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   515篇
  免费   38篇
林业   36篇
农学   17篇
基础科学   4篇
  162篇
综合类   17篇
农作物   29篇
水产渔业   43篇
畜牧兽医   162篇
园艺   20篇
植物保护   63篇
  2023年   5篇
  2022年   5篇
  2021年   21篇
  2020年   19篇
  2019年   19篇
  2018年   13篇
  2017年   20篇
  2016年   16篇
  2015年   3篇
  2014年   12篇
  2013年   38篇
  2012年   32篇
  2011年   45篇
  2010年   17篇
  2009年   22篇
  2008年   32篇
  2007年   37篇
  2006年   26篇
  2005年   30篇
  2004年   28篇
  2003年   13篇
  2002年   23篇
  2001年   10篇
  2000年   6篇
  1999年   6篇
  1997年   3篇
  1996年   3篇
  1995年   2篇
  1994年   4篇
  1993年   2篇
  1992年   4篇
  1991年   6篇
  1989年   1篇
  1988年   3篇
  1986年   3篇
  1985年   2篇
  1983年   2篇
  1982年   1篇
  1981年   2篇
  1980年   3篇
  1978年   1篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1972年   2篇
  1969年   2篇
  1963年   2篇
  1961年   1篇
排序方式: 共有553条查询结果,搜索用时 15 毫秒
1.
The purpose of this study was to evaluate the clinicopathological aspects of experimental sporotrichosis in cats and compare the sensitivity of cytopathology, histopathology and culture as diagnostic tools in different phases of the infection. Twenty adult, mixed‐breed cats (10 males and 10 females) were inoculated subcutaneously with 106 fungal microorganisms. Clinical examination was performed weekly. Cytopathologic, histopathologic and culture examinations were performed at 15, 30 and 60 days postinoculation. Culture of multiple organs was performed after euthanasia at 30 (10 cats) and 60 (10 cats) days postinoculation. Friedman parametric and nonparametric statistical analysis were applied to the results. The nodular, tumoral and necrotic lesionsprogressed significantly until day 30 postinoculation, and partial spontaneous regression occurred at day 60, particularly in males. An intense inflammatory pyogranulatomous and lymphocytic infiltrate with rare giant cells and sparse fibrosis associated with numerous, pleomorphic, intra‐ and extracellular fungal cells were observed on day 30. These findings gradually decreased by day 60. Despite the inflammatory granuloma associated with feline sporotrichosis, a tendency for dissemination was observed, with fungal isolation in the lymph nodes, spleen and liver at the 30 and 60 days postinoculation. No significant differences were observed between cytopathology, histopathology and fungal culture during the different phases of the disease. Therefore, cytological examination was considered a simple, rapid and inexpensive diagnostic method at all stages of this disease. Funding: Self‐funded.  相似文献   
2.
3.
This study investigated the effects of ascorbic acid and α-tocopherol supplementation on semen quality parameters of equine thawed-frozen semen. Semen was divided in seven different treatments in a final concentration of 100 × 106 sperm/mL by using Gent extender containing no supplements (control) and the following supplements with three different concentrations: α-tocopherol (0.5, 1, and 2 mM) and ascorbic acid (0.45, 0.9, and 1.8 g/L). After thawing, all samples were maintained at 37°C, while analyses were performed at 0, 60, and 120 minutes. Evaluation of viability and acrosome status (using Pisum sativum agglutinin conjugated to fluorescein isothiocyanate and propidium iodide), mitochondrial membrane potential (5,5′,6,6′-tetrachloro-1,1′,3,3′tetraethylbenzimidazolyl carbocyanine iodine [JC-1]), membrane lipid peroxidation (LPO; C11-BODIPY581/591), and stability of the plasmatic membrane (merocyanine 540 and Yo-Pro-1) of each sample was determined by flow cytometry. Relative to the control group, supplementation with α-tocopherol improved (P ≤ .05) postthaw membrane LPO, yet the higher concentrations of ascorbic acid (0.9 and 1.8 g/L, respectively) showed a negative effect on membrane LPO. Neither antioxidant significantly increased (P > .05) the acrosome integrity and mitochondrial membrane potential of frozen-thawed spermatozoa, although supplementation with α-tocopherol and ascorbic acid (0.9 and 1.8 g/L, respectively) had a positive effect on membrane integrity and stability (P ≤ .05). For all semen parameters, the lower concentration of ascorbic acid (0.45 g/L) did not show significant differences (P > .05) compared with the control. In conclusion, α-tocopherol seems to be an efficient antioxidant for reducing the oxidative stress provoked by cryopreservation, decreasing lipid peroxidation on equine spermatozoa.  相似文献   
4.
The proposed technique consists of placing a catheter in the olfactory recess of the lateral ventricle of the brain of a sheep. Twenty adult ewes were used in the study. The olfactory recess is in the frontal region 25 +/- 3 mm below the skin, just caudal to the line joining the supraorbital foramen and approximately 8-10 mm from the median plane. The approach is relatively easy under normal experimental conditions. The wall of the olfactory bulb, however, is fragile, and the animals must not have been injured by Oestrus ovis.  相似文献   
5.
An 8-month-old white feathered, black skinned Moroseta hen was presented for examination because of numerous 2 mm- to 30 mm-diameter irregularly shaped, hard nodules in the skin of the head, wings, back, and abdomen. The nodules were confined to the skin and did not involve subcutaneous tissues. Nodules consisted of dilated feather follicles packed with a caseous tan-to-pale-yellow material admixed with feather remnants. Histologically, affected feather follicles were markedly dilated and filled with laminated keratin debris. Necrosis of the epidermis and perifollicular lymphocyte infiltration was also present. Bacteriologic investigation of internal organs was negative, while secondary bacteria, Proteus spp. and Bacillus spp., were isolated from skin nodules. A concomitant lice infestation of Menopon spp., as well as leg mange caused by Cnemidocoptes spp., were also present. These bacterial isolates and parasites were not related to the disease condition. The condition observed was differentiated from benign feather follicle tumors, and a diagnosis of multiple feather follicle cysts was made. In addition, a breed predisposition was hypothesized.  相似文献   
6.
7.
This study compared the effects of intravaginal and intravenous routes of oxytocin (OT) administration in 46 oestrous‐induced Santa Inês ewes (6‐day treatment with progestin‐releasing intravaginal sponges and a single injection of 200 IU of eCG at the time of sponge removal) that underwent transcervical embryo recovery 6–7 days after oestrous onset and mating. All ewes received 37.5 μg of d‐cloprostenol via latero‐vulvar route, and 1 mg of oestradiol benzoate i.m. 16 hr before and 50 IU of OT 20 min before non‐surgical embryo recovery (NSER), with OT being administered intravenously (n = 21) or intravaginally (n = 21). An overall oestrous response was 95.6% (44/46), and adequate cervical retraction could be accomplished in 78.6% (33/42) of ewes. The percentage of successful NSER procedures was 57% (24/42) or 72.7% (24/33) of animals with sufficient cervical retraction. The duration of NSER procedure averaged 28 min (range: 17–40 min) and ~96% of flushing fluid could be recovered (range: 85%–100%). Out of 18 ewes that could not undergo NSER, 12 (66.6%) presented various anatomical barriers, whilst the other 33.4% did not present these barriers and still could not be traversed. Excluding the ewes with those anatomical features, the overall success rate of NSER was 80% (24/30). The route of OT administration had no effect on NSER efficiency or the ease with which transcervical embryo flushing was performed. Both routes of OT administration can be used for cervical dilation protocol. Discarding ewes with anatomical features precluding cervical penetration is highly recommended to increase the efficacy of NSER in sheep.  相似文献   
8.
The aim of the experiment was to study the relationship between plasma lactate and allantoin accumulation in horses undergoing five exercises differing in intensity and length. Twenty-five adult trotter horses were used (18 males, two castrated, and five females), housed in three training centers. The horses were assigned to five groups: slow trot, over 2000 m (Group 1); slow trot over 1600 m (Group 2); fast trot over 1600 m (Group 3); fast trot over 2000 m (Group 4); fast trot over 2400 m (Group 5). Plasma was obtained from blood sampled at rest, at the end of the bout of exercise and after 15 and 45 minutes from the end of the bout of exercise and analyzed for glucose, lactate, uric acid, free fatty acids (FFA) and allantoin concentrations. Accumulations of plasma lactate and allantoin (mmol/sec) were calculated as difference between end of exercise and rest and between 45 minutes sample and rest, respectively.Ranking the intensity of exercise using the lactate concentrations at the end of exercise, the level of exertion was highest for Group 3 horses and lowest for Group 5 horses (20.9 and 2.8 mmol/l, respectively). At the end of exercise, glucose concentrations were much higher for horses undertaking the more intensive exercise (Groups 3 and 4 compared to Group 2). FFA concentrations were highest at the end of exercise for Groups 2 and 3 and after 15 minutes for Groups 4 and 5. Plasma uric acid and allantoin concentrations peaked 15 and 45 minutes from the end of exercise, respectively, independently of exercise intensity. The relationship between accumulation of plasma allantoin (y, dependent variables) and lactate (x, independent variable) was non-linear: y=0.15−2.61*x+68.3*x2 (r2=0.900; se=0.19). This suggests that allantoin accumulation could be used together with plasma lactate to calibrate the workload to muscle conditions to prevent muscle injury.  相似文献   
9.
10.

