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71.
Reproductive performance of camels (Camelus dromedarius) under pastoral management and its influence on herd development 总被引:1,自引:0,他引:1
Brigitte A. Kaufmann 《Livestock Production Science》2005,92(1):17-29
Camels (Camelus dromedarius) produce milk and offspring and provide transport in pastoral husbandry systems in the Afro-Asian dryland belt. The aim of the present study was to investigate the reproductive performance of camels kept under pastoral management in northern Kenya. Using the Progeny History surveying technique, data were collected from 471, 287 and 416 adult Rendille, Gabra and Somali female camels including data on 1506, 789 and 1206 parturitions, respectively. Surveys took place from January to December 1995, but data refer to the 15-year production period preceding the survey. Age at first calving (AFC) was 58.4±1.0 months (LSMeans±S.E.), 63.0±1.1 months and 68.4±1.3 months for the Somali, Rendille and Gabra camels, respectively.The mean calving interval was similar for all three populations with 27.3±0.6 months (LSMeans±S.E.) for Rendille camels, 28.0±0.6 months for Gabra (n=500) and 28.4±0.6 months for Somali camels. The annual calving rate varied between 33% and 46% in the Somali, 19% and 44% in the Gabra and 8% and 86% in the Rendille camel population. Calf mortality rate averaged 25%, 22% and 27% in Rendille, Gabra and Somali camel calves, respectively, and showed highest variation between the years in the Rendille system (5% to 60%).The number of adult breeding females increased by about 20% over a simulation period of 10 years using the status quo reproductive parameters and by about 70% with improved AFC and CI (excluding AFC>78 months and CI>36 months). The results reveal the usual and unusual variation in the reproductive parameters over different years and in the different systems. It is concluded that eliminating unusual variation is a promising way to enhance herd development and reduce risk in the production systems. 相似文献
72.
Growth, mycorrhiza and frost resistance of Picea abies seedlings following fertilization with different levels of nitrogen . NPK fertilization with varying levels of nitrogen causes increased growth of spruce seedlings and faster flushing in spring. During the growing season, the frost resistance of all organs of the plants, especially new needles and shoots is the lower, the more nitrogen the plants have received. Consequently, spruce plantations, especially at high altitudes, may be liable to late frost damage. 相似文献
73.
Thierry Koumbi-Mounanga Tony Ung Paul Cooper Brigitte Leblon Kevin Groves 《Wood material science & engineering》2015,10(1):17-26
AbstractThe potential of near infrared spectroscopy (NIRS) to estimate wood moisture content (MC), surface energy characteristics and adhesive bond strength were evaluated on aspen (Populus tremuloides Michx.) veneer subjected to different drying times. For samples dried progressively at 103°C, the best MC prediction model was for the total MC range (0–100%) with an R2 value of 0.68. However, exposure at 180°C produced surface colour changes, and the CIE L*a*b* colour parameters measuring colour changes were better estimated using the 400–900 nm spectral data than the 1100–2400 nm spectral data. Increased exposure time at 180°C resulted in lower wettability and, hence, larger contact angles, especially when ethylene glycol was used as probe solvent. Lap shear strength tests on veneers showed that adhesion by phenol formaldehyde resins was impaired by the high temperature exposure; however, the lap shear strength test had high variability so there was not always a clear relationship between contact angle and lap shear strength test. 相似文献
74.
Imamura K Yasuda M Riwar B Inui S Ekino S 《Comparative immunology, microbiology and infectious diseases》2009,32(5):419-428
We established the method of isolating individually encapsulated germinal centers (GCs) from immunized spleen and analyzed single cell suspension of GCs by flowcytometry. In GCs, the high frequency of sIgG+ cells (29%) and sIgA+ cells (5%) was detected. Two-color flowcytometry analysis showed that GCs contained 27% of sIgM-IgG+ cells, in which isotype switch from IgM to IgG had occurred, and 5% of Bu1-IgG+ cells, which were differentiating into plasma cells. On the other hand, sIgM-IgG+ and Bu1-IgG+ cells were not detected in the bursa, which contained 95% of B cells and only 1% of T cells. CD4+ but not CD8+ T cells were detected in the light zone of GCs and these CD4+ T cells are supposed to play a key role in isotype switching and differentiation into plasma cells in GCs. These results clearly demonstrate that GCs provide a site for isotype switching and differentiation into plasma cells. 相似文献
75.
