全文获取类型
收费全文 | 54067篇 |
免费 | 2959篇 |
国内免费 | 4341篇 |
专业分类
林业 | 5636篇 |
农学 | 6985篇 |
基础科学 | 3372篇 |
8616篇 | |
综合类 | 13281篇 |
农作物 | 3050篇 |
水产渔业 | 2623篇 |
畜牧兽医 | 12109篇 |
园艺 | 1651篇 |
植物保护 | 4044篇 |
出版年
2024年 | 116篇 |
2023年 | 457篇 |
2022年 | 1161篇 |
2021年 | 1674篇 |
2020年 | 1507篇 |
2019年 | 1631篇 |
2018年 | 1307篇 |
2017年 | 1601篇 |
2016年 | 1542篇 |
2015年 | 1996篇 |
2014年 | 1882篇 |
2013年 | 2601篇 |
2012年 | 2773篇 |
2011年 | 3077篇 |
2010年 | 2804篇 |
2009年 | 2757篇 |
2008年 | 2739篇 |
2007年 | 2855篇 |
2006年 | 2532篇 |
2005年 | 2613篇 |
2004年 | 1376篇 |
2003年 | 1286篇 |
2002年 | 1071篇 |
2001年 | 1534篇 |
2000年 | 1608篇 |
1999年 | 1854篇 |
1998年 | 1245篇 |
1997年 | 1090篇 |
1996年 | 1022篇 |
1995年 | 940篇 |
1994年 | 890篇 |
1993年 | 842篇 |
1992年 | 904篇 |
1991年 | 864篇 |
1990年 | 714篇 |
1989年 | 618篇 |
1988年 | 540篇 |
1987年 | 482篇 |
1986年 | 374篇 |
1985年 | 270篇 |
1984年 | 218篇 |
1983年 | 186篇 |
1982年 | 135篇 |
1981年 | 137篇 |
1980年 | 108篇 |
1979年 | 160篇 |
1978年 | 103篇 |
1977年 | 75篇 |
1975年 | 83篇 |
1974年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
H K Pradhan G C Mohanty W Y Lee B Patnaik 《Veterinary immunology and immunopathology》1991,29(3-4):229-238
Antibody directed against Marek's disease-associated tumor surface antigen (MATSA) was eluted from tumor cells of lymphomas and peripheral blood lymphocytes that were isolated from Marek's disease virus-infected chickens. Feather follicular Marek's disease virus (MDV) antigen could not be demonstrated with this antibody by indirect immunofluorescent (IF) staining. Monoclonal antibody directed against MATSA could completely block the activity of eluted antibody and vice versa. By indirect IF staining using eluted antibody and fluorescein isothiocyanate (FITC) labelled antichicken globulin conjugate. MATSA-bearing cells were detected in MDV infected and herpes virus of turkey (HVT) vaccinated birds. Blocking of immunoglobulin molecules present on B-cells by anti-chicken globulin is critical in this test. 相似文献
162.
163.
综述影响啤酒大麦种子发芽整齐度的因素 ,着重介绍了品种、籽粒整齐度 (包括粒重和粒位 )对发芽整齐度的影响 ,旨在为培育优质啤酒大麦提供借鉴。 相似文献
164.
对偏调谐类单调谐滤波器提出了非线性的束优化模型,运用大系统理论协调优化单调谐滤波器和高通滤波器,实例计算表明,该方法是对以往单调谐滤波器设计计算方法的一大改进。 相似文献
165.
166.
