全文获取类型
收费全文 | 8442篇 |
免费 | 614篇 |
国内免费 | 5篇 |
专业分类
9061篇 |
出版年
2023年 | 43篇 |
2022年 | 93篇 |
2021年 | 195篇 |
2020年 | 130篇 |
2019年 | 123篇 |
2018年 | 181篇 |
2017年 | 149篇 |
2016年 | 281篇 |
2015年 | 401篇 |
2014年 | 461篇 |
2013年 | 570篇 |
2012年 | 693篇 |
2011年 | 712篇 |
2010年 | 439篇 |
2009年 | 379篇 |
2008年 | 495篇 |
2007年 | 515篇 |
2006年 | 504篇 |
2005年 | 417篇 |
2004年 | 382篇 |
2003年 | 302篇 |
2002年 | 333篇 |
2001年 | 77篇 |
2000年 | 56篇 |
1999年 | 58篇 |
1998年 | 89篇 |
1997年 | 36篇 |
1996年 | 51篇 |
1995年 | 52篇 |
1994年 | 49篇 |
1993年 | 48篇 |
1992年 | 40篇 |
1991年 | 40篇 |
1990年 | 32篇 |
1989年 | 38篇 |
1988年 | 33篇 |
1987年 | 43篇 |
1986年 | 29篇 |
1985年 | 39篇 |
1984年 | 36篇 |
1983年 | 46篇 |
1982年 | 34篇 |
1981年 | 35篇 |
1980年 | 23篇 |
1979年 | 23篇 |
1978年 | 19篇 |
1977年 | 34篇 |
1976年 | 20篇 |
1973年 | 14篇 |
1964年 | 14篇 |
排序方式: 共有9061条查询结果,搜索用时 0 毫秒
81.
Schroeder CP Goeldner EM Schulze-Forster K Eickhoff CA Holtermann P Heidecke H 《Biological trace element research》2004,99(1-3):17-25
Selenite is frequently used in combination with cancer chemotherapeutic agents to reduce side effects. However, the cytoprotective
activity of selenite may also reduce the efficacy of chemotherapeutic drugs on tumor cells. This study was designed to examine
the effects of selenite combined with cytotoxic agents used in clinical protocols [e.g., doxorubicine, docetaxel, 5-fluorouracil
(5-FU), methotrexate (MTX), mafosphamide, mitomycin C, gemcitabine, etoposide, cisplatin, irinotecan, and oxaliplatin] on
the proliferation of various carcinoma cell types. The data demonstrated that selenite had no marked effects on the antiproliferative
activity of docetaxel, doxorubicine, 5-FU, MTX, and mafosphamide in MDA-MB-231 breast cancer cells. Likewise, no consistent
changes were observed in A549 lung cancer cell proliferation when selenite was combined with cisplatin, etoposide, gemcitabine,
or mitomycin C. On the other hand, selenite potentiated the cytotoxicity of 5-FU, oxaliplatin, and irinotecan in HCT116 colon
cancer cells by approx 1.1-fold, 2.7-fold, and 2.6-fold, respectively. In SW620 colon cancer cells, selenite induced a 1.5-fold
and 4.3-fold increase of the antiproliferative activity of 5-FU and oxaliplatin, respectively. Whereas irinotecan showed no
effects on SW620 cell growth, a combination with selenite resulted in 23% inhibition. Our results indicate that selenite did
not reduce the antiproliferative activity of chemotherapeutic agents in vitro. In addition, selenite was able to increase
the inhibitory activity of docetaxel in A549 lung cancer cells, and of 5-FU, oxaliplatin, and irinotecan in HCT116 and SW620
colon cancer cells implying selenite is potentially useful as an adjuvant chemotherapeutic agent. 相似文献
82.
Intercalibrations of phytoplankton countings were made in the Baltic in 1974 and 1975, where seven laboratories participated, each using their routine method. A statistical evaluation was made on the results, and recommendations for routine countings with the Utermöhl technique are given. 相似文献
83.
Eva Purkey 《CMAJ》2004,171(6):618-619
84.
Von Hippel and colleagues have highlighted the crucial role of users in innovation in different industries and types of products. They describe the innovation process in terms of the distinct domains of knowledge that producers and users possess. Producers have knowledge about technical solutions and users about their needs, the context of use, and their own capabilities as users. Both sets of knowledge are characterized by "stickiness": They move relatively freely within their own domain but are difficult to transfer outside of it.
In the case of radical innovations for sustainable consumption, the problem of "sticky information" is compounded. Both producers and consumers need to reach out of their conventional competencies and search for new solutions. "Societal actors," such as government bodies or environmental experts, can show the way to such solutions, but this new knowledge needs to be integrated with the "sticky" knowledge about everyday practices in production and consumption.
In the present article we attempt to conceptualize the role and interaction of user and producer knowledge with the knowledge of environmental experts in housing energy innovations. We do so by applying the user−producer interaction framework to a case study on the introduction of low-energy housing concepts in Finland. On the basis of this analysis, we draw conclusions on the potential and limitations of today's practices in the field. For example, we suggest that user involvement can help to enhance the acceptance of low-energy solutions but that the methods for involving users need to be adapted to the particular circumstances in each industry. 相似文献
In the case of radical innovations for sustainable consumption, the problem of "sticky information" is compounded. Both producers and consumers need to reach out of their conventional competencies and search for new solutions. "Societal actors," such as government bodies or environmental experts, can show the way to such solutions, but this new knowledge needs to be integrated with the "sticky" knowledge about everyday practices in production and consumption.
