首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   226篇
  免费   13篇
  2022年   3篇
  2021年   6篇
  2020年   1篇
  2019年   8篇
  2018年   3篇
  2017年   4篇
  2016年   8篇
  2015年   11篇
  2014年   5篇
  2013年   15篇
  2012年   6篇
  2011年   8篇
  2010年   9篇
  2009年   6篇
  2008年   8篇
  2007年   9篇
  2006年   5篇
  2005年   12篇
  2004年   6篇
  2003年   6篇
  2002年   4篇
  2001年   4篇
  2000年   7篇
  1999年   2篇
  1997年   3篇
  1996年   1篇
  1994年   3篇
  1993年   2篇
  1992年   8篇
  1991年   6篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1986年   4篇
  1985年   3篇
  1984年   4篇
  1982年   7篇
  1981年   7篇
  1980年   2篇
  1979年   6篇
  1978年   2篇
  1977年   4篇
  1976年   3篇
  1975年   2篇
  1974年   3篇
  1973年   5篇
  1968年   1篇
  1967年   1篇
  1965年   1篇
排序方式: 共有239条查询结果,搜索用时 15 毫秒
231.
The diploid number 2n=22 and haploid number n=11 found for Eisenia foetida from Palermo, Italy, confirm earlier data for this species from other localities. Analyses of silver-stained and C-banded mitotic and meiotic chromosomes suggest that a single chromosome pair has active NORs which correspond with C-positive regions. The occurrence of nucleolus activity during spermatogenesis of E. foetida is ascertained.  相似文献   
232.
A diurnal pattern in oxytocin concentrations is present in cerebrospinal fluid (CSF) removed from the spinal subarachnoid space of monkeys, with elevated levels occurring in the early light hours. In order to investigate the possible role of endogenous opioid peptides in the generation of this oxytocin rhythm, we administered naloxone (0.4 mg/kg/h x 48 h) to rhesus and cynomolgus monkeys and examined the effects on the diurnal pattern of oxytocin in CSF collected from the lumbar subarachnoid spinal space. Monkeys maintained on jacket/tether/swivel systems and in a 12 h light: 12 h dark cycle (lights on 07.00-19.00 h) were implanted with temporary spinal subarachnoid catheters. CSF was continuously collected from the lumbar subarachnoid space and assayed for oxytocin. Oxytocin concentrations in CSF showed a diurnal variation with peak and nadir concentrations during light and dark hours, respectively. The lumbar CSF concentrations of oxytocin were not significantly different during naloxone vs. saline infusion. Plasma oxytocin concentrations, measured in the same animals, displayed no diurnal variation and were not significantly different during naloxone vs. saline infusion. We conclude that naloxone administration for 48 h does not perturb the diurnal variation in oxytocin concentrations in the CSF of monkeys. Mu opioid receptors are unlikely to be involved in modulating the diurnal rhythm of oxytocin in the CSF of monkeys.  相似文献   
233.
Several cultures established from biopsies of apparently normal adult human glial material showed no cells positive for glial fibrillary acidic protein (GFA) when examined after seven or more cumulative population doublings (CPD), although the established glioma line U251 MG showed approximately 3% GFA-positive cells, and U333 CG/343 MG clone 3 showed greater than 98% GFA-positive cells. Both the human glia delivered cultures and the glioma lines were positive when assayed with sera specific for vimentin. We therefore investigated the expression of GFA as a function of cumulative population doublings after the establishment of primary cultures. Under our experimental conditions, although GFA-positive cells were clearly present in the primary cultures accounting for some 3%-14% of the cells present, the GFA marker was subsequently lost, and the proliferating cultures expressed only the vimentin type of intermediate filament. Those cells that were GFA-positive also appeared to be vimentin-positive. GFA expression was not reinduced in cultures that had lost the GFA marker by treatment with dibutyryl cyclic AMP. We discuss two alternate hypotheses for the origin of the GFA-negative cells: (1) the cultures area of astrocyte origin but lost the ability to express GFA on culturing; (2) the cultures originate from cells of nonastrocyte origin present in the primary material.  相似文献   
234.
235.
236.
In order to localize the cell specific domains of glial- and muscle-type intermediate filaments, the purified subunits (bovine GFA protein and chicken desmin) were fragmented and the digests passed through immunoaffinity columns or stained by the immunoblotting procedure to determine which fragments reacted with the monospecific polyvalent antisera. The following fragments were found immunoreactive according to these criteria: 30 K (GFA) and 33 K (desmin) N-bromosuccinimide fragments (tryptophan cleavage); 35 K (GFA) and 39 K (desmin) 2-nitro-5-thiocyanobenzoic acid fragments (cysteine cleavage); 18 K (GFA) and 9 K (desmin) cyanogen bromide fragments. Fragmentation of GFA protein was also accomplished using proteolytic digestion with chymotrypsin and trypsin. Two resistant core polypeptides, one about 37 K and stable in the chymotryptic digests and one about 21 K and stable in the tryptic digests bound specifically to the immunoaffinity columns. The 21 K tryptic fragment was found to contain the 18 K cyanogen bromide fragment. The fragmentation patterns support recently published structural domain models for intermediate filament proteins. The immunochemical findings indicate that the immunoreactive regions of GFA protein are located in the aminoterminal region of the middle domain of these models (coil I), while they appear to be situated in the aminoterminal headpiece of the protein in the case of desmin.  相似文献   
237.
