全文获取类型
收费全文 | 40037篇 |
免费 | 2501篇 |
国内免费 | 2334篇 |
出版年
2023年 | 576篇 |
2022年 | 730篇 |
2021年 | 1260篇 |
2020年 | 1173篇 |
2019年 | 1657篇 |
2018年 | 1438篇 |
2017年 | 932篇 |
2016年 | 989篇 |
2015年 | 1268篇 |
2014年 | 2321篇 |
2013年 | 2856篇 |
2012年 | 1724篇 |
2011年 | 2418篇 |
2010年 | 1704篇 |
2009年 | 1917篇 |
2008年 | 2023篇 |
2007年 | 2177篇 |
2006年 | 1895篇 |
2005年 | 1686篇 |
2004年 | 1480篇 |
2003年 | 1204篇 |
2002年 | 1095篇 |
2001年 | 755篇 |
2000年 | 660篇 |
1999年 | 691篇 |
1998年 | 678篇 |
1997年 | 536篇 |
1996年 | 551篇 |
1995年 | 509篇 |
1994年 | 427篇 |
1993年 | 379篇 |
1992年 | 376篇 |
1991年 | 319篇 |
1990年 | 269篇 |
1989年 | 236篇 |
1988年 | 236篇 |
1987年 | 218篇 |
1986年 | 179篇 |
1985年 | 313篇 |
1984年 | 441篇 |
1983年 | 354篇 |
1982年 | 396篇 |
1981年 | 273篇 |
1980年 | 271篇 |
1979年 | 273篇 |
1978年 | 223篇 |
1977年 | 164篇 |
1976年 | 137篇 |
1975年 | 121篇 |
1974年 | 124篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
81.
Geoffrey P Dobson 《BBA》2002,1553(3):261-267
Our aim was to estimate a number of bioenergetic parameters in the beating mouse, rat and guinea pig heart in situ and compare the values to those in hearts of mammals over a 2000-fold range in body mass. For the mouse, rat and guinea pig heart, we report a phosphorylation ratio of 1005±50 (n=16), 460±32 (n=10) and 330±22 (n=5) mM−1 and a free cytosolic [ADP] concentration of 13, 18 and 22 μM, respectively. When each parameter was plotted against body mass, they scaled closely to the quarter power (−0.28, r=0.99 and −0.23, r=0.97). A similar regression slope was found when the inverse of free [ADP] was plotted against absolute mitochondrial (slope=−0.26, r=0.99) and myofibrillar volumes (slope=−0.24, r=0.99). The similar slopes indicate that the ratio of absolute mitochondria and myofibrillar volumes in the healthy mammalian heart is a constant, and independent of body size. In conclusion, our study supports the hypothesis that the mammalian heart has a number of highly conserved thermodynamic and kinetic parameters that obey quarter-power laws linking the phosphorylation ratio, ATP turnover rates, free [ADP] and absolute mitochondrial volumes to body size. The results are discussed in terms of possible mechanisms and potential deviations from these laws in some disease states. 相似文献
82.
83.
84.
Prion colonization of secondary lymphoid organs (SLOs) is a critical step preceding neuroinvasion in prion pathogenesis. Follicular dendritic cells (FDCs), which depend on both tumor necrosis factor receptor 1 (TNFR1) and lymphotoxin β receptor (LTβR) signaling for maintenance, are thought to be the primary sites of prion accumulation in SLOs. However, prion titers in RML-infected TNFR1−/− lymph nodes and rates of neuroinvasion in TNFR1−/− mice remain high despite the absence of mature FDCs. Recently, we discovered that TNFR1-independent prion accumulation in lymph nodes relies on LTβR signaling. Loss of LTβR signaling in TNFR1−/− lymph nodes coincided with the de-differentiation of high endothelial venules (HEVs)—the primary sites of lymphocyte entry into lymph nodes. These findings suggest that HEVs are the sites through which prions initially invade lymph nodes from the bloodstream. Identification of HEVs as entry portals for prions clarifies a number of previous observations concerning peripheral prion pathogenesis. However, a number of questions still remain: What is the mechanism by which prions are taken up by HEVs? Which cells are responsible for delivering prions to lymph nodes? Are HEVs the main entry site for prions into lymph nodes or do alternative routes also exist? These questions and others are considered in this article. 相似文献
85.
