全文获取类型
收费全文 | 144987篇 |
免费 | 7881篇 |
国内免费 | 818篇 |
专业分类
林业 | 6325篇 |
农学 | 4438篇 |
基础科学 | 1011篇 |
16447篇 | |
综合类 | 29275篇 |
农作物 | 5554篇 |
水产渔业 | 6542篇 |
畜牧兽医 | 73513篇 |
园艺 | 1868篇 |
植物保护 | 8713篇 |
出版年
2019年 | 1319篇 |
2018年 | 1995篇 |
2017年 | 2234篇 |
2016年 | 2018篇 |
2015年 | 1915篇 |
2014年 | 2187篇 |
2013年 | 5047篇 |
2012年 | 4115篇 |
2011年 | 4987篇 |
2010年 | 3352篇 |
2009年 | 3170篇 |
2008年 | 4649篇 |
2007年 | 4540篇 |
2006年 | 4153篇 |
2005年 | 3981篇 |
2004年 | 3679篇 |
2003年 | 3778篇 |
2002年 | 3538篇 |
2001年 | 4224篇 |
2000年 | 4320篇 |
1999年 | 3444篇 |
1998年 | 1368篇 |
1997年 | 1291篇 |
1995年 | 1411篇 |
1993年 | 1265篇 |
1992年 | 2755篇 |
1991年 | 2982篇 |
1990年 | 3008篇 |
1989年 | 2941篇 |
1988年 | 2716篇 |
1987年 | 2765篇 |
1986年 | 2816篇 |
1985年 | 2657篇 |
1984年 | 2243篇 |
1983年 | 1993篇 |
1982年 | 1335篇 |
1979年 | 2110篇 |
1978年 | 1667篇 |
1977年 | 1400篇 |
1976年 | 1396篇 |
1975年 | 1530篇 |
1974年 | 2042篇 |
1973年 | 2031篇 |
1972年 | 2014篇 |
1971年 | 1912篇 |
1970年 | 1810篇 |
1969年 | 1681篇 |
1968年 | 1388篇 |
1967年 | 1496篇 |
1966年 | 1388篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
The transformation of recent igneous rock occurs with participation of microorganisms associated with the deposition of iron and aluminum on their cell surface. An identity of morphological structures was found in the microorganisms in both cases, and this fact counts in favor of their similarity and wide distribution in the rock being transformed. The polymorphous acid-resisting organism identified by our studies was tentatively classified with the Metallogenium-Siderococcus group. 相似文献
72.
A ten-year-old female poodle was presented for left hindlimb lameness. Radiographically, irregular intramedullary densities of long bones (bone infarcts) and a lytic lesion in the left distal femur were detected. Two years after the first examination, the lesions in the distal femur were definitely identified as osteosarcoma and the dog was euthanized. Pathological and histological changes of the bone infarcts as well as of the osteosarcoma are described. Regarding bibliographical data, occurrence and aetiopathogenesis of osteosarcoma associated with multifocal bone infarction in man and dog are discussed. 相似文献
73.
K Miyahara T Matsumoto S Tose H Sakurai I Igarashi A Saito T Hirose N Suzuki 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(1):87-93
Spleen cells from Toxoplasma lysate antigen (TLA)-sensitized BALB/c mice showed the strong cytotoxic activity against both natural killer (NK)-sensitive cells (YAC-1 and RL male-1) and NK-insensitive cells (P-815), when incubated with TLA or recombinant human IL-2 (rhIL-2). The increment of TLA concentration in culture medium increased the cytotoxic activity. Treatment of effector cells; spleen cells from TLA-sensitized mice incubated with TLA, with anti-asialo GM1 or anti-Thy-1 plus complement inhibited the cytotoxic activity of effector cells, whereas treatment with anti-mouse Lyt-2.2 serum plus complement had no effect on the cytotoxic activity. Treatment of spleen cells from TLA-sensitized mice with anti-asialo GM1 and/or anti-Thy-1 plus complement inhibited cytotoxic activities of effector cells. These results suggested that spleen cells sensitized with TLA both in vivo and in vitro were asialo GM1 positive and Thy-1 positive, and the majority of cytotoxic cells induced by TLA were similar to lymphokine-activated killer (LAK) cells induced by IL-2. 相似文献
74.
A rapid and low cost procedure, the carbon immunoassay (CIA) test, was evaluated for the diagnosis of Toxoplasma gondii infections. Using a closely related parasite (Besnoitia jellisoni) as antigen, and homologous or heterologous immune sera, it was demonstrated by light and electron microscopy that CIA is a very reliable and specific test. As it is neither expensive nor time-consuming, it can be recommended for general and routine laboratory use. 相似文献
75.
