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   5658篇
  免费   176篇
  国内免费   4篇
电工技术   69篇
综合类   8篇
化学工业   1031篇
金属工艺   190篇
机械仪表   90篇
建筑科学   238篇
矿业工程   33篇
能源动力   98篇
轻工业   543篇
水利工程   35篇
石油天然气   8篇
无线电   483篇
一般工业技术   762篇
冶金工业   1652篇
原子能技术   56篇
自动化技术   542篇
  2022年   42篇
  2021年   70篇
  2020年   64篇
  2019年   65篇
  2018年   95篇
  2017年   78篇
  2016年   116篇
  2015年   78篇
  2014年   113篇
  2013年   161篇
  2012年   164篇
  2011年   215篇
  2010年   175篇
  2009年   162篇
  2008年   191篇
  2007年   191篇
  2006年   169篇
  2005年   181篇
  2004年   132篇
  2003年   115篇
  2002年   126篇
  2001年   137篇
  2000年   113篇
  1999年   109篇
  1998年   436篇
  1997年   265篇
  1996年   193篇
  1995年   165篇
  1994年   125篇
  1993年   142篇
  1992年   82篇
  1991年   76篇
  1990年   74篇
  1989年   72篇
  1988年   61篇
  1987年   62篇
  1986年   52篇
  1985年   67篇
  1984年   53篇
  1983年   58篇
  1982年   60篇
  1981年   46篇
  1980年   49篇
  1979年   61篇
  1978年   35篇
  1977年   62篇
  1976年   116篇
  1975年   55篇
  1974年   32篇
  1972年   33篇
排序方式: 共有5838条查询结果,搜索用时 15 毫秒
51.
In a comprehensive literature study applied measurement methods for determination of the specific electrical conductivity of slags were compared. Based on these conclusions, a Tammann furnace was modified to a conductivity measuring system with four electrodes. A qualitative and quantitative comparison of results from literature with the practical results of multiple investigations of CaF2 slags with a purity of 99.5% was carried out.  相似文献   
52.
The relationship of depressed mood to cognitive disturbance in HIV infection was examined in a sample of 139 homosexual men. Ss were grouped according to the classification of the Centers for Disease Control: 39 were in Group IV, 62 were in Group II or Group III, and 38 were HIV-negative. Ss completed the Profile of Mood States and 10 neuropsychological tests. Analysis employing a classification approach indicated that, although symptoms of depression and neuropsychological impairment were more common in Ss who were HIV-positive, particularly those classified as Group IV, there were no systematic relationships between depression and neuropsychological impairment. Depressed mood and cognitive disturbance each seem to have unique associations to HIV illness status. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
53.
54.
Four actuarial instruments for the prediction of violent and sexual reoffending (the Violence Risk Appraisal Guide [VRAG], Sex Offender Risk Appraisal Guide [SORAG], Rapid Risk Assessment for Sex Offender Recidivism [RRASOR], and Static-99) were evaluated in 4 samples of sex offenders (N = 396). Although all 4 instruments predicted violent (including sexual) recidivism and recidivism known to be sexually motivated, areas under the receiver operating characteristic (ROC) were consistently higher for the VRAG and the SORAG. The instruments performed better when there were fewer missing items and follow-up time was fixed, with an ROC area up to .84 for the VRAG, for example, under such favorable conditions. Predictive accuracy was higher for child molesters than for rapists, especially for the Static-99 and the RRASOR. Consistent with past research, survival analyses revealed that those offenders high in both psychopathy and sexual deviance were an especially high-risk group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
55.
56.
57.
Summary Recent progress in the modelling of exchanged Cu sites and their interactions with small molecules, based on DFT cluster calculations, is briefly reviewed.  相似文献   
58.
OBJECTIVE: To identify possible causes for the increased cardiovascular morbidity and mortality seen in patients with primary hyperparathyroidism. DESIGN: Prospective, blind study. SETTING: University hospital, Sweden. SUBJECTS: 44 Patients with primary hyperparathyroidism and 23 (sex and age matched) control patients with atoxic nodular goitres. INTERVENTIONS: Exploration of the neck with removal of pathological parathyroid glands or thyroid resection. Echocardiography before, and one year after, the operation. MAIN OUTCOME MEASURES: Blood pressure and echocardiographic findings. RESULTS: Hyperparathyroid patients had higher blood pressure and greater left atrial diameter than control patients preoperatively. They also had a significantly lower E:A ratio (mitral flow velocity pattern) than the controls (p = 0.02) indicating a disturbance in early diastolic filling of the left ventricle. The E:A ratio correlated negatively with the systolic blood pressure. 19 of the hyperparathyroid patients (43%) had cardiac calcifications as did 14 (61%) of the controls. Most of calcifications were located in the aortic and mitral valves; only a few patients had calcifications in the myocardium. No significant changes had occurred one year after parathyroidectomy, except for a reduction in systolic blood pressure, in the hyperparathyroid patients. CONCLUSION: Echocardiographic investigation of patients with primary hyperparathyroidism shows early signs of left ventricular dysfunction that may be of clinical importance.  相似文献   
59.
60.
The relative populations and transverse relaxation times of the solid-like hydrogen pool (PB and T2B) and the magnetization transfer (MT) rates between the solid-like and liquid-like hydrogen pools (kappa) have been determined for three different agar gel concentrations (2%, 4%, and 8% by weight) as well as excised fibroglandular breast tissue specimens. PB was determined to be .003(.001), .01(.002), .02(.01), and .06(.01); T2B was determined to be 13.0(.2), 14.0(.1), 14.5(.1) and 15.2(1.3) microseconds; and kappa was determined to be 0.78(.01), 1.15(.02), 2.00(.02), and 3.55(1.5) sec-1 for the 2%, 4%, and 8% agar gels and the fibroglandular tissue, respectively. The image signal intensities of a pulsed MTC-prepared gradient-echo imaging technique are predicted using these MT parameters and are shown to agree well with experimental data obtained from a clinical MR imaging system. This technique is shown to suppress signal intensity of fibroglandular breast tissue by 40%-50% without exceeding SAR limits (< or = 8 W/kg) and is helpful for visualizing lesions and silicone implants.  相似文献   
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