全文获取类型
收费全文 | 165536篇 |
免费 | 9109篇 |
国内免费 | 122篇 |
专业分类
林业 | 6633篇 |
农学 | 5401篇 |
基础科学 | 1013篇 |
20995篇 | |
综合类 | 27490篇 |
农作物 | 6367篇 |
水产渔业 | 8582篇 |
畜牧兽医 | 85191篇 |
园艺 | 2217篇 |
植物保护 | 10878篇 |
出版年
2019年 | 1632篇 |
2018年 | 2484篇 |
2017年 | 2770篇 |
2016年 | 2501篇 |
2015年 | 2127篇 |
2014年 | 2664篇 |
2013年 | 6446篇 |
2012年 | 4878篇 |
2011年 | 6070篇 |
2010年 | 3950篇 |
2009年 | 4061篇 |
2008年 | 6022篇 |
2007年 | 5630篇 |
2006年 | 5265篇 |
2005年 | 4960篇 |
2004年 | 4709篇 |
2003年 | 4879篇 |
2002年 | 4336篇 |
2001年 | 5390篇 |
2000年 | 5486篇 |
1999年 | 4347篇 |
1998年 | 1836篇 |
1997年 | 1743篇 |
1996年 | 1594篇 |
1995年 | 1945篇 |
1994年 | 1724篇 |
1993年 | 1565篇 |
1992年 | 3375篇 |
1991年 | 3504篇 |
1990年 | 3394篇 |
1989年 | 3371篇 |
1988年 | 3103篇 |
1987年 | 3109篇 |
1986年 | 3175篇 |
1985年 | 3028篇 |
1984年 | 2472篇 |
1983年 | 2182篇 |
1982年 | 1476篇 |
1979年 | 2221篇 |
1978年 | 1790篇 |
1977年 | 1475篇 |
1976年 | 1519篇 |
1975年 | 1633篇 |
1974年 | 1898篇 |
1973年 | 1901篇 |
1972年 | 1818篇 |
1971年 | 1645篇 |
1970年 | 1590篇 |
1969年 | 1648篇 |
1967年 | 1420篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
S A Robertson 《Veterinary Clinics of North America: Small Animal Practice》1989,19(2):289-306
The body regulates pH closely to maintain homeostasis. The pH of blood can be represented by the Henderson-Hasselbalch equation: pH = pK + log [HCO3-]/PCO2 Thus, pH is a function of the ratio between bicarbonate ion concentration [HCO3-] and carbon dioxide tension (PCO2). There are four simple acid base disorders: (1) Metabolic acidosis, (2) respiratory acidosis, (3) metabolic alkalosis, and (4) respiratory alkalosis. Metabolic acidosis is the most common disorder encountered in clinical practice. The respiratory contribution to a change in pH can be determined by measuring PCO2 and the metabolic component by measuring the base excess. Unless it is desirable to know the oxygenation status of a patient, venous blood samples will usually be sufficient. Metabolic acidosis can result from an increase of acid in the body or by excess loss of bicarbonate. Measurement of the "anion-gap" [(Na+ + K+) - (Cl- + HCO3-)], may help to diagnose the cause of the metabolic acidosis. Treatment of all acid-base disorders must be aimed at diagnosis and correction of the underlying disease process. Specific treatment may be required when changes in pH are severe (pH less than 7.2 or pH greater than 7.6). Treatment of severe metabolic acidosis requires the use of sodium bicarbonate, but blood pH and gases should be monitored closely to avoid an "overshoot" alkalosis. Changes in pH may be accompanied by alterations in plasma potassium concentrations, and it is recommended that plasma potassium be monitored closely during treatment of acid-base disturbances. 相似文献
992.
C. E. Cornelius B. A. Myers M. L. Bruss J. W. George 《Veterinary research communications》1989,13(5):395-401
Fasted Brazilian squirrel monkeys (BrSMs) exhibited slightly higher serum bilirubin levels (0.30±0.05 mg/dl) than others in the fed state (0.13±0.01). The mean liver weight was 50% lower following a 22 h fast. The rate of bile flow was unaffected by fasting and averaged 13.8 l/min/kg and 47.5 l/min/100g liver in six BrSMs. No significant difference in mean bilirubin excretion/min was observed on a body weight basis following fasting. When the mean rate of bilirubin excretion was calculated as a function of liver weight, a two-fold higher rate was present in fasted monkeys, but only at the p=0.06 level of statistical significance. From data collected in this and earlier studies, it would appear that BrSMs represent the best animals studied to date to serve as experimental controls in comparative studies with Bovilian squirrel monkeys which exhibit a Gilbert-like syndrome. 相似文献
993.
