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51.
Novel positive‐working aqueous‐base developable photosensitive polyimide (PSPI) precursors based on partially diazonaphthoquinone (DNQ)‐capped polyamic esters bearing phenolic hydroxyl groups and a DNQ photosensitive compound (PIC‐3) were developed. The partially DNQ capped polyamic esters were prepared from an esterification reaction of 1,2‐naphthoquinone diazide‐5‐sulfonyl chloride with the polyamic esters. The partially DNQ capped polyamic esters decreased the dark film loss effectively in the aqueous‐base developer and were able to make thicker film resists compared to the uncapped polyamic esters. The 25 mol % DNQ‐capped BisAPAF–PMDA polyamic ester and BisAPAF–ODPA polyamic ester containing 25 wt % PIC‐3 photosensitive compound showed a sensitivity of 176 and 185 mJ/cm2, and a contrast of 1.68 and 1.02, respectively, in a 3‐μm film with 1.25 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 5 μm was obtained from both PSPI precursor compositions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2293–2300, 2003 相似文献
52.
Reactive Laser Ablation Synthesis of Nanosize Alumina Powder 总被引:1,自引:0,他引:1
Gregory P. Johnston Ross Muenchausen Douglas M. Smith William Fahrenholtz Steve Foltyn 《Journal of the American Ceramic Society》1992,75(12):3293-3298
An aluminum (Al) target was laser ablated in an oxygen (O2 ) atmosphere, producing nanosize alumina (Al2 O3 ) powder. The powder surface area decreased (and the particle size increased) with both increasing oxygen pressure and laser fluence. All powders produced had surface areas between 135 and 250 m2 /g, corresponding to primary particle sizes ranging from 7 to 3 nm in radius. Phase evolution with temperature was studied via X-ray diffraction. These powders showed a direct transformation from γ- to α-alumina at approximately 1200°C, bypassing other transition alumina phases, while still maintaining small particle size ( 30 nm). Despite the nanosize particles, green densities equal to 54% of the skeletal density (i.e., true density of the solid phase) were obtained by uniaxial pressing at 40 MPa. 相似文献
53.
LiNi1/3Co1/3Mn1/3O2 cathode materials have been coated with Al2O3 nano-particles using sol-gel processing to improve its electrochemical properties. The X-ray diffraction (XRD) pattern of the as-prepared Al2O3 nano-particles was indexed to the cubic structure of the γ-Al2O3 phase and had an average size of ∼4 nm. The XRD showed that the structure of LiNi1/3Co1/3Mn1/3O2 was not affected by the Al2O3 coating. However, the Al2O3 coatings on LiNi1/3Co1/3Mn1/3O2 improved the cyclic life performance and rate capability without decreasing its initial discharge capacity. These electrochemical properties were also compared with those of LiAlO2-coated LiNi1/3Co1/3Mn1/3O2 cathode material. The electrochemical impedance spectroscopy (EIS) was studied to understand the enhanced electrochemical properties of the Al2O3-coated LiNi1/3Co1/3Mn1/3O2 compared to uncoated LiNi1/3Co1/3Mn1/3O2. 相似文献
54.
Gregory P. Johnston Ross E. Muenchausen Douglas M. Smith Steve R. Foltyn 《Journal of the American Ceramic Society》1992,75(12):3465-3468
An aluminum (Al) target was laser ablated in a nitrogen (N2 ) atmosphere, producing aluminum nitride (AlN) powder. These powders were calcined at 900°C for 2 h. Powders were produced at various nitrogen pressures, and the calcined powders were tested for unreacted aluminum content, using differential thermal analysis (DTA). The AlN powder, produced at a laser fluence of 12 J/cm2 and a nitrogen pressure of 10.0 kPa (75 torr), showed no evidence of unreacted aluminum by DTA and was phase-pure AlN by X-ray diffraction (XRD). The surface area of this powder is 82 m2 /g, corresponding to a particle size of ∼11 nm, which is in good agreement with TEM observations. 相似文献
55.
Steve W. Martin Emanuel I. Cooper C. Austen Angell 《Journal of the American Ceramic Society》1983,66(9):c153-c154
A study of the high-alkali region of glass formation in the system Na2 O +B2 O3 reveals that retention of CO2 from carbonate starting materials can become a serious preparative problem at the high-alkali extreme. Results presented for glasses prepared using both Na2 O and Na2 CO3 show that residual CO2 can lead to major differences in physical properties which in this work are represented by the viscosity-related glass transition temperature . 相似文献
56.
There is a growing emphasis in many countries on matters such as participation in e-government, e-democracy, the provision of forums for online debate, and so on. A critical issue in all of these cases is one of encouraging engagement across a broad spectrum of potentially interested parties and stakeholders. In this paper, we use an ethnographic study of an online event, designed to encourage debate, to explore some critical issues in how the mechanisms productive of debate have shifted in company with the Web 2.0 phenomenon. By contrasting this with a prior study of how players managed their gameplay in a multiplayer pervasive game, we focus upon how different ways of constructing games and events can have serious implications for their ordinary everyday reportability in routine face-to-face interactions. We conclude that designing for reportability should be an active consideration when designing the resources for online debate and consider some ways in which that might be accomplished. 相似文献
57.
