首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   174294篇
  免费   9542篇
  国内免费   94篇
林业   8038篇
农学   5720篇
基础科学   1185篇
  21162篇
综合类   30886篇
农作物   6796篇
水产渔业   8532篇
畜牧兽医   88858篇
园艺   2231篇
植物保护   10522篇
  2018年   2469篇
  2017年   2805篇
  2016年   2619篇
  2015年   2223篇
  2014年   2648篇
  2013年   6810篇
  2012年   4878篇
  2011年   5993篇
  2010年   3962篇
  2009年   3888篇
  2008年   5927篇
  2007年   5479篇
  2006年   5321篇
  2005年   4760篇
  2004年   4735篇
  2003年   4724篇
  2002年   4479篇
  2001年   5748篇
  2000年   5623篇
  1999年   4307篇
  1998年   1795篇
  1997年   1850篇
  1996年   1661篇
  1995年   2001篇
  1994年   1843篇
  1993年   1795篇
  1992年   3639篇
  1991年   3851篇
  1990年   3784篇
  1989年   3752篇
  1988年   3408篇
  1987年   3433篇
  1986年   3576篇
  1985年   3451篇
  1984年   2778篇
  1983年   2494篇
  1982年   1705篇
  1981年   1580篇
  1979年   2538篇
  1978年   2016篇
  1977年   1646篇
  1976年   1659篇
  1975年   1792篇
  1974年   2197篇
  1973年   2220篇
  1972年   2137篇
  1971年   2085篇
  1970年   1987篇
  1969年   1850篇
  1967年   1651篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Nonweightbearing lameness secondary to synovial sarcoma in a young dog   总被引:1,自引:0,他引:1  
Synovial sarcoma was diagnosed in the right carpus of a 2 1/2-year-old mixed-breed dog. The dog had developed a right forelimb lameness before one year of age. The lameness was progressive for nearly 2 years, resulting in severe disuse atrophy of the right forelimb musculature and pronounced osteopenia. A definitive diagnosis was not made until the dog was referred after 2 years of conservative treatment was ineffectual. Right forelimb amputation was done and the dog survived an additional 15 months. The protracted clinical course before definitive diagnosis underscores the need for aggressive pursuit of a diagnosis when conservative treatment of a lameness is not efficacious.  相似文献   
992.
Avian rotaviruses were isolated from turkeys with enteritis using MA 104 cell line. MA 104 cells were suitable for primary isolation and propagation of avian rotaviruses. Trypsin appeared essential for the enhancement of infectivity and the occurrence of cytopathic effect (CPE). Serum neutralization (SN), electron microscopy (EM), and analysis of genomic RNA were done to identify and confirm the identity of rotaviruses. Electrophoretic migration patterns of genomic RNA from avian rotaviruses were examined, and they were compared with those from mammalian rotaviruses. The migration patterns differed between these groups.  相似文献   
993.
994.
The aim of the present study was to establish the effect of intravesical administration of resiniferatoxin (RTX) and tetrodotoxin (TTX) on the chemical coding of paracervical ganglion (PCG) neurons supplying the urinary bladder in the pig. In order to identify the PCG neurons innervating the bladder, retrograde tracer Fast Blue was injected into the bladder wall prior to intravesical RTX or TTX administration. Consequent application of immunocytochemical methods revealed that in the control group 76.82% of Fast Blue positive PCG neurons contain nitric oxide synthetase (nNOS), and 66.92% contain acetylcholine transferase (ChAT). Intravesical infusion of RTX resulted in a reduction of the nNOS-IR neurons to 57.74% and ChAT-IR to 57.05%. Alternative administration of TTX induced an increase of nNOS-IR neurons up to 79.29% and a reduction of the ChAT-IR population down to 3.73% of the Fast Blue positive PCG cells. Our data show that both neurotoxins affect the chemical coding of PCG cells supplying the porcine urinary bladder, but the effects of their action are different. Moreover, these results shed light on the possible involvement of NO-ergic and cholinergic neurons in the mechanisms of therapeutic action exerted by RTX and TTX in curing the overactive bladder disorder.  相似文献   
995.
996.
997.
1. Effective nutritional approaches to counteract the negative effects of stress may provide food animal producers with useful alternatives to antibiotics. In this study, turkeys were fed on a standard diet, or the same diet supplemented with yeast extract (YE), to determine if YE would improve disease resistance in a stress model.

2. At 16 weeks of age, half of the birds were exposed to a bacterial challenge using a coarse spray of the pen environment. A subset of control and challenged birds was also treated with dexamethasone (Dex) prior to challenge (Dex/challenge). At 18 weeks, another subset was subjected to a 12?h transport stress protocol (Challenge/transport). All birds were bled and necropsied the morning after transport. The numbers and proportions of blood cells and the heterophil oxidative burst activity (OBA) were determined. Serum corticosterone (Cort) levels of male birds were measured using a commercial ELISA kit. Body weight and gain were increased by YE during week 1.

3. YE decreased mortality and bacterial isolation following Dex/challenge only in females. Cort levels in male turkeys were decreased by YE and Dex treatment. OBA was higher in males and in birds given YE and was reduced by challenge and transport.

4. These results suggest there may be gender differences in the turkey stress response and that dietary YE has potential for modulating the impact of stress on innate immunity of turkeys.  相似文献   

998.
CASE: A 13-week-old female boxer pup was found to be suffering from rigidity of the left hindleg. Antibiotic and anti-inflammatory treatment over a 3-week period failed to improve the condition and the pup was humanely killed. METHODS: Serological examination for Neospora antibodies was carried out by the indirect fluorescent antibody test and for Toxoplasma gondii antibodies with a latex agglutination test. A variety of tissues were examined histologically, and the central nervous system by immunohistochemistry and the polymerase chain reaction. RESULTS: The IFAT for anti-Neospora antibodies showed a titre of 1:51 200 in the clinically affected pup while the latex agglutination test for Toxoplasma antibodies was negative. The dam and one of two tested litter-mates had anti-Neospora IFAT titres of 1:1600, the other litter mate was negative. All three were not clinically affected. Histological, immunohistochemical and polymerase chain reaction examinations of the affected pup confirmed the diagnosis of Neospora infection. CONCLUSION: In the live animal, serological examination is thought to be the most useful specific test. Post-mortem examination by traditional histology, immunohistochemistry and the polymerase chain reaction confirmed the diagnosis. The case is discussed in the context of present knowledge about Neospora infection in New Zealand.  相似文献   
999.
1000.
A 7-month-old La Mancha doe was presented with a right head tilt and ventral strabismus while circling to the left. History and physical examination led to a tentative diagnosis of a cerebral abscess. Computed tomography revealed a large, complex mass with ring enhancement in the left cerebral hemisphere, supporting the diagnosis. Postmortem examination confirmed the cerebral abscess. Bacterial cultures yielded heavy growth of Actinomyces pyogenes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号