全文获取类型
收费全文 | 5669篇 |
免费 | 51篇 |
国内免费 | 1篇 |
专业分类
林业 | 272篇 |
农学 | 243篇 |
基础科学 | 19篇 |
1011篇 | |
综合类 | 618篇 |
农作物 | 589篇 |
水产渔业 | 443篇 |
畜牧兽医 | 2116篇 |
园艺 | 74篇 |
植物保护 | 336篇 |
出版年
2024年 | 54篇 |
2023年 | 40篇 |
2022年 | 90篇 |
2021年 | 117篇 |
2020年 | 106篇 |
2019年 | 109篇 |
2018年 | 137篇 |
2017年 | 161篇 |
2016年 | 186篇 |
2015年 | 166篇 |
2014年 | 201篇 |
2013年 | 285篇 |
2012年 | 351篇 |
2011年 | 421篇 |
2010年 | 224篇 |
2009年 | 224篇 |
2008年 | 315篇 |
2007年 | 301篇 |
2006年 | 269篇 |
2005年 | 250篇 |
2004年 | 232篇 |
2003年 | 191篇 |
2002年 | 203篇 |
2001年 | 144篇 |
2000年 | 119篇 |
1999年 | 77篇 |
1998年 | 33篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 21篇 |
1993年 | 21篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 33篇 |
1989年 | 37篇 |
1988年 | 30篇 |
1987年 | 40篇 |
1986年 | 18篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1978年 | 21篇 |
1977年 | 19篇 |
1976年 | 28篇 |
1974年 | 20篇 |
1973年 | 22篇 |
1972年 | 22篇 |
1971年 | 15篇 |
排序方式: 共有5721条查询结果,搜索用时 15 毫秒
81.
Ion control of nutrient solutions to control nitrogen (N), phosphorus (P), and potassium (K) was developed for Superior (medium-to-early maturing) and Atlantic (mid-late) potato cultivars grown in closed hydroponic systems in which solutions were replenished and recirculated. Results were compared with conventional nutrient solution management strategies. In the “solution replacement” treatment, nutrient solutions were completely replaced each week. In the “electrical conductivity (EC) control” treatment, water use by potato plants was compensated by adding ground water to achieve the original volume (water replenishment) and the diluted EC of the solution was adjusted to the target levels using stock solution. In “ion control” treatment, ammonium dihydrogen phosphate (NH4H2PO4) and potassium nitrate (KNO3) were added to the EC-controlled nutrient solution. The amounts increased with plant age in both cultivars. The concentrations of nitrate (NO3), P, and K in the ion control nutrient solution could be maintained at target levels. In water replenishment, recycling of nutrient solution resulted in a progressive decrease in EC and an increase in pH. Root activity increased by 93% and 59% in the Superior and Atlantic cultivars, respectively, compared with the nutrient solution replacement. These changes decreased photosynthesis, plant growth, water use, and thus tuber growth in the Superior cultivar. Decreased growth of shoots and tubers occurred without affecting photosynthesis in the Atlantic cultivar. Although there were no significant differences in root activity, photosynthesis, or plant growth between the ion control treatment and the EC control treatment, increased tuber growth was observed in the ion control treatment, possibly as a result of the constant supply of nutrients. High tuber growth and the capability to maintain solution nutrient concentration in the ion control treatment are highly desirable for closed hydroponic systems. 相似文献
82.
