全文获取类型
收费全文 | 5334篇 |
免费 | 879篇 |
国内免费 | 1044篇 |
出版年
2023年 | 187篇 |
2022年 | 147篇 |
2021年 | 269篇 |
2020年 | 406篇 |
2019年 | 422篇 |
2018年 | 348篇 |
2017年 | 367篇 |
2016年 | 359篇 |
2015年 | 314篇 |
2014年 | 331篇 |
2013年 | 370篇 |
2012年 | 276篇 |
2011年 | 255篇 |
2010年 | 243篇 |
2009年 | 281篇 |
2008年 | 242篇 |
2007年 | 291篇 |
2006年 | 260篇 |
2005年 | 223篇 |
2004年 | 175篇 |
2003年 | 175篇 |
2002年 | 162篇 |
2001年 | 138篇 |
2000年 | 132篇 |
1999年 | 110篇 |
1998年 | 100篇 |
1997年 | 83篇 |
1996年 | 59篇 |
1995年 | 72篇 |
1994年 | 49篇 |
1993年 | 55篇 |
1992年 | 47篇 |
1991年 | 37篇 |
1990年 | 33篇 |
1989年 | 28篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 9篇 |
1982年 | 25篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有7257条查询结果,搜索用时 31 毫秒
81.
82.
《Molecular cell》2021,81(16):3294-3309.e12
83.
84.
This article examines an important class of information system that serves as the foundation for corporate energy and greenhouse gas (GHG) accounting: energy and carbon management systems (ECMS). Investors, regulators, customers, and employees increasingly demand that organizations provide information about their organizational energy use and GHG emissions. However, there is little transparency about how organizations use ECMS to meet such demands. To shed light on ECMS implementation and application, we collected extensive qualitative interview data from two service‐sector organizations: one that uses a spreadsheet‐based ECMS and another that implemented an ECMS provided by a third‐party vendor. Our analysis of collected data revealed numerous challenges in the areas of business processes, managerial capabilities, data capture and integration, and data quality. Though our study is built on only two organizations and requires confirmation in large‐sample surveys, we provide several recommendations for organizations regarding ECMS. We also provide suggestions for future studies to build on our tentative results. 相似文献
85.
L. Pesciaroli M. Petruccioli F. Federici A. D'Annibale 《Journal of applied microbiology》2013,114(6):1750-1762
Aims
To investigate the effect of support and growth medium (GM) on Pleurotus ostreatus biofilm production, specific metabolic activity (SMA) and ultrastructure.Methods and Results
Biofilms were developed on membranes covering a broad range of surface properties and, due to the applicative implications of mixed biofilms, on standard bacterial GM in stationary and shaken culture. Hydrophilic (glass fibre, Duran glass and hydroxyapatite) and mild hydrophobic (polyurethane, stainless steel, polycarbonate, nylon) supports were more adequate for biofilm attachment than the hydrophobic Teflon. Among the GM, sucrose–asparagine (SA) was more conducive to biofilm production than Luria–Bertani and M9. GM was more influential than support type on biofilm ultrastructure, and a high compactness was evident in biofilms developed on SA. Biofilms on Duran glass were more efficient than planktonic cultures in olive‐mill wastewater treatment.Conclusions
The main effects of support and GM variables and their binary interactions on both biofilm production and SMA were all highly significant (P < 0·001): thus, the magnitude of the effect of each variable strongly depended on the level of the other one.Significance and Impact of the Study
There is a lack of basic information regarding physiology and ultrastructure of P. ostreatus biofilms. To our knowledge, this is the first attempt to fill this gap, thus representing a basis for future studies. 相似文献86.
K.-H. Hsu P. Brandt-Rauf T.-M. Lin H.-Y. Chiou C.-H. Tseng C.-J. Chen 《Biomarkers》2013,18(6):538-546
AbstractEpidemiological studies have demonstrated an association between long-term exposure to inorganic arsenic and the related adverse effects such as cancers, skin lesions, and vascular diseases. Although several hypotheses have been proposed for the mechanism of arsenic-induced pathogenesis, it remains imperfectly understood. Recent studies have suggested that alterations in growth signal transduction pathways, particularly involving transforming growth factor-alpha (TGF-alpha), may be important. Immunoassays were used to determine the plasma levels of TGF-alpha and epidermal growth factor receptor (EGFR), which is the receptor for TGF-alpha, in residents of an arseniasis area of Taiwan in relation to their estimated cumulative arsenic exposure from drinking water. No relationship between arsenic exposure and EGFR was found. However, among the high cumulative exposure group (>6 ppm-years), levels of plasma TGF-alpha (25.5±38.2 pg ml?1) and the proportion of individuals with TGF-alpha over-expression (29.4%) were significantly higher (p<0.05) than normal, healthy unexposed controls (8.1±5.6 pg ml?1, 8.6%, respectively). There was a significant linear trend between cumulative arsenic exposure and the prevalence of plasma TGF-alpha over-expression after adjusting for age and sex (p=0.019). The results suggest that plasma TGF-alpha expression may be a useful biomarker when detecting adverse effects on arsenic exposed population. 相似文献
87.
88.
《Biomarkers》2013,18(5):393-404
Mutagen sensitivity, measured in short-term cultures of peripheral blood lymphocytes by cytogenetic endpoints, is an indirect measure for DNA repair capacity and has been used for many years as a biomarker for intrinsic susceptibility for cancer. In this article, we briefly give an overview of the different cytogenetic mutagen sensitivity approaches that have been used successfully to evaluate the biological effects of polymorphisms in DNA repair genes based on a current review of the literature and based on the need for biomarkers that would allow the characterization of the biological and functional significance of such polymorphisms. We also address some of the future challenges facing this emerging area of research. 相似文献
89.
This article examines the relationship between trust and risk in one of the centres of the global chemical industry, Ludwigshafen in Germany. A single industry town associated for 150 years with BASF, the dominant outlook among those living or working there has been one of trust, confidence and pride in the corporation which has ‘put the town on the map’. Yet beneath the surface, subtle shifts in public assumptions and expectations about BASF and the town's chemical industry are now occurring. We describe the parameters of public reflection about trust and risk, analyse how characterizations of BASF are changing, and consider how far recent writing on trust helps in understanding its salience in this particular industrial town. 相似文献
90.
《Journal of Plant Interactions》2013,8(2):125-134
Abstract The Bioregenerative Life Support program CAB (Controllo Ambientale Biorigenerativo) is a key element of the Italian Space Agency (ASI) Medicine & Biotechnology scientific program, set forth in the ASI Activity Plan 2006–2008. The CAB program started in October 2006, under the prime partnership of Thales Alenia Space Italia, with a feasibility study of a controlled biological system, allowing the regeneration of resources and the production of food for life support in long duration missions. Main constituents of the CAB program are: (a) Higher plants as basic elements for food and oxygen production, CO2 regeneration and water purification via the photosynthetic and leaf transpiration processes, and (b) biological & physico-chemical systems for environmental control, monitoring, power & data distribution, etc. The sectors of technological and scientific concern are practically all the ones typical for life support systems in the frame of long duration human missions; i.e., food production, in particular via the cultivation of higher plants, and food management; air regeneration (production of O2, removal of CO2, trace gas control); water regeneration (urine processing, gray water processing, potable water management); solid waste processing; resources allocation and storage; control of environmental conditions (Thermal-hygrometric, light, pressure, radiation, etc). 相似文献