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排序方式: 共有2664条查询结果,搜索用时 15 毫秒
1.
D Averill D Blockus B Brabson J Brom C Jung H Ogren DR Rust M Derrick P Kooijman JS Loos B Musgrave LE Price J Repond K Sugano B Cork C Akerlof J Chapman D Errede MT Ken DI Meyer H Neal D Nitz R Thun R Tschirhart S Abachi P Baringer BG Bylsma R DeBonte D Koltick EH Low RL McIlwain DH Miller CR Ng EI Shibata 《Canadian Metallurgical Quarterly》1989,39(1):123-137
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Effect of starting particle size on hot-pressing of magnesium oxide (MgO) powder was examined using seven kinds of MgO powders
prepared by a vapour-phase oxidation process; the average primary particle sizes were 11, 25, 32, 44, 57, 107 and 261 nm.
These compressed powders (compacts) were hot-pressed at a temperature between 900 and 1300°C. The densifications of these
compacts during the hot-pressing proceeded via (i) the sintering of primary particles within secondary particles and the rearrangement
of secondary particles/grains (900°C), (ii) the gradual grain growth controlled by the pore migration (900∼1100°C) and (iii)
the rapid grain growth due to the active mass transfer (1300°C); the grain sizes of MgO compacts hot-pressed at and below
1100°C were <1 μm, while those at 1300°C attained 20∼30 μm. The transluscent compact with the relative density of 99.7% could
be obtained when the compressed powder with the average primary particle size of 44 nm was hot-pressed at a temperature as
low as 1100°C for 1 h.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
4.
CR Gaus 《Canadian Metallurgical Quarterly》1996,11(1):S26-S29
The Agency for Health Care Policy and Research (AHCPR) plays a leading role in health services research. Research efforts to develop practice guidelines, outcomes research, and computer applications have led to improvements in the delivery of care and reduced health care costs. These efforts aid consumers, providers, purchasers, and policy makers in health care decision making. This article cites numerous examples of AHCPR's efforts to increase quality of care and reduce costs. 相似文献
5.
R. H. Howell P. A. Sterne M. J. Fluss J. H. Kaiser K. Kitazawa H. Kojima 《Journal of Superconductivity and Novel Magnetism》1994,7(1):169-173
High-statistics (>4 × 108 counts), room-temperature measurements of the electron-positron momentum density of La2?x Sr x CuO4 have been performed for samples with Sr concentrations of x=0.0, 0.1, 0.13, and 0.2. These spectra have been analyzed in conjunction with theoretical calculations of the electron-positron momentum density. The metallic samples show features consistent with the presence of a Fermi surface, but its evolution with increasing Sr concentration does not follow the predictions of band theory. These results may indicate the effects of electron-electron correlation on the electron momentum distribution in the Cu-O plane. 相似文献
6.
S Modi DE Gilham MJ Sutcliffe LY Lian WU Primrose CR Wolf GC Roberts 《Canadian Metallurgical Quarterly》1997,36(15):4461-4470
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin that produces Parkinsonism symptoms in man, has been examined as a substrate of recombinant human cytochrome P450 2D6. When cumene hydroperoxide is used as an oxygen and electron donor, a single product is formed, identified as 4-phenyl-1,2,3,6-tetrahydropyridine. The K(m) for formation of this product (130 microM) is in agreement with the dissociation constants for MPTP binding to the enzyme determined by optical and nuclear magnetic resonance (NMR) spectroscopy. When the reaction is carried out with nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) and recombinant human NADPH-cytochrome P450 reductase, a second product, identified as 1-methyl-4-(4'-hydroxyphenyl)-1,2,3,6-tetrahydropyridine, is formed in addition to 4-phenyl-1,2,3,6-tetrahydropyridine. The K(m) values for formation of these two products are 19 microM and 120 microM, respectively. Paramagnetic relaxation experiments have been used to measure distances between the protons of bound MPTP and the heme iron, and these have been used to construct models for the position and orientation of MPTP in the active site. For the cytochrome alone, a single mode of binding was observed, with the N-methyl close to the heme iron in a position appropriate for the observed N-demethylation reaction. In the presence of the reductase, the data were not consistent with a single mode of binding but could be explained by the existence of two alternative orientations of MPTP in the active site. One of these, characterized by a dissociation constant of 150 microM, is essentially identical to that observed in the absence of the reductase. In the second, which has a K(d) of 25 microM, the MPTP is oriented so that the aromatic ring is close to the heme iron, in a position appropriate for p-hydroxylation leading to the formation of the product seen only in the presence of the reductase. In the case of codeine, another substrate for cytochrome P450 2D6, the addition of reductase had no effect on the nature of the product formed, the dissociation constant, or the orientation in the binding site. These observations show that NADPH-cytochrome P450 reductase has an allosteric effect on the active site of cytochrome P450 2D6 that affects the binding of some substrates but not others. 相似文献
7.
