全文获取类型
收费全文 | 282篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
系统科学 | 1篇 |
丛书文集 | 1篇 |
教育与普及 | 3篇 |
理论与方法论 | 1篇 |
现状及发展 | 51篇 |
研究方法 | 33篇 |
综合类 | 161篇 |
自然研究 | 33篇 |
出版年
2021年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2012年 | 9篇 |
2011年 | 42篇 |
2010年 | 2篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 1篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1970年 | 7篇 |
1969年 | 1篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1966年 | 7篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有284条查询结果,搜索用时 359 毫秒
201.
Veverka J Farquhar B Robinson M Thomas P Murchie S Harch A Antreasian PG Chesley SR Miller JK Owen WM Williams BG Yeomans D Dunham D Heyler G Holdridge M Nelson RL Whittenburg KE Ray JC Carcich B Cheng A Chapman C Bell JF Bell M Bussey B Clark B Domingue D Gaffey MJ Hawkins E Izenberg N Joseph J Kirk R Lucey P Malin M McFadden L Merline WJ Peterson C Prockter L Warren J Wellnitz D 《Nature》2001,413(6854):390-393
The NEAR-Shoemaker spacecraft was designed to provide a comprehensive characterization of the S-type asteroid 433 Eros (refs 1,2,3), an irregularly shaped body with approximate dimensions of 34 x 13 x 13 km. Following the completion of its year-long investigation, the mission was terminated with a controlled descent to its surface, in order to provide extremely high resolution images. Here we report the results of the descent on 12 February 2001, during which 70 images were obtained. The landing area is marked by a paucity of small craters and an abundance of 'ejecta blocks'. The properties and distribution of ejecta blocks are discussed in a companion paper. The last sequence of images reveals a transition from the blocky surface to a smooth area, which we interpret as a 'pond'. Properties of the 'ponds' are discussed in a second companion paper. The closest image, from an altitude of 129 m, shows the interior of a 100-m-diameter crater at 1-cm resolution. 相似文献
202.
203.
204.
Growth induced by pulsatile infusion of an amidated fragment of human growth hormone releasing factor in normal and GHRF-deficient rats 总被引:1,自引:0,他引:1
The discovery of human pancreatic growth hormone releasing factors (GHRFs) and subsequent characterization of human hypothalamic GHRF has led to studies on the role of these peptides in stimulating growth hormone (GH) release, and attempts to use GHRF peptides to increase growth rates in short children are already underway. However, there is no experimental evidence in animals that exogenous GHRF promotes growth in vivo. Although anaesthetized rats release GH reproducibly in response to GHRF injections, the responses in conscious male rats are much more variable, perhaps because of their highly episodic endogenous GH secretory pattern. In contrast, female rats secrete GH in a more continuous pattern and respond reproducibly to repeated injections of GHRF. We report here that it is possible to establish a 'male' type of GH secretory pattern in normal female rats by long-term pulsatile intravenous (i.v.) infusions of the active human GHRF fragment GHRF (1-29)NH2. We found that this treatment accelerates growth and increases pituitary GH content, whereas continuous infusions of this GHRF fragment at the same daily dose are ineffective. Pulsatile, but not continuous GHRF also stimulates growth in animals made GHRF-deficient by neonatal monosodium glutamate treatment. Thus exogenous GHRF will stimulate growth in both GHRF-deficient and normal animals provided it is administered in an appropriate pattern. 相似文献
205.
206.
207.
Reshaping human antibodies for therapy 总被引:76,自引:0,他引:76
A human IgGI antibody has been reshaped for serotherapy in humans by introducing the six hypervariable regions from the heavy- and light-chain variable domains of a rat antibody directed against human lymphocytes. The reshaped human antibody is as effective as the rat antibody in complement and is more effective in cell-mediated lysis of human lymphocytes. 相似文献
208.
Radionuclide deposition from the Chernobyl cloud 总被引:2,自引:0,他引:2
209.
A human T cell-specific cDNA clone encodes a protein having extensive homology to immunoglobulin chains 总被引:15,自引:0,他引:15
We have cloned and sequenced a human mRNA specific for mammalian T-lymphoid cells. The message was found to be expressed in human and murine T lymphoblasts, thymocytes and phytohaemagglutinin-stimulated T lymphocytes. The protein deduced from the cDNA sequence has a molecular weight of 34,938 and shows extensive similarity to the entire length of the variable, joining and constant regions of mammalian immunoglobulin light chains. In addition, the relative positions of the cysteine residues are similar to those of the light chains of murine and human immunoglobulin molecules. These properties suggest that the cDNA clone may correspond to a message that specifies part of the human T-cell receptor. 相似文献
210.