全文获取类型
收费全文 | 2431篇 |
免费 | 114篇 |
专业分类
2545篇 |
出版年
2022年 | 9篇 |
2021年 | 14篇 |
2020年 | 18篇 |
2019年 | 27篇 |
2018年 | 36篇 |
2017年 | 25篇 |
2016年 | 38篇 |
2015年 | 60篇 |
2014年 | 63篇 |
2013年 | 248篇 |
2012年 | 157篇 |
2011年 | 155篇 |
2010年 | 82篇 |
2009年 | 109篇 |
2008年 | 148篇 |
2007年 | 135篇 |
2006年 | 141篇 |
2005年 | 132篇 |
2004年 | 152篇 |
2003年 | 144篇 |
2002年 | 139篇 |
2001年 | 20篇 |
2000年 | 29篇 |
1999年 | 35篇 |
1998年 | 30篇 |
1997年 | 34篇 |
1996年 | 24篇 |
1995年 | 30篇 |
1994年 | 29篇 |
1993年 | 25篇 |
1992年 | 24篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1985年 | 8篇 |
1984年 | 16篇 |
1982年 | 10篇 |
1981年 | 22篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1970年 | 6篇 |
1966年 | 6篇 |
排序方式: 共有2545条查询结果,搜索用时 0 毫秒
991.
Masahiro Ito Masahiro Watanabe Toshiaki Ihara Hitoshi Kamiya Minoru Sakurai 《Cellular immunology》1995,160(2):173-177
Fas antigen and bcl-2 expression on peripheral blood mononuclear cells (PBMC) cultured with cytomegalovirus (CMV) and varicella—zoster virus (VZV) antigen was analyzed by three-color flow cytometry. Expression of Fas antigen increased significantly in CD45RO+ populations of both CD4+ and CD8+ cells obtained from CMV and VZV seropositive donors after culture with CMV and VZV antigen for 6 days. Fas antigen expression did not increase in PBMC cultured with control antigen. In contrast, bcl-2 expression decreased both in CD4+CD45RO+ and CD8+CD45RO+ cells from the same donors. Fas antigen and bcl-2 expression in CD45RA+ populations did not change. Cell viability of cultured cells with CMV and VZV antigen decreased after treatment with anti-Fas antibody and DNA fragments indicating apoptosis were detected in the cell lysate of these cultured cells after treatment with anti-Fas antibody. These data suggest that Fas antigen and bcl-2 protein may interact in regulating the cell death process of activated memory lymphocytes and eliminating lymphocytes activated by viral infection. 相似文献
992.
993.
Naoki Nagatani Masashige Shinkai Yayoi Nagase Hiroyuki Honda Ken-ichiro Hata Hirokazu Mizuno Minoru Ueda Takeshi Kobayashi 《Biotechnology letters》2000,22(12):999-1002
A non-viral transfection method for oral mucosal cells was investigated using a modified transfection method and five commercial transfection reagents. The CellFECTINTM gave the highest expression of a transfected gene. When the mucosal cells were transfected with 0.3 ng DNA/cell, the transfection efficiency was optimal, and the production of a reporter protein increased up to ten times higher than those with the other transfection reagents. 相似文献
994.
Takebayashi H Yoshida S Sugimori M Kosako H Kominami R Nakafuku M Nabeshima Y 《Mechanisms of development》2000,99(1-2):143-148
995.
The mechanism by which malate synthesis from CO2 is increasedunder low concentrations of CO2 was investigated in C3 plants.A number of metabolites were administered to illuminated tomatoleaves, and their effects on the incorporation of 14CO2 intomalate were determined. Compared with water as a control, glycolate,glyoxylate, D,L-glycerate, glycine, phosphoglycolate and L-serineincreased malate synthesis by factors of 6.8, 3.8, 3.3, 2.5,2.3 and 2.2, respectively. The effect of exogenous glycolateon malate synthesis from CO2 was dependent on its concentrationup to 100 mu, but was independent of ambient CO2 concentration.The feeding of l-14C-glycolate in the light indicated that glycolatestimulated the carbon flow from CO2 to malate. The analysis of the products of 14CO2 fixation in illuminatedleaves supplied with glycolate showed increases in malate andsugar and decreases in serine and phosphate esters. However,this stimulated malate synthesis ceased when malonate was suppliedsimultaneously with glycolate. Treatment with glycolate didnot affect the dark 14CO2-fixation, but increased the 14C-malatesynthesis, with a corresponding decrease in 14C-aspartate and14C-glutamate. These results suggest that exogenous glycolateactivates malate dehydrogenase in leaves, and that the increasedglycolate formation at low CO2 concentrations is associatedwith the increased malate synthesis from CO2. (Received January 12, 1981; Accepted May 20, 1981) 相似文献
996.
