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951.
Foetal fibroblasts introduced to cleaving mouse embryos contribute to full-term development 总被引:1,自引:0,他引:1
Piliszek A Modliński JA Pyśniak K Karasiewicz J 《Reproduction (Cambridge, England)》2007,133(1):207-218
Foetal fibroblasts (FFs) labelled with vital fluorescent dye were microsurgically introduced into eight-cell mouse embryos, three cells to each embryo. FFs were first identified in the inner cell mass (ICM) in about one-third of embryos, whereas in three quarters of embryos FFs were located among trophoblast cells. Some elimination of FFs from trophoblast occurred later on. Eventually, in blastocysts' outgrowths, an equally high contribution from FFs progeny (60%) was found in both ICM and trophoblast. Three days after manipulation, FFs resumed proliferation in vitro. More than three FFs were found in 46.2% of embryos on day 4. On the 7th day in vitro in 70% of embryos more than 12 FFs were found, proving at least three cell divisions. To study postimplantation development, the embryos with FFs were transferred to pseudopregnant recipients a day after manipulation. After implantation, FFs were identified by electrophoresis for isozymes of glucose phosphate isomerase (GPI). A single 11-day embryo delayed to day 8 proved chimeric by expressing both donor isozyme GPI-1B and recipient GPI-1A. Similar chimerism was found in the extraembryonic lineage of 11% of embryos by day 12. Starting from day 11 onwards, in 32% of normal embryos and in 57% of foetal membranes, hybrid GPI-1AB isozyme, as well as recipient isozyme, was present. Hybrid GPI-1AB can only be produced in hybrid cells derived by cell fusion, therefore, we suggest that during postimplantation development, FFs are rescued by fusion with recipient cells. In the mice born, hybrid isozyme was found in several tissues, including brain, lung, gut and kidney. We conclude that somatic cells (FFs) can proliferate in early embryonic environment until early postimplantation stages. Foetuses and the mice born are chimeras between recipient cells and hybrid cells with contributions from the donor FFs. Transdifferentiation as opposed to reprogramming by cell fusion can be considered as underlying cellular processes in these chimeras. 相似文献
952.
Rodríguez E Simoes RV Roig A Molins E Nedelko N Slawska-Waniewska A Aime S Arús C Cabañas ME Sanfeliu C Cerdán S García-Martín ML 《Magma (New York, N.Y.)》2007,20(1):27-37
A new iron-based T 1 contrast agent consisting of a complex of iron ions coordinated to phosphate and amine ligands (Fe(phos) in short) has been characterized by spectroscopic and magnetic measurements. NMR relaxation studies showed r 1 values to be dependent on the phosphate salt concentration, K2HPO4, present in the medium. r 1 reaches a maximum value of 2.5 mM?1 s?1 for measurements carried out at 7 T and 298 K. 31P MRS, Mössbauer spectroscopy and magnetic measurements of Fe(phos) solutions suggest paramagnetic Fe3+ ions present in the studied iron–phosphate complex. In vitro and in vivo toxicity experiments with C6 cells and CD1 mice, respectively, demonstrated lack of toxicity for Fe(phos) at the highest dose tested in the MRI experiments (12 mM iron for C6 cells and 0.32 mmol iron/kg for mice). Finally, T 1 weighted images of brain tumours in mice have shown positive contrast enhancement of Fe(phos) for tumour afflicted regions in the brain. 相似文献
953.
Ros A Lillo-Ródenas MA Canals-Batlle C Fuente E Montes-Morán MA Martin MJ Linares-Solano A 《Environmental science & technology》2007,41(12):4375-4381
The present paper discusses H2S removal by a new generation of sewage-sludge-derived materials which are characterized by their outstanding textural properties when compared to previous materials obtained by pyrolysis and/or activation of similar precursors. Alkaline hydroxide activation was used to prepare adsorbents/catalysts covering a wide range of porosities (SBET values from 10 to 1300 m2 g(-1)). Our results outline that textural properties are important for H2S abatement. However, not only highly porous sorbents, but also a high metallic content and a basic pH of these materials are required to achieve good performances. Proper combinations of textural properties and alkalinity render superior performances with retention values (x/M) as high as 456 mg of H2S removed per g of material. These retention capacities outperform previously published data for sewage-sludge derived materials and those achieved with commercial materials (including some activated carbons). Sulfur titration shows that most H2S is removed in the form of elemental sulfur, especially in the sewage/NaOH materials. 相似文献
954.
