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   92168篇
  免费   3331篇
  国内免费   38篇
林业   3739篇
农学   3463篇
基础科学   661篇
  11302篇
综合类   13529篇
农作物   3365篇
水产渔业   4968篇
畜牧兽医   47711篇
园艺   1165篇
植物保护   5634篇
  2020年   774篇
  2019年   981篇
  2018年   1582篇
  2017年   1848篇
  2016年   1674篇
  2015年   1404篇
  2014年   1718篇
  2013年   3717篇
  2012年   2928篇
  2011年   3588篇
  2010年   2339篇
  2009年   2329篇
  2008年   3470篇
  2007年   3208篇
  2006年   3135篇
  2005年   2668篇
  2004年   2576篇
  2003年   2591篇
  2002年   2372篇
  2001年   3389篇
  2000年   3304篇
  1999年   2553篇
  1998年   983篇
  1997年   1051篇
  1996年   883篇
  1995年   1022篇
  1994年   895篇
  1993年   896篇
  1992年   1845篇
  1991年   1919篇
  1990年   1856篇
  1989年   1858篇
  1988年   1607篇
  1987年   1594篇
  1986年   1627篇
  1985年   1526篇
  1984年   1225篇
  1983年   1032篇
  1982年   713篇
  1979年   1060篇
  1978年   816篇
  1975年   815篇
  1974年   897篇
  1973年   864篇
  1972年   805篇
  1971年   795篇
  1970年   800篇
  1969年   780篇
  1968年   708篇
  1967年   734篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
In three Austrian rabbit units (two in the west, one in the east) heavy losses occurred in April/May 1989. The clinical course (deaths in adult animals, haemorrhagic diathesis) of the disease was indicative for an infection with the RHD-virus. Necropsy confirmed the suggestive clinical diagnosis as bleeding of the nostrils, hyperaemia in the respiratory tract, spleen tumor, partly decolorized livers, hyperaemia of kidneys with rare petechias could be observed. Histologic examination revealed centrolobular liver necrosis, lung bleeding and edema, tumor of spleen and atrophy of spleen follicles. Rabbits infected with organ suspensions died within 48 hours. The organ suspensions and the suspensions of the already necropsied animals showed a haemagglutination titer for above 1:100. This reaction could be inhibited with a specific RHD-antiserum. The intramuscular application of a RHD-reference strain in one hare, two wild rabbits and a rabbit did not induce clinical disease or death of the leporids during a six week observation period. The rabbit died within 48 hours post infection. However the hare and wild rabbits showed high antibody titers by ELISA at the end of the observation period. Before infection the two wild rabbits were serologically negative.  相似文献   
163.
Bilateral metacarpophalangeal radiographs of 100 Thoroughbreds were examined for visualization and location of the major nutrient foramen of the proximal phalanx. The foramina were located on the dorsal or palmar aspects of the cortex or were not visible radiographically. Of the 100 horses, 60 had the same pattern in both forefeet. In the remaining 40 horses, the left and right proximal phalangeal foramina were asymmetric. Of the 200 proximal phalangeal foramina (100 horses), 53 were on the dorsal aspect of the cortex and 101 were on the palmar aspect of the cortex; 46 were not visible radiographically. Significant effect of age or gender could not be determined.  相似文献   
164.
The adequacy of postoperative analgesia was assessed in 40 cats following ovariohysterectomy. At extubation, cats were given one dose of carprofen, ketoprofen, meloxicam or tolfenamic acid. Postoperative analgesia was assessed using visual analogue scale (VAS) scoring for pain and sedation; measurement of mechanical nociceptive thresholds at the wound; recognition of the requirement for rescue intervention analgesia; and an overall clinical assessment score at 18 hours. VAS pain scores were low throughout the trial, with no significant differences found between the groups. Postoperative mechanical nociceptive thresholds decreased significantly from baseline in all four groups, with no significant differences between the groups. One cat in each of the tolfenamic acid, ketoprofen and meloxicam groups required rescue intervention analgesia. Nine out of 10 cats in all four groups were classified as having desirable overall clinical assessment scores. In summary, all four drugs provided good postoperative analgesia, although none was able to prevent postoperative wound tenderness.  相似文献   
165.
Superovulation of female rabbits was induced by subcutaneous injection(s) of porcine FSH. Zygotes were recovered 17 to 19 hr after hCG injection and were classified into two categories under a microscope equipped with Nomarski interference-contrast optics at x 200 magnification: (A) zygotes with clearly visible pronuclei, or (B) zygotes with visualized pronuclei after 10 min centrifugation at 12,000 x g. No significant difference between strains was found in the proportion of category-A zygotes (JW 72.6% vs NZW 79.3%). Pronuclei of category-A zygotes were located in the center of the cytoplasm, and the pronuclei of category-B zygotes were slightly moved by centrifugation toward the mass of cytoplasmic lipid droplets. Exogenous DNA solution (5 microg/ml of fusion gene composed of bovine alphaS1-casein promoter and human growth hormone structural gene) was microinjected into the pronucleus of the JW zygotes. The pronucleus of category-A zygotes with a mean volume of 7.4 pl swelled up to 16.6 pl (132% increase), while that of category-B zygotes with a mean volume of 6.1 pl swelled up to 15.9 pl (148% increase). Nevertheless, similar proportions of category-A and category-B zygotes developed into offspring after transfer to recipient females (11.1 and 11.2%, respectively). The efficiency to produce hGH-carrying transgenic rabbits was 0.9% (2/235) from category-A zygotes and 0.5% (1/215) from category-B zygotes (P>0.05). To date, transgenic rabbits have been produced without centrifugation of pronuclear zygotes. However approximately 25% of fertilized rabbit zygotes can be used for DNA microinjection after they have been centrifuged to visualize their pronuclei.  相似文献   
166.
A survey of aldicarb poisoning in companion animals was conducted by posting questionnaires to all private practitioners in Gauteng Province, South Africa. The survey was designed to determine the percentage of aldicarb cases seen, treatment regimen, clinical signs observed, proposals for preventative actions and more effective treatments. Other questions included duration of treatment, survival rate, cost to clients, post mortem findings and reasons for poisonings.  相似文献   
167.
168.
169.
Seven wild-caught ball pythons (Python regius), including six gravid females and one male, were obtained from Africa and were housed in a government animal facility in Research Triangle Park, North Carolina. Upon arrival, the snakes were found to be infested with ticks (Aponomma latus), which were manually removed. Four weeks following arrival, vesicular skin lesions began to appear on the snakes. Despite treatment of all affected female snakes with amikacin (5 mg/kg i.m., every 3 days) and cefotaxime (25 mg/kg i.m., every 3 days), the condition progressed and five of the female snakes died 7 wk after arrival. The remaining male and one female improved after an increase in environmental temperature, with ecdysis followed by healing. Physiologic stress, ectoparasites, and shipping may have predisposed the snakes to sepsis.  相似文献   
170.
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