全文获取类型
收费全文 | 5564篇 |
免费 | 530篇 |
国内免费 | 5篇 |
专业分类
6099篇 |
出版年
2023年 | 32篇 |
2022年 | 63篇 |
2021年 | 144篇 |
2020年 | 87篇 |
2019年 | 109篇 |
2018年 | 148篇 |
2017年 | 119篇 |
2016年 | 212篇 |
2015年 | 293篇 |
2014年 | 343篇 |
2013年 | 372篇 |
2012年 | 513篇 |
2011年 | 510篇 |
2010年 | 301篇 |
2009年 | 266篇 |
2008年 | 363篇 |
2007年 | 358篇 |
2006年 | 326篇 |
2005年 | 258篇 |
2004年 | 277篇 |
2003年 | 217篇 |
2002年 | 239篇 |
2001年 | 58篇 |
2000年 | 51篇 |
1999年 | 46篇 |
1998年 | 63篇 |
1997年 | 37篇 |
1996年 | 31篇 |
1995年 | 30篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 24篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 16篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1971年 | 4篇 |
排序方式: 共有6099条查询结果,搜索用时 15 毫秒
31.
Yuan Yan Sin Laurel L. Ballantyne Kamalika Mukherjee Tim St. Amand Lianna Kyriakopoulou Andreas Schulze Colin D. Funk 《PloS one》2013,8(11)
Arginase deficiency is a rare autosomal recessive disorder resulting from a loss of the liver arginase isoform, arginase 1 (ARG1), which is the final step in the urea cycle for detoxifying ammonia. ARG1 deficiency leads to hyperargininemia, characterized by progressive neurological impairment, persistent growth retardation and infrequent episodes of hyperammonemia. Using the Cre/loxP-directed conditional gene knockout system, we generated an inducible Arg1-deficient mouse model by crossing “floxed” Arg1 mice with CreERT2 mice. The resulting mice (Arg-Cre) die about two weeks after tamoxifen administration regardless of the starting age of inducing the knockout. These treated mice were nearly devoid of Arg1 mRNA, protein and liver arginase activity, and exhibited symptoms of hyperammonemia. Plasma amino acid analysis revealed pronounced hyperargininemia and significant alterations in amino acid and guanidino compound metabolism, including increased citrulline and guanidinoacetic acid. Despite no alteration in ornithine levels, concentrations of other amino acids such as proline and the branched-chain amino acids were reduced. In summary, we have generated and characterized an inducible Arg1-deficient mouse model exhibiting several pathologic manifestations of hyperargininemia. This model should prove useful for exploring potential treatment options of ARG1 deficiency. 相似文献
32.
Benjamin F. Kaluza Helen Wallace Tim A. Heard Alexandra‐Maria Klein Sara D. Leonhardt 《Ecology and evolution》2016,6(5):1304-1316
Increasing human land use for agriculture and housing leads to the loss of natural habitat and to widespread declines in wild bees. Bee foraging dynamics and fitness depend on the availability of resources in the surrounding landscape, but how precisely landscape related resource differences affect bee foraging patterns remains unclear. To investigate how landscape and its interaction with season and weather drive foraging and resource intake in social bees, we experimentally compared foraging activity, the allocation of foragers to different resources (pollen, nectar, and resin) and overall resource intake in the Australian stingless bee Tetragonula carbonaria (Apidae, Meliponini). Bee colonies were monitored in different seasons over two years. We compared foraging patterns and resource intake between the bees'' natural habitat (forests) and two landscapes differently altered by humans (suburban gardens and agricultural macadamia plantations). We found foraging activity as well as pollen and nectar forager numbers to be highest in suburban gardens, intermediate in forests and low in plantations. Foraging patterns further differed between seasons, but seasonal variations strongly differed between landscapes. Sugar and pollen intake was low in plantations, but contrary with our predictions, it was even higher in gardens than in forests. In contrast, resin intake was similar across landscapes. Consequently, differences in resource availability between natural and altered landscapes strongly affect foraging patterns and thus resource intake in social bees. While agricultural monocultures largely reduce foraging success, suburban gardens can increase resource intake well above rates found in natural habitats of bees, indicating that human activities can both decrease and increase the availability of resources in a landscape and thus reduce or enhance bee fitness. 相似文献
33.
34.
Ye Zhu Maximilian Blum Uwe Hoff Tim Wesser Mandy Fechner Christina Westphal Dennis Gürgen Rusan Ali Catar Aurelie Philippe Kaiyin Wu Gordana Bubalo Michael Rothe Steven M. Weldon Duska Dragun Wolf-Hagen Schunck 《PloS one》2016,11(1)
Aim
20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) are cytochrome P450 (CYP)-dependent eicosanoids that play opposite roles in the regulation of vascular tone, inflammation, and apoptosis. 20-HETE aggravates, whereas EETs ameliorate ischemia/reperfusion (I/R)-induced organ damage. EETs are rapidly metabolized to dihydroxyeicosatrienoic acids (DHETs) by the soluble epoxide hydrolase (sEH). We hypothesized that sEH gene (EPHX2) deletion would increase endogenous EET levels and thereby protect against I/R-induced acute kidney injury (AKI).Methods
Kidney damage was evaluated in male wildtype (WT) and sEH-knockout (KO)-mice that underwent 22-min renal ischemia followed by two days of reperfusion. CYP-eicosanoids were analyzed by liquid chromatography tandem mass spectrometry.Results
Contrary to our initial hypothesis, renal function declined more severely in sEH-KO mice as indicated by higher serum creatinine and urea levels. The sEH-KO-mice also featured stronger tubular lesion scores, tubular apoptosis, and inflammatory cell infiltration. Plasma and renal EET/DHET-ratios were higher in sEH-KO than WT mice, thus confirming the expected metabolic consequences of sEH deficiency. However, CYP-eicosanoid profiling also revealed that renal, but not plasma and hepatic, 20-HETE levels were significantly increased in sEH-KO compared to WT mice. In line with this finding, renal expression of Cyp4a12a, the murine 20-HETE-generating CYP-enzyme, was up-regulated both at the mRNA and protein level, and Cyp4a12a immunostaining was more intense in the renal arterioles of sEH-KO compared with WT mice.Conclusion
These results indicate that the potential beneficial effects of reducing EET degradation were obliterated by a thus far unknown mechanism leading to kidney-specific up-regulation of 20-HETE formation in sEH-KO-mice. 相似文献35.
36.
37.
Santini Nadia S. Lovelock Catherine E. Hua Quan Zawadzki Atun Mazumder Debashish Mercer Tim R. Muñoz-Rojas Miriam Hardwick Simon A. Madala Bindu Swapna Cornwell William Thomas Torsten Marzinelli Ezequiel M. Adam Paul Paul Swapan Vergés Adriana 《Ecosystems》2019,22(8):1803-1822
Ecosystems - Saltmarshes provide many valuable ecosystem services including storage of a large amount of ‘blue carbon’ within their soils. To date, up to 50% of the world’s... 相似文献
38.
39.
40.
Journal of Insect Conservation - 相似文献