全文获取类型
收费全文 | 1744篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 23篇 |
综合类 | 3篇 |
化学工业 | 107篇 |
金属工艺 | 46篇 |
机械仪表 | 7篇 |
建筑科学 | 61篇 |
矿业工程 | 4篇 |
能源动力 | 33篇 |
轻工业 | 104篇 |
水利工程 | 8篇 |
石油天然气 | 4篇 |
无线电 | 108篇 |
一般工业技术 | 223篇 |
冶金工业 | 858篇 |
原子能技术 | 11篇 |
自动化技术 | 167篇 |
出版年
2021年 | 13篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 17篇 |
2014年 | 18篇 |
2013年 | 58篇 |
2012年 | 25篇 |
2011年 | 39篇 |
2010年 | 28篇 |
2009年 | 27篇 |
2008年 | 40篇 |
2007年 | 48篇 |
2006年 | 41篇 |
2005年 | 37篇 |
2004年 | 51篇 |
2003年 | 33篇 |
2002年 | 36篇 |
2001年 | 44篇 |
2000年 | 28篇 |
1999年 | 47篇 |
1998年 | 247篇 |
1997年 | 144篇 |
1996年 | 107篇 |
1995年 | 69篇 |
1994年 | 48篇 |
1993年 | 50篇 |
1992年 | 27篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 30篇 |
1988年 | 26篇 |
1987年 | 15篇 |
1986年 | 25篇 |
1985年 | 27篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 28篇 |
1976年 | 49篇 |
1975年 | 12篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 5篇 |
排序方式: 共有1767条查询结果,搜索用时 15 毫秒
31.
M Patel RF Kaltenbach DA Nugiel RJ McHugh PK Jadhav LT Bacheler BC Cordova RM Klabe S Erickson-Viitanen S Garber C Reid SP Seitz 《Canadian Metallurgical Quarterly》1998,8(9):1077-1082
Cyclic urea SD146, a potent HIV protease inhibitor bearing a flat resistance profile, possessed poor solubility and bioavailability, which precluded further development of the compound. In an effort to improve upon the pharmacokinetic profile of the compound, several analogs modified at the P1/P1' residues were prepared and evaluated. Several of those compounds displayed significant improvement of physical properties. 相似文献
32.
RJ O''Hara J Greenman PJ Drew AW McDonald GS Duthie PW Lee JR Monson 《Canadian Metallurgical Quarterly》1998,41(4):460-463
OBJECTIVE: Spontaneous spinal epidural hematoma (SSEH) is an idiopathic accumulation of blood in the vertebral epidural space without identifiable predisposing factors. First reported in 1869, the clinical outcome in children younger than 18 years old has not been clearly delineated. DESIGN: A comprehensive review of the English language literature revealed 26 patients younger than 18 years old with reported clinical outcomes. The 27th case is presented. RESULTS: Complete neurologic recovery occurred in 14 of 27 (52%) patients, partial recovery in 12 of 27 (44%) patients, and death in 1 of 27 (4%) patients. CONCLUSION: There is an overall good prognosis for neurologic recovery in children who experience SSEH. 相似文献
33.
CM McDonald 《Canadian Metallurgical Quarterly》1998,9(1):9-48
This article has reviewed the clinical approach to the diagnostic evaluation of progressive neuromuscular diseases with an emphasis on relevant neuromuscular history, family history, clinical examination findings, laboratory studies, and a brief discussion of the role of muscle biopsy. Molecular genetic and immunocytochemistry studies of muscle have been major advances in the diagnostic evaluation of the neuromuscular disease patient; however, all diagnostic information must be interpreted within the context of relevant clinical information. In some instances, a precise diagnosis is not medically possible; however, the accurate characterization of an individual patient within the most appropriate NMD clinical syndrome often allows the clinician to provide the patient and family with accurate prognostic information and anticipatory guidance for the future. After synthesizing all available clinical and diagnostic information, the physiatrist or neurologist may at times determine that an NMD patient has an inappropriate diagnosis warranting further diagnostic evaluation. This issue focuses on the rehabilitation of progressive neuromuscular diseases with an emphasis on optimization of health, prevention or minimization of complications, and enhancement of quality of life. Appropriate rehabilitation approaches require an accurate diagnosis. In addition, patient quality of life in NMD depends on access to current and accurate information. The first step in providing accurate information and appropriate treatment is constantly ensuring that NMD patients have appropriate diagnoses based on a through evaluation of clinical information and appropriate application of current medical science and available diagnostic technology. 相似文献
34.
T Putilina C Jaworski S Gentleman B McDonald M Kadiri P Wong 《Canadian Metallurgical Quarterly》1998,252(2):433-439
A unique clone, isolated from a human pancreatic cDNA library, was sequenced and characterized. Northern blot analysis showed that the gene is active in a number of fetal and adult tissues, and immunoblots showed expression in nuclear and cytosolic cell fractions. The gene corresponding to the clone was localized to chromosome 13 by human/rodent somatic cell hybrid panels. The largest open reading frame contains a LIM domain, and the deduced peptide from the open reading frame appears to have the characteristics of a LIM-only protein, designated LMO7. RT-PCR and genomic sequence analyses indicate that expression of this gene product is subject to tissue-specific modulation by elimination of the LIM domain by alternative splicing in neural tissues. 相似文献
35.
X Chen DJ Kempf HL Sham BE Green A Molla M Korneyeva S Vasavanonda NE Wideburg A Saldivar KC Marsh E McDonald DW Norbeck 《Canadian Metallurgical Quarterly》1998,8(24):3531-3536
The 2-isopropyl thiazolyl group is a highly optimized P3 ligand for C2 symmetry-based HIV protease inhibitors, as exemplified in the drug ritonavir. Here we report that incorporation of this P3 ligand into a piperazine hydroxyethylamine series also yielded novel, highly potent inhibitors. In tissue culture assays, the presence of human serum was less deleterious to the activity of these inhibitors than to that of ritonavir. Furthermore, potent activity against ritonavir resistant HIV was observed. 相似文献
36.
