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181.
B van Ommen A Koster H Verhagen P J van Bladeren 《Biochemical and biophysical research communications》1992,189(1):309-314
The glutathione conjugates of tert-butyl hydroquinone, a metabolite of butylated hydroxyanisole (BHA), possess redox potentials which are much higher as compared to the non-conjugated hydroquinone (0.36 V for the hydroquinone and 1.2-1.4 V for the conjugates). As a result, the redox cycling activity of the conjugates, as measured by oxygen consumption in the presence of a reducing agent, is increased tenfold as compared to the non-conjugated hydroquinone. Since evidence for both oxidative damage and the involvement for glutathione in the toxicity of butylated hydroxyanisole is available, this mechanism may be involved in the toxic action of this compound. 相似文献
182.
Koster KL 《Plant physiology》1991,96(1):302-304
The formation of intracellular glass may help protect embryos from damage due to desiccation. Soluble sugars similar to those found in desiccation tolerant embryos were studied with differential scanning calorimetry. Those sugars from desiccation tolerant embryos can form glasses at ambient temperatures, whereas those from embryos that do not tolerate desiccation only form glasses at subzero temperatures. It is concluded that tolerant embryo cells probably contain sugar glasses at storage temperatures and water contents, but intolerant embryo cells probably do not. 相似文献
183.
Germ Layer Interactions in Pattern Formation of Amphibian Mesoderm during Primary Embryonic Induction 总被引:6,自引:6,他引:0
Mesodermal differentiation of dorsal marginal zone (DMZ) before and after invagination was analyzed by a series of combination experiments with different kinds of ectoderm.
Lower DMZ of early gastrula didn't show any axial-mesoderm (notochord and somitic mesoderm) but lateral mesoderm (mesenchyme, mesothelium, or blood cells) in combinant with non-competent ventral ectoderm, while combinant with competent ectoderm was found to have well-differentiated axial-mesoderm with deutero-spinocaudal neurals. The axial-mesoderms have origin in the ectoderm. Uninvaginated DMZ of middle gastrula also showed difference in mesodermal differentiation between competent and non-competent ectoderms; axial-mesoderm differentiation was much better in competent than in non-competent. The axial-mesoderm originated from the uninvaginated DMZ. Archenteron roof of late gastrula showed regional difference in mesodermal differentiation in both combinants with competent and non-competent. The present study further demonstrated that there was regionality in promoting effect of induced neurectoderm on axial-mesoderm differentiation of invaginated archenteron roof.
The present experiments suggest that the cranio-caudal and dorso-ventral axis formations of amphibian mesoderm are finally determined by sequential and reciprocal interactions between the mesodermal anlage and the overlying ectoderm. It should be also shown that lower DMZ acts to trigger a series of the sequential interactions during primary embryonic induction. 相似文献
Lower DMZ of early gastrula didn't show any axial-mesoderm (notochord and somitic mesoderm) but lateral mesoderm (mesenchyme, mesothelium, or blood cells) in combinant with non-competent ventral ectoderm, while combinant with competent ectoderm was found to have well-differentiated axial-mesoderm with deutero-spinocaudal neurals. The axial-mesoderms have origin in the ectoderm. Uninvaginated DMZ of middle gastrula also showed difference in mesodermal differentiation between competent and non-competent ectoderms; axial-mesoderm differentiation was much better in competent than in non-competent. The axial-mesoderm originated from the uninvaginated DMZ. Archenteron roof of late gastrula showed regional difference in mesodermal differentiation in both combinants with competent and non-competent. The present study further demonstrated that there was regionality in promoting effect of induced neurectoderm on axial-mesoderm differentiation of invaginated archenteron roof.
The present experiments suggest that the cranio-caudal and dorso-ventral axis formations of amphibian mesoderm are finally determined by sequential and reciprocal interactions between the mesodermal anlage and the overlying ectoderm. It should be also shown that lower DMZ acts to trigger a series of the sequential interactions during primary embryonic induction. 相似文献
184.
Evolution of the primary and secondary structures of the E1a mRNAs of the adenovirus 总被引:1,自引:0,他引:1
In this paper we investigate and compare (evolutionary) patterns in the
primary and secondary structure of four homologous E1a mRNAs of the
adenovirus. Our main results are as follows: (1) The similarity of the
coding regions of the mRNA sequences reflects both similarity in function
(i.e., oncogenicity) and evolutionary divergence. (2) The similarity of the
leader and the trailer regions reflects host specificity (i.e., human or
simian) and must therefore arise from convergence. (3) Minimal energy
foldings of the mRNAs show similar secondary structures (in particular
around the splice sites). The conservation of pre-mRNA secondary structure
shows that mRNAs are subject to selection constraints in addition to those
associated with proteins. (4) The conserved secondary (helical) structures
consist of nonhomologous subsequences, i.e., shifts have occurred. The
observed shifts near the splice sites seem to be the simplest way of
dealing with the dual constraints.
