全文获取类型
收费全文 | 2291篇 |
免费 | 260篇 |
国内免费 | 617篇 |
专业分类
3168篇 |
出版年
2024年 | 13篇 |
2023年 | 58篇 |
2022年 | 103篇 |
2021年 | 127篇 |
2020年 | 117篇 |
2019年 | 129篇 |
2018年 | 109篇 |
2017年 | 105篇 |
2016年 | 115篇 |
2015年 | 164篇 |
2014年 | 167篇 |
2013年 | 183篇 |
2012年 | 200篇 |
2011年 | 200篇 |
2010年 | 147篇 |
2009年 | 151篇 |
2008年 | 168篇 |
2007年 | 145篇 |
2006年 | 145篇 |
2005年 | 84篇 |
2004年 | 78篇 |
2003年 | 79篇 |
2002年 | 74篇 |
2001年 | 58篇 |
2000年 | 41篇 |
1999年 | 43篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1968年 | 2篇 |
1957年 | 2篇 |
1954年 | 2篇 |
1950年 | 2篇 |
排序方式: 共有3168条查询结果,搜索用时 15 毫秒
1.
2.
QIAN‐WAN MENG YI‐BO LUO 《Botanical journal of the Linnean Society. Linnean Society of London》2008,158(4):689-695
A new species, Galearis huanglongensis Q.W.Meng & Y.B.Luo, is described and illustrated. It is similar to Galearis cyclochila (Franch. & Sav.) Soó and Galearis diantha (Schltr.) P.F.Hunt, but differs in having a short spur, two elliptical lateral stigma lobes and distinctly separated bursicles. This new species is known only from the type locality, the Huanglong Valley, Songpan County, western Sichuan, China, growing amongst mosses under alpine shrubs at an elevation of about 3000 m. Based on two years of observations of its population size, the species was categorized as critically endangered CR (B1a, B2a) according to the World Conservation Union (IUCN) Red List Categories and Criteria, Version 3.1. The micromorphology of pollinia and seeds was observed by scanning electron microscopy and compared with that of G. cyclochila and G. diantha. The results supported G. huanglongensis Q.W.Meng & Y.B.Luo as a new species. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 689–695. 相似文献
3.
The mechanism of mass collaboration in risk management was studied during the Sichuan earthquake under a Web-based “PeopleFinder” project, where information is contributed and shared among mass contributors. The case study is provided by a great earthquake that happened in Wenchuan County, Sichuan Province, of southwestern China at 2:28 p.m. on May 12, 2008. We witnessed and experienced the rescue and relief efforts for the great earthquake. In this article, two fundamental frameworks are developed to study the mechanism of mass collaboration. Mass collaboration is proven to be effective in a big public crisis such as the Sichuan earthquake. 相似文献
4.
A G Chuchalin V A Babushkina V Ia Arion R D Aspetov T B Sha?khinova 《Biulleten' eksperimental'no? biologii i meditsiny》1984,98(7):76-78
A study was made of the effect of T-activin on the biosynthesis of immune gamma-interferon. It was shown that in 27% of patients with chronic nonspecific pulmonary diseases, production of gamma-interferon by lymphocytes was substantially reduced during exacerbation of inflammatory process in the lungs. It was discovered that T-activin was not an interferon inductor but enhanced its synthesis in patients with a low capacity of producing immune interferon even at small doses of interferon inductor. The preparation does not produce any effect on this process in normal subjects and in patients showing the normal level of gamma-interferon. Thus T-activin can be used for stimulation of interferonogenesis. 相似文献
5.
6.
7.
Brucella abortus catalase is a periplasmic protein lacking a standard signal sequence. 总被引:3,自引:2,他引:1 下载免费PDF全文
A periplasmic catalase has been purified and cloned from Brucella abortus. The functional enzyme is a tetramer with a subunit molecular weight of 55,000. All evidence indicates that a typical N-terminal signal sequence is not associated with the export of this protein to the periplasm. 相似文献
8.
渗透胁迫对高粱根K~+吸收的影响 总被引:4,自引:0,他引:4
以CaSO40.5mmolL-1溶液培养高粱得到低钾植株,在渗透胁迫下当PEG-1000使外界渗透势下降时,刺激了高粱根高K+亲和系统的净K+积累,其表观Km值和Tmax值分别为18μmolL-1和49.6μmolg-1DWh-1。此高亲和系统不受可渗物质乙二醇和外界pH变化的影响,为蛋白质合成抑制剂环己酰亚胺抑制。 相似文献
9.
Identification and analysis of discrete functional domains in the pro region of pre-pro-transforming growth factor beta 1 总被引:3,自引:0,他引:3 下载免费PDF全文
A series of site-specific insertion and deletion mutants was prepared in the pro domain of transforming growth factor beta 1 (TGF beta 1) encoded by simian TGF beta 1 cDNA. These mutants were transiently expressed in COS-1 cells and the ability of each to be properly processed, folded correctly, and secreted was determined by immunoblot analysis of cells and culture supernatants. Insertions in regions corresponding to amino acid residues 50, 154, and 170 blocked secretion; culture supernatants from COS-1 cells showed no immunologically reactive proteins, whereas intact cells contained high levels of the mutant polypeptides. Insertions in the middle portion of the pro domain at residues 81, 85, and 144 affected disulfide maturation of the mature TGF beta 1. An insertion at residue 110, on the other hand, appeared to destabilize the mature TGF beta 1 polypeptide, resulting in degraded growth factor. Relatively small (10 amino acids) to large (125 amino acids) deletion mutations in the pro domain of TGF beta 1, when expressed as the full-length pre-pro-TGF beta 1, appeared to block secretion. By contrast, if the pro domain (designated beta 1-latency-associated peptide [beta 1-LAP]) was expressed independently, deletion mutants in the region 40-110 were readily secreted by the COS-1 cells, whereas deletions in residues 110-210 either destabilized the structure of the protein or blocked its intracellular transport. Cross-linking assays employing radioiodinated TGF beta 1 and biological assays indicate that residues 50-85 of beta 1-LAP are required for association with mature TGF beta 1. 相似文献
10.