全文获取类型
收费全文 | 3840篇 |
免费 | 53篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 14篇 |
综合类 | 2篇 |
化学工业 | 237篇 |
金属工艺 | 29篇 |
机械仪表 | 40篇 |
建筑科学 | 78篇 |
矿业工程 | 4篇 |
能源动力 | 25篇 |
轻工业 | 165篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
武器工业 | 2篇 |
无线电 | 99篇 |
一般工业技术 | 250篇 |
冶金工业 | 2742篇 |
原子能技术 | 5篇 |
自动化技术 | 195篇 |
出版年
2022年 | 17篇 |
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 20篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 41篇 |
2013年 | 68篇 |
2012年 | 39篇 |
2011年 | 66篇 |
2010年 | 52篇 |
2009年 | 50篇 |
2008年 | 69篇 |
2007年 | 66篇 |
2006年 | 44篇 |
2005年 | 45篇 |
2004年 | 43篇 |
2003年 | 43篇 |
2002年 | 34篇 |
2001年 | 28篇 |
2000年 | 29篇 |
1999年 | 114篇 |
1998年 | 823篇 |
1997年 | 524篇 |
1996年 | 339篇 |
1995年 | 185篇 |
1994年 | 147篇 |
1993年 | 190篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 38篇 |
1989年 | 29篇 |
1988年 | 30篇 |
1987年 | 33篇 |
1986年 | 36篇 |
1985年 | 27篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 26篇 |
1980年 | 36篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 73篇 |
1976年 | 141篇 |
1975年 | 10篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有3898条查询结果,搜索用时 31 毫秒
1.
2.
P. Richards I. Duncan C. Phipps G. Pickering J. Grzywacz R. Hoult J. Merritt 《Journal of Petroleum Geology》2006,29(3):199-214
Four basins surround the Falkland Islands, but only the North Falkland Basin has been drilled; six wells were drilled there in 1998. Although all six wells encountered good quality sandstones, none of them targeted the basin margins, on what are now thought to be the optimum migration pathways associated with the basin's thick lacustrine source rocks. Subsequently, a 3D seismic survey acquired in 2004 was designed to identify potential basin-margin -derived sandstones entering the basin along transfer zones. From this survey, a number of basin-margin -attached fans have been identified; these prograded into lacustrine waters of varying depths. These Early Cretaceous alluvial/fan delta/deep-lacustrine fan systems are interpreted to provide excellent potential reservoir facies as they are intimately associated with thick, mature source rocks. They will provide the focus for the next planned phase of exploration in the North Falkland Basin.
A phase of drilling is also planned for the basins to the south of the Islands, where large deltaic and fan systems, slightly younger than those imaged in the North Falkland Basin, are seen on seismic to prograde from the same Palaeozoic hinterland that produced the older, North Falkland Basin fans.
This paper attempts to show how sedimentary models derived from targeted seismic programmes following initial exploration can be utilised to plan and improve new drilling campaigns in a frontier basin. It presents an analysis of sediment dispersal patterns in basins of marine and lacustrine origin linked to a single hinterland area, and highlights the nature of the relationship between relay ramp/transfer zone development and sediment dispersal patterns in the subsurface. 相似文献
A phase of drilling is also planned for the basins to the south of the Islands, where large deltaic and fan systems, slightly younger than those imaged in the North Falkland Basin, are seen on seismic to prograde from the same Palaeozoic hinterland that produced the older, North Falkland Basin fans.
This paper attempts to show how sedimentary models derived from targeted seismic programmes following initial exploration can be utilised to plan and improve new drilling campaigns in a frontier basin. It presents an analysis of sediment dispersal patterns in basins of marine and lacustrine origin linked to a single hinterland area, and highlights the nature of the relationship between relay ramp/transfer zone development and sediment dispersal patterns in the subsurface. 相似文献
3.
