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排序方式: 共有193条查询结果,搜索用时 15 毫秒
51.
Lamming DW Latorre-Esteves M Medvedik O Wong SN Tsang FA Wang C Lin SJ Sinclair DA 《Science (New York, N.Y.)》2005,309(5742):1861-1864
Calorie restriction (CR) extends the life span of numerous species, from yeast to rodents. Yeast Sir2 is a nicotinamide adenine dinucleotide (NAD+-dependent histone deacetylase that has been proposed to mediate the effects of CR. However, this hypothesis has been challenged by the observation that CR can extend yeast life span in the absence of Sir2. Here, we show that Sir2-independent life-span extension is mediated by Hst2, a Sir2 homolog that promotes the stability of repetitive ribosomal DNA, the same mechanism by which Sir2 extends life span. These findings demonstrate that the maintenance of DNA stability is critical for yeast life-span extension by CR and suggest that, in higher organisms, multiple members of the Sir2 family may regulate life span in response to diet. 相似文献
52.
Myron J. Mitchell Dudley J. Raynal Charles T. Driscoll 《Water, air, and soil pollution》1996,88(3-4):355-369
Information on atmospheric inputs, water chemistry and hydrology were combined to evaluate elemental mass balances and assess temporal changes in elemental transport from 1983 through 1992 for the Arbutus Lake watershed. This watershed is located within a northern hardwood ecosystem at the Huntington Forest within the central Adirondack Mountains of New York (USA). Changes in water chemistry, including increasing NO3 ? concentrations (1.1 μmol c , L?1 yr-1), have been detected during this study period. Starting in 1991 hydrological flow has been measured from Arbutus Lake and these measurements were compared with predicted flow using the BROOK2 hydrological simulation model. The model adequately (r2=0.79) simulated flow from this catchment and was used to estimate drainage for earlier periods when direct hydrological measurements were not available. Modeled drainage water losses coupled with estimates of wet and dry atmospheric deposition were used to calculate solute budgets. Export of SO4 2? (831 mol c ha?1 yr?1) from the greater Arbutus Lake watershed exceeded estimates of atmospheric deposition in an adjacent hardwood stand suggesting an additional source of S. These large drainage losses of SO4 2? also contributed to the drainage fluxes of basic cations (Ca2+, Mg2+, K+ and Na+). Most of the atmospheric inputs of inorganic N were retained (average of 74% of wet precipitation and 85% total deposition) in the watershed. There were differences among years (56 to 228 mol ha?1 yr?1) in drainage water losses of N with greatest losses occurring during a warm, wet period (1989–1991). 相似文献
53.
Contact time, Tc, was varied from 0.5 to 4 ms in a 13C CPMAS NMR study of samples of four organic soils differing only in copper content and degree of decomposition. Initial polarization was rapid, with maximum intensity reached at or before 0.5 ms contact time and a large decrease in intensity by 4 ms contact time. The distribution of intensity was determined by dividing the spectra into four regions, corresponding approximately to aliphatic, carbohydrate, aromatic and carboxyl carbons. Three samples, with up to 1150 p.p.m. Cu, showed small increases in aromaticity with increasing Tc, with the greatest effect between 0.5 and 1 ms, and fairly constant intensity distributions between 1 and 4 ms. The sample with 2920 p.p.m. Cu showed much greater increase in aromaticity with increasing Tc and a decrease in the 50–110 p.p.m. region, which is dominated by carbohydrate signals. T1?H was negatively correlated with increasing Cu content for all four regions of the spectra, but the effect was much larger and the correlation coefficient much higher for the carbohydrate region. A Tc of 1 ms appears suitable for organic soil samples; however, caution must be exercised in drawing conclusions from intensity data, especially where samples contain high concentrations of metals. These data also indicate a possible preferential localization of Cu in the carbohydrate or hydrophilic portions of the organic matter; 13C CPMAS NMR may provide a novel, non-perturbing method to study metal binding in organic soils. 相似文献
54.
Anyanga Milton O. Farman Dudley I. Ssemakula Gorrettie N. Mwanga Robert O. M. Stevenson Philip C. 《Journal of pest science》2021,94(3):783-794
Journal of Pest Science - Sweetpotato weevil (SPW) pest management is challenging because the pest target is sub-terranean, so the application of pesticides is impractical and usually ineffective.... 相似文献
55.
