全文获取类型
收费全文 | 1785篇 |
免费 | 32篇 |
国内免费 | 9篇 |
专业分类
化学 | 1312篇 |
晶体学 | 31篇 |
力学 | 40篇 |
数学 | 225篇 |
物理学 | 218篇 |
出版年
2022年 | 9篇 |
2021年 | 16篇 |
2020年 | 23篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 18篇 |
2016年 | 35篇 |
2015年 | 23篇 |
2014年 | 45篇 |
2013年 | 93篇 |
2012年 | 98篇 |
2011年 | 129篇 |
2010年 | 53篇 |
2009年 | 60篇 |
2008年 | 121篇 |
2007年 | 121篇 |
2006年 | 139篇 |
2005年 | 107篇 |
2004年 | 86篇 |
2003年 | 80篇 |
2002年 | 82篇 |
2001年 | 35篇 |
2000年 | 16篇 |
1999年 | 23篇 |
1998年 | 21篇 |
1997年 | 27篇 |
1996年 | 21篇 |
1995年 | 32篇 |
1994年 | 36篇 |
1993年 | 12篇 |
1992年 | 18篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 19篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 9篇 |
1973年 | 5篇 |
排序方式: 共有1826条查询结果,搜索用时 0 毫秒
61.
Timothy M. Miller Thomas X. Neenan Elizabeth W. Kwock Susan M. Stein 《Macromolecular Symposia》1994,77(1):35-42
The first general single-step route to dendritic or cascade polyaryl ethers analogous to common linear polyaryl ethers is described. The sodium salts of four AB2 monomers each containing a single phenolic hydroxyl group and two aryl fluorides activated toward nucleophilic substitution by carbonyl, sulphonyl, or tetrafluorophenyl moieties are shown to polymerize in hot N, N-dimethylacetamide. The products are high molecular weight polymers (7000 < Mn < 36000), have narrow polydispersities (1.50 < Mw/Mn < 4.50), and are highly soluble in organic solvents. The molecular weights of two of the polymers increase with monomer concentration. The polymers are thermally stable (500 °C under N2) and have glass transition temperatures ranging from 135 to 231 °C. 相似文献
62.
Yukiko Yasuoka Yuichiro Izumi Takashi Fukuyama Haruki Omiya Truyen D. Pham Hideki Inoue Tomomi Oshima Taiga Yamazaki Takayuki Uematsu Noritada Kobayashi Yoshitaka Shimada Yasushi Nagaba Tetsuro Yamashita Masashi Mukoyama Yuichi Sato Susan M. Wall Jeff M. Sands Noriko Takahashi Katsumasa Kawahara Hiroshi Nonoguchi 《Molecules (Basel, Switzerland)》2022,27(3)
Anemia is a major complication of chronic renal failure. To treat this anemia, prolylhydroxylase domain enzyme (PHD) inhibitors as well as erythropoiesis-stimulating agents (ESAs) have been used. Although PHD inhibitors rapidly stimulate erythropoietin (Epo) production, the precise sites of Epo production following the administration of these drugs have not been identified. We developed a novel method for the detection of the Epo protein that employs deglycosylation-coupled Western blotting. With protein deglycosylation, tissue Epo contents can be quantified over an extremely wide range. Using this method, we examined the effects of the PHD inhibitor, Roxadustat (ROX), and severe hypoxia on Epo production in various tissues in rats. We observed that ROX increased Epo mRNA expression in both the kidneys and liver. However, Epo protein was detected in the kidneys but not in the liver. Epo protein was also detected in the salivary glands, spleen, epididymis and ovaries. However, both PHD inhibitors (ROX) and severe hypoxia increased the Epo protein abundance only in the kidneys. These data show that, while Epo is produced in many tissues, PHD inhibitors as well as severe hypoxia regulate Epo production only in the kidneys. 相似文献
63.