Martin S. A. Seewald Wolfgang Singer Brigitte A. Knapp Ingrid H. Franke-Whittle Armin Hansel Heribert Insam 《Biology and Fertility of Soils》2010,46(4):371-382
The agronomic effects of composts, mineral fertiliser and combinations thereof on chemical, biological and physiological soil
properties have been studied in an 18-year field experiment. The present study aimed at tracing treatment effects by evaluating
the volatile organic compound (VOC) emission of the differently treated soils: non-amended control, nitrogen fertilisation
and composts (produced from organic waste and sewage sludge, respectively) in combination with nitrogen fertiliser. Microbial
community structure was determined by denaturing gradient gel electrophoresis (DGGE). Aerobic and anaerobic soil VOC emission
was determined after glucose amendment using proton transfer reaction–mass spectrometry (PTR-MS). After inducing VOC production
by substrate (glucose) addition and at the same time reducing oxygen availability to impair degradation of the produced VOCs,
we were able to differentiate among the treatments. Organic waste compost did not alter the VOC emissions compared to the
untreated control, whilst sewage sludge composts and mineral fertilisation showed distinct effects. This differentiation was
supported by DGGE analysis of fungal 18S rDNA fragments and confirms earlier findings on bacterial communities. Three major
conclusions can be drawn: (1) VOC patterns are able to discriminate among soil treatments. (2) Sewage sludge compost and mineral
fertilisation have not only the strongest impact on microbial community composition but also on VOC emission patterns, but
specific tracer VOCs could not be identified. (3) Future efforts should aim at a PTR-MS-linked identification of the detected
masses. 相似文献
76.
Chetboul V Tessier D Borenstein N Delisle F Zilberstein L Payen G Leglaive E Franc B Derumeaux G Pouchelon JL 《Journal of the American Veterinary Medical Association》2003,223(8):1159-62, 1129
A thoracic aortic aneurysm was diagnosed in a 6-month-old male Leonberg dog by use of radiography, transthoracic and transesophageal echocardiography, and magnetic resonance imaging. The aneurysm was associated with a twisted ascending aorta and dilatation of several other thoracic arteries (pulmonary trunk, brachiocephalic trunk, and left subclavian artery). Histologic examination of the aorta revealed cystic medial necrosis, with disruption of the elastic network, collagen fibers, and the muscle glycoprotein fibrillin-1. The dam and sire of the dog and 8 littermates were examined by use of transthoracic echocardiography. The sire and 1 male littermate also had an aneurysm of the ascending aorta. To the authors' knowledge, this is the first report of familial aortic aneurysm in dogs. 相似文献
77.
Landscape pattern in topographically complex landscapes: issues and techniques for analysis 总被引:7,自引:1,他引:6
Ecological research provides ample evidence that topography can exert a significant influence on the processes shaping broad-scale landscape vegetation patterns. Studies that ignore this influence run the risk of misinterpreting observations and making inappropriate recommendations to the management community. Unfortunately, the standard methods for landscape pattern analysis are not designed to include topography as a pattern-shaping factor. In this paper, we present a set of techniques designed to incorporate the topographic mosaic into analyses of landscape pattern and dynamics. This toolbox includes adjustments to classic landscape indices that account for non-uniform landscape topography, indices that capture associations and directionality in vegetation pattern due to topographic structure, and the application of statistical models to describe relationships between topographic characteristics and vegetation pattern. To illustrate these methods, we draw on examples from our own analysis of landscape pattern dynamics in logged and unlogged forest landscapes in southwestern British Columbia. These examples also serve to illustrate the importance of considering topography in both research and management applications.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
78.
79.
80.
Endogenous opioid binding to micro receptors is hypothesized to mediate natural rewards and has been proposed to be the basis of infant attachment behavior. Here, we report that micro-opioid receptor knockout mouse pups emit fewer ultrasonic vocalizations when removed from their mothers but not when exposed to cold or male mice odors. Moreover these knockout pups do not show a preference toward their mothers' cues and do not show ultrasonic calls potentiation after brief maternal exposure. Results from this study may indicate a molecular mechanism for diseases characterized by deficits in attachment behavior, such as autism or reactive attachment disorder. 相似文献