全文获取类型
收费全文 | 1418篇 |
免费 | 96篇 |
国内免费 | 1篇 |
专业分类
1515篇 |
出版年
2022年 | 13篇 |
2021年 | 24篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 26篇 |
2017年 | 19篇 |
2016年 | 39篇 |
2015年 | 67篇 |
2014年 | 63篇 |
2013年 | 88篇 |
2012年 | 110篇 |
2011年 | 77篇 |
2010年 | 42篇 |
2009年 | 50篇 |
2008年 | 75篇 |
2007年 | 67篇 |
2006年 | 78篇 |
2005年 | 53篇 |
2004年 | 60篇 |
2003年 | 49篇 |
2002年 | 57篇 |
2001年 | 10篇 |
2000年 | 25篇 |
1999年 | 22篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 13篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 17篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 14篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1967年 | 6篇 |
排序方式: 共有1515条查询结果,搜索用时 9 毫秒
121.
Faidon Magkos Inge Tetens Susanne Gjedsted Bügel Claus Felby Simon Rnnow Schacht James O. Hill Eric Ravussin Arne Astrup 《Obesity (Silver Spring, Md.)》2020,28(1):73-79
Emissions of greenhouse gases (GHG) are linked to global warming and adverse climate changes. Meeting the needs of the increasing number of people on the planet presents a challenge for reducing total GHG burden. A further challenge may be the size of the average person on the planet and the increasing number of people with excess body weight. We used data on GHG emissions from various sources and estimated that obesity is associated with ~20% greater GHG emissions compared with the normal‐weight state. On a global scale, obesity contributes to an extra GHG emissions of ~49 megatons per year of CO2 equivalent (CO2eq) from oxidative metabolism due to greater metabolic demands, ~361 megatons per year of CO2eq from food production processes due to increased food intake, and ~290 megatons per year of CO2eq from automobile and air transportation due to greater body weight. Therefore, the total impact of obesity may be extra emissions of ~700 megatons per year of CO2eq, which is about 1.6% of worldwide GHG emissions. Inasmuch as obesity is an important contributor to global GHG burden, strategies to reduce its prevalence should prioritize efforts to reduce GHG emissions. Accordingly, reducing obesity may have considerable benefits for both public health and the environment. 相似文献
122.
Nagelkerken L Haspels I van Rijs W Blauw B Ferrant JL Hess DM Garber EA Taylor FR Burkly LC 《Journal of immunology (Baltimore, Md. : 1950)》2004,173(2):993-999
It has been demonstrated that anti-CD154 mAb treatment effectively inhibits the development of experimental autoimmune encephalomyelitis (EAE). However, although it appears to prevent the induction of Th1 cells and reactivation of encephalitogenic T cells within the CNS, little information is available regarding the involvement of alternative mechanisms, nor has the contribution of Fc effector mechanisms in this context been addressed. By contrast, efficacy of anti-CD154 mAbs in models of allotransplantation has been reported to involve long-term unresponsiveness, potentially via activation of T regulatory cells, and recently was reported to depend on Fc-dependent functions, such as activated T cell depletion through FcgammaR or complement. In this study we demonstrate that anti-CD154 mAb treatment inhibits EAE development in SJL mice without apparent long-term unresponsiveness or active suppression of disease. To address whether the mechanism of inhibition of EAE by anti-CD154 mAb depends on its Fc effector interactions, we compared an anti-CD154 mAb with its aglycosyl counterpart with severely impaired FcgammaR binding and reduced complement binding activity with regard to their ability to inhibit clinical signs of EAE and report that both forms of the Ab are similarly protective. This observation was largely confirmed by the extent of leukocyte infiltration of the CNS; however, mice treated with the aglycosyl form may display slightly more proteolipid protein 139-151-specific immune reactivity. It is concluded that FcR interactions do not play a major role in the protective effect of anti-CD154 mAb in the context of EAE, though they may contribute to the full abrogation of peripheral peptide-specific lymphocyte responses. 相似文献
123.
124.
We tested the influence of illuminance and level of forager experience on nest orientation behavior of the social wasps Vespula vulgaris, Vespa crabro, and Dolichovespula saxonica in an artificial laboratory tunnel system. The number of wasps which oriented themselves chemically via a terrestrial trail or used visual orientation were determined at different illuminance levels for foragers which were naïve or experienced with the tunnel system. In V. vulgaris and D. saxonica, mainly the young and naïve foragers used the chemical trail for orientation in brightness. Experienced foragers used visual cues for nest orientation. In V. crabro, naïve and experienced foragers followed the chemical trail in a similar intensity. In darkness, when visual orientation was limited, the relative importance of the chemical trail increased dramatically in all species and all experience classes. 相似文献
125.
