全文获取类型
收费全文 | 8657篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 268篇 |
金属工艺 | 49篇 |
机械仪表 | 36篇 |
建筑科学 | 121篇 |
矿业工程 | 7篇 |
能源动力 | 67篇 |
轻工业 | 207篇 |
水利工程 | 14篇 |
石油天然气 | 13篇 |
无线电 | 175篇 |
一般工业技术 | 378篇 |
冶金工业 | 7089篇 |
原子能技术 | 13篇 |
自动化技术 | 234篇 |
出版年
2022年 | 14篇 |
2021年 | 13篇 |
2019年 | 19篇 |
2018年 | 13篇 |
2017年 | 22篇 |
2015年 | 20篇 |
2014年 | 24篇 |
2013年 | 115篇 |
2012年 | 55篇 |
2011年 | 86篇 |
2010年 | 72篇 |
2009年 | 60篇 |
2008年 | 72篇 |
2007年 | 80篇 |
2006年 | 68篇 |
2005年 | 75篇 |
2004年 | 69篇 |
2003年 | 58篇 |
2002年 | 42篇 |
2001年 | 49篇 |
2000年 | 46篇 |
1999年 | 230篇 |
1998年 | 2232篇 |
1997年 | 1247篇 |
1996年 | 808篇 |
1995年 | 442篇 |
1994年 | 400篇 |
1993年 | 447篇 |
1992年 | 77篇 |
1991年 | 115篇 |
1990年 | 88篇 |
1989年 | 97篇 |
1988年 | 97篇 |
1987年 | 105篇 |
1986年 | 94篇 |
1985年 | 92篇 |
1984年 | 24篇 |
1983年 | 26篇 |
1982年 | 58篇 |
1981年 | 68篇 |
1980年 | 56篇 |
1979年 | 26篇 |
1978年 | 41篇 |
1977年 | 195篇 |
1976年 | 377篇 |
1975年 | 29篇 |
1974年 | 13篇 |
1973年 | 19篇 |
1972年 | 14篇 |
1968年 | 13篇 |
排序方式: 共有8690条查询结果,搜索用时 0 毫秒
1.
2.
Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented 相似文献
3.
S. F. Edwards 《Polymer International》1985,17(2):122-125
Elasticity is discussed as an aspect of viscoelasticity, which is described by the tube model. The effects of both crosslinks and entanglements contribute to this model and a discussion of how these effects can be quantified is given. At high enough concentration, entanglements ensure the existence of elastic effects even without crosslinks, and a theory is presented on how this dynamical phase change comes about. 相似文献
4.
5.
The authors highlight several possible ways in which the construction industry could lower present emissions of the greenhouse gas, carbon dioxide. It is an excellent discussion document and is recommended reading. 相似文献
6.
JW DiFiore DO Fauza R Slavin CA Peters JC Fackler JM Wilson 《Canadian Metallurgical Quarterly》1994,29(2):248-56; discussion 256-7
Infants with congenital diaphragmatic hernia (DH) and profound pulmonary hypoplasia are currently unsalvageable. The authors previously demonstrated that tracheal ligation (TL) accelerates fetal lung growth and reverses the pulmonary hypoplasia of fetal nephrectomy. The purpose of this study was to determine if the pulmonary hypoplasia of experimental DH could be similarly reversed and, if so, whether the resulting lungs would show better function than those of their DH counterparts. Eighteen fetal lambs were divided into three experimental groups of six animals each. In group 1, DH was created at 90 days' gestation. In group 2, DH was created at 90 days' gestation and TL performed during the same operation. Group 3 consisted of sham-operated controls. These animals were delivered near full-term, and their lungs analyzed by standard morphometric techniques. Ten additional fetal lambs were divided into two experimental groups of five animals each. In group 4, DH was created at 90 days' gestation. In group 5, DH was created at 90 days' gestation and TL performed 20 days later, at 110 days' gestation. These animals were pressure-ventilated via tracheostomy over a 2-hour period in which PaO2, PaCO2, and compliance were measured. Intratracheal pressure (ITP) was measured at the time of delivery in all groups. Upon retrieval, DH animals had abdominal viscera in the chest and small lungs; in contrast, DH/TL animals had the herniated viscera reduced from the chest by enlarged lungs. DH/TL lungs showed markedly increased growth, with significant increases in lung volume:body weight ratio (LV:BW; P = .0001), alveolar surface area (ALV.SA; P = .0001), and alveolar number (ALV#) (P = .0001) when compared with those of the DH or control group. This growth was associated with a normal maturation pattern based on histological appearance, normal airspace fraction, and normal alveolar numerical density. ITP in the DH/TL group was increased when compared with that of DH and control animals (P = .0001). Total lung DNA and protein were both elevated in the DH/TL animals (P = .0001). However, the DNA:protein ratio remained normal, suggesting lung growth had occurred through cell proliferation, not by hypertrophy. When ventilated over a range of settings, DH/TL lungs were more compliant (P = .0001) and achieved higher PaO2s (P < .003) and lower PaCO2s (P = .0001) than their DH counterparts. From these data, the authors conclude: (1) Experimental fetal DH produces hypoplastic lungs that are not capable of adequate gas exchange with conventional ventilation.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
7.
RA Kilani P Hmiel MK Garver SK Srinathan KM Wickline JC Langer 《Canadian Metallurgical Quarterly》1996,31(10):1427-1429
Although jejunal atresia occasionally may occur with a familial pattern, an association with renal disease has not been described. The authors report on three family members treated over two generations, all of whom had both proximal jejunal atresia and renal dysplasia. This association was most likely inherited as an autosomal dominant trait. 相似文献
8.
This paper presents the results of laboratory measurements of relative permeability for two phase flow in partially saturated samples of unconsolidated sands. Relative permeabilities for tap water and air, de-aired water and nitrogen were measured using a steady—state technique. Three different sand samples (fine sand, heterogeneous sand and coarse sand) were tested. 相似文献
9.
L D''Hondt C Chatelain C Doyen JC Osselaer A Ferrant A Bosly 《Canadian Metallurgical Quarterly》1996,38(4):353-354
We report the case of a young patient with refractory acute lymphoblastic leukemia relapse, after allogeneic bone marrow transplantation, who was treated by donor leukocyte infusions. We observed potent adoptive immunotherapy which produced a cytologic complete remission and total chimeric state. This was of short duration and the patient died of severe graft-versus-host disease. We present a short summary of the literature concerning acute lymphoblastic leukemia and donor leukocyte infusions. 相似文献
10.
Three different fully implantable venous access devices were randomly inserted in 72 patients. Comparison both from the point of view of their ease of insertion and their later use failed to show any significant difference between the three systems. 相似文献