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1.
Eukaryotic protein kinases are typically strictly controlled by second messenger binding, protein/protein interactions, dephosphorylations or similar processes. None of these regulatory mechanisms is known to work for protein kinase CK2 (former name “casein kinase 2”), an acidophilic and constitutively active eukaryotic protein kinase. CK2 predominantly exists as a heterotetrameric holoenzyme composed of two catalytic subunits (CK2α) complexed to a dimer of non-catalytic subunits (CK2β). One model of CK2 regulation was proposed several times independently by theoretical docking of the first CK2 holoenzyme structure. According to this model, the CK2 holoenzyme forms autoinhibitory aggregates correlated with trans-autophosphorylation and driven by the down-regulatory affinity between an acidic loop of CK2β and the positively charged substrate binding region of CK2α from a neighboring CK2 heterotetramer. Circular trimeric aggregates in which one-half of the CK2α chains show the predicted inhibitory proximity between those regions were detected within the crystal packing of the human CK2 holoenzyme. Here, we present further in vitro support of the “regulation-by-aggregation” model by an alternative crystal form in which CK2 tetramers are arranged as approximately linear aggregates coinciding essentially with the early predictions. In this assembly, the substrate binding region of every CK2α chain is blocked by a CK2β acidic loop from a neighboring tetramer. We found these crystals with CK2Andante that contains a CK2β variant mutated in a CK2α-contact helix and described to be responsible for a prolonged circadian rhythm in Drosophila. The increased propensity of CK2Andante to form aggregates with completely blocked active sites may contribute to this phenotype.  相似文献   
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Unique species of ceramide (Cer) with very-long-chain polyunsaturated fatty acid (VLCPUFA), mainly 28–32 carbon atoms, 4–5 double bonds, in nonhydroxy and 2-hydroxy forms (n-V Cer and h-V Cer, respectively), are generated in rat spermatozoa from the corresponding sphingomyelins during the acrosomal reaction. The aim of this study was to determine the properties of these sperm-distinctive ceramides in Langmuir monolayers. Individual Cer species were isolated by HPLC and subjected to analysis of surface pressure, surface potential, and Brewster angle microscopy (BAM) as a function of molecular packing. In comparison with known species of Cer, n-V Cer and h-V Cer species showed much larger mean molecular areas and increased molecular dipole moments in liquid expanded phases, which suggest bending and partial hydration of the double bonded portion of the VLCPUFA. The presence of the 2-hydoxyl group induced a closer molecular packing in h-V Cer than in their chain-matched n-V Cer. In addition, all these Cer species showed liquid-expanded to liquid-condensed transitions at room temperature. Existence of domain segregation was confirmed by BAM. Additionally, thermodynamic analysis suggests a phase transition close to the physiological temperature for VLCPUFA-Cers if organized as bulk dispersions.  相似文献   
5.
目的探讨中枢神经系统感染患者脑脊液和血清中MMP-2(基质金属蛋白2)、MMP-9(基质金属蛋白9)、MCP-1(单核细胞趋化蛋白-1)表达的意义。方法选取2012年12月至2014年5月我院收治的中枢神经系统感染患者60例,其中结核性脑膜炎组(TBM组)、化脓性脑膜炎组(PM组)、真菌性脑膜炎组(CM组)和病毒性脑膜炎组(VM组)各15例;另外选取同期健康体检者15例作为对照组。治疗前、治疗后检测5组患者脑脊液常规及生化,采用ELISA法检测其脑脊液及血清中MMP-2、MMP-9、MCP-1的表达,并对患者进行格拉斯哥昏迷评分(GCS),分析其内在联系。结果治疗前、治疗后TBM组、PM组、CM组和VM组的脑脊液细胞数、蛋白水平均高于对照组,且TBM组、PM组的脑脊液细胞数、蛋白水平均高于CM组和VM组(P0.05);治疗前、治疗后TBM组、PM组、CM组和VM组的脑脊液糖水平、GCS评分低于对照组,治疗前TBM组、PM组、CM组、VM组的脑脊液氯化物水平低于对照组(P0.05);治疗后四组与对照组在脑脊液氯化物水平以及GCS评分等方面的差异无统计学意义(P0.05);治疗前、治疗后TBM组、PM组、CM组、VM组的脑脊液和血清中MMP-2、MMP-9、MCP-1水平均显著高于对照组,且治疗前TBM组、PM组的脑脊液和血清中MMP-2、MMP-9、MCP-1水平均显著高于CM组、VM组以及对照组(P0.05);治疗后PM组、CM组、VM组的脑脊液和血清中MMP-2、MMP-9、MCP-1水平的差异无统计学意义(P0.05);经Pearson进行相关性分析,BM组、PM组、CM组以及VM组的脑脊液和血清中MMP-2、MMP-9、MCP-1表达均与GCS评分负相关(相关系数r=-0.859~-0.574,P0.05)。结论中枢神经系统感染患者脑脊液和血清中MMP-2、MMP-9、MCP-1表达均与GCS评分相关,动态检测脑脊液和血清中MMP-2、MMP-9、MCP-1表达均对中枢神经系统感染的诊断和判断预后有积极意义。  相似文献   
6.
