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171.
苏柳799,苏柳172制强韧硫酸盐浆的研究 总被引:2,自引:0,他引:2
运用典型硫酸盐法制浆工艺对速生人工林苏柳172、苏柳799制强韧硫酸盐浆性能进行了系统研究,活性碱用量为10% ̄16%,硫化度25%,液比1:4,升温75min至170℃保温120min,研究结果表明,两种试材用碱量均低,在蒸煮至Kappa值20左右时,J172,活性碱用量约为13.1%(Na2O计),J799活性碱用量约为13.8%。细浆得率高达52% ̄53%(对绝干木片),纸浆性能研究结果表明 相似文献
172.
本文用过硫酸盐法,用离子选择性电极测定惚木,黄毛偬木、棘茎楤木、食用土当归、细柱五加、中华五加、吴茱蔓五加和竹节参中的总氮,相对标准偏差为0.69%~10.1%,回收率为96.7%~100%,本方法准确度和精密度比较高,省时,省电.省试剂和环境污染小等。故树木和植物样品的分析,有理由用过硫酸盐法(TPN法)代替凯氏法(TKN法)。 相似文献
173.
174.
以杉木林分优势水平均高作为研究指标,分别建立各林分优势木平均高的生长模型:H_优=A(1—be~-(kt))1/(1-m),以反映生长速度、生长高峰期出现的早晚的综合参数,作为建立生长类型及生长类型识别的模式. 相似文献
175.
四川森林航测和林业遥感回顾与展望(上) 总被引:1,自引:0,他引:1
1953~1959年林业部航测队在四川省袭江下游、金沙江下游、青衣江上游以及川、陕、鄂交界的大巴山林区进行航测航调工作,1956~1958年林业部三、八森林经理调查大队使用航片在四川小金、会东等县及甘、青交界的祁连山林区完成323hm~2的森林经理调查;1959~1983年间森勘一大队使用航片调查总面积达1432万hm~2、森勘二大队调查1211万hm~2;营林调查队1959~1962年使用航片调查设计达128万hm~2。使用航片节省劳力提高工效,便于野外调查作业和小班区划调绘,不受地形限制以及有利于室内检核调绘质量等优点。放大航片象幅,蒙片调绘,内业航片加密,辐射隔网和透视格网转绘技术可提高航片实用性和精度 相似文献
176.
句容低山丘陵秃杉引种试验 总被引:1,自引:0,他引:1
本场引种珍稀树种秃杉7年的试验结果表明,秃杉能适应本地生长,并以杉木适生的优良立地载植较为适宜。采用2年生无务健壮大苗深栽、壅土保墒、合理混交、适度遮萌等措施可使造林成活率达90%以上,5年生幼树生长量达到或超过杉木,具有扩大引种的潜力。 相似文献
177.
ZHANG Baohua HE Yurong ZHOU Hongyi CHENG Genwei Institute of Mountain Hazards & Environment the Chinese Academy of Sciences.Chengdu . China. Department of Geography Liaocheng University Liaocheng . China bhz@ imde. ac.cn 《中国林业科技(英文版)》2003,(1)
The deforestation on large scale in the upper reaches of Yangtze River has caused serious problems of ecosystem and environment. Restoration of the degenerated forest ecosystems is one of the main research fields. Taking Gongga Mountain as an example, degeneration features and existing problems of forest ecosystems are analyzed in this paper, and the measures are also proposed. 相似文献
178.
Cottonwoods occur in riparian areas where water table depth generally varies with the elevation of the adjacent river. Plant adaptation to the riparian zone requires the coordination of root elongation to maintain contact with the water table during the summer decline. We investigated the effects of rate of water decline on growth allocation and concentrations of endogenous gibberellins (GAs) in black cottonwood (Populus trichocarpa Torr. & A. Gray ex Hook.) saplings. Rhizopods were used to achieve water decline rates of 0, 2 and 4 cm day(-1). Root elongation approximately doubled in response to the 2 cm day(-1) treatment, whereas leaf area was reduced. A water decline rate of 4 cm day(-1) led to water stress, as evidenced by reduced growth, increased leaf diffusive resistance, decreased water potential, and leaf senescence and abscission. Endogenous GAs were extracted, purified and analyzed by gas chromatography-selected ion monitoring with internal [(2)H(2)]GA standards. Across the sampled plant organs, GAs were generally highest in shoot tips and sequentially lower in basal stems, root tips, leaves and upper roots; GAs were thus abundant in rapidly growing tissues. Of the GAs measured, GA(1) tended to predominate, followed sequentially by GA(3), GA(8), GA(19), GA(20), GA(29) and GA(4). There was little relationship between GA concentration and growth allocation across the water table decline treatments, although GA(8) was consistently reduced in plants experiencing water table decline. Because GA(8) is the final gibberellin in the metabolic sequence, it might be useful for assessing historic patterns of GAs and growth rate. This study demonstrated changes in growth allocation in response to water table decline, but provided little evidence that endogenous GAs play a primary role in the regulation of root elongation in response to water table decline. 相似文献
179.
若尔盖高原湿地土壤性质对硒有效性的影响 总被引:1,自引:0,他引:1
用等温吸附的方法研究了若尔盖高原广泛分布的泥炭土、沼泽土和风沙土对硒的吸附与解吸,以探讨湿地土壤因素对硒有效性的影响。结果表明,3种土壤还原状态下硒的吸附量均大于氧化态,水溶性硒和交换态硒的解吸量均为氧化态高于还原态,潜在有效硒与此相反,氧化状态有助于提高土壤硒的有效性。土壤pH升高,泥炭土对SeO_3~(2-)-Se的吸附量降低,水溶态硒增加,交换态硒降低,潜在有效硒变化不明显。土壤有机质能大量吸持硒降低其有效性,泥炭土去有机质后对硒的吸附量大幅度下降,水溶性硒和交换态硒量增加,潜在有效性硒量则明显降低。 相似文献
180.
H D Rood W B Buck S P Swanson 《Journal of the Association of Official Analytical Chemists》1988,71(3):493-498
A gas chromatographic method for screening trichothecene mycotoxins in feeds is described. Feed is extracted with acetonitrile-water, and the toxins are purified with charcoal-alumina-Celite, Florisil, and silica mini-columns. Deoxynivalenol (DON), nivalenol (NIV), diacetoxyscirpenol (DAS), T-2 toxin, and their fungal metabolites are hydrolyzed to their corresponding parent alcohols (DON, NIV, scirpentriol, or T-2 tetraol) by alkaline hydrolysis. After derivatization to their pentafluoropropionyl analogs, they are quantitated by capillary gas chromatography with electron capture detection. Identity can be confirmed and sensitivity can be increased by using negative chemical ionization mass spectrometry with no additional sample workup. Recoveries of DAS, DON, and T-2 toxin averaged, respectively, 80, 65, and 85% in corn; 84, 65, and 88% in soybeans; and 70, 57, and 96% in mixed feeds at concentrations ranging from 0.1 to 2.0 ppm. Recoveries of 15-monoacetoxyscirpenol (MAS), HT-2, NIV, and T-2 tetraol were 97, 97, 86, and 56%, respectively, in corn at a concentration of 0.25 ppm: A detection limit of 0.02 ppm in corn, soybeans, and mixed feeds, and 0.05 ppm in silages is estimated. 相似文献