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991.
Koichi Harazono Yoshio Watanabe Takema Fukatsu Ryuichiro Kurane 《Current microbiology》2003,47(3):0250-0254
Abstract:In the presence of polyunsaturated fatty acids, including cis-4,7,10,13,16,19-docosahexaenoic acid (DHA), 2,7-dichlorodibenzo-p-dioxin (DCDD) was treated with manganese peroxidase (MnP) from white rot basidiomycete Phanerochaete sordida YK-624. After incubation with MnP, DCDD could not be extracted from the reaction mixture with n-hexane and was trapped in the water layer. DCDD was released by alkalification of the water layer. DCDD was also trapped after treatment with lipoxidase, which produces hydroperoxides from unsaturated lipids. The amounts of thiobarbituric acid-reactive substances produced in the MnP reactions with three highly unsaturated fatty acids were higher than the amounts produced with three fatty acids with a lower degree of unsaturation. These results suggest that a DCDD-trapping compound may be produced by peroxidation of the polyunsaturated fatty acids.Received: 22 October 2002 / Accepted: 6 December 2002 相似文献
992.
A light in multidrug resistance: Photodynamic treatment of multidrug-resistant tumors 总被引:4,自引:0,他引:4
The major drawback of cancer chemotherapy is the development of multidrug-resistant (MDR) tumor cells, which are cross-resistant to a broad range of structurally and functionally unrelated agents, making it difficult to treat these tumors. In the last decade, a number of authors have studied the effects of photodynamic therapy (PDT), a combination of visible light with photosensitizing agents, on MDR cells. The results, although still inconclusive, have raised the possibility of treating MDR tumors by PDT. This review examines the growing literature concerning the responses of MDR cells to PDT, while stressing the need for the development of new photosensitizers that possess the necessary characteristics for the photodynamic treatment of this class of tumor. 相似文献
993.
In this study, we used a random approach to determine which amino acid pairs in human coagulation factor IX precursor are more sensitive to its 99 variants. The results show that the randomly unpredictable amino acid pairs are more sensitive to variants. 相似文献
994.
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996.
Khanna S Venojarvi M Roy S Sharma N Trikha P Bagchi D Bagchi M Sen CK 《Free radical biology & medicine》2002,33(8):1089-1096
997.
Cabatingan MS Schmidt MR Sen R Woodland RT 《Journal of immunology (Baltimore, Md. : 1950)》2002,169(12):6795-6805
998.
Ribonucleotide reduction is the only known biological means for de novo production of deoxyribonucleotides, the building blocks of DNA. These are produced from ribonucleotides, the building blocks
of RNA, and the direction of this reaction has been taken to support the idea that, in evolution, RNA preceded DNA as genetic
material. However, an understanding of the evolutionary relationships among the three modern-day classes of ribonucleotide
reductase and how the first reductase arose early in evolution is still far off. We propose that the diversification of this
class of enzymes is inherently tied to microbial colonization of aerobic and anaerobic niches. The work is of broader interest,
as it also sheds light on the process of adaptation to oxygenic environments consequent to the evolution of atmospheric oxygen. 相似文献
999.
Dragoi V 《Biological cybernetics》2002,86(6):419-426
Simple exposure to repeatitive stimulation is known to induce short-term learning effects across a wide range of species.
These effects can be both suppressive and facilitatory depending on stimulus conditions: repeatitive presentation of a weak
stimulus decreases the strength of the response (habituation), whereas presentation of a tonic stimulus following a series
of weak stimuli transiently increases the response strength (dishabituation). Although these phenomena have been comprehensively
characterized at both behavioral and cellular levels, most existing models of nonassociative learning focus exclusively on
the suppressive or facilitatory changes in response, and do not attempt to relate cellular events to behavior. I propose here
a feedforward model of habituation effects that explains both suppressive and facilitatory changes in response relying on
the interaction between excitatory and inhibitory processes that develop in parallel on two different timescales. The model's
properties are used to explain the rate sensitivity property of habituation and recovery and stimulus dishabituation.
Received: 1 June 2001 / Accepted in revised form: 4 December 2001 相似文献
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