全文获取类型
收费全文 | 3000篇 |
免费 | 197篇 |
出版年
2020年 | 19篇 |
2019年 | 18篇 |
2018年 | 32篇 |
2017年 | 29篇 |
2016年 | 45篇 |
2015年 | 83篇 |
2014年 | 109篇 |
2013年 | 154篇 |
2012年 | 149篇 |
2011年 | 158篇 |
2010年 | 93篇 |
2009年 | 81篇 |
2008年 | 140篇 |
2007年 | 186篇 |
2006年 | 173篇 |
2005年 | 156篇 |
2004年 | 154篇 |
2003年 | 138篇 |
2002年 | 131篇 |
2001年 | 28篇 |
2000年 | 20篇 |
1999年 | 35篇 |
1998年 | 33篇 |
1997年 | 34篇 |
1996年 | 31篇 |
1995年 | 37篇 |
1994年 | 27篇 |
1993年 | 41篇 |
1992年 | 19篇 |
1991年 | 22篇 |
1990年 | 27篇 |
1989年 | 29篇 |
1988年 | 36篇 |
1987年 | 30篇 |
1985年 | 31篇 |
1984年 | 26篇 |
1983年 | 39篇 |
1982年 | 37篇 |
1981年 | 36篇 |
1980年 | 38篇 |
1979年 | 27篇 |
1978年 | 33篇 |
1977年 | 27篇 |
1976年 | 21篇 |
1975年 | 24篇 |
1973年 | 24篇 |
1971年 | 17篇 |
1970年 | 18篇 |
1967年 | 18篇 |
1960年 | 17篇 |
排序方式: 共有3197条查询结果,搜索用时 15 毫秒
121.
Bernd Gröttrup Jens Wiltfang Helmut Heinsen Katrin Marcus Helmut E. Meyer Lea T. Grinberg Young Mok Park 《Proteomics》2013,13(20):2938-2941
The HUPO Brain Proteome Project (HUPO BPP) held its 19th workshop in Dortmund, Germany, from May 22 to 24, 2013. The focus of the spring workshop was on strategies and developments concerning early diagnosis of neurodegenerative diseases 相似文献
122.
Alexander Benedikt Leichtle Uta Ceglarek Peter Weinert Christos T. Nakas Jean-Marc Nuoffer Julia Kase Tim Conrad Helmut Witzigmann Joachim Thiery Georg Martin Fiedler 《Metabolomics : Official journal of the Metabolomic Society》2013,9(3):677-687
Metabolomics as one of the most rapidly growing technologies in the “-omics” field denotes the comprehensive analysis of low molecular-weight compounds and their pathways. Cancer-specific alterations of the metabolome can be detected by high-throughput mass-spectrometric metabolite profiling and serve as a considerable source of new markers for the early differentiation of malignant diseases as well as their distinction from benign states. However, a comprehensive framework for the statistical evaluation of marker panels in a multi-class setting has not yet been established. We collected serum samples of 40 pancreatic carcinoma patients, 40 controls, and 23 pancreatitis patients according to standard protocols and generated amino acid profiles by routine mass-spectrometry. In an intrinsic three-class bioinformatic approach we compared these profiles, evaluated their selectivity and computed multi-marker panels combined with the conventional tumor marker CA 19-9. Additionally, we tested for non-inferiority and superiority to determine the diagnostic surplus value of our multi-metabolite marker panels. Compared to CA 19-9 alone, the combined amino acid-based metabolite panel had a superior selectivity for the discrimination of healthy controls, pancreatitis, and pancreatic carcinoma patients $ [ {\text{volume under ROC surface}}\;\left( {\text{VUS}} \right) = 0. 8 9 1 { }\left( { 9 5\,\% {\text{ CI }}0. 7 9 4- 0. 9 6 8} \right)]. $ We combined highly standardized samples, a three-class study design, a high-throughput mass-spectrometric technique, and a comprehensive bioinformatic framework to identify metabolite panels selective for all three groups in a single approach. Our results suggest that metabolomic profiling necessitates appropriate evaluation strategies and—despite all its current limitations—can deliver marker panels with high selectivity even in multi-class settings. 相似文献
123.
124.
