全文获取类型
收费全文 | 3767篇 |
免费 | 252篇 |
专业分类
4019篇 |
出版年
2023年 | 19篇 |
2022年 | 38篇 |
2021年 | 56篇 |
2020年 | 48篇 |
2019年 | 63篇 |
2018年 | 88篇 |
2017年 | 73篇 |
2016年 | 96篇 |
2015年 | 163篇 |
2014年 | 160篇 |
2013年 | 248篇 |
2012年 | 306篇 |
2011年 | 233篇 |
2010年 | 161篇 |
2009年 | 152篇 |
2008年 | 196篇 |
2007年 | 201篇 |
2006年 | 208篇 |
2005年 | 175篇 |
2004年 | 158篇 |
2003年 | 134篇 |
2002年 | 155篇 |
2001年 | 87篇 |
2000年 | 60篇 |
1999年 | 55篇 |
1998年 | 61篇 |
1997年 | 44篇 |
1996年 | 37篇 |
1995年 | 33篇 |
1994年 | 26篇 |
1993年 | 20篇 |
1992年 | 32篇 |
1991年 | 45篇 |
1990年 | 37篇 |
1989年 | 37篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 22篇 |
1984年 | 34篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1978年 | 19篇 |
1977年 | 11篇 |
1976年 | 17篇 |
1975年 | 8篇 |
1974年 | 12篇 |
排序方式: 共有4019条查询结果,搜索用时 15 毫秒
91.
Daesoo Kim Greg Thoma Darin Nutter Franco Milani Rick Ulrich Greg Norris 《The International Journal of Life Cycle Assessment》2013,18(5):1019-1035
Purpose
A life cycle assessment was conducted to determine a baseline for environmental impacts of cheddar and mozzarella cheese consumption. Product loss/waste, as well as consumer transport and storage, is included. The study scope was from cradle-to-grave with particular emphasis on unit operations under the control of typical cheese-processing plants.Methods
SimaPro© 7.3 (PRé Consultants, The Netherlands, 2013) was used as the primary modeling software. The ecoinvent life cycle inventory database was used for background unit processes (Frischknecht and Rebitzer, J Cleaner Prod 13(13–14):1337–1343, 2005), modified to incorporate US electricity (EarthShift 2012). Operational data was collected from 17 cheese-manufacturing plants representing 24 % of mozzarella production and 38 % of cheddar production in the USA. Incoming raw milk, cream, or dry milk solids were allocated to coproducts by mass of milk solids. Plant-level engineering assessments of allocation fractions were adopted for major inputs such as electricity, natural gas, and chemicals. Revenue-based allocation was applied for the remaining in-plant processes.Results and discussion
Greenhouse gas (GHG) emissions are of significant interest. For cheddar, as sold at retail (63.2 % milk solids), the carbon footprint using the IPCC 2007 factors is 8.60 kg CO2e/kg cheese consumed with a 95 % confidence interval (CI) of 5.86–12.2 kg CO2e/kg. For mozzarella, as sold at retail (51.4 % milk solids), the carbon footprint is 7.28 kg CO2e/kg mozzarella consumed, with a 95 % CI of 5.13–9.89 kg CO2e/kg. Normalization of the results based on the IMPACT 2002+ life cycle impact assessment (LCIA) framework suggests that nutrient emissions from both the farm and manufacturing facility wastewater treatment represent the most significant relative impacts across multiple environmental midpoint indicators. Raw milk is the major contributor to most impact categories; thus, efforts to reduce milk/cheese loss across the supply chain are important.Conclusions
On-farm mitigation efforts around enteric methane, manure management, phosphorus and nitrogen runoff, and pesticides used on crops and livestock can also significantly reduce impacts. Water-related impacts such as depletion and eutrophication can be considered resource management issues—specifically of water quantity and nutrients. Thus, all opportunities for water conservation should be evaluated, and cheese manufacturers, while not having direct control over crop irrigation, the largest water consumption activity, can investigate the water use efficiency of the milk they procure. The regionalized normalization, based on annual US per capita cheese consumption, showed that eutrophication represents the largest relative impact driven by phosphorus runoff from agricultural fields and emissions associated with whey-processing wastewater. Therefore, incorporating best practices around phosphorous and nitrogen management could yield improvements. 相似文献92.
