全文获取类型
收费全文 | 99179篇 |
免费 | 5950篇 |
国内免费 | 2424篇 |
专业分类
林业 | 5490篇 |
农学 | 5133篇 |
基础科学 | 1879篇 |
12676篇 | |
综合类 | 21164篇 |
农作物 | 4196篇 |
水产渔业 | 4479篇 |
畜牧兽医 | 44637篇 |
园艺 | 1709篇 |
植物保护 | 6190篇 |
出版年
2022年 | 805篇 |
2021年 | 1314篇 |
2020年 | 1359篇 |
2019年 | 1564篇 |
2018年 | 1702篇 |
2017年 | 1989篇 |
2016年 | 1875篇 |
2015年 | 1984篇 |
2014年 | 2134篇 |
2013年 | 3739篇 |
2012年 | 3861篇 |
2011年 | 4583篇 |
2010年 | 3319篇 |
2009年 | 3155篇 |
2008年 | 4072篇 |
2007年 | 3924篇 |
2006年 | 3654篇 |
2005年 | 3470篇 |
2004年 | 2791篇 |
2003年 | 2730篇 |
2002年 | 2482篇 |
2001年 | 2799篇 |
2000年 | 2928篇 |
1999年 | 2501篇 |
1998年 | 1313篇 |
1997年 | 1156篇 |
1996年 | 1017篇 |
1995年 | 1116篇 |
1994年 | 968篇 |
1993年 | 994篇 |
1992年 | 1787篇 |
1991年 | 1955篇 |
1990年 | 1817篇 |
1989年 | 1735篇 |
1988年 | 1604篇 |
1987年 | 1611篇 |
1986年 | 1618篇 |
1985年 | 1420篇 |
1984年 | 1210篇 |
1983年 | 1031篇 |
1979年 | 1059篇 |
1978年 | 829篇 |
1976年 | 713篇 |
1975年 | 747篇 |
1974年 | 1008篇 |
1973年 | 984篇 |
1972年 | 952篇 |
1971年 | 878篇 |
1970年 | 851篇 |
1969年 | 806篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
D. L. Clarke 《The Journal of small animal practice》2018,59(6):324-333
Feline ureteral obstructions are an increasingly recognised and challenging diagnostic and management problem. Many cats with ureteral obstructions are critically ill at the time of diagnosis, especially if there is dysfunction of the contralateral kidney. They may present with varying severities of acute kidney injury, electrolyte disturbances, and may have comorbidities such as heart disease that complicate perioperative and long‐term management. Medical management, which may consist of rehydration and restoration of intravascular volume with intravenous fluid therapy, osmotic diuresis, ureteral muscle relaxation, and antimicrobials for infection, is important in feline ureteral obstruction patients. Despite medical management, many cats with ureteral obstructions will require decompression of the obstructed kidney to relieve pressure‐nephropathy and restore urine flow. However, some cats may be too unstable for traditional medical management and require more emergent intervention to relieve the obstruction and address the life‐threatening sequelae to acute kidney injury, such as hyperkalaemia and fluid overload. Both surgical and interventional methods to address ureteral obstructions have been described in veterinary medicine, though debate continues as to the ideal approach. 相似文献
992.
Evaluating the effect of metronidazole plus amoxicillin‐clavulanate versus amoxicillin‐clavulanate alone in canine haemorrhagic diarrhoea: a randomised controlled trial in primary care practice 下载免费PDF全文
993.
994.
ABSTRACT1. The objectives of the current study were to investigate the mitochondrial genome and molecular phylogeny of Lueyang black-bone chicken, and provide molecule base to preserve and explore the specific chicken strain.2. Based on sequencing and clustering, the complete mitochondrial DNA map and sequences of Lueyang black-bone chicken were revealed, and two phylogenetic trees of Lueyang black-bone chickens based on D-loop sequences and the mitochondrial genome were constructed.3. The results showed that the complete mitochondrial genome of Lueyang black-bone chickens is 16,784bp in size, consisting of 22 transfer RNA genes, two ribosomal RNA genes, 13 protein-coding genes, and one non-coding control region. The base composition of the complete mtDNA sequence is 30.28% for A, 23.78% for T, 32.42% for C, 13.52% for G. Additionally, 10 haplotypes of D-loop sequences in 32 Lueyang black-bone chickens were detected, which were distributed into 4 clades (A, B, C and E).4. It was concluded that genetic diversity is wide in Lueyang black-bone chickens, and this strain has multiple maternal origins from different regions in China and neighbouring regions. 相似文献
995.
996.
