全文获取类型
收费全文 | 4763篇 |
免费 | 372篇 |
国内免费 | 1篇 |
出版年
2023年 | 25篇 |
2022年 | 64篇 |
2021年 | 119篇 |
2020年 | 51篇 |
2019年 | 73篇 |
2018年 | 96篇 |
2017年 | 85篇 |
2016年 | 147篇 |
2015年 | 260篇 |
2014年 | 243篇 |
2013年 | 329篇 |
2012年 | 417篇 |
2011年 | 395篇 |
2010年 | 248篇 |
2009年 | 194篇 |
2008年 | 306篇 |
2007年 | 299篇 |
2006年 | 263篇 |
2005年 | 258篇 |
2004年 | 243篇 |
2003年 | 219篇 |
2002年 | 237篇 |
2001年 | 44篇 |
2000年 | 35篇 |
1999年 | 47篇 |
1998年 | 52篇 |
1997年 | 45篇 |
1996年 | 19篇 |
1995年 | 35篇 |
1994年 | 31篇 |
1993年 | 34篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1976年 | 10篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1969年 | 5篇 |
排序方式: 共有5136条查询结果,搜索用时 15 毫秒
1.
Monica Driscoll 《Developmental neurobiology》1992,23(9):1327-1351
In C. elegans, cell death can be readily studied at the cellular, genetic, and molecular levels. Two types of death have been characterized in this nematode: (1) programmed cell death, which occurs as a normal component in development; and (2) pathological cell death which occurs aberrantly as a consequence of mutation. Analysis of mutations that disrupt programmed cell death in various ways has defined a genetic pathway for programmed cell death which includes genes that perform such functions as the determination of which cells die, the execution of cell death, the engulfment of cell corpses, and the digestion of DNA from dead cells. Molecular analysis is providing insightinto the nature of the molecules that function in these aspects of programmed cell death. Characterization of some genes that mutate to induce abnormal cell death has defined a novel gene family called degenerins that encode putative membrane proteins. Dominant alleles of at least two degenerin genes, mec-4 and deg-1, can cause cellular swelling and late onset neurodegeneration of specific groups of cells. © 1992 John Wiley & Sons, Inc. 相似文献
2.
Filippo Genovese Stefania Ferrari Giambattista Guaitoli Monica Caselli M. Paola Costi Glauco Ponterini 《Protein science : a publication of the Protein Society》2010,19(5):1023-1030
An ad hoc bioconjugation/fluorescence resonance energy transfer (FRET) assay has been designed to spectroscopically monitor the quaternary state of human thymidylate synthase dimeric protein. The approach enables the chemoselective engineering of allosteric residues while preserving the native protein functions through reversible masking of residues within the catalytic site, and is therefore suitable for activity/oligomerization dual assay screenings. It is applied to tag the two subunits of human thymidylate synthase at cysteines 43 and 43′ with an excitation energy donor/acceptor pair. The dimer–monomer equilibrium of the enzyme is then characterized through steady‐state fluorescence determination of the intersubunit resonance energy transfer efficiency. 相似文献
3.
Monica BreurkenEdith H.M. Lempens Rinske P. TemmingBrett A. Helms E.W. MeijerMaarten Merkx 《Bioorganic & medicinal chemistry》2011,19(3):1062-1071
Collagen is an attractive marker for tissue remodeling in a variety of common disease processes. Here we report the preparation of protein dendrimers as multivalent collagen targeting ligands by native chemical ligation of the collagen binding protein CNA35 to cysteine-functionalized dendritic divalent (AB2) and tetravalent (AB4) wedges. The binding of these multivalent protein constructs was studied on collagen-immobilized chip surfaces as well as to native collagen in rat intestinal tissues. To understand the importance of target density we also created collagen-mimicking surfaces by immobilizing synthetic collagen triple helical peptides at various densities on a chip surface. Multivalent display of a weak-binding variant (CNA35-Y175K) resulted in a large increase in collagen affinity, effectively restoring the collagen imaging capacities for the AB4 system. In addition, dissociation of these multivalent CNA35 dendrimers from collagen surfaces was found to be strongly attenuated. 相似文献
4.
Javier J Gonzalez-Rosa Manuel Vazquez-Marrufo Encarnacion Vaquero Pablo Duque Monica Borges Carlos M Gomez-Gonzalez Guillermo Izquierdo 《BMC neurology》2011,11(1):64-19
Background
Event-related potentials (ERPs) may be used as a highly sensitive way of detecting subtle degrees of cognitive dysfunction. On the other hand, impairment of cognitive skills is increasingly recognised as a hallmark of patients suffering from multiple sclerosis (MS). We sought to determine the psychophysiological pattern of information processing among MS patients with the relapsing-remitting form of the disease and low physical disability considered as two subtypes: 'typical relapsing-remitting' (RRMS) and 'benign MS' (BMS). Furthermore, we subjected our data to a cluster analysis to determine whether MS patients and healthy controls could be differentiated in terms of their psychophysiological profile. 相似文献5.
6.
