首页 | 官方网站   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   341篇
  免费   31篇
  国内免费   11篇
生物科学   383篇
  2023年   4篇
  2022年   9篇
  2021年   13篇
  2020年   10篇
  2019年   9篇
  2018年   7篇
  2017年   11篇
  2016年   8篇
  2015年   8篇
  2014年   16篇
  2013年   21篇
  2012年   13篇
  2011年   27篇
  2010年   11篇
  2009年   22篇
  2008年   20篇
  2007年   25篇
  2006年   12篇
  2005年   14篇
  2004年   12篇
  2003年   11篇
  2002年   6篇
  2001年   5篇
  2000年   5篇
  1999年   7篇
  1998年   7篇
  1997年   6篇
  1996年   2篇
  1995年   4篇
  1994年   7篇
  1993年   10篇
  1992年   4篇
  1991年   8篇
  1990年   4篇
  1989年   2篇
  1988年   4篇
  1987年   1篇
  1986年   5篇
  1985年   4篇
  1981年   2篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1971年   2篇
排序方式: 共有383条查询结果,搜索用时 171 毫秒
1.
Many proteins that can assemble into higher order structures termed amyloids can also concentrate into cytoplasmic inclusions via liquid–liquid phase separation. Here, we study the assembly of human Golgi-Associated plant Pathogenesis Related protein 1 (GAPR-1), an amyloidogenic protein of the Cysteine-rich secretory proteins, Antigen 5, and Pathogenesis-related 1 proteins (CAP) protein superfamily, into cytosolic inclusions in Saccharomyces cerevisiae. Overexpression of GAPR-1-GFP results in the formation GAPR-1 oligomers and fluorescent inclusions in yeast cytosol. These cytosolic inclusions are dynamic and reversible organelles that gradually increase during time of overexpression and decrease after promoter shut-off. Inclusion formation is, however, a regulated process that is influenced by factors other than protein expression levels. We identified N-myristoylation of GAPR-1 as an important determinant at early stages of inclusion formation. In addition, mutations in the conserved metal-binding site (His54 and His103) enhanced inclusion formation, suggesting that these residues prevent uncontrolled protein sequestration. In agreement with this, we find that addition of Zn2+ metal ions enhances inclusion formation. Furthermore, Zn2+ reduces GAPR-1 protein degradation, which indicates stabilization of GAPR-1 in inclusions. We propose that the properties underlying both the amyloidogenic properties and the reversible sequestration of GAPR-1 into inclusions play a role in the biological function of GAPR-1 and other CAP family members.  相似文献   
2.
The proportion of planted forests in the Mediterranean Basin is one of the largest in the world. These plantations are dominated by pine species and present a series of characteristics such as low elevation, high competition or small tree size that make them more vulnerable to droughts. However, quantitative assessments of their post-drought growth resilience in accordance with species, site factors and tree characteristics are lacking. In this study we sampled 164 trees at four forest sites located in the drought-prone Sierra Nevada, southeastern Spain. We compared growth responsiveness to drought in rear-edge planted vs. relic natural Scots pine (Pinus sylvestris) and coexisting Pyrenean oak (Quercus pyrenaica) stands. Our objective was to characterize and compare the different growth responses to drought between species and sites and the effect of the main physiographic factors (altitude, aspect, and slope) on these responses since the influence of these factors on post-drought resistance and resilience has received little attention to date. Our results reveal that the planted pine sites with the lowest mean growth rates displayed greater resistance during drought, and that higher altitude was associated with improved resistance and/or resilience for all species and sites. Natural pine and Pyrenean oak stands were better adapted to the dry climatic conditions of the Mediterranean region where the study was undertaken, displaying greater resistance and/or resilience and lower influence of drought on growth in comparison to stands of planted pines. These results suggest that promoting the conservation of high-elevation pine plantations and enhancing the regeneration of natural pine and oak may improve the resistance and resilience of these drought-prone forest ecosystems.  相似文献   
3.
