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   1754篇
  免费   80篇
  2021年   11篇
  2020年   16篇
  2019年   11篇
  2018年   23篇
  2017年   13篇
  2016年   27篇
  2015年   41篇
  2014年   45篇
  2013年   103篇
  2012年   82篇
  2011年   71篇
  2010年   40篇
  2009年   52篇
  2008年   85篇
  2007年   82篇
  2006年   83篇
  2005年   77篇
  2004年   67篇
  2003年   61篇
  2002年   66篇
  2001年   47篇
  2000年   59篇
  1999年   55篇
  1998年   23篇
  1997年   11篇
  1996年   13篇
  1995年   17篇
  1994年   19篇
  1993年   12篇
  1992年   60篇
  1991年   40篇
  1990年   24篇
  1989年   33篇
  1988年   45篇
  1987年   40篇
  1986年   23篇
  1985年   25篇
  1984年   20篇
  1983年   24篇
  1981年   13篇
  1980年   9篇
  1979年   24篇
  1976年   11篇
  1975年   10篇
  1974年   13篇
  1973年   11篇
  1972年   12篇
  1971年   10篇
  1970年   13篇
  1968年   13篇
排序方式: 共有1834条查询结果,搜索用时 312 毫秒
371.
We describe the syntheses of three different deoxy-D-allose analogs [2-deoxy-D-allose (2-DOAll), 1,2-dideoxy-D-allose (1,2-DOAll), and 1,2-didehydro-1,2-dideoxy-D-allose (1,2-DHAll)] and their fatty acid esters via regioselective lipase-catalyzed transesterification. Among them, 2-DOAll and its decanoate (2-DOAll-C10) showed higher inhibitory activity on plant growth, which is similar to D-allose (All) and its decanoate (All-C10). Bioassay results of deoxy-All-C10 on four plant species suggest that the hydroxy group at the C-1 position might be important showing growth inhibitory activity. In addition, co-addition of gibberellin (GA3) with 1,2-DHAll-C10 and 2-DOAll-C10 recovered plant growth, suggesting that they might mainly inhibit biosynthesis of gibberellin.  相似文献   
372.
373.

Background

There are no studies about the caregiving burdens in families of patients with eating disorders in Japan, and only limited studies on the role of caregivers’ stress coping, social support, and mental health. This study examines caregiving burdens, mental health conditions, and associated factors in caregivers of anorexia nervosa (AN) patients in Japan.

Methods

Seventy-nine principal caregivers (70 mothers, 5 fathers, 3 spouses and 1 grandmother; mean age 56.0?±?8.0 years) for outpatients with AN (all female; mean age 26.6?±?7.9 years; BMI 14.6?±?3.2 kg/m2) were evaluated using self-report questionnaires in a cross-sectional study. The questionnaires included caregiving burden (J-ZBI_8), mental health conditions (GHQ28), stress coping styles (CISS), social support (SNQ), severity of the patient’s symptoms from the family’s perspective (ABOS), and family functioning (GF-FAD). Clinical information about the patients was also obtained.

Results

Mean caregiving burden assessed by J-ZBI_8 score was 12.4?±?7.0 (SD). The total GHQ score was 31.6?±?13.7 (Likert scoring) and 9.2?±?7.0 (GHQ scoring). Of the respondents, 48 (60.7 %) indicated a high risk for mental health problems that exceeded the cutoff point of the GHQ. Significantly higher caregiving burden and poor mental health conditions were shown in the group who had contact with patients?>?6 h a day compared to the group with daily patient contact?<?3 h (F (2, 76)?=?3.19, p?=?0.047 and F (2, 76)?=?9.39, p?<?0.001, respectively). Stepwise multiple regression analysis indicated that the factors that significantly predicted the caregiving burden were severity of the patient’s symptoms from the family’s perspective (β?=?0.47, p?<?0.001) and Emotion-Oriented Coping (β?=?0.38, p?=?0.002) (R2?=?0.401), while predictors of mental health conditions were Emotion-Oriented Coping (β?=?0.522, p?<?0.001), Affective Support (β?=??0.419, p?<?0.001), and contact time with patient (β?=?0.201, p?=?0.042) (R2?=?0.602).

Conclusion

Caregivers of AN patients experienced heavy burdens and manifested poor mental health conditions. The severity of the patient’s symptoms from the family’s perspective and the greater use of emotion-oriented coping were associated with higher burdens. Greater use of emotion-oriented coping, less affective support and longer contact with patients were related to worse mental health conditions. Interventions to promote caregivers’ adaptive coping styles may help reduce their caregiving burden and improve their mental health.
  相似文献   
374.