Transglutaminase (TGase), responsible for crosslinking between proteins, is known to be localized exclusively in the egg envelope (chorion) of rainbow trout, Oncorhynchus mykiss, and probably participates in the post-fertilization chorion hardening. We purified the TGase from unfertilized egg chorions by sequential chromatography using SP-Sepharose, Q-Sepharose, and TSK-gel G3000SWXL columns. The purified enzyme was a monomeric protein having the molecular mass of 76 kDa. It promoted incorporation of monodansyl-cadaverine into chorion protein and catalyzed the polymerization of chorion subunit proteins. The effect of various reagents suggested that the chorion TGase is a Ca2+-dependent SH-enzyme similar to the well-characterized TGases of various animals. The highest activity was observed at pH 6.0. The amines examined in the present study inhibited the TGase activity of the purified enzyme. However, they did not necessarily cause effective inhibition of its activity. These properties of the chorion TGase were essentially consistent with our previous observations on polymerization of chorion proteins, resulting in chorion hardening. We compared the amino acid composition of the purified TGase with those of the previously characterized TGases of fishes, such as chum salmon and red sea bream. The results suggest that the chorion 76 kDa TGase is not homologous with those liver TGases in terms of amino acid composition. 相似文献
8.
KL Hopkins PK Dickson TI Ball RR Ricketts PA O'Shea CR Abramowsky 《Canadian Metallurgical Quarterly》1997,32(10):1476-1479
Fetus-in-fetu is an unusual condition in which a vertebrate fetus is enclosed within the abdomen of another fetus. These occurrences are usually benign. This report describes an instance of malignant recurrence after resection of a fetus-in-fetu. 相似文献
9.
10.
Qualitative urinalysis methods of monitoring cocaine use may over-detect frequency of use, possibly decreasing the ability of clinical trials to detect effective treatments. Quantitative urinalysis and newly developed criteria for identifying new cocaine use were evaluated as alternative measures of cocaine use. Urine specimens collected in a cocaine dosing study in non-treatment-seeking subjects (n = 5) and a cocaine treatment trial (n = 37) were analyzed for the cocaine metabolite, benzoylecgonine, with qualitative and quantitative methods. Pharmacokinetic criteria ('New Use' rules) were applied to quantitative data to identify occasions of new cocaine use. Results were compared to known cocaine administrations in the laboratory study and to self-reported drug use and qualitative urinalysis for subjects in the clinical trial. New Use criteria correctly identified cocaine administrations in the cocaine dosing study in all but a small number of specimens. In the clinical trial, quantitative urinalysis and estimated New Uses provided more information about patterns and frequency of use than qualitative urinalysis in the different treatment conditions in the clinical trial. Interpretation of quantitative urinalysis with New Use rules appears to be a useful method for monitoring treatment outcome and may be more accurate than traditional qualitative urinalysis in estimating frequency of cocaine use. 相似文献