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   147篇
  免费   3篇
  国内免费   1篇
林业   16篇
农学   3篇
  26篇
综合类   40篇
农作物   1篇
水产渔业   4篇
畜牧兽医   56篇
园艺   1篇
植物保护   4篇
  2023年   1篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2018年   3篇
  2017年   1篇
  2014年   4篇
  2013年   6篇
  2012年   8篇
  2011年   6篇
  2010年   5篇
  2009年   4篇
  2008年   3篇
  2007年   6篇
  2006年   9篇
  2005年   9篇
  2004年   14篇
  2003年   8篇
  2002年   2篇
  2001年   2篇
  2000年   4篇
  1999年   2篇
  1998年   3篇
  1997年   2篇
  1994年   1篇
  1993年   3篇
  1992年   2篇
  1991年   3篇
  1990年   1篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1985年   2篇
  1984年   7篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   2篇
  1971年   4篇
  1968年   2篇
  1966年   4篇
排序方式: 共有151条查询结果,搜索用时 281 毫秒
51.
Jupiter's great sodium nebula represents the largest visible structure traversed by the Ulysses spacecraft during its encounter with the planet in February 1992. Ground-based imaging conducted on Mount Haleakala, Hawaii, revealed a nebula that extended to at least +/-300 Jovian radii (spanning approximately 50 million kilometers); it was somewhat smaller in scale and less bright than previously observed. Analysis of observations and results of modeling studies suggest reduced volcanic activity on the moon lo, higher ion temperatures in the plasma torus, lower total plasma content in the torus, and fast neutral atomic clouds along the Ulysses inbound trajectory through the magnetosphere. Far fewer neutrals were encountered by the spacecraft along its postencounter, out-of-ecliptic trajectory.  相似文献   
52.
A statistical correlationl was made between adrenocorticotropin (ACTH) and four elements in rats under control, stress, and stress-recovery conditions. Blood serum zinc showed a strong positive correlation with the rise in ACTH during stress and its decline in stress recovery. Serum calcium, copper, and magnesium demonstrated little correlation with ACTH changes. The strong ACTH-zinc correlation points to an as yet undefined interaction between ACTH and zinc  相似文献   
53.
Capital rationing and tax incentive issues for an aquacultural firm are developed in the context of intensive firm growth (growth from within rather than through acquisition) with a channel catfish enterprise. Beginning firm debt levels and stringently imposed debt limits (which the firm was not permitted to exceed) were found to have prominent effects upon pond construction levels and growth in profitability. Wide fluctuations in interest rate levels had little impact upon growth of the aquacultural enterprise, although higher interest rates significantly reduced profitability. The tax incentive examined also had little effect upon firm growth. The methodology developed and the effect of the capital, debt, interest rate level and tax features analyzed provide insights that may apply wherever capital and credit rationing impacts upon investment decisions by aquacultural firms.  相似文献   
54.
OBJECTIVE: To validate a fat intake questionnaire (FIQ) developed to assess habitual dietary intake while focusing on the assessment of detailed fatty acid intake including total trans unsaturated fatty acids (TUFA). DESIGN: An 88 food item/food group FIQ was developed using a meal pattern technique. Validation was achieved by comparison with dietary intake assessed by a modified diet history (DH) in a cross-over design. Eighty-four individuals supplied adipose tissue biopsies for linoleic acid and total TUFA analysis as an independent validation of the FIQ and DH. SETTING: Medical Centre, Dublin Airport, Republic of Ireland. SUBJECTS: One hundred and five healthy volunteers (43 females and 62 males aged 23-63 years). RESULTS: Significant correlations (P<0.0005) were achieved for intakes of energy (0.78), total fat (0.77), saturated fat (0.77), monounsaturated fat (0.63), polyunsaturated fat (0.73), TUFA (0.67) and linoleic acid (0.71) assessed by the FIQ compared with the DH. Linoleic acid intake assessed by the FIQ and the DH was significantly correlated with adipose tissue concentrations (r=0.58 and 0.49, respectively; P<0.005); however, total TUFA intake was poorly correlated with adipose tissue concentrations (r=0.17 and 0.10 for FIQ and DH, respectively). CONCLUSIONS: The FIQ compared favourably with the DH in assessing habitual diet, in particular fatty acid intake. In addition, the FIQ was successfully validated against the linoleic acid composition of adipose tissue, an independent biomarker of relative fatty acid status. The FIQ could therefore be used as an alternative to the DH as it is a shorter, less labour-intensive method.  相似文献   
55.
