全文获取类型
收费全文 | 816篇 |
免费 | 41篇 |
专业分类
林业 | 4篇 |
农学 | 26篇 |
基础科学 | 4篇 |
90篇 | |
综合类 | 105篇 |
农作物 | 68篇 |
水产渔业 | 53篇 |
畜牧兽医 | 474篇 |
园艺 | 16篇 |
植物保护 | 17篇 |
出版年
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 29篇 |
2012年 | 22篇 |
2011年 | 22篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 25篇 |
2007年 | 32篇 |
2006年 | 25篇 |
2005年 | 26篇 |
2004年 | 24篇 |
2003年 | 36篇 |
2002年 | 29篇 |
2001年 | 30篇 |
2000年 | 24篇 |
1999年 | 18篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1992年 | 16篇 |
1991年 | 27篇 |
1990年 | 14篇 |
1989年 | 26篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 10篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 9篇 |
1974年 | 16篇 |
1973年 | 10篇 |
1971年 | 8篇 |
1970年 | 8篇 |
1968年 | 9篇 |
1967年 | 8篇 |
1966年 | 8篇 |
1963年 | 10篇 |
排序方式: 共有857条查询结果,搜索用时 15 毫秒
101.
The result of alterations in the levels of CCK, in the blood and in the cerebrospinal fluid, on the functioning of the growth hormone axis has been examined in sheep. Male Coopworth sheep of about 40 kg liveweight were given various doses of CCK either intracerebroventricularly (icv) or intravenously (iv). Other similar sheep were given various doses of a CCK antagonist (loxiglumide) by the same routes. Bolus iv administration of either 35 μg or 200 μg of CCK had no effect on plasma GH levels. When given icv, however, CCK resulted in a marked (P<0.01) prolonged depression in plasma GH levels. The decrease in GH secretion could be partially attenuated by concurrent administration of loxiglumide, but was completely unaffected by concurrent administration of anti-somatostatin serum icv. Loxiglumide alone had no effect on plasma GH levels when given at up to 200 μg icv, but intravenous administration of 8 mg of the CCK antagonist resulted in an increase in plasma GH concentrations (P<0.05). Plasma levels of somatostatin, glucose and cortisol were unaffected by both icv and iv administration of CCK. These results show that CCK can have a strong GH-inhibiting effect in the brain. Furthermore, this effect seems to be independent of hypothalamic somatostatin, suggesting another GH-inhibiting system exists. 相似文献
102.
103.
Daniel A. Feeney DVM MS Gary R. Johnston DVM MS Carl A. Osborne DVM PhD Michael J. Tomlinson DVM PhD 《Veterinary radiology & ultrasound》1984,25(6):249-253
Prostatic and membranous urethral diameter was measured in 24 normal mature male Beagle dogs during maximum distension retrograde urethrocystography. This technique involved retrograde urethral distension by infusion with contrast medium until the urinary bladder was distended and the vesicourethral junction remained opened as observed by fluoroscopy. Lateral and ventro-dorsal radiographs were made during subsequent injections of 5–10 ml of contrast medium. The prostatic urethra was consistently greater in diameter than the membranous urethra. However, the numerical ratio between the prostatic urethral diameter and the membranous urethral diameter varied among these dogs by a factor of 2 at the numerical extremes. 相似文献
104.
