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   1614篇
  免费   226篇
  1840篇
  2022年   18篇
  2021年   34篇
  2019年   14篇
  2018年   21篇
  2017年   18篇
  2016年   40篇
  2015年   51篇
  2014年   45篇
  2013年   44篇
  2012年   85篇
  2011年   90篇
  2010年   64篇
  2009年   58篇
  2008年   61篇
  2007年   51篇
  2006年   53篇
  2005年   56篇
  2004年   56篇
  2003年   46篇
  2002年   46篇
  2001年   47篇
  2000年   54篇
  1999年   35篇
  1998年   26篇
  1997年   16篇
  1995年   17篇
  1994年   23篇
  1993年   21篇
  1992年   28篇
  1991年   23篇
  1990年   39篇
  1989年   44篇
  1988年   35篇
  1987年   25篇
  1986年   28篇
  1985年   30篇
  1984年   30篇
  1983年   21篇
  1981年   19篇
  1979年   20篇
  1978年   21篇
  1977年   20篇
  1976年   16篇
  1975年   18篇
  1974年   20篇
  1973年   24篇
  1972年   18篇
  1971年   22篇
  1970年   16篇
  1967年   15篇
排序方式: 共有1840条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
The frequency of nine different mutated alleles known to occur in the glucocerebrosidase gene was determined in 247 Gaucher patients, of whom 176 were of Jewish extraction, 2 were Jewish with one converted parent, and 69 were of non-Jewish origin. DNA was prepared from peripheral blood, active glucocerebrosidase sequences were amplified by using the PCR technique, and the mutations were identified by using the allele-specific oligonucleotide hybridization method. The N37OS mutation appeared in 69.77% of the mutated alleles in Jewish patients and in 22.86% of the mutated alleles in non-Jews. The 84GG mutation, which has not been found so far among non-Jewish patients, existed in 10.17% of the disease alleles among Jewish patients. The IVS + 1 mutation constituted 2.26% of the disease alleles among Jewish patients and 1.43% among the non-Jewish patients. RecTL, a complex allele containing four single-base-pair changes, occurred in 2.26% of the alleles in Jewish patients and was found in two (1.43%) of the patients of non-Jewish extraction. Another complex allele, designated "RecNciI" and containing three single-point mutations, appeared in 7.8% of alleles of non-Jewish patients and in only two (0.56%) of the Jewish families. The prevalence of the L444P mutation among non-Jewish Gaucher patients was 31.43%, while its prevalence among Jewish patients was only 4.24%. The prevalence of two other point mutations--D409H and R463C--was 5.00% and 3.57%, respectively, among non-Jewish patients and was not found among the Jewish Gaucher patient population. The prevalence of the R496H mutation, found so far only among Jewish patients, was 1.13%. The results presented demonstrate that seven mutations identify 90.40% of the mutations among Jewish patients and that these seven mutations allow diagnosis of only 73.52% of the non-Jewish patients. Identification of additional mutant alleles will enhance the accuracy of carrier detection.  相似文献   
105.
Normative data on plasma amine oxidase activity were obtained for four primate species, M. mulatta, M. arctoides, C. aethiops and H. sapiens. Significant between-species differences in activity were observed. In a large sample of M. mulatta, no significant relationship between age and plasma amine oxidase activity was observed, but adult males had significantly higher enzyme activities than adult females.  相似文献   
106.
Regulators face the problem of ensuring that wetland functions that are lost due to permitting actions are restored via mitigation of those impacts. While there has been considerable study of wetland function, little of it has been directed toward the practical assessment of mitigation success. Development of quantitatively based rapid assessment methods would provide valuable assistance to the regulatory community. Regional and local goal setting, including a determination of whether strict in-kind restoration or restoration of habitat balance is preferable, is needed to ensure that the ecological health of the area is restored to the greatest extent possible.  相似文献   
107.
Observations of monkey behavior were made on free-ranging and corral-enclosedMacaca mulatta. Two sampling techniques were used: focal animal and group observations. Group observations measured frequencies of social behavior whereas focal observations used time samples which estimated durations of social and nonsocial activities as well as frequencies of social behavior. Analysis of concordance within and between sampling techniques revealed that short duration focal time samples provide a reliable estimate of total frequencies of social behaviors derived using group observations and furthermore, allows the recording of important nonsocial activities not easily recorded in terms of frequencies. Focal time sampling is advantageous for certain types of studies where the equal distribution of observation time between individuals is important, particularly in the field where visibility is often limited and individuals can only be observed continuously for short periods of time. This work was supported by grants from the H. F. Guggenheim Foundation, Dr.H. C. Robinson, Jr., and USPHS grants MH 24607 and MH 25642.  相似文献   
108.
109.
Periapical abscesses of canine teeth in a group of 47 male cynomolgus macaques are found to be associated with a procedure, involving cutting the canine teeth, used to make non-human primates less hazardous. Examination of 150 canine teeth in dry specimens revealed 30 cut teeth with no exposure of the pulpal chamber and 107 cut teeth where the dental pulp had been exposed. Of those teeth which had the pulpal chamber exposed by the cutting procedure, 85 (79.4%) showed clear evidence of osseous changes consistent with abscess formation in the apical regions.  相似文献   
110.
Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2 (NPFF), an endogenous mammalian antiopioid peptide, has been shown by other laboratories to attenuate the acute antinociceptive effects of morphine, the development of morphine tolerance, and naloxone-induced withdrawal in morphine-dependent rats. The present study determined the effect of chronic NPFF on mu opioid receptors and mRNA for the endogenous opioids dynorphin and enkephalin. Rats received ICV infusions of either saline or NPFF (5 μg/h) for 13 days via Alzet 2002 osmotic minipumps. Homogenate binding studies, which used whole brain membranes, demonstrated that NPFF decreased the Bmax of mu binding sites (labeled by [3H][ -Ala2-MePhe4,Gly-ol5]enkephalin) from 262 ± 12 to 192 ± 12 fmolmg protein, and increased the Kd from 1.1 to 2.3 nM. Quantitative receptor autoradiography and in situ hybridization experiments were conducted with sections collected at the level of the striatum. The density of mu opioid binding sites labeled by [3H][ -Ala2-MePhe4,Gly-ol5]enkephalin was decreased in all brain areas measured except the corpus callosum, and there was no change in dynorphin mRNA or enkephalin mRNA in the caudate, the nucleus accumbens, or the ventral pallidum. Rats chronically administered ICV morphine sulfate (20 μg/h) for 14 days developed tolerance to morphine and a low degree of dependence, as measured by naloxone-precipitated withdrawal. Chronic administration of NPFF concurrently with morphine sulfate did not significantly alter naloxone-induced withdrawal signs or the development of morphine tolerance. Viewed collectively with previous findings that chronic ICV infusion of anti-NPFF IgG upregulates mu receptors, these data provide additional evidence that the density of CNS mu receptors is tonically regulated by NPFF in the extracellular fluid. The action of NPFF to decrease mu receptors is consistent with an antiopioid role for this peptide; however, the fact that NPFF (administered into the lateral ventricle) did not appreciably alter expression of morphine tolerance and dependence contrasts with previous findings and reinforces the view that this effect is most reliably seen after third ventricle administration.  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