全文获取类型
收费全文 | 5203篇 |
免费 | 364篇 |
国内免费 | 2篇 |
专业分类
5569篇 |
出版年
2024年 | 6篇 |
2023年 | 16篇 |
2022年 | 76篇 |
2021年 | 114篇 |
2020年 | 76篇 |
2019年 | 101篇 |
2018年 | 136篇 |
2017年 | 116篇 |
2016年 | 194篇 |
2015年 | 338篇 |
2014年 | 351篇 |
2013年 | 398篇 |
2012年 | 525篇 |
2011年 | 414篇 |
2010年 | 334篇 |
2009年 | 254篇 |
2008年 | 330篇 |
2007年 | 299篇 |
2006年 | 291篇 |
2005年 | 251篇 |
2004年 | 237篇 |
2003年 | 197篇 |
2002年 | 139篇 |
2001年 | 71篇 |
2000年 | 72篇 |
1999年 | 52篇 |
1998年 | 26篇 |
1997年 | 30篇 |
1996年 | 19篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有5569条查询结果,搜索用时 15 毫秒
31.
Man Il Kim Jee Yeon Baek Min Jee Kim Heon Cheon Jeong Ki-Gyoung Kim Chang Hwan Bae Yeon Soo Han Byung Rae Jin Iksoo Kim 《Molecules and cells》2009,28(4):347-363
The 15,389-bp long complete mitogenome of the endangered red-spotted apollo butterfly, Parnassius bremeri (Lepidoptera: Papilionidae) was determined in this study. The start codon for the COI gene in insects has been extensively discussed, and has long remained a matter of some controversy. Herein, we propose that the CGA (arginine) sequence functions as the start codon for the COI gene in lepidopteran insects, on the basis of complete mitogenome sequences of lepidopteran insects, including P. bremeri, as well as additional sequences of the COI start region from a diverse taxonomic range of lepidopteran species (a total of 53 species from 15 families). In our extensive search for a tRNA-like structure in the A+T-rich region, one tRNATrp-like sequence and one tRNALeu (UUR)-like sequence were detected in the P. bremeri A+T-rich region, and one or more tRNA-like structures were detected in the A+T-rich region of the majority of other sequenced lepidopteran insects, thereby indicating that such features occur frequently in the lepidopteran mitogenomes. Phylogenetic analysis using the concatenated 13 amino acid sequences and nucleotide sequences of PCGs of the four macrolepidopteran superfamilies together with the Tortricoidea and Pyraloidea resulted in the successful recovery of a monophyly of Papilionoidea and a monophyly of Bombycoidea. However, the Geometroidea were unexpectedly identified as a sister group of the Bombycoidea, rather than the Papilionoidea. 相似文献
32.
The increasing problem of antibiotic resistance among pathogenic bacteria requires development of new antimicrobial agents. For the purpose of this study, a cDNA encoding hinnavin II‐α‐melanocyte stimulating hormone (hin/MSH) hybrid was chemically synthesized, annealed, and then cloned into transfer vector pBacPAK 9 for expression in Sf21 insect cells. Recombinant hin/MSH (rhin/MSH) hybrid was efficiently produced in baculovirus expression vector system (BEVS) as a hybrid peptide. The antibacterial activity of the rhin/MSH hybrid was compared to that of the recombinant hinnavin II (rhin), using inhibition zone and overlay assay. This new recombinant hybrid peptide may serve as an attractive candidate for powerful novel class of antimicrobial pharmaceuticals. 相似文献
33.
The diguanylate cyclase 1 (DGC1) (dgc1) gene in Acetobacter xylinum BPR 2001—a bacterial cellulose (BC) producer—was cloned and sequenced, and a DGC1 gene-disrupted mutant, strain DD, was constructed. The production and structural characteristics of the BC formed by DD were compared with those of the parental strain BPR 2001. BC production by DD was almost the same as that by BPR 2001 in static cultivation and in shake flask cultivation. However, in a jar fermentor DD produced about 36% more BC than the parental strain. DD produced suspended particle materials that cannot aggregate owing to their random structural characteristics in static cultivation; more uniformly dispersed BC pellicles and smaller BC pellets are produced on average in a jar fermentor, as reflected by the higher BC production by DD than by the parental strain in a jar fermentor. Micrographs of BC produced by DD revealed that the width of cellulose ribbons assemblies decreased as a result of differences in the ultrastructure and mechanism of formation of BC between the two strains. These results reveal that disruption of the dgc1 gene, which catalyzes synthesis of c-di-GMP (an effector of BC synthase), is not fatal for BC synthesis, although it affects BC structure. 相似文献
34.