Agricultural biotechnologies embrace a large array of conventional and modern technologies, spanning from composting organic by-products of agriculture to innovative improvement of quality traits of about twenty out of the mostly cultivated plants. In EU a rather restrictive legislative framework has been installed for GMOs, requiring a risk assessment disproportionate with respect to conventional agriculture and organic farming products. The latter are far from being proved safe for human and animal health, and for the environment.Biotechnology of GMOs has been overtaken by biopolitics. On one side there are biotechnological challenges to be tackled, on another side there is plenty of ground for biopolitical decisions about GMOs. Perhaps the era of harsh confrontation could be fruitfully replaced by sensible cooperation, in order to get a sustainable agricultural development. 相似文献
7.
Species-specific algal responses to zooplankton: experimental and field observations in three nutrient-limited lakes 总被引:3,自引:0,他引:3
Elser James J.; Goff Nancy C.; MacKay Neil A.; Amand Ann L.St.; Elser Monica M.; Carpenter Stephen R. 《Journal of plankton research》1987,9(4):699-717
A series of 4-day manipulations of zooplankton biomass and nutrientavailability was performed in enclosures in three lakes to determinespecies-specific algal responses to herbivory and nutrient enrichment.Algal performance in enclosures was compared to the relationshipsbetween weekly algal growth rates and the zooplankton in situ.When in situ growth rates were significant functions of zooplanktonbiomass, the responses were generally consistent with responsesin the enclosure experiments. The importance of both nutrientsand zooplankton in mediating algal growth was demonstrated bynumerous observations: strong algal community response to enrichment,unimodal or positive responses of certain algal taxa to zooplanktonbiomass, differences in degree of nutrient limitation amongthe algal response types, lack of nutrient limitation of non-grazedalgal taxa and a preponderance of taxa with no net responseto increasing zooplankton biomass. Variation in the zooplanktoncommunity may be the largest source of variability in nutrientsupply rate during summer in stratified lakes, and causes substationalvariability in the algae. Algae responded more strongly to changesin zooplankton composition than to changes in zooplankton biomass.We conclude that, due to the close coupling of phytoplanktonand zooplankton communities in these nutrient-limited lakes,major compositional changes in the zooplankton have greatereffects on the algae than do changes in biomass of grazers alreadypresent.
1Present address: Division of Environmental Studies, Universityof California, Davis, CA 95616, USA
2Present address: Division of Biological Sciences, Universityof California, Davis, CA 95616, USA 相似文献
8.
A mouse model for poliovirus neurovirulence identifies mutations that attenuate the virus for humans. 总被引:20,自引:16,他引:4 下载免费PDF全文
A mutation in the genome of poliovirus type 3 that is known to reduce neurovirulence in humans similarly reduces neurovirulence in mice when incorporated into a mouse-adapted-human poliovirus recombinant. Viral recombinants with a uracil at nucleotide position 472 in the 5'-noncoding regions of their genomes are unable to replicate in the mouse brain. Viral recombinants with a cytosine at this position are neurovirulent in mice. Neurovirulence of poliovirus in mice may therefore prove to be a useful indicator of the genetic stability of new attenuating mutations created by site-directed mutagenesis. 相似文献
9.
Richard L. Wahl Barry S. Wilson Monica Liebert William H. Beierwaltes 《Cancer immunology, immunotherapy : CII》1987,24(3):221-224
Summary Nonspecific uptake of radiolabeled monoclonal antibodies in normal tissues is a significant problem for tumor imaging. A potential means of decreasing nonspecific antibody binding is to blockade nonspecific antibody binding sites by predosing with cold, nonspecific isotypematched antibody, before injecting specific antibody. Nontumor-specific murine monoclonal antibody LK2H10 (IgG1) or Ab-1 (IgG2a) was given i.v. at doses of 0 to 3.5 mg to nude mice with xenografts of human melanoma. These mice were then given i.v. 4 g of 131I anti-high molecular weight antigen of melanoma (HMWMAA) monoclonal antibody 763.24T (IgG1) or 225.28S (IgG2a), respectively. These mice were also given a tracer dose of 125I LK2H10 or Ab-1, respectively. Specific tumor uptake of anti-HMWMAA antibodies was see in all cases. No drop in tumor or nontumor uptake was demonstrated for either of the tumor-specific or nonspecific monoclonal antibodies due to nonspecific monoclonal antibody pretreatment. These data suggest that high doses of isotype-matched unlabeled nonspecific monoclonal antibody given before 131I tumor-specific monoclonal antibody, will not enhance tumor imaging.
Present address: Hybritech, San Diego, CA, USA 相似文献
10.
Dirk Bosch Monica Scholten Cora Verhagen Jan Tommassen 《Molecular & general genetics : MGG》1989,216(1):144-148
Summary PhoE protein of Escherichia coli K12 is an outer membrane protein which is supposed to span the membrane sixteen times. By creating a deletion which removes the last membrane-spanning fragment and studying the localization of the truncated PhoE, we show that this fragment is indispensable for trimerization and outer membrane localization. In addition, circumstantial evidence for the proposed topology model of the protein was obtained. An insertion mutation in a region supposed to be cell surface-exposed, interferes with the binding of a monoclonal antibody which recognizes a cell surface-exposed epitope of the protein. 相似文献