首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3319篇
  免费   55篇
  国内免费   4篇
电工技术   156篇
综合类   1篇
化学工业   708篇
金属工艺   202篇
机械仪表   107篇
建筑科学   35篇
矿业工程   15篇
能源动力   110篇
轻工业   178篇
水利工程   8篇
无线电   281篇
一般工业技术   506篇
冶金工业   754篇
原子能技术   66篇
自动化技术   251篇
  2023年   12篇
  2022年   36篇
  2021年   69篇
  2020年   29篇
  2019年   27篇
  2018年   32篇
  2017年   26篇
  2016年   46篇
  2015年   36篇
  2014年   70篇
  2013年   149篇
  2012年   108篇
  2011年   128篇
  2010年   106篇
  2009年   114篇
  2008年   135篇
  2007年   143篇
  2006年   100篇
  2005年   98篇
  2004年   75篇
  2003年   78篇
  2002年   98篇
  2001年   67篇
  2000年   64篇
  1999年   97篇
  1998年   289篇
  1997年   211篇
  1996年   120篇
  1995年   104篇
  1994年   85篇
  1993年   81篇
  1992年   34篇
  1991年   46篇
  1990年   39篇
  1989年   39篇
  1988年   29篇
  1987年   30篇
  1986年   22篇
  1985年   36篇
  1984年   30篇
  1983年   21篇
  1982年   25篇
  1981年   18篇
  1980年   22篇
  1979年   27篇
  1978年   16篇
  1977年   28篇
  1976年   30篇
  1975年   9篇
  1973年   11篇
排序方式: 共有3378条查询结果,搜索用时 15 毫秒
51.
The implementation on the vector processor of Incomplete LU factorization in the Preconditioned Conjugate Gradient method and other Preconditioned CG-like methods for the numerical solutions of the partial differential equations is discussed. For sufficient vectorization, a variant of the standard 5-point difference scheme for 2-dimensional problems is introduced. The convergence property of ILU factorization for this variant is examined in comparison with that vectorized with the usual hyperplane ordering method for the standard 5-point difference scheme on the vector processor. The efficiency and effectiveness of this factorization for the variant of the difference scheme is demonstrated through several computational experiments.  相似文献   
52.
Summary To understand some main ink flow mechanisms in a mimeograph printer, the continuum mechanics theory of fluid-saturated porous solids is applied to analyze the ink flow through screens and a printing master, which are modeled by a fluid-filled poroelastic single layer. The layer is assumed to be pressed by a press roller from below and to be subjected from above to the hydrodynamic lubrication pressure induced between a printing drum and an ink roller. Nonlinear elasticity of the layer and dependence of the permeability on its deformation are taken into account. The numerical results show some important results: e.g., squeezing-out of the ink from the layer by the layer compaction by the press roller plays an important role, especially for the case where the compression duration is small in comparison with the characteristic time of the ink-filled poroelastic layer.  相似文献   
53.
We report a nephrotic syndrome patient with eosinophilia who developed ileus, epigastralgia and malabsorption due to strongyloidiasis which became symptomatic by steroid therapy. The patient was then treated with thiabendazole and recovered. A percutaneous renal biopsy revealed minimal change nephrotic syndrome. This renal injury may be brought on by severe infection of Strongyloides stercoralis. It is important to rule out strongyloidiasis prior to corticosteroid therapy to patients from eosinophilia endemic areas.  相似文献   
54.
Motility related protein 1 (MRP1/CD9) expression in colon cancer   总被引:1,自引:0,他引:1  
STUDY OBJECTIVES: To examine the incidence and clinical significance of prolonged air leak (PAL) in patients undergoing radical upper lobectomy and to determine potential risk factors for PAL in this group of patients. DESIGN: Retrospective review of a prospective database. SETTING: Experience of one thoracic surgeon at a tertiary care cancer center. PATIENTS: One hundred consecutive patients undergoing right upper lobectomy and mediastinal lymph node dissection for non-small cell lung cancer over an 11-year period. MEASUREMENTS: PAL was defined as an air leak lasting >7 days. Preoperative, intraoperative, and postoperative clinical data were collected and analyzed to determine the factors associated with PAL. RESULTS: PAL was the most prevalent postoperative complication, comprising 25.5% of all complications seen, and lasting an average of 12.1+/-5.3 days. In 21 of the 26 patients with PAL, this complication was the only morbidity identified. There was no statistically significant difference in patient age, gender, preoperative FEV1 and diffusion of carbon monoxide, exposure to neoadjuvant chemotherapy, status of pulmonary fissures, or pathologic stage between the PAL group vs the remaining 74 patients without this complication. A significantly greater proportion of patients with PAL had FEV1/FVC ratio < or =50% (6/26 vs 5/74; p=0.02). Patients with PAL had significantly longer median length of hospital stay (11 vs 7 days; p=0.0001). Moreover, PAL was the single most common reason for an extended length of hospitalization (21/58, 36% of all causes). CONCLUSION: PAL is an alarmingly common postoperative complication and is the most frequent cause of an extended length of hospital stay in patients undergoing radical upper lobectomy. Severe obstructive pulmonary disease predisposes patients to the development of this complication.  相似文献   
55.
