全文获取类型
收费全文 | 211711篇 |
免费 | 11172篇 |
国内免费 | 124篇 |
专业分类
林业 | 8544篇 |
农学 | 6420篇 |
基础科学 | 1483篇 |
24355篇 | |
综合类 | 39798篇 |
农作物 | 8119篇 |
水产渔业 | 10146篇 |
畜牧兽医 | 107380篇 |
园艺 | 2603篇 |
植物保护 | 14159篇 |
出版年
2018年 | 2507篇 |
2017年 | 2770篇 |
2016年 | 2637篇 |
2015年 | 2315篇 |
2014年 | 2759篇 |
2013年 | 7950篇 |
2012年 | 5364篇 |
2011年 | 6651篇 |
2010年 | 4294篇 |
2009年 | 4306篇 |
2008年 | 6611篇 |
2007年 | 6182篇 |
2006年 | 5951篇 |
2005年 | 5620篇 |
2004年 | 5568篇 |
2003年 | 5549篇 |
2002年 | 5449篇 |
2001年 | 6535篇 |
2000年 | 6370篇 |
1999年 | 4981篇 |
1998年 | 2115篇 |
1997年 | 2154篇 |
1995年 | 2503篇 |
1994年 | 2331篇 |
1993年 | 2219篇 |
1992年 | 4514篇 |
1991年 | 4807篇 |
1990年 | 4792篇 |
1989年 | 4788篇 |
1988年 | 4385篇 |
1987年 | 4517篇 |
1986年 | 4658篇 |
1985年 | 4464篇 |
1984年 | 3750篇 |
1983年 | 3363篇 |
1982年 | 2312篇 |
1981年 | 2176篇 |
1980年 | 2063篇 |
1979年 | 3371篇 |
1978年 | 2850篇 |
1977年 | 2366篇 |
1976年 | 2213篇 |
1975年 | 2325篇 |
1974年 | 3051篇 |
1973年 | 3130篇 |
1972年 | 3052篇 |
1971年 | 2801篇 |
1970年 | 2635篇 |
1969年 | 2428篇 |
1967年 | 2064篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
991.
Boysen SR Rozanski EA Tidwell AS Holm JL Shaw SP Rush JE 《Journal of the American Veterinary Medical Association》2004,225(8):1198-1204
OBJECTIVE: To establish a focused assessment with sonography for trauma (FAST) protocol in dogs, determine whether FAST can be performed by veterinary clinicians without extensive ultrasonographic experience, and assess the frequency of free fluid (as determined via FAST) in the abdominal cavity of dogs following motor vehicle accidents (MVAs). DESIGN: Prospective study. ANIMALS: 100 client-owned dogs evaluated within 24 hours of an MVA. PROCEDURE: Dogs were placed in lateral recumbency for the FAST examination. To detect fluid in the abdomen, 2 ultrasonographic views (transverse and longitudinal) were obtained at each of 4 sites (just caudal to the xiphoid process, on the midline over the urinary bladder, and at the left and right flank regions). RESULTS: In the 100 dogs evaluated via FAST, free abdominal fluid was detected in 45 dogs. In 40 of those 45 dogs, abdominocentesis was performed; hemoperitoneum and uroperitoneum were diagnosed in 38 and 2 dogs, respectively. Compared with dogs that had no free abdominal fluid detected via FAST, dogs that had free abdominal fluid detected via FAST had significantly higher heart rates and serum lactate concentrations and significantly lower PCVs and total solid concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that FAST is a simple and rapid technique that can be performed on dogs in an emergency setting to detect intra-abdominal free fluid and can be performed by veterinary clinicians with minimal previous ultrasonographic experience. 相似文献
992.
Characterization of BoHV-1 gE envelope glycoprotein mimotopes obtained by phage display 总被引:4,自引:0,他引:4
A phage-displayed peptide library was screened using four mAbs directed against bovine herpesvirus 1 (BoHV-1) gE glycoprotein to identify peptides mimicking this glycoprotein. The selected mimotopes allowed us to characterize the epitopes corresponding to the mAbs as continuous and proteinic and to consider using these peptides in further studies. One epitope has been clearly located at the C-terminus of the protein (amino-acids 561-569). The three other mAbs enabled us to stress the immunogenic relevance of the proline-rich motifs of gE. Selected peptides showed no clear sequence identity with gE, but there is a clear link between gE proline-rich regions and the amino-acid composition of the mimotopes. The proline-rich motifs of gE are potentially located in flanking regions involved in the gE/gl glycoprotein complex formation. N-terminal fusion to pill or pVIII filamentous phage protein, C-terminal fusion to the T7 phage capsid protein, biotinylated synthetic peptides and insertion between the non-cleaved CX leader sequence and the C-terminal part of Caulobacter crescentus RsaA protein have been tested in order to increase the valency of a model peptide. We have diverted the C. crescentus expression system and proven its usefulness using the RsaA protein as a scaffold displaying the peptides of interest. Comparison between these different display systems in an indirect ELISA, indicates that the C. crescentus expression and the T7 phage display systems have some major advantages. 相似文献
993.
