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   201篇
  免费   8篇
  国内免费   1篇
电工技术   1篇
化学工业   28篇
金属工艺   5篇
机械仪表   2篇
建筑科学   7篇
能源动力   3篇
轻工业   21篇
水利工程   10篇
无线电   2篇
一般工业技术   24篇
冶金工业   77篇
原子能技术   4篇
自动化技术   26篇
  2023年   1篇
  2021年   5篇
  2020年   2篇
  2019年   3篇
  2018年   9篇
  2017年   6篇
  2016年   6篇
  2015年   4篇
  2014年   3篇
  2013年   9篇
  2012年   8篇
  2011年   20篇
  2010年   18篇
  2009年   8篇
  2008年   15篇
  2007年   11篇
  2006年   9篇
  2005年   7篇
  2004年   7篇
  2003年   4篇
  2002年   5篇
  2001年   5篇
  2000年   1篇
  1999年   4篇
  1998年   6篇
  1997年   5篇
  1996年   7篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1989年   1篇
  1986年   2篇
  1984年   1篇
  1983年   2篇
  1982年   5篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1974年   2篇
  1973年   1篇
排序方式: 共有210条查询结果,搜索用时 234 毫秒
1.
This field study examined applicant reactions (N = 802) toward face-to-face as compared with technology-mediated interviews (through videoconferencing or by telephone) for 346 organizations. Face-to-face interviews were perceived as more fair and led to higher job acceptance intentions than were videoconferencing and telephone interviews. Perceived interview outcomes were higher with face-to-face and telephone interviews over videoconferencing. Self-monitoring moderated the relationship between interview medium and perceptions of fairness. Specifically, this relationship was (a) positive for face-to-face, (b) negative for telephone, and (c) nonsignificant for videoconferencing interviews. Moreover, the number of offers an applicant received moderated the relationship between interview medium over, and perceived fairness. The relationship between number of offers and perceived fairness was positive for face-to-face and negative for technology-mediated interviews. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
2.
BACKGROUND: Accessory function (AF) is one way antigen presenting cells generate sufficient secondary signals for optimal T-cell proliferation and IL-2 production. In general, alveolar macrophages (AM) are inferior accessory cells in comparison to monocytes whereas in sarcoidosis AF of AM is increased. METHODS: We compared the accessory index (AI) of AM and peripheral blood monocytes (PBM) of 41 patients with inactive sarcoidosis (SAR I, n = 12); active sarcoidosis with new or progressing symptoms (SAR II, n = 19), active sarcoidosis with spontaneous remission (SAR III, n = 10), tuberculosis (TB, n = 12), hypersensitivity pneumonitis (HP, n = 12), Wegener's disease (WD, n = 2), undefined alveolitis (UA, n = 8) and chronic obstructive pulmonary disease (COPD, n = 6) by employing the histoincompatibility-insensitive Jurkat cells as indicator cells. RESULTS: Compared with the controls (1.08 +/- 0.3) AMs of all groups but SAR I (AI: 0.96 +/- 0.42) exhibited significantly increased AIs (SAR II: 3.6 +/- 3.9; SAR III: 3.2 +/- 2.4; TB: 2.8 +/- 2.2; HP: 3 +/- 2; UA: 2.7 +/- 2.3; COPD: 3.1 +/- 2.2; p < 0.05 for all comparisons). Only in HP, AI of PBM was significantly increased compared with controls (3 +/- 1.5, 1.3 +/- 0.5, respectively; p < 0.001). Alveolar macrophages from patients with arcoidosis, TB, and HB express the costimulatory molecule CD80 on their surface and anti-CD80 antibodies inhibited the IL-2 release of Jurkat cells in this system to 59 +/- 27%. CONCLUSIONS: Our data demonstrate that AM from patients with various diseases have the capability to act as competent accessory cells and that the reported accessory function of these cells is at least in part mediated by the expression of CD80.  相似文献   
3.
