全文获取类型
收费全文 | 10158篇 |
免费 | 61篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 47篇 |
化学工业 | 409篇 |
金属工艺 | 70篇 |
机械仪表 | 58篇 |
建筑科学 | 124篇 |
矿业工程 | 15篇 |
能源动力 | 43篇 |
轻工业 | 299篇 |
水利工程 | 29篇 |
石油天然气 | 9篇 |
无线电 | 299篇 |
一般工业技术 | 461篇 |
冶金工业 | 7937篇 |
原子能技术 | 20篇 |
自动化技术 | 404篇 |
出版年
2021年 | 29篇 |
2019年 | 20篇 |
2018年 | 25篇 |
2017年 | 32篇 |
2016年 | 17篇 |
2015年 | 32篇 |
2014年 | 59篇 |
2013年 | 150篇 |
2012年 | 103篇 |
2011年 | 101篇 |
2010年 | 57篇 |
2009年 | 62篇 |
2008年 | 89篇 |
2007年 | 109篇 |
2006年 | 106篇 |
2005年 | 74篇 |
2004年 | 84篇 |
2003年 | 95篇 |
2002年 | 75篇 |
2001年 | 57篇 |
2000年 | 58篇 |
1999年 | 302篇 |
1998年 | 2652篇 |
1997年 | 1497篇 |
1996年 | 950篇 |
1995年 | 521篇 |
1994年 | 408篇 |
1993年 | 510篇 |
1992年 | 91篇 |
1991年 | 95篇 |
1990年 | 103篇 |
1989年 | 96篇 |
1988年 | 106篇 |
1987年 | 91篇 |
1986年 | 91篇 |
1985年 | 88篇 |
1984年 | 29篇 |
1983年 | 40篇 |
1982年 | 48篇 |
1981年 | 73篇 |
1980年 | 97篇 |
1979年 | 30篇 |
1978年 | 41篇 |
1977年 | 191篇 |
1976年 | 344篇 |
1975年 | 39篇 |
1974年 | 23篇 |
1973年 | 29篇 |
1972年 | 19篇 |
1971年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zenan Yu Julian Moore Jean Calderon Lei Zhai Jayan Thomas 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(39):5289-5295
Cable‐shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable‐shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable‐shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil‐type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical‐electrochemical stability. The CASECs show excellent charge–discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm−3), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets. 相似文献
2.
3.
4.
The aim of this study was to assess the association between the length of maternity leave and the quality of mother-infant interactions; 198 employed mothers of 4-month-old infants were interviewed and videotaped in their homes during a feeding time. Hierarchical multiple regression analyses indicated a direct association between shorter length of leave and more negative affect and behavior in maternal interactions with their infants. Infant and mother stressor/protective variables added significantly in predicting the quality of the mother-infant relationship. There were also significant interaction effects between the length of leave and these variables. Mothers who either reported more depressive symptoms or who perceived their infant as having a more difficult temperament and who had shorter leaves, compared with mothers who had longer leaves, were observed to express less positive affect, sensitivity, and responsiveness in interactions with their infants. The public policy implications of the relation between length of maternity leave, maternal and infant individual differences, and the quality of mother-infant interactions are discussed. 相似文献
5.
A case of traumatic extracranial vertebral arterial dissection leading to vertebrobasilar thrombosis and respiratory compromise requiring mechanical ventilation was managed with intraarterial thrombolysis and stenting of the vertebral intimal dissection. In contrast to similar, previously reported cases, this critically ill patient made a full recovery, returning to his job as a secondary school teacher. 相似文献
6.
Gastric bacteria from cheetahs with gastritis were used to inoculate specific-pathogen free kittens and conventional mice. Helicobacter sp. and Gastrospirillum sp. colonized kittens, while only Gastrospirillum sp. colonized mice. In kittens, both bacterial species induced mild lymphofolliclar gastritis which did not change over the course of the 11 months observation period. In mice, Gastrospirillum sp. induced lymphoplasmacytic and follicular gastritis which increased in severity over 6 months and persisted for the 12 month observation period. Gastric ulcers and gastric mucosal hypertrophy were present in chronically infected mice. These results indicate that host but not bacterial factors influence the severity of gastritis, and that in mice, bacterial gastritis increases in severity with time and may lead to gastric ulceration in some individuals. 相似文献
7.
8.
MA Molina MJ Romero E Abril I Delgado RM Cano F Garrido JM de Pablos ML Garrido 《Canadian Metallurgical Quarterly》1994,39(4):253-256
INTRODUCTION: Heterozygous beta-thalassemia manifests hematologically with microcytosis, reduced red blood cell hemoglobin concentration and high hemoglobin A2 levels. Almost all molecular alterations are due to point mutations. We attempt to determinate the frequency of that mutations in the Oriental Andalusia Area, and its relationship with the hematological phenotype. PATIENTS AND METHODS: We have studied 45 heterozygous patients. DNA samples were amplified by PCR, using the printers CD7 and HI1. A 16 Kb fragment corresponding to beta globin gene was obtained and analyzed by Dot Blot assay and hybridized with allelic specific oligonucleotide (ASO) probes to detect the 6 more frequent mutations found in the South of Spain. RESULTS: Codon 39 nonsense mutation (31.1%) was the most frequent finding followed by IVS-1 NT 110 (26.7%). The relationship between hematological parameters and molecular mutations concluded that IVS-I NT 6 mutation developed a minimal anemia. DISCUSSION: From the practical point of view, this study indicates that we were able to detect more than 90% of heterozygous beta-tal. with 5 out of 6 ASO probes used in this work. Thus, our data also provides a further implication in prenatal diagnosis. 相似文献
9.
MJ Weiss 《Canadian Metallurgical Quarterly》1997,11(6):1185-1198
Two advances in murine embryonic stem (ES) cell technology and their applications for the study of hematopoietic stem cells (HSCs) are discussed in this article. First, ES cells induced to differentiate in vitro form hematopoietic lineages in a fashion that recapitulates the ontogeny of blood formation in the embryo. This system offers a unique opportunity to isolate, examine, and manipulate the most primitive hematopoietic progenitors. Second, targeted gene ablation (knockout) studies in ES cells have identified several genes that are required for normal hematopoiesis and may function in the formation, maintenance, and differentiation of HSCs. Insights into murine hematopoiesis gained through the study of ES cells generally should be applicable to other vertebrates, including humans. 相似文献
10.
NC Moore 《Canadian Metallurgical Quarterly》1997,86(2):81-82
The nation's health care system is undergoing a period of rapid change that will profoundly affect women's health care services and, ultimately, women's health. Although managed care is quickly becoming the predominant mode of health care delivery in the United States, a new, more consumer-focused, and accountable model known as organized systems of care (OSC) is emerging. OSC development has been driven by large private and public employers seeking to purchase the highest quality health care for the best price. The changes in health care delivery encouraged by these innovative employers will provide women with optimal care and attention, which will in turn help them attract and retain a competitive and productive workforce. 相似文献