全文获取类型
收费全文 | 1218篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 16篇 |
综合类 | 4篇 |
化学工业 | 66篇 |
金属工艺 | 34篇 |
机械仪表 | 24篇 |
建筑科学 | 7篇 |
能源动力 | 8篇 |
轻工业 | 39篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 107篇 |
一般工业技术 | 97篇 |
冶金工业 | 751篇 |
原子能技术 | 6篇 |
自动化技术 | 76篇 |
出版年
2022年 | 9篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 11篇 |
2013年 | 32篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 22篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 13篇 |
2004年 | 12篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 41篇 |
1998年 | 242篇 |
1997年 | 156篇 |
1996年 | 99篇 |
1995年 | 40篇 |
1994年 | 53篇 |
1993年 | 38篇 |
1992年 | 7篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1977年 | 16篇 |
1976年 | 40篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有1240条查询结果,搜索用时 0 毫秒
1.
2.
HJ Lee HK Ha MH Kim YK Jeong PN Kim MG Lee JS Kim DJ Suh SG Lee YI Min YH Auh 《Canadian Metallurgical Quarterly》1997,169(2):517-520
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers. 相似文献
3.
4.
A chimeric dopamine transporter (DAT) cDNA encoding mutant human DAT (hDAT) protein in which the intracellular carboxyl-terminal tail is replaced by that of the bovine dopamine transporter (bDAT) was constructed. The chimeric hDAT cDNA was expressed in COS-7 cells, and [3H]dopamine and [3H]MPP+ uptake and [3H]CFT binding capacities were assessed. Substrate transport and ligand binding of bDAT were reduced by 32-43% as a result of substitution of the carboxyl tail in hDAT, suggesting that the functional characteristics of bDAT arise from differences in the carboxyl tail between human and bovine DAT. Thus, it appears that the sequences encoded within the carboxyl terminal of DAT would be one of the important determinants for its functions. 相似文献
5.
Juin-Hung Chen Hen-Wai Tsao 《Lightwave Technology, Journal of》1998,16(7):1137-1148
This paper presents a design method of optical frequency modulation (FM) subcarrier (with super carrier) transmission modem. The nonideal link characteristics, including laser chirping, fiber dispersion, voltage controlled oscillator (VCO) phase noise, relative intensity noise (RIN), and equivalent network model of laser diode of such a system that may bring about signal distortion are discussed first. We then propose a hierarchical methods to establish the system equivalent model. Finally this FM modem is applied to a GSM wireless system, in which multichannel signals are transmitted over fiber between radio port and basestation, and system performance is appraised by its dynamic range. It is found that optical FM subcarrier (with super carrier) transmission technique can improve the system dynamic range, compared with the intensity modulated direct detection (IMDD) method, and this is a economical and efficient method 相似文献
6.
MT Dorak HK Machulla M Hentschel KI Mills J Langner AK Burnett 《Canadian Metallurgical Quarterly》1996,65(2):134-139
Goodpasture syndrome is an often fatal autoimmune disease associated with glomerulonephritis and/or pulmonary hemorrhage. The clinical manifestations of this disease correlate well with the presence of circulating antiglomerular basement membrane (GBM) autoantibodies. The primary target antigen in glomerular and alveolar basement membranes is thought to be the alpha 3 chain of type IV collagen. Nearly all that is known about anti-GBM antibodies in humans comes from work on unbound circulating antibody. We recently had the unique and rare opportunity to obtain early postmortem antibody and tissues from a patient who died with catastrophic Goodpasture syndrome. The specificity of circulating, kidney-bound and lung-bound autoantibodies from this patient was evaluated against a variety of purified basement membrane constituents. The results indicate that the primary target for the circulating and tissue-bound autoantibodies is the NC1 domain of the alpha 3(IV) chain of type IV collagen. Additionally, all the antibodies recognize a cryptic epitope/s on the alpha 3(IV)NC1 hexamer. Furthermore, tissue-bound and circulating antibodies compete with one another for overlapping epitopes on the antigen. These findings demonstrate that circulating autoantibodies in Goodpasture syndrome are highly representative of those bound to organ tissues, strengthening the notion that pathogenic autoantibodies are targeted to the alpha 3(IV)NC1 collagen, and that previous reports of findings in the circulation may be applicable to tissue injury. 相似文献
7.
8.
Because of concerns among veterans over Agent Orange exposure, the Department of Veterans Affairs (VA) has conducted a series of studies of specific cancers among Vietnam veterans. Lung cancer is the topic of investigation in this report. The VA's Patient Treatment File (PTF) was used to identify 329 Vietnam era veterans with a diagnosis of lung cancer made between 1983 and 1990. The PTF is a computerized hospitalized database of inpatient records, including patients' demographic data, and diagnoses. A record is created for each patient discharged from any one of the VA's Medical Centers. Variables abstracted from the military record include education, race, branch of service, Military Occupational Specialty Code, rank, and units served within Vietnam. Two hundred sixty-nine controls were randomly selected from the PTF file of men hospitalized for a reason other than cancer. A second control group numbering 111 patients with colon cancer was also selected from the PTF file. Data were also gathered on exposure to Agent Orange through the location of each individual ground troop veteran's unit in relation to an area sprayed and the time elapsed since that area was sprayed. The crude odds ratio between service in Vietnam and lung cancer was of borderline significance (odds ratio = 1.39 with 95% confidence interval = 1.01-1.92). The relationship disappeared when the confounder year of birth was considered. We conclude from these data that there is no evidence of increased risk in lung cancer associated with service in Vietnam at this time. 相似文献
9.
10.
A nuclease activity has been purified from the nuclei-kinetoplast fraction of Leishmania. This enzyme, termed endonuclease M (Endo M), is shown by electrophoresis in a denaturing polyacrylamide gel to be associated with a single polypeptide of molecular mass 52 kDa. Physical analysis of the enzyme indicates that it has a sedimentation coefficient S20,w of 4.5S, a Stoke's radius of 32.5 A, and a native molecular mass of 53 kDa. The final Mono Q purified Endo M possesses both DNase and RNase activities. It acts as an endonuclease by introducing random single-stranded nicks into the supercoiled DNA molecules, that often leads to its linearization due to nicking at the opposite strands, and subsequent degradation of the DNA with further incubation. Single-stranded DNA is twice preferred to double-stranded DNA as substrate. Single-stranded RNA is also degraded rapidly and is competitive as a substrate with single-stranded DNA. RNA:DNA hybrids, however, are largely resistant to the Endo M digestion. 相似文献