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391.
392.
Although the technique of intracytoplasmic sperm injection (ICSI) has been a revolution in the alleviation of male infertility, the use of testicular sperm for ICSI was a formerly unseen breakthrough in the treatment of the azoospermic man with primary testicular failure. At the clinical level, different procedures of testicular sperm retrieval (conventional TESE, micro-TESE, FNA/TESA, MESA, PESA) are being performed, the choice is mainly based on the cause of azoospermia (obstructive versus non-obstructive) and the surgeon’s skills. At the level of the IVF laboratory, mechanical procedures to harvest the sperm from the tissue may be combined with enzymatic treatment in order to increase the sperm recovery rates. A number of techniques have been developed for viable sperm selection in males with only immotile testicular sperm available. However, large, well-designed studies on the benefit and safety of one over the other technique are lacking. Despite all the available methods and combinations of laboratory procedures which have a common goal to maximize sperm recovery from testicular samples, a large proportion of NOA patients fail to father a genetically own child. Advanced technology application may improve recovery rates by detection of the testicular foci with active spermatogenesis and/or identification of the rare individual sperm in the testicular suspensions. On the other hand, in vitro spermatogenesis or sperm production from embryonic stem cells or induced pluripotent stem cells might be future options. The present review summarizes the available strategies which aim to maximize sperm recovery from surgically retrieved samples. 相似文献
393.
Greta Limoni Sahana Murthy Denis Jabaudon Alexandre Dayer Mathieu Niquille 《Cell reports》2021,34(4):108644
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394.
Abstract The temperature profiles have been determined for O2 reduction by activating substrates for whole cells and cell extracts of the psychrophilic, obligately anaerobic bacterium, strain B6, belonging to the Bacteroidaceae. The profiles were similar whether the cells were grown at 15 or 1°C, and also for cells harvested in the exponential or stationary phase. The H2 O producing pyruvate oxidase displayed in cell-free extracts a considerably higher activity than the H2 O2 producing NADH and NADPH oxidases at all temperatures in the range 30–1°C, and characteristically makes up a larger proportion of the total O2 reduction capacity the lower the temperature. It thus seems that the O2 scavenging property of the pyruvate oxidase, postulated to be utilized in a defense mechanism against the detrimental effects of the H2 O2 producing pyridine nucleotide oxidases, is particularly well adapted to function at the low temperatures of the Barents Sea, from which this obligately anaerobic organism originates. 相似文献
395.
Nelson Holly V. Frankham Greta J. Leo Viyanna Anson Jennifer R. Eldridge Mark D. B. de Bruyn Mark 《Conservation Genetics》2021,22(5):745-756
Conservation Genetics - Wildlife species impacted by habitat loss and fragmentation often require conservation efforts to maintain populations. Long-nosed bandicoots (Perameles nasuta) still... 相似文献
396.
Mitchell J. Eaton Greta L. Meyers Sergios-Orestis Kolokotronis Matthew S. Leslie Andrew P. Martin George Amato 《Conservation Genetics》2010,11(4):1389-1404
The creation and use of a globally available database of DNA sequences from a standardized gene region has been proposed as
a tool for species identification, assessing genetic diversity and monitoring the legal and illegal trade in wildlife species.
Here, we contribute to the Barcode of Life Data System and test whether a short region of the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene would reliably distinguish among a suite of commonly hunted African and South American mammal and reptile species.
We used universal primers to generate reference barcode sequences of 645 bp for 23 species from five vertebrate families (Crocodilidae, Alligatoridae, Bovidae, Suidae and Cercopithecidae). Primer cocktails yielded high quality barcode sequences for 179 out of 204 samples (87.7%) from all species included in
the study. For most taxa, we sequenced multiple individuals to estimate intraspecific sequence variability and document fixed
diagnostic characters for species identification. Polymorphism in the COX1 fragment was generally low (mean = 0.24%), while differences between congeneric species averaged 9.77%. Both fixed character
differences and tree-based maximum likelihood distance methods unambiguously identified unknown and misidentified samples
with a high degree of certainty. Barcode sequences also differentiated among newly identified lineages of African crocodiles
and identified unusually high levels of genetic diversity in one species of African duiker. DNA barcoding offers promise as
an effective tool for monitoring poaching and commercial trade in endangered species, especially when investigating semi-processed
or morphologically indistinguishable wildlife products. We discuss additional benefits of barcoding to ecology and conservation. 相似文献
397.
