全文获取类型
收费全文 | 4780篇 |
免费 | 199篇 |
国内免费 | 3篇 |
专业分类
4982篇 |
出版年
2023年 | 9篇 |
2022年 | 31篇 |
2021年 | 51篇 |
2020年 | 24篇 |
2019年 | 47篇 |
2018年 | 77篇 |
2017年 | 44篇 |
2016年 | 84篇 |
2015年 | 126篇 |
2014年 | 168篇 |
2013年 | 350篇 |
2012年 | 320篇 |
2011年 | 280篇 |
2010年 | 195篇 |
2009年 | 192篇 |
2008年 | 304篇 |
2007年 | 286篇 |
2006年 | 298篇 |
2005年 | 287篇 |
2004年 | 323篇 |
2003年 | 291篇 |
2002年 | 280篇 |
2001年 | 48篇 |
2000年 | 52篇 |
1999年 | 54篇 |
1998年 | 60篇 |
1997年 | 56篇 |
1996年 | 43篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 35篇 |
1992年 | 53篇 |
1991年 | 48篇 |
1990年 | 48篇 |
1989年 | 45篇 |
1988年 | 38篇 |
1987年 | 21篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 24篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 14篇 |
1973年 | 9篇 |
排序方式: 共有4982条查询结果,搜索用时 15 毫秒
1.
2.
3.
Multiple-sulfatase deficiency (MSD) is now considered to be heterogeneous and could be classified into three or four clinical phenotypes according to the onset of the disease: neonatal, late infantile, juvenile and possibly adult type. Neonatal-type MSD shows severe clinical involvement and practically no arylsulfatase A, B and C activities in cultured skin fibroblasts. Furthermore, arylsulfatase A activity in neonatal-type MSD was not enhanced by the addition of thiosulfate. Therefore, it is distinct from late infantile-type MSD. The degradation of 14C-sulfatide can occur in MSD-cultured skin fibroblasts and was much higher than in late infantile-type MLD. The addition of thiol protease such as leupeptin to cultured MSD skin fibroblasts enhanced arylsulfatase A activity as well as the degradation of 14C-sulfatide. This suggests that the decreased activities of arylsulfatase A is due to an acceleration of the enzyme degradation. Enzyme replacement by the addition of arylsulfatases of different sources (human liver, brain, fungus) was carried out in cultured MSD skin fibroblasts. Human enzymes of arylsulfatase A and B were mostly taken up by MSD cells rather than those of fungus origin. By the exposure to leukocytes to cultured skin fibroblasts, MSD cells corrected arylsulfatase A and B activities. 相似文献
4.
5'-Nucleotidase was found in purified rat liver tritosomes. When tritosomes were subfractionated into the membrane and soluble contents fractions, 73% of the total 5'-nucleotidase activity was found in the membrane fraction and 24% in the soluble contents fraction. Immunoblotting using specific polyclonal antibodies against the rat liver plasma membrane 5'-nucleotidase showed that the mobilities on SDS-polyacrylamide gel electrophoresis of both 5'-nucleotidases in the membrane and contents fractions were identical to that of the enzyme in the plasma membranes (Mr = 72,000). 5'-Nucleotidases in the membrane and contents fractions were sensitive to neuraminidase and converted into a form that was 4 kDa smaller after digestion, as observed in the case of plasma membrane enzyme. 5'-Nucleotidases, both from the membrane and contents fractions, were purified using immunoaffinity chromatography, and the isoelectric points, heat stability, and oligomeric structure of the purified enzymes were compared. Isoelectric focusing and the heat stability test indicated the resemblance of the soluble enzyme to the membrane-bound enzyme. However, the membrane-bound enzyme aggregated in the absence of Triton X-100, whereas the soluble enzyme behaved as a dimer. The topography of 5'-nucleotidase in the tritosomal membranes was studied using antibodies against 5'-nucleotidase and neuraminidase treatment. The inhibition of 5'-nucleotidase were not observed in the intact tritosomal fraction until the tritosomes had been disrupted by osmotic shock. These results show that the active sites and the oligosaccharide chains of 5'-nucleotidase are located on the inside surface of the tritosomal membranes. 相似文献
5.
