首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   365篇
  免费   34篇
林业   18篇
农学   6篇
基础科学   2篇
  40篇
综合类   28篇
农作物   20篇
水产渔业   36篇
畜牧兽医   223篇
园艺   6篇
植物保护   20篇
  2023年   2篇
  2022年   7篇
  2021年   9篇
  2020年   12篇
  2019年   14篇
  2018年   13篇
  2017年   15篇
  2016年   13篇
  2015年   10篇
  2014年   11篇
  2013年   19篇
  2012年   23篇
  2011年   21篇
  2010年   14篇
  2009年   17篇
  2008年   13篇
  2007年   24篇
  2006年   20篇
  2005年   9篇
  2004年   12篇
  2003年   12篇
  2002年   7篇
  2001年   7篇
  2000年   3篇
  1999年   4篇
  1998年   4篇
  1996年   4篇
  1995年   2篇
  1994年   2篇
  1991年   2篇
  1990年   3篇
  1989年   2篇
  1988年   6篇
  1987年   2篇
  1985年   4篇
  1984年   3篇
  1982年   3篇
  1981年   2篇
  1979年   2篇
  1978年   4篇
  1977年   2篇
  1976年   3篇
  1975年   2篇
  1974年   3篇
  1973年   6篇
  1972年   2篇
  1971年   9篇
  1969年   3篇
  1967年   3篇
  1958年   3篇
排序方式: 共有399条查询结果,搜索用时 31 毫秒
381.
After 5 years of development, the European College of Veterinary Clinical Pathology (ECVCP) was formally recognized and approved on July 4, 2007 by the European Board of Veterinary Specialisation (EBVS), the European regulatory body that oversees specialization in veterinary medicine and which has approved 23 colleges. The objectives, committees, basis for membership, constitution, bylaws, information brochure and certifying examination of the ECVCP have remained unchanged during this time except as directed by EBVS. The ECVCP declared full functionality based on the following criteria: 1) a critical mass of 65 members: 15 original diplomates approved by the EBVS to establish the ECVCP, 37 de facto diplomates, 7 diplomates certified by examination, and 5 elected honorary members; 2) the development and certification of training programs, laboratories, and qualified supervisors for residents; currently there are 18 resident training programs in Europe; 3) administration of 3 annual board-certifying examinations thus far, with an overall pass rate of 70%; 4) European consensus criteria for assessing the continuing education of specialists every 5 years; 5) organization of 8 annual scientific congresses and a joint journal (with the American Society for Veterinary Clinical Pathology) for communication of scientific research and information; the College also maintains a website, a joint listserv, and a newsletter; 6) collaboration in training and continuing education with relevant colleges in medicine and pathology; 7) development and strict adherence to a constitution and bylaws compliant with the EBVS; and 8) demonstration of compelling rationale, supporting data, and the support of members and other colleges for independence as a specialty college. Formal EBVS recognition of ECVCP as the regulatory body for the science and practice of veterinary clinical pathology in Europe will facilitate growth and development of the discipline and compliance of academic, commercial diagnostic, and industry laboratories in veterinary clinical pathology. Future needs are in developing sponsorship for resident positions, increasing employment opportunities, increasing compliance with laboratory, training, and continuing education standards, and advancing relevant science and technology.  相似文献   
382.
This is the first report of feline solitary plasmacytoma of bone. We describe the clinical, clinico-pathological, radiographic and pathological findings of two successfully treated cats with long-term follow-up. The first case presented with spinal pain and neurological deficits. Radiographs demonstrated sclerosis of lumbar vertebra L6 and a myelogram confirmed interference to flow of contrast in the L4-7 region. A biopsy of L6 revealed neoplastic plasma cell infiltration. There was no evidence of paraproteinaemia on serum protein electrophoresis. The cat underwent hypofractionated megavoltage radiotherapy. Clinical signs resolved completely and 4 years after diagnosis the cat remains well and has no electrophoretically detectable paraproteinaemia. The second case presented with neurological deficits of the tail and spinal radiographs revealed extensive osteolysis of the sacrum. A biopsy of sacral bone demonstrated neoplastic plasma cell infiltration. The animal was normoglobulinaemic. The cat improved clinically with induction chemotherapy (melphalan and methylprednisolone). The same chemotherapeutics were continued at maintenance doses for 4.3 years, at which time there was recurrence of neurological deficits and a palpable sacral mass. Cytological examination of a fine needle aspirate confirmed recurrence of plasma cell neoplasia. A low concentration monoclonal paraproteinaemia was detected. Vincristine was administered resulting in resolution of neurological deficits and a palpably smaller sacral mass. Eighteen months into vincristine therapy, there was recurrence of clinical signs and the cat was euthanased, more than 6 years after the initial diagnosis.  相似文献   
383.
Gamma scintigraphy is a well established imaging modality, which in equine practice is predominantly used in the investigation of lameness and suspected musculoskeletal problems. Whilst there is a growing literature on the indications for scintigraphy in the horse, there has been little emphasis so far on identifying the validity of scintigraphy as a diagnostic test. In particular, to what extent can the results of a scintigraphic examination be trusted? In this opinionated review the current indications for skeletal scintigraphy in the horse are considered and its validity as a diagnostic test reviewed. It is concluded that in the majority of published studies, inherent biases in study design make it difficult to assess accurately the validity of skeletal scintigraphy in the horse. Further well designed, prospective studies are required to assess the validity of skeletal scintigraphy as a diagnostic tool, particularly in horses with subtle alterations in radiopharmaceutical uptake.  相似文献   
384.
