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991.
Milk production, rumen fermentation, and whole-tract apparent nutrient digestibility in response to feeding 20% steam-rolled wheat with or without sodium bicarbonate were evaluated in 12 Holstein cows averaging 165 ± 16 DIM. Cows were fed 1 of 2 isoenergetic and isonitrogenous diets containing either 0 or 0.75% sodium bicarbonate on a DM basis for 21 d in a crossover design. Rumen fluid samples were obtained 18 times during the last 2 d of each period, and fecal samples were collected on 12 occasions from d 18 to 21 of each period. Removal of sodium bicarbonate from the diet did not affect DMI (21.0 kg/d), yields of milk (30.8 kg/d), or milk components (1.16, 1.01, and 1.40 kg/d for fat, protein, and lactose, respectively). Whole-tract apparent digestibility of DM, CP, ADF, and NDF did not differ between the 2 treatments (75.3, 76.6, 67.2, and 63.6%, respectively). The mean rumen pH was 6.24 and was not affected by excluding sodium bicarbonate from the diet. Rumen NH3-N (12.31 mg/dL) and lactic acid (3.63 mM) concentrations were not different, whereas total volatile fatty acids concentration tended to increase when sodium bicarbonate was present in the diet (110 vs. 116 mM). However, average concentrations of the individual volatile fatty acids, as a proportion of total volatile fatty acids, were not affected by treatment. In conclusion, dairy cow diets can include up to 20% steam-rolled wheat without the need for added sodium bicarbonate as long as the diets are formulated to meet the fiber requirements of the cow. 相似文献
992.
Martins JP Policelli RK Neuder LM Raphael W Pursley JR 《Journal of dairy science》2011,94(6):2815-2824
Luteolysis is a key event in Ovsynch programs of lactating dairy cows. Studies indicate that as many as 20% of cows treated with a Presynch/Ovsynch program have delayed or incomplete luteolysis using dinoprost tromethamine. Cows must have complete luteolysis to have a chance to become pregnant. Dinoprost tromethamine has a short half-life of approximately 7 to 8 min. Cloprostenol sodium is more resistant to endogenous metabolism and is maintained in circulation for a longer time (half-life = 3 h). The objective was to determine if cloprostenol sodium could increase the percentage of cows with complete luteolysis and subsequent pregnancy per artificial insemination (P/AI) in lactating dairy cows compared with dinoprost tromethamine when administered within a presynchronization plus Ovsynch program for first artificial insemination (n = 652) and an Ovsynch resynchronization program for second or later AI (second+; n = 394). Blood samples were collected daily for 5 d beginning at the PGF2α of Ovsynch in a subset of cows (n = 680) for first and second+ AI to measure circulating concentrations of progesterone (P4) and estradiol (E2). Complete luteolysis was defined as cows with functional corpus luteum (CL) at time of treatment and serum concentrations of P4 <0.5 ng/mL at 56, 72, and 96 h after treatment. Percentage of cows with functional CL that had complete luteolysis after treatment was not greater for cloprostenol sodium compared with dinoprost tromethamine in first (79 vs. 80%, respectively) or second+ AI (70 vs. 72%, respectively). In addition, mean serum concentrations of P4 were not less for cows treated with cloprostenol sodium following treatment. Pregnancy per AI of cows treated with cloprostenol sodium tended to be greater than dinoprost tromethamine for first (40 vs. 35%; respectively) but not second+ AI (23 vs. 21%, respectively). Cows with greater serum P4 concentrations at time of PGF2α of Ovsynch had a greater probability of undergoing complete luteolysis after PGF2α of Ovsynch and pregnancy at 39 d after timed AI (i.e., 50% pregnant at 8 vs. 28% pregnant at 4 ng/mL P4). Serum concentrations of E2 at 56 h after PGF2α of Ovsynch were a positive predictor of pregnancy at 39 d after timed AI. In summary, cloprostenol sodium tended to improve P/AI. Cows with greater serum concentrations of P4 at time of PGF2α of Ovsynch had a greater chance of luteolysis and pregnancy. 相似文献
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996.
乙酸钠浓度对AZ91D镁合金锡酸盐转化膜的影响 总被引:1,自引:0,他引:1
镁合金的无铬化学转化处理已成为其防护技术研究的一个重要方向,为此,开发了一种以乙酸钠为主要成分的镁合金锡酸盐转化工艺,采用全浸腐蚀试验、扫描电镜(SEM)、X射线衍射(XRD)等方法研究了AZ91D镁合金在含不同乙酸钠浓度成膜液中所形成膜层的结构,并比较了膜层的耐腐蚀性能.结果表明:成膜过程中,随着成膜液中乙酸钠浓度的... 相似文献
997.
