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QI WANG CHENG-SEN LI BAO-YIN GENG SHYA CHITALEY 《Botanical journal of the Linnean Society. Linnean Society of London》2003,143(1):55-67
Lepidostrobus xinjiangensis sp. nov. is described from Upper Devonian rocks of the eastern Junggar Basin, Xinjiang, north-west China. It provides new insights into the reproductive diversification and phylogenetic relationships of lycopsids in the Late Devonian. The strobilus shares more characteristics with arborescent lycopsids than any herbaceous forms, and falls within the diagnosis of Lepidostrobus . Each sporophyll consists of a deltoid pedicel and a triangular lamina. Sporophylls are horizontally inserted into the strobilus axis in low spirals. The pedicel, with lateral alations and an abaxial keel, extends distally into the upturned lamina and downturned heel, producing a peltate appearance. A single sporangium with terminal longitudinal dehiscence is a radially elongate, dorsiventrally flattened ovoid and is attached along its length to the adaxial surface of the pedicel. A column-like subarchesporial pad is found in the sporangium. A possible ligule occurs on the adaxial surface of the pedicel distal to the sporangium. The strobilus is microsporangiate, containing Lycospora -type spores with granulate ornamentation and an equatorial flange. Based on this new species, the reproductive diversification and evolutionary pattern in arborescent lycopsids from the Devonian through the Carboniferous are discussed in a phylogenetic framework. We suggest that the reproductive strategies represented by bisporangiate- and monosporangiate-strobili had proliferated by the Late Devonian, which implies that phylogenetically advanced arborescent lycopsids bearing Lepidostrobus strobili had an earlier origin than previously thought. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143 , 55−67. 相似文献
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为研究蛋白质O-甘露糖转移酶-1(Protein O-mannosyltransferase-1,Pmt1p)与Pmt5p基因对酵母细胞寿命的影响,采用一步基因置换法构建PMT5基因缺失菌株(pmt5Δ),在此基础上,缺失PMT1基因,构建PMT1和PMT5双基因缺失菌株(pmt1Δpmt5Δ)。显微镜下分离和计数酵母子细胞的数目,统计菌株的复制性寿命;检测细胞吸光度值来评价细胞分裂增殖速度。结果发现,与对照组酵母细胞的平均复制性寿命(25代)比较,pmt5Δ菌株(26代)的寿命无明显变化(P 0. 05),而pmt1Δpmt5Δ菌株(21代)的寿命明显缩短(P 0. 01);热量限制条件下,与对照组酵母细胞比较,pmt5Δ菌株的生长曲线无明显变化,而pmt1Δpmt5Δ菌株的生长曲线低平,细胞分裂增殖减慢。结果表明,PMT1与PMT5双基因缺失明显缩短酵母细胞的寿命,机制可能与细胞的增殖活力下降有关。 相似文献
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以河北山前平原区秸秆还田条件下小麦-玉米轮作体系为研究对象,设置农民习惯、高产高效、再高产和再高产高效4个模式,通过定位试验探讨各栽培模式对3个轮作周期作物产量、土壤硝态氮累积量及氮平衡的影响.结果表明: 小麦、玉米产量均以再高产模式最高,高产高效和再高产高效模式次之,均显著高于农民习惯模式;小麦季和玉米季氮肥利用效率(PFP)均以高产高效模式最高,显著高于其他模式;0~400 cm土体硝态氮累积量在 768.4~1133.3 kg·hm-2之间,其中80%~85%累积在根下90~400 cm土层;4种模式的土壤硝态氮均有明显向下淋移现象,120~150 cm和270~330 cm处均出现了累积峰,以270~330 cm土层硝态氮累积量最大;高产高效模式的土壤硝态氮含量整体水平均低于其他模式,浓度基本维持在30 mg·kg-1以下,在一定程度上能有效缓解环境压力;冬小麦季0~90 cm土体氮素盈余量均小于夏玉米季,并以高产高效模式的氮素表观损失量最低,显著低于其他模式.综合考虑产量、氮肥利用效率、硝态氮累积和氮平衡,以高产高效模式表现最优,但还有一定的提升空间. 相似文献
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长白山白桦林不同演替阶段土壤有机碳组分的变化 总被引:6,自引:0,他引:6
ZHANG Xue HAN Shi-jie WANG Shu-qi GU Yue YUE Lin-yan FENG Yue GENG Shi-cong CHEN Zhi-jie 《生态学杂志》2016,35(2):282
为了解长白山天然针阔混交林群落恢复演替土壤碳储量的变化,采用空间代替时间的方法,选取白桦幼龄林、白桦中龄林、白桦成熟林、阔叶红松成熟林和阔叶红松过熟林5个不同演替序列,研究其土壤总有机碳(SOC)、易氧化有机碳(ROC)、微生物生物量碳(MBC)及颗粒有机碳(POC)含量。结果表明:随着白桦林从早期到晚期的演替,SOC、MBC、ROC、POC以及土壤全氮、全磷和碳氮比(C/N)均呈现先逐渐增加后保持稳定的规律。随着土层深度的增加,SOC、MBC、ROC和POC含量均显著降低(P0.05),5个演替序列内ROC/SOC和POC/SOC的变化范围分别为12.91%~47.95%和14.21%~69.46%。相关分析表明:MBC、ROC和POC含量与土壤总有机碳(SOC)含量呈极显著正相关(P0.01),SOC、MBC、ROC和POC含量与全氮、全磷及碳氮比呈极显著正相关(P0.01)。研究结果为了解白桦林在演替过程中土壤有机碳的稳定性变化和固碳潜力提供数据支持。 相似文献
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Two leafy specimens of Tingia carbonica were collected as impression from
Shanxi formation of Permian, from Inner Mongolia, China. The epidermal structure of its
leaves is reported in this paper. Under SEM, well preserved epidermal cells as well as some
concaves on the surface of large leaves were clearly recognized. The epidermal cells are approximately rectangular in shape, about 100~150 um long and 20~30 um wide. They are
arranged longitudinally parallel to veins. The concaves usually in rows are round or elliptical,
about 0.65~0.35 mm long and 0.2~0.35 mm wide. Density of concaves is about 1.8/
mm2 and no stomata occur inside the concaves. In all probability, this is the upper epidermis. On the other side of the epidermis, anomocytic stomata are scattered irregularly, each with 5~6 epidermal cells around. The stomatal apertures are about 35.8 µm long, and 18.7
um wide, which is organised parallel to the common epidermal cells. As far as shape and size
is concerned, it is similar to that described on the upper epidermis. Density of the stomata is
about 60/mm2. In all Probability, this is the lower epidermis. The ecological preference and
classification of Tingia are discussed according to these new characters of the epidermis andsubordinate struture of the leaf. 相似文献