Astiban produced structural damage in male Schistosoma mansoni (Puerto Rican strain) in mice. The degree of disorganization was directly related to the dosage administered, although initial changes in structure for the first three doses (3 × 30–40 mg/kg) varied between individual worms of the same infection. More consistent damage to the tegument, parenchyma, and reproductive organs occurred after 6 × 40 mg/kg of Astiban injections. Exposure of the subtegumentary musculature preceded appearance of an increased number of noncytoplasmic spaces in various tissues, probably a result of osmotic stress. Testicular disorganization was prominent initially in spermatozoa and spermatids, but became more generalized with drug accumulation. The sustentacular cells showed increased phagocytic activity with testicular damage. Continuous administration of drug resulted in a general distortion of the worm's morphology. However, partial recovery occurred within 22 days following cessation of drug administration.  相似文献   
4.
Temperate seagrass meadows form valuable ecosystems in coastal environments and present a distinct seasonal growth. They are threatened by an increasing amount of stressors, potentially affecting their capacity to recover from disturbances. We hypothesized that their resilience to disturbances is affected by seasonal dynamics. Hence, we investigated the effect of the timing of the disturbance on seagrass Leaf Area Index (as a proxy for presence, or ‘visible’ status), recovery from disturbance (as a proxy for meadow resilience), and rhizome carbohydrates (as a proxy for longer term resilience) by a series of four disturbance-recovery field experiments spread over the growing season at two sites in Shandong Province, China. During the course of the growing season, we found the highest recovery at the start of the growing season, lowest recovery when Leaf Area Index peaked around mid-growing season, and intermediate recovery when Leaf Area Index decreased at the end of the growing season. Rhizome carbohydrates were not affected by disturbances during any of the four experimental periods and could not explain the low recovery during mid-growing season. The two sites differed in exposure and in the occurrence of incidents like a green tide and storms, which affected recovery. However, general patterns were similar; timing strongly influenced the indicator of meadow resilience and its correlation with presence during the two main seagrass growth phases. Our results emphasize the importance of carefully considering timing in the evaluation of seagrass resilience in temperate systems. Furthermore, our study implies that, to effectively protect seagrass beds, conservation management should aim at avoiding disturbances particularly during the peak of the growing season, when resilience is lowest.  相似文献   
5.
The consumer recovery model has had increasing influence on mental health practices in the United States, Western Europe, and several other countries. However, adoption of the model has reflected political decisions rather than empirical evidence of the validity of the model or its value for treatment services. The recovery construct is poorly defined, and until recently there has been no reliable and valid measure with which to base a research program. We have developed an empirical measure that is well-suited for both research and clinical applications: the Maryland Assessment of Recovery in Serious Mental Ill-ness (MARS). We briefly describe the MARS and present preliminary data demonstrating that recovery is not a simple by-product of traditional outcome do-mains, but seems to be a distinct construct that may have important implications for understanding consumers with serious mental illness and for evaluating the outcome of treatment programs.  相似文献   
6.
目的:探讨加速康复外科理念对行根治性子宫切除术的宫颈癌患者的围手术期应用价值。方法:选取2013年1月至2018年7月在我院行因宫颈癌行根治性子宫切除术的66例患者作为研究对象。将入院患者随机分为观察组及对照组,观察组接受加速康复外科理念治疗(30例),对照组为常规治疗组(36例)。比较两组患者的肠鸣音恢复时间、肛门排气时间、下床行走时间、术后住院时间以及术后并发症的发生情况。结果:观察组与对照组肠鸣音恢复时间分别为(35.9±3.4)h及(39.6±3.0)h,术后首次排气时间分别为(50.7±2.7)h及(54.8±3.2)h,下床行走时间分别为(49.9±2.6)h及(53.6±3.2)h。术后住院时间分别为(7.6±1.7)d及(9.2±1.8)d,观察组以上指标均显著短于对照组(P0.01)。观察组与对照组的术后并发症总发生率分别为10.11%及23.44%,观察组显著低于对照组(P0.05)。两组拔除尿管后尿潴留的发生情况比较差异无统计学意义(P0.05)。结论:加速康复外科理念用于宫颈癌根治术患者的围手术期可有效加速患者的康复,且安全性较高。  相似文献   
7.