F. Atroshi J. Parantainen S. Sankari T. Österman 《Veterinary research communications》1989,13(6):427-433
Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) cocentrations in milk and plasma samples from healthy and mastitic cows were determined by radioi-immunoassay and compared with prostaglandins (PGE2, PGF2 and thromboxane B2 [TXB2]), phospholipids and other relevant parameters in milk and blood. The concentrations of cAMP were about five times higher in plasma (p<0.01) than in milk, whereas the cGMP concentration in milk was three times higher (p<0.01) than that in plasma in both healthy and diseased animals. In mastitic milk, the cAMP and cGMP concentrations were 19% and 65% and in blood plasma 13% and 84% higher respectively than in healthy animals. In milk, cyclic nucleotide concentrations correlated with the markedly elevated cell count and also with the prostaglandin concentration and pH. In blood, cAMP correlated positively with phospholipids and cGMP with reduced glutathione (GSH). These changes are considered to be important in the disease process and, in particular, the increase in cGMP deserves further study. 相似文献
994.
The paper describes pathomorphological findings in two dogs and one cat with the intention to clarify whether these animals died by drowning. The investigations are supplemented by experimental results of water instillation into the lung to induce signs of emphysema aquosum post mortem. Additionally, histopathology of the skin lesions due to water exposition after death are demonstrated by systematic investigations of four different localizations for 10 days. Critical evaluation of the results and literature references in human forensic pathology indicate that post mortem findings as described in this paper, especially those of the so called "drowning lung" can be attributed to death by drowning. 相似文献
995.
996.
Hagemoser WA 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1989,18(1):17-20
An intravenous bile acid loading test was performed on 16 goats using various dosages and sampling protocols. A recently developed enzymatic bile acid assay provided an economical and technologically simple method for bile acid analysis. Intravenous injection of bile salts into goats was well tolerated. Clearance times were rapid. A protocol for performance of the test was suggested and a practical reference range for T 1/2 clearance of 4+/-1 minute was determined. Further investigations of this test in the assessment of liver function in the ruminant appear warranted. 相似文献
997.
998.
Randomized placebo-controlled crossover studies were carried out in dogs to evaluate how two non-steroidal anti-inflammatory drugs (NSAID) might modulate an acute post-traumatic inflammatory reaction. Two "identical" surgical interventions were performed on the forelimbs of each animal with an interval of 28 days, to enable a paired comparison of the inflammatory signs and the wound/bone healing processes. At one operation 8 dogs received 300 mg phenylbutazone twice daily for 8 days starting on the day before surgery, and at the other operation matching placebo tablets were given. In a similar placebo-controlled trial another group of 8 dogs received 5 mg indomethacin twice daily. With phenylbutazone the post-operative swelling was not significantly reduced compared to placebo, but there was less pain and limping. With indomethacin the swelling was somewhat reduced, but there was no consistent difference to placebo in the pain and limping assessments. None of the drugs appeared to distinctly effect the wound or fracture healing, as evaluated by clinical inspection, comparison of radiographs and comparison of bone sections from the sites of surgery. It proved difficult to select an appropriate dosage of indomethacin due to its high potential to induce GI ulceration and bleeding in dogs. In this experimental surgical model with an acute inflammation, neither phenylbutazone nor indomethacin showed impressive anti-inflammatory or analgesic properties. In the same model paracetamol has proved to significantly and more efficiently, reduce both swelling and pain without any noticeable adverse effects, and appears to be a better alternative than the two presently tested NSAID. 相似文献
999.
1000.
A Leoni A M Nieddu F Guarda M Castagnaro A Firinu P Cossu V Mingioni 《Schweizer Archiv für Tierheilkunde》1989,131(6):361-368
A severe neurological disorder was observed during a very dry season, in sheep pasturing on land with mediterranean vegetation. During the crisis, lasting 5-20", ataxia and convulsions were the main clinical signs. Brain congestion, spongy appearance of the liver, interstitial nephritis and hyperpigmentation of visceral lymph nodes were the most important macroscopic lesions. Histopathological, histochemical and ultrastructural findings confirmed liver and kidney lesions and showed considerable neurovisceral storage of lipofuscin. Although further toxicological and experimental studies are needed to elucidate the origin of the disease, the Authors attribute the outbreak of the neurological syndrome to the ingestion of a neurotoxin containing plant. 相似文献