N-acetyltransferase (NAT) activity was determined by incubation of purified Enterobacter aerogenes enzyme with 2-aminofluorene (2-AF) as the substrate, followed by high pressure liquid chromatography assays. The NAT activity from E. aerogenes was 0.58 +/- 0.08 nmol/min/mg protein for 2-AF. The values of apparent K(m) and Vmax were 0.72 +/- 0.14 mM and 2.45 +/- 0.29 nmol/min/mg protein, respectively, for 2-AF. The optimal pH value for the enzyme activity was 7.5 for the 2-AF tested. The optimal temperature for enzyme activity was 37 degrees C for the 2-AF substrate. The molecular weight of NAT from E. aerogenes was 44.9 kD. Among a series of divalent cations and salts, Zn2+, Ca2+, and Fe2+ were demonstrated to be the most potent protease inhibitors, and only ethylenediaminetetraacetic acid significantly protected the NAT. Iodoacetamide, in contrast to other agents, markedly inhibited NAT. 相似文献
37.
Peanut skin, when treated with formaldehyde to polymerize tannins, is a highly efficient substrate for removal of many heavy metal ions from aqueous waste solutions. The ions Ag1+, Cd2+, Cr6+, Cu2+, Hg2+, Ni2+, Pb2+, Zn2+, as well as Ca2+ and Mg2+, were contacted with formaldehyde-treated peanut skin. Quantitative removal could be achieved with Ag1+, Cd2+, Cu2+, Hg2+, Pb2+, and Zn2+. Capacity of the substrate for ions was promising for Pb2+ (2.1 meq/g substrate), Cu2+ (3.0 meq/g), and Cd2+ (1.3 meq/g). Sorption from a solution containing Cd2+, Cu2+, Hg2+, Ni2+, Pb2+, Zn2+, on a packed column of formaldehyde-treated peanut skin indicated that Hg2+, Pb2+, and Cu2+ were rapidly and completely bound to the packing, while Cd2+, Ni2+, and Zn2+ were poorly bound until the preferred ions had been removed from solution. 相似文献
38.
M. M. Mossoba M. P. Yurawecz J. A. G. Roach H. S. Lin R. E. McDonald B. D. Flickinger E. G. Perkins 《Lipids》1994,29(12):893-896
This study reports the structural elucidation of diunsaturated 5- or 6-membered ring cyclic fatty acid monomers (CFAM) isolated
from heated flaxseed oil by complementary gas chromatography (GC)-mass spectrometry (MS) and GC-matrix isolation-Fourier transform
infrared spectroscopy (MI-FTIR). Infrared measurements of CFAM were carried out on methyl ester derivatives as well-resolved
chromatograms were obtained on a polar 100% cyanopropyl polysiloxane capillary GC column. By contrast, electron ionization
MS of methyl ester derivatives was of limited value because of double bond migration during the ionization process in the
mass spectrometer. This communication reports definitive MS fragmentation patterns that can confirm ring position and double
bond position along the fatty acid chain in 1,2-disubstituted CFAM determined as 2-alkenyl-4,4-dimethyloxazoline derivatives.
Double bond configuration (cis, trans, or conjugatedcis,cis) in CFAM was confirmed by GC-MI-FTIR. The presence of CFAM, degradation products found in used frying oils, is a potential
source of dietary toxicity.
This work was presented in part at the 84th American Oil Chemists' Society Annual Meeting held in Anaheim, CA, in April 1993. 相似文献
39.
Abstract. It is well known that the sum of moving average processes is itself a moving average process. Existing theory does not provide formulae relating the innovations in the sum process to those in the component processes when some zeros of the autocovari-ance function of the sum process are on the unit circle. This gap is filled here by first showing that these zeros are necessarily shared by the component processes. Conditions for the innovations in the sum process to be current are given. Throughout the paper contemporary innovations in the component processes are allowed to be correlated, replacing the usual assumption that they are uncorrelated. 相似文献
40.
D. L. Purcell B. T. McClure J. McDonald Hemendra N. Basu 《Journal of the American Oil Chemists' Society》1996,73(3):381-388
An evaluation of the exhaust emissions from a compression ignition engine for fuels composed of 100 and 30% methyl esters
of soy oil (SME) is described. These fuels were compared with a low-sulfur, petroleum #2 diesel fuel in a Caterpillar 3304,
prechamber, 75 kW diesel engine, operated over heavy- and light-duty transient test cycles developed by the United States
Bureau of Mines. More than 60 h of testing was performed on each fuel. The objective was to determine the influence of the
fuels upon diesel particulate matter (DPM) and gaseous emissions. The effect of a modern diesel oxidation catalyst (DOC) also
was determined in an effort to minimize emissions. Neat SME produced a higher volatile fraction of the DPM, but much less
carbon soot fraction, leading to overall DPM reductions of 23 to 30% for the light- and heavy-duty transients. The DOC further
reduced the volatile fraction and the total DPM. The SME fuel reduced gaseous emissions of CO by 23% and hydrocarbons by over
30% without increasing NOx. The DOC further reduced CO and hydrocarbon levels. Mutagenicity of the SME exhaust was low. Results indicate that SME fuel,
used with a proper DOC, may be a feasible emission reduction technology for underground mines.
References to specific products do not imply endorsement by the U.S. Bureau of Mines, a now defunct agency. 相似文献