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   123416篇
  免费   7104篇
  国内免费   63篇
林业   5344篇
农学   3975篇
基础科学   730篇
  14435篇
综合类   20309篇
农作物   4511篇
水产渔业   6112篇
畜牧兽医   65464篇
园艺   1515篇
植物保护   8188篇
  2018年   1778篇
  2017年   1898篇
  2016年   1736篇
  2015年   1540篇
  2014年   1800篇
  2013年   4961篇
  2012年   3392篇
  2011年   4006篇
  2010年   2646篇
  2009年   2651篇
  2008年   3886篇
  2007年   3771篇
  2006年   3484篇
  2005年   3246篇
  2004年   3064篇
  2003年   3280篇
  2002年   3023篇
  2001年   3647篇
  2000年   3574篇
  1999年   2916篇
  1998年   1241篇
  1997年   1269篇
  1996年   1144篇
  1995年   1386篇
  1994年   1214篇
  1993年   1201篇
  1992年   2446篇
  1991年   2713篇
  1990年   2566篇
  1989年   2632篇
  1988年   2431篇
  1987年   2365篇
  1986年   2521篇
  1985年   2420篇
  1984年   2032篇
  1983年   1807篇
  1982年   1233篇
  1979年   1883篇
  1978年   1460篇
  1977年   1400篇
  1976年   1363篇
  1975年   1407篇
  1974年   1732篇
  1973年   1762篇
  1972年   1689篇
  1971年   1556篇
  1970年   1562篇
  1969年   1520篇
  1968年   1309篇
  1967年   1391篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
61.
62.
63.
64.
The medical records of 38 horses with puncture wounds of the navicular bursa were reviewed. Only 12 horses had a satisfactory outcome (breeding or riding). Of the remaining 26 horses, 19 were euthanized, five were sold due to persistent severe lameness, one died, and one was lost to long-term follow-up. Different combinations of conservative management prior to surgical debridement and drainage of the navicular bursa were unsuccessful in resolving the condition. Horses that were treated surgically within 1 week of the injury and had a hind leg affected had the best chance of a satisfactory outcome. Additional wound debridement was necessary in 15 horses after initial surgical treatment. The most common complications encountered were navicular bone osteomyelitis and sepsis of the deep digital flexor tendon. Thirteen of 14 horses that had rupture of the deep digital flexor tendon and subluxation of the distal interphalangeal joint had an unsatisfactory outcome. One mare subsequently developed ankylosis of the distal interphalangeal joint and was a useful brood mare. Two horses that had biaxial palmar digital neurectomy because of persistent lameness were later euthanized because of navicular bone fracture and rupture of the deep digital flexor tendon. Results from limited numbers of bacterial cultures and antibiotic sensitivities suggest that penicillin and an aminoglycoside antibiotic should be used as initial antibiotic therapy. Immediate surgical debridement and appropriate antibiotic treatment are recommended as the minimum therapy for penetrating wounds of the navicular bursa in horses.  相似文献   
65.
Images with high resolution and exceptionally broad gray scale can be obtained by the application of video contrast enhancement to an optimized procedure for imaging transparent objects with oblique rays of illumination. This technique is simple to set up. A conventional microscope with a light source whose position can be adjusted and a video camera with controls for gain and black level are the only essential components. Features such as high resolution, optical sectioning, control of contrast, and operation under low light intensity make this technique preferable, in several instances, to currently used video microscopy techniques.  相似文献   
66.
Characterization of monoclonal antibodies directed against swine leukocytes   总被引:3,自引:0,他引:3  
Hybridomas were produced from fusions of the SP2/0 mouse myeloma with splenic cells from: 1) an outbred Sprague Dawley rat immunized with swine peripheral blood mononuclear (PBM) cells; 2) a (CBA/NDub X BALB/c Dub) F1 mouse immunized with concanavalin A (Con A) activated swine PBM cells and 3) a (BALB/c Dub X C3H/He Dub) F1 mouse immunized with swine thymocytes. The resulting supernatants were screened by a microcytotoxicity assay for activity against swine PBM cells. Four hybridomas (MSA1, MSA2, MSA3 and MSA4) were selected, cloned and characterized by their cell reactivity and effect on mitogenic assays. MSA1 and MSA2 belong to the rat IgG2b subclass. MSA3 and MSA4 are of the mouse IgG2a subclass. These monoclonal antibodies reacted in the following manner: MSA1 with monocytes, granulocytes, red blood cells and bone marrow cells; MSA2 with subset of T cells; MSA3 with B cells and subsets of T cells and monocytes (class II molecule) and MSA4, a pan-T cell reagent (E-rosette receptor). The involvement of the various cell types reactive to the different monoclonal antibodies in the mitogenic response of swine PBM cells to Con A, phytohemagglutinin (PHA) or pokeweed mitogen (PWM) was investigated by cellular depletion with monoclonal antibody plus complement. Cellular depletion of PBM cells with the following monoclonal antibodies plus complement treatment resulted in: MSA1, almost total reduction in the mitogenic response to low doses of Con A or PWM; MSA2, partial reduction in the proliferative responses to any concentration of Con A, PHA or PWM; MSA3, partial reduction in proliferative responses to low concentrations of Con A or PWM and 4) MSA4, total elimination of any proliferative response to Con A, PHA or PWM.  相似文献   
67.
Washed and unwashed red blood cells (RBC) from young calves, adult cattle, hamsters and humans were incubated with Leptospira interrogans serovars pomona and ballum. Washed cells suspended in saline were always haemolysed while unwashed cells and those which were washed and resuspended in plasma were never haemolysed, despite the presence of large numbers of organisms within the culture supernatant. Pomona produced greater haemolysis of cattle and human RBC than did ballum, but with hamster RBC ballum produced greater haemolysis than did pomona. A group of 6- to 9-month-old cattle infected with pomona showed no signs of clinical disease and RBC taken from them before infection and during the development of antibodies to pomona were haemolysed by pomona only after the cells were washed. Plasma therefore appears to have a protective function. This in vitro protective function of plasma even extended to plasma from young seronegative calves.  相似文献   
68.
69.
70.
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