全文获取类型
收费全文 | 2125篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
化学工业 | 151篇 |
金属工艺 | 64篇 |
机械仪表 | 21篇 |
建筑科学 | 67篇 |
矿业工程 | 2篇 |
能源动力 | 17篇 |
轻工业 | 110篇 |
水利工程 | 11篇 |
石油天然气 | 2篇 |
无线电 | 124篇 |
一般工业技术 | 179篇 |
冶金工业 | 1207篇 |
原子能技术 | 4篇 |
自动化技术 | 166篇 |
出版年
2022年 | 11篇 |
2021年 | 19篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2017年 | 17篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 52篇 |
2012年 | 40篇 |
2011年 | 54篇 |
2010年 | 29篇 |
2009年 | 27篇 |
2008年 | 42篇 |
2007年 | 48篇 |
2006年 | 38篇 |
2005年 | 32篇 |
2004年 | 25篇 |
2003年 | 38篇 |
2002年 | 30篇 |
2001年 | 26篇 |
2000年 | 31篇 |
1999年 | 46篇 |
1998年 | 304篇 |
1997年 | 188篇 |
1996年 | 116篇 |
1995年 | 82篇 |
1994年 | 70篇 |
1993年 | 70篇 |
1992年 | 21篇 |
1991年 | 17篇 |
1990年 | 42篇 |
1989年 | 27篇 |
1988年 | 28篇 |
1987年 | 20篇 |
1986年 | 36篇 |
1985年 | 34篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 31篇 |
1981年 | 36篇 |
1980年 | 41篇 |
1979年 | 21篇 |
1978年 | 18篇 |
1977年 | 38篇 |
1976年 | 85篇 |
1975年 | 18篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1968年 | 8篇 |
排序方式: 共有2138条查询结果,搜索用时 15 毫秒
1.
2.
V. Elliott Smith John M. Spurr John C. Filkins Jody J. Jones 《Journal of Great Lakes research》1985,11(3):231-246
Organochlorine analysis was performed on carcasses of 13 diving ducks from a 1981 wintering population that foraged on contaminated sediments in the lower Detroit River. Mean total PCB concentrations were 10 mg/kg for seven lesser scaups (Aythya affinis), 11 mg/kg for three greater scaups (A. marila), and 7.6 mg/kg for three goldeneyes (Bucephala clangula). Highest mean levels of other residues were measured for hexachlorobenzene (1.7 mg/kg) in goldeneyes, and transnonachlor (0.33 mg/kg) and 4,4’-DDE (1.3 mg/kg) in greater scaup. Quantitative analysis of 72 PCB congeners also was applied to water, seston, sediment, benthie oligochaetes, and carp from the same site. Principal congeners in most of the samples included some of the more toxic and persistent PCBs. Results of a multivariate analysis indicated that ratios of more conservative to less conservative PCBs did not vary significantly among ducks (α = .05), but differed from those in carp, oligochaetes, and sediment. For the February through March period of fat mobilization, concentrations of total PCB in lipid were inversely correlated with percent lipid (r = 0.76) in ducks. The percentage of conservative PCBs increased slightly. The distribution and partitioning of organochlorines, including toxic PCB congeners, varied considerably within this water column-sediment-fauna ecosystem. Estimates of toxic exposure based on total PCB values may be unreliable. 相似文献
3.
The viscometric, turbidimetric and potentiometric properties of copolymers of acrylamide (AM) with 2-acrylamido-2-methylpropanedimethylammonium chloride (AMPDAC) were studied in aqueous solutions. The AMPDAC polymers exhibit poor salt tolerance and large, negative viscosity/temperature coefficients. Furthermore, the polymers were found to be sensitive to changes in pH. The AMPDAC polymers undergo phase separation in the presence of dianions as a function of temperature and AMPDAC composition. 相似文献
4.
In this paper, the authors describe how the tragic events of 11 September 2001 have resulted in an urgent requirement for improved and enhanced security measures at airports, larger facilities and transportation networks. 相似文献
5.
Frank J.Elliott 《中国计算机用户》2003,(5):26-26
众所周知,在当前的企业信息系统中,一些新型的应用、无法预料的业务需求、加上信息传递和访问渠道的增多,使得企业需要存储的数据信息量呈爆炸性增长。应对这些问题,是一项艰巨而又昂贵的工作,尤其是存储及处理大量重要的商业信息。对于存储,很多信息系统决策者已经认识到了它的重要性。但是,高昂的花销却让决策者“瞻前顾后”、左右为难。如何才能制订一个最合适的规划呢?IBM存储产品部副总裁Frank J.Elliott为我们展示了他的分析。 相似文献
6.
BP Grubb D Samoil P Temesy-Armos H Hahn L Elliott 《Canadian Metallurgical Quarterly》1993,22(4):714-717
STUDY OBJECTIVE: To determine the potential feasibility of external cardiac pacing for the termination of sustained supraventricular tachycardia in the emergency department setting. TYPE OF PARTICIPANTS: Three men and two women (mean age, 34 years) who presented to the ED with a narrow-complex, hemodynamically stable tachycardia that was later proven to be supraventricular in origin. INTERVENTION: Each patient underwent external overdrive pacing using a modified external pacemaker at a pulse amplitude of 120 mA and a rate between 240 and 280 pulses per minute. RESULTS: In four patients, external cardiac pacing was able to successfully terminate the tachycardia without complication. In one patient, the pacemaker was not able to terminate the tachycardia. CONCLUSION: We conclude that external, noninvasive pacing is a feasible means of terminating supraventricular tachycardia in the ED setting. 相似文献
7.
8.
KC Dunn AD Marmorstein VL Bonilha E Rodriguez-Boulan F Giordano LM Hjelmeland 《Canadian Metallurgical Quarterly》1998,39(13):2744-2749
PURPOSE: To determine the polarity of fibroblast growth factor 5 (FGF5) secretions from retinal pigment epithelium (RPE) cells and to examine the viability and utility of the ARPE-19 cell line as a model for the study of RPE polarity. METHODS: Influenza infection and adenovirus-mediated gene transfer were used to deliver and express genes encoding influenza hemagglutinin (HA), p75-NTR (a neurotrophin receptor), low-density lipoprotein (LDL) receptor (LDLR), and FGF5 in confluent monolayers of ARPE-19 cells. The localization of HA, p75-NTR, and LDLR was determined by confocal microscopy. Domain selective biotinylation assays were used to quantitatively determine the polarities of p75-NTR and LDLR. The secretion of FGF5 into the apical and basal media of ARPE-19 cultures was examined by immunoblot analysis of conditioned media. RESULTS: Hemagglutinin and p75-NTR were found to be localized on the apical surface of infected and transduced ARPE-19 cells. In contrast, LDLR was associated preferentially with the basolateral membrane of ARPE-19 cells. Biotinylation studies indicated that 84% of p75-NTR was present on the apical surface, and 79% of LDLR was basolaterally polarized. Over the course of 6 hours, more than 90% of the total secreted FGF5 protein accumulated in the basolateral media. CONCLUSIONS: ARPE-19 cells exhibit a polarized distribution of cell surface markers when examined by either confocal microscopy or surface-labeling assays. This indicates that the ARPE-19 cell line is a valid model for studies of RPE cell polarity. FGF5, a secreted protein normally produced by RPE cells, is accumulated preferentially in the basal media after only 6 hours, suggesting that it is vectorially secreted from the basolateral surface of ARPE-19 cells. 相似文献
9.
10.
Discrete-Time Expectation Maximization Algorithms for Markov-Modulated Poisson Processes 总被引:1,自引:0,他引:1