全文获取类型
收费全文 | 1363篇 |
免费 | 70篇 |
国内免费 | 1篇 |
出版年
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 49篇 |
2020年 | 24篇 |
2019年 | 25篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 39篇 |
2015年 | 77篇 |
2014年 | 86篇 |
2013年 | 99篇 |
2012年 | 101篇 |
2011年 | 139篇 |
2010年 | 82篇 |
2009年 | 65篇 |
2008年 | 94篇 |
2007年 | 94篇 |
2006年 | 71篇 |
2005年 | 53篇 |
2004年 | 51篇 |
2003年 | 53篇 |
2002年 | 33篇 |
2001年 | 15篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 11篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有1434条查询结果,搜索用时 62 毫秒
1.
M K Theodorou D J Gascoyne D E Akin R D Hartley 《Applied and environmental microbiology》1987,53(5):1046-1050
Information on the interaction between mixed populations in the rumen and plant phenolics is required to fully elucidate the limitations of phenolic compounds on forage digestibility. The objective of this study was to examine the degradation of Italian ryegrass (Lolium multiflorum L.) hay incubated with mixed ruminal populations in consecutive batch culture (CBC) with or without phenolic acids or phenolic compounds extracted from plant cell walls. Each CBC consisted of a series of 10 cultures (3 replicates per culture) inoculated (10%, vol/vol) in sequence at 48-h intervals with microbial suspension from the previous set of cultures. All cultures were grown on a semidefined medium containing Italian ryegrass hay, and each CBC was initiated with an inoculum from the rumen. Rumenlike fermentation characteristics were maintained in control CBCs by repeated inoculum transfer. Treatment CBCs were transferred as described above, but cultures 5, 6, and 7 were incubated in the presence of trans-p-coumaric, cis-p-coumaric, or trans-ferulic acid or phenolics extracted from the cell walls of maize stem or barley straw. Mean apparent dry matter disappearance in control CBC cultures was 495 mg per g of hay, whereas the presence of phenolics reduced the initial dry matter disappearance by 6.3 to 25.6%. trans-p-Coumaric acid and, to a lesser extent, the phenolics from cell walls of maize stem were the most inhibitory compounds for dry matter disappearance and for the production of volatile fatty acids; trans-p-coumaric acid altered the molar ratio of acetate/propionate/butyrate. The CBC further showed variations in the ability of the rumen microbial population to adapt to phenolic compounds. 相似文献
2.
Effect of phenolic acids and phenolics from plant cell walls on rumenlike fermentation in consecutive batch culture. 总被引:5,自引:3,他引:2
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Information on the interaction between mixed populations in the rumen and plant phenolics is required to fully elucidate the limitations of phenolic compounds on forage digestibility. The objective of this study was to examine the degradation of Italian ryegrass (Lolium multiflorum L.) hay incubated with mixed ruminal populations in consecutive batch culture (CBC) with or without phenolic acids or phenolic compounds extracted from plant cell walls. Each CBC consisted of a series of 10 cultures (3 replicates per culture) inoculated (10%, vol/vol) in sequence at 48-h intervals with microbial suspension from the previous set of cultures. All cultures were grown on a semidefined medium containing Italian ryegrass hay, and each CBC was initiated with an inoculum from the rumen. Rumenlike fermentation characteristics were maintained in control CBCs by repeated inoculum transfer. Treatment CBCs were transferred as described above, but cultures 5, 6, and 7 were incubated in the presence of trans-p-coumaric, cis-p-coumaric, or trans-ferulic acid or phenolics extracted from the cell walls of maize stem or barley straw. Mean apparent dry matter disappearance in control CBC cultures was 495 mg per g of hay, whereas the presence of phenolics reduced the initial dry matter disappearance by 6.3 to 25.6%. trans-p-Coumaric acid and, to a lesser extent, the phenolics from cell walls of maize stem were the most inhibitory compounds for dry matter disappearance and for the production of volatile fatty acids; trans-p-coumaric acid altered the molar ratio of acetate/propionate/butyrate. The CBC further showed variations in the ability of the rumen microbial population to adapt to phenolic compounds. 相似文献
3.
Growth and fermentation of an anaerobic rumen fungus on various carbon sources and effect of temperature on development. 总被引:5,自引:5,他引:0
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An anaerobic fungus (strain R1) resembling Neocallimastix spp. was isolated from sheep rumen. When grown on defined medium, the isolate utilized a wide range of polysaccharides and disaccharides, but of the eight monosaccharides tested only fructose, glucose, and xylose supported growth. The organism had doubling times of 5.56 h on glucose and 6.67 h on xylose, and in each case fermentation resulted in production of formate, acetate, lactate, and ethanol. During active growth, formate was a reliable indicator of fungal biomass. Growth on a medium containing glucose and xylose resulted in a doubling time of 8.70 h, but diauxic growth did not occur since both sugars were utilized simultaneously. The optimum temperature for zoospore and immature plant development was 39 degrees C, and no development occurred below 33 degrees C or above 41 degrees C. 相似文献
4.
