全文获取类型
收费全文 | 5176篇 |
免费 | 431篇 |
国内免费 | 296篇 |
出版年
2024年 | 13篇 |
2023年 | 50篇 |
2022年 | 104篇 |
2021年 | 217篇 |
2020年 | 131篇 |
2019年 | 186篇 |
2018年 | 215篇 |
2017年 | 142篇 |
2016年 | 239篇 |
2015年 | 325篇 |
2014年 | 382篇 |
2013年 | 335篇 |
2012年 | 464篇 |
2011年 | 434篇 |
2010年 | 269篇 |
2009年 | 260篇 |
2008年 | 282篇 |
2007年 | 257篇 |
2006年 | 219篇 |
2005年 | 199篇 |
2004年 | 184篇 |
2003年 | 163篇 |
2002年 | 167篇 |
2001年 | 101篇 |
2000年 | 67篇 |
1999年 | 70篇 |
1998年 | 61篇 |
1997年 | 42篇 |
1996年 | 42篇 |
1995年 | 37篇 |
1994年 | 30篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有5903条查询结果,搜索用时 15 毫秒
991.
992.
Xiao-Xia Zhang Jian-Fei Ye Shawn W.Laffan Brent D.Mishler Andrew H.Thornhill Li-Min Lu Ling-Feng Mao Bing Liu You-Hua Chen An-Ming Lu Joseph T.Miller Zhi-Duan Chen 《植物学报(英文版)》2022,64(1):105-117
The flora of China is well known for its high diversity and endemism. Identifying centers of endemism and designating conservation priorities are essential goals for biodiversity studies.However, there is no comprehensive study from a rigorous phylogenetic perspective to understand patterns of diversity and endemism and to guide biodiversity conservation in China. We conducted a spatial phylogenetic analysis of the Chinese angiosperm flora at the generic level to identify centers of neo-and pale... 相似文献
993.
994.
Kalthoum Tizaoui Jae Won Yang Keum Hwa Lee Ji Hong Kim Minseok Kim Sojung Yoon Yeonwoo Jung Joon Beom Park Kitae An Hyeok Choi Donggyu Song HyunTaek Jung Seongmin Ahn Taeho Yuh Hee Min Choi Jae Ha Ahn Younjuong Kim Sanghyun Jee Hyeongsun Lee Soohwa Jin Jun-Gu Kang Bohyun Koo Joo Yeop Lee Kyoung Min Min Wonseok Yoo Hyeong Jun Rhyu Yeonjung Yoon Min Ho Lee Sung Eun Kim Jimin Hwang Ai Koyanagi Louis Jacob Seoyeon Park Jae Il Shin Lee Smith 《International journal of biological sciences》2022,18(9):3731
YKL-40, a chitinase-3-like protein 1 (CHI3L1) or human cartilage glycoprotein 39 (HC gp-39), is expressed and secreted by various cell-types including macrophages, chondrocytes, fibroblast-like synovial cells and vascular smooth muscle cells. Its biological function is not well elucidated, but it is speculated to have some connection with inflammatory reactions and autoimmune diseases. Although having important biological roles in autoimmunity, there were only attempts to elucidate relationships of YKL-40 with a single or couple of diseases in the literature. Therefore, in order to analyze the relationship between YKL-40 and the overall diseases, we reviewed 51 articles that discussed the association of YKL-40 with rheumatoid arthritis, psoriasis, systemic lupus erythematosus, Behçet disease and inflammatory bowel disease. Several studies showed that YKL-40 could be assumed as a marker for disease diagnosis, prognosis, disease activity and severity. It is also shown to be involved in response to disease treatment. However, other studies showed controversial results particularly in the case of Behçet disease activity. Therefore, further studies are needed to elucidate the exact role of YKL-40 in autoimmunity and to investigate its potential in therapeutics. 相似文献
995.
Xiaojing Meng Lingxiao Yue An Liu Wenjuan Tao Li Shi Wan Zhao Zhongmin Wu Zhi Zhang Liecheng Wang Xulai Zhang Wenjie Zhou 《The Journal of biological chemistry》2022,298(8)
Pain is a multidimensional perception that includes unpleasant somatosensory and affective experiences; however, the underlying neural circuits that mediate different components of pain remain elusive. Although hyperactivity of basolateral amygdala glutamatergic (BLAGlu) neurons is required for the somatosensory and emotional processing of pain, the precise excitatory inputs to BLAGlu neurons and their roles in mediating different aspects of pain are unclear. Here, we identified two discrete glutamatergic neuronal circuits in male mice: a projection from the insular cortex glutamatergic (ICGlu) to BLAGlu neurons, which modulates both the somatosensory and affective components of pain, and a projection from the mediodorsal thalamic nucleus (MDGlu) to BLAGlu neurons, which modulates only the aversive-affective component of pain. Using whole-cell recording and fiber photometry, we found that neurons within the IC→BLA and MD→BLA pathways were activated in mice upon inflammatory pain induced by injection of complete Freund’s adjuvant (CFA) into their paws. Optical inhibition of the ICGlu→BLA pathway increased the nociceptive threshold and induced behavioral place preference in CFA mice. In contrast, optical inhibition of the MDGlu→BLA pathway did not affect the nociceptive threshold but still induced place preference in CFA mice. In normal mice, optical activation of the ICGlu→BLA pathway decreased the nociceptive threshold and induced place aversion, while optical activation of the MDGlu→BLA pathway only evoked aversion. Taken together, our results demonstrate that discrete ICGlu→BLA and MDGlu→BLA pathways are involved in modulating different components of pain, provide insights into its circuit basis, and better our understanding of pain perception. 相似文献
996.
