全文获取类型
收费全文 | 45648篇 |
免费 | 3728篇 |
国内免费 | 4篇 |
出版年
2023年 | 222篇 |
2021年 | 376篇 |
2020年 | 312篇 |
2019年 | 314篇 |
2018年 | 888篇 |
2017年 | 918篇 |
2016年 | 996篇 |
2015年 | 918篇 |
2014年 | 1086篇 |
2013年 | 1911篇 |
2012年 | 3118篇 |
2011年 | 3461篇 |
2010年 | 1797篇 |
2009年 | 1228篇 |
2008年 | 2853篇 |
2007年 | 2915篇 |
2006年 | 2720篇 |
2005年 | 2467篇 |
2004年 | 2353篇 |
2003年 | 2200篇 |
2002年 | 2208篇 |
2001年 | 1515篇 |
2000年 | 1755篇 |
1999年 | 938篇 |
1998年 | 473篇 |
1997年 | 367篇 |
1996年 | 436篇 |
1995年 | 372篇 |
1994年 | 403篇 |
1993年 | 353篇 |
1992年 | 367篇 |
1991年 | 302篇 |
1990年 | 274篇 |
1989年 | 262篇 |
1988年 | 250篇 |
1987年 | 252篇 |
1986年 | 215篇 |
1985年 | 311篇 |
1984年 | 367篇 |
1983年 | 338篇 |
1982年 | 310篇 |
1981年 | 299篇 |
1980年 | 263篇 |
1979年 | 262篇 |
1978年 | 262篇 |
1977年 | 244篇 |
1976年 | 239篇 |
1975年 | 288篇 |
1974年 | 213篇 |
1973年 | 199篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Johannes Schwerk Mario K?ster Hansj?rg Hauser Manfred Rohde Marcus Fulde Mathias W. Hornef Tobias May 《PloS one》2013,8(8)
Cell lines derived from the small intestine that reflect authentic properties of the originating intestinal epithelium are of high value for studies on mucosal immunology and host microbial homeostasis. A novel immortalization procedure was applied to generate continuously proliferating cell lines from murine E19 embryonic small intestinal tissue. The obtained cell lines form a tight and polarized epithelial cell layer, display characteristic tight junction, microvilli and surface protein expression and generate increasing transepithelial electrical resistance during in vitro culture. Significant up-regulation of Cxcl2 and Cxcl5 chemokine expression upon exposure to defined microbial innate immune stimuli and endogenous cytokines is observed. Cell lines were also generated from a transgenic interferon reporter (Mx2-Luciferase) mouse, allowing reporter technology-based quantification of the cellular response to type I and III interferon. Thus, the newly created cell lines mimic properties of the natural epithelium and can be used for diverse studies including testing of the absorption of drug candidates. The reproducibility of the method to create such cell lines from wild type and transgenic mice provides a new tool to study molecular and cellular processes of the epithelial barrier. 相似文献
62.
Delia V?rg? Petru Lucian Cur?eu Lauren?iu Maricu?oiu Florin A. Sava Irina Macsinga Silvia M?gurean 《PloS one》2014,9(11)
This study seeks to explore whether neuroticism, agreeableness, and conscientiousness moderate the influence of relationship conflict experienced in groups on changes in group members'' evaluative cognitions related to teamwork quality (teamwork-related mental models). Data from 216 students, nested in 48 groups were analyzed using a multilevel modeling approach. Our results show that the experience of relationship conflict leads to a negative shift from the pre-task to the post-task teamwork-related mental models. Moreover, the results indicate that conscientiousness buffered the negative association between relationship conflict and the change in teamwork-related mental models. Our results did not support the hypothesized moderating effect of agreeableness and show that the detrimental effect of relationship conflict on the shift in teamwork-related mental models is accentuated for group members scoring low rather than high on neuroticism. These findings open new research venues for exploring the association between personality, coping styles and change in teamwork-related mental models. 相似文献
63.
64.
65.
Continuous coenzyme dependent stereoselective synthesis of sulcatol by alcohol dehydrogenase 总被引:2,自引:0,他引:2
Summary 6-methyl-5-hepten-2-one was reduced to sulcatol ((+)-6-methyl-5-hepten-2-ol) by using alcohol dehydrogenase fromThermoanaerobium brockii in a continuous process. The cofactor NADP(H) was retained by a charged UF-membrane and regenerated by oxidation of isopropanol to acetone. Use of native NADP in a charged UF-membrane reactor proved to be superior to use of PEG coupled NADP in a uncharged UF-membrane reactor. 相似文献
66.
67.
68.
Summary Saruplase — a recombinant single-chain urokinase-type plasminogen activator was identified immunohistochemically in normal rat tissue after intravenous administration by means of a polyclonal antibody. For this purpose, rat tissues were fixed in various ways (liquid nitrogen, ethanol, formaldehyd solution). Saruplase could be detected by the PAP method, streptavidinbiotin system and indirect immunofluorescence in the kidney (proximal tubule), liver (hepatocytes, Kupffer cells) and spleen (reticular cells). Saruplase was not localized in the rat endothelium. It is discussed that the ratspecific receptors for urokinase-type plasminogen activator on endothelial cells cannot bind Saruplase due to the extreme species specificity. 相似文献
69.
1. Ecosystem processes depend on the biomass of the involved organisms, but their functional diversity may play an additional role. In particular, the exclusion of key functional groups through habitat disturbance may lead to the breakdown of ecosystem functions. Dung removal is an important process contributing to nutrient cycling and thus productivity in grazed ecosystems. 2. This study investigated the role of different functional groups of dung beetles in dung removal in different habitats within a wood-pasture in two different seasons. An experimental setting with 12 blocks and 108 dung pads was used to investigate short-term dung removal over 1 week of exposure. 3. Dung removal was most strongly affected by habitat type, with almost 40% lower levels in grassland than in adjacent forest and forest gaps. Of all assemblage characteristics, total biomass of tunneller species was the strongest predictor of dung removal, whereas functional diversity showed no significant effect. In accordance with the dung removal pattern at habitat type level, densities of large tunnellers were suppressed in grassland compared with forest. 4. It is concluded that dung removal is habitat-specific and large tunnellers play a disproportionate role in this important ecosystem function in temperate forests. 相似文献
70.