The effects of cyclic 3′,5′-adenosine monophosphate (cAMP) on amaranthin synthesis in the dark, or in the presence of kinetin or light were investigated in isolated cotyledons of Amaranthus tricolor and A. caudatus. The results suggest that sites or modes of action of cAMP and kinetin are not separated and differ from those of light and that the nucleotide cannot be considered a messenger involved in amaranthin formation stimulated by kinetin or by light.  相似文献   
238.
BackgroundEffective implementation strategies are needed to increase engagement in HIV services in hyperendemic settings. We conducted a pragmatic cluster-randomized trial in a high-risk, highly mobile fishing community (HIV prevalence: approximately 38%) in Rakai, Uganda, to assess the impact of a community health worker-delivered, theory-based (situated Information, Motivation, and Behavior Skills), motivational interviewing-informed, and mobile phone application-supported counseling strategy called “Health Scouts” to promote engagement in HIV treatment and prevention services.Methods and findingsThe study community was divided into 40 contiguous, randomly allocated clusters (20 intervention clusters, n = 1,054 participants at baseline; 20 control clusters, n = 1,094 participants at baseline). From September 2015 to December 2018, the Health Scouts were deployed in intervention clusters. Community-wide, cross-sectional surveys of consenting 15 to 49-year-old residents were conducted at approximately 15 months (mid-study) and at approximately 39 months (end-study) assessing the primary programmatic outcomes of self-reported linkage to HIV care, antiretroviral therapy (ART) use, and male circumcision, and the primary biologic outcome of HIV viral suppression (<400 copies/mL). Secondary outcomes included HIV testing coverage, HIV incidence, and consistent condom use. The primary intent-to-treat analysis used log-linear binomial regression with generalized estimating equation to estimate prevalence risk ratios (PRR) in the intervention versus control arm. A total of 2,533 (45% female, mean age: 31 years) and 1,903 (46% female; mean age 32 years) residents completed the mid-study and end-study surveys, respectively. At mid-study, there were no differences in outcomes between arms. At end-study, self-reported receipt of the Health Scouts intervention was 38% in the intervention arm and 23% in the control arm, suggesting moderate intervention uptake in the intervention arm and substantial contamination in the control arm. At end-study, intention-to-treat analysis found higher HIV care coverage (PRR: 1.06, 95% CI: 1.01 to 1.10, p = 0.011) and ART coverage (PRR: 1.05, 95% CI: 1.01 to 1.10, p = 0.028) among HIV–positive participants in the intervention compared with the control arm. Male circumcision coverage among all men (PRR: 1.05, 95% CI: 0.96 to 1.14, p = 0.31) and HIV viral suppression among HIV–positive participants (PRR: 1.04, 95% CI: 0.98 to 1.12, p = 0.20) were higher in the intervention arm, but differences were not statistically significant. No differences were seen in secondary outcomes. Study limitations include reliance on self-report for programmatic outcomes and substantial contamination which may have diluted estimates of effect.ConclusionsA novel community health worker intervention improved HIV care and ART coverage in an HIV hyperendemic setting but did not clearly improve male circumcision coverage or HIV viral suppression. This community-based, implementation strategy may be a useful component in some settings for HIV epidemic control.Trial registrationClinicalTrials.gov NCT02556957.

Larry Chang and co-workers study an intervention by which community health workers aim to promote engagement in HIV treatment and prevention services in Uganda.  相似文献   
239.
Antisera raised to desmin, the protein subunit of muscle-type intermediate filaments (IFs), were used to study by indirect immunofluorescence and immunoperoxidase procedures the early development of skeletal muscle in the rat embryo. The specificity of the antisera (Dahl D, Bignami A: J Histochem Cytochem 30:207, 1982) was confirmed by immune blotting on chicken gizzard extracts and purified antigen. Desmin-positive cells were first observed on day 12 by immunofluorescence and on day 13 by the immunoperoxidase procedure. Desmin immunoreactivity was not found in caudal somites in which the dermatome was present, i.e., somites where the dorso-lateral part had maintained its definite boundaries and epithelioid characteristics. Desmin-positive cells were observed within the myotome of cranial somites where the dermatome had disappeared. Compared to day 13, desmin-positive cells had extended ventrally on day 14, while on day 15, they were found in the skeletal musculature of the trunk and the limbs.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号