全文获取类型
收费全文 | 960篇 |
免费 | 43篇 |
国内免费 | 2篇 |
专业分类
林业 | 85篇 |
农学 | 67篇 |
基础科学 | 15篇 |
266篇 | |
综合类 | 66篇 |
农作物 | 113篇 |
水产渔业 | 77篇 |
畜牧兽医 | 230篇 |
园艺 | 18篇 |
植物保护 | 68篇 |
出版年
2023年 | 20篇 |
2022年 | 29篇 |
2021年 | 31篇 |
2020年 | 47篇 |
2019年 | 54篇 |
2018年 | 55篇 |
2017年 | 66篇 |
2016年 | 53篇 |
2015年 | 24篇 |
2014年 | 38篇 |
2013年 | 105篇 |
2012年 | 60篇 |
2011年 | 61篇 |
2010年 | 44篇 |
2009年 | 36篇 |
2008年 | 37篇 |
2007年 | 31篇 |
2006年 | 22篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1959年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有1005条查询结果,搜索用时 15 毫秒
941.
Hosseinzadeh AZ 《Pakistan journal of biological sciences: PJBS》2008,11(10):1401-1404
The report presents a 24 year-old man who admitted at the orthopedic center with full-thickness skin avulsion of the right leg, due to his leg being caught under the wheel of a truck and subsequently traumatized. The day after injury, plastic and reconstructive surgery consult was done. After thoroughly irrigation, the 20 cm laceration was repaired above the knee. There was full-thickness skin necrosis below the knee down to the dorsal surface of the right leg (atypical form of skin avulsion). Debridment and graft was performed for the first stage. During the second stage, re-grafting was performed and the gasterocnemious flap was transposed to cover the Tibia bone. This study confirms early Plastic and reconstructive surgery consult from the trauma of lower extremities associated with skin lesion. 相似文献
942.
In seed priming, seeds are soaked in a solution of low water potential and dried back to their original weight. This study was conducted to evaluate the comparative performance of different seed priming treatments and to investigate whether re-drying is essential or not? Seeds of fine grain aromatic rice (Oryza sativa L.) cultivar Super-Basmati were subjected to hardening, osmohardening with CaCl2 and KCl (ψ s ?1.25 MPa) each for 24 h (one cycle), and hydropriming and ascorbate priming (10 mg L?1) for 48 h. Seeds were primed in two sets. In one set after each treatment, seeds were given three surface washings with distilled water and dried back near to original moisture contents with forced air. In the other case, after surface washings with distilled water, seeds were surface dried using blotting paper and sown immediately. All the priming treatments improved the emergence, seedling growth and reserve metabolism. Use of surface drying was more effective for rice seed invigoration, as evident from earlier and synchronized seedling emergence. Moreover, shoot and root length, seedling dry weight, root score, α-amylase activity, soluble sugars and dehydrogenase activity were also improved, although germination percentage and leaf score were similar from both strategies. Results suggested that surface drying, rather than re-drying close to original weight, was more effective, while among the treatments, osmohardening with CaCl2 was the most effective. Increasing rice production with judicious use of water is need of the day, and aerobic rice cultivation is an attractive alternative for this purpose. However, poor and erratic stand establishment is one of the major hindrances in its wide scale adoption. In this regard, seed priming techniques are pragmatic approaches to achieve proper stand establishment in the new rice culture. They help in improving seedling density per unit area under optimal and adverse soil conditions and may be opted to improve the performance of aerobic rice. 相似文献
943.
In the tropical arid and semi-arid regions of many developing countries, sheep are predominantly grazed on low-quality pastures and stall-fed on crop residues. This study evaluated the potential of Grewia oppositifolia tree leaves as crude protein (CP) supplement to the low-quality diets of sheep in comparison with cottonseed cake (CSC). Changes in the chemical composition of the leaves with progressive maturation (December to March) were studied. The leaves maintained a high CP content (>164?g/kg dry matter (DM)) during the prolonged maturation in the winter feed scarcity period. The leaves were rich in Ca (41?g/kg DM) and K (89?g/kg DM). The rate of degradation and effective degradability of CP were consistently higher (P?0.001) in CSC than in G. oppositifolia. A balance trial in a 4?×?4 Latin square design with four mature Ramghani wethers showed that DM intake, DM and CP digestibility, and N retention did not differ with the substitution of CSC with G. oppositifolia leaves, as a supplement to a basal diet of sorghum hay. Body weight (BW) gain and wool yield responses to the supplements were examined with 36 lambs (27?±?3?kg BW; age 11?±?1?months) for 15?weeks. The lambs were only grazed on local pasture (control group) or supplemented with CSC, G. oppositifolia leaves, and their mixture on iso-N basis. Addition of the supplements increased (P?0.05) BW gain and wool yield, and the leaves were as effective as CSC. These results demonstrated that G. oppositifolia leaves provide good quality green fodder during the prolonged winter feed scarcity period, and that the leaves can be efficiently utilized as a CP supplement to the low-quality diets of sheep. 相似文献
944.