6.
7.
We have reevaluated the sequence of porcine follicle-stimulating hormone (pFSH) with more recent protein-sequencing methodology. This has led to revision of the earlier proposed sequence. As with almost all reported gonadotropin -subunits, NH2-terminal heterogeneity was found in the porcine FSH -subunit (FSH), starting with residue Phe (1), Asp (3), Gly (4), or Thr (7). In the -subunit, there were found to be at least two molecular species, starting with residue Asn (1) (minor 20%) or Cys (3) (major 80%) as NH2-terminal and ending at residue Glu (108) as COOH-terminal. The net effect of the present revisions is to increase the homology of pFSH with other reported follitropin sequences. Apparent differences in the half-cystine placements in a previous proposal for pFSH compared with other species of FSH are no longer tenable. The half-cystine placements thus remain a constant structural feature throughout the gonadotropin hormones (choriogonadotropin, follitropin, and lutropin). 相似文献
8.
It is often reported that an animal with spotty coat markings on its body has a tail with stripe-shaped pattern. In other various biological and chemical phenomena in/on cylinder-like domains, longitudinally periodic band patterns are observed much more often than the other non-uniform patterns. This paper mathematically explains these observations by proving that, in/on a long and narrow cylinder-like domain, any solution of reaction-diffusion system asymptotically loses its spatial dependence in the transectional/circumferential direction. 相似文献
9.
Fertilization of the medaka egg in 10% Ringer's solution generates a depolarization of 4 mV just before the appearance of a characteristically longer hyperpolarization (25). The depolarization appears to be the result of a nonspecific leak triggered by sperm stimulation and the amplitude of the depolarization is thought to be independent of [Ca2+ ]o (25). We have investigated the ionic dependence of this depolarization. An initial small depolarization (3–4 mV; duration, 5–8 sec) is followed by a rising phase of a spike-like depolarization in the range of 10–60 mV. The amplitude of this spike-like depolarization is propodional to log [Ca2+ ], ranging from 0.33–18 mM. Calcium antagonists, e.g. 10 mM cobalt or 10 μg/ml verapamil in 10% Ringer do not block the depolarization in the presence of 1.1 mM CaCl2 . 相似文献
10.
Hypoxia-induced fibre type transformation in rat hindlimb muscles
Histochemical and electro-mechanical changes 总被引:1,自引:0,他引:1
Histochemical and electro-mechanical changes 总被引:1,自引:0,他引:1
Kazuo Itoh Toshio Moritani Koji Ishida Chiyoko Hirofuji Sadayoshi Taguchi Minoru Itoh 《European journal of applied physiology and occupational physiology》1990,60(5):331-336
Twelve male Sprague-Dawley rats (21 days old) were randomly assigned into two experimental groups: sea level control (CONT) and hypobaric hypoxia (HYPO). The HYPO rats were kept in an hypobaric chamber maintaining a simulated altitude of 4000 m (61.1 kPa). After 10 weeks of treatment, the rat hindlimb muscles [soleus (SOL) and extensor digitorum longus (EDL)] were subjected to histochemical and electro-mechanical analyses. Results indicated that compared to CONT the HYPO SOL muscle had a significantly greater relative distribution of fast-twitch-oxidative-glycolytic (FOG) fibres (28.9% SEM 2.0 vs 18.3% SEM 1.8, P less than 0.01) with a significant decrease in slow twitch oxidative fibre distribution (69.5% SEM 2.4 vs 82.9% SEM 3.1, P less than 0.01). Compared to CONT the HYPO EDL muscle also manifested a significant increase in FOG fibre distribution (51.6% SEM 0.8 vs 46.6% SEM 1.1, P less than 0.01), but this was accompanied by a significant decrease in fast twitch glucolytic fibres (44.3% SEM 0.9 vs 49.2% SEM 1.7, P less than 0.05). These histochemical fibre type transformations accompanied significant and expected changes in the electro-mechanical parameters tested in situ, e.g. maximal twitch force, maximal rate of force development, contraction time, half relaxation time, force: frequency curve, and fatigability. It was concluded that chronic hypobaric hypoxia could have a potent influence upon the phenotype expression of muscle fibres. 相似文献