全文获取类型
收费全文 | 3498篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
综合类 | 2篇 |
化学工业 | 151篇 |
金属工艺 | 25篇 |
机械仪表 | 36篇 |
建筑科学 | 49篇 |
矿业工程 | 5篇 |
能源动力 | 30篇 |
轻工业 | 99篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 127篇 |
一般工业技术 | 164篇 |
冶金工业 | 2673篇 |
原子能技术 | 25篇 |
自动化技术 | 116篇 |
出版年
2021年 | 6篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 22篇 |
2015年 | 7篇 |
2014年 | 20篇 |
2013年 | 54篇 |
2012年 | 33篇 |
2011年 | 39篇 |
2010年 | 27篇 |
2009年 | 29篇 |
2008年 | 38篇 |
2007年 | 27篇 |
2006年 | 32篇 |
2005年 | 20篇 |
2004年 | 21篇 |
2003年 | 30篇 |
2002年 | 26篇 |
2001年 | 30篇 |
2000年 | 20篇 |
1999年 | 96篇 |
1998年 | 863篇 |
1997年 | 497篇 |
1996年 | 299篇 |
1995年 | 179篇 |
1994年 | 154篇 |
1993年 | 176篇 |
1992年 | 47篇 |
1991年 | 49篇 |
1990年 | 49篇 |
1989年 | 47篇 |
1988年 | 45篇 |
1987年 | 53篇 |
1986年 | 25篇 |
1985年 | 49篇 |
1984年 | 20篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 27篇 |
1980年 | 27篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 58篇 |
1976年 | 120篇 |
1975年 | 15篇 |
1974年 | 6篇 |
1972年 | 8篇 |
1970年 | 6篇 |
1969年 | 4篇 |
1968年 | 5篇 |
排序方式: 共有3528条查询结果,搜索用时 203 毫秒
991.
GE Wyatt KA Desmond PA Ganz JH Rowland K Ashing-Giwa BE Meyerowitz 《Canadian Metallurgical Quarterly》1998,4(4):385-405
This study examines ethnic differences in sexual socialization and attitudes, sexual history and current practices, and the effects of treatment in 147 African American and White breast cancer survivors. Sex-related research in younger healthy populations has shown that cultural values associated with ethnicity influence sexual functioning, but small numbers of African American participants in previous research in breast cancer survivors has limited what we know about that population. In this study, there were few differences between the 2 ethnic groups in a predominantly well-educated, high-income, highly functional sample. However, African American women were significantly less likely to be comfortable with and to practice oral sex, self-touching, and masturbatory behaviors. White women were more likely to report that breast cancer had a negative impact on their sex lives. These differences in sexual repertoire and functioning should be noted by health care practitioners treating the sexual sequelae of breast cancer treatment. 相似文献
992.
BACKGROUND: Patients with functional dyspepsia often experience early satiety and discomfort after a meal. The role of early gastric emptying in symptom generation is not known. Our aim was to relate timing of symptoms and early postprandial emptying in functional dyspepsia. METHODS: Twelve patients with functional dyspepsia were investigated during 3 min of fasting, during 3 min of ingesting 500 ml of a meat soup, and during the first 10 min postprandially by means of duplex sonography. RESULTS: Gastric emptying commenced on average 52 sec after the start of ingestion. Transpyloric movements of gastric contents unrelated to peristalsis (that is, alternating transpyloric emptying and reflux within a common chamber created by the terminal antrum, the pylorus, and the duodenal bulb) appeared before peristaltic-related emptying, which commenced after on average 116 sec. In all patients epigastric, meal-related discomfort was experienced after the commencement of transpyloric emptying, on average after 143 sec. A negative correlation was found between intensity of fullness and duration of presymptomatic transpyloric movements of gastric contents (that is, the duodenal 'tasting' period). CONCLUSIONS: The early occurrence of meal-related symptoms suggests that gastric distension is the main factor in symptom generation. However, the onset of symptoms after the commencement of gastric emptying suggests that intestinal tasting receptors are involved in symptom generation. The inverse relationship between the duration of the tasting period and symptom intensity suggests that the time allowed for duodenal tasting might be too short in patients with FD. 相似文献
993.