Shoaib Akhtar Gu-cheng LI Raza Ullah Adnan Nazir Muhammad Amjed Iqbal Muhammad Haseeb Raza Nadeem Iqbal Muhammad Faisal 《农业科学学报》2018,17(6):1454-1462
Hybrid maize farmers have to face diverse kinds of climate, biological, price and financial risks. Farmers' risk perceptions and risk attitudes are essential elements influencing farm operations and management decisions. However, this important issue has been overlooked in the contemporary studies and therefore there is a dearth of literature on this important issue. The present research is therefore, an attempt to fill this gap. This study aims to quantify hybrid maize farmers' perceptions of disastrous risks, their attitudes towards risk and to explore the impacts of various farm and farm household factors on farmers' risk attitudes and risk perceptions. The present study is conducted in four hybrid maize growing districts of Punjab Province, Pakistan, using cross-sectional data of 400 hybrid maize farmers. Risk matrix and equally likely certainty equivalent (ELCE) method are used to rank farmers' perceptions of four catastrophic risk sources including climate, biological, price and financial risks and to investigate farmers' risk aversion attitudes, respectively. Furthermore, probit regression is used to analyze the determinants affecting farmers' risk attitudes and risk perceptions. The results of the study showed that majority of farmers are risk averse in nature and perceive price, biological and climate to be potential sources of risks to their farm enterprise. In addition, analysis divulges that distance from farm to main market, off-farm income, location dummies for Sahiwal and Okara, age, maize farming experience, access to extension agent, significantly (either negatively or positively) influence farmers' risk attitudes and risk perceptions. The study delivers valuable insights for farmers, agricultural insurance sector, extension services researchers and agricultural policy makers about the local understanding of risks to hybrid maize crop in developing countries, like Pakistan, and have implications for research on farmers' adaptation to exposed risks. 相似文献
945.
We investigated the floristic composition, phytosociological and regeneration status of Sarkot Van Panchyat (community forest) in Chamoli district of Garhwal Himalaya. A total of 52 plant species of 46 genera and 26 families were recorded, which included 12 trees, 18 shrubs and 22 herb species. Quercus leucotrichophora was dominant tree species in sapling and seedling layers, followed by Lyonia ovalifolia and Rhododendron arboreum.Out of 12 tree species, 7 species in seedling stage and 8 species in sapling stage were recorded in the study area. The 44.41% species in the study area showed good regeneration status, 16.66% species were fairly regenerating,and 8.33% species showed poor regeneration status, while 33% species were not regenerating. Number of individuals from lower girth classes (0 10 cmand 10 30 cm) showed decreasing trend with the increase in size of girth class. Shannon index (H) for trees, shrubs and herbs was recorded as 1.82,2.24 and 2.41 respectively. Simpsons index (CD) was recorded as 0.21, 0.12and 0.12 for trees, shrubs and herbs respectively. The forest should be divided into compartments for better management purpose and each compartment should be closed for five years to assist regeneration and enrichment planting may also be carried out for sustainable management. 相似文献
946.
秸秆覆盖对土壤养分和油菜生长发育的影响 总被引:3,自引:0,他引:3
通过田间试验,研究了不同秸秆(水稻秸秆和玉米秸秆)不同量覆盖条件下耕层土壤有机质、全氮、碱解氮、全磷、有效磷、全钾和速效钾的效应以及旱地油菜株高、花序数和分枝数的差异,并进行了产量分析.结果表明:秸秆覆盖对耕层土壤有机质的积累没有明显作用,总体上全氮随着秸秆覆盖量的增加而增加.同水平玉米秸秆覆盖处理较水稻秸秆覆盖处理对碱解氮的积累作用较明显;秸秆覆盖处理大部分可以提高耕层土壤全钾;不同秸秆对耕层土壤钾素的影响不同,水稻秸秆覆盖处理对土壤有效磷、全钾和速效钾的效果优于玉米秸秆覆盖;速腐剂的使用对有机质、碱解氮积累没有影响,但可以增加土壤全氮、全磷的累积,无作物的情况下速腐剂可以增加耕层土壤全钾的积累.秸秆覆盖对油菜的营养生长和生殖生长有显著促进作用,秸秆覆盖可以显著提高油菜的株高,增加分枝数和花序数;速腐剂的加施对营养生长的效果明显,但对生殖生长的效果未显现出来.秸秆覆盖可以增加油菜产量,同水平秸秆覆盖速腐剂处理的产量最高. 相似文献
947.
