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41.
Binding of inorganic elements to kelp residues 总被引:1,自引:1,他引:0
42.
黑腹果蝇P转座因子研究 Ⅰ.我国黑腹果蝇的P-M测定及其地理分布 总被引:1,自引:0,他引:1
采用性腺败育(GD不育)作为标准检定方法。对我国20个地方的黑腹果蝇的P因子活性和细胞型进行了测定。结果表明我国北部沿海城市为Q型;南部沿海和内地皆为M型。各地的M品系所产生的GD不育能力各不相同,但表现出与地理位置相关的梯度变化。这一变化规律为研究我国黑腹果蝇的P因子起源及P和M品系的形成提供了重要的理论依据。 相似文献
43.
Nigel J. Robinson 《Journal of applied phycology》1989,1(1):5-18
Metallothioneins, MT's, are low-molecular-weight, cysteine-rich, polypeptides that complex ‘soft’ metal ions in thiol clusters.
They are structurally diverse. Some MT's are gene products, while others are secondary metabolites. Two of the three classes
of MT have been identified in algae. Eukaryotic algae possess the secondary metabolites referred to as class III MT. There
is no unequivocal evidence that MT genes occur in eukaryotic algae. However, the products of MT genes have been identified
in cyanobacteria. These genes and their metal regulatory elements remain to be isolated and characterized.
MT's have attracted interest from researchers involved in a wide range of disciplines including bioinorganic chemistry, biochemistry,
molecular biology, physiology, toxicology, environmental science and medicine. Although, the precise physiological roles of
these polypeptides remain undefined, a large number of functions have been speculated. These molecules chelate toxic trace
metals, such as Cd, thereby reducing the concentration of cytotoxic, free-metal ions. Furthermore, some MT's are believed
to be involved in zinc and copper homoeostasis. Future studies should reveal whether or not some of the diversity of MT structure
reflects a diversity of function. 相似文献
44.
Effect of cytoplasmic acidification on the membrane potential of T-lymphocytes: Role of trace metals
Summary The effect of lowering intracellular pH on the membrane potential (E
m
) of rat thymic lymphocytes was studied using the potential-sensitive dyebis-oxonol. Cells were acid loaded by addition of the electroneutral K+/H+ exchanging ionophore nigericin. Acidification to pH 6.3 in Na+-free solution resulted in a biphasic change inE
m
: an early transient hyperpolarization followed by a sustained depolarization. These changes were associated with a rise in cytosolic free Ca2+ ([Ca2+]
i
). The hyperpolarization was eliminated when the change in [Ca2+]
i
was prevented using BAPTA, an intracellular Ca2+ chelator. Moreover, a similar hyperpolarization was elicited by elevation of [Ca2+]
i
at physiological pH
i
using ionomycin, suggesting involvement of Ca2+-activated K+ channels. In contrast, the depolarization phase could not be mimicked by raising [Ca2+]
i
with ionomycin. However, intracellular BAPTA effectively inhibited the acidificationinduced depolarization. Inhibition was also obtained by extracellular addition of EGTA or dithiothreitol, even when the external free Ca2+ concentration remained unaltered. These observations suggested a possible role of contaminating trace metals. Cytosolic acidification is envisaged to induce intracellular accumulation of one or more trace metals, which induces the observed changes inE
m
. Accordingly, similar changes inE
m
can be induced without acidification by the addition of small amounts of Cu2+ to the medium. The ionic basis of theE
m
changes induced by acidification and the significance of these observations are discussed. 相似文献
45.
[3H]Spiperone ([3H]SPI) binding sites in rat or bovine striata have been solubilized using CHAPS or digitonin detergents. Solubilized sites retained the binding characteristics of those in native membrane preparations. The same solubilized material, however, did not bind [3H]tyramine ([3H]PTA), thus indicating that [3H]PTA binding sites and DA receptors are different chemico-physical entities. In membrane preparations or crude synaptosomes obtained from the c.striatum of neonatally-rendered hypothyroid rats, when central DA-pathways are impaired, both [3H]PTA binding and [3H]DA uptake processes were markedly decreased, with no effect on [3H]mazindol ([3H]MAZ) binding, compared to euthyroids. Reserpine, a well-known inhibitor of DA-uptake into a variety of secretory vesicles, and a potent in vivo andin vitro inhibitor of [3H]PTA binding, did not affect the [3H]MAZ binding process. This further supported the suggestion that while [3H]PTA binding sites are almost totally associated with the vesicular transporter for DA, [3H]MAZ does label a site involved in the DA-translocation across the neuronal membrane. The latter process seems to be rather insensitive to thyroid hypofunction, when however the intracellular storage of DA might be consistently impaired. In conclusion, PTA might be well exploited as a marker of the DA vesicular transporter through its molecular characterization, whenever possible.Special issue dedicated to Dr. Paola S. Timiras 相似文献
46.
A. J. Richards 《Plant Systematics and Evolution》1989,163(3-4):177-185
Morphological variation for the NOR chromosome was studied for four half-siblings of a sexual outbreedingTaraxacum, for three siblings of the obligate agamospermT. pseudohamatum, and for two individuals of the agamospermT. brachyglossum. No rearrangement was detected for the 113 chromosomes of sexuals, or for 41 chromosomes of two agamospermous individuals. In the other three agamospermous individuals, 3/16, 5/50, and 5/20 chromosomes showed evidence of chromosomal rearrangement. The majority of rearrangement events (10/13) occurred to the satellite rather than to the body of the NOR-chromosome. It is considered that such high levels of somatic chromosomal rearrangement in agamospermousTaraxacum may be the result of activity by transposable genetic elements. This recombination may be of selective advantage to asexual plants which cannot generate genetic variability through the sexual process. 相似文献
47.
48.
Michael F. Dowe Jr. Gregg W. Roman Anita S. Klein 《Molecular & general genetics : MGG》1990,221(3):475-485
Summary The regulatory mutation bronze mutable 4 Derivative 6856 (bz-m4 D6856) contains a complex 6.7 kb Dissociation (Ds) element tagged with a duplication of low copy bz 3 flanking sequences (Klein et al. 1988). This creates a unique opportunity to study the transposition of a single member of the repetitive family of Ds elements. Eighteen full purple revertants (Bz alleles) of bz-m4 were characterized enzymatically and by genomic mapping. For 17 of the Bz alleles, reversion to a wild-type phenotype was caused by excision of the 6.7 kb Ds transposon. Nine of these Bz alleles retained the transposon somewhere in their genome. In this study we show that like Ac (Schwartz 1989; Dooner and Belachew 1989), the 6.7 kb Ds element can transpose within a short physical distance, both proximal and distal to its original position. Additional bz sequences have been mapped immediately distal to the mutant locus in bz-m4 D6856; genetic evidence suggests these are flanked by two additional Ds elements. The remaining Bz revertant, Bz :107, arose from excision of a more complex 13 kb Ds element. 相似文献
49.
50.