Carmen Zinssmeister Helmut Keupp Gilbert Tischendorf Freya Kaulbars Marc Gottschling 《PloS one》2013,8(1)
Biomineralization in calcareous dinophytes (Thoracosphaeracaea, Peridiniales) takes place in coccoid cells and is presently poorly understood. Vacuolar crystal-like particles as well as collection sites within the prospective calcareous shell may play a crucial role during this process at the ultrastructural level. Using transmission electron microscopy, we investigated the ultrastructure of coccoid cells at an early developmental stage in fourteen calcareous dinophyte strains (corresponding to at least ten species of Calciodinellum, Calcigonellum, Leonella, Pernambugia, Scrippsiella, and Thoracosphaera). The shell of the coccoid cells consisted either of one (Leonella, Thoracosphaera) or two matrices (Scrippsiella and its relatives) of unknown element composition, whereas calcite is deposited in the only or the outer layer, respectively. We observed crystal-like particles in cytoplasmic vacuoles in cells of nine of the strains investigated and assume that they are widespread among calcareous dinophytes. However, similar structures are also found outside the Thoracosphaeraceae, and we postulate an evolutionarily old physiological pathway (possibly involved in detoxification) that later was specialized for calcification. We aim to contribute to a deeper knowledge of the biomineralization process in calcareous dinophytes. 相似文献
125.
Schllnberger Helmut Kaiser Jan Christian Eidemller Markus Zablotska Lydia B. 《Radiation and environmental biophysics》2020,59(1):63-78
Radiation and Environmental Biophysics - Recent analyses of the Canadian fluoroscopy cohort study reported significantly increased radiation risks of mortality from ischemic heart diseases (IHD)... 相似文献
126.
127.
Dipl.-Landw. Hans-Joachim Spohn Prof. Dr. Helmut Bochow 《Archives Of Phytopathology And Plant Protection》2013,46(3):223-233
Sunflower is one of the most important oilseed crops, which is grown in many countries. Increasing demand to use sunflower oil has expanded the under cultivation area throughout the world. Sunflower viruses have been reported as one of the pathogens that reduce the quantity and the quality of this product in a number of countries. In our research to study the occurrence and distribution of viruses in sunflower fields of Iran, 562 samples were collected from different fields in Kerman and Isfahan provinces during growing seasons from 2009 to 2011. Potato virus Y (PVY), Cucumber mosaic virus (CMV) and Tomato spotted wilt virus (TSWV) were detected by double antibody sandwich enzyme-linked immunosorbent assay. Also, numbers of samples were positive for infection to potyviruses (except PVY) in antigen-coated-plate enzyme-linked immunosorbent assay test using potyviruses general antiserum. Infected plants had symptoms like mosaic, yellowing, deformation, necrotic and chlorotic lesions and mottling on leaves and stunting. The infection rates of potyviruses, PVY, CMV and TSWV in Isfahan province were 33, 22, 4.18 and 3.25% of collected samples, respectively. The corresponding rates for samples from Kerman province were 15, 5, 0.8 and 0.4% of collected samples. According to these results, viral infection in Isfahan province was more than surveyed in Kerman province during the mentioned period of three years. Furthermore, generally there was a decrease in the percentage of viral infection during this three growing seasons in both provinces. This is the first report of the detection of CMV and TSWV in sunflower fields of Isfahan and Kerman and first report of PVY in Isfahan. 相似文献
128.
129.
Hideko Kawaki Albin Otter Helmut Beierbeck George Kotovych John M. Stewart 《Journal of biomolecular structure & dynamics》2013,31(4):795-803
Abstract High-field nuclear magnetic resonance measurements were carried out on substance P fragments SP4–11 [pGlu5]-SP5–11 and [pGlu6]SP6–11 both at 400 and at 500 MHz. A spectral simulation was carried out on two of these peptides and the coupling constants were interpreted in terms of the conformations. The JNH-CHa coupling constants are all ~8 Hz, with the exception of glycine, indicating no preferred conformation for the backbone. For the amino acids other than p-Glu, a comparison of the coupling constant data suggests the same relative rotamer populations for the side chains. Proton longitudinal relaxation time data were measured for all three peptides and support the above conclusions. 相似文献
130.
Modeling simple and complex biopolymers in solution requires the shapes of these molecules to be approximated by bead modeling procedures, primarily for the prediction of hydrodynamic and scattering quantities. Though several bead modeling strategies (strict, shell and filling models) and a variety of computer programs (preferably the HYDRO suite by the García de la Torre group) are available, several subtle questions remain to be answered, in particular concerning the appropriate volume correction for intrinsic viscosity computations. In this context, various versions of the HYDRO programs and different types of volume corrections, as well as the novel, alternative program ZENO of the Mansfield group, were applied to a plethora of thoroughly designed multibead models of spherical, ellipsoidal, cylindrical and prismatic shapes. A critical comparison of the results obtained reveals a variety of new aspects, useful for many future applications. Among these, application of our recently suggested “reduced volume correction” (RVC) together with specially adapted HYDRO versions and use of ZENO turned out to be highly effective, in particular when aiming at filling model strategies and using high bead numbers, a domain not fully supported by the recent HYDRO++ versions. By our approaches, the values of translational properties (diffusion coefficients, D, and intrinsic viscosities, [η]) of all multibead models applied were anticipated correctly. 相似文献