  1. The analysis of functional groups with a resolution to the individual species level is a basic requirement to better understand complex interactions in aquatic food webs. Species‐specific stable isotope analyses are currently applied to analyse the trophic role of large zooplankton or fish species, but technical constraints complicate their application to smaller‐sized plankton.
  2. We investigated rotifer food assimilation during a short‐term microzooplankton bloom in the East African soda lake Nakuru by developing a method for species‐specific sampling of rotifers.
  3. The two dominant rotifers, Brachionus plicatilis and Brachionus dimidiatus, were separated to single‐species samples (purity >95%) and significantly differed in their isotopic values (4.1‰ in δ13C and 1.5‰ in δ15N). Bayesian mixing models indicated that isotopic differences were caused by different assimilation of filamentous cyanobacteria and particles <2 μm and underlined the importance of species‐specific sampling of smaller plankton compartments.
  4. A main difference was that the filamentous cyanobacterium Arthrospira fusiformis, which frequently forms blooms in African soda lakes, was an important food source for the larger‐sized B. plicatilis (48%), whereas it was hardly ingested by B. dimidiatus. Overall, Afusiformis was, relative to its biomass, assimilated to small extents, demonstrating a high grazing resistance of this species.
  5. In combination with high population densities, these results demonstrate a strong potential of rotifer blooms to shape phytoplankton communities and are the first in situ demonstration of a quantitatively important direct trophic link between rotifers and filamentous cyanobacteria.
  相似文献   
7.
Aquatic organisms such as cichlids, coelacanths, seals, and cetaceans are active in UV–blue color environments, but many of them mysteriously lost their abilities to detect these colors. The loss of these functions is a consequence of the pseudogenization of their short wavelength-sensitive (SWS1) opsin genes without gene duplication. We show that the SWS1 gene (BdenS1ψ) of the deep-sea fish, pearleye (Benthalbella dentata), became a pseudogene in a similar fashion about 130 million years ago (Mya) yet it is still transcribed. The rates of nucleotide substitution (~ 1.4 × 10− 9/site/year) of the pseudogenes of these aquatic species as well as some prosimian and bat species are much smaller than the previous estimates for the globin and immunoglobulin pseudogenes.  相似文献   
8.