Kupper J Waidyasekera D Schönenberger W Demuth D Althaus RF Naegeli H 《DTW. Deutsche tier?rztliche Wochenschrift》2004,111(11):433-438
Poisonings can cause reduced performance and severe economic loss in farm animals. A swift and targeted action is required from veterinarians. We have established a computer-based decision support system for poisonings in ruminants and pigs. The system offers access to the most recent information available in clinical toxicology of farm animals. Towards this goal, relevant reports from the peer-reviewed literature were evaluated and organised according to the requirements of a structured database. The information provided for each toxic substance includes a summary of its chemical and physical properties, sources, commercial uses or natural occurrences, toxicokinetic data, mechanisms of action, threshold doses, clinical symptoms with brief case reports, sampling and analytical results, post-mortem abnormalities, differential diagnoses, therapeutic guidelines and references to the literature. This decision support system has been programmed with two user-friendly search functions: a search tool that allows the choice of clinical and pathological findings, and another function that serves to find a substance using its chemical name, the class of compounds to wich it belongs, a possible source or one of its main applications. CliniTox can be accessed directly via our webserver (http://www.clinitox.ch). 相似文献
994.
A nutritional evaluation of an Irish dairy herd indicated gross overfeeding of late lactation cows, over-conditioning of cows at parturition and a high rate of body condition loss in early lactation. Metabolisable-energy based nutritional modelling software was used to guide recommended dietary changes to prevent excessive condition gain in late lactation. Immediately following the implementation of the changes there was an unexpected reduction in performance affecting both milk yield and protein concentration. An investigation into the poor performance revealed underestimation of peak milk yield; over-estimation of maize silage quality; a large difference in the concentrate being fed compared to the concentrate recommended, and failure of the blend of concentrate ingredients to maintain the intended proportions in the in-parlour feeding system. The estimated maximum cumulative effect of these errors was to cause undersupply of energy and protein in the recommended diet of 16% and 3% respectively to cows in early lactation. Use of a net-energy nutritional model would have indicated a requirement for a higher energy supply in this case. This report highlights the challenges in obtaining accurate on-farm data for use in dairy cow nutritional models. 相似文献
995.
Elliott RC 《Journal of the South African Veterinary Association》2010,81(2):75-79
Cricopharyngeal achalasia is a rare cause of dysphagia in the dog. However it must be differentiated from other causes of dysphagia as it is treatable with surgery. It is a disruption of the cricopharyngeal phase of the oropharyngeal phase of deglutition. There appears to be an incoordination in the swallowing process between the relaxation of the rostral, middle pharyngeal muscles and the caudal pharyngeal muscles. It is seen as a primary condition in young animals presenting soon after weaning onto solid food. The dogs appear clinically healthy unless there is secondary aspiration pneumonia or emaciation. These dogs may present as respiratory emergencies and require intensive support and treatment prior to corrective surgery. The diagnosis is made on videofluoroscopy. The condition carries a good prognosis for cure with surgical myectomy of the cricopharyngeal muscle and the thyropharyngeal muscle, which make up the upper oesophageal sphincter. Temporary relief prior to surgery can be achieved by injection of the cricopharyngeal muscle with botulism toxin. Surgical treatment for dysphagia secondary to an underlying neurological, neuromuscular or pharyngeal weakness carries a guarded prognosis and will make aspiration pneumonia worse. 相似文献
996.
Although androgenic and estrogenic steroids are widely used to enhance muscle growth and increase feed efficiency in feedlot cattle, their mechanism of action is not well understood. Further, in vivo studies indicate that estradiol (E2) affects muscle protein synthesis and/or degradation, but in vitro results are inconsistent. We have examined the effects of E2 treatment on protein synthesis and degradation rates in fused bovine satellite cell (BSC) cultures. Additionally, to learn more about the mechanisms involved in E2-enhanced muscle growth, we have examined the effects of compounds that interfere with binding of E2 or insulin-like growth factor (IGF)-1 to their respective receptors on E2-induced alterations in protein synthesis and degradation rates in BSC cultures. Treatment of fused BSC cultures with E2 results in a concentration-dependent increase (P < 0.05) in protein synthesis rate and a decrease (P < 0.05) in protein degradation rate. The pure estrogen antagonist ICI 182 780 suppresses (P < 0.05) E2-induced alterations in protein synthesis and degradation in fused BSC cultures. The G-protein coupled receptor (GPR)-30 agonist G1 does not affect either synthesis or degradation rate, which establishes that GPR30 does not play a role in E2-induced alterations in protein synthesis or degradation. JB1, a competitive inhibitor of IGF-1 binding to the Type 1 insulin-like growth factor receptor (IGFR-1), suppresses (P < 0.05) E2-induced alterations in protein synthesis and degradation. In summary, our data show that E2 treatment directly alters both protein synthesis and degradation rates in fused BSC cultures via mechanisms involving both the classical estrogen receptor (ER) and IGFR-1. 相似文献
997.
