全文获取类型
收费全文 | 4473篇 |
免费 | 123篇 |
国内免费 | 87篇 |
专业分类
电工技术 | 52篇 |
综合类 | 123篇 |
化学工业 | 240篇 |
金属工艺 | 130篇 |
机械仪表 | 99篇 |
建筑科学 | 256篇 |
矿业工程 | 27篇 |
能源动力 | 31篇 |
轻工业 | 166篇 |
水利工程 | 45篇 |
石油天然气 | 38篇 |
武器工业 | 24篇 |
无线电 | 213篇 |
一般工业技术 | 379篇 |
冶金工业 | 2617篇 |
原子能技术 | 31篇 |
自动化技术 | 212篇 |
出版年
2023年 | 14篇 |
2022年 | 51篇 |
2021年 | 56篇 |
2020年 | 40篇 |
2019年 | 45篇 |
2018年 | 41篇 |
2017年 | 46篇 |
2016年 | 38篇 |
2015年 | 56篇 |
2014年 | 58篇 |
2013年 | 100篇 |
2012年 | 117篇 |
2011年 | 125篇 |
2010年 | 117篇 |
2009年 | 102篇 |
2008年 | 98篇 |
2007年 | 124篇 |
2006年 | 134篇 |
2005年 | 101篇 |
2004年 | 85篇 |
2003年 | 68篇 |
2002年 | 73篇 |
2001年 | 55篇 |
2000年 | 49篇 |
1999年 | 122篇 |
1998年 | 776篇 |
1997年 | 485篇 |
1996年 | 318篇 |
1995年 | 194篇 |
1994年 | 164篇 |
1993年 | 199篇 |
1992年 | 35篇 |
1991年 | 41篇 |
1990年 | 41篇 |
1989年 | 50篇 |
1988年 | 39篇 |
1987年 | 37篇 |
1986年 | 30篇 |
1985年 | 32篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1978年 | 10篇 |
1977年 | 67篇 |
1976年 | 146篇 |
1975年 | 10篇 |
1974年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有4683条查询结果,搜索用时 664 毫秒
1.
2.
BA Elliott 《Canadian Metallurgical Quarterly》1993,20(2):277-288
Primary care physicians can easily incorporate efforts toward the primary and secondary prevention of family violence into their practices. By designing a preventive effort using the phases of the family life cycle, a developmentally appropriate system of prevention is created. The anticipatory guidance at each (annual) visit acknowledges family transitions and assures the family that abuse is a health issue and that the physician is a resource for issues of violence prevention. Using the FLC, the first phase is Coupling, when there is a risk of partner violence that continues as long as there is a partnership. Pregnancy and childbirth bring concerns of child neglect and battery. Older children are at additional risk for child sexual abuse. As families age, risks develop for elder abuse, too. The regular discussion of these issues raises the awareness that the potential for family violence continues over the life span and allows the physician opportunities to assess the risk of violence in that family and make appropriate preventive referrals. Primary care physicians are optimally positioned to address violence and its prevention in the office: they know and care for family units over time. Physicians are respected and trusted advisors who can become effective in preventing violence. 相似文献
3.
4.
Turner S.E. Elder R.B. Jr. Jansen D.S. Kotecki D.E. 《Microwave and Wireless Components Letters, IEEE》2005,15(3):144-146
A 41-GHz 4-b adder-accumulator test circuit implemented in InP double heterojunction bipolar transistor (DHBT) technology using 624 transistors is reported. High clock rates are obtained by combining the logic functions into pipelined latches. The adder-accumulator contains a single-level parallel-gated carry circuit that is used as a step toward reduced power consumption. The carry circuit has a maximum clock frequency of 55 GHz. The accumulator architecture employs modular, pipelined 2-b adders and is cascadable to 2 N-bits. The test circuit includes a 4-b digital to analog converter (DAC) that facilitates demonstration of high-speed operation. 相似文献
5.
E Persson M Ljunggren J la Cour Jansen R Strube L J?nsson 《Water science and technology》2006,53(12):139-147
A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis. 相似文献
6.
7.
8.
MJ de Gortari BA Freking SM Kappes KA Leymaster AM Crawford RT Stone CW Beattie 《Canadian Metallurgical Quarterly》1997,28(4):274-290
We report the evaluation of 1036 bovine microsatellite primer pairs for their suitability as linkage markers in sheep. Approximately 58% (605/1036) of bovine primer pairs amplified a locus in sheep. Sixty-seven per cent (409/605) of amplified loci were detected as polymorphic. Marker heterozygosity, allele number and range of allele sizes were significantly lower in sheep than cattle sampled in this study. However, median fragment size was similar. These data suggest that high-resolution comparative linkage maps between closely related species can be constructed relatively efficiently. 相似文献
9.
The Chiari type II malformation is the leading cause of death in infants with myelomeningocele. The authors report 17 cases of symptomatic Chiari type II malformation occurring in two distinct age dependent population. In Group I, 13 neonates and infants in the first year of life presented with cranial nerve and brain stem dysfunction characterized by vocal cord paralysis, apnea, dysphagia and laryngeal stridor. In Group II, 4 patients developed signs and symptoms after the first year of life. In this group, the presentation was more insidious and included neck pain and cerebellar manifestations. The surgical treatment consisted initially in shunt implantation or revision and when there was no improvement, posterior fossa decompression was performed. The response to the surgical treatment differed considerably between the two groups: older patients improved promptly after surgery and there was no casualties; in newborn and infants, especially those under 6 months of age, the mortality rate was 46.1%. The authors stress that prompt diagnosis and surgical intervention should be performed in order to produce a favorable outcome. 相似文献
10.
SW D'Souza E Rivlin J Cadman B Richards P Buck BA Lieberman 《Canadian Metallurgical Quarterly》1997,76(2):F70-F74
AIMS: To compare the outcome in in vitro fertilisation (IVF) children (after fresh embryo transfer) from multiple and singleton births with one another, and with normally conceived control children. METHODS: A cohort of 278 children (150 singletons, 100 twins, 24 triplets and four quadruplets), conceived by IVF after three fresh embryos had been transferred, born between October 1984 and December 1991, and 278 normally conceived control children (all singletons), were followed up for four years after birth. They were assessed for neonatal conditions, minor congenital anomalies, major congenital malformations, cerebral palsy and other disabilities. Control children, all born at term, were matched for age, sex and social class. RESULTS: The ratio of male:female births was 1.03. Forty six per cent of IVF children were from multiple births; 34.9% were from preterm deliveries; and 43.2% weighed less than 2500 g at birth. The IVF singletons were on average born one week earlier than the controls, weighed 400 g less, and had a threefold greater chance of being born by caesarean section. The higher percentage of preterm deliveries was largely due to multiple births and they contributed to neonatal conditions in 45.0% of all IVF children. The types of congenital abnormalities varied: 3.6% of IVF children and 2.5% of controls had minor congenital anomalies, and 2.5% of IVF children and none of the controls had major congenital malformations. The numbers of each specific type of congenital abnormality were small and were not significantly related to multiple births. IVF children (2.1%) and 0.4% of the controls had mild/moderate disabilities. They were all from multiple births, including two children with cerebral palsy who were triplets. CONCLUSIONS: The outcome of IVF treatment leading to multiple births is less satisfactory than that in singletons because of neonatal conditions associated with preterm delivery and disabilities in later childhood. A reduction of multiple pregnancies by limiting the transfer of embryos to two instead of three remains a high priority. 相似文献