全文获取类型
收费全文 | 16069篇 |
免费 | 1276篇 |
国内免费 | 362篇 |
专业分类
电工技术 | 716篇 |
综合类 | 518篇 |
化学工业 | 2975篇 |
金属工艺 | 628篇 |
机械仪表 | 860篇 |
建筑科学 | 707篇 |
矿业工程 | 191篇 |
能源动力 | 629篇 |
轻工业 | 1382篇 |
水利工程 | 183篇 |
石油天然气 | 384篇 |
武器工业 | 64篇 |
无线电 | 2516篇 |
一般工业技术 | 2562篇 |
冶金工业 | 1042篇 |
原子能技术 | 200篇 |
自动化技术 | 2150篇 |
出版年
2024年 | 26篇 |
2023年 | 168篇 |
2022年 | 312篇 |
2021年 | 444篇 |
2020年 | 366篇 |
2019年 | 381篇 |
2018年 | 410篇 |
2017年 | 417篇 |
2016年 | 514篇 |
2015年 | 496篇 |
2014年 | 799篇 |
2013年 | 1084篇 |
2012年 | 1003篇 |
2011年 | 1140篇 |
2010年 | 942篇 |
2009年 | 925篇 |
2008年 | 866篇 |
2007年 | 793篇 |
2006年 | 720篇 |
2005年 | 688篇 |
2004年 | 544篇 |
2003年 | 518篇 |
2002年 | 561篇 |
2001年 | 475篇 |
2000年 | 373篇 |
1999年 | 339篇 |
1998年 | 501篇 |
1997年 | 325篇 |
1996年 | 228篇 |
1995年 | 213篇 |
1994年 | 177篇 |
1993年 | 165篇 |
1992年 | 102篇 |
1991年 | 94篇 |
1990年 | 79篇 |
1989年 | 79篇 |
1988年 | 52篇 |
1987年 | 50篇 |
1986年 | 42篇 |
1985年 | 35篇 |
1984年 | 39篇 |
1983年 | 29篇 |
1982年 | 21篇 |
1981年 | 35篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 23篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
北部湾盆地福山凹陷CO2气成因探讨 总被引:2,自引:1,他引:1
北部湾盆地福山凹陷油气钻探中发现了高含CO2气的天然气气藏。对CO2气稳定碳同位素、伴生稀有气体氦和氩同位素进行了分析研究,结果显示,福山凹陷CO2气稳定碳同位素偏重,(13CCO2为-5.01~-10.08‰,绝大多数样品大于-7.0‰,为无机成因CO2气特征;伴生稀有气体氦同位素3He/4He值为(4.74~5.03)×10-6,R/Ra值为3.38~3.59;伴生稀有气体氩同位素40Ar/36Ar值为1881~2190,也显示出幔源或壳幔混合CO2气的特征。综合判定认为,福山凹陷CO2为壳幔混合成因。始新统流沙港组岩浆岩体分布特征与CO2气藏分布范围基本一致,也表明幔源-岩浆可能是福山凹陷CO2气的主要来源。与南海北部边缘盆地其它地区如珠江口盆地西部、琼东南盆地东部CO2气成因一致,都为幔源-岩浆来源,或壳幔混合来源。 相似文献
22.
Young-Geun Han Sang Hyuck Kim Sang Bae Lee Un-Chul Paek Youngjoo Chung 《Electronics letters》2003,39(15):1107-1108
A novel fabrication method of the core mode blocker by exposing H/sub 2/-loaded Ge-B codoped fibres to local electric arc discharge for application to the LPFGs-based tunable all-fibre bandpass filter with 6.5 nm bandwidth and 40 nm tuning range is presented. 相似文献
23.
Derivation of a second-order switching surface in the boundary control of buck converters 总被引:1,自引:0,他引:1
A second-order switching surface in the boundary control of buck converters is derived in this letter. The formulated switching surface can make the overall converter exhibit better steady-state and transient behaviors than the one with a first-order switching surface. The switching surface is derived by estimating the state trajectory movement after a switching action, resulting in a high state trajectory velocity along the switching surface. This phenomenon accelerates the trajectory moving toward the target operating point. The proposed control scheme has been successfully applied to a 120-W buck converter. The large-signal performance and a comparison with the first-order switching surface have been studied. 相似文献
24.
Saehoon Ju Hyeongdong Kim Hyung-Hoon Kim 《Microwave and Wireless Components Letters, IEEE》2003,13(9):405-407
This letter presents a numerical dispersion relation for the two-dimensional (2-D) finite-difference time-domain method based on the alternating-direction implicit time-marching scheme (2-D ADI-FDTD). The proposed analytical relation for 2-D ADI-FDTD is compared with those relations in the previous works. Through numerical tests, the dispersion equation of this work was shown as correct one for 2-D ADI-FDTD. 相似文献
25.