This study was conducted to investigate the effect of steeping conditions of waxy rice, temperatures (15, 25, and 35°C) and time periods (1, 11, and 21 days) on the expansion ratio of gangjung (a traditional Korean oil‐puffed rice snack). Physicochemical properties of waxy rice flour steeped under various conditions and expansion properties of gangjung made of the steeped waxy rice flour were investigated, and multiple regression analyses were applied between those properties to identify major physicochemical factors that optimally predict the expansion ratio of gangjung. As steeping temperature and time periods of waxy rice changed from the lowest to the highest, the expansion ratio of gangjung markedly increased (from 1,022 to 2,533%). Yet, the expansion ratio of the waxy rice sample steeped for 11–21 days at 35°C was not significantly different from the sample steeped for 21 days at 25°C, indicating that the lengthy steeping process for gangjung making can be shortened by increasing the steeping temperature. Physicochemical properties include moisture (γ = 0.85), protein (γ = –0.91), ash (γ = –0.84), potassium (γ = –0.89), magnesium (γ = –0.88), phosphorous (γ = –0.91), peak viscosity (γ = 0.77), and breakdown (γ = 0.94) of steeped waxy rice flour. These properties were highly correlated with expansion ratio (P < 0.01). Multiple regression analysis showed that the expansion ratio of gangjung was predicted successfully by the phosphorous content and breakdown value of steeped waxy rice flour. 相似文献
83.
Rubio DR Kamp LM Heilman M Williams L Rubio FM 《Journal of agricultural and food chemistry》2008,56(17):7606-7612
A competitive enzyme-linked immunoassay (ELISA) for the quantitation of Penoxsulam [2-(2,2-difluoroethoxy)-6-(trifluoromethyl-N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl))benzenesulfonamide] in ground and surface waters was developed. This immunoassay utilizes magnetic particles as the solid phase to which polyclonal rabbit anti-Penoxsulam antibodies are attached. The ELISA has an estimated detection limit of 0.17 ppb (microg/mL) of Penoxsulam in water. Specificity studies indicate that the antibody can distinguish Penoxsulam from its major metabolites and structurally similar pesticides. Interference studies indicate that the ELISA has a wide tolerance of sample pH and salinity and for compounds commonly found in surface and ground waters. The ELISA was shown to compare favorably to LC-MS/MS on ground and surface water samples (r(2) = 0.957). The various studies performed demonstrate the usefulness of the ELISA technique as a rapid and high-throughput analytical method for the cost-effective monitoring of water samples. 相似文献
84.
Zou Y Qian ZJ Li Y Kim MM Lee SH Kim SK 《Journal of agricultural and food chemistry》2008,56(16):7001-7009
Three phlorotannins, including phloroglucinol, diphlorethohydroxycarmalol, and 6,6'-bieckol, were isolated from Ishige okamurae by column chromatography. The structures of the phlorotannins were determined on the basis of spectroscopic analysis, including NMR and mass spectrometry (MS) techniques. Antioxidant effects of phlorotannins were measured by direct free radical scavenging activities using the electron spin resonance spectrometry (ESR) technique and cellular systems in vitro. The results indicated that diphlorethohydroxycarmalol and 6,6'-bieckol showed potential radical scavenging activities against the 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, alkyl, and superoxide radicals. Moreover, no cytotoxicities of the phlorotannins on human fetal lung fibroblasts cell line (MRC-5), mouse macrophages cell line (RAW264.7), and human leukemic cell line (HL-60) were observed. In addition, diphlorethohydroxycarmalol and 6,6'-bieckol significantly reduced the intracellular reactive oxygen species level assessed by 2',7'-dichlorofluorescein diacetate (DCFH-DA) assay in RAW264.7 cells, and myeloperoxide (MPO) activity in HL-60 cells and radical-mediated oxidation of cell membrane proteins in RAW264.7 cells were dose-dependently inhibited in the presence of diphlorethohydroxycarmalol and 6,6'-bieckol. In conclusion, these results suggested that phlorotannins could be used as novel functional foodstuffs or antioxidants in the cosmetic and drug industries. 相似文献
85.
86.
87.
Local manipulation of electric fields at the atomic scale may enable new methods for quantum transport and creates new opportunities for field control of ferromagnetism and spin-based quantum information processing in semiconductors. We used a scanning tunneling microscope to position charged arsenic (As) vacancies in the gallium arsenide 110 [GaAs(110)] surface with atomic precision, thereby tuning the local electrostatic field experienced by single manganese (Mn) acceptors. The effects of this field are quantified by measuring the shift of an acceptor state within the band gap of GaAs. Experiments with varying tip-induced band-bending conditions suggest a large binding energy for surface-layer Mn, which is reduced by direct Coulomb repulsion when the As vacancy is moved nearby. 相似文献
88.