Daniel M. Lajoie Sue A. Roberts Pamela A. Zobel-Thropp Jared L. Delahaye Vahe Bandarian Greta J. Binford Matthew H. J. Cordes 《The Journal of biological chemistry》2015,290(17):10994-11007
Venoms of the sicariid spiders contain phospholipase D enzyme toxins that can cause severe dermonecrosis and even death in humans. These enzymes convert sphingolipid and lysolipid substrates to cyclic phosphates by activating a hydroxyl nucleophile present in both classes of lipid. The most medically relevant substrates are thought to be sphingomyelin and/or lysophosphatidylcholine. To better understand the substrate preference of these toxins, we used 31P NMR to compare the activity of three related but phylogenetically diverse sicariid toxins against a diverse panel of sphingolipid and lysolipid substrates. Two of the three showed significantly faster turnover of sphingolipids over lysolipids, and all three showed a strong preference for positively charged (choline and/or ethanolamine) over neutral (glycerol and serine) headgroups. Strikingly, however, the enzymes vary widely in their preference for choline, the headgroup of both sphingomyelin and lysophosphatidylcholine, versus ethanolamine. An enzyme from Sicarius terrosus showed a strong preference for ethanolamine over choline, whereas two paralogous enzymes from Loxosceles arizonica either preferred choline or showed no significant preference. Intrigued by the novel substrate preference of the Sicarius enzyme, we solved its crystal structure at 2.1 Å resolution. The evolution of variable substrate specificity may help explain the reduced dermonecrotic potential of some natural toxin variants, because mammalian sphingolipids use primarily choline as a positively charged headgroup; it may also be relevant for sicariid predatory behavior, because ethanolamine-containing sphingolipids are common in insect prey. 相似文献
398.
Greta Hulting Margareta Flock Lars Frykberg Jonas Lannergård Jan-Ingmar Flock & Bengt Guss 《FEMS microbiology letters》2009,298(1):44-50
Streptococcus equi ssp. equi causes strangles, a highly contagious and serious disease in the upper respiratory tract of horses. Streptococcus equi ssp. zooepidemicus , another subspecies of this genus, is regarded as an opportunistic commensal in horses. The present study describes the characterization of two novel immunoglobulin G (IgG) endopeptidases of these subspecies, IdeE2 and IdeZ2. Both enzymes display sequence similarities with two previously characterized IgG endopeptidases, IdeE of S. equi ssp. equi and IdeZ of S. equi ssp. zooepidemicus . IdeE2 and IdeZ2 display high substrate-specificity in comparison with IdeE and IdeZ, as they both completely cleave horse IgG, while the activity against IgG from mouse, rabbit, cat, cow, sheep and goat is low or absent. The potential use of IdeE and IdeE2 as vaccine components was studied in a mouse infection model. In this vaccination and challenge study, both enzymes induced protection against S. equi ssp. equi infection. 相似文献
399.
In two previous studies influence of gonadal hormones on male—female interaction has been investigated. Interaction between pair-living cagemates and non-cagemates was compared. In the first study the animals met in direct paired encounters, and in the second study the tested animals had the choice of wiremesh-restricted contact with the cagemate or a non-cagemate. The present choice test involves direct contact with the animal chosen in a series of consecutive trials. The two incentive animals were again non-cagemate and the cagemate of the experimental animal. The males tested were intact or castrated. The females were tested in induced oestrus. The females tested with intact males showes a higher choice of the cagemate. This was also the case in castrated males. Intact males and females tested with castrated males showed no significant difference in their choice. Differences in the results and testing conditions of the present and the previous choice test allowing restricted contact are discussed. 相似文献
400.
We have confirmed the finding of Murray et al. [Lett Appl Microbiol 1: 63–65, 1985] that most of theBacillus brevis spores undergoing the gramicidin S-delayed outgrowth stage of germination are killed by gramicidin S, the antibiotic produced during sporulation. We found, however, that 1% of the population resists this suicidal event even when high concentrations of gramicidin S are added and outgrowth is further delayed. It is obviously this small fraction of the population which, at the end of the long outgrowth stage, develops into vegetative cells. Previous work indicates that this minor population is not genetically resistant to gramicidin S. We conclude that the long delay in germination outgrowth is brought about by two effects of gramicidin S: (1) killing; and (2) decreasing the rate of one or more of the cellular metabolic activities necessary for outgrowth. 相似文献