全文获取类型
收费全文 | 1490篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 17篇 |
综合类 | 2篇 |
化学工业 | 118篇 |
金属工艺 | 16篇 |
机械仪表 | 15篇 |
建筑科学 | 35篇 |
矿业工程 | 3篇 |
能源动力 | 25篇 |
轻工业 | 88篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 85篇 |
一般工业技术 | 126篇 |
冶金工业 | 861篇 |
原子能技术 | 13篇 |
自动化技术 | 102篇 |
出版年
2022年 | 5篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 16篇 |
2016年 | 14篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 25篇 |
2012年 | 20篇 |
2011年 | 29篇 |
2010年 | 11篇 |
2009年 | 20篇 |
2008年 | 38篇 |
2007年 | 27篇 |
2006年 | 19篇 |
2005年 | 38篇 |
2004年 | 26篇 |
2003年 | 17篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 43篇 |
1998年 | 250篇 |
1997年 | 143篇 |
1996年 | 121篇 |
1995年 | 68篇 |
1994年 | 58篇 |
1993年 | 62篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 28篇 |
1987年 | 23篇 |
1986年 | 22篇 |
1985年 | 21篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 23篇 |
1976年 | 34篇 |
1973年 | 7篇 |
1972年 | 7篇 |
1970年 | 6篇 |
1967年 | 4篇 |
排序方式: 共有1511条查询结果,搜索用时 0 毫秒
71.
This paper presents a biography of Hertha Ayrton, celebrated as the first woman member of the IEE. The author writes that this feat should not obscure her many other achievements 相似文献
72.
PURPOSE: To determine if lucanthone crossed the blood-brain barrier in experimental animals; and to determine accelerated tumor regression of human brain metastases treated jointly with lucanthone and whole brain radiation. METHODS AND MATERIALS: The organ distribution of 3H lucanthone in mice and 125I lucanthone in rats was determined to learn if lucanthone crossed the blood-brain barrier. Size determinations were made of patients' brain metastases from magnetic resonance images or by computed tomography before and after treatment with 30 Gy whole brain radiation alone or with lucanthone. RESULTS: The time course of lucanthone's distribution in brain was identical to that in muscle and heart after intraperitoneal or intravenous administration in experimental animals. Lucanthone, therefore, readily crossed the blood-brain barrier in experimental animals. CONCLUSION: Compared with radiation alone, the tumor regression in patients with brain metastases treated with lucanthone and radiation was accelerated, approaching significance using a permutation test at p = 0.0536. 相似文献
73.
S Sharir MA Jewett JF Sturgeon M Moore PR Warde CN Catton MK Gospodarowicz 《Canadian Metallurgical Quarterly》1999,161(2):472-5; discussion 475-6
PURPOSE: To optimize followup in patients with stage I nonseminomatous testis cancer on surveillance we evaluated the contribution of each followup modality to the detection of progression as well as morbidity and mortality outcomes. MATERIALS AND METHODS: After orchiectomy 170 patients with clinical stage I nonseminoma were prospectively placed on a surveillance protocol. History, physical examination, serum tumor markers, abdominal and pelvic computerized tomography (CT), and chest x-ray were used for followup. The number of failures, methods and timing of progression detection, treatments required, mortality rate and subsequent contralateral primary tumors were recorded. RESULTS: The 170 surveillance patients were followed a median of 6.3 years. Within 2 years (median 6.9 months) postoperatively 48 patients (28.2%) had disease progression. History, physical examination, markers, CT and chest radiography provided the initial evidence of progression in 18 (37.5%), 34 (70.8%), 34 (70.8%), and 4 (8.3%) patients, respectively. Each modality was the only indicator of failure in 2 (4.2%), 4 (8.3%), 10 (20.8%) and 0 cases, respectively. Of the 170 patients 122 (71.8%) required no additional treatment beyond orchiectomy, 26 (15.3%) received 1 and 22 (12.9%) underwent more than 1 therapeutic modality. Only 1 patient (0.6%) died of disease. Contralateral tumors developed in 5 cases (2.9%) therapeutic a mean of 8.1 years after orchiectomy. CONCLUSIONS: In stage I nonseminoma patients, surveillance history, physical examination, tumor markers and abdominopelvic CT are necessary components of the followup protocol. Removal of routine chest x-ray from the protocol would not have changed progression detection. The initial surveillance visit must occur by 2 months postoperatively. Patients should be followed beyond 5 years and likely for life in addition to regular patient self-examination. 相似文献
74.
75.
76.
X-ray computed tomography (CT) is used to explore the differences in gas dispersion in a stirred-tank reactor (STR) for different operating conditions by varying the impeller speed and gas flow rate. X-ray imaging has been carried out in a 0.21 m ID acrylic STR equipped with a nylon Rushton-type impeller. From the CT images, major differences in local gas holdup are observed for different operating conditions. Completely dispersed conditions have a relatively uniform holdup profile while flooded conditions show a high gas holdup near the impeller shaft. The high resolution of the X-ray system allowed fine details such as recirculation regions behind the baffles to be visualized. 相似文献
77.
Argues that G. S. Howard and C. G. Conway (see record 1987-07162-001) have not achieved their aim of demonstrating a new methodology for elucidating the nature and effects of volition but have remained prisoners of the philosophy of determinant science. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
This article presents findings from an empirical study investigating the transfer of rhetorical knowledge, defined as audience awareness, sense of purpose, organization, use of visuals, professional appearance, and style, between the technical communication and the engineering disciplines. Various data collection methods were used to examine the skills and rhetorical knowledge students learned in a technical communication course and determine whether or not students relied on that knowledge as they completed writing assignments in an engineering course. Also examined was the effect of workplace experiences on shaping students' rhetorical knowledge. This study indicated that students did appear to transfer rhetorical strategies between different contexts, and those strategies were learned in the workplace as well as the classroom. 相似文献
79.
The years of the great depression were marked with unemployment and economic ruin for many people. Americans were left feeling helpless and hopeless. After the 1932 presidential election of Franklin Roosevelt, his administration embarked on a course of government known as the New Deal. Many new and innovative programs were established to create jobs and a sense of hope for the public. This article will examine four programs that were of particular interest to nursing: the Federal Emergency Relief Act, the Civil Works Act, the Works Progress Act, and the Social Security Act. Nurses of the time embraced these programs. They participated in their development and implementation and made a difference in the lives of many desperate Americans. 相似文献
80.
Desorption electrospray ionization (DESI) was demonstrated as a means to couple thin-layer chromatography (TLC) with mass spectrometry. The experimental setup and its optimization are described. Development lanes were scanned by moving the TLC plate under computer control while directing the stationary DESI emitter charged droplet plume at the TLC plate surface. Mass spectral data were recorded in either selected reaction monitoring mode or in full scan ion trap mode using a hybrid triple quadrupole linear ion trap mass spectrometer. Fundamentals and practical applications of the technique were demonstrated in positive ion mode using selected reaction monitoring detection of rhodamine dyes separated on hydrophobic reversed-phase C8 plates and reversed-phase C2 plates, in negative ion full scan mode using a selection of FD&C dyes separated on a wettable reversed-phase C18 plate, and in positive ion full scan mode using a mixture of aspirin, acetaminophen, and caffeine from an over-the-counter pain medication separated on a normal-phase silica gel plate. 相似文献