标准化的目的是“获得最佳秩序和社会效益”,而最佳秩序是企业进行高效率生产和管理的前提条件。能够更及时准确的对企业的生产标准、技术标准、安全标准、管理标准进行监督和管理工作;有助于更好的督促企业在每个环节都建立起互相适应、配套的标准体系,使企业生产活动和经营管理活动井然有序,避免混乱;能够进一步加强对认证及认证咨询工作的质量,提高认证企业质量体系运行的有效性。为此我们提出了建设《哈尔滨市企业产品执行标准数据库管理系统》,对企业的产品执行标准进行登记注册管理,这将有助于组织、监督标准实施工作;有助于组织制订地方标准;推行采用国际标准和国外先进标准;有助于协调指导企业产品标准的制订并管理其备案;组织重要标准的宣传贯彻,监督检查重要标准的实施情况。 相似文献
26.
To determine three‐dimensional fiber orientation states in injection‐molded short‐fiber composites, a confocal laser scanning microscope (CLSM) is used. Since the CLSM optically sections the specimen, more than two images of the cross sections on and below the surface of the composite can be obtained. Three‐dimensional fiber orientation states can be determined by using geometric parameters of fiber images obtained from two parallel cross sections. For experiments, carbon‐fiber‐reinforced polystyrene is examined by the CLSM and geometric parameters of fibers on each cross‐sectional plane are measured by an image analysis. In order to describe fiber orientation states compactly, orientation tensors are determined at different positions of the prepared specimen. Three‐dimensional orientation states are obtained without any difficulty by determining the out‐of‐plane angles utilizing fiber images on two parallel planes acquired by the CLSM. Orientation states are different at different positions and show the shell–core structure along the thickness of the specimen. Fiber orientation tensors are predicted by a numerical analysis and the numerically predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from the fountain flow effects, which are not considered in the numerical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 500–509, 2003 相似文献
27.
Bong Keun Kim Wan Kyun Chung 《Industrial Electronics, IEEE Transactions on》2003,50(6):1207-1216
Disturbance-observer (DOB)-based controller design is one of the most popular methods in the field of motion control. In this paper, the generalized disturbance compensation framework, named the robust internal-loop compensator (RIC) is introduced and an advanced design method of a DOB is proposed based on the RIC. The mixed sensitivity optimization problem, which is the main issue of DOB design, is also solved through the parametrization of the DOB in the RIC framework. Differently from conventional methods, the Q-filter is separated from the mixed sensitivity optimization problem and a systematic design law for the DOB is proposed. This guarantees the robustness and optimality of the DOB and enables the design for unstable plants. 相似文献
28.
Pi-Yu Chung Hajj I.N. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1997,5(2):233-237
This paper presents a technique to correct multiple logic design errors in a gate-level netlist. A number of methods have been proposed for correcting single logic design errors. However, the extension of these methods to more than one error is still very limited. We direct our attention to circuits with a low multiplicity of errors. By assuming different error dependency scenarios, multiple errors are corrected by repeatedly applying a single error search and correction algorithm. Experimental results on correcting double-design errors and triple-design errors on ISCAS and MCNC benchmark circuits are included 相似文献
29.
Ju D.-C.R. Chuan-Lin Wu Carini P. 《Parallel and Distributed Systems, IEEE Transactions on》1994,5(10):1113-1120
We present a classification scheme for array language primitives that quantifies the variation in parallelism and data locality that results from the fusion of any two primitives. We also present an algorithm based on this scheme that efficiently determines when it is beneficial to fuse any two primitives. Experimental results show that five LINPACK routines report 50% performance improvement from the fusion of array operators 相似文献
30.
O. Perat J. M. Dorkel E. Scheid P. Temple Boyer Y. S. Chung A. Peyre-Lavigne M. Zecri P. Tounsi 《Microelectronics Reliability》2002,42(7):1053-1058
Reliability of thermomechanical simulations is critically linked to the accuracy of the mechanical properties that govern the behaviour of structure, like Young's modulus (E) and coefficient of thermal expansion (CTE). For many cases, the values found in literatures are dealing with bulk properties without detailed information on temperature effects. To address such issues, it is necessary to measure the materials parameters as a function of temperature. The measurement of CTE is usually accomplished by evaluating the thermal deflections of a subjected material layer deposited on a substrate, providing that E is known at a specific temperature of experiment. A bilayer method, based on theory of elasticity, is proposed to determine both E and CTE for a given temperature with a good resolution. This paper presents the theoretical analysis, the design and process of the microsystem test structures, and the main calculation results. 相似文献