93.
Gemma Navarro Estefania Moreno Jordi Bonaventura Marc Brugarolas Daniel Farré David Aguinaga Josefa Mallol Antoni Cortés Vicent Casadó Carmen Lluís Sergi Ferre Rafael Franco Enric Canela Peter J. McCormick 《PloS one》2013,8(4)
Under normal conditions the brain maintains a delicate balance between inputs of reward seeking controlled by neurons containing the D1-like family of dopamine receptors and inputs of aversion coming from neurons containing the D2-like family of dopamine receptors. Cocaine is able to subvert these balanced inputs by altering the cell signaling of these two pathways such that D1 reward seeking pathway dominates. Here, we provide an explanation at the cellular and biochemical level how cocaine may achieve this. Exploring the effect of cocaine on dopamine D2 receptors function, we present evidence of σ1 receptor molecular and functional interaction with dopamine D2 receptors. Using biophysical, biochemical, and cell biology approaches, we discovered that D2 receptors (the long isoform of the D2 receptor) can complex with σ1 receptors, a result that is specific to D2 receptors, as D3 and D4 receptors did not form heteromers. We demonstrate that the σ1-D2 receptor heteromers consist of higher order oligomers, are found in mouse striatum and that cocaine, by binding to σ1 -D2 receptor heteromers, inhibits downstream signaling in both cultured cells and in mouse striatum. In contrast, in striatum from σ1 knockout animals these complexes are not found and this inhibition is not seen. Taken together, these data illuminate the mechanism by which the initial exposure to cocaine can inhibit signaling via D2 receptor containing neurons, destabilizing the delicate signaling balance influencing drug seeking that emanates from the D1 and D2 receptor containing neurons in the brain. 相似文献
94.
Giovanni Lombardi Patrizia Lanteri Pier Luigi Fiorella Luigi Simonetto Franco M. Impellizzeri Marco Bonifazi Giuseppe Banfi Massimo Locatelli 《PloS one》2013,8(4)
Cycling stage races are strenuous endurance events during which exercise-induced variations in hematological parameters are consistently observed. However, specific literature on such changes is scarce and published data have been derived from small samples of athletes. The aims of this study were: (1) to determine the hematological response to middle-term strenuous endurance; and (2) to determine whether a relationship exists between the athlete-specific hematological profile and final placement in a cycling stage race. The study population was male professional cyclists (n = 253) competing in the 2010 (n = 144) and 2012 (n = 109) GiroBio 10-day stage races. Blood draws taken before the start of the race, at mid-race, and at end-race were performed in strict compliance with academic and anti-doping pre-analytical warnings. Blood chemistry included white blood cell, red blood cell, hemoglobin concentration, hematocrit, mean corpuscular volume (MCV), mean hemoglobin content (MCH), mean corpuscular hemoglobin content (MCHC), platelets, and reticulocyte relative and absolute counts. Compared to baseline values, erythrocyte, hemoglobin, hematocrit, MCHC, platelet and reticulocyte counts were all consistently lower at mid-race, but returned to normal by race-end, while leukocytes were increased in the final phase. MCV increased during both events. MCH increased in the first part to then return to baseline in the 2012 race. The calculated OFF-score consistently decreased in the first half of the race before increasing, but remained lower than the baseline value. The trends of variation in hematological parameters were substantially similar in both events. There was an inverse, albeit weak, relationship between placement and erythrocyte, platelet, hemoglobin, hematocrit and OFF-score values in the 2010, but not in the 2012 race. In conclusion, the data confirm that, in this large series of elite road cyclists, the strenuous effort a rider sustains during a stage race induces appreciable changes in the hematological profile. 相似文献
95.
96.
97.
98.
Mehbub Mohammad F. Tanner Jason E. Barnett Stephen J. Franco Christopher M. M. Zhang Wei 《Applied microbiology and biotechnology》2016,100(24):10609-10626
Applied Microbiology and Biotechnology - Sponge-associated bacteria play a critical role in sponge biology, metabolism and ecology, but how they interact with their host sponges and the role of... 相似文献
99.
100.
Tree growth,cambial phenology,and wood anatomy of limber pine at a Great Basin (USA) mountain observatory 总被引:1,自引:0,他引:1