The fungus Eutypa lata (syn. E. armeniacae), known as the causal agent of the death of many different woody plants, was found on dead branches of pistachio (Pistacia vera L.) in Greece. Isolations from diseased branches yielded consistently typical colonies of the asexual stage of the fungus (Libertella blepharis, syn. Cytosporina sp.), which proved to be undistinguishable from other cultures of the pathogen obtained from 15 different hosts. Furthermore, all isolates from pistachio tested for pathogenicity on apricot were pathogenic and yielded characteristic cankers. 相似文献
5.
Ingo Marenholz Armin Volz Andreas Ziegler Angela Davies Ioannis Ragoussis Bernhard P. Korge Dietmar Mischke 《Genomics》1996,37(3):295
The epidermal differentiation complex (EDC) unites a remarkable number of structurally, functionally, and evolutionarily related genes that play an important role in terminal differentiation of the human epidermis. It is localized within 2.05 Mb of region q21 on human chromosome 1. We have identified and characterized 24 yeast artificial chromosome (YAC) clones by mapping individual EDC genes, sequence-tagged site (STS) markers (D1S305, D1S442, D1S498, D1S1664), and 10 new region-specific probes (D1S3619–D1S3628). Here we present a contig that covers about 6 Mb of 1q21 including the entire EDC. Fluorescencein situhybridization on metaphase chromosomes with two YACs flanking the EDC determined its chromosomal orientation and established, in conjunction with physical mapping results, the following order of genes and STSs: 1cen–D1S442–D1S498–S100A10–THH–FLG–D1S1664–IVL–SPRR3–SPRR1–SPRR2–LOR–S100A9–S100A8–S100A7–S100A6–S100A5–S100A4–S100A3–S100A2–S100A1–D1S305–1qtel. These integrated physical, cytogenetic, and genetic mapping data will be useful for linkage analyses of diseases associated with region 1q21 and for the identification of novel genes and regulatory elements in the EDC. 相似文献
6.
Rob J. De Boer Alan S. Perelson Ioannis G. Kevrekidis 《Bulletin of mathematical biology》1993,55(4):781-816
Two types of behavior have been previously reported in models of immune networks. The typical behavior of simple models, which
involve B cells only, is stationary behavior involving several steady states. Finite amplitude perturbations may cause the
model to switch between different equilibria. The typical behavior of more realistic models, which involve both B cells and
antibody, consists of autonomous oscillations and/or chaos. While stationary behavior leads to easy interpretations in terms
of idiotypic memory, oscillatory behavior seems to be in better agreement with experimental data obtained in unimmunized animals.
Here we study a series of models of the idiotypic interaction between two B cell clones. The models differ with respect to
the incorporation of antibodies, B cell maturation and compartmentalization. The most complicated model in the series has
two realistic parameter regimes in which the behavior is respectively stationary and chaotic. The stability of the equilibrium
states and the structure and interactions of the stable and unstable manifolds of the saddle-type equilibria turn out to be
factors influencing the model's behavior. Whether or not the model is able to attain any form of sustained oscillatory behavior,
i.e. limit cycles or chaos, seems to be determined by (global) bifurcations involving the stable and unstable manifolds of
the equilibrium states. We attempt to determine whether such behavior should be expected to be attained from reasonable initial
conditions by incorporating an immune response to an antigen in the model. A comparison of the behavior of the model with
experimental data from the literature provides suggestions for the parameter regime in which the immune system is operating. 相似文献
7.
Yasmeen Hashim Ioannis Ragoussis Lyndal Kearney Sabrina Tosi Alex K. So 《Immunogenetics》1995,41(6):337-342
Yeast artificial chromosomes (YACs) were used to construct a physical map of the germline human T-cell chain gene complex (TCRB). Variable region genes (BV) for the 25 known subfamilies were used as probes to screen the ICRF AM4x YAC library. Of the five positive YACs identified, one YAC designated B3, 820 kilobase pairs (kbp) in size, scored positive for all 25 TCRBV subfamilies plus the constant region genes (BC) when analyzed by pulse field gel electrophoresis. Restriction enzyme mapping of B3 located TCRBV and TCRBC gene regions to 4 Sfi I fragments of 280 110, 90, and 125 kbp and was in accordance with published data. In addition comparison of hybridization results of Sfi I-restricted B3 and genomic DNA from the parental cell line GM1416B revealed identical banding patterns. The data thus showed YAC B3 encoded a complete and unrearranged TCRB gene locus of some 600–620 kbp. The map was further resolved by locating restriction sites for Sal I and Bss HII on B3, giving more precise localization of the individual TCRBV gene families. Flourescent in situ hybridization of B3 to spreads of human metaphase chromosomes localized B3 to 7q35. However, two additional signals were obtained; one attributable to the TCRBV orphon cluster on 9p21, the second to the long arm of chromosome 2. Polymerase chain reaction amplification of a chromosome 2 somatic cell hybrid, using primers for all 25 TCRBV gene families, revealed that the signal was not attributable to a second orphon cluster. It is suggested that B3 is a chimeric YAC with an intact TCRB locus flanked by chromosome 2 sequences. 相似文献
8.