Investigation of extended-spectrum beta-lactamases produced by clinical isolates of Klebsiella pneumoniae and Escherichia coli in Korea 总被引:2,自引:0,他引:2
Jeong SH Bae IK Kwon SB Lee JH Jung HI Song JS Jeong BC Kim SJ Lee SH 《Letters in applied microbiology》2004,39(1):41-47
AIMS: Isolates obtained from various regions in Korea in 2002 were identified and their susceptibility to extended-spectrum cephalosporins, monobactams and/or cephamycins was studied along with any production of extended-spectrum beta-lactamases (ESBLs). METHODS AND RESULTS: Bacteria identified by the conventional techniques and Vitek GNI card were Klebsiella pneumoniae and Escherichia coli. Using disk diffusion and double-disk synergy tests, we found that 39.2% of strains produced ESBLs. About 52% of isolates transferred resistance to ceftazidime by conjugation. Banding patterns of PCR amplification with the designed primers showed that 837- and 259-bp fragments specific to bla(TEM) genes were amplified in 63.3% of strains. 929- and 231-bp fragments (bla(SHV)), 847- and 520-bp fragments (bla(CMY)), 597- and 858-bp fragments (bla(CTX-M)) were amplified in 61.5, 17.3 and 7.7% of strains respectively. About 51.9% of strains contained more than two types of beta-lactamase genes. Especially, one strain contained bla(TEM), bla(CMY) and bla(CTX-M) genes. SIGNIFICANCE: Resistance mechanisms to beta-lactams, comprising mostly ESBL production, lead to the resistance against even recently developed beta-lactams in enterobacteria, which is now a serious threat to antibiotic therapy. The high prevalence of bla(CMY) genes and multidrug-resistant genes may also make therapeutic failure and lack of eradiation of these strains by extended-spectrum cephalosporins or cephamycins. 相似文献
35.
Lee Gap Ryol Kim Se Nyun Noguchi Kohei Park Sang Dai Hong Seung Hwan Cho-Chung Yoon S. 《Molecular and cellular biochemistry》1999,195(1-2):77-86
Expression of the RI regulatory subunit of protein kinase A type I is increased in human cancer cell lines, in primary tumors, in cells after transformation, and in cells upon stimulation of growth. Ala99 (the pseudophosphorylation site) of human RI was replaced with Ser (RI-p) for the structure-function analysis of RI. MCF-7 hormone- dependent breast cancer cells were transfected with an expression vector for the wild-type RI or mutant RI-p. Overexpression of RI-P resulted in suppression of protein kinase A type II, the isozyme of type I kinase, production of kinase exhibiting reduced cAMP activation, and inhibition of cell growth showing an increase in G0/G1 phase of the cell cycle and apoptosis. The wild-type RI overexpression had no effect on protein kinase A isozyme distribution or cell growth. Overexpression of protein kinase A type II regulatory subunit, RII, suppressed RI and protein kinase A type I and inhibited cell growth. These results show that the growth of hormone-dependent breast cancer cells is dependent on the functional protein kinase A type I. 相似文献
36.
Hiroyuki Nakamura Jong-Dae Lee Manabu Ueno Yusuke Miyajima Hyun Seung Ban 《NanoBioTechnology》2007,3(2):135-145
High accumulation and selective delivery of boron into tumor tissues are the most important requirements to achieve efficient
neutron capture therapy of cancers. We focused on liposomal boron delivery system to achieve a large amount of boron delivery
to tumor. We succeeded in the synthesis of the double-tailed boron cluster lipids 4a–c and 5a–c, which has a B12H11S-moiety as a hydrophilic function, by S-alkylation of B12H11SH with bromoacetyl and chloroacetocarbamate derivatives of diacylglycerols. Size distribution of liposomes prepared from
the boron cluster lipid 4b, dimyristoylphosphatidylcholine, polyethyleneglycol-conjugated distearoylphosphatidylethanolamine, and cholesterol was determined
as 100 nm in diameter by an electrophoretic light scattering spectrophotometer. Calcein-encapsulation experiments revealed
that these boronated liposomes are stable at 37 °C in fetal bovine serum solution for 24 h. 相似文献
37.