Alexander J. C. Kuehne Markus Kaiser Allan R. Mackintosh Bodo H. Wallikewitz Dirk Hertel Richard A. Pethrick Klaus Meerholz 《Advanced functional materials》2011,21(13):2564-2570
The metastable β‐phase morphology, inherent to most polyfluorene homo‐polymers, is of interest due to its superior optical and electrical characteristics compared to its amorphous analogue. Here, a polyfluorene with vinyl‐ether‐functionalized aliphatic side‐chains that allow crosslinking is reported. It is demonstrated that the previously induced conformational morphology is preserved in the resulting polyfluorene network, which enables subsequent wet thin‐film processing. Electron‐beam lithography provides a means for sub‐(optical)‐wavelength patterning of the crosslinkable polyfluorene films. As a specific demonstration, optically‐pumped distributed‐feedback (DFB) lasers made from surface‐relief gratings in amorphous and β‐phase polyfluorene are presented. By backfilling gratings of one morphology by the other, devices are demonstrated that exhibit lasing at two wavelengths with a threshold (<1 μJ cm?2) at least an order of magnitude lower compared with previous data. 相似文献
998.
Leszek Zalewski Sergio Brovelli Massimo Bonini Jeffrey M. Mativetsky Michael Wykes Emanuele Orgiu Thomas Breiner Marcel Kastler Florian Dötz Francesco Meinardi Harry L. Anderson David Beljonne Franco Cacialli Paolo Samorì 《Advanced functional materials》2011,21(5):834-844
A comparative study of the self‐assembly at a variety of surfaces of a dithiophene rotaxane 1 ?β‐CD and its corresponding dumbbell, 1, by means of atomic force microscopy (AFM) imaging and scanning tunneling microscopy (STM) imaging on the micrometer and nanometer scale, respectively. The dumbbell is found to have a greater propensity to form ordered supramolecular assemblies, as a result of π–π interactions between dithiophenes belonging to adjacent molecules, which are hindered in the rotaxane. The fine molecular structure determined by STM was compared to that obtained by molecular modelling. The optical properties of both rotaxane and dumbbell in the solid state were investigated by steady‐state and time‐resolved photoluminescence (PL) experiments on spin‐cast films and diluted solutions. The comparison between the optical features of the threaded and unthreaded systems reveals an effective role of encapsulation in reducing aggregation and exciton migration for the rotaxanes with respect to the dumbbells, thus leading to higher PL quantum efficiency and preserved single‐molecule photophysics for longer times after excitation in the threaded oligomers. 相似文献
999.
Mi Jung Lee Dhritiman Gupta Ni Zhao Martin Heeney Iain McCulloch Henning Sirringhaus 《Advanced functional materials》2011,21(5):932-940
Charge transport in the ribbon phase of poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT)—one of the most highly ordered, chain‐extended crystalline microstructures available in a conjugated polymer semiconductor—is studied. Ribbon‐phase PBTTT has previously been found not to exhibit high carrier mobilities, but it is shown here that field‐effect mobilities depend strongly on the device architecture and active interface. When devices are constructed such that the ribbon‐phase films are in contact with either a polymer gate dielectric or an SiO2 gate dielectric modified by a hydrophobic, self‐assembled monolayer, high mobilities of up to 0.4 cm2 V?1 s?1 can be achieved, which is comparable to those observed previously in terrace‐phase PBTTT. In uniaxially aligned, zone‐cast films of ribbon‐phase PBTTT the mobility anisotropy is measured for transport both parallel and perpendicular to the polymer chain direction. The mobility anisotropy is relatively small, with the mobility along the polymer chain direction being higher by a factor of 3–5, consistent with the grain size encountered in the two transport directions. 相似文献
1000.
Chengfen Xing Libing Liu Hongwei Tang Xuli Feng Qiong Yang Shu Wang Guillermo C. Bazan 《Advanced functional materials》2011,21(21):4058-4067
Multifunctional materials that simultaneously provide therapeutic action and image the results provide new strategies for the treatment of various diseases. Here, it is shown that water soluble conjugated polymers with a molecular design centered on the polythiophene?porphyrin dyad are effective for killing neighboring cells. Following photoexcitation, energy is efficiently transferred from the polythiophene backbone to the porphyrin units, which readily produce singlet oxygen (1O2) that is toxic for the cells. Due to the light‐harvesting ability of the electronically delocalized backbone and the efficient energy transfer amongst optical partners, the polythiophene?porphyrin dyad shows a higher 1O2 generation efficiency than a small molecule analog. The fluorescent properties of these polymers can also serve to distinguish amongst living and dead cells. Polymers can be designed with folic acid grafted onto the polymer side chain that can specifically kill folate receptor‐overexpressed cells, thereby providing an important demonstration of anticancer specificity through molecular design. 相似文献