全文获取类型
收费全文 | 9529篇 |
免费 | 572篇 |
国内免费 | 148篇 |
出版年
2023年 | 54篇 |
2022年 | 69篇 |
2021年 | 137篇 |
2020年 | 116篇 |
2019年 | 135篇 |
2018年 | 291篇 |
2017年 | 210篇 |
2016年 | 298篇 |
2015年 | 326篇 |
2014年 | 396篇 |
2013年 | 572篇 |
2012年 | 768篇 |
2011年 | 960篇 |
2010年 | 532篇 |
2009年 | 272篇 |
2008年 | 572篇 |
2007年 | 535篇 |
2006年 | 488篇 |
2005年 | 440篇 |
2004年 | 357篇 |
2003年 | 363篇 |
2002年 | 279篇 |
2001年 | 146篇 |
2000年 | 262篇 |
1999年 | 183篇 |
1998年 | 119篇 |
1997年 | 63篇 |
1996年 | 55篇 |
1995年 | 41篇 |
1994年 | 45篇 |
1993年 | 41篇 |
1992年 | 64篇 |
1991年 | 45篇 |
1990年 | 33篇 |
1989年 | 44篇 |
1988年 | 37篇 |
1987年 | 45篇 |
1986年 | 29篇 |
1985年 | 50篇 |
1984年 | 51篇 |
1983年 | 37篇 |
1982年 | 46篇 |
1981年 | 33篇 |
1980年 | 45篇 |
1979年 | 33篇 |
1978年 | 35篇 |
1977年 | 45篇 |
1976年 | 45篇 |
1975年 | 31篇 |
1974年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
991.
Mezyk-Kopeć R Bzowska M Bzowska M Mickowska B Mak P Potempa J Bereta J 《Biological chemistry》2005,386(8):801-811
Neutrophil elastase (NE) and cathepsin G (CG), the proteolytic enzymes localized in azurophil granules of neutrophils (PMN), are involved in PMN responses to various stimuli. When released at sites of inflammation, they participate in the degradation of numerous proteins involved in the regulation of the immune response. In this study, we employed ADAM17(-/-) fibroblasts stably transfected with cDNA of human pro-tumor necrosis factor alpha (proTNFalpha) (ADAM17(-/-)TNF(+)) to investigate the effects of NE and CG on shedding and degradation of TNFalpha. Both NE and CG were found to diminish the level of membrane TNFalpha (mTNFalpha) as measured by flow cytometry. This process was accompanied by the accumulation of biologically active soluble TNFalpha (sTNFalpha) in the culture medium, as determined by an increase in both the cytotoxic activity of TNFalpha and its ability to serve as a co-stimulator in the induction of inducible nitric oxide synthase (iNOS). However, in contrast to CG, NE at high concentrations was able to degrade sTNFalpha released from the cell surface. Using soluble recombinant human TNFalpha, we identified Val(93)-Ala(94) and Val(117)-Glu(118) as the NE cleavage sites within the sTNFalpha molecule. Taken together, the ability of NE and CG to modulate levels of membrane and soluble forms of TNFalpha may contribute to the proinflammatory activity of neutrophils. 相似文献
992.
Background
Liquid chromatography coupled to mass spectrometry (LC/MS) has been widely used in proteomics and metabolomics research. In this context, the technology has been increasingly used for differential profiling, i.e. broad screening of biomolecular components across multiple samples in order to elucidate the observed phenotypes and discover biomarkers. One of the major challenges in this domain remains development of better solutions for processing of LC/MS data. 相似文献993.
Background
Condition-dependence is a ubiquitous feature of animal life histories and has important implications for both natural and sexual selection. Mate choice, for instance, is typically based on condition-dependent signals. Theory predicts that one reason why condition-dependent signals may be special is that they allow females to scan for genes that confer high parasite resistance. Such explanations require a genetic link between immunocompetence and body condition, but existing evidence is limited to phenotypic associations. It remains unknown, therefore, whether females selecting males with good body condition simply obtain a healthy mate, or if they acquire genes for their offspring that confer high immunocompetence. 相似文献994.
995.
996.
Коммуникации занимается дегенерации производства штамма Streptomyces erythreus. Новые Jare представлены выводы:
- (1)Штамма включает в себя как sporogenous и asporogenous морфологических компонент, каждая из которых может быть делится на подтипы далее. По оценке производственной деятельности индивидуального морфологические подтипов было показано что sporogenous компонент культуры включает в себя лиц, в то время производственного asporogenous компонент включает в себя только непроизводственной или с низким уровнем производственного лиц. Микроскопического изучения показали, что sporogenous подтипов формируется прямо вегетативной hyphae, в то время как asporogenous подтипов формируется толще и сморщенное вегетативной hyphae. 相似文献
997.
