全文获取类型
收费全文 | 122000篇 |
免费 | 9853篇 |
国内免费 | 4700篇 |
专业分类
电工技术 | 6932篇 |
技术理论 | 2篇 |
综合类 | 6069篇 |
化学工业 | 20559篇 |
金属工艺 | 6923篇 |
机械仪表 | 8317篇 |
建筑科学 | 6510篇 |
矿业工程 | 2243篇 |
能源动力 | 4429篇 |
轻工业 | 8761篇 |
水利工程 | 2155篇 |
石油天然气 | 3553篇 |
武器工业 | 1017篇 |
无线电 | 16354篇 |
一般工业技术 | 17869篇 |
冶金工业 | 7263篇 |
原子能技术 | 1575篇 |
自动化技术 | 16022篇 |
出版年
2024年 | 313篇 |
2023年 | 1419篇 |
2022年 | 2709篇 |
2021年 | 4173篇 |
2020年 | 3080篇 |
2019年 | 2741篇 |
2018年 | 3205篇 |
2017年 | 3587篇 |
2016年 | 3840篇 |
2015年 | 4268篇 |
2014年 | 5911篇 |
2013年 | 7433篇 |
2012年 | 8883篇 |
2011年 | 9775篇 |
2010年 | 8470篇 |
2009年 | 8344篇 |
2008年 | 8090篇 |
2007年 | 7192篇 |
2006年 | 6626篇 |
2005年 | 5492篇 |
2004年 | 4509篇 |
2003年 | 4230篇 |
2002年 | 4211篇 |
2001年 | 3650篇 |
2000年 | 2544篇 |
1999年 | 2024篇 |
1998年 | 2159篇 |
1997年 | 1505篇 |
1996年 | 1231篇 |
1995年 | 887篇 |
1994年 | 711篇 |
1993年 | 577篇 |
1992年 | 416篇 |
1991年 | 366篇 |
1990年 | 346篇 |
1989年 | 312篇 |
1988年 | 242篇 |
1987年 | 204篇 |
1986年 | 146篇 |
1985年 | 121篇 |
1984年 | 101篇 |
1983年 | 75篇 |
1982年 | 48篇 |
1981年 | 49篇 |
1980年 | 38篇 |
1979年 | 36篇 |
1978年 | 32篇 |
1977年 | 41篇 |
1976年 | 64篇 |
1975年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
71.
首先揭示出民族风格是与时代风格对立统一、相互依存的一个概念。因而特定的时代需要具有时代精神的民族风格──创新民族风格。在探索此风格的过程中.我们首先要学习日本的战略,然后在学习的基础上实现超越。 相似文献
72.
Jae-Chul Lee Ho-In Lee Gyeung-Ho Kim Jung-Ill Lee 《Metallurgical and Materials Transactions A》1997,28(5):1251-1259
Interfacial reactions in the squeeze-cast SAE 329 Al alloy reinforced with SAFFIL and carbon fibers were investigated using
scanning and transmission electron microscopy and secondary ion mass spectroscopy. The SiO2 layer added as a binder for the preform of SAFFIL fiber appeared to prevent excessive reaction between the fiber and the
molten Al alloy during casting. In the as-cast composite, the reaction between the SiO2 layer and the Al alloy is considered to produce MgO crystals in the vicinity of SAFFIL fiber. With subsequent heat treatment
of the composite to the T6 condition, small crystals of MgO and MgAl2O4 were found to form at the surface of SAFFIL fiber as a result of interfacial reaction between the SiO2 layer and the Al alloy. Even at the T6 condition, significant reactions between the Al alloy and SAFFIL fiber itself were
not observed, indicating the effective role of the binder layer in suppressing the degradation of SAFFIL fiber by reaction
with the Al alloy. 相似文献
73.
Flexible manufacturing systems (FMSs) are able to process a wide variety of operations, but the specific mix of operations that can be performed at any point in time depends upon the combination of tools loaded onto the machines. The machines have tool magazines with finite capacities. We consider the problem of assigning operations and their associated tools to machines (or groups of machines) to maximize the throughput for a specified steady-state mix of orders. Since this objective is difficult to deal with directly, we use an intermediate objective of meeting workload targets for each machine group as closely as possible. A certain form of this intermediate objective has been shown to correlate highly with the original objective.
