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531.
The recovery, after inhibition by u.v.-irradiation, of phytohaemagglutinin-stimulated DNA synthesis is impaired in lymphocytes from patients with multiple actinic keratoses (AK) compared to the recovery in lymphocytes from age-matched, control individuals. This shows that the reduced level (50%) of DNA repair activity in AK ceils is sufficiently different from that in normal cells to significantly affect cellular activity. 相似文献
532.
Work on the roles of excitable epithelia in hydromedusan behaviour is reviewed from the historical point of view. Of special
interest are cases where epithelial impulses excite or inhibit nerves. It is suggested that nerves running in the endoderm
canals as described in several species with excitable endodermal epithelia may function to convey excitation to nerves in
the ectoderm, but the precise pathways and mechanisms whereby epithelial depolarizations lead to the generation or suppression
of neurally mediated processes are still poorly understood. Recent work on feeding in Aglantha
digitaleshows a component (lip-flaring) that may be a version of the crumpling behaviour seen in other medusae. The pathways mediating
feeding and crumpling behaviours are reviewed. 相似文献
533.
Mackie C. O'Hara W. Scott McGraw Debbie Guatelli-Steinberg 《American journal of physical anthropology》2023,180(3):519-533
Objectives
Developmental defects of tooth enamel are associated with systemic physiological stress and have been linked to seasonal environmental factors such as rainfall, temperature, and fruit availability. Here, we evaluate whether linear enamel hypoplasia and accentuated perikymata occur with any cyclicity on lower canines and then whether cycles differ between Bornean and Sumatran orangutans.Materials and Methods
Epoxy casts of lower canines from Pongo abelii (n = 14) and P. pygmaeus (n = 33) were evaluated for perikymata and dental enamel defects. Individual developmental sequences (IDSs) were generated for each canine, tracking the position of each defect in the context of continuous perikymata (time). Autocorrelation, a form of time-series statistical analysis was run for each canine to identify whether any cyclicity of defect expression was discernable.Results
Autocorrelation revealed cycles of defect expression within canines, but no common cycle periodicities were identified between individuals of the same species or across species. P. pygmaeus averaged more linear enamel hypoplasia per year than P. abelli, but no other comparisons (number of defects, number of perikymata between defects, and autocorrelation analysis) revealed differences between the species.Discussion
Although no common patterns of defect expression were identified within or between P. abelli and P. pygmaeus, the potential for autocorrelation analysis is promising for primatological and paleoanthropological studies of seasonal phenomena.534.
535.
Abstract. Simple cupular organs similar to those described in Ciona intestinalis were observed in Corella eumyota. They consist of a macula containing the cell bodies of 20–30 primary sensory neurons whose cilia project into a dome‐ or finger‐shaped structure, the cupula. Rather than being found in the mantle lining as in C. intestinalis, the organs were located on the atrial surface of the branchial sac. The sensory innervation was examined in whole‐mount preparations using anti‐tubulin immunohistochemistry. Sensory neurons in C. eumyota showed no immunoreactivity with antisera raised against gonadotropin‐releasing hormone (GnRH). A novel, elongated sense organ termed the cupular strand was found in Corella inflata. It has the same basic components as the simple type of cupular organ but consists of a single, long structure containing ~1500 sensory cells. Located on the atrial surface of the branchial sac, it extends along the midline of the dorsal fold, from the gonoduct openings almost as far as the brain. Preparations were examined using optical and electron microscopy. Nerves and cilia were visualized by anti‐tubulin immunofluorescence microscopy. It was possible to follow the sensory axons from the macula of the cupular strand to points where they joined branches of the visceral nerve, which enters a nerve root at the back of the brain. In C. inflata the sensory cell bodies and their axons were immunoreactive not only with anti‐tubulin but also with an antiserum raised against Tunicate I GnRH. There was no immunoreactivity, however, with Chicken II and catfish GnRH antisera. All three GnRH antisera labeled the dorsal strand plexus, a structure associated with production of GnRH in its role as a reproductive hormone. We concluded that the GnRH‐like molecule labeled in sensory neurons differs from the form of GnRH found in the dorsal strand plexus, and may have a different function, perhaps in the neural control of ciliary activity. The function of the cupular organs in species of Corella has not yet been investigated physiologically, but by analogy with such structures in other metazoans, cupular organs are probably hydrodynamic sensors registering local disturbances or changes in water flow through the atrial cavity. 相似文献
536.