Y Takahashi M Iida Y Nishida Y Kido 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1989,51(5):995-1001
Eight calves, weighing 50-150 kg, were given intramuscularly 5 ml of ampicillin (ABPC) aqueous suspensions (200 mg potency/ml) in their right and left gluteal and femoral regions. All calves were sacrificed one hour later to confirm the location of injected drug. The drug was found in a muscle layer when injected with a needle 15 mm long to the following positions, 1. the midpoint between the central position of the gluteal region (CG) and the tuber coxae (M-CTc), 2. the midpoint between CG and the tuber ossis ischii (M-CTo), 3. the central position of M. semimembranaceus in the femoral region (CF). Seven calves, weighing 130-150 kg, were given intramuscularly 5 ml of ABPC suspensions at M-CTo and CF and sacrificed one hour (4 calves) and 3 days (3 calves) later. ABPC diffused along the long axis of the muscle fibers but not to the radial direction. ABPC was detected only in the injected muscle layer even after 3 days indicating that the drug did not diffuse to the neighboring muscles. In the injected muscle layer, concentration of ABPC was remarkably different from part to part. From these results, sampling of the injected muscle for the drug residue study was proposed as follows: 1. isolate about 100 g of muscle just under the stick point marked on the skin considering the direction of drug diffusion, and 2. isolate separately about 200 g of the surrounding muscle to confirm if the sampling is appropriate. 相似文献
167.
Cellular injury and lipid peroxidation induced by hexavalent chromium in isolated rat hepatocytes 总被引:1,自引:0,他引:1
S Ueno N Susa Y Furukawa K Aikawa I Itagaki 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1989,51(1):137-145
In order to elucidate the relationship between cellular injury and lipid peroxidation induced by hexavalent chromium (CrVI), isolated rat hepatocytes treated with any one of scavengers of active oxygen species, antioxidants or antichromium agent were incubated with K2Cr2O7 as CrVI (1 mM Cr). After the incubation, the development of lipid peroxidation was determined as thiobarbituric acid (TBA)-reacting materials in total lipid extracts from the incubated hepatocytes. Cellular injury was observed as a leakage of lactate dehydrogenase (LDH) from hepatocytes into incubation medium. The contents of reduced glutathione (GSH) in hepatocytes were also assessed. Results obtained were as follows: (1) CrVI facilitated lipid peroxidation in isolated hepatocytes after 20 min of incubation. On the other hand, the cellular injury induced by CrVI was barely observed even after 60 min of incubation. (2) The CrVI-induced lipid peroxidation was inhibited by catalase and mannitol as scavengers of active oxygen species, or N,N'-diphenyl-p-phenylenediamine and alpha-tocopherol as antioxidants. However the cytotoxicity of CrVI could not be prevented by these chemicals. (3) CrVI depleted the contents of intracellular GSH and diminished the activities of glutathione reductase (GR) and glutathione-S-transferase (GST) except glutathione peroxidase. (4) The scavengers of active oxygen species and the antioxidants could not prevent the depletion of intracellular GSH induced by CrVI. (6) Ascorbic acid, antichromium agent, prevented all of the lipid peroxidation, the cellular injury and intracellular GSH depletion induced by CrVI.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
168.
169.
170.
Distribution of Cytochrome P450-side Chain Cleavage in the Theca Interna Layers of Bovine Small Antral and Cystic Follicles 总被引:1,自引:0,他引:1
Cystic follicle is anovulatory follicular structure that is caused by an endocrine imbalance. The activity of cytochrome P450‐side chain cleavage (P450scc) is essential for the initiation of steroidogenesis in the follicle. The present study was designed to compare the frequency of cells containing P450scc between healthy and atretic small antral follicles, and among several types (I, II and III, classified based on the presence of granulosa layer) of cystic follicles. Paraffin sections of healthy (2–5 mm in diameter), atretic (2–5 mm) and cystic follicles (>25 mm) were immunohistochemically stained with rabbit polyclonal antibody to bovine P450scc. The P450scc‐positive cells were counted in four different regions of the follicles from the apical to the basal side. In small antral follicles and cystic follicles, P450scc‐positive cells were localized in the theca interna layers but not granulosa layers. The P450scc‐positive cell populations decreased in the late atretic follicles compared with the early and advanced atretic follicles at all the regions of follicle. Type III cystic follicles showed significantly lower frequencies of P450scc‐positive cells than those in the types I and II cystic follicles. These results suggest that in both small and cystic follicles in cows, total loss of granulosa cells may be associated with the reduction of frequency of P450scc‐positive cells in theca interna layer. 相似文献