全文获取类型
收费全文 | 127045篇 |
免费 | 7148篇 |
国内免费 | 133篇 |
专业分类
林业 | 6240篇 |
农学 | 4041篇 |
基础科学 | 770篇 |
15034篇 | |
综合类 | 20931篇 |
农作物 | 4661篇 |
水产渔业 | 6022篇 |
畜牧兽医 | 66723篇 |
园艺 | 1621篇 |
植物保护 | 8283篇 |
出版年
2018年 | 1811篇 |
2017年 | 1891篇 |
2016年 | 1778篇 |
2015年 | 1592篇 |
2014年 | 1820篇 |
2013年 | 5114篇 |
2012年 | 3497篇 |
2011年 | 4090篇 |
2010年 | 2732篇 |
2009年 | 2680篇 |
2008年 | 3992篇 |
2007年 | 3930篇 |
2006年 | 3638篇 |
2005年 | 3381篇 |
2004年 | 3197篇 |
2003年 | 3377篇 |
2002年 | 3123篇 |
2001年 | 3707篇 |
2000年 | 3638篇 |
1999年 | 2959篇 |
1998年 | 1251篇 |
1997年 | 1274篇 |
1995年 | 1403篇 |
1994年 | 1223篇 |
1993年 | 1222篇 |
1992年 | 2501篇 |
1991年 | 2768篇 |
1990年 | 2642篇 |
1989年 | 2712篇 |
1988年 | 2491篇 |
1987年 | 2421篇 |
1986年 | 2574篇 |
1985年 | 2472篇 |
1984年 | 2070篇 |
1983年 | 1843篇 |
1982年 | 1263篇 |
1979年 | 1939篇 |
1978年 | 1505篇 |
1977年 | 1433篇 |
1976年 | 1392篇 |
1975年 | 1440篇 |
1974年 | 1781篇 |
1973年 | 1813篇 |
1972年 | 1736篇 |
1971年 | 1598篇 |
1970年 | 1606篇 |
1969年 | 1569篇 |
1968年 | 1351篇 |
1967年 | 1422篇 |
1966年 | 1175篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
262.
R. Zabielski S. G. Pierzynowski 《Journal of animal physiology and animal nutrition》1992,68(3):146-150
Eine Methode zur langfristigen Lymphsammlung aus der jejunalen Lymphbahn bei Schweinen und Schafen Es wird eine Methode zur langfristigen Lymphsammlung im Dünndarmbereich von Schweinen und Schafen vorgestellt. Mit Hilfe eines chirurgischen Eingriffs wurde ein Silikon-Katheder im truncus lymphaticus jejunalis implantiert. Zusätzlich wurde ein zweiter Katheter in die hintere vena cava in Richtung Herz eingesetzt. Beide Katheter wurden sofort miteinander verbunden, um die Wiedereinführung der jejunalen Lymphe in den Blutkreislauf zu gewährleisten. Der negative Druck in der hinteren vena cava im Thoraxteil förderte den Lymphfluß durch das Katheter im truncus lymphaticus jejunalis. Der preprandiale Lymphfluß des Jéjunums betrug bei Schweinen 0,3 ml/h/kg Körpergewicht und stieg postprandial auf 0,78 ml/h/kg an. Beim Schaf betrug der Basiswert 0,75 ml/h/kg. Er stieg nach intraduodenaler Infusion von Rapsöl auf 4,75 ml/h/kg. Eine mechanische Stimulation der intestinalen Receptoren durch 0,9% NaCl-Lösung stimulierte ebenfalls den Lymphfluß. 相似文献
263.
Management of the lactating sow influences milk production and subsequent reproduction through changes in nutrient intake. The management goal during lactation is to maximize feed intake. Decreasing the effective environmental temperature, increasing the nutrient density of the lactation diet, maintaining fresh adequate supplies of feed and water, and preventing excess weight gain during the prior gestation period will increase nutrient intake during lactation. Effective environmental temperature of the lactating sow can be maintained in the thermoneutral zone by using drip cooling, increased ventilation rates and flooring materials with superior conductive properties. Sow parity, genetics, litter size, and disease level will also influence feed intake. Management practices must account for these factors and, thus, should be tailored to individual farm situations to ensure adequate nutrient intake and prevent aberrations in subsequent reproductive performance. 相似文献
264.