In the present article we attempt to conceptualize the role and interaction of user and producer knowledge with the knowledge of environmental experts in housing energy innovations. We do so by applying the user−producer interaction framework to a case study on the introduction of low-energy housing concepts in Finland. On the basis of this analysis, we draw conclusions on the potential and limitations of today's practices in the field. For example, we suggest that user involvement can help to enhance the acceptance of low-energy solutions but that the methods for involving users need to be adapted to the particular circumstances in each industry. 相似文献
85.
Verónica Corrales-Sánchez María del Mar Noblejas-López Cristina Nieto-Jiménez Javier Pérez-Peña Juan Carlos Montero Miguel Burgos Eva M. Galán-Moya Atanasio Pandiella Alberto Ocaña 《Journal of cellular and molecular medicine》2020,24(5):3117-3127
Identification of druggable vulnerabilities is a main objective in triple-negative breast cancer (TNBC), where no curative therapies exist. Gene set enrichment analyses (GSEA) and a pharmacological evaluation using a library of compounds were used to select potential druggable combinations. MTT and studies with semi-solid media were performed to explore the activity of the combinations. TNBC cell lines (MDAMB-231, BT549, HS-578T and HCC3153) and an additional panel of 16 cell lines were used to assess the activity of the two compounds. Flow cytometry experiments and biochemical studies were also performed to explore the mechanism of action. GSEA were performed using several data sets (GSE21422, GSE26910, GSE3744, GSE65194 and GSE42568), and more than 35 compounds against the identified functions were evaluated to discover druggable opportunities. Analyses done with the Chou and Talalay algorithm confirmed the synergy of dasatinib and olaparib. The combination of both agents significantly induced apoptosis in a caspase-dependent manner and revealed a pleotropic effect on cell cycle: Dasatinib arrested cells in G0/G1 and olaparib in G2/M. Dasatinib inhibited pChk1 and induced DNA damage measured by pH2AX, and olaparib increased pH3. Finally, the effect of the combination was also evaluated in a panel of 18 cell lines representative of the most frequent solid tumours, observing a particularly synergism in ovarian cancer. Breast cancer, triple negative, dasatinib, olaparib, screening. 相似文献
86.
Matthias Albrecht David Kleijn Neal M. Williams Matthias Tschumi Brett R. Blaauw Riccardo Bommarco Alistair J. Campbell Matteo Dainese Francis A. Drummond Martin H. Entling Dominik Ganser G. Arjen de Groot Dave Goulson Heather Grab Hannah Hamilton Felix Herzog Rufus Isaacs Katja Jacot Philippe Jeanneret Mattias Jonsson Eva Knop Claire Kremen Douglas A. Landis Gregory M. Loeb Lorenzo Marini Megan McKerchar Lora Morandin Sonja C. Pfister Simon G. Potts Maj Rundlf Hillary Sardias Amber Sciligo Carsten Thies Teja Tscharntke Eric Venturini Eve Veromann Ines M.G. Vollhardt Felix Wckers Kimiora Ward Andrew Wilby Megan Woltz Steve Wratten Louis Sutter 《Ecology letters》2020,23(10):1488-1498
Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future. 相似文献
87.
The mutualism between chemical cues emitted into the air and variations in how primates respond to them using olfaction has demonstrated aspects of species‐specific adaptations. Building on this mutualism we can look at particle deposition as another means to understanding how various environments may have elicited biological changes that enable efficient communication. Research on particle movement and deposition within the nasal cavity is largely based on questions about health as it relates to drug delivery systems and overall olfactory function in modern humans. With increased access to 3D models and the use of computational fluid dynamic analysis, researchers have been able to simulate site‐specific deposition, to determine what particles are making it through the nasal cavity to the main olfactory epithelium, which ultimately leads to processing in the olfactory bulb. Here we discuss particle deposition research, sensory drive and their potential applications to evolutionary anthropology. 相似文献
88.
Vollset Knut Wiik Lennox Robert J. Thorstad Eva B. Auer Samuel Bär Kerstin Larsen Martin H. Mahlum Shad Näslund Joacim Stryhn Henrik Dohoo Ian 《Reviews in Fish Biology and Fisheries》2020,30(4):553-568
Reviews in Fish Biology and Fisheries - A systematic review and meta-analysis was conducted to evaluate the appropriate tag:fish size ratio when tagging juvenile salmonids (genera Oncorhynchus,... 相似文献
89.
Cointet Eva Séverin Elise Couzinet-Mossion Aurélie Méléder Vona Gonçalves Olivier Wielgosz-Collin Gaëtane 《Journal of applied phycology》2021,33(4):2093-2103
Journal of Applied Phycology - In recent years diatoms have emerged as a major algal source for the production of bioactive compounds. Marine diatoms grow quickly and can store high amount of... 相似文献
90.
Ptáková Michaela Pokorný Petr Šída Petr Novák Jan Horáček Ivan Juřičková Lucie Meduna Petr Bezděk Aleš Myšková Eva Walls Matthew Poschlod Peter 《Vegetation History and Archaeobotany》2021,30(2):269-286
Vegetation History and Archaeobotany - In a continuous, perfectly stratified sedimentary sequence which was discovered under a large sandstone overhang in northern Bohemia, Czech Republic, we... 相似文献