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81.
Juana J. Perdomo Pierre Gounon Madeleine Schaeverbeke Jean Schaeverbeke Vanina Groult Marie P. Jacob Ladislas Robert 《Journal of cellular physiology》1994,158(3):451-458
Mesenchymal cells (fibroblasts, smooth muscle cells) and endothelial cells were shown to interact with elastin fibers. The strong adhesion of elastin fibers to these cells is mediated by a cell membrane complex with a major glycoprotein component of 120 kDa designated as elastonectin. This interaction was studied by transmission electron microscopy (TEM) and immunocytochemical techniques using antibodies raised against the elastin adhesive proteins. When fibroblasts and smooth muscle cells were cultured in presence of elastin fibers, TEM showed an adhesion mechanism that takes place over several sites along the plasma membrane of these cells. Endothelial cells showed a very close association with elastin, emitting “pseudopodia” that embody the fibers. TEM, indirect immunofluorescence, immunoperoxidase, and confocal microscopy showed the presence and localization of cell membrane components synthesized in large quantities when cells were incubated in presence of elastin. Cells without elastin fibers barely revealed the adhesive membrane complex. These results confirm and extend previous findings concerning the presence of an inducible cell membrane complex that mediates the adhesion of elastin fibers to these cell types. © 1994 Wiley-Liss, Inc. 相似文献
82.
83.
Effects of sub-minimal inhibitory concentrations of EDTA on growth of Escherichia coli and the release of lipopolysaccharide 总被引:1,自引:0,他引:1
Christophe Pelletier Pierre Bourlioux Jean van Heijenoort 《FEMS microbiology letters》1994,117(2):203-206
Abstract Release of lipopolysaccharide from E. coli was studied in the presence of sub-minimal inhibitory concentrations of ethylenediaminetetraacetic acid (EDTA). In untreated cells no release was detected with 50 mM Mg2+ in the medium, but a steady release of over 50% of the synthesized lipopolysaccharide was observed with 0.1 mM Mg2+ . EDTA at MIC/8 led to a 2- to 3-fold higher release, presumably by an adjustment of the concentration of unchelated Mg2+ to a value still sustaining normal growth but giving rise to a highly unstable outer membrane. No structural difference was observed between cell-bound and released lipopolysaccharide. 相似文献
84.
Isabelle Chevalot Athanase Visvikis Pierre Nabet Jean-Marc Engasser Annie Marc 《Cytotechnology》1994,16(2):121-129
Recombinant Chinese Hamster Ovary (CHO) cells, engineered for the production of human gamma-glutamyl transferase (GGT), have been grown on Cytodex 1 microcarriers, as aggregates, or as single cells in suspension after adaptation. GGT is a membrane bound enzyme which was not secreted during the culture period. The maximal enzyme activity was found to be directly related to the achieved maximal cell density. Culture of CHO on microcarriers yielded the fastest growth, with a specific growth rate of 0.04 h–1, the highest cell density (near 1.3×106 cells ml–1), and the highest enzyme activity around 300 mU ml–1, which corresponded to a specific cellular level of 20 mU 10–5 cells. GGT could also be produced by growing CHO cells in suspension as single cells or as aggregates. Under these conditions, however, the specific CHO growth rate was significantly slower and the GGT level per cell was divided by a factor 6. Growing CHO cells without microcarriers also resulted in differences in cell metabolism, with a higher conversion yield of glutamine into ammonia, and a higher cell lysis. The catalytic kinetic constants of the enzyme were found identical for the three culture systems. 相似文献
85.
Cobalt determinations in biological fluids are of great interest in biological or toxicological research programs. Cobalturia
is often chosen as an indicator for a biological monitoring program in occupational exposure to cobalt dusts. The method described
here derives from the IUPAC reference method for nickel determination. It enables cobaltemia and cobalturia to be measured
in small samples (1 mL). The mean usual values for cobalt in biological fluids are very low (2.7 nmol L−1 for serum and 6.7 nmol L−1 for urine), and therefore, thus require an analytical procedure with preconcentration and extraction. The sample is mineralized
by wet acid digestion. After digestion, inorganic cobalt is extracted in form of ammonium pyrrolidine dithiocarbamate complex
into isobutyl methyl ketone and measured in the organic layer by electrothermal atomic absorption spectrometry.