Goo Jang So Gun Hong Byeong Chun Lee 《Journal of veterinary science (Suw?n-si, Korea)》2011,12(1):83-89
Somatic cell nuclear transfer (SCNT) is considered to be a critical tool for propagating valuable animals. To determine the productivity calves resulting from embryos derived with different culture media, enucleated oocytes matured in vitro were reconstructed with fetal fibroblasts, fused, and activated. The cloned embryos were cultured in modified synthetic oviduct fluid (mSOF) or a chemically defined medium (CDM) and developmental competence was monitored. After 7 days of culturing, the blastocysts were transferred into the uterine horn of estrus-synchronized recipients. SCNT embryos that were cultured in mSOF or CDM developed to the blastocysts stages at similar rates (26.6% vs. 22.5%, respectively). A total of 67 preimplantational stage embryos were transferred into 34 recipients and six cloned calves were born by caesarean section, or assisted or natural delivery. Survival of transferred blastocysts to live cloned calves in the mSOF and the CDM was 18.5% (to recipients), 9.6% (to blastocysts) and 42.9% (to recipients), 20.0% (to blastocysts), respectively. DNA analysis showed that all cloned calves were genetically identical to the donor cells. These results demonstrate that SCNT embryos cultured in CDM showed higher viability as judged by survival of the calves that came to term compared to blastocysts derived from mSOF cultures. 相似文献
89.
Park WT Kim JK Park S Lee SW Li X Kim YB Uddin MR Park NI Kim SJ Park SU 《Journal of agricultural and food chemistry》2012,60(33):8111-8116
We profiled and quantified glucosinolates, anthocyanins, carotenoids, and other secondary metabolites in the skin and flesh of pale green and purple kohlrabis. Analysis of these distinct kohlrabis revealed the presence of 8 glucosinolates, 12 anthocyanins, 2 carotenoids, and 7 phenylpropanoids. Glucosinolate contents varied among the different parts and types of kohlrabi. Glucoerucin contents were 4-fold higher in the flesh of purple kohlrabi than those in the skin. Among the 12 anthocyanins, cyanidin 3-(feruloyl)(sinapoyl) diglucoside-5-glucoside levels were the highest. Carotenoid levels were much higher in the skins than the flesh of both types of kohlrabi. The levels of most phenylpropanoids were higher in purple kohlrabi than in pale green ones. trans-Cinnamic acid content was 12.7-fold higher in the flesh of purple kohlrabi than that in the pale green ones. Thus, the amounts of glucosinolates, anthocyanins, carotenoids, and phenylpropanoids varied widely, and the variations in these compounds between the two types of kohlrabi were significant. 相似文献
90.
Cha KH Lee JY Song DG Kim SM Lee DU Jeon JY Pan CH 《Journal of agricultural and food chemistry》2011,59(16):8670-8674
Chlorella is a nutrient-rich microalga that contains protein, lipid, minerals, vitamins, and high levels of lutein. This study evaluated the bioavailability of lutein from Chlorella vulgaris using a coupled in vitro digestion and human intestinal Caco-2 cell model. Lutein bioaccessibility was low, and approximately 75% of total C. vulgaris lutein was not micellized during the digestion process but remained in the insoluble digestate. Microfluidization improved lutein micellization efficiency during C. vulgaris digestion. C. vulgaris was microfluidized at a pressure exceeding 10000 psi, and the cell surface disruption was visualized by scanning electron microscopy. The mean C. vulgaris particle size was reduced from 3.56 to 0.35 μm with the microfluidization treatment. C. vulgaris microfluidization at 20000 psi was three times more efficient for aqueous lutein micelles production as compared with untreated C. vulgaris, and the final lutein content accumulated by intestinal Caco-2 cells was also higher with microfluidization. C. vulgaris lutein stability was not affected by microfluidization. These results indicate that microfluidization may be useful for improving lutein bioaccessibility from C. vulgaris during food processing. 相似文献