Bayer M Mosandl A Thaçi D 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2005,819(2):323-328
Enantioselective analysis is used as a valuable tool for determining the biological origin of chiral derivatives of arachidonic, 11,14-eicosadienoic and linoleic acid in psoriatic skin scales and for clarifying their role in pathogenesis. This paper reports on a simple and rapid enantioselective determination (without any derivatization) of the fatty acid derivatives 13(R,S)-hydroxyoctadecadienoic acid [13(R,S)-HODE], 9(R,S)-hydroxyoctadecadienoic acid [9(R,S)-HODE] and 12(R,S)-hydroxyeicosatetraenoic acid [12(R,S)-HETE], using high-performance liquid chromatography (HPLC) with Chiralpak AD as the chiral selector and electrospray ionisation mass spectrometry (ESI-MS). The enantiomeric distribution of 12-HETE, 9-HODE and 13-HODE in psoriatic skin scales of untreated patients (untreated during the last 4 weeks before sampling) was evaluated in comparison to psoriatic skin scales of patients underlying systemic treatment. The enantiomeric distribution of 12-HETE and 9-HODE showed no remarkable differences, whilst samples of patients under systemic treatment exhibited a lower predominance of 13(S)-HODE than samples of untreated patients. Furthermore, the effect of UVB phototherapy on the enantiomeric distribution of 12-HETE, 9-HODE and 13-HODE was studied and a semiquantitation of these compounds in psoriatic skin scales performed. The detected amounts of 9-HODE in samples of untreated patients were remarkably lower than those in samples of patients underlying systemic treatment. In the case of UVB phototherapy, no influence on the enantiomeric distribution could be observed. 相似文献
998.
Trtić-Petrović T Liu JF Jönsson JA 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2005,826(1-2):169-176
The determination of drug-protein binding and free drug concentration in plasma applying the equilibrium sampling through membrane (ESTM) technique has been studied using supported liquid membrane extraction in a single hollow fibre without any membrane carrier. In the extraction setup, the donor phase (plasma or buffer) was placed in the vial, into which was immersed the hollow fibre with the acceptor phase situated in the lumen. This proposed technique was applied to study the drug-protein binding of five local anaesthetics and two antidepressants as model substances, and the influence of the total drug concentration on the drug-protein binding was investigated. The brief theoretical background for determination of the drug-protein binding under equilibrium conditions is described. The developed method shows a new, improved and simple procedure for determination of free drug concentration in plasma and extent of drug-protein binding. 相似文献
999.
Heinz Sager Dean Konjević Marijan Grubešić Zdravko Janicki Krešimir Severin Relja Beck 《European Journal of Wildlife Research》2005,51(1):63-64
Since 1996, European beavers (Castor fiber) have been reintroduced from Germany to Croatia. However, little is known about the health status of the established population. Necropsy of a 2-year-old female European beaver, which died from a car accident, revealed 28 adult trematodes in the preserved fragments of the colon and in the peritoneal cavity. All of them were identified as Stichorchis subtriquetrus. The typical location of these parasites is the large intestine, and the finding of several specimens in the peritoneal cavity can be explained by the severe trauma. We assume that the trematode was introduced to Croatia along with the beavers. Furthermore, it is very probable that the life cycle can be completed as the intermediate hosts are part of the local fauna. This is the first record of S. subtriquetrus in Croatia. 相似文献
1000.
Losses of proteolytic peptides during extraction and/or purification procedures succeeding in-gel or in-solution digests of proteins frequently occur in the course of protein identification investigations. In order to overcome this disadvantage, the method of in-capillary digest was developed: native proteins were incubated in the presence of endoproteases in the electrospray capillary and the resulting peptides were analyzed by nanoelectrospray-mass spectrometry during the ongoing proteolysis. In-capillary digest of apomyglobin by use of trypsin in a molar ratio of 25:1 yielded complete degradation already after 15 min. The sequence coverage based on formation of molecular ions was 100% and peptide ions could be fragmented by collision-induced dissociation and sequenced. When myoglobin was incubated in the electrospray capillary with trypsin in a molar ratio of 500:1, a clear shift from molecular ions and miscleaved peptide ions to the expected final tryptic peptide ions was observed over a 2 h period. The peptide spectra obtained from tryptic in-capillary proteolysis of bovine serum albumin and apotransferrin, respectively, gave rise to sequence coverages of more than 40% for both proteins. The data obtained from the peptide maps as well as from collision-induced dissociation (CID) of selected peptides were more than sufficient for protein identification by database searches. An elephant milk protein preparation was used to demonstrate the application of in-capillary proteolysis on protein mixtures. Tryptic digest, simultaneous analysis of the proteolytic peptides by use of CID, and subsequent sequencing allowed the identification of lactoferrin, alphas1-casein, beta-casein, delta-casein, and kappa-casein by homology search. 相似文献