Michelle Cutajar Robert A. Stockman Susan Braovac Calin Constantin Steindal Angeliki Zisi Stephen E. Harding 《Molecules (Basel, Switzerland)》2022,27(7)
Butvar B-98 and PDMS-OH both have a demonstrable ability as consolidants for archaeological wood. This makes them both potential treatment options for the Oseberg collection, which is one of the most important archaeological finds from the Viking era. Both Butvar B-98 and PDMS-OH are soluble in organic solvents, offering a useful alternative to aqueous-based consolidants. Extensive characterisation studies were carried out on both of these polymers, with the use of analytical ultracentrifugation and viscometry, for the benefit of conservators wanting to know more about the physical properties of these materials. Short column sedimentation equilibrium analysis using SEDFIT-MSTAR revealed a weight-average molar mass (weight-average molecular weight) Mw of (54.0 ± 1.5) kDa (kg · mol−1) for Butvar B-98, while four samples of PDMS-OH siloxanes (each with a different molar mass) had an Mw of (52.5 ± 3.0) kDa, (38.8 ± 1.5) kDa, (6.2 ± 0.7) kDa and (1.6 ± 0.1) kDa. Sedimentation velocity confirmed that all polymers were heterogeneous, with a wide range of molar masses. All molecular species showed considerable conformational asymmetry from measurements of intrinsic viscosity, which would facilitate networking interactions as consolidants. It is anticipated that the accumulated data on these two consolidants will enable conservators to make a more informed decision when it comes to choosing which treatment to administer to archaeological artefacts. 相似文献
64.
John de Jersey ZHENG Yuan-zhi FAN Hong-kuan Gary Schenk Luke Guddat Susan Hamilton 《高等学校化学研究》2006,22(2):263-264
Introduction Purpleacidphosphatases(PAPs)compriseofa familyofbinuclearmetal containinghydrolases,some membersofwhichhavebeenisolatedandcharacterized fromanimal,plantandfungalsources[1].PAPsnoton lycatalyzethehydrolysesofawiderangeofphosphate estersandanhy… 相似文献
65.
Selective growth of metal and binary metal tips on CdS nanorods 总被引:1,自引:0,他引:1
66.
Background
Growth cone migratory patterns show evidence of both deterministic and stochastic search modes. 相似文献67.
Let X
t be a one-dimensional diffusion of the form dX
t=dB
t+(X
t)dt. Let Tbe a fixed positive number and let
be the diffusion process which is X
t conditioned so that X
0=X
T=x. If the drift is constant, i.e.,
, then the conditioned diffusion process
is a Brownian bridge. In this paper, we show the converse is false. There is a two parameter family of nonlinear drifts with this property. 相似文献
68.
Livia S Machado Anna Kozak Adviye Ergul David C Hess Cesario V Borlongan Susan C Fagan 《BMC neuroscience》2006,7(1):56
Background
Matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) are increased in the brain after experimental ischemic stroke in rats. These two proteases are involved with the degradation of the basal lamina and loss of stability of the blood brain barrier that occurs after ischemia and that is associated with thrombolytic therapy in ischemic stroke. Minocycline is a lipophilic tetracycline and is neuroprotective in several models of brain injury. Minocycline inhibits inflammation, apoptosis and extracellular matrix degradation. In this study we investigated whether delayed minocycline inhibits brain MMPs activated by ischemia in a model of temporary occlusion in Wistar rats. 相似文献69.
Vasilyeva Inga Abdusalyamova Maxsuda Makhmudov Farchod Eshov Bakhtier Kauzlarich Susan 《Journal of Thermal Analysis and Calorimetry》2019,136(2):541-548
Journal of Thermal Analysis and Calorimetry - A high sublimation rate of Yb14MnSb11 as a promising thermoelectric material at working temperatures is a critical factor for its space power... 相似文献
70.
Brandon C. Presley Marisol S. Castaneto Barry K. Logan Susan A. Jansen-Varnum 《Biomedical chromatography : BMC》2020,34(9):e4884
FUB-AMB, an indazole carboxamide synthetic cannabinoid recreational drug, was one of the compounds most frequently reported to governmental agencies worldwide between 2016 and 2019. It has been implicated in intoxications and fatalities, posing a risk to public health. In the current study, FUB-AMB was incubated with human liver microsomes (HLM) to assess its metabolic fate and stability and to determine if its major ester hydrolysis metabolite (M1) was present in 12 authentic forensic human blood samples from driving under the influence of drug cases and postmortem investigations using UHPLC–MS/MS. FUB-AMB was rapidly metabolized in HLM, generating M1 that was stable through a 120-min incubation period, a finding that indicates a potential long detection window in human biological samples. M1 was identified in all blood samples, and no parent drug was detected. The authors propose that M1 is a reliable marker for inclusion in laboratory blood screens for FUB-AMB; this metabolite may be pharmacologically active like its precursor FUB-AMB. M1 frequently appears in samples in which the parent drug is undetectable and can point to the causative agent. The results suggest that it is imperative that synthetic cannabinoid laboratory assay panels include metabolites, especially known or potential pharmacologically active metabolites, particularly for compounds with short half-lives. 相似文献