全文获取类型
收费全文 | 4134篇 |
免费 | 232篇 |
国内免费 | 1篇 |
出版年
2023年 | 13篇 |
2022年 | 28篇 |
2021年 | 64篇 |
2020年 | 43篇 |
2019年 | 41篇 |
2018年 | 67篇 |
2017年 | 58篇 |
2016年 | 82篇 |
2015年 | 140篇 |
2014年 | 172篇 |
2013年 | 253篇 |
2012年 | 291篇 |
2011年 | 281篇 |
2010年 | 148篇 |
2009年 | 163篇 |
2008年 | 263篇 |
2007年 | 254篇 |
2006年 | 246篇 |
2005年 | 231篇 |
2004年 | 274篇 |
2003年 | 217篇 |
2002年 | 202篇 |
2001年 | 74篇 |
2000年 | 41篇 |
1999年 | 62篇 |
1998年 | 44篇 |
1997年 | 40篇 |
1996年 | 30篇 |
1995年 | 39篇 |
1994年 | 39篇 |
1993年 | 27篇 |
1992年 | 37篇 |
1991年 | 36篇 |
1990年 | 36篇 |
1989年 | 42篇 |
1988年 | 23篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 29篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有4367条查询结果,搜索用时 15 毫秒
71.
The effect of 6059-S, a novel 1-oxacephem, on peptidoglycan synthesis was investigated using ether-treated cells of Escherichia coli K 12, Pseudomonas aeruginosa KM 338 and Serratia marcescens IFO 12648. The cross-linking reaction of peptidoglycan synthesis in these organisms was inhibited by markedly low concentration of 6059-S.Non-standard abbreviations PBP
penicillin binding protein
- MIC
minimum inhibitory concentration
- ETB
ether treated bacterial cells
- SDS
sodium dodecylsulfate 相似文献
72.
The effect of indole-3-acetic acid on cell wall loosening andchemical modifications of noncellulosic components of the cellwall in Avena coleoptile segments was studied and the followingresults were obtained. (1) Auxin decreased both the minimum stress-relaxation time(To) and the noncellulosic glucose content of the cell wall. (2) Decreases were observed in the absence or presence of mannitolsolution at concentrations lower than 0.20 M which osmoticallysuppressed auxin-induced extension, while at concentrationshigher than 0.25 M, there was little auxin effect, indicatingthat it is turgor-dependent. (3) The decrease in To of the cell wall and that in the noncellulosicglucose content caused by auxin in the presence of mannitolsolutions of various concentrations paralleled each other (thecorrelation coefficient was 0.897). (4) Both decreases in To and glucose content caused by auxinwere inhibited by nojirimycin (5-amino-5-deoxy-D-glucopyranose)in the presence of mannitol. The results suggest that auxin-induced cell wall loosening iscaused by the degradation of noncellulosic rß-glucanin the cell wall. (Received December 24, 1976; ) 相似文献
73.
Auxin-indnced changes in barley coleoptile cell wall composition 总被引:1,自引:0,他引:1
Auxin induces extension growth of barley coleoptile segments,causing cell extension and cell wall loosening represented bya change in mechanical properties of the cell wall. This responsedecreased after the segments were starved for more than 12 hrin buffer solution. Auxin decreased the noncellulosic glucosecontent of the cell wall of the segments starved for 0 and 6hr, but very little that of segments starved for 12 and 18 hr.The contents of arabinose, xylose and galactose, among noncellulosicpolysaccharides, and -cellulose of the cell wall increased duringthe starvation, but auxin did not affect them. The auxin-induceddecrease in glucose content was inhibited by nojirimycin, apotent inhibitor of ß-glucanase, which inhibited auxin-inducedextension and changes in mechanical properties of the cell wall,suggesting that cell wall loosening, and thus cell extension,resulted from partial degradation of ß-glucan of thecell wall. (Received April 20, 1978; ) 相似文献
74.
75.
T Muta T Miyata Y Misumi F Tokunaga T Nakamura Y Toh Y Ikehara S Iwanaga 《The Journal of biological chemistry》1991,266(10):6554-6561
76.
Kunihiro Kuwajima Naoki Okayama Kaori Yamamoto Tsuyoshi Ishihara Shintaro Sugai 《FEBS letters》1991,290(1-2)
Kinetics of unfolding and refolding of a staphylococcal nuclease mutant, in which Pro117 is replaced by glycine, have been investigated by stopped-flow circular dichroism, and the results are compared with those for the wild-type protein. In contrast to the biphasic unfolding of the wild-type nuclease, the unfolding of the mutant is represented by a single-phase reaction, indicating that the biphasic unfolding for the wild-type protein is caused by cis-trans isomerization about the prolyl peptide bond in the native state. The proline mutation also simplifies the kinetic refolding. Importance of the results in elucidating the folding mechanism is discussed. 相似文献
77.
