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   111842篇
  免费   6378篇
  国内免费   53篇
林业   4552篇
农学   4028篇
基础科学   754篇
  14552篇
综合类   16509篇
农作物   4243篇
水产渔业   5773篇
畜牧兽医   59509篇
园艺   1416篇
植物保护   6937篇
  2019年   1162篇
  2018年   1964篇
  2017年   2257篇
  2016年   2038篇
  2015年   1646篇
  2014年   2085篇
  2013年   4819篇
  2012年   3511篇
  2011年   4345篇
  2010年   2882篇
  2009年   2855篇
  2008年   4201篇
  2007年   3922篇
  2006年   3763篇
  2005年   3183篇
  2004年   3076篇
  2003年   3076篇
  2002年   2787篇
  2001年   3878篇
  2000年   3804篇
  1999年   2934篇
  1998年   1163篇
  1997年   1215篇
  1996年   1009篇
  1995年   1212篇
  1994年   1062篇
  1993年   1055篇
  1992年   2143篇
  1991年   2230篇
  1990年   2180篇
  1989年   2180篇
  1988年   1877篇
  1987年   1870篇
  1986年   1895篇
  1985年   1786篇
  1984年   1486篇
  1983年   1275篇
  1979年   1429篇
  1978年   1059篇
  1976年   1055篇
  1975年   1180篇
  1974年   1311篇
  1973年   1247篇
  1972年   1156篇
  1971年   1070篇
  1970年   1093篇
  1969年   1136篇
  1968年   1055篇
  1967年   1104篇
  1966年   1001篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Ectopic teeth occur because of failure of the first branchial cleft to close during development and are found mostly in young horses. Such dentigerous cysts are often located at the base of the ear, forming a notable swelling with a fistula, as it was the case with the two year old Iceland mare ?Runa?. In order to confirm the diagnosis, x-ray images were taken, which is also necessary to locate the ectopic tooth correctly. While operating, the whole cystic membrane should be removed and it is important to prevent adjacent nerves and blood vessels from damage. Prognosis for complete healing after removing an ectopic tooth is excellent.  相似文献   
992.
993.
Understanding the inherent radiosensitivity and repair capacity of canine transitional cell carcinoma (TCC) can aid in optimizing radiation protocols to treat this disease. The objective of this study was to evaluate the parameters surviving fraction at 2 Gy (SF(2) ), α/β ratio and capacity for sublethal damage repair (SLDR) in response to radiation. Dose-response and split-dose studies were performed using the clonogenic assay. The mean SF(2) for three established TCC cell lines was high at 0.61. All the three cell lines exhibited a low to moderate α/β ratio, with the mean being 3.27. Two cell lines exhibited statistically increased survival at 4 and 24 h in the dose-response assay. Overall, our results indicate that the cell lines are moderately radioresistant, have a high repair capacity and behave similarly to a late-responding normal tissue. These findings indicate that the radiation protocols utilizing higher doses with less fractionation may be more effective for treating TCC.  相似文献   
994.
A nonhealing wound associated with a laceration in a 12-year-old llama was evaluated. Initial attempts at closure were unsuccessful and biopsy revealed scar tissue. Subsequent biopsies, 18 mo later, revealed squamous cell carcinoma with regional metastasis. This report describes squamous cell carcinoma, secondary to a traumatic wound in a llama.  相似文献   
995.
996.
997.
Urginea physodes (Jacq.) Bak., a species closely related to or possibly synonymous with U. pusilla, is described and its distribution given. Four bufadienolides were isolated from U. physodes and the approximated LD50 and cumulative effect of some of them determined in guinea pigs. The most toxic one proved to be mildly cumulative. Typical signs of acute cardiac glycoside poisoning, involving the locomotory, gastro-intestinal, respiratory and cardiac system, were seen in the field cases and/or were experimentally induced by the plant. Similar signs could also be induced by injecting the isolated bufadienolide, physodine A, to a sheep.  相似文献   
998.
999.
Common sites for blood sampling in the pekin duck and other avian species include the basilic vein, jugular vein, superficial plantar metatarsal vein, heart, and occipital sinus. The use of each of these sites is described and/or illustrated. In the present study using the pekin duck, the superficial plantar metatarsal vein proved most satisfactory for collecting repeated samples (every 5 minutes for 30 minutes) with minimal trauma to the duck.  相似文献   
1000.
The mydriatic effect of 10% phenylephrine was evaluated in 9 horses. Base-line pupillary size in mesopic conditions and during light stimulation was ascertained before application of pharmacologic agents. In study 1, 10% phenylephrine was applied to each eye (n = 5 horses). After 15 minutes, the pupillary size was determined in both lighting conditions. Phenylephrine was again applied to each eye, and after an additional 15 minutes, the pupillary size was determined. In study 2, 1% tropicamide was applied to each eye (n = 4 horses), and after 30 minutes, the pupillary size was determined in both lighting conditions. Tropicamide and phenylephrine were applied to each eye immediately after determination of pupillary size, and after an additional 30 minutes, the pupillary size was determined. There was no significant change (P greater than 0.9) in pupillary size when phenylephrine was used alone or when phenylephrine was used in an eye that had been dilated with tropicamide.  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