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181.
P. R. Y. Backwell MD . Jennions J. H. Christy & N. I. Passmore 《Ethology : formerly Zeitschrift fur Tierpsychologie》1999,105(5):415-421
In the fiddler crab, Uca annulipes, males attract receptive females into their burrows by waving their greatly enlarged major claw. We have previously shown that males clustered around a female wave in close synchrony. Females may have a preference for leading signals and synchronised waving may arise as an epiphenomenon of competition between males to signal first. Indeed, the males in clusters that females approach and visit in their burrows are more likely to produce leading waves than are their neighbours. Here we document two other differences in the waving behaviour of visited males and their neighbours. First, visited males complete the downward component of the wave more rapidly than their neighbours. Second, the interval between the end of one wave and the start of the next is shorter for visited males. How can waving be synchronous if visited males wave faster than their neighbours? While only 9% (40/431) of waves by neighbours did not overlap those of the visited male, 22% (110/501) of visited male waves did not overlap the wave of a focal neighbour (111 visited male-neighbour dyads). Hence, while overlapping waves are nearly synchronous, visited males produce additional, ‘nonoverlapping’ waves that result in a higher wave rate than that of their neighbours. 相似文献
182.
Photosynthetic activity of developing leaves of Zea mays is less affected by heat stress than that of developed leaves 总被引:9,自引:0,他引:9
Various physiological and biochemical characters of a leaf change with stages of its ontogeny. It is likely that the photosynthetic functions of leaves of different ontogeny have different levels of heat tolerance. This study was initiated to analyze the photosynthetic heat tolerance of fully-developed, nearly-developed (more than 2/3 expanded) and developing (10–12 cm visible) leaves of two maize genotypes, F223 and F250. The results indicate that the photosynthetic CO2 assimilation rate (Pn ) of developing leaves was less affected by heat stress (42°C in the dark for 90 min) than that of developed leaves. The impaired Pn recovered within 24 h in the developing leaves, while the Pn of developed and nearly-developed leaves did not reach the non-stress level, even after 72 h. The Pn of the developed leaves of genotype F250 was less affected by heat stress than that of genotype F223. After heat stress, the slightly affected Pn of the developing leaf was associated with the almost unchanged photochemical efficiency of photosystem II (Fv /Fm ) and the quantum yield of photosystem II electron transport. The chlorophylls a and b were degraded by heat stress; the degradation was pronounced in the developed leaves. As a result of heat stress, the antheraxanthin and zeaxanthin of the xanthophyll cycle accumulated in both the nearly-developed and developed leaves but not in the developing leaves. Injury to the plasma membrane due to heat stress was much less severe in developing leaves than that in the developed leaves. From the physiological characters which we determined it would appear that the Pn functions of the developing leaves are more resistant to heat stress than those of nearly-developed and developed leaves. 相似文献
183.
A Weil 《Cellular and molecular biology, including cyto-enzymology》2001,47(8):1343-1351
Whatever their own policies may be, developing countries will inevitably be affected by the development of genetically-modified organisms in industrialized countries. While maintaining a cautious attitude, most of these countries wish to keep their options open, thus protecting themselves from the risk of being deprived of future technologies that might allow them to achieve self-sufficiency in food production, to resolve certain problems confronting their most vulnerable populations and to preserve the international competitiveness of their products. Companies should see that it is in their interest to help these countries implement their own policies, notably through an open attitude to industrial property. If the value of genetic engineering is thus confirmed, then it perhaps in this manner that GMOs will earn the legitimacy required to make them acceptable to the people of Northern countries where the majority of solvent markets are located. 相似文献
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187.
C. Jacquillat M. Weil M. F. Gemon V. Izrael G. Schaison M. Boiron Jean Bernard 《BMJ (Clinical research ed.)》1972,4(5838):468-469
Fourty-four patients with acute myeloblastic leukaemia were treated with RP 22050, a new, semisynthetic derivative of daunorubicin. Complete remissions were achieved in 20 patients (45%). The median dose given was 23 mg/kg. The toxicity of RP 22050 is mainly haematological. Resistance rather than death in aplasia seemed to be the cause of failure of therapy. 相似文献
188.
Incorporation of methionine from met-tRNA-Met-F into internal positions of polypeptides by mouse liver polysomes 总被引:2,自引:0,他引:2
J. DrewsG. Högenauer F. UngerR. Weil 《Biochemical and biophysical research communications》1971,43(4):905-912
Two methionine accepting tRNA species corresponding to tRNAFMet and tRNAMMet from mouse ascites tumor cells were tested for their ability to donate methionine into internal positions of growing polypeptide chains on mouse liver polysomes. Both tRNA species can function in the elongation of polypeptide chains as judged by their ability to incorporate methionine into protein in the absence of chain initiation. The insertion of methionine into internal positions of polypeptide chains from Met-tRNAFMet was confirmed by Edman degradation and CNBr cleavage. When both tRNAMet species were present in saturating concentrations in the cell-free system a strong preference for the incorporation of methionine from Met-tRNAMMet became apparent. 相似文献
189.
Polyoma Viral DNA Replicated as a Nucleoprotein Complex in Close Association with the Host Cell Chromatin 总被引:17,自引:10,他引:7
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Polyoma viral DNA is shown to be replicated in close association with the mouse cell chromatin. Two virus-specific nucleoprotein complexes, designated complex A and B, can be dissociated from the isolated chromatin by gentle homogenization in 0.5 M NaCl. Complex A contains only replicating polyoma (Py) DNA whereas complex B contains only mature Py DNA I. The results show, furthermore, that complex A, containing viral DNA in different stages of replication, and complex B are both nucleoproteins with the same buoyant density. The data presently available suggest that newly synthesized stretches of Py DNA are immediately complexed with mouse cell histones and that complex B becomes the "core" of progeny Py virions. These results suggested that Py-induced replication of the mouse cell chromatin may be necessary to provide replicating Py DNA with histones. 相似文献
190.