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61.
Nitrous oxide emissions from an Uruguayan argiudoll under different tillage and rotation treatments 总被引:1,自引:0,他引:1
Lack of local data limits estimation of nitrous oxide (N2O) emissions from different land uses of Uruguay. As a first step towards obtaining local information, we measured from August
2003 to September 2004 N2O fluxes from a rotation-by-tillage experiment established in 1993 and from a nearby natural pasture (NP). Nitrous oxide emission
rates were measured on an event-driven basis by using the closed chamber technique with six replicates per treatment. Fluxes
varied considerably with time and the higher rates (more than 30 g N ha−1 day−1) were generally associated with periods of high soil water content, high temperature, and/or decreasing soil nitrate. We
could not identify, however, any statistically significant correlation between flux and these variables. Throughout the evaluation
period, fluxes from crops or cultivated pastures tended to be higher than those from NP, but the effects of tillage (no-till
and conventional tillage) or rotation (continuous tillage and rotation with pasture) were not consistent. The application
of 112 kg N ha−1 to barley did not increase N2O fluxes probably due to a high fertilizer use efficiency caused by the recommended three-split application and by the lack
of rain during this period. The annual cumulative flows of different treatments compared well with those estimated using IPCC
methodology, but the high spatial and temporal variability observed in this one-year study indicate that further research
is needed to obtain reliable data on N2O fluxes from agricultural soils of Uruguay. 相似文献
62.
José Antonio Gárate María de los Ángeles Valenzuela María Pilar Gárate Andrés F. Olea 《Journal of surfactants and detergents》2009,12(3):231-236
The solubility and aggregation process of polyethoxylated non-ionic surfactants, of general formula C
i
H2i+1–(O–CH2–CH2)
j
–OH with i = 6, 8, 10 and j = 3–6 (C
i
EO
j
), in heptane were studied. The aggregation of C
i
EO
j
surfactants in heptane was investigated by using methylene blue (MB) as an absorption probe. In solutions of MB in the presence
of these surfactants in heptane, at concentrations larger than the re-dissolution concentration, the UV bands associated to
free MB (A
1) and MB–EO complex (A
2) were detected. The ratio of these intensities A
2/A
1, was used to study the kinetics of the complex formation in pure surfactant. The value of A
2/A
1 depends on the surfactant structure and the media wherein MB is dissolved, being larger in the pure surfactant than in heptane
solutions. These results are explained in terms of solvent effect and aggregate structures on the complex formation.
相似文献
Andrés F. Olea (Corresponding author)Email: |
63.
The manufacture of β-Si3N4 seeds by self-propagating high temperature synthesis (SHS) presents some advantages, such as the low production costs, compared to other preparation methods based on sintering of α-Si3N4 powders and subsequent leaching out of the glassy phase. However, SHS process produces seed clusters that must be disentangled before use as reinforcing particles. Different mechanical and chemical treatments were tried to achieve good seed dispersion, proving that a combined treatment based on a hot basic etching and a short time attrition milling gave almost agglomerate-free particles with adequate features for seeding use. 相似文献
64.
Ramon Margalef‐Català Pilar Salagre Elena Fernández Carmen Claver 《Catalysis Letters》1999,60(3):121-123
Heterogenised homogeneous catalytic hydrogenation of aldimines by removable and reusable immobilised iridium complexes on montmorillonite clay. This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
65.
Oxidation of BN/Nicalon Fiber Interfaces in Ceramic-Matrix Composites and Its Effect on Fiber Strength 总被引:1,自引:0,他引:1
José Pérez-Rigueiro José Antonio Celemín Javier LLorca Pilar Herrero 《Journal of the American Ceramic Society》1999,82(12):3494-3500
Microstructural changes at the interface were analyzed in two Nicalon-fiber ceramic-matrix composites with a dual BN/SiC coating on the fibers after thermal exposure at different temperatures (in the range 800°-1400°C) and in different environments (air and argon). The outer SiC coating acted as a barrier to oxygen, which penetrated into the composite via pipeline diffusion along the BN/fiber interfaces. Oxygen penetration led to the formation of an SiO2 layer by oxidation of the fiber surfaces. The in situ fiber strength at different temperatures, as determined from the radius of the mirror region on the fiber fracture surface, indicated that this SiO2 layer severely degraded the fiber strength. Oxidation was highly dependent on the nature of the BN/fiber interface. The presence of a thin carbon-rich interlayer, which burned out rapidly at high temperature, favored the entry of oxygen and accelerated oxidation of the fibers. 相似文献
66.
