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91.
Keith D. Bartle Michael J. Mulligan Norman Taylor Terence G. Martin Colin E. Snape 《Fuel》1984,63(11):1556-1560
A number of procedures have been investigated for the calibration of a size-exclusion chromatography (s.e.c.) column in the determination of molecular mass (MM) distributions of coal derivatives. The behaviour of narrow fractions of coal extracts in the MM range 200–3000 was compared with a variety of the more generally available calibration standards. Calibration with preparative s.e.c. subfractions of materials similar to those under study has been recommended. Polystyrene standards are satisfactory, however, for MM < 1000, but above this range other polymer standards should be sought. Universal and molar volume calibration do not apply to coal-derived materials. 相似文献
92.
Widely different hydrogen adsorption capacities have been reported for a variety of carbon materials which have attracted attention for hydrogen storage. This has led to doubts as to the validity of some of the claims and it has been suggested that one possible reason for the disparate hydrogen sorption capacities may lie in the inaccurate measurement of the hydrogen adsorbed. The aim of the work described in this paper was to make a contribution to this debate by developing a means and method of producing repeatable, accurate measurements of hydrogen sorption capacity in carbon materials. The apparatus developed is a volumetric differential pressure set-up operating at up to 10 MPa and the method has a conservative limit of detection of 0.1 wt% and an accuracy of ±0.05 wt%, using 1.0-2.5 g samples of the carbon materials studied. These included a carbon nanofiber sample and a series of activated carbons, the latter displaying a direct correlation between the BET effective surface area and the hydrogen sorption capacity of the materials. The amount of hydrogen adsorbed was less than 1 wt% for all the carbons examined. 相似文献
93.
Cessation of polyunsaturated fatty acid formation in four selected filamentous fungi when grown on plant oils 总被引:6,自引:0,他引:6
Four fungi,Conidiobolus nanodes, Entomophthora exitalis, Mortierella isabellina, andMucor circinelloides, were grown on various oils (triolein, sesame, safflower, linseed, and oil fromM. isabellina) and produced lipids in which the fatty acids were predominantly the same as those of the original staring substrate. Only
in the first two cases was there evidence of a small amount of chain elongation and of fatty acid desaturation taking place.
The extent of this was only about 10% of that seen in glucose-grown cells. The apparent repression of the fatty acid desaturases
and elongases was not reversed by growing cells on glucose and oils as mixed substrates—the fatty acid profiles were the same
as when the fungi had grown in oils alone. Neither was the cessation of polyunsaturated fatty acid synthesis due to the presence
of nonoil components (NOC) in the oil. Only the NOC from sesame oil affected one single conversion, that of 20∶3n-3 to 20∶4n–6.
We conclude that fatty acid desaturase and elongase systems are repressed either partially or completely in a filamentous
fungi grown on triacylglycerol oils. 相似文献
94.
Mono-carboxylic, straight-chain fatty acids are present in extracts of lignite and subbituminous coal (0.4–1.0 wt%, daf basis), but not in those of a bituminous coal. They are removed with nearly equal ease by both solvent and supercritical gas (SCG) extraction. Octacosanoic acid is the major constituent, and values of the carbon preference index (even over odd) lie between 2 and 6. Solvent extraction of the coals also removes small quantities (< 0.08 wt%) of straight-chain alkanes which are closely related in composition to the straight-chain fatty acids and are probably derived from them during maturation. However, previous SCG extraction of the coals yielded much larger quantities of straight-chain alkanes (0.3–0.7 wt%). Pyrolysis experiments with a lignite fatty acid fraction and with tetracosanoic acid show that these acids largely survive SCG extraction and, therefore, are not the main source of the relatively large quantity of straight-chain alkanes in these extracts. 相似文献
95.
96.