998.
D Vecchio G Neglia R Di Palo A Prandi B Gasparrini A Balestrieri M J. D’Occhio L Zicarelli G Campanile 《Reproduction in domestic animals》2010,45(4):614-618
The aims of this study were to verify the efficacy of delayed hormonal treatments performed on day 25 post‐insemination on pregnancy rate at 45 and 70 days in buffalo. The trial was performed on 385 buffaloes synchronized by the Ovsynch/TAI protocol and submitted to artificial insemination (AI). Twenty‐five days after AI, pregnant animals were assigned to four treatments: (1) GnRH agonist (n = 52), 12 μg of buserelin acetate; (2) hCG (n = 51), 1500 IU of human chorionic gonadotrophin; (3) Progesterone (n = 47), 341 mg of P4 intramuscular (im) every 4 days for three times; (4) Control (n = 54), treatment with physiological saline (0.9% NaCl). Milk samples were collected on days 10, 20 and 25 after AI in all buffaloes to determine progesterone concentration in whey by radioimmunoassay method. Statistical analysis was performed by anova . Pregnancy rate on day 25 after AI was 52.9%, but declined to 41.8% by day 45, indicating an embryonic mortality (EM) of 21%. If only control group is considered, the incidence of EM was 38.9%. Pregnant buffaloes had higher (p < 0.01) progesterone concentrations on day 20 and 25 after AI than both non‐pregnant buffaloes and buffaloes that showed EM. The treatments on day 25 increased (p < 0.01) pregnancy rate, although in buffaloes with a low whey progesterone concentration on day 20 and 25 after AI (n = 22); all treatments were ineffective to reduce EM. 相似文献
999.
A. E. Joetzke K. A. Sterenczak N. Eberle S. Wagner J. T. Soller I. Nolte J. Bullerdiek H. Murua Escobar D. Simon 《Veterinary and comparative oncology》2010,8(2):87-95
Overexpression of high mobility group A (HMGA) genes was described as a prognostic marker in different human malignancies, but its role in canine haematopoietic malignancies was unknown so far. The objective of this study was to analyse HMGA1 and HMGA2 gene expression in lymph nodes of canine lymphoma patients. The expression of HMGA1 and HMGA2 was analysed in lymph node samples of 23 dogs with lymphoma and three control dogs using relative quantitative real‐time RT‐PCR. Relative quantity of HMGA1 was significantly higher in dogs with lymphoma compared with reference samples. HMGA2 expression did not differ between lymphoma and control dogs. With the exception of immunophenotype, comparison of disease parameters did not display any differences in HMGA1 and HMGA2 expression. The present findings indicate a role of HMGA genes in canine lymphoma. This study represents the basis for future veterinary and comparative studies dealing with their diagnostic, prognostic and therapeutic values. 相似文献
1000.
E. Finn L.M. Freeman J.E. Rush Y. Lee 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2010,24(6):1369-1374
Background: Obese people with heart failure have improved survival compared with their normal or underweight counterparts. The purpose of this study was to determine if there is a relationship between body weight or body condition and survival in cats with heart failure. Hypothesis: Body weight and body condition score (BCS) are predictors of survival in cats with heart failure. Animals: One‐hundred and one cats with heart failure (International Small Animal Cardiac Health Council Classes II, IIIa, or IIIb) evaluated between March 2007 and June 2009. Methods: Data regarding initial body weight and BCS, subsequent changes in body weight, and treatment were collected from records and compared with survival times. Results: Median initial body weight was 5.1 kg (range, 2.2–9.5 kg). Median BCS was 5 (range, 3–9). Of the 68 cats that were discharged from the hospital, median body weight change was 0.0 kg (range, ?2.6 to +2.3 kg). Survival time for all 101 cats was 93 days (0–811 days). Survival could be predicted using a model combining initial body weight (P= .02), body weight squared (P= .02), and survival to discharge (P < .001) with a resulting global P value for this model of P < .0001. Conclusions and Clinical Importance: Cats with the lowest and highest body weights had reduced survival times compared with those with body weights in the intermediate ranges, suggesting a U‐shaped relationship between body weight and survival. Additional research into the effects of body composition could help to determine optimal management of cats with heart failure. 相似文献