Elsa Corts-Montero María Rodríguez-Muoz M. Carmen Ruiz-Cantero Enrique J. Cobos Pilar Snchez-Blzquez Javier Garzn-Nio 《International journal of molecular sciences》2021,22(1)
Transient receptor potential ankyrin member 1 (TRPA1) belongs to the family of thermo TRP cation channels that detect harmful temperatures, acids and numerous chemical pollutants. TRPA1 is expressed in nervous tissue, where it participates in the genesis of nociceptive signals in response to noxious stimuli and mediates mechanical hyperalgesia and allodynia associated with different neuropathies. The glutamate N-methyl-d-aspartate receptor (NMDAR), which plays a relevant role in allodynia to mechanical stimuli, is connected via histidine triad nucleotide-binding protein 1 (HINT1) and type 1 sigma receptor (σ1R) to mu-opioid receptors (MORs), which mediate the most potent pain relief. Notably, neuropathic pain causes a reduction in MOR antinociceptive efficacy, which can be reversed by blocking spinal NMDARs and TRPA1 channels. Thus, we studied whether TRPA1 channels form complexes with MORs and NMDARs that may be implicated in the aforementioned nociceptive signals. Our data suggest that TRPA1 channels functionally associate with MORs, delta opioid receptors and NMDARs in the dorsal root ganglia, the spinal cord and brain areas. These associations were altered in response to pharmacological interventions and the induction of inflammatory and also neuropathic pain. The MOR-TRPA1 and NMDAR-TRPA1 associations do not require HINT1 or σ1R but appear to be mediated by calcium-activated calmodulin. Thus, TRPA1 channels may associate with NMDARs to promote ascending acute and chronic pain signals and to control MOR antinociception. 相似文献
67.
68.
Marta Gmez-Ferrer Estela Villanueva-Badenas Rafael Snchez-Snchez Christian M. Snchez-Lpez Maria Carmen Baquero Pilar Sepúlveda Akaitz Dorronsoro 《International journal of molecular sciences》2021,22(7)
Despite the strong evidence for the immunomodulatory activity of mesenchymal stromal cells (MSCs), clinical trials have so far failed to clearly show benefit, likely reflecting methodological shortcomings and lack of standardization. MSC-mediated tissue repair is commonly believed to occur in a paracrine manner, and it has been stated that extracellular vesicles (EVs) secreted by MSCs (EVMSC) are able to recapitulate the immunosuppressive properties of parental cells. As a next step, clinical trials to corroborate preclinical studies should be performed. However, effective dose in large mammals, including humans, is quite high and EVs industrial production is hindered by the proliferative senescence that affects MSCs during massive cell expansion. We generated a genetically modified MSC cell line overexpressing hypoxia-inducible factor 1-alpha and telomerase to increase the therapeutic potency of EVMSC and facilitate their large-scale production. We also developed a cytokine-based preconditioning culture medium to prime the immunomodulatory response of secreted EVs (EVMSC-T-HIFc). We tested the efficacy of this system in vitro and in a delayed-type hypersensitivity mouse model. MSC-T with an HIF-1α-GFP lentiviral vector (MSC-T-HIF) can be effectively expanded to obtain large amounts of EVs without major changes in cell phenotype and EVs composition. EVMSC-T-HIFc suppressed the proliferation of activated T-cells more effectively than did EVs from unmodified MSC in vitro, and significantly blunted the ear-swelling response in vivo by inhibiting cell infiltration and improving tissue integrity. We have developed a long-lived EV source that secretes high quantities of immunosuppressive EVs, facilitating a more standard and cost-effective therapeutic product. 相似文献
69.
Fernando Corvillo Laura Gonzlez-Snchez Alberto Lpez-Lera Emilia Arjona Giovanni Ceccarini Ferruccio Santini David Araújo-Vilar Rebecca J Brown Joan Villarroya Francesc Villarroya Santiago Rodríguez de Crdoba Teresa Caballero Pilar Nozal Margarita Lpez-Trascasa 《International journal of molecular sciences》2021,22(12)
70.
Mario Gonzalez-de la Parra Pilar Rodriguez-Loaiza Salvador Namur 《Quality Engineering》2006,18(2):225-235
The impurity profile is one of the most important quality characteristics of a drug substance. Although it is always desirable to determine the chemical structure of all impurities forming the impurity profile, unfortunately this is not always economically and technically feasible because of the extremely low concentrations at which some impurities may be found in the drug substance. Therefore, alternative approaches to the chemical analysis are needed for trying to determine the origin of the unidentified impurities.
In a previous study conducted by our group, based on exploratory (principal component and hierarchical cluster) analysis, we were able to suggest a hypothesis for explaining the origin of the unidentified impurities of a drug substance. However, there was still a concern that alternative hypotheses might explain the same phenomenon equally well. This article explores the application of recent developments in structural equation modeling for the systematic generation and selection of hypotheses (models) worthy of being confirmed by chemical research. 相似文献
In a previous study conducted by our group, based on exploratory (principal component and hierarchical cluster) analysis, we were able to suggest a hypothesis for explaining the origin of the unidentified impurities of a drug substance. However, there was still a concern that alternative hypotheses might explain the same phenomenon equally well. This article explores the application of recent developments in structural equation modeling for the systematic generation and selection of hypotheses (models) worthy of being confirmed by chemical research. 相似文献