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101.
应用多项式的完全判别系统,以分类的形式给出2+1维非线性KDV方程组的单行波解,这个方法能够获得方程组的全部精确解,其中一部分是新解。同时通过赋予方程中参数具体数值,构造出单行波解的具体结构和波形图。 相似文献
102.
为了探究丰枯水期里下河腹地典型水体中浮游动物的群落结构特征,通过布设20个采样站点,于2014年丰水期(7月29日)和枯水期(12月24日)对里下河腹地典型水体进行了2次全面调查,并对水质状况进行了评价。结果表明,里下河腹地典型水体共鉴定出浮游动物21种(包括变种和变型),无节幼体1类;其中轮虫最多,共14种,占浮游动物总种数的66.6%;枝角类次之,共6种,占28.6%;桡足类最少,仅1种,占4.8%;各站点浮游动物种类组成和密度均以轮虫和枝角类为主,数量在5~15种,密度变化在9.8~102.2个/L。浮游动物相似性指数在0.18~0.55,平均为0.36,偏向于轻度相似,表明丰水期与枯水期的生境差异较大。优势种的优势度不高,在0.023~0.297;多样性指数在1.73~3.56,均匀度指数在0.67~0.95,表明丰、枯水期里下河腹地典型水体的浮游动物群落信息含量较大、群落结构处于较稳定状态。浮游动物多样性和水质监测结果均表明,枯水期水质优于丰水期,枯水期水质基本处于清洁状态,丰水期水质基本处于中度污染状态;污染源主要为面源污染,且串场河(6号)、新通扬运河(12号)、喜鹊湖(17号)、兴姜河(18号)受人类活动影响较大。 相似文献
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Jia-Rui Wu Fang-Ji Xu Wei Cao Wei Zhang Chuan-Chao Dai 《Archives of Agronomy and Soil Science》2019,65(2):240-252
Previously, the application of the fungal endophyte Phomopsis liquidambari B3 exhibited notable effect in alleviating soil obstacles caused by continuous cropping of peanut. It was supposed that P. liquidambari B3 could enhance the efficiency of nodulation and nitrogen fixation by enriching the diversity of nodular endophytic bacteria under continous monocropping system. To verify this hypothesis, a pot experiment was conducted under natural conditions. Four treatments were set as follow: discontinuous cropping soil (NS), continuous cropping soil (CK), continuous cropping soil inoculate with actived P. liquidambari B3 (CSB3), and continuous cropping soil inoculate with sterilized P. liquidambari B3 (CSIB3). As a result, a total of 120 isolates were obtained. Our study clearly declared that the addition of fungal endophyte effectively enriched the genetic diversity and the community composition in CSB3. In contrast, a low genetic diversity level and simplex community structure were exhibited in CK and CSIB3. Meanwhile, the positive percentage rate and corresponding community composition of the plant growth-promoting isolates in NS and CSB3 were larger and more abundant than the other. This is the first time to describe the effects of fungal endophytes on the diversity of the nodular culturable endophytic bacteria associated with continuous cropping of peanut. 相似文献
104.
Zhaohua Dai Carl C. Trettin Changsheng Li Harbin Li Ge Sun Devendra M. Amatya 《Water, air, and soil pollution》2012,223(1):253-265
Emissions of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from a forested watershed (160 ha) in South Carolina, USA, were estimated with a spatially explicit watershed-scale modeling
framework that utilizes the spatial variations in physical and biogeochemical characteristics across watersheds. The target
watershed (WS80) consisting of wetland (23%) and upland (77%) was divided into 675 grid cells, and each of the cells had unique
combination of vegetation, hydrology, soil properties, and topography. Driven by local climate, topography, soil, and vegetation
conditions, MIKE SHE was used to generate daily flows as well as water table depth for each grid cell across the watershed.
Forest-DNDC was then run for each cell to calculate its biogeochemistry including daily fluxes of the three greenhouse gases
(GHGs). The simulated daily average CH4, CO2 and N2O flux from the watershed were 17.9 mg C, 1.3 g C and 0.7 mg N m−2, respectively, during the period from 2003–2007. The average contributions of the wetlands to the CH4, CO2 and N2O emissions were about 95%, 20% and 18%, respectively. The spatial and temporal variation in the modeled CH4, CO2 and N2O fluxes were large, and closely related to hydrological conditions. To understand the impact of spatial heterogeneity in
physical and biogeochemical characteristics of the target watershed on GHG emissions, we used Forest-DNDC in a coarse mode
(field scale), in which the entire watershed was set as a single simulated unit, where all hydrological, biogeochemical, and
biophysical conditions were considered uniform. The results from the field-scale model differed from those modeled with the
watershed-scale model which considered the spatial differences in physical and biogeochemical characteristics of the catchment.
This contrast demonstrates that the spatially averaged topographic or biophysical conditions which are inherent with field-scale
simulations could mask “hot spots” or small source areas with inherently high GHGs flux rates. The spatial resolution in conjunction
with coupled hydrological and biogeochemical models could play a crucial role in reducing uncertainty of modeled GHG emissions
from wetland-involved watersheds. 相似文献
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108.
玉米果穗剥皮辊型及其主要参数优选试验 总被引:1,自引:1,他引:1
在前人研究基础上,用实验法在室内专用试验台架上对玉米果穗剥皮辊型及其主要运动与结构参数进行多指标正交试验,以求进一步摸清各参数对剥皮性能影响程度及其变化规律,寻求较优参数组合,为研究设计米果穗剥皮机械提供科学依据。 相似文献
109.
介绍了混合动力电动汽车(HEV)的概念、HEV动力总成的组成及型式,以丰田PRIUS为例阐述了HEV的工作原理。 相似文献
110.