全文获取类型
收费全文 | 2370篇 |
免费 | 178篇 |
专业分类
2548篇 |
出版年
2021年 | 29篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 25篇 |
2017年 | 35篇 |
2016年 | 40篇 |
2015年 | 52篇 |
2014年 | 86篇 |
2013年 | 147篇 |
2012年 | 121篇 |
2011年 | 118篇 |
2010年 | 71篇 |
2009年 | 59篇 |
2008年 | 104篇 |
2007年 | 109篇 |
2006年 | 114篇 |
2005年 | 136篇 |
2004年 | 130篇 |
2003年 | 114篇 |
2002年 | 135篇 |
2001年 | 82篇 |
2000年 | 91篇 |
1999年 | 70篇 |
1998年 | 31篇 |
1997年 | 35篇 |
1996年 | 41篇 |
1995年 | 36篇 |
1994年 | 28篇 |
1993年 | 27篇 |
1992年 | 51篇 |
1991年 | 46篇 |
1990年 | 39篇 |
1989年 | 42篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 21篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1972年 | 7篇 |
1970年 | 6篇 |
1969年 | 8篇 |
排序方式: 共有2548条查询结果,搜索用时 15 毫秒
11.
Based on the assumption of nonidentical two heads of myosin it is pointed out that a strong motive force is generated in actomyosin pair only when ATP-decomposition occurs co-operatively at the both heads and that the tension-independent part of shortening heat is liberated when an ATP molecule is decomposed only at the burst head. These two actions of actomyosin pair are related to the two states of force-generator in Huxley-Simmons' model. Elementary cycles at different positions in a sarcomere are interacted each other through feedback loop via sliding motion of muscular filaments. Due to this synergetic interaction the rate constant for the rate-determining step of elementary cycle has a dependence on velocity v of shortening such as k = k ° + κv. From these functions and properties of actomyosin system in vivo, the following properties of muscle are explained consistently in a quantitative manner: (1) Hill's equation on the relationship between tension and velocity of shortening, (2) damped oscillations in tension and in muscular length around steady state, (3) Hill's energy equation improved in 1964, (4) the chemical equivalence of shortening heat, (5) the influence of tension on the incorporation of radio-active phosphate into ATP and (6) the asymmetric activation by actomyosin system only for the forward reaction, the decomposition of ATP. 相似文献
12.
Wakana Saso Masako Yamasaki Shin-ichi Nakakita Shuetsu Fukushi Kana Tsuchimoto Noriyuki Watanabe Nongluk Sriwilaijaroen Osamu Kanie Masamichi Muramatsu Yoshimasa Takahashi Tetsuro Matano Makoto Takeda Yasuo Suzuki Koichi Watashi 《PLoS pathogens》2022,18(6)
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been transmitted across all over the world, in contrast to the limited epidemic of genetically- and virologically-related SARS-CoV. However, the molecular basis explaining the difference in the virological characteristics among SARS-CoV-2 and SARS-CoV has been poorly defined. Here we identified that host sialoglycans play a significant role in the efficient spread of SARS-CoV-2 infection, while this was not the case with SARS-CoV. SARS-CoV-2 infection was significantly inhibited by α2-6-linked sialic acid-containing compounds, but not by α2–3 analog, in VeroE6/TMPRSS2 cells. The α2-6-linked compound bound to SARS-CoV-2 spike S1 subunit to competitively inhibit SARS-CoV-2 attachment to cells. Enzymatic removal of cell surface sialic acids impaired the interaction between SARS-CoV-2 spike and angiotensin-converting enzyme 2 (ACE2), and suppressed the efficient spread of SARS-CoV-2 infection over time, in contrast to its least effect on SARS-CoV spread. Our study provides a novel molecular basis of SARS-CoV-2 infection which illustrates the distinctive characteristics from SARS-CoV. 相似文献
13.