Davis BJ Swan AK Unlü MS Karl WC Goldberg BB Schotland JC Carney PS 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(11):3587-3599
A theoretical and numerical analysis of spectral self-interference microscopy (SSM) is presented with the goal of expanding the realm of SSM applications. In particular, this work is intended to enable SSM imaging in low-signal applications such as single-molecule studies. A comprehensive electromagnetic model for SSM is presented, allowing arbitrary forms of the excitation field, detection optics, and tensor sample response. An evanescently excited SSM system, analogous to total internal reflection microscopy, is proposed and investigated through Monte Carlo simulations. Nanometer-scale axial localization for single-emitter objects is demonstrated, even in low-signal environments. The capabilities of SSM in imaging more general objects are also considered--specifically, imaging arbitrary fluorophore distributions and two-emitter objects. A data-processing method is presented that makes SSM robust to noise and uncertainties in the detected spectral envelope. 相似文献
955.
Resonant Raman spectroscopy of single carbon nanotubes suspended across trenches displays red-shifts of up to 30 meV of the electronic transition energies as a function of the surrounding dielectric environment. We develop a simple scaling relationship between the exciton binding energy and the external dielectric function and thus quantify the effect of screening. Our results imply that the underlying particle interaction energies change by hundreds of meV. 相似文献
956.
Single-source molecular precursors were found to produce iron phosphide materials. In a surfactant system of trioctylamine and oleic acid, H2Fe3(CO)9PtBu reacted to form Fe4(CO)12(PtBu)2, which decomposed to give Fe2P nanorods and "bundles." Control of the morphology obtained was possible by varying the surfactant system; addition of increasing amounts of oleic acid resulted in crystal splitting, while the addition of microliter amounts of an alkane enhanced the crystal splitting to give sheaflike structures. The different morphologies seen were attributed to imperfect crystal growth mechanisms. 相似文献
957.
Herland A Björk P Hania PR Scheblykin IG Inganäs O 《Small (Weinheim an der Bergstrasse, Germany)》2007,3(2):318-325
The amyloid-like fibril is a biomolecular nanowire template of very high stability. Here we describe the coordination of a conjugated polyelectrolyte, poly(thiophene acetic acid) (PTAA), to bovine insulin fibrils with widths of <10 nm and lengths of up to more than 10 microm. Fibrils complexed with PTAA are aligned on surfaces through molecular combing and transfer printing. Single-molecule spectroscopy techniques are applied to chart spectral variation in the emission of these wires. When these results are combined with analysis of the polarization of the emitted light, we can conclude that the polymer chains are preferentially aligned along the fibrillar axis. 相似文献
958.
A patterned anisotropic nanofluidic sieving structure for continuous-flow separation of DNA and proteins 总被引:2,自引:0,他引:2
Microfabricated regular sieving structures hold great promise as an alternative to gels to improve the speed and resolution of biomolecule separation. In contrast to disordered porous gel networks, these regular structures also provide well defined environments ideal for the study of molecular dynamics in confining spaces. However, the use of regular sieving structures has, to date, been limited to the separation of long DNA molecules, however separation of smaller, physiologically relevant macromolecules, such as proteins, still remains a challenge. Here we report a microfabricated anisotropic sieving structure consisting of a two-dimensional periodic nanofluidic filter array. The designed structural anisotropy causes different-sized or -charged biomolecules to follow distinct trajectories, leading to efficient separation. Continuous-flow size-based separation of DNA and proteins, as well as electrostatic separation of proteins, was achieved, demonstrating the potential use of this device as a generic molecular sieving structure for an integrated biomolecule sample preparation and analysis system. 相似文献
959.
Use of Sacrificial Piles as Pier Scour Countermeasures 总被引:2,自引:0,他引:2
Laboratory studies on the use of sacrificial piles as a pier scour countermeasure are reported. Sacrificial piles, which previous studies have shown to result in significant scour depth reductions under clear-water conditions, were found to be rather less effective under live-bed conditions due to the passage of bed forms. Sacrificial piles are not recommended unless the flow remains aligned and the flow intensity is relatively small. 相似文献
960.