Dr. Jessica S. Kelsey Dr. Tamas Geczy Nancy E. Lewin Dr. Noemi Kedei Colin S. Hill Julia S. Selezneva Christopher J. Valle Wonhee Woo Dr. Inna Gorshkova Dr. Peter M. Blumberg 《Chembiochem : a European journal of chemical biology》2014,15(8):1131-1144
The C1 domain, which represents the recognition motif on protein kinase C for the lipophilic second messenger diacylglycerol and its ultrapotent analogues, the phorbol esters, has emerged as a promising therapeutic target for cancer and other indications. Potential target selectivity is markedly enhanced both because binding reflects ternary complex formation between the ligand, C1 domain, and phospholipid, and because binding drives membrane insertion of the C1 domain, permitting aspects of the C1 domain surface outside the binding site, per se, to influence binding energetics. Here, focusing on charged residues identified in atypical C1 domains which contribute to their loss of ligand binding activity, we showed that increasing charge along the rim of the binding cleft of the protein kinase C δ C1 b domain raises the requirement for anionic phospholipids. Correspondingly, it shifts the selectivity of C1 domain translocation to the plasma membrane, which is more negatively charged than internal membranes. This change in localization is most pronounced in the case of more hydrophilic ligands, which provide weaker membrane stabilization than do the more hydrophobic ligands and thus contributes an element to the structure–activity relations for C1 domain ligands. Coexpressing pairs of C1‐containing constructs with differing charges each expressing a distinct fluorescent tag provided a powerful tool to demonstrate the effect of increasing charge in the C1 domain. 相似文献
97.
This work has two objectives in the investigation of polymer solution lower critical solution temperature (LCST): First, to develop a new instrument to monitor LCST onset during copolymer synthesis by coupling several thermostatted light scattering flow cells to the output stream of an ACOMP system (Automatic Continuous Online Monitoring of Polymerization reactions). Second, to use this to investigate effects on LCST when N-isopropylacrylamide (NIPAM) is copolymerized with a charged comonomer, styrene sulfonate (SS). This comonomer pair has widely separated reactivity ratios. SS is rapidly consumed, yielding composition drift toward NIPAM rich polymer. High content SS chains inhibited LCST, and SS was dramatically effective at suppressing LCST down to copolymers of 5% molar SS in 10 mM NaCl aqueous solvent. LCST for higher content SS chains was elevated and required significant additional ionic strength to occur. It was determined that the suppression of the LCST by SS is chiefly an intramolecular effect. 相似文献
98.
Colin Davies 《电子产品世界》2007,(10):72-72,74,76
毋庸置疑,高亮LED将成为未来一代汽车的主要特征.这是由于LED相对于传统的白炽光照明方案,具备许多重要优势.同时,采用LED也可带动技术上,甚至汽车设计风格上的变化.但是,正如任何革新技术,LED在广泛运用于汽车照明前,仍有许多困难需要克服. 相似文献
99.
100.
E. Siranidi D. Lampakis D. Palles E. Liarokapis C. Colin T. T. M. Palstra 《Journal of Superconductivity and Novel Magnetism》2009,22(2):185-188
The spin and orbital ordering have been examined for high-quality SmVO3 polycrystalline compound using Raman spectroscopy. Measurements were obtained on individual microcrystallites in the approximate
y(zz)y and y(xx)y scattering configurations at low temperatures (down to 20 K) and high pressures (up to 2.75 GPa). At room temperature and
ambient pressure only the Ag phonons have been observed in both polarizations examined. The decrease of temperature leads to the appearance of extra peaks
in the Raman spectra related to the magnetic and structural transitions that occur in the system. We present evidence of a
coexistence of the monoclinic and orthorhombic phases accompanied with the coexistence of the G- and C-type OO phases for
temperatures below 100 K. However, no sign of any structural transition has been observed in the high pressure Raman spectra
(1.87<P<2.75 GPa) at low temperatures T≥80 K, indicating that SmVO3 remains orthorhombic, at least down to 80 K. 相似文献