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41.
On the phospholipids of Bacillus megaterium 总被引:12,自引:0,他引:12
42.
43.
Phylogenetic screening of the human genome: identification of differentially hybridizing repetitive sequence families 总被引:1,自引:0,他引:1
The phi-screen, a method of phylogenetic screening, can be employed to
detect repetitive sequence families that differentially hybridize between
closely related species. Such differences may involve sequence divergence
or variations in copy number, including total presence versus absence of a
family of repeated DNA. We present the results of a phi-screen comparing
the human genome to that of the prosimian, Galago crassicaudatus. Three
human repetitive families that are divergent or not present in galago have
been detected. One of these families is described in detail; it is similar
among the anthropoids but is present in a lower copy number and/or
divergent form in prosimians. The family is clearly related to the
transposon-like human element (THE) described by Paulson et al. (1985).
THEs have long terminal repeats reminiscent of retroviruses but are unique
in that they have no sequence similarity to known mammalian retroviruses.
The sequence of a solo long terminal repeat, found unassociated with THE
internal sequence, is presented. This family member, THE p2, is bordered by
a 5-bp target-site repeat and is interrupted by the insertion of an Alu
element. A solo THE element sequenced by Wiginton et al. (1986) contains an
insertion of Alu at precisely the same position as does THE p2.
相似文献
44.
The alcohol dehydrogenase (Adh) region from five planitibia subgroup
species of Hawaiian picture-wing Drosophila has been cloned. A total of 15
kb of DNA in and around the Adh gene has been compared among the five
species. Genetic distances were calculated to determine evolutionary
relationships. These distances agree with previous distances determined by
protein polymorphism and DNA hybridization techniques and can be
interpreted in terms of specific island colonization and speciation
(founder) events over the past 5 Myr. Examination of the restriction maps
of the cloned Adh region from the five species shows many instances of
small deletions, insertion of a transposable element in D. heteroneura, and
the existence of a highly variable region on the 3' side of the Adh gene.
Clustering relationships and rates of DNA change are calculated and
compared with the relationship found for other species of Drosophila.
相似文献
45.
J J Fernández-Ruiz C Agrasal M Cebeira J A Tresguerres A I Esquifino J A Ramos 《Revista Espanola de Fisiología》1988,44(2):205-210
The existence of local mechanisms controlling the prolactin (PRL) release from anterior pituitaries (AP) grafted to an ectopic location has been recently described. To study if these mechanisms are affected by estrogens, pituitary-grafted (GRAFT) and sham-operated (SHAM) rats were injected with a single dose of estradiol benzoate (EB), their plasma PRL levels as well as their hypothalamic and AP contents of norepinephrine (NE) and dopamine (DA) being analyzed. Administration of EB to GRAFT animals produced a small increase in their previously high plasma PRL levels, with both an increased NE and a decreased DA content in the ectopic AP. Since NE enhances the PRL release from ectopic AP and DA partially inhibits this secretion these changes may explain such a small increase in PRL levels. However, an additional increase in the decreased PRL release from the in situ AP of these animals cannot be discarded since EB produced also a decrease of the DA content in this tissue with an unaltered hypothalamic content. Finally, administration of this steroid to SHAM animals produced an important increase in plasma PRL levels. Since this increase was correlative to a decrease in DA and NE hypothalamic contents and unaltered AP contents. EB may be supposed to be able to reduce the DA synthesis in the tuberoinfundibular neurons, while the changes in noradrenergic inputs could be more related to the feedback effects of estrogens on the gonadotrophin release. 相似文献
46.