Introduction: Low‐grade chronic inflammation is common in hemodialysis (HD) patients. Previous studies suggest an anti‐inflammatory effect of angiotensin II receptor blocker (ARB) treatment. The aim of this study was to compare the effect of ARB vs. placebo on plasma concentrations of inflammatory markers in HD patients. Methods: Adult HD patients were randomized for double‐blind treatment with the ARB irbesartan 150–300 mg/day or placebo. At baseline, 1 week, 3, 6, 9, and 12 months plasma high sensitivity C‐reactive protein (hsCRP), interleukin (IL)?1β, IL‐6, IL‐8, IL‐18, and transforming growth factor‐β (TGF‐β) were measured using Luminex and enzyme‐linked immunosorbent assay (ELISA) technology. Findings: Eighty‐two patients were randomized (placebo/ARB: 41/41). The groups did not differ in initial levels of any of the inflammatory markers (placebo/ARB median(range)): hsCRP 3.3(0.2–23.4)/2.7(0.2–29.6) μg/mL; IL‐1β 1.1(0.0–45.9)/1.1(0.0‐7.2) pg/mL; IL‐6 10(1–90)/12(1–84) pg/mL; IL‐8 31(9–134)/34(5–192) pg/mL; IL‐18 364(188–1343)/377(213–832) pg/mL; TGF‐β 3.2(0.8–13.9)/3.6(1.3–3.8) ng/mL. Overall, there was no significant difference in hsCRP, IL‐6, IL‐8, and TGF‐β between placebo and ARB‐treated patients during the study period, and hsCRP, IL‐6, IL‐8, and TGF‐β were relatively stable during the study period (P ≥ 0.18 in all tests for parallel curves, equal levels, and constant levels). The IL‐1β level was slightly different in the two groups over time, but not significantly (P = 0.09 in test for parallel curves) and it was also relatively stable during the study period (P ≥ 0.49 in tests for equal levels and constant level). IL‐18 was the only inflammatory marker which was not constant during the study period (P = 0.001 in test for constant level), but there was no significant difference between placebo and ARB‐treated (P ≥ 0.51 in tests for parallel curves and equal levels). Discussion: Inflammatory biomarkers were neither acutely, nor in the long‐term significantly affected by the ARB irbesartan. Our findings suggest that ARB treatment in HD patients does not offer protective anti‐inflammatory effects.  相似文献   
4.
Introduction: Health related quality of life (HRQOL) is markedly reduced in hemodialysis patients compared to the general population. We investigated the course of self‐reported HRQOL over time and the association with selected factors, focusing on changes in glomerular filtration rate (GFR). Methods: Eighty‐two newly started hemodialysis patients from the SAFIR cohort filled out the Kidney Disease Quality of Life Short Form Version 1.3 (KDQOL‐SFTM) questionnaire at baseline, 6 and 12 months. The SAFIR study was a randomized, placebo‐controlled, double‐blind intervention study, examining the effects of the angiotensin II receptor blocker irbesartan. HRQOL was a secondary outcome measure. Main inclusion criteria: Dialysis vintage <1 year, left ventricular ejection fraction >30% and urinary output >300 mL/day. GFR was measured with mean creatinine and urea clearance from 24‐hour urine collections at baseline, 6 and 12 months. Findings: Irbesartan treatment did not affect HRQOL. Patients were pooled into one group for further analyses. Decline in GFR correlated significantly with decreasing HRQOL over time. HRQOL was stable over time, with a slight nonsignificant tendency toward improved HRQOL. The largest HRQOL‐differences (positive values equal improved HRQOL) observed during the 12 month study period were (mean[95% confidence interval]): Burden of kidney disease:6.4[?2.2;15.0], Role limitations‐physical:12.7[?2.1;27.5], and Role limitations‐emotional:9.7[?5.2;24.6]. Comorbidity, especially diabetes, hospital admissions, female gender, and age were strongly associated with lower HRQOL in cross sectional analysis. Discussion: Preservation of residual renal function seems to be important for HRQOL. In newly started HD patients, HRQOL showed little change after 12 months. HRQOL was negatively affected by comorbidity, especially diabetes, hospital admissions, female gender, and age.  相似文献   
5.
