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81.
Anthony J.Miller 《中国科学:生命科学英文版》2005,48(Z2)
As rice can use both nitrate (NO3-) and ammonium (NH4+), we have tested the hypothesis that the shift in the pattern of cultivars grown in Jiangsu Province reflects the ability of the plants to exploit NO3- as a nitrogen (N) source. Four rice cultivars were grown in solution culture for comparison of their growth on NO3- and NH4+ nitrogen sources. All four types of rice, Xian You 63 (XY63), Yang Dao 6 (YD), Nong Keng 57 (NK) and Si You 917 (SY917), grew well and produced similar amounts of shoot biomass with 1 mmol/L NH4+ as the only N source. However, the roots of NK were significantly smaller in comparison with the other cultivars. When supplied with 1 mmol/L NO3- YD produced the greatest biomass; while NK achieved the lowest growth among the four cultivars. Electrophysiological measurements on root rhizodermal cells showed that the NO3- elicited changes in membrane potential (△Em) of these four rice cultivars were significantly different when exposed to low external NO3- (<1 mmol/L); while they were very similar at high external NO3- (10 mmol/L). The root cell membrane potentials of YD and XY63 were more responsive to low external NO3- than those of NK and SY917. The△Em values for YD and XY63 rhizodermal cells were almost the same at both 0.1 mmol/L and 1 mmol/L NO3-; while for the NK and SY917 the values became larger as the external NO3- increased. For YD cultivar,△Em was measured over a range of NO3- concentrations and a Michaelis-Menten fit to the data gave a Km value of 0.17 mmol/L. Net NO3- uptake depletion kinetics were also compared and for some cultivars (YD and XY63) a single-phase uptake system with first order kinetics best fitted the data; while other cultivars (ND and SY917) showed a better fit to two uptake systems. These uptake systems had two affinity ranges: one had a similar Km in all the cultivars (0.2 mmol/L); the other much higher affinity system (0.03 mmol/L) was only present in NK and SY917. The expression pattern of twelve different NO3- transporter genes was tested using specific primers, but only OsNRT1.1 and OsNRT2.1 expression could be detected showing significant differences between the four rice cultivars. The results from both the physiological and molecular experiments do provide some support for the hypothesis that the more popular rice cultivars grown in Jiangsu Province may be better at using NO3- as an N source. 相似文献
82.
Pulmonary acariasis is a sporadic, incidental finding in colony‐raised rhesus macaques (Macaca mulatta). Prophylactic treatment in indoor‐raised and indoor‐housed macaques is not routine due to low prevalence, lack of clinical significance, and potential risk of toxicosis. This case is an unusually severe infestation of Pneumonyssus simicola in an indoor‐housed rhesus macaque, which ultimately resulted in this animal's death. 相似文献
83.
Freshwater crayfish invasions have been studied around the world, but less so in Africa, a continent devoid of native freshwater crayfish. The present study reviews historical and current information on alien freshwater crayfish species introduced into South Africa and aims to indicate which areas are at risk from invasion. As is the case elsewhere, South Africans have shown a keen interest in both farming and keeping freshwater crayfish as pets, which has resulted in Cherax cainii, Cherax destructor, Cherax quadricarinatus and Procambarus clarkii being introduced to the country. There is evidence of successful establishment in the wild for C. quadricarinatus and P. clarkii in different parts of the country. Species distribution models suggest that the eastern part of the country and parts of the Eastern and Western Cape are at higher risk of invasion. At present, illegal translocations represent the most likely pathway of crayfish spread in South Africa. A continued risk of invasion by freshwater crayfish species in South Africa is highlighted, which reinforces the need for more research, as well as for strong mitigation measures, such as stronger policing of existing regulations, management or eradication where feasible and public education. 相似文献
84.
85.