The analytical parameters are described in detail. The extraction output is about 99%. The detection limits are 1.93 and 1.89
nmol L−1 for serum and urine, respectively. Sensitivity (expressed as the concentration that gives a 0.044 absorbance) is 3.4 nmol
L−1 for serum and 3.3 nmol L−1 for urine.
Within-run precision ranged between 3.9 and 2.5% (coefficients of variation) for serum and 4.2 and 1.1% for urine, at 87 and
136 nmol L−1 levels, respectively. Between-run precision ranged between 4.3 and 3.3% (coefficients of variation) for serum and 4.2 and
2.3% for urine, at 87 and 136 nmol L−1 levels, respectively. At very low concentration, 5.7 nmol L−1 for serum and 2.5 nmol L−1 for urine, the between-run precision is, respectively, 19.5 and 28%.
Linearity is effective between 0 and 272 nmol L−1. Interferences and matrix effects are negligible for urine, serum, or plasma samples without hemoglobin. The method is easily
applicable for routine determinations. 相似文献
86.
Pierre Bondil 《Andrologie》1994,4(3):341-345
Defined as a blocked erection, longer than 4 hours, after an intracavernous injection of erectogenic drugs, the pharmacological prolonged erection (PPE) is the most frequent complication of this impotence treatment. The main risk of this priapic erection lies in the occurence of an acute ischemia of cavernous bodies. Although this risk is inconstant, any blocked erection must be treated before the 4th hour for avoiding any erectile tissue lesions. The indications of the various medical methods are dependent on the length of the PPE and/or intense physical effort, and/or penile freezing (using vapocoolant or ice application), must be always first used, owing to both their simplicity and efficiency when they are early made. These “little means” can also be easily teached to the patient using cavervous self-injection. In case of failure, another medical methods can be tried as cavernous decompressive puncture and/or, oral or mainly intracavernous pharmacological detumescence. In the absence of pain and hypertension or heart diseases, puncture of pharmacological detumescence can be equally used. If not, the cavernous puncture must be always first tried, combined with the study of cavernous blood gas. In the great majority of cases, this medical treatment is sufficient if early done. Its rare failures require a rapid surgical treatment, particularly in case of anoxic suffering. Presently, the PPE prevention is possible thanks to a better information of both patients and physicians using intracavernous injections, and also, to the recent use of less dangerous drugs. 相似文献
87.
Corine Vernet Joëlle Boretto Marie-Geneviève Mattéi Masahide Takahashi Lucinda J. W. Jack Ian H. Mather Sylvie Rouquier Pierre Pontarotti 《Journal of molecular evolution》1993,37(6):600-612
Summary During a search for novel coding sequences within the human MHC class I region (chromosome 6p21.3), we found an exon (named B30-2) coding for a 166-amino-acid peptide which is very similar to the C-terminal domain of several coding sequences: human 52-kD Sjögren's syndrome nuclear antigen A/Ro (SS-A/Ro) and ret finger protein (RFP), Xenopus nuclear factor 7 (XNF7), and bovine butyrophilin. The first three of these proteins share similarities over the whole length of the molecule whereas butyrophilin is similar in the C-terminal domain. The N-terminal domain of butyrophilin is similar to rat myelin/oligodendrocyte glycoprotein (MOG) and chicken B blood group system (B-G) protein. These domains are components of a new subfamily of the immunoglobulin superfamily (IgSF). Butyrophilin is thus a mosaic protein composed of the MOG/B-G Ig-like domain and the C-terminal domain of 52-kD SS-A/Ro, RFP, and XNF7 (1330-2-like domain). Moreover, in situ hybridization shows that RFP, butyrophilin, and MOG map to the human chromosome 6p2l.3-6p22 region and are thus close to the MHC class I genes. It is therefore possible that the butyrophilin gene is the product of an exon shuffling event which occurred between ancestors of the RFP and MOG genes. To our knowledge, this is the first example of the colocalization of a chimeric gene and its putative progenitors. Finally, regulatory protein T-lymphocyte 1 (Rpt-1) shares similarities with the N-terminal halves of RFP, 52-kD SS-A/Ro, and XNF7, but not with the B30-2-like domain. We show that the ancestral Rpt-l gene evolved by overprinting.