Ioannis Dragatsis Christine Zioudrou Kyriaki Gerozissis 《Cellular and molecular neurobiology》1995,15(4):389-400
Summary 1. Inin vitro studies with adult male rats we have recently shown that the delta-opioid agonist DTLET inhibits the release of the Gonadotropin-Releasing Hormone (GnRH) from hypothalamic fragments containing the arcuate nucleus and the median eminence. This effect is receptor mediated and eicosanoid dependent (Gerozissiset al., 1993).2. In the present study we report that the delta-opioid antagonists with negative intrinsic activity, Diallyl-G and ICI 174864, applied under the same experimental conditions (30 min static incubations at 37°C, in a potassium rich milieu), in the absence of the agonist DTLET, also exert a similar to the agonist inhibitory effect on the release of GnRH.3. The dose-dependent inhibitory effect of Diallyl-G on GnRH release is reversed by increasing concentrations of DTLET. The mu and delta opioid antagonist, naloxone is without effect in the absence of DTLET. However, naloxone acts as an antagonist on the Diallyl-G-induced inhibition of GnRH release.4. Diallyl-G also inhibits the release of prostaglandin E2 (PGE2). In the presence of indomethacin or nordihydroguaiaretic acid, Diallyl-G is ineffective to further inhibit the release of GnRH. These latter observations taken together with the results of eicosanoid estimation suggest that PGE2 but not leukotrienes participate in the agonist-independent effects of Diallyl-G on GnRH release.5. Therefore these results support the hypothesis that delta-opioid antagonists with negative intrinsic activity exert agonist-independent biological responses similar to those of the agonists. 相似文献
9.
Theodorou Andreas; Weger Natalie; Kunke Kathleen; Rhee Kyoo; Bice David; Muggenberg Bruce; Lemen Richard 《Journal of applied physiology》1997,83(3):912-917
Theodorou, Andreas, Natalie Weger, Kathleen Kunke, KyooRhee, David Bice, Bruce Muggenberg, and Richard Lemen. Ragweed sensitization alters pulmonary vascular responses to bronchoprovocation in beagle dogs. J. Appl. Physiol.83(3): 912-917, 1997.In ragweed (RW)-sensitized beagle dogs, wetested the hypothesis that reactivity of the pulmonary vasculature wasenhanced with aerosolized histamine (Hist) and RW. Seven dogs wereneonatally sensitized with repeated intraperitoneal RW injections, and12 dogs were controls (Con). The dogs were anesthetizedwith intravenous chloralose, mechanically ventilated, and instrumentedwith femoral arterial and pulmonary artery catheters. Specific lungcompliance(CLsp),specific lung conductance (Gsp),systemic vascular resistance index, and pulmonary vascular resistanceindex (PVRI) were measured before and after bronchoprovocation withHist and RW. After Hist inhalation (5 breaths of 30 mg/ml), both Conand RW dogs had significant (P < 0.05) decreases inCLsp(51 ± 4 and 53 ± 5%, respectively) andGsp (65 ± 5 and69 ± 3%, respectively), but only RW-sensitized dogs had asignificant increase in PVRI (38 ± 10%). After RW inhalation (60 breaths of 0.8 mg/ml), only RW-sensitized dogs had significant increases (62 ± 20%) in PVRI and decreases inGsp (77 ± 4%) and CLsp(65 ± 7%). We conclude that, compared with Con,RW-sensitized beagle dogs have increased pulmonary vasoconstrictiveresponses with Hist or RW inhalation. 相似文献
10.
Rats received continuous administration of cis-flupenthixol (0.8-1.2 mg/kg/day) or trans-flupenthixol (0.9-1.2 mg/kg/day) in drinking water for 14 months. The administration of cis-flupenthixol, but not trans-flupenthixol, caused apparent cerebral dopamine receptor supersensitivity. Thus, animals receiving cis-flupenthixol, but not trans-flupenthixol, showed enhanced apo-morphine-induced stereotyped behaviour. Dopamine concentration in striatum was not altered by drug treatment but striatal HVA and DOPAC concentrations were reduced in animals receiving cis-flupenthixol, but not trans-flupenthixol. No consistent change in Bmax of KD for specific striatal 3H-spiperone binding was observed after 14 months drug intake. However, in cis-flupenthixol treated animals a 40% increase in Bmax was observed following 2 weeks drug withdrawal. Continuous cis-flupenthixol intake increased striatal acetylcholine concentrations; trans-flupenthixol was without effect. This suggests the apparent increase in cerebral dopamine receptor supersensitivity caused by continuous long-term cis-flupenthixol administration is of functional importance in the intact animal. 相似文献