气候变化对鄱阳湖白鹤越冬种群数量变化的影响   总被引:2,自引:0,他引:2  
分析了1983—2011年鄱阳湖国家级自然保护区越冬白鹤种群数量的年际变化趋势,检验了白鹤种群动态与繁殖地和越冬地气候变化的相关性,气候变量包括月平均气温、月平均最高气温、月平均最低气温和月降水量。研究结果表明,鄱阳湖国家级自然保护区内的白鹤年最大数量平均为(2 130±153)只,呈显著地线性增长趋势(R2=0.454,F=22.441,df=28,P=0.000),但年际波动较大。在越冬地,越冬当年10月、11月、12月的气候变量与白鹤种群数量没有显著的相关性,但越冬初期10月份和越冬后期翌年3月份的气温变量与第4年、第5年、第6年及第7年的白鹤种群数量存在显著的正相关,表明越冬地气候对白鹤种群大小的影响存在时滞效应。越冬初期和末期可能是白鹤补充能量的关键阶段,而且越冬初期的气候可能也与冬季食物的数量或质量相关,因此这两个阶段的适宜气温可能有利于个体尤其是幼鹤的存活,使更多的个体参加繁殖,由于白鹤的性成熟年龄在3—5a,因此其对白鹤种群增长的有利影响会在3a以后表现出来。白鹤种群数量变化与繁殖地繁殖期的降水量没有显著的相关性,而与7月份的气温变量存在显著的正相关。多元线性回归分析结果表明,6a前的10月份平均最低温度、2a前的10月最高温度及5a前的10月平均气温是白鹤种群数量变化的显著预测因子,共同解释了鄱阳湖国家级自然保护区白鹤种群数量变化的74.8%(F=23.807,df=27,P=0.000)。  相似文献   
9.
人类活动与气候变化对洪湖春旱的影响   总被引:1,自引:0,他引:1  
刘可群  梁益同  周金莲  刘敏 《生态学报》2014,34(5):1302-1310
近年来洪湖地区干旱事件频繁发生,对该地区农业生产与生态环境造成了极大影响。利用1960—2011年气候资料、近30年洪湖水文、土地利用资料,采用湖泊水量平衡方法、统计学等方法,研究分析了人类活动和气候变化对洪湖春季干旱的影响。结果表明:伴随全球气候变化该地区年降水和夏季降水呈增加趋势,而春季降水尤其是春季少雨年的降水量减少趋势明显,其减少速率为12.57 mn/10a,达到了α=0.1显著水平;洪湖5月水位高度依赖春季降水,降水对它贡献率为0.36 m/100mm。近20年来,洪湖周边两县市水产养殖面积增加了7倍,在降水偏少时,农业灌溉需水量20a增加了4.14×10~8m~3以上;水产养殖消耗大量春季水资源,对洪湖5月水位的影响率为-0.158 m/10~4hm~2,达到了0.1的显著性水平。人类活动与气候变化是洪湖春旱增多加重两个重要原因,比较它们的变化量与影响率,人类活动对洪湖春旱的影响更大。为维护洪湖生态功能,减轻干旱影响,必须调整农业结构。  相似文献   
10.
黄土丘陵区生物土壤结皮表面糙度特征及影响因素   总被引:1,自引:0,他引:1  
地表糙度是影响地表径流和侵蚀过程的重要属性.生物结皮在干旱半干旱区广泛分布,是地表糙度的影响因子之一.本文采用链条法测定了黄土丘陵区不同发育阶段生物结皮表面糙度特征,分析了不同发育阶段生物结皮表面糙度对坡向、土壤含水量和冻融作用的响应及其与各理化性质的相关性,初步探索了生物结皮对地表糙度的影响及其相关因素.结果表明: 生物结皮显著改变地表糙度,随着生物结皮从藻结皮向藓结皮演替,其糙度先降低后增加,生物结皮发育形成10年以后,其表面糙度基本趋于稳定;研究区早期形成的藻结皮表面糙度较裸土降低47.0%,深色藻结皮(藓类盖度<20%)较裸土降低20.4%,混生结皮(藓类盖度为20%~60%)和苔藓结皮(藓类盖度>70%)表面糙度与深色藻结皮基本一致;坡向对发育10年以上的生物结皮表面糙度的影响不显著;土壤含水量影响地表糙度特征.研究区浅色藻结皮表面糙度随水分变化较为剧烈;随着生物结皮发育,深色藻结皮、混生结皮和苔藓结皮表面糙度随水分的变化趋于平缓.冻融增加了生物结皮表面糙度.浅色藻结皮经两次冻融后表面糙度增加29.7%;深色藻结皮、混生结皮和藓结皮表面糙度的影响需经过反复冻融才有所体现.生物结皮表面糙度与藓结皮盖度呈显著正相关(P<0.1).  相似文献   
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