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101.
Jinsong Zhang Chris Taylor Erich Bowman Leo Savage-Low Michael W. Lodewyk Larry Hanne Guang Wu 《Tetrahedron letters》2013
A process for synthesizing 1,4-benzodioxin, through oxidation of a phenol to an o-quinone followed by treatment with an enamine, has been developed. Adduct stereochemistry is found to be retained via this one-pot reaction. The method uses hypervalent iodine reagent under mild conditions and is compatible with a wide scope of phenols and enamines. 相似文献
102.
103.
Argon matrix photolysis of tetrazolo[1,5-a]quinoline 8 and tetrazolo[5,1-a]isoquinoline 7 causes nitrogen elimination and ring expansion to 1,3-diazabenzo[d]cyclohepta-1,2,4,6-tetraene 13. The photolysis of tetrazolo[5,1-a]isoquinoline 7 also causes ring opening to o-cyanophenylketenimine 22. Mechanisms of ring opening of heteroarylnitrenes are discussed. 相似文献
104.
The oxidation of polyunsaturated fatty acids such as arachidonic and linoleic acid initiates a plethora of cell signaling pathways in animals and plants. The chemistry of the enzymatic oxidation has been investigated for several enzymes, most notably prostaglandin synthase and the lipoxygenases, revealing many surprises and impressive examples of enzymatic control of hydrogen atom abstraction and subsequent oxygenation. 相似文献
105.
Liu C Walter D Neuhauser D Baer R 《Journal of the American Chemical Society》2003,125(46):13936-13937
Crown ethers have the remarkable property of recognizing and binding specific metal cations in complex mixtures. We propose to combine molecular recognition with molecular electric conductance. The question we address is: can the event of binding a cation be sensed by a change in conductance? Specifically, we study a short molecular wire (MW) containing a crown-6 molecule connected via sulfur atoms to two gold atomic wires acting as metallic leads. Upon binding a cation, the density of states of the system is only slightly affected. This reflects the fact that the cation binding is largely electrostatic in nature and is accompanied by little electronic reorganization. Yet, the cationic binding does significantly lower conductance. We also identify strong interference affecting the conductance. A striking feature is the insensitivity of conductance to the type of ligand with the exception of the proton. 相似文献
106.
Chambers C Smith F Williams C Marcos S Liu ZH Hayter P Ciaramella G Keighley W Gribbon P Sewing A 《Combinatorial chemistry & high throughput screening》2003,6(4):355-362
The measurement of intracellular calcium fluxes in real time is widely applied within the pharmaceutical industry to measure the activation of G-protein coupled receptors (GPCRhyp;s), either for pharmacological characterisation or to screen for new surrogate ligands. Initially restricted to G(q) coupled GPCRs, the introduction of promiscuous and chimeric G-proteins has further widened the application of these assays. The development of new calcium sensitive dyes and assays has provided sensitive, homogeneous assays which can be readily applied to high throughput screening (HTS). In this paper we describe the full automation of this assay type using a fluorometric imaging plate reader (FLIPR ) integrated into a Beckman/Sagian system to establish a simple robotic system that is well suited for the current medium throughput screening in this area of lead discovery. Using a recently completed HTS we discuss important determinants for FLIPR based screening, highlight some limitations of the current approach, and look at the requirements for future automated systems capable of keeping up with expanding compound files. 相似文献
107.
Wu G Irvine J Luft C Pressley D Hodge CN Janzen B 《Combinatorial chemistry & high throughput screening》2003,6(4):303-312
Caspase proteases are familiar targets in drug discovery. A common format for screening to identify caspase inhibitors employs fluorogenic or colorimetric tetra-peptide substrates in 96, 384, or 1536 -well microtiter plates. The primary motivation for increasing the number of wells per plate is to reduce the reagent cost per test and increase the throughput of HTS operations. There are significant challenges, however, to moving into or beyond the 1536-well format, such as submicroliter liquid handling, liquid evaporation, increased surface area-to-volume ratios, and the potential for artifacts and interference from small air-borne particles such as lint. Therefore, HTS scientists remain keenly interested in technologies that offer alternatives to the ever-shrinking microtiter plate well. Microfluidic assay technology represents an attractive option that, in theory, consumes only subnanoliter volumes of reagents per test. We have successfully employed a microfluidic assay technology in fluorogenic screening assays for several caspase isoforms utilizing the Caliper Technologies Labchip platform. Caspase-3 is used as a representative case to describe microfluidic assay development and initial high-throughput screening results. In addition, microfluidic screening and plate-based screening are compared in terms of reagent consumption, data quality, and ease of operation. 相似文献
108.
Sherif M. Hassan James A. Byrd Aubry L. Cartwright Chris A. Bailey 《Applied biochemistry and biotechnology》2010,162(4):1008-1017
Hemolytic and antibacterial activities of eight serial concentrations ranged from 5-666 µg/mL of saponin-rich extracts from guar meal (GM), quillaja, yucca, and soybean were tested in 96-well plates and read by enzyme-linked immunosorbent assay plate-well as 650 nm. Hemolytic assay used a 1% suspension of chicken red blood cells with water and phosphate buffered saline as positive and negative controls, respectively. Antibacterial activity against Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli were evaluated using ampicillin and bacteria without saponin-rich extract as positive and negative controls, respectively. The 100% MeOH GM and commercial quillaja saponin-rich extracts were significantly the highest in both hemolytic and antibacterial activities against all bacteria at the same concentration tested. Soybean saponin-rich extract had no antibacterial activity against any of the bacteria at the concentrations tested while yucca saponin-rich extract had no antibacterial activity against the gram-negative bacteria at the concentrations tested. GM and quillaja saponin-rich extracts were hemolytic, while yucca and soybean saponin-rich extracts were not hemolytic at the concentrations tested. No saponin-rich extract source had antibacterial activity against S. typhimurium or E. coli at the concentrations tested. Both GM and quillaja saponin-rich extracts exhibited antibacterial activity against S. aureus. Saponin-rich extracts from different plant sources have different hemolytic and antibacterial activities. 相似文献
109.
Anti-resonant reflecting optical waveguides (ARROW) are described which trap light in a low index layer between a lower, high-index confining layer and an upper total internal reflection boundary. In this configuration, most of the light (greater than 80%) travels in the low index porous polymer layer, the refractive index of which is monitored by examining the angle at which light is coupled out of the waveguide. It is shown that asymmetric ARROW sensors can be constructed using conventional chemical vapour deposition and spin-coating techniques and their sensitivity is as predicted by theoretical modelling. 相似文献
110.
Kate J. Graham Chris P. Schaller Brian J. Johnson John B. Klassen 《The Chemical Educator》2002,7(6):376-378
The incorporation of research projects into undergraduate chemistry courses provides a perspective that is fundamentally unavailable in most laboratory experiences. While independent, multistep synthesis projects in organic chemistry have been reported previously, most efforts have been directed at relatively restricted, closely guided research plans with modest student participation in the experimental design. We have implemented a more open-ended synthesis project, limited principally by cost, safety and availability of materials. In the second semester of the sophomore organic sequence, students develop multiple drafts of a plan for a three-to-four-step synthesis. Subsequently, students obtain their own literature protocols for the individual steps. The synthesis is performed over three four-hour laboratory periods. The students conclude this project with a poster presentation of the results at the end of the semester. Evaluation of the students work focuses not only on the successful synthesis of the target but also on planning, troubleshooting, purification, and spectral analysis. 相似文献