Global expression analysis of nucleotide binding site-leucine rich repeat-encoding and related genes in Arabidopsis 总被引:1,自引:0,他引:1
Xiaoping Tan Blake C Meyers Alexander Kozik Marilyn AL West Michele Morgante Dina A St Clair Andrew F Bent Richard W Michelmore 《BMC plant biology》2007,7(1):56
Background
Nucleotide binding site-leucine rich repeat (NBS-LRR)-encoding genes comprise the largest class of plant disease resistance genes. The 149 NBS-LRR-encoding genes and the 58 related genes that do not encode LRRs represent approximately 0.8% of all ORFs so far annotated in Arabidopsis ecotype Col-0. Despite their prevalence in the genome and functional importance, there was little information regarding expression of these genes. 相似文献86.
H?Bukulmez AL?Matthews CM?Sullivan C?Chen MJ?Kraay RC?Elston RW?Moskowitz VM?Goldberg ML?WarmanEmail author 《Arthritis research & therapy》2005,8(1):R25
In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA),
we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family
histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses
to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis
of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing
total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We
compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings
of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the
siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age
and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to
identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with
hip OA than in those with knee OA. 相似文献
87.
Rapid evolution of immunoglobulin superfamily C2 domains expressed in immune system cells 总被引:6,自引:3,他引:3
To test the hypothesis that proteins expressed in cells of the vertebrate
immune system evolve unusually rapidly, 107 orthologous immunoglobulin C2
domains were compared between human and murine rodent. The analysis showed
that the rate of nonsynonymous (amino-acid- altering) nucleotide
substitution in these domains was correlated with factors associated with
protein structure and with breadth of tissue expression, as well as with
the rate of synonymous substitution. However, when such factors were
controlled for statistically, there remained a strong positive association
between expression in the immune system and nonsynonymous rate, with the
highest rates being seen in genes expressed in the immune system only.
Certain immune system genes are known to be subject to positive selection
favoring diversity at the amino acid level; most of these genes encode
receptors that interact directly with foreign antigens. The observed
acceleration of the rate of nonsynonymous evolution in C2 domains of immune
system proteins may be explained by either (1) reduced constraint at the
amino acid level on molecules interacting with immune system receptors that
are themselves evolving rapidly due to positive diversifying selection or
(2) positive selection favoring amino acid changes correlated with changes
in the immune system receptors.
相似文献
88.
89.
Medical genetic study was carried out in the urban and rural populations of Kostroma Province. Urban populations were shown to have lower frequencies of "rare" forms of autosomal recessive diseases, in comparison with those in the rural populations. Analysis of interrelationship between genetical structure of populations and prevalencies of hereditary diseases in the populations revealed clear relations between the load of autosomal recessive diseases and the level of inbreeding in the populations. 相似文献
90.
Characterization of phosphorus fractions in the sediments of a tropical intertidal mangrove ecosystem 总被引:2,自引:0,他引:2
Solid phases of phosphorus fractions in the surface and core sediments were studied to understand the biogeochemical cycling
and bioavailability of phosphorus in the Pichavaram intertidal mangrove sediments of India. Total P in surface and core sediments
ranged between 451–552 and 459–736 μg g−1 respectively and Fe bound P was the dominant fraction. Low levels of Fe bound P in the mangrove zone than the two estuarine
zones may be because of high salinity inhibition of phosphate adsorption onto the Fe-oxides/hydroxides. Post-depositional
reorganization of P was observed in surface sediments, converting organic P and Fe bound P into the authigenic P. High levels
of organic P in the mangrove zone is primarily due to intensive cycling and degradation of organic matter and adsorption of
phosphate on the organic molecules. The burial rates and regeneration efficiency of P in the intertidal mangrove ecosystem
ranged from 5.41 to 7.27 μmol P cm−2 year−1 and 0.122 to 0.233 μmol P cm−2 year−1, respectively. High burial efficiency (≈99%) of P proves the earlier observation of limiting nature of P for the biological
productivity. Further, bioavailable P (exchangeable P + Fe bound P + organic P) constituted a considerable proportion of sedimentary
P pool of which an average accounted for 55 and 50% in surface and core sediments respectively. The results indicate that
significant amount of P is locked in sediments in the form of authigenic P and detrital P which makes P as a limiting nutrient
for the biological productivity. 相似文献