全文获取类型
收费全文 | 109006篇 |
免费 | 1122篇 |
国内免费 | 901篇 |
专业分类
111029篇 |
出版年
2023年 | 121篇 |
2022年 | 293篇 |
2021年 | 460篇 |
2020年 | 266篇 |
2019年 | 280篇 |
2018年 | 12118篇 |
2017年 | 10931篇 |
2016年 | 7874篇 |
2015年 | 1314篇 |
2014年 | 1089篇 |
2013年 | 1418篇 |
2012年 | 5410篇 |
2011年 | 13796篇 |
2010年 | 12568篇 |
2009年 | 8753篇 |
2008年 | 10404篇 |
2007年 | 11973篇 |
2006年 | 868篇 |
2005年 | 1028篇 |
2004年 | 1447篇 |
2003年 | 1422篇 |
2002年 | 1146篇 |
2001年 | 593篇 |
2000年 | 471篇 |
1999年 | 273篇 |
1998年 | 137篇 |
1997年 | 127篇 |
1996年 | 108篇 |
1995年 | 115篇 |
1994年 | 110篇 |
1993年 | 126篇 |
1992年 | 244篇 |
1991年 | 245篇 |
1990年 | 208篇 |
1989年 | 201篇 |
1988年 | 185篇 |
1987年 | 177篇 |
1986年 | 151篇 |
1985年 | 176篇 |
1984年 | 175篇 |
1983年 | 132篇 |
1982年 | 115篇 |
1981年 | 100篇 |
1980年 | 94篇 |
1979年 | 147篇 |
1978年 | 110篇 |
1977年 | 95篇 |
1974年 | 118篇 |
1972年 | 346篇 |
1971年 | 357篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Siddhartha Kumar Bhaumik Manoj Kumar Singh Subir Karmakar Tripti De 《Glycoconjugate journal》2009,26(6):663-673
As compared to cutaneous leishmaniasis, vaccination against visceral leishmaniasis (VL) has received limited attention. In
this study, we demonstrate for the first time that an UDP-Galactose: N-acetylglucosamine β 1–4 galactosyltransferase (GenBank Accession No. EF159943) expressing attenuated LD clonal population (A-LD) is able to confer protection against the experimental challenge with the virulent LD AG83 parasite. A-LD was also effective in established leishmania infection. The vaccinated animals showed both cell mediated
(in vitro T-cell proliferation, and DTH response) and humoral responses (Th1 type). These results demonstrate the potential of the
attenuated clones as an immunotherapeutic and immunoprophylactic agent against visceral leishmaniasis. 相似文献
63.
M Singh 《Life sciences》1980,26(9):715-724
The present study was designed to determine the effect of vitamin B6 deficiency on pancreatic acinar cell function. Rats were either fed or rendered B6-deficient by a purified B6-deficient diet; half of the latter being replenished with IP pyridoxine before sacrifice. Body weight, pancreatic weight, RNA and DNA content were decreased in B6-deficient animals. These changes were considered to be due to inanition resulting from decreased food intake. Amylase content of pancreas in B6-deficient animals was less compared with B6-replenished animals. Although slightly higher in B6-deficient animals, the incorporation of L-phenylalanine14C into total tissue proteins was not significantly different in the three groups of animals. On B6-replenishment, incorporation of L-phenylalanine14C into nascent proteins was diminished in spite of higher tissue amylase and protein content. Vitamin B6 deficiency decreased total RNA content and adenine-8-14C incorporation into RNA. DNA content was diminished but incorporation of thymidine-2-14C into DNA was increased. On replenishment with B6, thymidine-2-14C incorporation decreased significantly compared to control animals. Secretion of amylase was diminished commensurate with decreased content. It is concluded from these studies that B6-deficiency induced DNA injury, decreased RNA turnover and increased protein turnover resulting in diminished amylase content. These data indicate that B6-deficiency so frequently encountered in alcoholism may contribute to the pancreatic injury in this clinical condition. 相似文献
64.
65.
66.
67.
Shallow-water vegetated estuarine habitats, notably seagrass, mangrove and saltmarsh, are known to be important habitats for
many species of small or juvenile fish in temperate Australia. However, the movement of fish between these habitats is poorly
understood, and yet critical to the management of the estuarine fisheries resource. We installed a series of buoyant pop nets
in adjacent stands of seagrass, mangrove and saltmarsh in order to determine how relative abundance of fishes varied through
lunar cycles. Nets were released in all habitats at the peak of the monthly spring tide for 12 months, and in the seagrass
habitat at the peak of the neap tide also. The assemblage of fish in each habitat differed during the spring tides. The seagrass
assemblage differed between spring and neap tide, with the neap tide assemblage showing greater abundances of fish, particularly
those species which visited the adjacent habitats when inundated during spring tides. The result supports the hypothesis that
fish move from the seagrass to the adjacent mangrove and saltmarsh during spring tides, taking advantage of high abundances
of zooplankton, and use seagrass as a refuge during lower tides. The restoration and preservation of mangrove and saltmarsh
utility as fish habitat may in some situations be linked to the proximity of available seagrass. 相似文献
68.
69.
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
70.