Energy coupled to matter (ECM) concepts such as magnetic field–assisted processing were used to align rare earth–doped alumina ceramics in the presence of applied fields. The addition of gadolinium and ytterbium dopants to alumina increased the magnetic susceptibility anisotropies, and induced magnetic torques that led to significant alignment of ceramic particles under the application of magnetic fields as low as 1.8?T. In comparison, undoped alumina materials showed minimal alignment under applied field strengths as high as 9?T. Density function theory modeling indicated that the specific dopant type dictated changes in the magnetic properties of different rare earth–doped alumina systems by directly affecting the magnetic moment localization and magnetocrystalline anisotropy.  相似文献   
6.
Some students (base group) played the Circuit Game, a 10-level computer-based learning activity intended to help students learn how electrical circuits work. Other students (competition group) played the same game but with competition features added - including a score bar showing performance on each level, the opportunity to earn one ticket per level if a performance criterion is met, and the opportunity to win a prize based on the number of tickets earned. On a retention test given after the game, the competition group remembered significantly more than the base group (d = 0.47). On an embedded transfer test constituting the final level of the game, the groups did not differ significantly. However, on the transfer test there was a significant gender by group interaction in which men performed worse in the competition group than the base group (d = −0.54) and women performed better in the competition group than the base group (d = 0.24). Overall, adding game-like features to a computer-based learning activity caused students to pay attention to game details but did not motivate students - particularly men - to learn more deeply.  相似文献   
7.
Well designed domain specific languages have three important benefits: (1) the easy expression of problems, (2) the application of domain specific optimizations (including parallelization), and (3) dramatic improvements in productivity for their users. In this paper we describe a compiler and parallel runtime system for modeling the complex kinetics of rubber vulcanization and olefin polymerization that achieves all of these goals. The compiler allows the development of a system of ordinary differential equations describing a complex vulcanization reaction or single-site olefin polymerization reaction—a task that used to require months—to be done in hours. A specialized common sub-expression elimination and other algebraic optimizations sufficiently simplify the complex machine generated code to allow it to be compiled—eliminating all but 8.0% of the operations in our largest program and enabling over 60 times faster execution on our largest benchmark codes. The parallel runtime and dynamic load balancing scheme enables fast simulations of the model.  相似文献   
8.
Cluster validity indices are used to validate results of clustering and to find a set of clusters that best fits natural partitions for given data set. Most of the previous validity indices have been considerably dependent on the number of data objects in clusters, on cluster centroids and on average values. They have a tendency to ignore small clusters and clusters with low density. Two cluster validity indices are proposed for efficient validation of partitions containing clusters that widely differ in sizes and densities. The first proposed index exploits a compactness measure and a separation measure, and the second index is based an overlap measure and a separation measure. The compactness and the overlap measures are calculated from few data objects of a cluster while the separation measure uses all data objects. The compactness measure is calculated only from data objects of a cluster that are far enough away from the cluster centroids, while the overlap measure is calculated from data objects that are enough near to one or more other clusters. A good partition is expected to have low degree of overlap and a larger separation distance and compactness. The maximum value of the ratio of compactness to separation and the minimum value of the ratio of overlap to separation indicate the optimal partition. Testing of both proposed indices on some artificial and three well-known real data sets showed the effectiveness and reliability of the proposed indices.  相似文献   
9.
Rats with hippocampal or sham lesions were trained to find food on a T maze located at 2 positions. Response rats were required to make a right or left turn. Direction rats were required to go in a consistent direction (east or west). Place rats were required to go to a consistent location, relative to room cues. One place group had distinguishable start points at the 2 maze positions, whereas another place group had start points facing the same side of the room. Controls took longer to solve a place problem than the response and direction problems when the start points were not distinguishable. Rats with hippocampal lesions were not different than controls on the response problem but were impaired on the direction and place problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
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