Background

Lung transplantation has been established as the definitive treatment option for patients with advanced lymphangioleiomyomatosis (LAM). However, the prognosis after registration and the circumstances of lung transplantation with sirolimus therapy have never been reported.

Methods

In this national survey, we analyzed data from 98 LAM patients registered for lung transplantation in the Japan Organ Transplantation Network.

Results

Transplantation was performed in 57 patients as of March 2014. Survival rate was 86.7% at 1 year, 82.5% at 3 years, 73.7% at 5 years, and 73.7% at 10 years. Of the 98 patients, 21 had an inactive status and received sirolimus more frequently than those with an active history (67% vs. 5%, p<0.001). Nine of twelve patients who remained inactive as of March 2014 initiated sirolimus before or while on a waiting list, and remained on sirolimus thereafter. Although the statistical analysis showed no statistically significant difference, the survival rate after registration tended to be better for lung transplant recipients than for those who awaited transplantation (p = 0.053).

Conclusions

Lung transplantation is a satisfactory therapeutic option for advanced LAM, but the circumstances for pre-transplantation LAM patients are likely to alter with the use of sirolimus.  相似文献   
375.
A genomic clone specifying a new HLA class II antigen β chain,DQB3, was isolated from a human genomic phage library using aDQB1 cDNA probe under low stringency conditions. Southern hybridization and nucleotide sequence analyses identified the β2 domain exon (exon 3) with several deleterious mutations and the CP-TM-CY exon [connecting peptide, transmembrane, and cytoplasmic regions, (exon 4)], but the first, second, and fifth exons encoding the 5′ UT-leader, the β1 domain, and the 3′ UT domain of normal β chains, respectively, were entirely missing. The nucleotide sequences of these two exons were distinct from those of other class II β chain genes, but slightly more related to theDQB1 andDQB2 genes than to other class II genes. TheDQB3 sequence mapped betweenDQA2 andDQB1, 15 kb upstream fromDQA2, by analysis of overlapping cosmid clones. This mapping was supported by the fact thatTaq I,Msp I, andBam HIDQB3 polymorphisms were perfectly correlated with theDQA2 polymorphism and not with any polymorphisms in theDR orDQ subregion, suggesting the presence of a hot spot for recombination betweenDQB3 andDQB1. The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number M26577.  相似文献   
376.
recA protein, which is essential for genetic recombination in Escherichia coli, causes extensive unwinding of the double helix by an ATP-dependent reaction and accumulation of positive supercoiling in closed circular double-stranded DNA. Initiation of the extensive unwinding was largely dependent on homologous single-stranded DNA. Therefore, it is likely that the extensive unwinding is initiated mainly at the site of D-loops. "Nascent D-loops" in which the two DNA molecules did not interwind were also good initiation sites of extensive unwinding. When the concentration of Mg2+ was decreased from the standard conditions for D-loop formation (13 mM MgCl2; the higher Mg2+ condition) to the lower Mg2+ condition (1 to 2 mM MgCl2), extensive unwinding by recA protein was initiated very quickly in the absence of single-stranded DNA. Results showed that this single-stranded DNA-independent initiation of extensive unwinding (i) requires negative superhelicity of the double-stranded DNA and (ii) is a first order reaction with respect to the DNA. These observations suggest that, under the lower Mg2+ condition, the extensive unwinding starts at a transiently denatured site in the negative superhelical DNA. Once initiated, the unwinding by recA protein is propagated extensively, even under conditions that do not allow its initiation. Therefore, the propagation of unwinding is a processive reaction ("processive unwinding"). Previous studies indicated that recA protein promotes "distributive unwinding" of double helix which depends on single-stranded DNA. Therefore, recA protein promotes unwinding of the double helix by either of two distinct pathways. Stress caused by the processive unwinding could explain the dissociation of D-loops and reversible inactivation of the double-stranded DNA in a D-loop cycle.  相似文献   
377.
The sterols of the hydroid, Dynamena pumila (Sertulariidae) have been analysed for the first time. Results from TLC, GLC, mass spectrometry and NMR have led to the determination of the structure of 16 steroids, the main being cholesterol (37%). A series of Δ5 22 C26, C27, C28 C29 sterols, and the corresponding stanols and fucostanol, have also been identified.  相似文献   
378.
379.
A growth inhibiting substance, detected by the Avena coleoptile straight growth test, was isolated from dormant iris bulbs and identified as capric  相似文献   
380.
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