385.
386.
Tyrosine hydroxylase (TH) which catalyses the rate – limiting step in catecholamine (CA) synthesis shows significant annual variations with activity and kinetics increasing with the progress of gonad recrudescence up to spawning and decreasing thereafter. Estradiol-17 β (E2) exerts biphasic effects on in vivo and in vitro enzyme activity and kinetics: low dosages/concentrations stimulated, and high dosages/concentrations inhibited them. Preincubations of hypothalamic enzyme preparations with low (10?9 M) or high (10?3 M) E2 for 15 min at 30 °C, followed by cAMP (1.0 mM) for 10 min at 30 °C produced differential effects: an additive effect in the low concentration group and an inhibitory response in the high concentration group. The stimulatory or inhibitory effects on TH activity could be related to changes in apparent Km and Vmax of the enzyme for substrate and cofactor. The results suggest that TH activity and kinetics are influenced by the circulating titer of E2 and the steroid interacts with the cAMP signaling pathway in the acute regulation of TH.  相似文献   
387.
One mouse click on fish seminal vesicle (SV) in Pub-Med reveals a limited number of articles that give various pieces of information on its restricted distribution, origin, structure, relation with testis, and physiology. Although in the last decade significant progress has been made with respect to the nature and multiple functions of SV secretions, and new aspects are steadily being uncovered, much still remains to be known before we can realize its potential application in fisheries. This review is an attempt to provide an update on recent research on various aspects of the SV and its secretory products in teleosts. The available data suggest a significant role of SV and its products in the maturation and nutrition of sperm cells, in the maintenance of their integrity and viability, and the enhancement of spawning performance and fertilization.  相似文献   
388.
The pharmacokinetics of dantrolene and its active metabolite, 5‐hydroxydantrolene, after a single oral dose of either 5 or 10 mg/kg of dantrolene was determined. The effects of exposure to dantrolene and 5‐hydroxydantrolene on activated whole‐blood gene expression of the cytokines interleukin‐2 (IL‐2) and interferon‐γ (IFN‐γ) were also investigated. When dantrolene was administered at a 5 mg/kg dose, peak plasma concentration (Cmax) was 0.43 μg/mL, terminal half‐life (t1/2) was 1.26 h, and area under the time–concentration curve (AUC) was 3.87 μg·h/mL. For the 10 mg/kg dose, Cmax was 0.65 μg/mL, t1/2 was 1.21 h, and AUC was 5.94 μg·h/mL. For all calculated parameters, however, there were large standard deviations and wide ranges noted between and within individual dogs: t1/2, for example, ranged from 0.43 to 6.93 h, Cmax ratios ranged from 1.05 to 3.39, and relative bioavailability (rF) values ranged from 0.02 to 1.56. While activated whole‐blood expression of IL‐2 and IFN‐γ as measured by qRT‐PCR was markedly suppressed following exposure to very high concentrations (30 and 50 μg/mL, respectively) of both dantrolene and 5‐hydroxydantrolene, biologically and therapeutically relevant suppression of cytokine expression did not occur at the much lower drug concentrations achieved with oral dantrolene dosing.  相似文献   
389.
390.
Spatial patterns of soil δ13C were quantified in a subtropical C3 woodland in the Rio Grande Plains of southern Texas, USA that developed during the past 100 yrs on a lowland site that was once C4 grassland. A 50 × 30 m plot and two transects were established, and soil cores (0–15 cm, n = 207) were collected, spatially referenced, and analyzed for δ13C, soil organic carbon (SOC), and soil particle size distribution. Cross-variogram analysis indicated that SOC remaining from the past C4 grassland community co-varied with soil texture over a distance of 23.7 m. In contrast, newer SOC derived from C3 woody plants was spatially correlated with root biomass within a range of 7.1 m. Although mesquite trees initiate grassland-to-woodland succession and create well-defined islands of soil modification in adjoining upland areas at this site, direct gradient and proximity analyses accounting for the number, size, and distance of mesquite plants in the vicinity of soil sample points failed to reveal any relationship between mesquite tree abundance and soil properties. Variogram analysis further indicated soil δ13C, texture and organic carbon content were spatially autocorrelated over distances (ranges = 15.6, 16.2 and 18.7 m, respectively) far greater than that of individual tree canopy diameters in these lowland communities. Cross-variogram analysis also revealed that δ13C – SOC and δ13C-texture relationships were spatially structured at distances much greater than that of mesquite canopies (range = 17.6 and 16.5 m, respectively). These results suggest fundamental differences in the functional nature and consequences of shrub encroachment between upland and lowland landscapes and challenge us to identify the earth system processes and ecosystem structures that are driving carbon cycling at these contrasting scales. Improvements in our understanding how controls over soil carbon cycling change with spatial scale will enhance our ability to design vegetation and soil sampling schemes; and to more effectively use soil δ13C as a tool to infer vegetation and soil organic carbon dynamics in ecosystems where C3–C4 transitions and changes in structure and function are occurring.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号