全文获取类型
收费全文 | 4718篇 |
免费 | 240篇 |
国内免费 | 405篇 |
出版年
2023年 | 50篇 |
2022年 | 73篇 |
2021年 | 100篇 |
2020年 | 96篇 |
2019年 | 130篇 |
2018年 | 131篇 |
2017年 | 93篇 |
2016年 | 101篇 |
2015年 | 136篇 |
2014年 | 280篇 |
2013年 | 287篇 |
2012年 | 231篇 |
2011年 | 302篇 |
2010年 | 221篇 |
2009年 | 238篇 |
2008年 | 255篇 |
2007年 | 321篇 |
2006年 | 230篇 |
2005年 | 187篇 |
2004年 | 146篇 |
2003年 | 135篇 |
2002年 | 118篇 |
2001年 | 102篇 |
2000年 | 86篇 |
1999年 | 107篇 |
1998年 | 72篇 |
1997年 | 71篇 |
1996年 | 67篇 |
1995年 | 68篇 |
1994年 | 54篇 |
1993年 | 62篇 |
1992年 | 65篇 |
1991年 | 64篇 |
1990年 | 48篇 |
1989年 | 37篇 |
1988年 | 32篇 |
1987年 | 49篇 |
1986年 | 24篇 |
1985年 | 63篇 |
1984年 | 53篇 |
1983年 | 48篇 |
1982年 | 39篇 |
1981年 | 37篇 |
1980年 | 49篇 |
1979年 | 33篇 |
1978年 | 37篇 |
1977年 | 25篇 |
1976年 | 29篇 |
1975年 | 25篇 |
1973年 | 21篇 |
排序方式: 共有5363条查询结果,搜索用时 15 毫秒
1.
Benjamin C. Blum Weiwei Lin Matthew L. Lawton Qian Liu Julian Kwan Isabella Turcinovic Ryan Hekman Pingzhao Hu Andrew Emili 《Molecular & cellular proteomics : MCP》2022,21(1):100189
Metabolism is recognized as an important driver of cancer progression and other complex diseases, but global metabolite profiling remains a challenge. Protein expression profiling is often a poor proxy since existing pathway enrichment models provide an incomplete mapping between the proteome and metabolism. To overcome these gaps, we introduce multiomic metabolic enrichment network analysis (MOMENTA), an integrative multiomic data analysis framework for more accurately deducing metabolic pathway changes from proteomics data alone in a gene set analysis context by leveraging protein interaction networks to extend annotated metabolic models. We apply MOMENTA to proteomic data from diverse cancer cell lines and human tumors to demonstrate its utility at revealing variation in metabolic pathway activity across cancer types, which we verify using independent metabolomics measurements. The novel metabolic networks we uncover in breast cancer and other tumors are linked to clinical outcomes, underscoring the pathophysiological relevance of the findings. 相似文献
2.
Maria João Feio Trefor B. Reynoldson Verónica Ferreira Manuel Augusto S. Graça 《Hydrobiologia》2007,579(1):55-68
We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive
model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to
September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model.
At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream
hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207
taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution
to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise
forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality,
substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to
reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream
sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model,
the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model
methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and
increasing the number of ellipses that define quality bands.
Handling editor: K. Martens 相似文献
3.
1. Metabolism is the fundamental process that powers life. Understanding what drives metabolism is therefore critical to our understanding of the ecology and behaviour of organisms in nature. 2. Metabolic rate generally scales with body size according to a power law. However, considerable unexplained variation in metabolic rate remains after accounting for body mass with scaling functions. 3. We measured resting metabolic rates (oxygen consumption) of 227 field‐caught wolf spiders. Then, we tested for effects of body mass, species, and body condition on metabolic rate. 4. Metabolic rate scales with body mass to the 0.85 power in these wolf spiders, and there are metabolic rate differences between species. After accounting for these factors, residual variation in metabolic rate is related to spider body condition (abdomen:cephalothorax ratio). Spiders with better body condition consume more oxygen. 5. These results indicate that recent foraging history is an important determinant of metabolic rate, suggesting that although body mass and taxonomic identity are important, other factors can provide helpful insights into metabolic rate variation in ecological communities. 相似文献
4.
