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901.
亚纳米木粉低能耗的形成机理 总被引:2,自引:0,他引:2
通过对亚纳米木粉形成过程的分析,由细胞壁厚的几何尺寸定量计算亚纳米木纤维在低能耗形成过程中细胞变化的相关数学参数,定性地解释亚纳米木纤维在低能耗形成过程中细胞尺寸变化的数学关系。结果表明,可以由微观变化解释木材亚纳米木纤维尺寸的变化原因,并以试验结果的照片分析来验证此理论。 相似文献
902.
中国木地板企业开展森林认证的思考 总被引:1,自引:1,他引:0
近年来,森林认证发展很快,在国内外日益受到重视,对于木地板企业经营活动的影响也越来越大。木地板企业开展森林认证有利于品牌建设、市场准入、提高市场占有率和获取环保溢价,还有利于规范经营、实现可持续发展以及获得政府及非政府环保组织支持。但是,目前也存在着木地板企业普遍对森林认证的重要性认识不足、开展森林认证能力不足、规模过小、认证间接成本高、存在风险、认证木材供应不足等问题和困难。然而,国内外森林认证发展的大趋势是不会改变的,木地板企业应审时度势,结合自己的具体情况,制定适应森林认证发展的长期发展战略,迎接新的挑战。 相似文献
903.
904.
Spatial variation in respiration from coarse woody debris in a temperate secondary broad-leaved forest in Japan 总被引:1,自引:0,他引:1
We measured the rates of respiration from snags and logs (“coarse woody debris”, CWD) of Japanese red pine (Pinus densiflora Sieb. et Zucc.) to examine the rate of decomposition and CO2 efflux from these materials in a temperate secondary broad-leaved forest in Japan. At this site, a high quantity of CWD of P. densiflora had accumulated as a result of pine wilt disease during the 1970s. Respiration rates were measured using a dynamic closed chamber method combined with an infrared gas analyzer. We measured the respiration rate of 7 samples of snags and 10 samples of logs from August 2003 to January 2004. The responses of the respiration rates of snags (Rsnag) and logs (Rlog) to changing temperature were both exponential and the responses to water content were quadratic, and the same function could be used to estimate annual values of both Rsnag and Rlog. Intensive measurements of water contents of snags and logs showed a marked difference in water content. The mean water content of snags was 20% of log water content. This difference was likely responsible for the observed difference in annual Rsnag and Rlog. The decay rate constants estimated from the respiration rates measurement of snags and logs were 0.019 and 0.081 year−1, respectively. Despite being lower than Rlog, Rsnag was a significant compartment of the CWD carbon budget at this site. 相似文献
905.
Calycophyllum spruceanum (Benth.) Hook. f. ex K. Shum. is an important timber-tree species in the Peruvian Amazon Basin. Markets currently prefer
wood with a uniform, light yellow color, but these preferences may change in the future. As farmers and industry commonly
use wood from young trees, it is important to investigate genetic and environmental variation in juvenile-wood properties
to assess whether tree improvement programs could make adjustments to changing preferences. A provenance/progeny test was
established to evaluate genetic variation in growth and wood properties of young trees, the strength of their genetic control
as well as their interrelationships both at the genetic and the phenotypic level in different planting zones. This paper presents
analyses of variation in wood color at 39 months, and their correlations with tree growth and wood basic density. CIELab means
for lightness ranging from black to white (L), green to red hues (a*) and blue to yellow hues (b*) were 67.63, 5.34 and 22.12,
respectively; means for chroma (C) and hue angle (h)* were 22.76 and 76.43, respectively (C and h* were estimated from a*
and b*). Significant variation due to provenances and especially due to families within provenances was found in some wood
color characteristics, and some color characteristics also differed significantly among planting zones. Genetic correlations
indicate that, in general, selection of faster growing trees and/or trees with denser wood would have little effect on wood
color and its uniformity. In general, wood color had relatively low heritability (h
i
2): among all trees, h
i
2 = 0.31 for L; and variance due to families was not significant for a* and b*. Genetic control of color was highest in the
planting zone where trees grew most rapidly: h
i
2 = 0.48 and 0.52 for a* and b*, respectively; but variance due to families was not significant for L. Results suggest that
selection based on wood color would be more effective in zones with more fertile soils and higher rainfall.
相似文献
906.
Yoshitaka Kubojima Seiichi Kanetani Takeshi Fujiwara Youki Suzuki Mario Tonosaki Hiroshi Yoshimaru Hiroharu Ikegame 《Journal of Wood Science》2008,54(6):443-450
A dead tree of Pinus armandii Franch. var. amamiana (Koidz.) Hatusima (abbreviated to PAAm) was obtained from a natural habitat on Tanega-shima Island and various properties
of its wood were investigated. Grain angle was measured and soft X-ray analysis was undertaken to obtain the density in each
annual ring. Unit shrinkage and dynamic properties were measured by shrinkage, bending, and compression tests. Variations
of wood properties in the radial direction, relationships of wood properties to density, and annual ring width were examined.