B lymphocyte alloantigens in cattle were identified by serological analysis. Alloantisera were raised by skin implant immunization or leucocyte immunization and were absorbed with platelets to reduce class I-specific antibody activity. Leucocyte absorptions were done to reduce the complexity of some antisera. A panning technique was used to prepare B-enriched and B-depleted lymphocytes. Antisera which displayed anti-B cell activity over a number of dilutions were tested against 115 Charolais cattle, and 13 antisera were used to define five B lymphocyte alloantigens. These antigens were present on B lymphocytes but did not appear to be present, at least at the same density, on the majority of T lymphocytes or platelets. Family studies suggested that these antigens are coded by one or two loci which are closely linked to the bovine class I loci. These results suggest the five antigens are class II antigens of the major histocompatibility complex (MHC) of cattle. 相似文献
537.
At the August 1995 meeting of the General Council of the CMA, a resolution supporting school-based health promotion (comprehensive School Health) was adopted. This article briefly reviews the research supporting this integrated approach to school and community programs, applies the recommended approach to reducing tobacco use and outlines a role for physicians in promoting Comprehensive School Health in their communities. 相似文献
538.
539.
The objective of this study was to characterize the extracellular proteolytic activity of Streptococcus bovis. Strains KEG, JB1, NCFB 2476, and K11.21.09.6C produced very similar large molecular weight (160–200 kDa) extracellular proteases
that were specifically inhibited by PMSF, a serine protease inhibitor. Further experiments with S. bovis KEG indicated that cultures grown with casein as the sole added N source produced the greatest level of proteolytic activity,
and the level of proteolytic activity was independent of growth rate. Clarified ruminal fluid (CRF) decreased proteolytic
activity by 54% compared with cultures grown with casein alone, and addition of exogenous peptides and carbohydrates (CHO)
to the CRF further reduced the level of proteolytic activity by 44% and 52%, respectively. These results suggested that the
proteolytic activity of S. bovis KEG was modulated by available N source and that the proteolytic activity was present for reasons other than providing N
for growth. The role of S. bovis in ruminal proteolysis requires further definition, but phenotypic similarity among some ruminal strains would suggest a
common niche in ruminal proteolysis. The uniformity of proteolytic activities could make S. bovis a prime candidate for manipulation in ruminal proteolysis control strategies.
Received: 12 January 1999 / Accepted: 19 May 1999 相似文献
540.
C.J. Giffard S. Ladha A.R. Mackie D.C. Clark D. Sanders 《The Journal of membrane biology》1996,151(3):293-300
Nisin, a prominent member of the lantibiotic family of antimicrobial agents, has wide application as a food preservative despite
poor understanding of its mode of action. Fluorescence recovery after photobleaching has been used with planar lipid bilayers
as a model membrane system to examine how nisin might interact with the surface of bacterial cells. Nisin associates with
planar lipid bilayers in the absence of an applied membrane potential causing an array of effects consistent with adsorption
of nisin onto the membrane surface which involves inhibition of the lateral diffusion and fluorescence of the lipid probe
N-(7--1,2,3-benzoxadiazol-4-yl) phosphatidylethanolamine (NBD-PE) and a reduction of the capacitance of the bilayer. Nisin
adsorption is dependent on phospholipid composition. In the presence of dioleoylphosphatidylcholine (PC): cardiolipin (CL)
4:1, the rate of lateral mobility of phospholipid is reduced to 61% of the control level which decreases to a value of 46%
when CL is replaced by 1-palmitoyl-2-oleoylphosphatidylserine (PS). These effects on bilayer parameters are transient, and
with time the values return to near original levels. High electrical conductivity is observed on application of a voltage
ramp suggesting that insertion into the membrane follows surface association. Results have been interpreted in terms of a
model in which nisin initially binds to the surface of the membrane causing a modulation of bilayer properties.
Received: 14 August 1995/Revised: 22 February 1996 相似文献