86.
87.
In the present study, we addressed the question of whether treatment with mannitol, an osmotic diuretic, affects astrogliovascular responses to status epilepticus (SE). In saline-treated animals, astrocytes exhibited reactive astrogliosis in the CA1-3 regions 2-4 days after SE. In the mannitol-treated animals, a large astroglial empty zone was observed in the CA1 region 2 days after SE. This astroglial loss was unrelated to vasogenic edema formation. There was no difference in SE-induced neuronal loss between saline- and mannitol-treated animals. Furthermore, mannitol treatment did not affect astroglial loss and vasogenic edema formation in the dentate gyrus and the piriform cortex. These findings suggest that mannitol treatment induces selective astroglial loss in the CA1 region independent of vasogenic edema formation following SE. These findings support the hypothesis that the susceptibility of astrocytes to SE is most likely due to the distinctive heterogeneity of astrocytes independent of hemodynamics. [BMB Reports 2015; 48(9): 507-512] 相似文献
88.
Blood coagulation factor X (FX) is converted to its active form (FXa) by a membrane bound multi-protein enzyme complex, comprised of factor VIII (FVIII), factor IXa (FIXa) and FX. Characterization of the molecular forces involved in the association of these proteins with phospholipids is crucial to understanding how these proteins bind to the lipid milieux of physiological membranes. In this report, the molecular forces involved in the association of FVIII, FIXa or FX with phospholipid vesicles (PLV) were characterized by ligand affinity chromatographic analyses. Treating FVIII-affinity columns with agents that disrupt electrostatic interactions caused elution of 15.2% of the total bound PLV, while agents that disrupt hydrophobic interactions caused elution of 84.8% of the total bound PLV. These results demonstrate that the association of PLV with FVIII is primarily hydrophobic. In contrast, the association of PLV with FIXa or FX is largely the result of electrostatic forces. This was established by observing that 71.3% and 78.9% of the total bound PLV was eluted from FIXa- and FX-affinity columns, respectively, by agents that disrupt electrostatic interactions. Of the total bound PLV, 28.7% and 21.2% were eluted from FIXa- and FX-affinity columns, respectively, by agents that disrupt hydrophobic interactions. These data demonstrate that hydrophobic forces play a heretofore unrecognized role in the association of PLV with FIXa or FX. 相似文献
89.
《Journal of enzyme inhibition and medicinal chemistry》2013,28(5):1105-1112
Nine novel 4-[3-(4-Dimethylamino-phenyl)-5-aryl-4,5-dihydro-pyrazol-1-yl]-benzenesulfonamides (2a-i) were synthesized and evaluated for their anti-inflammatory and antiproliferative activities. These compounds (2a-i) showed moderate to strong anti-inflammatory activity in carrageenan rat paw oedema test. Compounds 2b, 2d and 2g showing comparable anti-inflammatory activity to that of reference drug celecoxib were evaluated for their ulcerogenic and analgesic activities. The effect of 2b, 2d and 2g on the content of NO, TNF-α and PGE2 in exudates from rat paw stimulated by carrageenan was also evaluated. The compound 2c showed considerable antitumor activities against all 60 human tumor cell lines with effective GI50 (MG-MID) value of 3.63 µM. It exhibited maximum activity against melanoma (LOX IMVI and SK-MEL-5) cancer cell lines with GI50 value less than 2 μM. 相似文献
90.
Stanley K. Shapiro Fritz Schlenk 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,633(2):176-180
5′-Methylthio[U-14C]adenosine was used as a culture supplement for Candida utilitis. The resulting S-adenosylmethionine was hydrolyzed into its structural components. Virtually none of the label of the pentose was found in the carbohydrate part of the intracellular S-adenosylmethionine. Much of it was present in the four-carbon chain of the methionine part of the sulfonium compound. The U-14C)-labeled adenine of 5′-methylthio[U-14C]adenosine did not contribute to the labeling of the amino acid component of the sulfonium compound. 相似文献