Long‐term experiments are a classical case of repeated measurements. Traits are measured on the same experimental unit over many years so that correlations arise between the observations made on the same plot in consecutive years. This paper describes the analysis of a three‐crop‐rotation long‐term experiment. We analysed the yields of the crops and the organic carbon content in the topsoil over 30 consecutive years. Several variance–covariance approaches are discussed and the trait‐specific best fit is interpreted. Mixed models are used to describe the structure of the experiment. Both yields and soil organic carbon show a more or less pronounced variance heterogeneity. Especially for yields, the heterogeneity of cycles and years is dominant. The consideration of correlations results in a better model fit in all cases. 相似文献
265.
Gore Tex organoids and genetic drugs 总被引:2,自引:0,他引:2
B J Culliton 《Science (New York, N.Y.)》1989,246(4931):747-749
266.
J B Herrick 《Veterinary Clinics of North America: Food Animal Practice》1989,5(3):457-469
Marketing to veterinarians is the process of synchronizing the business aspects of his or her goods and services so that they are understood and desired by animal owners. The basic components of a successful marketing program are in four categories: the individual, the situation, the needs, and the implementation. Each category is important and all are interrelated; however, the implementation of a program should not begin until a self-analysis has been done and the situation and its needs are thoroughly researched. Programs that have been used by successful practitioners can be copied. No program can be effective unless the economic status of the client's enterprise is known and understood. 相似文献
267.
An experiment comprising 19 German Landrace sows was established to evaluate the effect of folic acid supplements (10 mg/kg concentrate) on homocysteine and folic acid concentration in plasma and serum, respectively, of highly pregnant sows as compared to an unsupplemented control (basal diet contained 0.62 mg folic acid/kg concentrate). Blood samples were taken between day 75 and 110 of gestation for homocysteine analysis and on day 100 of gestation for folic acid determination. Due to the folic acid supplements serum folic acid concentration increased significantly (104 nmol/l in controls and 140 nmol/l in supplemented sows). In contrast, homocysteine concentration in the plasma was not significantly influenced by folic acid supplements (16.6 mumol/l in controls and 15.2 mumol/l in supplemented sows). Further investigations seem to be necessary to clarify the physiology of homocysteine metabolism in swine. 相似文献
268.
S Cavirani C S Cabassi G Donofrio B De Iaco S Taddei C F Flammini 《Preventive veterinary medicine》2001,50(1-2):145-151
Although the seroprevalence of Chlamydia psittaci is widespread in Italian dairy herds, its role in inducing genital disorders has not been elucidated. We therefore set up a case-control study to compare seroprevalence to C. psittaci in an aborted-cow population and in a randomly selected control group in the province of Parma (the Po Valley of northern Italy). The true seroprevalence (45%) in aborted cows was significantly higher than that in the control group (24%) (adjusted odds ratio=2.53). 相似文献
269.
F. RODRÍGUEZ G. A. RAMÍREZ A. S. RAMÍREZ H. J. BALL A. ESPINOSA
DE LOS MONTEROS A. FERNNDEZ 《Zoonoses and public health》2002,49(5):226-229
Samples from the mammary tissue of 14 lactating goats (12 naturally infected and two experimentally infected) were examined for the presence of Mycoplasma agalactiae. A monoclonal antibody (5G12) was applied to formalin‐fixed, paraffin‐wax‐embedded sections and labelled by the avidin–biotin peroxidase complex (ABC) method. Histological examination of tissue sections revealed strong immunoreactivity in all animals included in the study. Mycoplasma agalactiae antigen was mainly detected in the cellular debris at the periphery of purulent exudates present within lactiferous sinuses, and lactiferous and interlobular ducts. In addition, M. agalactiae organisms appeared in the cytoplasm of the epithelium of ducts, and in infiltrating macrophages and neutrophils within the ducts, alveoli, interstitial tissue and regional lymph node sinuses. It is concluded that this monoclonal antibody‐based immunohistochemical technique is an efficient and specific method for the post‐mortem detection of M. agalactiae in cases of clinical mastitis as well as being a useful tool for the study of the route of infection and cellular types involved during mastitis caused by this organism. 相似文献
270.
Taenia saginata cyst fluid was examined for host proteins; IgG1 and IgG2 as well as haemolytic complement activity were detected. Polyacrylamide gel electrophoresis revealed differences in proteinograms among the samples taken from 1-, 4-, and 10-month old cysts. Fluid from older cysts had fewer protein components and showed a weaker antigenic reaction with sera of bovines infected with T. saginata than that of younger cysts. The roles of antibody and complement in initiating degeneration of the parasite are discussed. 相似文献