引:2,自引:1,他引:1
通过对混合结构楼房爆破倾倒过程特点的分析,提出了楼房在倾倒过程中的运动计算模型,并应用体积平衡原理,得到这类楼房爆破爆堆参数计算公式,用该公式计算的结果与实例中爆堆实测数据相比较,相对误差不超过11%. 相似文献
43.
Han-Sam Cho Hyun-Kyo Jung 《Energy Conversion, IEEE Transaction on》2002,17(4):492-499
The force equation of a synchronous permanent-magnet planar motor (SPMPM) was investigated. The flux density distribution of a two-dimensional (2-D) magnet array for a SPMPM was obtained by solving the equations of the scalar magnetic potential. The expressions of the force and back-EMF constant were derived and examined. Using these expressions, the conditions for normal operation of the SPMPM were found and the optimal design was determined in order to maximize the force of the SPMPM. 相似文献
44.
An existing extensive database on the isothermal and thermomechanical fatigue behaviour of high-temperature titanium alloy
EVII 834 and dispersoid-strengthened aluminum alloy X8019 in SiC particle-reinforced as well as unreinv conditions was used
to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining
material life by crack propagation consideration. Selection of the correct microstructural concepts was emphasised and these
concepts were, then adjusted by using data from independent experiments in order to avoid any sort of fitting. It is shown
that the cyclic /-integral (δJeff concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately
identical to pure fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep-fatigue
damage parameter δCF introduced by Riedel can be successfully applied. If environmental effects are very pronounced, the accelerating influence
of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law.
Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental
attack is assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account. 相似文献
45.
The photonic quantum ring (PQR) laser is a three dimensional whispering gallery (WG) mode laser and has anomalous quantum wire properties, such as microampere to nanoampere range threshold currents and √T‐dependent thermal red shifts. We observed uniform bottom emissions from a 1‐kb smart pixel chip of a 32×32 InGaAs PQR laser array flip‐chip bonded to a 0.35 µm CMOS‐based PQR laser driver. The PQR‐CMOS smart pixel array, now operating at 30 MHz, will be improved to the GHz frequency range through device and circuit optimization. 相似文献
46.
47.
The gas flow sputter technique was invented a few years ago particularly for the inexpensive fabrication of sophisticated ceramic layers. Meanwhile, it has matured and become increasingly powerful. Today it is on the verge of being applied in industrial fabrication processes. The present article gives an overview over the method, its characteristics and the numerous applications. 相似文献
48.
49.
50.
Coating of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN–PT) relaxor ferroelectrics by a sol–gel method is followed by growth of epitaxial SrRuO3 (SRO) metallic oxide electrodes on SrTiO3 (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN–PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN–PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed. 相似文献