Effects of estrogens and progesterone on the catecholaminergic activity of the adrenal medulla in female rats 总被引:3,自引:0,他引:3
J J Fernández-Ruiz A R Bukhari R Martínez-Arrieta J A Tresguerres J A Ramos 《Life sciences》1988,42(9):1019-1028
Some reports in the literature allow to suspect the existence of an effect of sexual steroids on the adrenal catecholamines. To test this possibility, we have examined the catecholaminergic activity in the adrenal medulla of normal cycling rats in three phases of estrous cycle and of ovariectomized (OVX) rats injected with pharmacological doses of estradiol (ES), 2-hydroxyestradiol (HE) and/or progesterone (P). Adrenomedullary content of norepinephrine (NE) was similar during the estrous cycle, while epinephrine (E) content was increased during diestrous. This increase was concomitant with an increased phenylethanolamine-N-methyltransferase (PNMT) activity. Moreover, the monoamine oxidase (MAO) activity was significantly increased during proestrous, while the catechol-O-methyltransferase (COMT) activity was significantly decreased during estrous. In addition to these observations, ovariectomy caused a significant reduction of the E/NE ratio and of COMT and MAO activities. Administration of ES to OVX rats increased the E content, the E/NE ratio and the COMT activity as compared to vehicle-treated OVX rats. Administration of P to OVX animals led also to a significant increase of the E/NE ratio and of the COMT activity but not of the E content, while the administration of this steroid to OVX rats previously treated with ES only increased the COMT activity. Finally, administration of HE caused non-significant changes in NE and E contents and in MAO, COMT and PNMT activities. We can conclude that sexual steroids seem to be able to modify the catecholamine metabolism in the adrenal medulla and, hence, they could alter the ability of this gland to store and release these amines. 相似文献
47.
A double antibody radioimmunoassay in estudied for the determination of PGF2alpha. Its sensitivity allows to detect 0.4 ng. The reproductibility in this assays is of 7.8 % while between assays is of 10.7 %. No detectable levels (less than 0.8 ng/ml) could be found on blood obtained from the right heart chambers during the menstrual cycle, but they were measured in peripheral blood during normal deliveries. Changes on PGF2alpha concentrations occur in the endometrium along the menstrual cycle. Tis is a relatively simple method useful either for farmocodinamical studies when administering PGF2alpha or for physiological work with tissure showing relatively high concentrations of this compound. 相似文献
48.
Wagner Vital Gustavo Lazzaro Rezende Leonardo Abreu Jorge Moraes Francisco JA Lemos Itabajara da Silva VazJr Carlos Logullo 《BMC developmental biology》2010,10(1):25
Background
The mosquito A. aegypti is vector of dengue and other viruses. New methods of vector control are needed and can be achieved by a better understanding of the life cycle of this insect. Embryogenesis is a part of A. aegypty life cycle that is poorly understood. In insects in general and in mosquitoes in particular energetic metabolism is well studied during oogenesis, when the oocyte exhibits fast growth, accumulating carbohydrates, lipids and proteins that will meet the regulatory and metabolic needs of the developing embryo. On the other hand, events related with energetic metabolism during A. aegypti embryogenesis are unknown. 相似文献49.
目的 制备一种新型的心肌急性缺血再灌注损伤模型,以探讨一种更符合临床实际需求的实验方法.方法 将20只雌性SD(Sprague-Dawley)大鼠随机分成2组(对照组、实验组),采用结扎主动脉根部引起心肌缺血5min再灌注30 min建立心肌急性缺血再灌注模型;通过应用透射电镜观察心肌细胞超微结构的改变,同时检测心肌组织匀浆丙二醛(Maleic Dialdehyde,MDA)含量、超氧化物歧化酶(Superoxide Dismutase,SOD)活力.结果 透射电镜下超微结构显示实验组较对照组明显加重了心肌组织结构和线粒体的损害;实验组心肌组织MDA明显高于对照组(P<0.01),而SOD明显低于对照组(P<0.01).结论 本实验成功建立了方法简便、易于操作、取材范围广泛的心肌缺血再灌注损伤模型,为心肌缺血再灌注损伤研究提供了一种更为可行的模型. 相似文献
50.
Pérez Analía Fernanda Calvo Jorge Tresguerres Martín Luquet Carlos 《Polar Biology》2003,26(12):800-805
We investigated the renal morphology, histology and ultrastructure of Harpagifer bispinis, as a first step toward understanding the morpho-functional basis of its adaptation to potentially freezing brackish seawater. Fish were separated into two groups of ten individuals each, and acclimated to 2 and 38 salinity. A study of complete serial sections of the kidney revealed that the nephrons were aglomerular. At the highly convoluted proximal segment two different regions were evident, a feature that has not been previously reported for other aglomerular species. In electron photomicrographs we distinguished light and dark cells in the proximal tubule epithelium, with highly infolded basolateral membranes and closely associated mitochondria. The dark cells also had a large number of mitochondria in the apical region. The intercellular spaces at the epithelium of the proximal tubule were larger in fish acclimated at 2 salinity, a modification that might facilitate urine secretion, thus contributing to the survival of an aglomerular fish in a hyposmotic medium. 相似文献