Recently, secretory granule Ca(2+) storage protein chromogranin B (CGB) was shown to be present in the nucleoplasm proper in a complex structure that consists of the inositol 1,4,5-trisphosphate receptor (IP(3)R)/Ca(2+) channels and the phospholipids. Further, the amounts of IP(3)Rs present in the nucleus of bovine chromaffin cells were shown to be comparable to that of the endoplasmic reticulum. Therefore, we investigated here the potential contribution of nuclear CGB on the IP(3)-dependent Ca(2+) mobilization in the nucleus, using both neuroendocrine PC12 and nonneuroendocrine NIH3T3 cells. Chromogranin A (CGA) expression in the NIH3T3 cells, which do not contain intrinsic chromogranins, increased the IP(3)-induced Ca(2+) releases in the nucleus by 45%, while CGB expression in the same cells increased the IP(3)-induced Ca(2+) releases in the nucleus by 80%. Microinjection of IP(3) into the nucleus of CGB-expressing NIH3T3 cells increased the IP(3)-dependent nuclear Ca(2+) mobilization approximately 3-fold, whereas in CGA-expressing cells it remained the same as that of control cells. In contrast, inhibition of CGA expression in PC12 cells by siRNA treatment decreased the IP(3)-induced Ca(2+) releases in the nucleus by 17%, while inhibition of CGB expression decreased the IP(3)-induced Ca(2+) releases in the nucleus by 55%. Microinjection of IP(3) into the nucleus of siCGB-treated PC12 cells decreased the IP(3)-dependent nuclear Ca(2+) mobilization by approximately 75%, whereas in siCGA-treated cells it remained the same as that of control cells. Given the presence of CGB in the nucleus, these results further highlight the critical contribution of nuclear CGB in the IP(3)-induced Ca(2+) release in the nucleus. 相似文献
38.
Seung Young Lee Eunjung Moon Sun Yeou Kim Kang Ro Lee 《Bioorganic & medicinal chemistry letters》2013,23(7):2140-2144
Five new quinic acid derivatives (1–5), together with 10 known quinic acid derivatives (6–15), were isolated from the MeOH extract of Pimpinella brachycarpa (Umbelliferae). Their structures were established on the basis of spectroscopic analyses including extensive 2D NMR studies (COSY, HMQC and HMBC). Isolated compounds 1–15 were evaluated for their inhibitory activities on nitric oxide (NO) production in an activated murine microglial cell line. Compounds 2, 3, 8 and 11 significantly inhibited NO production without high cell toxicity in lipopolysaccharide (LPS)-activated BV-2 cells, a microglia cell line (IC50 = 4.66, 12.52, 9.04 and 12.11 μM, respectively). 相似文献
39.
Yong-Yeon Jo Sang-Wook Kim Sung-Woo Cho Duck-Ho Bae Hyunok Oh 《Cluster computing》2017,20(2):1155-1166
An intuitive way to process the big data efficiently is to reduce the volume of data transferred over the storage interface to a host system. This is the reason that the notion of intelligent SSD (iSSD) was proposed to give processing power to SSD. There is rich literature on iSSD, however, its real implementation has not been provided to the public yet. Most prior work aims to quantify the benefits of iSSD with analytical modeling. In this paper, we first develop on iSSD simulator and present the potential of iSSD in data mining through the iSSD simulator. Our iSSD simulator performs on top of the gem 5 simulator and fully simulates all the processes of data mining algorithms running in iSSD with cycle-level accuracy. Then, we further addresse how to exploit all the computing resources for efficient processing of data mining algorithms. These days, CPU, GPU, and SSD are recently equipped together in most computing environment. If SSD is replaced with iSSD later on, we have a new computing environment where the three computing resources collaborate one another to process big data quite effectively. For this, scheduling is required to decide which computing resource is going to run for which function at which time. In our heterogeneous scheduling, types of computing resources, memory sizes in computing resources, and inter-processor communication times including IO time in SSD are considered. Our scheduling results show that processing in the collaborative environment outperforms that in the traditional one by up to about 10 times. 相似文献
40.
Abstract A new Monte Carlo sampling scheme, namely the Modified Valley Restrained Monte Carlo procedure, is used to obtain the global energy minimum conformations for polypeptides, such as Met-enkephalin and Melittin. For each peptide, we found close agreement with previous results from both theoretical and experimental studies. The simple idea for controlling the step size according to the Valley Function, provides useful suggestions in searching the global energy minimum structures, and furthermore helps solve the multiple minima problem. 相似文献