In this study, the effect and side-effect of epidural injection with lappaconitine compound for post-operative analgesia was observed. One hundred and twenty patients were randomly divided into 4 groups. Lappaconitine compound (LB) consisted of 12 mg of lappaconitine and 22.5 mg of bupivacaine, was given to group A (the group of observation), and lappaconitine 12 mg, bupivacaine 22.5 mg and morphine 2 mg to group B, C and D respectively for control. All were given by epidural injection with single blind method during post-operative pain of incision operation. Result showed that the initiating of analgesia was quicker in group A and C than that in group B and D, and the efficacy was group D > A > C > B. There was significant difference between group A and B in the above two parameters, P < 0.01 and P < 0.05. The analgisia maintenence time of single injection was D > A > B > C, that of group D was significantly longer than that of group A (P < 0.01). It indicated that the epidural injection with LB was more rapid and potent than that with lappaconitine alone in post-operative analgesia, and the former had no side-effect, it was safer than morphine. 相似文献
4.
A side effect of therapy with procainamide and numerous other medications is a lupus-like syndrome characterized by autoantibodies directed against denatured DNA and the (H2A-H2B)-DNA subunit of chromatin. We tested the possibility that an effect of lupus-inducing drugs on central T cell tolerance underlies these phenomena. Two intrathymic injections of procainamide-hydroxylamine (PAHA), a reactive metabolite of procainamide, resulted in prompt production of IgM antidenatured DNA antibodies in C57BL/6xDBA/2 F1 mice. Subsequently, IgG antichromatin antibodies began to appear in the serum 3 wk after the second injection and were sustained for several months. Specificity, inhibition and blocking studies demonstrated that the PAHA-induced antibodies showed remarkable specificity to the (H2A-H2B)-DNA complex. No evidence for polyclonal B cell activation could be detected based on enumeration of Ig-secreting B cells and serum Ig levels, suggesting that a clonally restricted autoimmune response was induced by intrathymic PAHA. The IgG isotype of the antichromatin antibodies indicated involvement of T cell help, and proliferative responses of splenocytes to oligonucleosomes increased up to 100-fold. As little as 5 microM PAHA led to a 10-fold T cell proliferative response to chromatin in short term organ culture of neonatal thymi. We suggest that PAHA interferes with self-tolerance mechanisms accompanying T cell maturation in the thymus, resulting in the emergence of chromatin-reactive T cells followed by humoral autoimmunity. 相似文献
5.
6.
MG McInnis A Chakravarti J Blaschak MB Petersen V Sharma D Avramopoulos JL Blouin U K?nig C Brahe TC Matise 《Canadian Metallurgical Quarterly》1993,16(3):562-571
A genetic linkage map of human chromosome 21q (HC21q) containing 43 markers genotyped by the polymerase chain reaction in the CEPH pedigrees is presented. The markers placed on this map are highly polymorphic with an average heterozygosity of 61%. The average interval size of the markers localized at 1000:1 odds is 2.5 cM. The map has a total length of 65.5 cM, with male and female lengths of 47.7 and 83.3 cM, respectively. The genotypes used in the construction of this map were subjected to rigorous error checking, which is reflected in the shorter map length compared to previous maps; the estimated error rate in genotyping is less than 0.04%. As noted in previous linkage maps there is increased recombination in females on proximal HC 21q and in the male in a region near the telomere. This map of HC 21 represents a highly informative and dense meiotic linkage map and will be useful in linking disease phenotypes to loci on this chromosome. 相似文献
7.
8.
9.
10.
MG Newman 《Canadian Metallurgical Quarterly》1997,2(1):180-198
The design and implementation of clinical trials (CTs) carried out to evaluate antimicrobial and anti-infective drugs and devices are one of the most difficult challenges in contemporary periodontal research and product development. The overwhelming amount of evidence which has established a microbial etiology for periodontitis is the basis for developing and testing antimicrobial treatments. Well-designed antimicrobial CTs start with a carefully crafted hypothesis and a protocol which explicitly integrates the requirements of the patient, the clinician, the sponsor, and regulatory authorities. Surrogate variables for effectiveness must be clinically relevant, scientifically sound, and statistically valid. Currently, clinical attachment level measurements and alveolar bone assessments are accepted as proof of effectiveness. Indication and claim support of the antimicrobial product guide the design and implementation of the CT. Adverse microbiologic consequences, such as lack of antimicrobial susceptibility, wrong spectrum, incorrect dosage, non-compliance, and drug interference, must be monitored. Successful CTs balance a large group of variables used to screen, randomize, and assign subjects to experimental and control groups to ensure that prognostic and risk factors are properly accounted for. 相似文献