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1.
残膜清杂是残膜回收的重要环节,现有机型的清杂装置存在清杂效果差及工作不可靠的缺点。为此,结合夹指链式残膜回收装置的改进设计与试验,提出了一种基于倾斜栅条的清杂装置。通过对该装置清杂机理进行分析,采用Box-Behnken响应面试验设计方法建立起清杂率与栅条间距b、栅条角度α、栅条长度L间的二次回归模型。通过分析模型响应曲面,寻得最优方案,确立了栅条式清杂装置的结构与尺寸。田间试验表明:当栅条间距为75mm、栅条角度为51°、栅条长度为870mm时,清杂率达85.35%。由此证明了优化方案的可行性,可为相关残膜清杂装置的研究提供理论依据。  相似文献   
2.
Three of the most commonly used veterinary antibiotics—enrofloxacin (ENR), sulfamethoxazole (SMX), and oxytetracycline (OTC)—were chosen as representative antibiotics for UV/H2O2 treatments. The objective was to determine the optimization of UV/H2O2 to remove antibiotics from aquaculture discharge water using response surface methodology. The degradation of the antibiotics was investigated under varying UV/H2O2 conditions in environments with different levels of pH, water matrices, humic acid, and constituent ions. The degradation results demonstrated that increasing the H2O2 dosage facilitated ENR degradation at a neutral pH while facilitating degradation of SMX and OTC at a slightly acidic pH. The optimum removal conditions for ENR, which was used in all influential effect experiments and the contact tank experiments, was obtained at 10 mM H2O2, a pretreated COD of 87.51 mg L−1, and an initial pH of 6.15. Among the tested anions, only the presence of Cl- showed slight positive effects on ENR degradation, due to the generation of secondary active radicals. During the reaction, the hydroxyl radical (OH) was present at a higher pH while singlet oxygen (1O2) was slightly present at a lower pH. The experimental results from H2O2 sequential addition indicated that freshly added H2O2 could quench the recently generated OH and therefore a high H2O2 concentration with frequent adding was not necessary. Our contact system reduced the ENR concentration in both the effluent reservoir and in the UV irradiation zone. The overall results supported the use of the UV/H2O2 system to treat remnant antibiotics in the discharge water.  相似文献   
3.
ABSTRACT

Despite near-extinction in the nineteenth century, after efficient restoration measures the population of Eurasian beaver (Castor fiber L.) in Latvia currently is viable and growing. While the ecological effect of the species on water quality and biodiversity is generally positive, the high number of animals in production forests often creates challenges for management. Drainage ditches are among the most favoured habitats of beavers resulting in flooded stands, reduced tree growth and economical losses. The aim of the study was to evaluate the chemical properties of water in forest drainage ditches, affected by beaver activity, and their changes after the dam removal. Chemical composition of surface water in ditches was analysed in sampling points above dam, below dam and in the ditch itself after removal of the dam; results compared to pristine beaver site nearby on a small stream. Results did not show significant differences between concentrations above and below dams. After removal of the dams, significant increase in DOC, N-NO3 -, N-NH4 + and TSS concentrations and significant decrease in TP concentrations were observed in some of the sites. Observed concentrations of all measured parameters were significantly lower in pristine beaver site than in beaver sites on drainage ditches.  相似文献   
4.
【目的】探究pH值和碳氮比对微生物燃料电池脱氮除磷的影响,找出适宜pH值的和碳氮比。【方法】采用单室微生物燃料电池装置,设置不同的阳极液的pH值(W1=5、W2=6、W3=7、W4=8、W5=9);选取pH值=7,设置不同的碳氮比(N1=1∶1、N2=2∶1、N3=4∶1、N4=8∶1、N5=16∶1),共10个处理,测量2个反应周期内输出电压值、COD、氨态氮、硝态氮、总氮和总磷的变化。【结果】在其他条件相同的情况下,只改变阳极液的pH值,输出电压随pH值增大先增大后减小;pH值为8时产电性能最佳,最大电压为204.74 mV;COD、氨态氮、硝态氮、总氮随pH值增大呈先降低后增大的趋势,在pH值为8时,其去除效率最高,分别为74%、38%、93%和58%;在pH值为9时,总磷的去除效率最优为24%。只改变碳氮比时,当碳氮比为4时电压最大,为158.33 mV;COD、氨态氮、硝态氮、总磷的去除率随碳氮比增大先增大后减小,当碳氮比为4时,COD的降解率最大为65%;当碳氮比为2时,氨态氮的降解效率最好为35%;当碳氮比为8时,硝态氮和总磷的去除效率最高,分别为96%和16%;总氮的去除效率随碳氮比的增大而提高,当碳氮比为16时,总氮的去除效率最高,为59%。【结论】碳氮比为4∶1、pH值为8时可以取得较好的脱氮除磷效果。  相似文献   
5.
为了明确黑土长期定位试验土壤搬迁后与新址的融合效果,以一个搬迁土块为研究对象,明确搬迁土块间的接缝处土壤与距接缝处不同距离的中心土壤在理化特性上的不同。结果表明,0~20 cm层次土体中心50 cm处的田间持水量比接缝处高5%,容重低4%,变异系数均明显高于其他层次;20~40 cm层次,土壤的固相率和容重高于其他层次,田间持水量降低,土块横切面各部位物理性质均无明显差别;剖面底部80~100 cm层次接缝处土壤松散缝处的固相率比30 cm和土体中心处低4.3%,液相率低3.1%,气相率高出7.6%,容重下降8.3%。0~40 cm土层的缝处、距缝30 cm和距缝50 cm处的孔隙率均低于40~100 cm层次,其中80~100 cm层次的孔隙率最大,20~40cm孔隙率最低为44.2%;土壤饱和导水率0~20 cm层次为35.3~38.0 cm/d,随着深度的加深呈下降趋势,均小于20cm/d;而80~100 cm层次缝处的饱和导水率值高达144.4 cm/d,是表层土壤的4倍。同一层次搬迁土块缝处与土块中心土壤速效养分无明显差别,缝处全氮含量均高于土块的其他位置,且与距缝30 cm和50 cm处的数值差异均达到显著水平(P0.05);pH随着土层的加深逐渐增大,碱解氮和土壤有机碳含量随着土层的加深而下降。长期定位土壤搬迁5 a后,深层土壤接缝处还处于疏松状态,下层土壤的融合要弱于上层土壤。  相似文献   
6.