Polycelis (Seidlia) auriculata is endemic to mountain districts of Japan, from the central part of Honshû to the area of the Daisetsu Mts of Hokkaidô. In northern Japan, it sometimes occurs in cold-water biotopes of lowland areas. The progenitor of P. auriculata appears to have been the oldest immigrant into northern Japan among the Japanese Polycelis species, entering through a northern route as a preglacial faunal element. P. auriculata now shows a discontinious distribution in northern Japan. By virtue of its geographical and vertical distribution, ecological niche, variation in anatomy of the copulatory apparatus, and cytodemes, this species appears to be in the process of transformation. 相似文献
78.
S Yamamoto T Yamamoto T Kataoka E Kuramoto O Yano T Tokunaga 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(12):4072-4076
Thirty-mer single-stranded oligonucleotides, with a sequence chosen from the known cDNA encoding the 64-kDa protein named Ag A or the MPB-70 protein of Mycobacterium bovis BCG and the human cellular proteins such as complement component 1 inhibitor and Ig rearranged lambda-chain, were used to dissect the capability to induce IFN and to augment NK cell activity of mouse spleen cells by coincubation in vitro. Three with the hexamer palindromic sequence as GACGTC were active, whereas two kinds of oligonucleotides with no palindrome were inactive. The oligonucleotides containing at least one of the different palindromic sequences showed no activity. When a portion of the sequence of the inactive oligonucleotides was substituted with either palindromic sequence of GACGTC, AGCGCT, or AACGTT, the oligonucleotide acquired the ability to augment NK activity. In contrast, the oligonucleotides substituted with another palindromic sequence such as ACCGGT was without effect. Furthermore, exchange of two neighboring mononucleotides within, but not outside, the active palindromic sequence destroyed the ability of the oligonucleotides to augment NK cell activity. Stimulation of spleen cells with the substituted oligonucleotide, A4a-AAC, induced production of significant amounts of IFN-alpha/beta and small amounts of IFN-gamma. Augmentation of NK activity of the cells by the oligonucleotide was ascribed to IFN-alpha/beta production. These results strongly suggest that the presence of the unique palindromic sequences, such as GACGTC, AGCGCT, and AACGTT, but not ACCGGT, is essential for the immunostimulatory activity of oligonucleotides. 相似文献
79.
Naoki Koyama Yukio Takahata Michael A. Huffman Koshi Norikoshi Hisayo Suzuki 《Primates; journal of primatology》1992,33(1):33-47
Over a 30-year period from 1954 to 1983, 975 live births were recorded for Japanese macaque females at the Iwatayama Monkey
Park, Arashiyama, Japan. Excluding unknown birth dates, primiparous mothers gave birth to 185 infants (182 cases with age
of mother known) and multiparous mothers gave birth to 723 infants (603 cases with age of mother known). The peak month of
birth was May with 52.3% of the total births occurring during the period. Multiparous females who had not given birth the
previous year did so earlier than multiparous females who had given birth the previous year and also earlier than primiparous
females. Among the females who had given birth the previous year, females whose infant had died gave birth earlier than females
who had reared an infant the previous year. The offspring sex ratio (1:0.97) was not significantly different from 1:1, and
revealed no consistent association with mother's age. Age-fecundity exhibited a humped curve. The annual birth rate was low
at the age of 4 years but increased thereafter, ranging between 46.7% and 69.0%, at between 5 and 19 years of age, but again
decreased for females between 20 and 25 years of age. Some old females displayed clear reproductive senescence. The infant
mortality within the first year of age was quite low (10.3%) and the neonatal (less than 1 month old) mortality rate accounted
for 49.0% of all infant deaths. There was no significant difference between the mortality rates of male and female infants.
A female's rank-class had no apparent effect on the annual birth rate, infant mortality, and offspring sex ratio. These long-term
data are compared with those from other primate populations. 相似文献
80.
A Kumatori K Tanaka T Tamura T Fujiwara A Ichihara F Tokunaga A Onikura S Iwanaga 《FEBS letters》1990,264(2):279-282
The nucleotide sequence of component C9 of rat proteasomes (multicatalytic proteinase complexes) has been determined from a recombinant cDNA clone isolated by screening a Reuber H4TG hepatoma cell cDNA library using synthetic oligodeoxynucleotide probes corresponding to partial amino acid sequences of the protein. The predicted sequence of C9 consists of 261 amino acid residues with a calculated molecular weight of 29,496. The C9 component is a novel protein, differing from known proteins, but its primary structure resembles those of other proteasome components, including C2, C3 and C5, although its similarity to C5 is relatively low, suggesting that proteasomes consist of a family of proteins that have evolved from a common ancestor. 相似文献