Wennerstrand J Johnston C Roethlisberger-Holm K Erichsen C Eksell P Drevemo S 《Equine veterinary journal》2004,36(8):707-711
REASONS FOR PERFORMING STUDY: Earlier studies have developed a clinical tool to evaluate objectively the function of the equine back. The ability to differentiate horses with back pain from asymptomatic, fully functioning horses using kinematic measures from this tool has not been evaluated. OBJECTIVES: To compare the kinematics of the back at walk and trot in riding horses with back dysfunction to the same parameters in asymptomatic sport horses. METHODS: The kinematics of the back in 12 horses with impaired performance and back pain were studied at walk and trot on a treadmill. Data were captured for 10 sees at 240 Hz. Range of movement (ROM) and intravertebral pattern symmetry of movement for flexion and extension (FE), lateral bending (LB) and axial rotation (AR) were derived from angular motion pattern data and the results compared to an earlier established database on asymptomatic riding horses. RESULTS: At walk, horses with back dysfunction had a ROM smaller for dorsoventral FE in the caudal thoracic region (T13 = 7.50 degrees, T17 = 7.71 degrees; P<0.05), greater for LB at T13 (8.13 degrees; P<0.001) and smaller for AR of the pelvis (10.97 degrees; P<0.05) compared to asymptomatic horses (FE-T13 = 8.28 degrees, FE-T17 = 8.49 degrees, LB-T13 = 6.34 degrees, AR-pelvis = 12.77 degrees). At trot, dysfunctional horses had a smaller (P<0.05) ROM for FE at the thoracic lumbar junction (T17 = 2.46 degrees, L1 = 2.60 degrees) compared to asymptomatic horses (FE-T17 = 3.07 degrees, FE-L1 = 3.12 degrees). CONCLUSIONS: The objective measurement technique can detect differences between back kinematics in riding horses with signs of back dysfunction and asymptomatic horses. The clinical manifestation of back pain results in diminished flexion/extension movement at or near the thoracic lumbar junction. However, before applying the method more extensively in practice it is necessary to evaluate it further, including measurements of patients whose diagnoses can be confirmed and long-term follow-ups of back patients after treatment. POTENTIAL RELEVANCE: Since the objective measurement technique can detect small movement differences in back kinematics, it should help to clinically describe and, importantly, objectively detect horses with back pain and dysfunction. 相似文献
105.
106.
107.
OBJECTIVE: To determine historical, physical, and clinical factors that may affect morbidity and mortality in horses with small intestinal volvulus unrelated to other causes (e.g., incarceration, lipoma, etc.). STUDY DESIGN: Retrospective study. ANIMALS: Client-owned horses (115), aged 1 month to 21 years. Methods: Data were obtained from medical records, identified by computer search and manual review. Continuous variables were compared between affected and non-affected horses with Mann-Whitney U-tests and non-continuous variables with Fisher's exact test (2 x 2 tables) or chi(2)-tests (larger tables). Stepwise logistic regression analysis was used to develop a multivariable model of the risk factors, taking account of confounding and interaction. RESULTS: Eighty percent of horses recovered from surgery survived to hospital discharge. Neither age, breed, nor sex was related to mortality. Survivors had a significantly lower heart rate, shorter capillary refill time, and better mucous membrane color. Variables associated with worsening cardiovascular status, increased hemoconcentration, and exudation of cells and protein into peritoneal fluid were significantly associated with non-survival. After recovery from surgery, the most serious complication was colic, which was significantly associated with non-survival (P=.028) as was a second celiotomy (P<.01). Both of these complications were associated with a jejunocecostomy during the first surgery. CONCLUSIONS: Significant differences in the clinical and clinicopathologic signs were identified between survivors and non-survivors. CLINICAL RELEVANCE: These findings can be used to make a scientific assessment of prognosis in the pre-operative, operative, and post-operative management of horses with small intestinal volvulus. 相似文献
108.
Linde A Summerfield NJ Johnston M Melgarejo T Keffer A Ivey E 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2004,18(5):772-774
Heart disease has been described in the chinchilla and, with increasing popularity as a pet, the demand for diagnostic evaluation and treatment has increased. The goal of this study was to determine reference values for echocardiographic measurements in chinchillas and the effect of anesthesia on these measurements. Seventeen clinically healthy adult chinchillas were studied. All animals were anesthetized with isoflurane by mask. Standard echocardiographic views were used. A difference was seen in the echocardiographic measurements for left ventricular systolic dimension, fractional shortening, aortic (Ao) diameter, left atrial (LA) diameter, ratio of LA diameter to Ao diameter, and peak flow velocities and ejection times for Ao and pulmonary artery flows between awake and anesthetized chinchillas. 相似文献
109.
110.
Gray CA Blaxter AC Johnston PA Latham CE May S Phillips CA Turnbull N Yamagishi B 《Journal of veterinary medical education》2006,33(1):85-92
This article reports on the coordination of communications skills training in veterinary schools in the United Kingdom and Ireland and describes the progress and status of training that is occurring in six of these schools. 相似文献