This study was conducted to determine the biological filtration capabilities of some culinary herbs co‐cultured with lemon fin barb hybrid in a nutrient film technique (NFT) recirculating aquaponic system. Lemon fin barb hybrid (Hypsibarbus wetmorei ♂ × Barbonymus gonionotus ♀) fingerlings were stocked in twelve 2‐tonne fibreglass tanks at 25 fish per tank and co‐cultured with Chinese celery (Apium graveolens var. secalinum Alef.), coriander (Coriandrum sativum) and peppermint (Mentha × piperita) for seven weeks. The impacts of the waste generated by the fish on the water quality, the filtration capability of the herbs and the ability of fish and herbs to retain nutrients (NPK) were also estimated. All the herbs showed water purifying potentials to varying degrees as significantly lower levels of nitrogenous compounds (NH3‐N, NO3‐N, NO2‐N) were observed after the herbal filtration. The plant growth seemed to be affected by their ability to absorb nutrients and consequently purify the culture medium. Interestingly, the lemon fin barb hybrid also showed significant differences in terms of weight gain, but the nutrient retention among fish treatments was not statistically different. The plants absorbed less phosphorus and potassium than the fish. After computing for the total system percentage of NPK recovered, nitrogen was the most retained nutrient. The peppermint showed superiority in terms of gross biomass and water purifying potential compared to the Chinese celery and coriander.  相似文献   
7.
2018年12月内蒙古农业大学动物医院接收一病犬,其外阴异常增大,生殖道口有淡红色液体流出,触诊阴门内有一肿瘤硬物,表面光滑,呈淡粉色,不规则形状,初步诊断为阴道肿瘤。手术切除后经组织病理学检查,证实为未成熟的畸胎瘤。  相似文献   
8.
构建一种脱氮的无回流生物滤床家庭生活污水处理一体化净化槽,研究其处理效果;改变各区内的曝气形式,形成A/O/A/O的脱氮工艺,通过测定各区COD、NH+4-N、NO-3-N和TN的浓度变化,考察其处理效果。结果表明:随着净化槽各区生物滤床的加入,反应器抗冲击性增强,处理效果明显提高。但A/O/A/O系统中第二级厌氧过程因碳源不足,脱氮效果不佳,改用分段进水后,净化槽不仅运行稳定,而且取得了很好的处理效果,出水COD平均浓度12.3 mg·L~(-1),NH+4-N平均浓度2.7 mg·L~(-1),TN平均浓度13.0mg·L~(-1),均达到国标(GB 18918—2002)一级A标准。A/O/A/O生物滤床新型净化槽不仅在结构上形成一体化,而且由于生物滤床的使用,不需要污泥回流,节省能耗,通过分段进水可以实现过程脱氮。  相似文献   
9.
The effects of the severity and timing of leaf removal(LR) on the amino acids of Sauvignon Blanc grapes and wines were studied during the 2017 growing season. High-performance liquid chromatography(HPLC) was used to analyze the amino acids profiles of grape berries and wines. The basal leaves were removed at three time points(40, 56 and 72 days after flowering, named LR40, LR56 and LR72, respectively) at two severity levels(one at which the first, third, and fifth basal leaves of each shoot were removed(50% level); and another at which the first six basal leaves were removed(100% level)). The results showed that leaf removal had little impact on total soluble solids(°Brix), titratable acidity, pH or berry weight. The LR72-50% treated grapes had higher berry weight, titratable acidity and °Brix than those of the other treatments. The highest concentrations of total amino acids and of total amino acids except proline were detected in LR72-50% treated grapes(2 952.58 and 2 764.36 mg L~(-1), respectively); the lowest were detected in LR72-100% treated grapes(2 172.82 and 2 038.71 mg L~(-1), respectively). LR72-50% treatment significantly promoted the synthesis of aspartic acid, serine, arginine, alanine, aminobutyric acid and proline at both severity levels for grapes, the concentrations of all of these amino acids were increased relative to the control concentrations. The LR72-50%, LR40-100% and LR72-100% treated wines had higher total amino acids concentrations and higher concentrations of some individual amino acids, such as arginine, alanine and serine, than did the control wines. Of all the amino acids studied, glycine, tyrosine, cysteine, methionine and lysine were not significantly influenced by the timing or severity basal defoliation in grapes and wines. The present study reveals the effects of the timing and severity of leaf removal on the amino acids profiles of grapes and wines.  相似文献   
10.
对北京市大兴区北程庄村的土地征占、整建制转居和集体经济产权制度改革进行调研发现,乡村在快速城市化进程中的核心问题是维护和发展农民的财产权利。建议从根本上改变现行的征地思维和征地制度,保障两种土地公有制的平等地位;落实户籍制度改革,全面取消农转居政策;实行集体土地与国有土地同样可以开发建设城市的政策制度;及时撤销“三无村”或“空壳村”的村委会建制,完善撤制乡村集体资产处置办法。  相似文献   
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