997.
The cytological instability of common wheat-rye addition lines was investigated in the present study. The chromosome numbers of almost all addition lines were considerably stable, but those of CS 5R were very variable. The rye chromosome added in this line was found to be much shorter than expected. Fluorescent in situ hybridization with 5S rDNA and the centromere-specific probes clearly revealed that the short rye chromosome contains only a short arm of chromosome 5R (5RS). In this line, chromosome numbers of both 5RS and common wheat were changeable. The chromosome numbers ranged from 2n = 36 to 2n = 44 in the cells carrying two 5RS, and ranged from 2n = 31 to 2n = 44 in one 5RS cells. In addition to the chromosome instability, the multicells wrapped in a sac-like structure were frequently observed in the root meristematic tissues of CS 5RS after the enzyme treatment for chromosome preparation. Genomic in situ hybridization with rye DNA as a probe showed that all cells in sacs investigated were at the interphase stage and contained one or two 5RS chromosomes. An electron microscopic analysis revealed that the cells of CS 5RS, particularly in sacs, have abnormal (irregular and curved) cell walls. These results indicate that 5RS has (a) specific factor(s) influencing the cell wall development as well as the genome stability. 相似文献
998.
Differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail,Papilio machaon (Lepidoptera: Papilionidae), from the Osaka population 下载免费PDF全文
To clarify differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail, Papilio machaon, we reared larvae from the Osaka population under photoperiods of 16 h light : 8 h dark (LD 16:8) (long day) or LD 12:12 (short day) at 20°C. We examined the relationship between food consumption and weight during the final larval stadium and pupae, and measured the pupal supercooling point (SCP). Although the ratio of assimilation to consumption did not differ significantly between photoperiods, the ratio of assimilation to pupal weight differed significantly between individuals reared under long and short days. All diapausing pupae were brown, whereas 56% of non‐diapausing pupae were green with the remainder brown. The mean pupal body length (L), dorsal width (W1) and lateral width (W2) were larger in non‐diapausing than in diapausing pupae, and the W1/L and W1/W2 ratios differed significantly between non‐diapausing and diapausing pupae. SCP was approximately –20°C and did not differ among pupae 5, 15 and 30 days after pupation under long‐day conditions. However, under short‐day conditions, mean SCP gradually decreased, stabilizing at approximately –24 to –25°C by 30 days after pupation. After freezing, some diapausing pupae emerged as adults, whereas all non‐diapausing pupae died. Both egestion and assimilation were greater under long‐day conditions. The results revealed that pupae of this papilionid exhibit seasonal polyphenism in physiological and morphological traits. Energy from food appears to be expended on increasing cold hardiness in the overwintering generation and on reproduction in the non‐overwintering generation. 相似文献
999.
Tanaka K Funakoshi M Kobayashi H 《Biochemical and biophysical research communications》2006,350(3):774-782
The yeast UbL-UBA protein Dsk2 is thought to act as a shuttle protein that delivers polyubiquitinated proteins to the proteasome. Previously, we identified Xenopus Dsk2-related protein, XDRP1, as a cyclin A-interacting protein. Using Xenopus egg extracts, we further characterized its two isoforms, XDRP1L and XDRP1S, with respect to cyclin binding and its degradation. Polyubiquitinated cyclins bound to the UBA domain of XDRP1L and XDRP1S, whereas monomeric cyclins A and B bound to the UbL domain of XDRP1S but not to XDRP1L. Binding of XDRP1S with monomeric cyclins was affected by a Cdc2-mediated phosphorylation of either the XDRP1S UbL domain or cyclins. Degradation of cyclin B was also prevented by XDRP1S in a Cdc2-sensitive manner. Loss of the XDRP1S-cyclin interaction allowed cyclins to be degraded in calcium-treated CSF extracts. These results suggest that the shuttling pathway via the UbL-UBA protein XDRP1 participates in degradation of mitotic cyclins in Xenopus eggs. 相似文献
1000.
Ohshige T Iwata M Omori S Tanaka Y Hirose H Kaku K Maegawa H Watada H Kashiwagi A Kawamori R Tobe K Kadowaki T Nakamura Y Maeda S 《PloS one》2011,6(10):e26911