目的 建立回收乙醇微生物限度检查方法,并对该法的适用性进行确认。方法 探索合适的稀释度来消除乙醇对微生物的抑菌性,寻找合适的过滤量,确定操作步骤。通过多次试验结果确定质量标准。另取3批回收乙醇,进行微生物限度方法适用性试验,分别计算金黄色葡萄球菌( Staphylococcus aureus )、铜绿假单胞菌( Pseudomonas aeruginosa )、枯草芽孢杆菌( Bacillus subtilis )、白色念珠菌( Candida albicans )、黑曲霉( Aspergillus niger )回收率。结果 回收乙醇至少稀释10倍时,可消除其抑菌性。最终确定试验时先用pH 7.0无菌氯化钠-蛋白胨缓冲液将供试品稀释10倍,薄膜过滤法过滤量为每张滤膜100 mL。根据多次微生物限度检查结果,最终确定回收乙醇微生物限度质量标准为不高于10 cfu/mL。方法适用性试验中,3批回收乙醇,5种菌的回收率均在50%~200%范围内,表明该方法适用于回收乙醇的微生物限度检查。结论 回收乙醇经10倍稀释后,可以消除其抑菌性,可以采用薄膜过滤法进行微生物限度检查。  相似文献   
8.
9.
许多长距离迁徙的雀形目鸟类的种群数量正在持续下降,田鹀(Emberiza rustica)种群数量下降趋势更为突出。通过对田鹀种群数量长期监测和迁徙动态分析,可为此物种保护提供科学依据。从2001年开始,陆续在黑龙江省高峰、青峰、帽儿山、新青和大沾河,吉林省珲春和吉林市,辽宁省的辽宁鸟类研究中心(大连)和旅顺老铁山,以及内蒙古乌尔其汗鸟类栖息的临水林缘处布网环志。截至2018年,累计环志田鹀184181只,其中春季88571只,秋季95610只;各年度环志数量波动较大,总体呈现急速下降趋势。幼鸟的越冬损失率高达41.3%。田鹀106只次的回收信息表明,自然条件下田鹀寿命可达11年以上;日迁飞距离最快可达到300 km,飞行速度可达30 km/h。中国东北地区是田鹀等鸟类的重要迁徙途经地;田鹀的迁徙路线相对稳定,在瑞典北部繁殖的种群经中国东北地区迁徙到天津以南越冬。通过环志发现,近些年田鹀种群数量急速下降。通过比对,发现中国东北地区田鹀的环志数量变化趋势与瑞典的田鹀环志数量变化趋势相似;相对于环志数量最多的年份,环志数量下降95%以上,值得关注。栖息地破碎化、非法猎捕等是影响田鹀生存的主要受威胁因素。建议依据田鹀等鸟类生物学习性,加强鸟类栖息地的保护,坚持长期标准化的鸟类环志监测,进一步探索鸟类迁徙规律,以助于鸟类种群的恢复。  相似文献   
10.
As soluble intercellular adhesion molecule-1 (sICAM-1) was recently hypothesized to be a key player in the mechanisms involved in exercise-induced muscular damage (EIMD), we investigated its circulating concentration changes in athletes before and after EIMD with and without the use of whole-body cryostimulation (WBC; 3 min at −110 °C) at the exercise end and repeated once a day during 4 days.We previously characterized plasma specimens from 11 endurance athletes who performed twice (randomized crossover design) strenuous running leading to EIMD, followed by passive recovery or WBC. Muscle soreness and inflammatory response were observed in both cases but the use of WBC induced a significant reduction in these responses (PlosOne 2011; 6:e22748). We now found that sICAM-1 concentration slightly increased in both circumstances and remained elevated for 24 h (p < 0.01). However, no significant WBC effect was observed concerning sICAM-1 changes indicating that this compound is not a major player both in EIMD and WBC physiological impacts.  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-23

京公网安备 11010802026262号