Correspondence to: P. Pontarotti 相似文献
88.
We study the influence of the individual behaviour of animals on predator-prey models. Populations of preys and predators are divided into sub-populations corresponding to different activity classes. The animals are assumed to do many activities all day long such as searching for food of different types. The preys are more vulnerable when doing some activities during which they are very exposed to predators attacks rather than for others during which they are hidden. We study activity sequences of the animals and also the effect of a change in the average individual behaviour of the animals on Lotka-Volterra prey-predator interactions. Numerical simulations are realized for the whole sets of equations (governing the subpopulations) and are compared to the simulations of the reduced sets of equation (governing the populations). We look for the validity of the method with respect to a scaling factor which measures the differences between the two time scales associated to the fast-varying variables and to the slow-time varying global variables. It is shown that when the two time scales differ of about two orders of magnitude, the approximation is satisfying. 相似文献
89.
Lucie Mahaut Philippe Choler Pierre Denelle Eric Garnier Wilfried Thuiller Jens Kattge Servane Lemauviel-Lavenant Sandra Lavorel François Munoz Delphine Renard Josep M. Serra-Diaz Nicolas Viovy Cyrille Violle 《Global Ecology and Biogeography》2023,32(4):561-572
Aim
It is crucial to monitor how the productivity of grasslands varies with its temporal stability for management of these ecosystems. However, identifying the direction of the productivity–stability relationship remains challenging because ecological stability has multiple components that can display neutral, positive or negative covariations. Furthermore, evidence suggests that the direction of the productivity–stability relationship depends on the biotic interactions and abiotic conditions that underlie ecosystem productivity and stability. We decipher the relationships between grassland productivity and two components of its stability in four habitat types with contrasting environments and flora.Location
France.Time period
2000–2020.Major taxa
Grassland plant species.Methods
We used c. 20,000 vegetation plots spread across French permanent grasslands and remotely sensed vegetation indices to quantify grassland productivity and temporal stability. We decomposed stability into constancy (i.e., temporal invariability) and resistance (i.e., maximum deviation from average) and deciphered the direct and indirect effects of abiotic (namely growing season length and nitrogen input) and biotic (namely plant taxonomic diversity, trait diversity and community-weighted mean traits) factors on productivity–stability relationships using structural equation models.Results
We found a positive relationship between productivity and constancy and a negative relationship between productivity and resistance in all habitats. Abiotic factors had stronger effects on productivity and stability compared with biotic factors. A longer growing season enhanced grassland productivity and constancy. Nitrogen input had positive and negative effects on grassland productivity and resistance, respectively. Trait values affected the constancy and resistance of grassland more than taxonomic and trait diversity, with effects varying from one habitat to another. Productivity was not related to any biotic factor.Main conclusions
Our findings reveal how vital it is to consider both the multiple components of stability and the interaction between environment and biodiversity to gain an understanding of the relationships between productivity and stability in real-world ecosystems, which is a crucial step for sustainable grassland management. 相似文献90.
Sophie Stettler Nuchanard Chiannilkulchai Sylvie Hermann-Le Denmat Dominique Lalo François Lacroute André Sentenac Pierre Thuriaux 《Molecular genetics and genomics : MGG》1993,238(1-2):169-176
The pem locus, which is responsible for the stable maintenance of the low copy number plasmid R100, contains the pemK gene, whose product has been shown to be a growth inhibitor. Here, we attempted to isolate mutants which became tolerant to transient induction of the PemK protein. We obtained 20 mutants (here called pkt for PemK tolerance), of which 9 were temperature sensitive for growth. We analyzed the nine mutants genetically and found that they could be classified into three complementation groups, pktA, pktB and pktC, which corresponded to three genes, ileS, gltX and asnS, encoding isoleucyl-, glutamyl- and asparaginyl-tRNA synthetases, respectively. Since these aminoacyl-tRNA synthetase mutants did not produce the PemK protein upon induction at the restrictive temperature, these mutants could be isolated because they behaved as if they were tolerant to the PemK protein. The procedure is therefore useful for isolating temperature-sensitive mutants of aminoacyl-tRNA synthetases. 相似文献