Shin Ugawa Kojiro Iwamoto Yojiro Matsuura Masamichi Takahashi Kenji Fukuda 《Plant and Soil》2010,326(1-2):303-310
We clarified the differences in root-tip diameter (RTD) among tree and shrub species in an Abies forest. To evaluate the effects of sampling month and tree size on RTD, we measured the root-tip diameters of mature individuals of nine woody species and sapling individuals of two Abies species in a subalpine Abies forest on Mount Shimagare in central Japan. Species, sampling month, and their interaction affected RTD; however, the differences in RTD between some pairs of species were consistent across sampling months. The woody species fell into two groups, based on RTD size: tree species with larger RTDs (group 1) and shrub species with smaller RTDs (group 2). Seasonal changes in RTD were observed in three species and showed different patterns among species. Tree size did not affect RTD for either Abies species; however, there was an interaction between tree size and sampling month for Abies veitchii. The woody species category had the greatest effect on RTD, followed by sampling month and then tree size. 相似文献
14.
Hiroyuki Inoue Chiaki Kitao Shinichi Yano Shigeki Sawayama 《World journal of microbiology & biotechnology》2016,32(11):186
On-site cellulase and hemicellulase production is a promising way to reduce enzyme cost in the commercialization of the lignocellulose-to-ethanol process. A hemicellulase-producing fungal strain suitable for on-site enzyme production was selected from cultures prepared using wet disc-milling rice straw (WDM-RS) and identified as Trichoderma asperellum KIF125. KIF125 hemicellulase showed uniquely high abundance of β-xylosidase in the xylanolytic enzyme system compared to other fungal hemicellulase preparations. Supplementation of Talaromyces cellulolyticus cellulase with KIF125 hemicellulase was more effective than that with the hemicellulases from other fungal sources in reducing the total enzyme loading for the improvement of xylose yield in the hydrolysis of ball-milling RS, due to its high β-xylosidase dominance. β-Xylosidase in KIF125 hemicellulase was purified and classified as a glycosyl hydrolase family 3 enzyme with relatively high specificity for xylobiose. The production of KIF125 β-xylosidase in the fermentor was estimated as 118 U/g-WDM-RS (2350 U/L culture) at 48 h. These results demonstrate that KIF125 is promising as a practical hemicellulase source to combine with on-site cellulase production using T. cellulolyticus. 相似文献
15.
16.
17.
The spider mite Tetranychus urticae shows variation in its dispersal capacity (i.e., the leaf quality at which a female decides to disperse). We were able to
artificially select mites that had either a high or a low dispersal capacity, indicating that this trait was genetically controlled.
We then compared correlated responses to this selection. Mites with a genetically high dispersal capacity (‘HD’ strains) had
a higher diapause incidence and a lower performance compared to mites with a low dispersal capacity (‘LD’ strains). A possible
effect of random genetic drift during the selection was negligible. Our results suggest that differential dispersal capacity
is associated with contrasting life history patterns as a result of natural selection.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
19.
T Kawamoto Y Ikeuchi Y Mikata M K Kishigami S Yano C Murayama T Mori F Yoneda 《Bioorganic & medicinal chemistry letters》2001,11(13):1745-1748
6-Nitro- and 8-nitro-5-deazaflavin derivatives have been found to enhance prominently the radiation-induced formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) at the expense of formation of 2,6-diamino-4-hydroxy-5-formamidopyrimidine nucleosides (FapydGuo) both in deaerated and in N(2)O saturated aqueous 2'-deoxyguanosine solutions. The radiosensitizing capacity of a 9-nitro-5-deazflavin derivative was observed only in the N(2)O saturated aqueous solutions. 相似文献
20.
As it walks, the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) spins a trail of silk threads, that is followed by the predatory mite, Neoseiulus womersleyi Schicha (Acari: Phytoseiidae). Starved adult female N. womersleyi followed T. urticae trails laid down by five T. urticae females but did not follow a trail of one T. urticae female, suggesting that the amount of spun threads and their chemical components should correlate positively with the number
of T. urticae individuals. To examine whether chemical components of T. urticae trails are responsible for the predatory mite’s trail following, we collected separate T. urticae threads from the exuviae and eggs, and then washed the threads with methanol to separate chemical components from physical
attributes of the threads. Female N. womersleyi did not follow T. urticae trails that had been washed with methanol but contained physical residues, but they did follow the direction to which the
methanol extracts of the T. urticae trails was applied. These results suggest that the predatory mite follows chemical, not physical, attributes of T. urticae trails. 相似文献