Rhizobia isolated from fourteen different genera of legumes were tested for their N-fixing effectiveness with Psophocarpus tetragonolobus in standard Leonard jar trials. Isolates from all plants except Pithecellobium jiringa were able to form nodules with P. tetragonolobus although a wide range of effectiveness amongst the different rhizobia was demonstrated. Thus P. tetragonolobus may be considered promiscuous with respect to its rhizobial requirements. Based on this experiment, a group of rhizobia comprising three elite strains (RRIM 56 from P. tetragonolobus, UMKL 36 from Lablab purpureus and CB 756 from Macrotyloma africanum, a moderately effective strain (NGR 258 from P. tetragonolobus), and two strains of low effectivity (RRIM 968 from Centrosema pubescens and UMKL 12 from Phaselus angularis) were selected for further study. When these were used to inoculate P. tetragonolubus growing in soil taken from virgin jungle (less than 1.54 rhizobia g?1 soil); RRIM 56 and UMKL 36 again performed well, but NGR 258 outperformed CB 756. 相似文献
948.
Ferdaus Mohamat-Yusuff Syaizwan Zahmir Zulkifli Ahmad Ismail Hiroya Harino Mohd Kamil Yusoff Takaomi Arai 《Water, air, and soil pollution》2010,211(1-4):443-457
Thais gradata samples were collected from six locations along the southern shores of Peninsular Malaysia and analyzed for imposex incidence and organotin (butyltins (BTs), including tributyltin, dibutyltin, and monobutyltin, and phenyltins (PTs), including triphenyltin, diphenyltin, and monophenyltin concentrations), in tissue burden. On average, the BT levels were found to be higher than the levels reported a year before for other biota. In contrast, the PT compounds were found to be lower than in the previous report. The present study also classified the morphological expressions of the imposex scheme for this species into seven stages (stage 0 to stage 6) by observing the development of vas deference sequence (VDS) and penis bulk. This latest imposex scheme clearly indicates the mechanism of VDS growth, the structural changes from penis bulk to a penis with flagellum, and from a normal vaginal opening to a swollen vaginal opening. The degree of imposex was assessed using the vas deference sequence index and the percentage of females possessing the imposex characteristics. It was found that locations possessing high imposex levels also tended to show high BT levels in the snail tissue samples. However, correlation analysis did not show a significant relationship among the two parameters. A better result could be obtained if more samples and sampling locations were added in order to prove the hypothesis. The nonsignificant correlation between the shell height and any of the organotin compounds, along with no significant differences between BT levels in female and lower imposex stage samples, suggests that the BT concentration detected was a recent contamination. 相似文献
949.
Ahmad Munib Chand Naila Khan Rifat Ullah Ahmad Nazir Khattak Irfan Naz Shabana 《Tropical animal health and production》2020,52(2):711-715
Tropical Animal Health and Production - The aim of the study was to investigate the influence of dietary supplementation of various levels of milk thistle (MT) on growth performance, oxidative... 相似文献
950.
BACKGROUND: The German cockroach is an important household insect pest mechanically involved in transmission of a variety of diseases to humans. Different classes of insecticides have extensively been used for its control leading to insecticide resistance development. Hence, for an optimal control of this pest, the status and underlying mechanisms of insecticide resistance should be studied in this group of insects. METHODS: Adult German cockroaches were collected from Imam and Bouali Cina Hospitals (Sari, Iran) and subjected to bioassay using jar test method. The results were compared to those of a susceptible laboratory strain. Biochemical assays of esterases, monooxigenases and glutathione S-transferase (GST) levels were undertaken on German cockroaches from Imam and Bouali Cina Hospitals and the results were compared to a susceptible laboratory strain. RESULTS: The LT50 values of the three strains were 20.24+/-2.2, 19.87+/-2.3 and 8.89+/-0.26 for permethrin; 19.3+/-3.05, 17.6+/-0.68 and 8.8+/-0.99 for deltamethrin; 19.64+/-2.9, 18.66+/-3.45 and 8.64+/-0.62 min for cypermethrin, respectively. The mean -esterase activity of Imam and Bouali Cina Hospitals and susceptible strains were 6.941x10(-4), 6.940x10(-4) and 8.01x10(-5) nmol/min/mg protein; the mean -esterase activity in those strains were 5.8x10(-4), 4.25x10(-4) and 7.28x10(-5) nmol/min/mg protein; the mean content of p450 in the above-mentioned strains were 5.64x10(-6), 1.89x10(-6) and 1.2x10(-6) nmol/mg protein; the mean GST activity were 6.66x10(-2), 0.102 and 5.72x10(-2) mol/min/mg protein, respectively. CONCLUSION: The LT50 values and also the mean activity of all enzyme groups in field strains were significantly different from those of the susceptible strain, indicating a vigour tolerance to insecticides and pyrethroids in particular. Hence, insecticide resistance monitoring techniques should be put in place and also resistance management strategies and measures should be considered implementing in the area. 相似文献