J.N. Beresford J.A. Gallagher M. Gowen M. Couch J. Poser D.D. Wood R.G.G. Russell 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,801(1):58-65
Cultural adherent human mononuclear cells produce factor(s) which stimulate the release of calcium from new-born mouse calvaria in organ culture. This stimulation of bone resorption is accompanied by an inhibition of the incorporation of [3H]proline into collagen which is independent of increased prostaglandin production by the bone. When human osteoblast-like cells are treated with conditioned medium from human mononuclear cells, collagen accounts for a decreased proportion of the protein synthesised. This effect on matrix synthesis is not accompanied by an inhibitory action of the monocyte-conditioned medium preparations on net cell proliferation. In human osteoblast-like cell cultures, partially purified human interleukin 1 also inhibits the production of the bone-specific protein osteocalcin in a dose-dependent fashion. These observations are consistent with the hypothesis that products of human monocytes similar to, or identical with, human interleukin 1 may be important regulators of bone metabolism and may contribute to the bone loss seen in diseases such as chronic rheumatoid arthritis. 相似文献
5.
Benjamin S. Johnson Lexie Chafin Daniela Farkas Jessica Adair Ajit Elhance Laszlo Farkas Joseph S. Bednash James D. Londino 《Molecular & cellular proteomics : MCP》2022,21(7):100256
Identifying protein–protein and other proximal interactions is central to dissecting signaling and regulatory processes in cells. BioID is a proximity-dependent biotinylation method that uses an “abortive” biotin ligase to detect proximal interactions in cells in a highly reproducible manner. Recent advancements in proximity-dependent biotinylation tools have improved efficiency and timing of labeling, allowing for measurement of interactions on a cellular timescale. However, issues of size, stability, and background labeling of these constructs persist. Here we modified the structure of BioID2, derived from Aquifex aeolicus BirA, to create a smaller, highly active, biotin ligase that we named MicroID2. Truncation of the C terrminus of BioID2 and addition of mutations to alleviate blockage of biotin/ATP binding at the active site of BioID2 resulted in a smaller and highly active construct with lower background labeling. Several additional point mutations improved the function of our modified MicroID2 construct compared with BioID2 and other biotin ligases, including TurboID and miniTurbo. MicroID2 is the smallest biotin ligase reported so far (180 amino acids [AAs] for MicroID2 versus 257 AAs for miniTurbo and 338 AAs for TurboID), yet it demonstrates only slightly less labeling activity than TurboID and outperforms miniTurbo. MicroID2 also had lower background labeling than TurboID. For experiments where precise temporal control of labeling is essential, we in addition developed a MicroID2 mutant, termed lbMicroID2 (low background MicroID2), that has lower labeling efficiency but significantly reduced biotin scavenging compared with BioID2. Finally, we demonstrate utility of MicroID2 in mass spectrometry experiments by localizing MicroID2 constructs to subcellular organelles and measuring proximal interactions. 相似文献
6.
7.
《Animal : an international journal of animal bioscience》2018,12(1):106-115
More energy-efficient, readily dimmable, long-lasting and more affordable light-emitting diode (LED) lights are increasingly finding applications in poultry production facilities. Despite anecdotal evidence about the benefits of such lighting on bird performance and behavior, concrete research data were lacking. In this study, a commercial poultry-specific LED light (dim-to-blue, controllable correlated color temperature (CCT) from 4500 to 5300 K) and a typical compact fluorescent light (CFL) (soft white, CCT=2700 K) were compared with regards to their effects on growing performance, activity levels, and feather and comb conditions of non-beak-trimmed W-36 pullets during a 14-week rearing period. A total of 1280-day-old pullets in two successive batches, 640 birds each, were used in the study. For each batch, pullets were randomly assigned to four identical litter-floor rooms equipped with perches, two rooms per light regimen, 160 birds per room. Body weight, BW uniformity (BWU), BW gain (BWG) and cumulative mortality rate (CMR) of the pullets were determined every 2 weeks from day-old to 14 weeks of age (WOA). Activity levels of the pullets at 5 to 14 WOA were delineated by movement index. Results revealed that pullets under the LED and CFL lights had comparable BW (1140±5 g v. 1135±5 g, P=0.41), BWU (90.8±1.0% v. 91.9±1.0%, P=0.48) and CMR (1.3±0.6% v. 2.7±0.6%, P=0.18) at 14 WOA despite some varying BWG during the rearing. Circadian activity levels of the pullets were higher under the LED light than under the CFL light, possibly resulting from differences in spectrum and/or perceived light intensity between the two lights. No feather damage or comb wound was apparent in either light regimen at the end of the rearing period. The results contribute to understanding the impact of emerging LED lights on pullets rearing which is a critical component of egg production. 相似文献
8.