相似文献
185.
Complete sequences of the rRNA genes of Drosophila melanogaster 总被引:19,自引:0,他引:19
In this, the first of three papers, we present the sequence of the
ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of
D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S
(123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat
of D. melanogaster is AT rich (65.9% overall), with the spacers being
particularly AT rich. Analysis of DNA simplicity reveals that, in contrast
to the intergenic spacer (IGS) and the external transcribed spacer (ETS),
most of the rRNA gene regions have been refractory to the action of
slippage-like events, with the exception of the 28S rRNA gene expansion
segments. It would seem that the 28S rRNA can accommodate the products of
slippage-like events without loss of activity. In the following two papers
we analyze the effects of sequence divergence on the evolution of (1) the
28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary
structures among eukaryotic species, respectively. Our detailed analyses
reveal, in addition to unequal crossing-over, (1) the involvement of
slippage and biased mutation in the evolution of the rDNA multigene family
and (2) the molecular coevolution of both expansion segments and the
nucleotides involved with compensatory changes required to maintain
secondary structures of RNA.
相似文献
186.
Alterations in energy status by menadione metabolism in hepatocytes isolated from fasted and fed rats 总被引:2,自引:0,他引:2
F A Redegeld R M Moison A S Koster J Noordhoek 《Archives of biochemistry and biophysics》1989,273(1):215-222
The biochemical mechanism of cytotoxicity, induced by the quinoid compound 2-methyl 1,4-naphthoquinone (menadione), was investigated in hepatocytes freshly isolated from fasted and fed rats. Hepatocytes from fasted rats were significantly more vulnerable to the toxicity of menadione than hepatocytes from fed rats. Menadione (150 microM) induced a 50% loss of viability of cells (LT50) from fasted rats after 55 min of incubation, whereas a LT50 of 80 min was observed after exposure of hepatocytes from fed rats to menadione. Glutathione and NADPH levels were rapidly depleted by menadione metabolism. This depletion was sustained during the incubation period. No significant differences were found in the time course and extent of the menadione-induced glutathione and NADPH depletion in hepatocytes of both nutritional states. Menadione also affected the energy status of the hepatocytes. The ATP content of cells from fasted rats decreased to 50% (AT50) within 18 min of exposure to menadione, whereas a 50% loss of ATP content of hepatocytes from fed rats was reached at 65 min. In contrast to depletion of glutathione and NADPH, the time course and extent of menadione-induced ATP depletion correlated well with the time of onset and rate of cell killing. Our results suggest that menadione metabolism may interfere with both mitochondrial and glycolytic ATP production. Depletion of ATP might be a critical step in menadione-induced cytotoxicity. 相似文献
187.
Wayne M. Koster David R. Dawson Adrian Kitchingman Paul D. Moloney Robin Hale 《Journal of fish biology》2020,96(3):782-794
The construction of dams and weirs, and associated changes to hydrological and hydraulic (e.g., water level and velocity) characteristics of rivers is a key environmental threat for fish. These multiple stressors potentially can affect fish in a variety of ways, including by causing changes in their movement, habitat use and activity. Understanding how and why these changes occur can inform management efforts to ameliorate these threats. In this context, we used acoustic telemetry to examine habitat use, longitudinal movement and activity of two lowland river fishes, Murray cod Maccullochella peelii and golden perch Macquaria ambigua, in a weir pool environment in south-eastern Australia. We compared our results to published studies on riverine populations to determine if their behaviours are similar (or not). We show that M. peelii and M. ambigua in a weir pool exhibited some similar behaviours to conspecific riverine populations, such as strong site fidelity and use of woody habitat for M. ambigua. However, some behaviours, such as large-scale (tens–hundreds of kilometres) movements documented for riverine populations, were rarely observed. These differences potentially reflect flow regulation (e.g., stable water levels, loss of hydraulic cues) in the weir pool. The two species also exhibited contrasting responses to dissolved oxygen conditions in the weir pool, which may reflect differences in their life history. Overall, this study shows that although some aspects of these two native fishes' life history can continue despite flow regulation, other aspects may change in weir pools, potentially impacting on long-term population persistence. 相似文献
188.
A new species of Sabellaria is described from the southeast coast of Brazil and compared with related species known from South or North America. 相似文献
189.
190.