全文获取类型
收费全文 | 103490篇 |
免费 | 1493篇 |
国内免费 | 887篇 |
专业分类
105870篇 |
出版年
2023年 | 74篇 |
2022年 | 132篇 |
2021年 | 291篇 |
2020年 | 140篇 |
2019年 | 196篇 |
2018年 | 12015篇 |
2017年 | 10833篇 |
2016年 | 7730篇 |
2015年 | 1105篇 |
2014年 | 855篇 |
2013年 | 927篇 |
2012年 | 4997篇 |
2011年 | 13530篇 |
2010年 | 12412篇 |
2009年 | 8557篇 |
2008年 | 10268篇 |
2007年 | 11839篇 |
2006年 | 687篇 |
2005年 | 909篇 |
2004年 | 1344篇 |
2003年 | 1392篇 |
2002年 | 1142篇 |
2001年 | 473篇 |
2000年 | 400篇 |
1999年 | 233篇 |
1998年 | 118篇 |
1997年 | 116篇 |
1996年 | 95篇 |
1995年 | 64篇 |
1994年 | 90篇 |
1993年 | 100篇 |
1992年 | 171篇 |
1991年 | 162篇 |
1990年 | 136篇 |
1989年 | 123篇 |
1988年 | 128篇 |
1987年 | 120篇 |
1986年 | 89篇 |
1985年 | 100篇 |
1984年 | 84篇 |
1983年 | 81篇 |
1982年 | 63篇 |
1981年 | 72篇 |
1980年 | 72篇 |
1979年 | 84篇 |
1977年 | 65篇 |
1975年 | 76篇 |
1974年 | 71篇 |
1972年 | 295篇 |
1971年 | 319篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
Spectral changes accompanying the binding of the nonionic detergent n-octyl beta-D-glucopyranoside (n-octyl glucoside) to cytochrome P-450LM2 purified from liver microsomes of phenobarbital-treated rabbits have been compared to changes in catalytic activity obtained in a reconstituted system consisting of various levels of detergent, P-450LM2, and NADPH-cytochrome P-450 reductase. In the absence of substrate and reductase, addition of n-octyl glucoside to 2-3 mM resulted in a difference spectrum (detergent-bound minus detergent-free cytochrome) characterized by a small maximum at 390 nm and a minimum at 410 nm, suggestive of a slight stabilization of the high-spin (S = 5/2) state of the cytochrome. As the detergent concentration was increased to 4-8 mM (corresponding to maximal activity and pentameric or hexameric P-450), a new peak appeared at 427 nm while the minimum remained at 410 nm. Between 10 and 30 mM n-octyl glucoside (conditions which produced catalytically inactive and monomeric P-450) the minimum in the difference spectrum shifted to 390 nm and the maximum to 425 nm, characteristic of a shift in spin equilibrium toward low-spin (S = 1/2) cytochrome. At low and high detergent concentrations, substrate [d-benzphetamine with n-octyl glucoside or cyclohexane with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS)] was bound to P-450LM2 with formation of high-spin P-450, although the increase in high-spin cytochrome was less at high detergent levels than at low. The affinity of P-450 for substrate decreased by 2-3-fold at high detergent.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
55.
56.
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
57.
Aurel Popa Wagner Eugenia Psarrou Lieselotte Popa Wagner 《Analytical biochemistry》1983,129(2):326-328
A simple and sensitive high-performance liquid chromatography method with electrochemical detector is described for the determination of free 3-methoxy-4-hydroxyphenylacetic acid (HVA) in human plasma. The method does not involve any extraction, is specific and reproducible, and has the potential to measure serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) simultaneously. The plasma concentration of free HVA in eight normal, healthy adult volunteers was 10.9 ± 4.6 (mean ± SD). In a preliminary study, in one schizophrenic patient the plasma HVA increased twofold after neuroleptic treatment. 相似文献
58.
59.
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
60.