Since it is computationally intractable to find optimal solutions for problems with more than 20 operations, fast heuristic algorithms are developed. These algorithms are adapted from multi-dimensional bin-packing algorithms. Computational results are reported. 相似文献
Since it is computationally intractable to find optimal solutions for problems with more than 20 operations, fast heuristic algorithms are developed. These algorithms are adapted from multi-dimensional bin-packing algorithms. Computational results are reported. 相似文献
74.
75.
76.
Inn Seock Kim 《Reliability Engineering & System Safety》1996,54(1):83-87
The Technical Specifications (TSs) for a nuclear power plant is an important licensing document which defines various operational requirements or conditions. In light of the recent trends to move towards risk-based regulation, many researchers analyzed the risk impacts associated with the TS requirements, using the plant models, such as event trees or fault trees, that were developed as part of probabilistic safety assessments. This paper presents the insights gained from a review of these risk-based analyses of TSs, focussing on surveillance requirements and AOT (allowed outage time) requirements. 相似文献
77.
The incidence of stress fractures is increasing among competitive and recreational athletes as well as among children and the elderly. By understanding the continuum of bone's response to stress and maintaining an appropriate index of suspicion, the health care provider can diagnose these injuries appropriately. An accurate history and examination is essential and will differentiate stress fractures from other stress reactions. The more common stress fractures are discussed. 相似文献
78.
PURPOSE: Normal retina is firmly attached to the retinal pigment epithelium, but the force of this adhesion drops precipitously within the first 2-3 min after enucleation. The purpose was to study metabolic factors that might be relevant to this postmortem failure of adhesion. METHODS: Dutch rabbit retina was manually peeled from the retinal pigment epithelium on strips of enucleated eyecup within a 37 degrees C bath. Retinal adhesiveness was measured by observing the amount of retinal pigment epithelium that remained adherent to the retina. RESULTS: Autologous whole blood in place of salt solution retarded the decrease in adhesiveness. A solution of hemoglobin alone was similarly effective, whereas methemoglobin solution failed to help the persistence of retinal adhesion. Bubbling oxygen into the salt solution and circulating it to avoid oxygen depletion at the tissue boundary also proved effective at sustaining retinal adhesiveness. Eyes made ischemic in vivo for 5 min or longer, by elevating intraocular pressure, showed virtually no retinal adhesion when enucleated immediately thereafter. However, eyes made ischemic for 10 min, but allowed to regain circulation for 5 min before enucleation, showed a return of retinal adhesiveness to 80% of normal. CONCLUSIONS: Oxidative metabolism is critical to the maintenance of retinal adhesiveness, and the effects of oxygen deprivation on adhesion are reversible within a certain time period. 相似文献
79.
A. Inoue B. G. Kim K. Nosaki T. Yamaguchi T. Masumoto 《Journal of Materials Science Letters》1992,11(12):865-867
On leave from: Honda Research and Development Co., Ltd, Wako 351-01, Japan. 相似文献
80.
Al,Ga取代Bi:DyIG薄膜的磁和磁光特性的研究 总被引:1,自引:0,他引:1
本文报道用热分解法在玻璃衬底上制备了Al和Ga取代的Bi:DYIG薄膜,对其磁和磁光特性做了详细研究.Al和Ga取代的薄膜均可获得好的矩形比和高的矫顽力.对于Bi1.2Dy1.8Fe5-xMXO12(M=A1,GZ)薄膜,A1和G2的最佳替代成份分别为1.0和G.7;最佳晶化温度分别为700o℃和675℃.在波长510nm附近,法拉第旋转角可达8°/um左右.光学吸收和品质因子的研究结果表明,Al和Ga取代能够影响光学吸收和品质因子,其中Ga取代对光学吸收和品质因子的影响较大. 相似文献