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991.
Tibor Hartel 《Biologia》2008,63(3):439-443
This study presents long-term fluctuation, within pond distribution and mortality of egg masses in a population of Rana dalmatina reproducing in a permanent semi-natural pond in Romania. The average number of egg masses per year was 410 (SD = 114.56,
min.-max. = 265–581). The mean spawning duration (days) was 26.72 (SD = 5.53). The egg mass distribution was not constant
during the years. The long-term change in the distribution of egg masses can be related to changes in the reed cover (pond
variable) and landscape structure, i.e. the presence of the forest and a pasture between the pond and the forest. There was
a reduction in the number of dead egg masses during the study period. We suggest that the maintenance of the connectivity
with the forest and the variable amount of reed assure the main aquatic and terrestrial habitats for the agile frogs. This
will allow agile frogs to shift breeding habitats in this area according to their ecological needs and find safe terrestrial
habitats for summering and wintering. 相似文献
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Interactions between Carbon and Nitrogen Metabolism in Fibrobacter succinogenes S85: a 1H and 13C Nuclear Magnetic Resonance and Enzymatic Study 下载免费PDF全文
Christelle Matheron Anne-Marie Delort Genevieve Gaudet Tibor Liptaj Evelyne Forano 《Applied microbiology》1999,65(5):1941-1948
The effect of the presence of ammonia on [1-13C]glucose metabolism in the rumen fibrolytic bacterium Fibrobacter succinogenes S85 was studied by 13C and 1H nuclear magnetic resonance (NMR). Ammonia halved the level of glycogen storage and increased the rate of glucose conversion into acetate and succinate 2.2-fold and 1.4-fold, respectively, reducing the succinate-to-acetate ratio. The 13C enrichment of succinate and acetate was precisely quantified by 13C-filtered spin-echo difference 1H-NMR spectroscopy. The presence of ammonia did not modify the 13C enrichment of succinate C-2 (without ammonia, 20.8%, and with ammonia, 21.6%), indicating that the isotopic dilution of metabolites due to utilization of endogenous glycogen was not affected. In contrast, the presence of ammonia markedly decreased the 13C enrichment of acetate C-2 (from 40 to 31%), reflecting enhanced reversal of the succinate synthesis pathway. The reversal of glycolysis was unaffected by the presence of ammonia as shown by 13C-NMR analysis. Study of cell extracts showed that the main pathways of ammonia assimilation in F. succinogenes were glutamate dehydrogenase and alanine dehydrogenase. Glutamine synthetase activity was not detected. Glutamate dehydrogenase was active with both NAD and NADP as cofactors and was not repressed under ammonia limitation in the culture. Glutamate-pyruvate and glutamate-oxaloacetate transaminase activities were evidenced by spectrophotometry and 1H NMR. When cells were incubated in vivo with [1-13C]glucose, only 13C-labeled aspartate, glutamate, alanine, and valine were detected. Their labelings were consistent with the proposed amino acid synthesis pathway and with the reversal of the succinate synthesis pathway. 相似文献
994.
J. A. Werner Stefan Gottschlich Benedikt J. Folz Tibor Goeroegh Burkard M. Lippert J.-D. Maass Heinrich Rudert 《Cancer immunology, immunotherapy : CII》1997,44(2):112-116
p53 antibodies are a new serological parameter of unknown potential in patients with malignancies. Their occurrence has been
described in various types of cancer patients. The mechanism underlying the immunization process is still unclear. We investigated
the incidence of p53 serum antibodies in 143 head and neck cancer patients with an enzyme-linked immunosorbent assay. The
post-therapy course of two matched study groups (n = 38 each), one p53-antibody-seropositive and one p53-antibody-seronegative, was followed up for 24 months. Thirty-nine head
and neck cancer patients (27.3%) were seropositive for p53 antibodies. During the follow-up, the p53-antibody-seropositive
patients accounted for more local tumor recurrences (n = 12 versus n = 8) and more tumor-related deaths (n = 11 versus n = 5) than did seronegative patients, and second primary tumors (n = 9 versus n = 0) occurred exclusively in seropositive patients. In total, therapy failures (recurrences, tumor-related deaths,
second primaries) were observed in 17/38 cases (44.7%) in the p53-antibody-seropositive group and in 8/38 cases (21.1%) in
the p53-antibody-seronegative group. These results, after a follow-up of 2 years, seem to indicate a prognostic value of p53
serum antibodies for therapy failure in patients with head and neck cancer.
Received: 5 December 1996 / Accepted: 4 January 1997 相似文献
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Although the contribution of community members to functional diversity is a key question of conservation ecology, its measurement and interpretation are rather problematic. In this paper, we suggest a novel method for decomposing functional diversity. To do this we consider functional units (i.e. species or a group of species with identical traits) as the functional building blocks of communities. Then we propose the use of a recently developed measure of functional diversity (called modified functional attribute diversity or MFAD) and suggest additive decomposition of MFAD into functional values contributed by the functional units. We point out that functional values are related to changes in MFAD if the functional unit is removed from the community. This property of decomposition allows the quantification of the contribution of community members to functional diversity. By studying artificial and actual communities we compare the performance of our new method with other recently developed contribution measures, which are based on dendrograms and ordinations. Both theoretical considerations and analyses of artificial and actual data sets suggest that the proposed method of calculating functional values expresses more explicitly the contribution of community members to functional diversity and hereby can be used as a simple, yet efficient method for searching for functional keystones in ecological communities or for quantifying the contribution of community members to functional diversity. 相似文献
1000.
We construct a tractable model to describe the rate at which a knotted polymer is ejected from a spherical capsid via a small pore. Knots are too large to fit through the pore and must reptate to the end of the polymer for ejection to occur. The reptation of knots is described by symmetric exclusion on the line, with the internal capsid pressure represented by an additional biased particle that drives knots to the end of the chain. We compute the exact ejection speed for a finite number of knots L and find that it scales as 1/L. We establish a mapping to the solvable zero-range process. We also construct a continuum theory for many knots that matches the exact discrete theory for large L. 相似文献