全文获取类型
收费全文 | 19074篇 |
免费 | 1653篇 |
国内免费 | 1篇 |
专业分类
20728篇 |
出版年
2023年 | 78篇 |
2021年 | 156篇 |
2020年 | 115篇 |
2019年 | 136篇 |
2018年 | 361篇 |
2017年 | 375篇 |
2016年 | 406篇 |
2015年 | 336篇 |
2014年 | 450篇 |
2013年 | 708篇 |
2012年 | 1319篇 |
2011年 | 1435篇 |
2010年 | 753篇 |
2009年 | 500篇 |
2008年 | 1213篇 |
2007年 | 1214篇 |
2006年 | 1147篇 |
2005年 | 1036篇 |
2004年 | 988篇 |
2003年 | 941篇 |
2002年 | 924篇 |
2001年 | 776篇 |
2000年 | 894篇 |
1999年 | 407篇 |
1998年 | 191篇 |
1997年 | 139篇 |
1996年 | 178篇 |
1995年 | 162篇 |
1994年 | 141篇 |
1993年 | 144篇 |
1992年 | 135篇 |
1991年 | 128篇 |
1990年 | 126篇 |
1989年 | 116篇 |
1988年 | 129篇 |
1987年 | 129篇 |
1986年 | 112篇 |
1985年 | 149篇 |
1984年 | 146篇 |
1983年 | 124篇 |
1982年 | 160篇 |
1981年 | 146篇 |
1980年 | 112篇 |
1979年 | 126篇 |
1978年 | 97篇 |
1977年 | 91篇 |
1976年 | 82篇 |
1975年 | 80篇 |
1974年 | 81篇 |
1973年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
H Härtel S Nikunen E Neuvonen R Tanskanen S-L Kivelä P Aho T Soveri H Saloniemi 《Acta veterinaria Scandinavica》2004,45(4):193-200
Pathogens causing bovine respiratory tract disease in Finland were investigated. Eighteen cattle herds with bovine respiratory
disease were included. Five diseased calves from each farm were chosen for closer examination and tracheobronchial lavage.
Blood samples were taken from the calves at the time of the investigation and from 86 calves 3–4 weeks later. In addition,
6–10 blood samples from animals of different ages were collected from each herd, resulting in 169 samples. Serum samples were
tested for antibodies to bovine parainfluenza virus-3 (PIV-3), bovine respiratory syncytial virus (BRSV), bovine coronavirus
(BCV), bovine adenovirus-3 (BAV-3) and bovine adenovirus-7 (BAV-7). About one third of the samples were also tested for antibodies
to bovine virus diarrhoea virus (BVDV) with negative results. Bacteria were cultured from lavage fluid and in vitro susceptibility
to selected antimicrobials was tested. According to serological findings, PIV-3, BAV-7, BAV-3, BCV and BRSV are common pathogens
in Finnish cattle with respiratory problems. A titre rise especially for BAV-7 and BAV-3, the dual growth of Mycoplasma dispar and Pasteurella multocida, were typical findings in diseased calves. Pasteurella sp. strains showed no resistance to tested antimicrobials. Mycoplasma bovis and Mannheimia haemolytica were not found. 相似文献
22.
23.
Planar cell polarity (PCP) controls the orientation of cells within tissues and the polarized outgrowth of cellular appendages. So far, six PCP core proteins including the transmembrane proteins Frizzled (Fz), Strabismus (Stbm) and Flamingo (Fmi) have been identified. These proteins form asymmetric PCP domains at apical junctions of epithelial cells. Here, we demonstrate that VhaPRR, an accessory subunit of the proton pump V‐ATPase, directly interacts with the protocadherin Fmi through its extracellular domain. It also shows a striking co‐localization with PCP proteins during all pupal wing stages in Drosophila. This localization depends on intact PCP domains. Reversely, VhaPRR is required for stable PCP domains, identifying it as a novel PCP core protein. VhaPRR performs an additional role in vesicular acidification as well as endolysosomal sorting and degradation. Membrane proteins, such as E‐Cadherin and the Notch receptor, accumulate at the surface and in intracellular vesicles of cells mutant for VhaPRR. This trafficking defect is shared by other V‐ATPase subunits. By contrast, the V‐ATPase does not seem to have a direct role in PCP regulation. Together, our results suggest two roles for VhaPRR, one for PCP and another in endosomal trafficking. This dual function establishes VhaPRR as a key factor in epithelial morphogenesis. 相似文献
24.
25.
Jonas G. Barlind Linda K. Buckett Sharon G. Crosby Öjvind Davidsson Hans Emtenäs Anne Ertan Ulrik Jurva Malin Lemurell Pablo Morentin Gutierrez Karolina Nilsson Gavin O’Mahony Annika U. Petersson Alma Redzic Fredrik Wågberg Zhong-Qing Yuan 《Bioorganic & medicinal chemistry letters》2013,23(9):2721-2726
[Acyl CoA]monoacylglycerol acyltransferase 2 (MGAT2) is of interest as a target for therapeutic treatment of diabetes, obesity and other diseases which together constitute the metabolic syndrome. In this Letter we report our discovery and optimisation of a novel series of MGAT2 inhibitors. The development of the SAR of the series and a detailed discussion around some key parameters monitored and addressed during the lead generation phase will be given. The in vivo results from an oral lipid tolerance test (OLTT) using the MGAT2 inhibitor (S)-10, shows a significant reduction (68% inhibition relative to na?ve, p <0.01) in plasma triacylglycerol (TAG) concentration. 相似文献
26.
Estimating the extent of biological invasions is critical in predicting the effect of exotic species. We investigated the occurrence and number of alien freshwater plants and give information on the composition of alien aquatic flora, their trend in time, invasion pathway, and their invasive character. 相似文献
27.
Acetobacter acetii DSMZ3508 and related bacteria converted 2,2-dimethyl-1,3-propanediol into 3-hydroxypivalic acid (2,2-dimethyl-3-hydroxypropionic acid; 3HP) during submerged cultivation in mineral salt medium. The maximum yield of 3-hydroxypivalic acid was 24.4% of the fed substrate after 18 days. Cultivation parameters, as pH, cell density, optimal substrate concentration, and oxygen supply for the bioconversion process were determined. 相似文献
28.
29.
30.
Cerebellum Gangliosides in Postnatal Rats 总被引:1,自引:1,他引:0
Sneana R. Vrbaki 《Journal of neurochemistry》1980,34(4):1032-1033