Jacqueline A. Johnson BVM&S MS Sanghita Bhattacharya PhD Vijay Goel PhD Matthew J. Allen Vet MB PhD 《Veterinary surgery : VS》2011,40(6):720-727
Objective: To define the kinematic motion patterns of the canine cervical spine, with a particular emphasis on identifying differences between the cranial (C2–C4) and caudal (C5–C7) segments, and to determine the significance of coupled motions (CM) in the canine cervical spine. Study Design: Cadaveric biomechanical study. Sample Population: Cervical spines of 8 Foxhounds. Methods: Spinal specimens were considered free of pathology based on radiographic, computed tomography, and magnetic resonance imaging examinations. All musculature was removed without damaging ligaments or joint capsules. Spines were mounted in a customized pure‐moment spine testing jig, and data were collected using an optoelectronic motion capture system. Range of motion, neutral zone and CM in flexion/extension, left/right lateral bending and left/right axial rotation were established. Data were analyzed using mixed‐effects maximum likelihood regression models. Results: Total flexion/extension did not change across the 4 levels. There was no difference between flexion and extension, and no CM was identified. Lateral bending was not different across levels, but tended to be greater in the cranial spine. Axial rotation was ~2.6 times greater in the caudal segments. Lateral bending and axial rotation were coupled. Conclusions: Kinematics of the cranial and caudal cervical spine differed markedly with greater mobility in the caudal cervical spine. 相似文献
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58.
Henry CJ Downing S Rosenthal RC Klein MK Meleo K Villamil JA Fineman LS McCaw DL Higginbotham ML McMichael J 《American journal of veterinary research》2007,68(11):1246-1251
OBJECTIVE: To evaluate safety and efficacy of LDI-100, a preparation containing human chorionic gonadotropin (hCG) and bacillus Calmette-Guerin (BCG), in the treatment of dogs with mast cell tumors and to compare results with those from a control group receiving single-agent vinblastine. ANIMALS: 95 dogs with measurable grade II or III mast cell tumors. PROCEDURES: Dogs were randomized to receive either LDI-100 (1.35 ng of BCG and 2 units of hCG, SC, q 24 h) or vinblastine (2 mg/m(2), IV, q 1 wk) for 6 weeks. Tumors were measured at baseline and day 42, and dogs were monitored for signs of toxicosis. Clinical performance scores were recorded at each visit. Differences in host factors (sex, weight, and age), clinical performance score, tumor response, and adverse events were analyzed. RESULTS: 46 dogs received LDI-100, and 49 dogs received vinblastine. No significant differences were found between the 2 treatment groups with regard to host factors or clinical performance score. Tumor response (>or=50% reduction) rates were similar between the LDI-100 and vinblastine group (28.6% and 11.7%, respectively). Dogs in the LDI-100 group had significantly less neutropenia than the vinblastine group. CONCLUSIONS AND CLINICAL RELEVANCE: hCG and BCG have immunomodulatory and antitumor effects against a variety of malignancies in humans and dogs. In this study, LDI-100 provided clinical responses comparable to single-agent vinblastine chemotherapy but without myelosuppression. LDI-100 is a promising new agent that should be further investigated for multimodality therapy of mast cell tumors in dogs. 相似文献
59.
RADIOGRAPHIC PROTOCOL AND NORMAL ANATOMY OF THE HIND FEET IN THE WHITE RHINOCEROS (CERATOTHERIUM SIMUM)
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Robert J. Dudley Simon P. Wood John R. Hutchinson Renate Weller 《Veterinary radiology & ultrasound》2015,56(2):124-132
Foot pathology is a common and important health concern in captive rhinoceroses worldwide, but osteopathologies are rarely diagnosed, partly because of a lack of radiographic protocols. Here, we aimed to develop the first radiographic protocol for rhinoceros feet and describe the radiographic anatomy of the white rhinoceros (Ceratotherium simum) hind foot (pes). Computed tomographic images were obtained of nine cadaver pedes from seven different white rhinoceroses and assessed for pathology. A single foot deemed free of pathology was radiographed using a range of different projections and exposures to determine the best protocol. 3D models were produced from the CT images and were displayed with the real radiographs to describe the normal radiographic anatomy of the white rhinoceros pes. An optimal radiographic projection was determined for each bone in the rhinoceros pes focusing on highlighting areas where pathology has been previously described. The projections deemed to be most useful were D60Pr‐PlDiO (digit III), D45Pr45M‐PlDiLO (digit II), and D40Pr35L‐PlDiLO (digit IV). The primary beam was centered 5–7 cm proximal to the cuticle on the digit of interest. Articular surfaces, ridges, grooves, tubercles, processes and fossae were identified. The radiographic protocol we have developed along with the normal radiographic anatomy we have described will allow for more accessible and effective diagnosis of white rhinoceros foot osteopathologies. 相似文献
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