H Slor 《Mutation research》1973,19(2):231-235
The carcinogen 7-bromomethylbenz(a)anthracene (BBA), which can bind strongly to DNA, induces unscheduled DNA synthesis (DNA repair) in normal lymphocytes but almost none in lymphocytes from patients with Xeroderma pigmentosum (XP), and inherited disease known to be defective in excision repair of ultraviolet-damaged DNA. We studied [3H]BBA's ability to bind to DNA of normal and XP lymphocytes, its influence on unscheduled DNA synthesis, and its removal from the DNA of both cell types. We found that 20–30% of the BBA is bound to macromolecules other than DNA and that its binding to DNA is essentially complete after 30 min. The induction of unscheduled DNA synthesis by the carcinogen in XP lymphocytes was approximately 10% of that induced in normal lymphocytes. While 15–20% of the BBA was removed from the DNA of normal cells 6 h after treatment, only 1–2% was removed from the DNA of XP cells. Thus, XP cells not only are defective in repairing ultraviolet-damaged DNA and excising thymine dimers but also fail to repair DNA damaged by certain carcinogens, and, most importantly, fail to remove the DNA-bound carcinogen, BBA. 相似文献
9.
Jarle Tryti Nordeide 《Journal of fish biology》2020,96(2):288-296
This paper highlights possible effects of physical and chemical mechanisms of formalin fixation and preservation on biological tissue and reviews the consequent potential inaccuracies on estimates of body mass of small fishes fixed and preserved in formalin. Twenty-six papers including 65 independent experiments with 35 species which examine effects of formalin on body mass estimates on small fishes are included. The effect of the formalin on the specimens depends on the salinity of the water used to dilute the commercial formalin (usually 1:9 formalin: water) before being used to fixate and preserve fish. Mean wet body mass of the specimens from the studies using seawater or fresh water diluted formalin deceases by 13% and increases by 7%, respectively, from before to after being immersed in formalin. The same trend is found with condition factor in the few papers that report this parameter. Body length decreases on average by c. 2% in fixated and preserved fish regardless of whether the formalin is diluted in seawater or fresh water. 相似文献
10.
In the past few decades, major advances in environmental protection within the coating application industry have been made. In spite of this technological progress, approximately 50% of industrial-solvent emissions still come from the paint-application sector. The advances made in reducing emissions for plants requiring licensing have unfortunately had no influence on the environmental efforts of smaller companies. Solvent-reduced painting systems, such as high-solid paints, water-based coating, and powder coating have not been able to achieve acceptance, nor have innovative application technologies. The principal arguments against a conversion to these ecologically more favorable alternatives were related to cost and quality.
Recently, the EU Solvent Directive (1999/13/EC) went into effect, aiming to significantly reduce industrial-solvent emissions. Up until this point, however, instruments enabling smaller companies to determine their solvent emissions and to simultaneously develop process-improvement potentials while keeping costs in mind have been missing.
Using the mass and energy flow-management approach, cost structures and environmental benefits can be made transparent to the entrepreneur. The primary result of the research projects presented here is the computer-based mass and energy flow model called the individual computer-aided mass and energy flow model for the vehicle-refinishing sector (IMPROVE). It can be used as a detailed business-consultancy tool. Based upon this, practical guidelines were developed for easy orientation and activity planning. They can be used by companies to help them fulfill the requirements of environmental legislation and to display the benefits that can be achieved by various emission-reduction measures. 相似文献
Recently, the EU Solvent Directive (1999/13/EC) went into effect, aiming to significantly reduce industrial-solvent emissions. Up until this point, however, instruments enabling smaller companies to determine their solvent emissions and to simultaneously develop process-improvement potentials while keeping costs in mind have been missing.
Using the mass and energy flow-management approach, cost structures and environmental benefits can be made transparent to the entrepreneur. The primary result of the research projects presented here is the computer-based mass and energy flow model called the individual computer-aided mass and energy flow model for the vehicle-refinishing sector (IMPROVE). It can be used as a detailed business-consultancy tool. Based upon this, practical guidelines were developed for easy orientation and activity planning. They can be used by companies to help them fulfill the requirements of environmental legislation and to display the benefits that can be achieved by various emission-reduction measures. 相似文献