Objective

To evaluate the effects of ketamine continuous rate infusions (CRI) at two dose rates on cardiovascular function and serum creatine kinase MB isoenzyme (CK-MB) and troponin I in healthy conscious dogs.

Study design

Experimental, prospective, crossover, randomized, blinded study.

Animals

Eight adult mixed-breed dogs, aged 6 ± 1 years and weighing 19 ± 8.6 kg (mean ± standard deviation).

Methods

Dogs were administered an intravenous bolus of ketamine (0.5 mg kg?1) followed by a ketamine CRI for 12 hours (20 μg kg?1 minute?1; treatment TC20 or 40 μg kg?1 minute?1; treatment TC40). Sedation, heart rate (HR), mean arterial pressure (MAP), electrocardiographic and echocardiographic parameters were evaluated at baseline (T0) and 1 (T1), 2 (T2), 4 (T4), 8 (T8), 12 (T12) and 24 (T24) hours after ketamine infusion started. Serum concentrations of CK-MB and troponin I were measured at baseline and 12, 24 and 48 hours after infusion started.

Results

HR increased over the first 4 hours, significantly at T1 in TC20 and at T4 in TC40 when compared with T0 (p < 0.05). MAP was significantly increased at T2 in TC40 when compared with TC20. Behavioral changes, such as stereotypical head movements and twitches, occurred within 4 hours in TC40. There were no significant changes in echocardiographic examinations in any dog when compared with baseline. There were no temporal changes in serum CK-MB activity either within or between treatments (p > 0.05). No troponin I was detected in any sample.

Conclusions and clinical relevance

No indication of myocardial injury resulting from ketamine infusion was detected in this study in healthy dogs. Further studies are needed to assess the ketamine infusion effects on antinociception and other organ function not evaluated in the present study.  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