Roughly speaking, variations in the radial direction of the grain angle, twist angle by drying, Young’s modulus and strength
in static bending, absorbed energy in impact bending, compressive Young’s modulus, compressive strength, and compressive proportional
limit corresponded to the variation of annual ring width. As a result, it was determined that if PAAm is afforested artificially
for the purposes of lumber production and conservation, the annual rings of logs should not be too widely spaced. Wood properties
of PAAm were similar to those of Japanese black pine (Pinus thunbergii Parl.), which is another representative pine on Tanegashima Island.
This study was presented in part at the 56th Annual Meeting of the Japan Wood Research Society, Hiroshima, August 2007 相似文献
907.
Typical symptoms of rubberwood canker found in East Kalimantan, Indonesia, differ from those of conventional rubberwood peach
canker. Rubberwood canker showed a conspicuous longitudinal canker with exposed xylem that was discolored and decayed. Bark
wounds, resulting from regular tapping, were enclosed within the xylem, and the tissues had become integrated. The characteristics
of abnormal and decayed xylem in this rubberwood canker were analyzed by light microscopy and scanning electron microscopy.
Xylem in the vicinity of the enclosed bark contained fewer vessels of smaller diameter and shorter length, and significantly
wider rays compared with normal xylem. Around the wide growth zones of the canker, axial cells were disoriented and warped
toward the canker zones. In view of the separation among cells, and the concentric degradation of the cell walls starting
from the lumen surfaces, decayed xylem appeared to be caused mainly by white-rot fungal attack. 相似文献
908.
Yuan Zhou Fu-Quan Chen Si Chen Qiong Xiao Hui-Fen Weng Qiu-Ming Yang An-Feng Xiao 《Marine drugs》2021,19(9)
In this work, the physicochemical properties of maleic anhydride (MAH)-modified κ-carrageenan (κCar) (MC) were characterized and compared with those of native κ-carrageenan (NC). The Fourier transform infrared spectrum of MC exhibited that κCar was successfully modified. Thermogravimetric analysis indicated that the thermal stability of MC was decreased. When the degree of substitution was 0.032, MC exhibited a low gel strength (759 g/cm2), gelling temperature (33.3 °C), and dehydration rate (60.3%). Given the excellent film-forming ability of κCar, MC films were then prepared and were found to have better mechanical and barrier properties (UV and water) than NC films. With regard to optical properties, MC films could completely absorb UV light in the range of 200–236 nm. The water contact angle of MC films was higher than that of NC films. Moreover, the elongation at break increased from 26.9% to 163%. These physicochemical property changes imply that MC can be employed in polysaccharide-based films. 相似文献
909.
对利用复合变性玉米淀粉,制造热压型淀粉基水性高分子——异氰酸酯胶黏剂(API)进行了系统的研究。以复合变性淀粉乳液、二元酸、聚乙烯醇、PMDI为主要影响因素,以拉伸剪切强度为评价目标,通过正交试验优化出满足日本JISK6806—1995指标要求的热压型淀粉基API的配方,对影响胶黏剂理化性能的因素进行了系统分析。经验证性试验证明:所优化出的配方具有明显的生产可操作性,交联剂PMDI可不经封闭直接使用,完全能够满足现有的木材胶合制品生产工艺的要求。 相似文献
910.
5种木材腐朽菌的生物学特性及对白桦木材腐朽能力的分析 总被引:2,自引:0,他引:2
用菌丝长度测量法和菌丝体干质量称重法比较了彩绒革盖菌、白囊耙齿菌、桦剥管菌、木蹄层孔菌和黄伞在固体培养基上的生长速度以及在液体培养基中的生物量变化,同时用比色法检测了5种木材腐朽菌中与木质素降解相关的木质素过氧化物酶、锰过氧化物酶、漆酶活性,并利用它们对300株天然成熟白桦样木进行了腐朽木材试验,采用质量损失法测定各木腐菌对白桦木材样本的生物降解能力。结果表明:木材腐朽菌在固体培养基上的生长速度与它在液体培养基中产生的生物量、木质素降解酶活性及其降解木材能力不完全相关;彩绒革盖菌和白囊耙齿菌的生长速度最快,桦剥管菌和木蹄层孔菌中等,黄伞最慢;桦剥管菌的生物量最高,彩绒革盖菌、白囊耙齿菌和木蹄层孔菌生物量中等,黄伞的生物量最低。桦剥管菌不表达木质素过氧化物酶、锰过氧化物酶、漆酶活性,其它4种真菌都表达这3种酶活性。木屑诱导下的3种酶活性普遍高于对照样,白囊耙齿菌的漆酶、木蹄层孔菌和黄伞的木质素过氧化物酶只在木屑诱导下表达,而且生长时间越长,酶活越高。彩绒革盖菌对白桦木材的生物降解能力最强,其次是木蹄层孔菌和桦剥管菌,白囊耙齿菌和黄伞的生物降解能力最弱。 相似文献