全文获取类型
收费全文 | 5279篇 |
免费 | 238篇 |
国内免费 | 4篇 |
专业分类
林业 | 435篇 |
农学 | 685篇 |
基础科学 | 107篇 |
1271篇 | |
综合类 | 198篇 |
农作物 | 437篇 |
水产渔业 | 350篇 |
畜牧兽医 | 1431篇 |
园艺 | 153篇 |
植物保护 | 454篇 |
出版年
2023年 | 44篇 |
2022年 | 94篇 |
2021年 | 115篇 |
2020年 | 164篇 |
2019年 | 188篇 |
2018年 | 229篇 |
2017年 | 245篇 |
2016年 | 200篇 |
2015年 | 152篇 |
2014年 | 192篇 |
2013年 | 472篇 |
2012年 | 270篇 |
2011年 | 283篇 |
2010年 | 233篇 |
2009年 | 193篇 |
2008年 | 197篇 |
2007年 | 213篇 |
2006年 | 208篇 |
2005年 | 157篇 |
2004年 | 109篇 |
2003年 | 112篇 |
2002年 | 98篇 |
2001年 | 90篇 |
2000年 | 84篇 |
1999年 | 75篇 |
1998年 | 57篇 |
1997年 | 53篇 |
1996年 | 42篇 |
1995年 | 40篇 |
1994年 | 36篇 |
1993年 | 35篇 |
1992年 | 40篇 |
1991年 | 51篇 |
1990年 | 44篇 |
1989年 | 47篇 |
1988年 | 56篇 |
1987年 | 44篇 |
1986年 | 35篇 |
1985年 | 29篇 |
1984年 | 32篇 |
1983年 | 31篇 |
1982年 | 26篇 |
1981年 | 27篇 |
1980年 | 38篇 |
1979年 | 48篇 |
1978年 | 24篇 |
1971年 | 24篇 |
1970年 | 38篇 |
1969年 | 28篇 |
1968年 | 26篇 |
排序方式: 共有5521条查询结果,搜索用时 31 毫秒
101.
Dynamics of salmonella infection in fryer roaster turkeys 总被引:2,自引:0,他引:2
102.
A study was conducted to examine the effect of nutritional stress on the development of the thymus, bursa, and pancreas of 7-to-14-day-old commercial meat-type chickens. One group of 7-day-old chickens was given access to food for only 30 minutes daily for 7 days. The birds were necropsied, and the thymus, pancreas, and bursa were compared with those of the control chickens fed ad libitum and necropsied at 7 and 14 days of age. The thymuses from birds on the restricted diet were atrophied (0.45 +/- 0.08 g) and congested compared with the thymuses from chickens fed ad libitum (1.32 +/- 0.31 g). The bursae from chickens on a restricted diet were also smaller (0.26 +/- 0.08 g) than the bursae from birds with free access to food (0.74 +/- 0.11 g). The restricted diet did not appear to cause any gross or histological pancreatic changes. The thymic lesions produced by nutritional stress were similar to those observed in the runting/stunting syndrome. 相似文献
103.
TREATMENT OF DIAPHRAGMATIC HERNIA IN BUFFALOES 总被引:2,自引:0,他引:2
J. Singh B. Prasad R. Kumar R. N. Kohli S. S. Rathor 《Australian veterinary journal》1977,53(10):473-475
The surgical treatment of diaphragmatic hernia attempted on 19 lactating buffaloes is described. Thirteen cases recovered uneventfully, 1 recovered after developing brisket oedema and 5 died, 3 during surgery and 2 postoperatively. The desired depth of anaesthesia was achieved by the administration of 6% chloral hydrate followed by 5% thiopentone sodium. A postxiphoid approach and the use of a continuous lock stitch suture were preferred to repair the vent in the diaphragm. Pre- and post-operative use of hydrocortisones and fluids and sufficient tissue oxygenation by controlled positive pressure respiration are believed to be keys to the success of the treatment adopted. 相似文献
104.
Anu Rastogi Brij Kishore Mishra Munna Singh Ritu Mishra 《Archives of Agronomy and Soil Science》2013,59(10):1389-1409
The adequate growth of plants can be achieved only by a balanced ratio of biologically active nutrients in soil along with its readily availability. Linseed seems to be an advantageous secondary oilseed crop widely used in industrial purposes, which can serve additional purpose of phytoextraction of heavily infested soils with heavy metals. In this study, we have made an effort to find out the optimum dose of heavy metals necessary as micronutrients like copper (Cu), iron (Fe) and zinc (Zn) for the enhancement of linseed yield along with the distribution of heavy metals in different plant parts. Quantitative enhancement in different traits of linseed plant due to Cu, Fe and Zn fertilization especially for capsules per plant after maturity suggested positive association between heavy metal supply and morphological traits, which indirectly enhanced seed yield. There was a positive correlation between Zn supply and seed yield. In the treatments with Cu and Fe fertilization, seed yield was positively correlated to plant height, capsules per plant and seeds per five capsules. According to this study, it is concluded that linseed has the ability to accumulate majorly Fe followed by Cu and Zn. 相似文献
105.