In this paper, we propose a multi-agent learning system for the control of an intelligent robot, based on a model of the human consciousnesses, including the ego. We pay attention to the intelligent learning processes of human beings. We try to give a robot a high learning ability by modeling the roles of the human consciousnesses, including the ego. In most ordinary methods, the instructions for learning are given from outside the system only. In the proposed method, the instructions are given not only from outside, but also from inside (from other agents in the system). Therefore, the robot can learn efficiently because it has more instructions than usual. The learning is also more flexible, since an agent learns by instructions from other agents while the learning agent and one of the instructing agents exchange roles according to changes in the environment. We experimentally verified that the proposed method is efficient by using an actual robot.  相似文献   
56.
A binary blend which consists of two incompatible polymers such as poly(vinyl chloride) and polyethylene has been performed through a partial co-crosslinking reaction with peroxide to give a co-crosslinked blend with a uniform dispersion of small polyethylene particles and with an improved mechanical property. The results are obtained through the formation of a co-crosslinked product which acts as a potential solid phase dispersant as well as a well-bonded reinforcing interlayer on polyethylene particles uniformly dispersed in poly(vinyl chloride) matrix. The resulting blends (PVC/PE=10/90 wt) give carbon spherules of 0.5 to 1m diameter through pressure-carbonization at 650° C for 1 h.  相似文献   
57.
Molybdenum plate was siliconized using Si2Cl6 as a silicon source, and the siliconizing conditions and some of its properties were examined. The siliconizing of the molybdenum plate began by the deposition here and there of island-like MoSi2 deposits 4 to 6m thick in the initial stage (after 10 min induction time), and then coalescence of the deposits proceeded to form a uniform MoSi2 layer all over the molybdenum plate after 30 min siliconizing time. The weight decrease of the siliconized plate by anodic dissolution in 0.2 M sulphuric acid reduced exponentially with increasing thickness of the MOSi2 layer, and no weight decrease was observed at all above 16m thickness. The sea water corrosion and sea sand abrasion resistivities of the siliconized molybdenum plate increased with increasing siliconizing temperature and Si2Cl6 flow rate.  相似文献   
58.
The enhancement ofT c in Pb-Bi-Sn and Pb-Bi-In system alloy filaments produced by glass-coated melt spinning was investigated as a means of producing a new type of superconducting filament with highT c. Long filaments of Pb-Bi-Sn alloy withT c higher than 10 K and Pb-Bi-In alloy withT c higher than 9 K were obtained from the molten state at a temperature of 1500 K with a winding speed of 2.63 m sec–1. For example, a Pb45Bi35Sn20 filament withT c of 10.1 K was 15 m in diameter and polycrystalline with a grain size of 100 nm. The structure of the filament was a mixture of , tin and bismuth phases and a metastable phase of mixed structure of bismuth and supersaturated solid solution of tin in -phase was detected. TheT c of the filament decreased on heat treatment. A metastable phase of mixed structure of bismuth and -phase was also detected for a Pb45Bi45In10 filament withT c of 9.3 K. As the metastable phase for the Pb-Bi-In filament was more unstable than that for the Pb-Bi-Sn filament, theT c of the filament was drastically decreased by heat treatment. The metastable phase was considered to play an important role in the enhancement ofT c for Pb-Bi-Sn and Pb-Bi-In alloy filaments.  相似文献   
59.
Decomposition of t-butylhydroperoxide was retarded by triazine thiols and their zinc salts, but accelerated by the copper salts of triazine thiols as well as sulfur compounds such as dithiocarbamates and mercaptobenzothiazolates. Triazine thiols and their zine salts are effective antioxidants for polyethylene crosslinked with peroxide and containing copper, and for protecting epichlorohydrin vulcanizates against attack by “sour” or hydroperoxide-containing gasoline.  相似文献   
60.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号