全文获取类型
收费全文 | 24587篇 |
免费 | 2650篇 |
国内免费 | 1795篇 |
专业分类
电工技术 | 2064篇 |
综合类 | 2583篇 |
化学工业 | 2860篇 |
金属工艺 | 1461篇 |
机械仪表 | 1678篇 |
建筑科学 | 1686篇 |
矿业工程 | 944篇 |
能源动力 | 757篇 |
轻工业 | 2582篇 |
水利工程 | 842篇 |
石油天然气 | 702篇 |
武器工业 | 408篇 |
无线电 | 2645篇 |
一般工业技术 | 1939篇 |
冶金工业 | 2243篇 |
原子能技术 | 323篇 |
自动化技术 | 3315篇 |
出版年
2024年 | 154篇 |
2023年 | 359篇 |
2022年 | 950篇 |
2021年 | 1178篇 |
2020年 | 850篇 |
2019年 | 616篇 |
2018年 | 664篇 |
2017年 | 731篇 |
2016年 | 670篇 |
2015年 | 1042篇 |
2014年 | 1302篇 |
2013年 | 1566篇 |
2012年 | 1922篇 |
2011年 | 1935篇 |
2010年 | 2003篇 |
2009年 | 1787篇 |
2008年 | 1853篇 |
2007年 | 1798篇 |
2006年 | 1534篇 |
2005年 | 1213篇 |
2004年 | 862篇 |
2003年 | 585篇 |
2002年 | 506篇 |
2001年 | 549篇 |
2000年 | 380篇 |
1999年 | 180篇 |
1998年 | 441篇 |
1997年 | 249篇 |
1996年 | 189篇 |
1995年 | 99篇 |
1994年 | 86篇 |
1993年 | 100篇 |
1992年 | 41篇 |
1991年 | 40篇 |
1990年 | 38篇 |
1989年 | 46篇 |
1988年 | 33篇 |
1987年 | 34篇 |
1986年 | 24篇 |
1985年 | 30篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 24篇 |
1978年 | 21篇 |
1977年 | 50篇 |
1976年 | 85篇 |
1975年 | 16篇 |
1971年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
论述了参数设计法在铝电解电容器设计开发阶段的应用。文中阐明了铝电解电容器的主要质量特性(损耗因子、电容量)及芯包外径的参数设计原理,并建立了归一化函数作为优选设计方案的判据。实例证明在铝电解电容器的设计过程中应用参数设计法以减小产品质量特性变异是有效的。 相似文献
22.
Allen Daniel N.; Strauss Gregory P.; Kemtes Karen A.; Goldstein Gerald 《Canadian Metallurgical Quarterly》2007,21(6):713
Hemispheric involvement in reasoning abilities has been debated for some time, and it remains unclear whether the right hemisphere's involvement in problem solving is modality specific or dependent on the type of spatial reasoning required. In the current study, 2 types of nonverbal reasoning abilities were examined, spatial reasoning and proportional reasoning, in 109 patients with cerebrovascular disease that was confined to either the right or the left hemisphere or was diffuse in nature. Results indicated that no lateralizing effects were present based on type of spatial reasoning. Findings are consistent with the suggestion that higher order cognitive processes involved in nonverbal abstraction and problem solving are not strongly lateralized to the right hemisphere but rather are more generally distributed throughout the cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
P Brouqui HT Dupont M Drancourt Y Berland J Etienne C Leport F Goldstein P Massip M Micoud A Bertrand 《Canadian Metallurgical Quarterly》1993,153(5):642-648
OBJECTIVE: Chronic Q fever is seldom recognized; before 1989, only 234 cases had been reported in the literature. The 92 cases of chronic Q fever collected at the French National Reference Center for Rickettsioses from 1982 through 1990 represent the largest series ever reported. PATIENTS: The patients included in the study were diagnosed between July 31, 1982, and August 1, 1990, at the French National Reference Center for Rickettsioses as having chronic Q fever by the following criteria: presence of antibody against Coxiella burnetii phase I antigen at a titer greater than or equal to 800 for IgG and 50 for IgA by the indirect immunofluorescence test. Epidemiologic, clinical, laboratory, and treatment data were collected from 39 different collaborative hospitals throughout France. MAIN OUTCOME MEASURE: For each serologically selected patient, a computerized questionnaire was utilized to record 188 different items of demographic, epidemiologic, clinical, laboratory, and therapeutic data, which were analyzed. RESULTS: Chronic Q fever occurs more frequently in city dwellers than in rural inhabitants, and exposure to domestic ruminants and raw milk is an important feature. Immunocompromising conditions (20.2%) and underlying heart disease (88.4%) or vascular disease are the most important risk factors to consider in potential cases of chronic Q fever. The mortality in these patients with endocarditis was high (23.5%). The clinical spectrum of 84 patients included 57 cases of endocarditis, three cases of vascular prosthesis infection, three cases of aneurysmal infection, three cases of osteoarthritis, four cases with lung localizations, nine asymptomatic cases, three cases of hepatitis, and two cases with cutaneous forms of the disease. CONCLUSIONS: In patients with unexplained fever, negative blood cultures, and a history of underlying vascular or cardiac disease, Q fever should be considered. 相似文献
24.
S Hunt Gerardo DM Citron MC Claros EJ Goldstein 《Canadian Metallurgical Quarterly》1996,40(10):2413-2415
When the Etest was compared to broth microdilution for susceptibility testing of Streptococcus pneumoniae, levofloxacin, erythromycin, and penicillin results correlated for both methods; azithromycin and clarithromycin showed discrepancies of > or = 2 dilutions for 95.8% and 31.5% of the isolates, respectively. Levofloxacin was active against 141 of 142 isolates (< or = 2.0 micrograms/ml), making it a potentially useful new fluoroquinolone. 相似文献
25.
26.
27.
The major goal of this investigation was to collect statistically-based anthropometry describing the kinematics of the human hand and to model this anthropometry as a function of external hand measurements, so that it may be predicted noninvasively. Joint centres were anatomically estimated as the centre of curvature of the head of the bone proximal to the given joint. Joint centres determined using Reuleaux's method for PIP and DIP were within 1.4 mm of this anatomical estimate. Models using bone length as the independent variable explain more than 97% of the variability in the anatomically estimated joint centre position along the mid-line of the bone. Models for estimating the lengths of the kinematic segments using external hand length as the independent variable account for between 49 and 99% of the variability in segment length. Models for estimating the axial location of the finger MCP and thumb CMC joints with respect to the distal wrist crease using external hand length as the independent variable account for between 82 and 96% of the variability in these locations. Models for estimating the radio-ulnar location of the finger MCP and thumb CMC joints with respect to the long axis of the third metacarpal using external hand breadth as the independent variable account for between 30 and 74% of the variability in these locations. 相似文献
28.
29.
30.
东莞市水污染现状及其对策探讨 总被引:2,自引:0,他引:2
通过分析东莞市河流、水库、饮用水源地、河库底质污染现状以及1998-2003年部分河道水质变化趋势,找出本地区水污染问题和原因,提出改善水环境的对策措施。 相似文献