全文获取类型
收费全文 | 26483篇 |
免费 | 2211篇 |
国内免费 | 1372篇 |
出版年
2024年 | 43篇 |
2023年 | 215篇 |
2022年 | 567篇 |
2021年 | 945篇 |
2020年 | 710篇 |
2019年 | 875篇 |
2018年 | 997篇 |
2017年 | 757篇 |
2016年 | 1125篇 |
2015年 | 1708篇 |
2014年 | 1945篇 |
2013年 | 2061篇 |
2012年 | 2472篇 |
2011年 | 2330篇 |
2010年 | 1390篇 |
2009年 | 1316篇 |
2008年 | 1545篇 |
2007年 | 1459篇 |
2006年 | 1292篇 |
2005年 | 1105篇 |
2004年 | 1074篇 |
2003年 | 880篇 |
2002年 | 682篇 |
2001年 | 450篇 |
2000年 | 367篇 |
1999年 | 321篇 |
1998年 | 216篇 |
1997年 | 176篇 |
1996年 | 161篇 |
1995年 | 131篇 |
1994年 | 115篇 |
1993年 | 68篇 |
1992年 | 96篇 |
1991年 | 77篇 |
1990年 | 84篇 |
1989年 | 66篇 |
1988年 | 47篇 |
1987年 | 48篇 |
1986年 | 28篇 |
1985年 | 29篇 |
1984年 | 35篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Kyung Hoon Jung Jeong Hwan Kim Yeong Joong Jeon Jae Heung Lee 《Biotechnology letters》1993,15(1):65-70
Summary A novel two enzyme system of fructosyltransferase and glucose oxidase to enhance the content of the net fructo—oligosaccharide (FOS) fractions in the industrial production of FOS syrup from sucrose was devised. The net FOS content in the commercial FOS syrup has been limited only to 55–60 % due to the accumulation of glucose which acts as a feedback inhibitor of the fructosyltransferase. By supplementing glucose oxidase to the conventional FOS reaction system, we could convert the glucose to gluconic acid readily separable from neutral sugars by simple ion exchange operation in the next step. The simultaneous removal of glucose was proved effective in proceeding the reaction by fructosyltransferase further by relieving the product inhibition caused by glucose. By this way, we could raise the net FOS content as high as 90 %. 相似文献
103.
Almost every cell in the Drosophila pupal wing forms a single, distally pointing cuticular hair. The function of the frizzled (fz) gene is essential for the elaboration of the normal wing hair pattern. In the absence of fz function hairs develop, but they display an abnormal polarity. We have examined the developmental expression of the fi gene at the RNA level via in situ hybridization and at the protein level via Western blotting. We have found that fz is expressed in all regions of the epidermis before, during, and after the fz cold sensitive period. We have also found that fz function is not required for normal fi expression. We have further found that mutations in several other tissue polarity genes do not noticeably alter the expression or the modification state of the Fz protein. © 1994 Wiley-Liss, Inc. 相似文献
104.
105.
106.
107.
108.
The dependence of blastocyst development on the extracellular Na+/K+ ratio was investigated in an in vitro system. Hatching and outgrowth of mouse blastocysts was enhanced at Na+/K+ ratios between 3 and 10 compared to the ratio of about 25 typical for most culture media and serum. At a Na+/K+ ratio of 2, blastocyst hatching and outgrowth were inhibited. The requirement of blastocyst development for relatively high extracellular K+ concentrations agrees with the fact that K+ concentrations in oviduct and uterine secretions are higher than in serum. The findings can also be relevant in optimizing in vitro culturing techniques for blastocysts. 相似文献
109.
Y. Li M. M. Bhargava A. Joseph L. Jin E. M. Rosen I. D. Goldberg 《In vitro cellular & developmental biology. Animal》1994,30(2):105-110
Summary Using an automated cell analyzer system, the effect of hepatocyte growth factor/scatter factor (HGF/SF), epidermal growth
factor (EGF), basic fibroblast growth factor (bFGF), endothelial acidic fibroblast growth factor (a-FGF), platelet derived
growth factor (PDGF), and recombinant human insulinlike growth factor (IGF) on the motility and morphology of Madin-Darby
canine kidney (MDCK), rat hepatomas, C2, and H5–6 and murine mammary carcinoma (EMT-6) cells was investigated. Treatment of MDCK cells with HGF/SF, bFGF, EGF, and a-FGF resulted
in an increase in average cell velocity and in the fraction of moving cells. Cells treated with the PDGF and IGF did not show
significant alterations in velocity. MDCK cells treated with each growth factor were classified into groups of “fast” and
“slow” moving cells based on their average velocities, and the average morphologic features of the two groups were quantitated.
Fast-moving cells had larger average area, circularity, and flatness as compared to slow-moving cells. Factors that stimulated
cell movement also induced alterations in cell morphologic parameters including spreading, flatness, area, and circularity.
HGF/SF also scattered and stimulated motility of C2 and H5–6 hepatoma cells. In contrast to MDCK cells, there was no significant difference between the morphology of the fast moving
and slow moving C2 and H5–6 cells. These studies suggest that growth factor cytokines have specific effects on motility of normal and tumor cells. 相似文献
110.
Xin-Min Li† Jin Qi Augusto V. Juorio Alan A. Boulton 《Journal of neurochemistry》1993,61(4):1573-1576
Abstract: Gliosis is commonly observed in the CNS following tissue damage, and it also occurs in aging and in many neurodegen-erative diseases. Glial fibrillary acidic protein (GFAP) accumulation is a prominent feature of astrocytic gliosis. An inhibition or delay in GFAP synthesis could mitigate scar formation and thus reduce the formation of a physical barrier. The consequence of this would be to allow neurons and oligodendrocytes to reestablish a functional environment. (—)-Deprenyl, a specific monoamine oxidase (MAO) B inhibitor, has been used as an effective antipar-kinsonian drug, and it has been reported to possess neuroprotective and neurorescue properties. Using northern and slot blots to detect GFAP mRNA in C6 glioma cells, we have demonstrated that (—)-deprenyl decreases the abundance of GFAP mRNA in a time- and dose-dependent manner. The effect seems to be specific to MA0 B inhibitors because (+)-deprenyl and clorgyline exhibit no effect. This study indicates therefore that (-)-deprenyl may be useful for regulating astrogliosis following CNS injury as well as in some neurodegenerative diseases. 相似文献