BackgroundRadiation therapy (RT) is often utilized in cases of high-grade soft tissue sarcoma (STS), but there remain situations where treatment is with surgical excision alone. Our goals were to determine (1) the local recurrence (LR) rate with and without perioperative RT and (2) associations between local recurrence, patient, tumor, and treatment variables.MethodsWe performed a retrospective review of 165 consecutive STS patients. A Cox proportional hazards model was used to investigate variables associated with local recurrence.ResultsLR occurred in 15/78 (19%) without RT, 4/29 (14%) with postoperative RT, and 0/58 with preoperative RT (p=0.002). We found increased rates of local recurrence at 24 months for myxofibrosarcoma (p=0.001) and no-RT (p=0.003). Myxofibrosarcoma accounted for 33 (20%) of the study patients and 12 (63%) of the local recurrences.ConclusionThe LR rate in patients treated with surgery alone was disproportionately attributable to myxofibrosarcoma (11/23 cases, 48%). Other subtypes demonstrated a lower rate of LR in the absence of RT (4/55 cases, 7%), and no LR occurred when final margins were >2 mm. In certain circumstances treatment with a negative margin surgical resection followed by close observation is justifiable. RT is effective and should continue to be considered routinely in myxofibrosarcoma or when surgical margins are inadequate. Level of Evidence: III 相似文献
997.
外泌体是多种活细胞经过"内吞-融合-外排"等一系列过程主动向胞外分泌的纳米级双层膜结构小囊泡,广泛存在于血液和尿液等生物体液中.因其携带着多种蛋白质、核酸和脂质等生物活性分子,所以外泌体不仅在细胞间物质交换和信息传递中发挥重要作用,而且对疾病诊断、预后预测和治疗管理等均具有提示意义.外泌体的高效提取、分离和完整保存是研... 相似文献
998.
999.
长江安庆段江豚主要栖息地鱼类群落结构 总被引:16,自引:3,他引:13
长江皖河交汇处(皖河口)是安庆江段江豚主要的栖息地之一。为了解江豚主要栖息地鱼类群落结构,于2013年9月—2014年8月对皖河口及其附近4个断面逐月进行了鱼类调查。研究结果表明,共采集鱼类35种,与历史资料相比,鱼类物种多样性已经严重下降,并且小型化趋势明显。5个断面当中,皖河口鱼类种数最多,为27种,且以中上层鱼类餐和油餐为主要优势种;其余4个断面分别为16、20、19和14种,且多数断面以底层鱼类黄颡鱼和长须黄颡鱼为主要优势种。方差分析结果表明,皖河口渔获物的总数量和总重量与其他断面无显著差异,但总种数却显著高于断面1和5。对中上层、中下层和底层鱼类的进一步分析发现,5个断面的显著差异仅存在于中上层鱼类,且皖河口中上层渔获物的数量和重量均显著高于其他断面。由此推断,江豚选择皖河口作为主要栖息地可能主要由于其更加丰富的中上层鱼类资源。研究结果不仅有助于了解鱼类资源的变化,还对江豚的原地和迁地保护具有重要意义。 相似文献
1000.
大兴安岭北坡多年冻土区植物群落分类及其物种多样性对冻土融深变化的响应 总被引:1,自引:0,他引:1
气候变化背景下冻土环境对地上植物群落的影响备受关注。鉴于此,选择了大兴安岭北坡作为研究区,应用双向指示种分析(TWINSPAN)和典范对应分析法(CCA)对大兴安岭北坡不同冻土融深的30个样地进行了群落分类,分析了物种多样性对冻土融深的响应。结果表明,1)研究区30个沟谷冻土样地植物群落可划分为3个群丛组,TWINSPAN的分类结果很好的反映了群丛组的分布与冻土融深的关系,即随着冻土融深由浅变深,群落由柴桦(Betula fruticosa)+狭叶杜香(Ledum palustrevar.angustum)-苔草(Carex subpediformis)群丛组逐渐过渡到柴桦(Betula fruticosa)-苔草(Carex subpediformis)群丛组和柴桦(Betula fruticosa)+细叶沼柳(Salix rosmarinifolia)-苔草(Carex subpediformis)群丛组,并在CCA二维排序图上得到了验证;2)地上植物群落的物种多样性指数随着冻土融深的增加表现出先上升后下降的单峰变化趋势;在50cmPMD≤150cm时,物种多样性指数较高。研究结果对冻土区的森林管理以及生物多样性保护具有一定地指导意义。 相似文献