Distribution and status of the Sumatran rhinoceros Dicerorhinus sumatrensis in Peninsular Malaysia were studied from 1975 to 1981. We compiled information collected from field surveys, interviews with people living near rhino areas, and the literature. Most potential rhino areas were surveyed on the ground to confirm the presence of animals, estimate numbers, and evaluate the status of the habitat. We confirmed that rhinos presently occur in ten isolated areas scattered throughout the Malay Peninsula. The number of rhinos is estimated at 50 to 75 animals with the Endau-Rompin (20–25), Taman Negara (8–12), and Sungai Dusun (4–6) areas containing the largest contiguous populations. The Sumatran rhino appears threatened with immediate extinction in Peninsular Malaysia. Excessive killing of rhinos because of the high commercial value of their body parts has greatly reduced numbers. Habitat destruction from logging and forest clearance has separated and isolated already small populations. We recommend that conservation efforts for this species in Malaysia be concentrated in the Endau-Rompin region because this population has the best chances for survival.  相似文献   
56.
Neospora caninum infects bovine hosts giving rise to pro-inflammatory immune responses that can result in foetal death or spontaneous abortion, this appears to be mediated by the actions of IFN-γ on cell activation and migration/trafficking. Yet successful vaccination or natural immunity is also strongly correlated with IFN-γ production. We utilised in vitro infection of bovine macrophages to prime naive T-cell responses. Naive T-cells in contact with infected macrophages produce both IFN-γ and IL-17 in a pattern that is dependent on whether the priming macrophage was protected or non-protected. Our results may explain the apparent dual role of IFN-γ during infection if a second major pro-inflammatory cytokine, IL-17, is produced simultaneously.  相似文献   
57.
An extensive field comparison of the gamma interferon (IFN-gamma) assay and the single intradermal tuberculin test for the diagnosis of bovine tuberculosis was conducted in Australia. The specificity of the IFN-gamma assay was determined by testing more than 6000 cattle from tuberculosis-free herds and varied from 96.2% to 98.1%, depending on the cut-off point chosen to define a positive reactor. For the sensitivity trial, cattle from herds being de-populated because of bovine tuberculosis were examined with both assays. The sensitivity of the IFN-gamma assay was shown to be significantly higher than the single intradermal tuberculin test and varied from 76.8% to 93.6% depending on the method of interpretation. A maximum overall sensitivity of 95.2% was obtained by testing with the IFN-gamma and the tuberculin test in parallel. The superior sensitivity of the IFN-gamma assay and the ability to adjust the sensitivity of the system depending on the task involved, will provide the Australian Tuberculosis Eradication Campaign with a valuable additional test to enable it to accomplish its goals.  相似文献   
58.
59.
Visual patterned reflex present during hypothalamically elicited attack   总被引:1,自引:0,他引:1  
A cat from which attack is elicited by electrical stimulation of the hypothalamus lunges more frequently toward a mouse presented to the eye contralateral to the stimulated site than it does to a mouse presented to the ipsilateral eye. This differential effect does not appear to be attributable to a temporary or permanent defect in the ipsilateral eye.  相似文献   
60.
This study evaluated and compared the clinical and histopathological effects of prednisone on acute radiation-induced dermatitis (ARID) in dogs treated with 48 Gray of fractionated irradiation targeted to the skin surface. The study was designed as a double-blind, randomized, placebo-controlled prospective clinical trial. Twenty-two otherwise healthy companion dogs completed the clinical study. Three dogs were excluded from complete histopathological analysis because the owner declined one (one dog) or both (two dogs) biopsies. The study duration for each dog was 36 days from the start of radiation therapy (RT) to the first re-examination post RT. Dogs were treated with either oral prednisone at 0.5 mg kg(-1) or sugar pill, daily. All dogs received 48 Gray of fractionated, standardized RT, beginning 2 weeks after tumour excision. Acute Radiation Morbidity Scores, Cutaneous Toxicity Extent and Severity scores, digital images, and impression cytology were carried out on days 1, 8, 15, 22 and 36. Four-millimetre skin specimens from days 15 (RT-11) and 36 (2 weeks after the last RT dose) were scored by a pathologist and a dermatologist, blind to specimen identity. A one-way analysis of variance for longitudinal data was used to compare scores between groups. Spearman's rho correlation coefficient was used to measure strength of association between clinical and histopathology scores (HPS). There was no significant difference in CUTES, AMS or HPS scores between groups. There was a strong correlation between clinical and HPS scores. Prednisone did not decrease ARID severity clinically or histopathologically.  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