126.
This study was designed to determine whether significant differences in saturation levels existed among patients with aspiration and patients without and wether pulse oximetry can reliably detect aspiration in patients with dysphagia. We also examined the effects of gender and disease (neurologic versus non neurologic) on saturation levels. We studied 38 patients. They all underwent a videofluoroscopic study of swallowing (VFSS). Twenty patients aspirated on videofluoroscopic study of swallowing: ten patients were solid aspirators, ten patients were liquid aspirators. In each group (liquid aspirators, solid aspirators or non aspirators) we found no significant difference in saturation levels. We found however a significant difference in saturation levels between each group before, during and after videofluoroscopic study of swallowing. Both gender and disease had an effect on saturation levels. We conclude that pulse oximetry can not serve as a screening tool for detection of aspiration as saturation levels are dependent on many factors. Therefore one can not reliably predict aspiration with a single saturation screening. 相似文献
127.
Methods for extracting useful information from the datasets produced by microarray experiments are at present of much interest. Here we present new methods for finding gene sets that are well suited for distinguishing experiment classes, such as healthy versus diseased tissues. Our methods are based on evaluating genes in pairs and evaluating how well a pair in combination distinguishes two experiment classes. We tested the ability of our pair-based methods to select gene sets that generalize the differences between experiment classes and compared the performance relative to two standard methods. To assess the ability to generalize class differences, we studied how well the gene sets we select are suited for learning a classifier. We show that the gene sets selected by our methods outperform the standard methods, in some cases by a large margin, in terms of cross-validation prediction accuracy of the learned classifier. We show that on two public datasets, accurate diagnoses can be made using only 15-30 genes. Our results have implications for how to select marker genes and how many gene measurements are needed for diagnostic purposes. When looking for differential expression between experiment classes, it may not be sufficient to look at each gene in a separate universe. Evaluating combinations of genes reveals interesting information that will not be discovered otherwise. Our results show that class prediction can be improved by taking advantage of this extra information. 相似文献
128.
The longitudinal muscle of isolated rat ileum is a sensitive bioassay suitable for testing compounds with antagonistic effects on the B(1) receptor. Bradykinin analogues with replacement of proline by alkyl-substituted phenylalanine at position 7 are effective on this receptor as entire molecules and have a stronger antagonistic effect than on the B(2) receptor. A corresponding desArg(9)-compound has a specific effect on the B(1) receptor and a very high antagonistic potency. [LNMPhe(2)]bradykinin as a compound without any replacement at position 7 or 8 shows antagonistic activity as well. 相似文献
129.
Laurberg P Andersen S Pedersen IB Ovesen L Knudsen N 《BioFactors (Oxford, England)》2003,19(3-4):145-153
Thyroid diseases are common in all populations but the type and frequency depends on environmental factors. In Denmark geographical differences in iodine intake are caused by different iodine contents of drinking water, which varies from < 1 to 139 microg iodine per litre. Comparative epidemiologic studies have demonstrated considerable differences in type and occurrence of thyroid disease with more goitre and hyperthyroidism in Aalborg with water iodine content around 5 microg/L, and more hypothyroidism in Copenhagen with water iodine around 20 microg/L. In Denmark, iodine in ground water is bound in humic substances, which have probably leached from marine sediments in the aquifers. Interestingly, humic substances in water from other parts of the world have goitrogenic properties, especially humic substances from coal and shale. Humic substances are heterogeneous mixtures of naturally occurring molecules, produced by decomposition of plant and animal tissues. The effect of humic substances in drinking water on the epidemiology of thyroid disease probably depends on the source of aquifer sediments. 相似文献
130.
In order to investigate factors influencing the production of the bacteriocin, sakacin P, Lactobacillus sakei CCUG 42687 was grown in a completely defined medium (DML-B) with 33 components. Although the maximum sakacin P concentration obtained was higher on a complex medium due to higher cell mass, the production per cell mass was higher in DML-B. Sakacin P was produced at 4-30 degrees C, with the highest specific production at low temperatures. More sakacin P was produced at uncontrolled pH compared with cultivation at pH 6.3. Tween-80 had a positive effect on sakacin P production, while addition of sodium chloride and trace metals had negative effects. The decrease in sakacin P concentration during the late growth and stationary phases was shown to be cell-independent and promoted at high temperature and pH. Some differences in production levels of sakacin P were found among six strains of Lactobacillus sakei tested. 相似文献