L Várnagy 《Acta veterinaria Hungarica》1992,40(3):203-206
Fertile pheasant's eggs were treated with the insecticide Wofatox 50 EC (50% methyl-parathion) by injection technique on day 12 of the hatching period. Treatment consisted of inoculation of 0.1 ml of different concentrations of the insecticide into the air space of embryonated eggs. The following dose levels were employed: 0.00, 1.35, 13.5 and 135.0 mg/kg egg of active ingredient. Biochemical changes in the plasma were evaluated by micro (photometric) methods which rendered possible the determination of several blood plasma variables of the embryos. At the highest dose level applied, serum alkaline phosphatase (SAP) enzyme activity and inorganic P concentration of the treated embryos showed statistically differences (reduction) as compared to the control data. Macroscopic alterations were detected at necropsy. 相似文献
76.
This article reviews the capabilities of transrectal ultrasonography for determining the distribution of fluid and tissue within stallion accessory sex glands. Emphasis is placed on describing the normal ultrasonographic appearance of the accessory sex glands, excurrent ducts, and pelvic urethra of stallions during rest, after teasing, and after ejaculation and using this information to detect glandular abnormalities. 相似文献
77.
E Ogawa A Kawakami T Yagi T Amaya H Fujise R Takahashi 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(1):57-62
Oxidative damage to the membrane in canine erythrocytes with inherited high Na, K-ATPase activity (HK cells) was compared with that in normal canine cells (LK cells). When 30 mM beta-acetylphenylhydrazine (APH) was applied to HK and LK cells, lipid peroxidation and hemoglobin denaturation occurred. Lipid peroxidation determined from malondialdehyde (MDA) formation was significantly lower in HK than in LK cells so far as endogenous glutathione (GSH) concentration was maintained at appropriate levels. With the depletion of GSH, MDA formation was accelerated and difference between HK and LK cells was not significant. Denatured hemoglobin bound to the membrane protein was less in HK than in LK cells. During incubation with APH, osmotic fragility increased markedly in LK cells, while HK cells showed very little change. The amounts of total lipid, total and free cholesterol, glycolipid, phospholipid and fatty acids were essentially the same in both cell types. Fatty acid compositions showed very small differences. The membrane of HK cells thus appear to have greater protection against oxidative damage induced by APH, owing to the presence of excess GSH in HK cells. The capability of HK cells to withstand oxidative damage would not be due to differences in membrane lipid compositions. 相似文献
78.
T Sawada H Tamada T Inaba J Mori 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1992,54(5):1061-1062
The possibility of estrus prevention in the queen by the oral administration of chlormadinone acetate was examined. The animals used were 29 mature and 15 immature queens. For 16 mature females, 4-12.5 mg was given daily by mouth for 7 days every 3 months. Ten of the 16 queens given this treatment came into estrus within 4 months of the first treatment. For 28 females including the immature, 2-12.5 mg was given once a week throughout the experiment. This treatment prevented estrous activity for at least 1 year. In the queens in this study, the side effects were not observed excepting an increase in body weight during treatment. Our results showed that oral administration of this drug weekly is safe and reliable for long-range prevention of estrus in queens. 相似文献
79.
Root length of Holcus lanatus L. declined rapidly with increasing lead and zinc concentrations in nutrient solution. In all used Pb and Zn concentrations root growth of genotypes coming from a Pb-Zn mine area, was greater than that of the control, suggesting that these genotypes evolved tolerance to Pb and Zn.
Negative correlation was also observed between chlorophyll content and increased heavy metal concentrations. The greater chlorophyll content found in tolerant genotypes, in different Pb and Zn concentrations, in comparison with the control, could be served to distinguish tolerant and non-tolerant genotypes. 相似文献
Negative correlation was also observed between chlorophyll content and increased heavy metal concentrations. The greater chlorophyll content found in tolerant genotypes, in different Pb and Zn concentrations, in comparison with the control, could be served to distinguish tolerant and non-tolerant genotypes. 相似文献
80.
T R Kasari T S Taylor A N Baird E L Morris 《Journal of the American Veterinary Medical Association》1992,201(7):1053-1057
Osteolytic defects were detected radiographically in the distal sesamoid bone of a 16-month-old Bralers heifer, in the middle phalanx of a 14-month-old American Gray Brahman bull, and in the distal phalanx of a 3-year-old American Gray Brahman bull. The articular cartilage was damaged in each animal because of osteolysis or pathologic fracture. After each animal was anesthetized and positioned in lateral recumbency, the lesions were curetted and packed with cancellous bone harvested from the same animal's tuber coxae. Basic postoperative management involved stall rest and immobilization of the graft site with a fiberglass cast (42 to 79 days), after which a support bandage was used for approximately 2 weeks. Recurrence of lameness has not been observed in these animals for 60 months, 58 months, and 21 months, respectively. These cases exemplify the benefit of using an autogenous cancellous bone graft for treatment of severe osteolysis of a digit in cattle. 相似文献