全文获取类型
收费全文 | 295篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
林业 | 3篇 |
农学 | 2篇 |
48篇 | |
综合类 | 65篇 |
农作物 | 8篇 |
畜牧兽医 | 187篇 |
园艺 | 2篇 |
植物保护 | 8篇 |
出版年
2023年 | 2篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 11篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 17篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 16篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 19篇 |
2005年 | 13篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1966年 | 2篇 |
1945年 | 3篇 |
1941年 | 2篇 |
1929年 | 2篇 |
1917年 | 2篇 |
1913年 | 1篇 |
1912年 | 2篇 |
1911年 | 3篇 |
1906年 | 1篇 |
排序方式: 共有323条查询结果,搜索用时 203 毫秒
91.
92.
93.
Tanaka S Kerfeld CA Sawaya MR Cai F Heinhorst S Cannon GC Yeates TO 《Science (New York, N.Y.)》2008,319(5866):1083-1086
The carboxysome is a bacterial microcompartment that functions as a simple organelle by sequestering enzymes involved in carbon fixation. The carboxysome shell is roughly 800 to 1400 angstroms in diameter and is assembled from several thousand protein subunits. Previous studies have revealed the three-dimensional structures of hexameric carboxysome shell proteins, which self-assemble into molecular layers that most likely constitute the facets of the polyhedral shell. Here, we report the three-dimensional structures of two proteins of previously unknown function, CcmL and OrfA (or CsoS4A), from the two known classes of carboxysomes, at resolutions of 2.4 and 2.15 angstroms. Both proteins assemble to form pentameric structures whose size and shape are compatible with formation of vertices in an icosahedral shell. Combining these pentamers with the hexamers previously elucidated gives two plausible, preliminary atomic models for the carboxysome shell. 相似文献
94.
95.
96.
97.
The dot enzyme-linked immunosorbent assay (Dot-ELISA), standard ELISA and the complement fixation (CF) tests were compared in the serodiagnosis of African visceral leishmaniasis (kala-azar). Assay sensitivity was determined using sera from 44 patients with parasitologically confirmed kala-azar. Using the Dot-ELISA, 42 of 44 patients (95%) were positive at a reciprocal titer of greater than or equal to 32 (titer range 512-524 288). In the standard ELISA technique, 43 of 44 patients (98%) were positive (titer range 32-32 768). At a reciprocal titer of greater than or equal to 8 in the CF test, 35 patients (80%) were positive, 1 (2%) was negative and 8 patients (18%) showed anticomplementary (AC) activity (titer range 8-2048). Specificity, determined using 33 sera from healthy individuals not living in endemic areas, was 97% in both the Dot-ELISA and the standard ELISA (32 of 33 sera); in he CF test, all sera were negative except 1 (3%) which showed AC activity. Sera from patients with Chagas' disease cross-reacted in the dot-ELISA up to a titer of 512. In the standard ELISA, cross-reactions occurred mainly using sera from patients with Chagas' disease, malaria and syphilis, and to a lesser extent with sera from amebiasis, schistosomiasis and trichinosis patients. Overall titer agreement in replicate experiments was highest in the Dot-ELISA (89%), followed by the standard ELISA (80%) and the CF test (72%). 相似文献
98.
A computer program was devised to extract information about the fertility of bulls from a bovine reproduction data bank used in a dairy herd health program. The data necessary for the analysis was already stored in the data bank so that the cost of performing the calculation arose from the writing of the program, and the subsequent computer time required to run it. 相似文献
99.
Giancarlo Pizza Paul H Levine Dharam V Ablashi Gary Armstrong Zakir Bengali Grace B Cannon 《Comparative immunology, microbiology and infectious diseases》1982,5(4):437-446
Humoral and cell-mediated immunity (CMI) to herpesvirus saimiri (HVS), an oncogenic lymphotropic herpesvirus, was studied in squirrel and rhesus monkeys. Natural antibody to HVS was found in five of six squirrel monkeys but there was no evidence of specific CMI directed against HVS. Rhesus monkeys did not show natural antibody or CMI against HVS antigens. Immunization with HVS, however, produced both antibody and specific CMI in the rhesus monkeys, but no CMI developed in the squirrel monkeys. These findings are important in the development of animal models for the treatment of tumors associated with lymphotropic herpesviruses. 相似文献
100.
Serum and Tissue Steroid Hormone Levels in Canine Mammary Tumours: Clinical and Prognostic Implications
下载免费PDF全文
![点击此处可从《Reproduction in domestic animals》网站下载免费的PDF全文](/ch/ext_images/free.gif)
FL Queiroga D Pérez‐Alenza A González‐Gil G Silván L Peña JC Illera 《Reproduction in domestic animals》2015,50(5):858-865
Hormonal dependency of canine mammary tumours (CMT) has been studied over the last few decades. However, studies assessing the prognostic and predictive potential of serum and/or tissue steroid hormone levels are still scarce in CMT. To the best of our knowledge, this is the first report relating serum and tissue levels of steroid hormones and prognosis in dogs. Serum and tumour tissue from 45 female dogs with spontaneous CMT were included in the study. Moreover, serum and normal mammary tissue from 13 healthy female dogs were also included as controls. Steroid hormones were determined by competitive enzyme immunoassay. Overall, levels of steroid hormones in serum and tissue homogenates were significantly different between malignant and benign mammary tumours (p < 0.01), except for progesterone (P4) serum levels that revealed no statistical differences between groups. In malignant tumours, oestrone sulphate (SO4E1), dehydroepiandrosterone (DHEA), androstenedione (A4), testosterone (T) and P4 elevated tissue concentrations were significantly associated with tumour relapse and/or distant metastasis during follow‐up. A significant association was found between elevated tissue SO4E1 (p = 0.003), 17β‐oestradiol (E2) (p = 0.036), DHEA (p = 0.022), A4 (p = 0.001) and P4 (p = 0.013) concentrations and shorter disease‐free survival and overall survival in female dogs with malignant mammary tumours. The high levels of tissue steroids found in cases of poor prognosis open the possibility of additional new therapeutic approaches. Future clinical trials will be needed to clarify the usefulness of targeting steroid hormones in the treatment of this neoplastic disease. 相似文献