Maneesh Kumar S. K Singh J. S Bohra 《Communications in Soil Science and Plant Analysis》2020,51(5):658-674
ABSTRACTField experiments were conducted for 2 years in sandy loam soil, to study the direct effect of organic manures i.e. sewage sludge (SS), vermicompost (VC) and sesbania (SB) and chemical fertilizers on rice (Oryza sativa) and their residual effect on wheat (Triticum aestivum) grown in sequence in winter (Rabi) and summer (Kharif) season during 2015–2016 to 2016–2017 at Varanasi, Uttar Pradesh. Residual effect of organic sources of nutrients as SS, VC and SB were monitored up to fourth crop (II wheat) in sequence applied in conjunction with 75% recommended dose of fertilize (RDF). Among the nutrient sources, the maximum grain yield in I rice (4.89 t ha?1), II rice (4.95 t ha?1), was recorded in treatment T3 (100% RDF with S, Zn, B) whereas in I wheat (4.68 t ha?1) and II wheat (4.59 t ha?1), it was recorded in T4 (customized fertilizer). The maximum straw yield during all four crops was recorded in T3 (100% RDF with S, Zn, B) in rice and T4 (customized fertilizer) in wheat crop, which showed 25, 32, 23 and 28% increase over 100% RDF (T2). Application of 100% RDF along with S, Zn, B and customized fertilizer increased the total uptake of N, P, K, S and B and also in net returns and B:C ratio followed by organic treatments. 相似文献
106.
D. Sharifi J. Singh P.K. Peshin A.P. Singh 《Veterinary anaesthesia and analgesia》1991,18(Z1):309-314
Cardio pulmonary embarrassment was induced with thiopentone sodium in 35 healthy adult donkeys divided in to seven groups of five animals. “To effect” anaesthetic dose was (12.72 ± 0.69 mg/kg) which caused transient hypotension, tachycardia and hypoxemia. A stable fall in MAP 1. 6.77 ± 0.287 Kpa (50.78 ± 2.15 mmHg) and a flat EEG were considered to indicate acute circulatory insufficiency due to thiopentone overdose. 相似文献
107.
Vishal Singh Ashish TewariSatya P.S. Kushwaha Vinay K. Dadhwal 《Forest Ecology and Management》2011,261(11):1945-1949
Biomass and carbon sequestration rate of a young (four year old) mixed plantation of Dalbergia sissoo Roxb., Acacia catechu Willd., and Albizia lebbeck Benth. growing in Terai region (a level area of superabundant water) of central Himalaya was estimated. The plantation is seed sown in the rainy season of year 2004 and spread over an area of 44 ha. Allometric equations for both above and below ground components were developed for three tree species. The density of trees in the plantation was 1322 trees ha−1 The diameters of trees were below 10 cm. Five diameter classes were defined for D. sissoo and A. catechu and 3 for A. lebbeck. 5 trees were harvested in each diameter class. Individual tree allometry was exercised for developing the allometric equations relating tree component (low and above ground) biomass to d.b.h. Post analysis equations were highly significant (P > 0.001) for each component of all species. In the plantation Holoptelia integrifolia Roxb. (Family Ulmaceae) has been reduced to shrub form because of frost. Only the aboveground biomass of H. integrifolia and other shrubs were estimated by destructive harvesting method. Herbaceous forest floor biomass and leaf litter fall were also estimated. The total forest vegetation biomass was 10.86 Mg ha−1 in 2008 which increased to 19.49 Mg ha−1 in 2009. The forest is sequestering carbon at the rate of 4.32 Mg ha−1 yr−1. 相似文献
108.
Kumar Chavlesh Singh Sanjay Kumar Verma Mahendra Kumar Pramanick Kallol Kumar Srivastav Manish Kaur Sukhdeep Kumar Rajeev Ranjan 《Genetic Resources and Crop Evolution》2022,69(2):645-659
Genetic Resources and Crop Evolution - The wild Malus germplasm is considered as a gene reservoir for various biotic and abiotic stresses tolerance/resistance genes, including important novel... 相似文献
109.
- 1. Three classes of habitat used by groups of fish species classified as conservation and management priorities were developed for the Gerua River (also known as the Girwa River, Karnali River) in the Ganges river basin. This river is large (mean annual discharge ca 1500 m3 s?1, up to 900 m wide), surrounded by protected lands of India and Nepal, and upstream of major diversions and river alterations.
- 2. Fish and habitat sampling was conducted at 45 sites from 2000 to 2003. Data were analysed for 2172 fish of 14 species. Species and life stages found occupying a statistically distinct subset of the river habitats were grouped to identify classes of river habitat for conservation.
- 3. Most species and life‐stage groups specialized on specific habitat conditions revealed by multivariate analyses of variance and a principal component analysis. The most numerous and diverse group (six species, 15 life stages) was associated with deep depositional habitats with sandy substrate. Two species covering three life stages were primarily oriented to erosional habitat marked by fast current velocity with pebble and cobble substrate. A third group of three species of adults and juveniles were intermediate in habitat use.
- 4. River conservation for fish faunas should maintain both erosional and depositional channel habitats with depths, substrates, and current velocity inclusive of the ranges reported. The erosional and depositional nature of the key habitats requires that rivers be maintained with flows capable of channel‐forming functions.
110.
Datta Apurba Kumar Haider Mohammed Ziaul Ghosh Sumon Kumar 《Tropical animal health and production》2019,51(1):55-64
Tropical Animal Health and Production - A study was conducted to analyze the dairy farming sector of Bangladesh from an economic viewpoint. Primary data was collected from smallholder dairy farms... 相似文献