Steve Lien‐Chung Hsu Keng‐Chuan Chang Yuan‐Pin Huang Shih‐Jung Tsai 《应用聚合物科学杂志》2003,88(10):2388-2391
A poly(imide benzoxazole) was prepared directly from trimellitic anhydride chloride and 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane (BisAPAF) monomers in a two‐step method. In the first step, a poly(hydroxyamide amic acid) precursor was synthesized by the low‐temperature solution polymerization in an organic solvent. Subsequently, thermal cyclodehydration of the poly(hydroxyamide amic acid) precursor at 350°C produced the corresponding poly(imide benzoxazole). The inherent viscosity of the precursor polymer was 0.22 dL/g. The cyclized poly(imide benzoxazole) showed a glass transition temperature (Tg) at 329°C and a 5% weight loss temperature at 530°C in nitrogen and at 525°C in air. The poly(imide benzoxazole) is amorphous as evidenced by the wide‐angle X‐ray diffraction measurement. The structures of the precursor polymer and the fully cyclized polymer were characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2388–2391, 2003 相似文献
58.
The cut growth properties of styrene–butadiene block and random copolymers are considered in terms of the tearing energy theory. It is found that the value of T0 (the minimum value of tearing energy below which no cut growth takes place in the absence of chemical effects) is far higher for a styrene–butadiene resin copolymer system with a high amount of bound styrene resin than for a conventionally vulcanized SBR elastomer. Similarly, it is shown that the value of T0 for a butadiene–styrene block copolymer (thermoplastic rubber) is considerably reduced when the material is crosslinked. It is proposed that the value of T0 is influenced by the hystersial properties of the rubber. 相似文献
59.
Abdellatif Mohamed Mila P. Hojilla-Evangelista Steve C. Peterson Girma Biresaw 《Journal of the American Oil Chemists' Society》2007,84(3):281-288
Barley protein isolate (BPI) was extracted in 0.015 N NaOH in a 10:1 ratio solvent:flour and was precipitated by adjusting
the pH to 4.5 and freeze-dried. The thermal properties of BPI were determined using modulated differential scanning calorimetry
(MDSC). BPI with 4% moisture content exhibited a glass transition (T
g) with 140 °C onset, 153 °C middle, and 165 °C end temperatures and a ΔC
p of 0.454 J/g per °C. The high moisture content sample (50%) showed a T
g at 89, 91, or 94 °C and 0.067 ΔC
p. Acetylation had no apparent effect on the foaming and emulsifying properties of protein from barley flour but exhibited
the least-stable foam among BPI samples. Foaming capacities of both barley protein isolates were ∼12% less than that of acid-precipitated
soy protein isolate reported in the literature. Acetylated BPI showed the highest surface hydrophobicity compared to the other
samples. The surface-tension test confirmed that unmodified and modified BPI possessed surface activity. BPI phosphorous oxycloride-crosslinked
was the most effective in lowering the surface tension of aqueous NaCl, while the crosslinked BPI was the least effective.
The G′ value of BPI suspension was greater than G″ at all frequencies from 0.1 to 100 rad/s. The strain value at which linear behavior ceased and nonlinear behavior began
ranged from 3 to 10%.
Names are necessary to report factually on available data; however, the United States Department of Agriculture (USDA) neither
guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product
to the exclusion of others that may also be suitable. 相似文献
60.
Phosphatidylcholine acyltransferase (lecithin:cholesterol acyltransferase or LCAT; EC 2.3.1.43) activity was found to be present
in pig ovarian follicular fluid (POFF), in addition to pig serum (PS). The cholesterol esterification rate in both POFF and
PS is linear with incubation time up to 2 hr. The mean absolute rate of POFF-cholesterol esterification was 8.1±0.4 nmoles
per ml per hr approximately one-fourth of that in PS. However, the fractional rate (percent of labeled cholesterol esterified
per hr) of POFF-cholesterol esterification was similar to that observed in PS. There was little variation of absolute rate
of cholesterol esterification in the fluid obtained from different sizes of follicles. Fatty acid or triacylglycerol did not
participate in the reaction of cholesterol esterification in POFF. No appreciable change in enzymatic activity was found from
storing POFF at 4 C for periods of time up to 24 hr or at −70 C up to 2 months, but activity was lost thereafter. On the other
hand, PS showed a much longer period of stability (5 days at 4 C and 9 months at −70 C). A discrepancy between the fatty acid
composition of cholesteryl esters formed by the LCAT reaction and the fatty acid composition at the C-2 position of phosphatidylcholine
led us to propose a two-step mechanism for the LCAT reaction. It is concluded that the LCAT of POFF, as well as that of plasma,
is specific for individual fatty acids rather than for the fatty acid composition of phosphatidylcholine. The fatty acid concentration
of lysophosphatidylcholine decreased during prolonged incubation times (6 to 21 hr) suggesting that the increased lysophosphatidylcholine
formed as a product of the LCAT reaction may be reused as substrate for the LCAT reaction or for hydrolysis by lysophosphatidylcholine
hydrolase.
Presented at the AOCS Meeting, New York, May 1977. 相似文献