CL Luongo KA Dryden DL Farsetta RL Margraf TF Severson NH Olson BN Fields TS Baker ML Nibert 《Canadian Metallurgical Quarterly》1997,71(10):8035-8040
The 144-kDa lambda2 protein is a structural component of mammalian reovirus particles and contains the guanylyltransferase activity involved in adding 5' caps to reovirus mRNAs. After incubation of reovirus T3D core particles at 52 degrees C, the lambda2 protein became sensitive to partial protease degradation. Sequential treatments with heat and chymotrypsin caused degradation of a C-terminal portion of lambda2, leaving a 120K core-associated fragment. The four other proteins in cores--lambda1, lambda3, mu2, and sigma2--were not affected by the treatment. Purified cores with cleaved lambda2 were subjected to transmission cryoelectron microscopy and image reconstruction. Reconstruction analysis demonstrated that a distinctive outer region of lambda2 was missing from the modified cores. The degraded region of lambda2 corresponded to the one that contacts the base of the sigma1 protein fiber in reovirus virions and infectious subvirion particles, suggesting that the sigma1-binding region of lambda2 is near its C terminus. Cores with cleaved lambda2 were shown to retain all activities required to transcribe and cap reovirus mRNAs, indicating that the C-terminal region of lambda2 is dispensable for those functions. 相似文献
994.
995.
996.
997.
ES Avetisov A Alazme TP Kashchenko IL Smol''ianinova KA Mats NI Lokhtina 《Canadian Metallurgical Quarterly》1994,110(1):13-16
In Europe patients are increasingly entering the healthcare debate, demanding explanations and questioning medical practice and clinical nursing traditions, at a time when human and financial resources are short and the relevancy of standard setting and quality assurance activities are being questioned. Working on heavily loaded units, nurses may feel tempted to dismiss the need for systematic evaluation of their work. However, quality assurance may be the way to empower nurses, but only if done collectively. 相似文献
998.
RA Perez-Tamayo MP Anstadt RL Cothran RJ Reisinger DI Schenkman C Hulette KA Reimer GL Anstadt JE Lowe 《Canadian Metallurgical Quarterly》1995,41(3):M512-M517
Direct mechanical ventricular actuation (DMVA) is a unique, non blood contacting method for biventricular cardiac assist. Although DMVA has successfully provided cardiac assist for more than 7 days in humans, with long-term survival, its potential for long-term circulatory support has not been adequately investigated. DMVA has not been studied in the large ruminants commonly used to evaluate support devices. To develop a large animal experimental model of prolonged total circulatory support using DMVA, Suffolk sheep (n = 10) underwent sterile instrumentation for hemodynamic and chemistry monitoring. After baseline values were obtained, a left lateral thoracotomy and pericardotomy were performed. Upon electrical ventricular fibrillation (VF), DMVA was begun and the thoracotomy closed. Total circulatory support was continued until mean arterial pressure (MAP) persisted below 50% of the baseline value for more than 1 hr, with a goal of 7 days' support. Mean duration (plus or minus the standard deviation [SD]) of circulatory support was 65.9 +/- 56.8 hr (range, 10-168 hr). Pressors were not used during DMVA support. The subject supported for the maximal time (7 days) was defibrillated into sinus rhythm. No CK-MB fraction was greater than 1%, suggesting that DMVA, even with prolonged application during VF, does not result in myocardial injury. Blood urea nitrogen and creatinine levels indicate renal function was preserved. The model described represents the longest period any animal has been supported in VF using DMVA. This new model will be useful in determining what limitations, if any, exist to the prolonged use of DMVA for circulatory support. 相似文献
999.
Michael L Popovich Joseph M Henderson John Stinn 《IEEE engineering in medicine and biology magazine》2002,21(5):48-55
For over 20 years, our nation's public health system has continually struggled to combat ongoing and emerging public health threats and emergencies. Deadly threats have created considerable interest among healthcare providers, public health officials, state and local politicians, the Congress, and the President. As a consequence, substantial funding has been made available to federal, state, and local public health agencies to build a stronger, more vigilant public health system. Significant investment is being made to develop local and regional public health response plans, create robust information systems to support exchange of critical data and information, improve workforce competencies, and enhance communication systems needed to inform responders, the healthcare community, and the public. To succeed, public health agencies need a sophisticated and proven information technology framework that can be effectively applied to improve public health readiness. This article provides insight into the development of that framework, an integrated disease surveillance system for rapid detection, tracking, and managing of public health threats, within the context of the overall public health system 相似文献
1000.