Efficacy of a mephentermine‐based product as a vasopressor and a cardiac performance enhancer when given intramuscularly to cattle 下载免费PDF全文
D. N. Q. Cunha C. L. del Rio B. L. Youngblood E. L. Ferris G. E. Geist Y. Ueyama L. C. Franz S. Mathur R. L. Hamlin 《Journal of veterinary pharmacology and therapeutics》2018,41(2):274-280
The goal of this study was to confirm the vasopressor and cardiac effects of POTENAY® INJETÁVEL (POT), a mephentermine‐based product, given to cattle with induced vascular/cardiac depression. Ten healthy Holstein cattle (206 ± 13 kg) followed a randomized‐complete‐block design (RCBD) utilizing crossover study design. Each animal randomly received (1 ml/25 kg, IM) of either POT (n = 10) or volume‐matched placebo control (0.9%NaCl, CP, n = 10). A subset of animals (n = 5) received POT first (day 0) while the remaining (n = 5) received CP; after a six‐day washout period, cattle received the opposite compound. Animals were anesthetized and catheterized for systemic/left ventricular hemodynamic monitoring. Myocardial dysfunction/hypotension was induced by increasing the end‐tidal isoflurane concentration until arterial blood pressure was 20% lower than at baseline and remained stable. Once the animal was determined to be hypotensive and hemodynamically stable, steady‐state hypotensive baseline data (BL2) were acquired, and treatment with either POT or CP was given. Data were acquired post‐treatment at every 15 min for 90 min. POT improved cardiac output (+68 L/min, ±14%, p < 0.05), MAP (+14 mmHg, ±4%, p < 0.05), HR (+22 bpm, ±8%, p < 0.05), and peak rates of ventricular pressure change during both systole (dP/dtmax: +37 mmHg/s ±13%, p < 0.05) and diastole (dP/dtmin: +31 mmHg/s, ±7%, p < 0.05). No improvements were noted following placebo‐control administration. Results indicate that POT improves cardiac performance and systemic hemodynamics in cattle with induced cardiovascular depression when given as single intramuscular injection. 相似文献
997.
M. L. Stock S. T. Elazab W. H. Hsu 《Journal of veterinary pharmacology and therapeutics》2018,41(2):184-194
Triazines are relatively new antiprotozoal drugs that have successfully controlled coccidiosis and equine protozoal myeloencephalitis. These drugs have favorably treated other protozoal diseases such as neosporosis and toxoplasmosis. In this article, we discuss the pharmacological characteristics of five triazines, toltrazuril, ponazuril, clazuril, diclazuril, and nitromezuril which are used in veterinary medicine to control protozoal diseases which include coccidiosis, equine protozoal myeloencephalitis, neosporosis, and toxoplasmosis. 相似文献
998.
Silva D. C. Queiroz P. J. B. Caetano D. B. S Assis B. M. Rabelo R. E. Silva L. A. F. 《Tropical animal health and production》2018,50(7):1631-1636
Tropical Animal Health and Production - We aimed to follow the epidemiologic evolution of bovine digital dermatitis (BDD) and other podal diseases grouped in a dairy farm in Central Brazil between... 相似文献
999.
Nathaly Enciso Luciana L. K. Ostronoff Guillermo Mejías Leticia G. León María Luisa Fermín Elena Merino Cristina Fragio Luis Avedillo Concepción Tejero 《Veterinary research communications》2018,42(1):29-38
Adult Mesenchymal Stem Cells (MSC) are cells that can be defined as multipotent cells able to differentiate into diverse lineages, under appropriate conditions. These cells have been widely used in regenerative medicine, both in preclinical and clinical settings. Initially discovered in bone marrow, MSC can now be isolated from a wide spectrum of adult and foetal tissues. Studies to evaluate the therapeutic potential of these cells are based on their ability to arrive to damaged tissues. In this paper we have done a comparative study analyzing proliferation, surface markers and OCT4, SOX9, RUNX2, PPARG genes expression in MSC cells from Bone marrow (BMMSC) and Adipose tissue (ASC). We also analyzed the role of Stem Cell Factor (SCF) on MSC proliferation and on ASCs metalloproteinases MMP-2, MMP-9 secretion. Healthy dogs were used as BMMSC donors, and ASC were collected from omentum during elective ovariohysterectomy surgery. Both cell types were cultured in IMDM medium with or without SCF, 10% Dog Serum (DS), and incubated at 38 °C with 5% CO2. Growth of BMMSCs and ASCs was exponential until 25–30 days. Flow citometry of MSCs revealed positive results for CD90 and negative for CD34, CD45 and MCH-II. Genes were evaluated by RT-PCR and metalloproteinases by zymografy. Our findings indicate morphological and immunological similarities as well as expression of genes from both origins on analyzed cells. Furthermore, SCF did not affect proliferation of MSCs, however it up-regulated MMP-2 and MMP-9 secretion in ASCs. These results suggest that metalloproteinases are possibly essential molecules pivoting migration. 相似文献
1000.
Influence of caudal epidural analgesia on cortisol concentrations and pain‐related behavioral responses in mares during and after ovariectomy via colpotomy 下载免费PDF全文