全文获取类型
收费全文 | 20965篇 |
免费 | 1762篇 |
国内免费 | 5篇 |
出版年
2023年 | 78篇 |
2022年 | 210篇 |
2021年 | 438篇 |
2020年 | 235篇 |
2019年 | 311篇 |
2018年 | 437篇 |
2017年 | 358篇 |
2016年 | 657篇 |
2015年 | 1055篇 |
2014年 | 1193篇 |
2013年 | 1457篇 |
2012年 | 1793篇 |
2011年 | 1709篇 |
2010年 | 1096篇 |
2009年 | 969篇 |
2008年 | 1307篇 |
2007年 | 1345篇 |
2006年 | 1137篇 |
2005年 | 1101篇 |
2004年 | 1083篇 |
2003年 | 969篇 |
2002年 | 918篇 |
2001年 | 239篇 |
2000年 | 167篇 |
1999年 | 183篇 |
1998年 | 262篇 |
1997年 | 159篇 |
1996年 | 150篇 |
1995年 | 140篇 |
1994年 | 124篇 |
1993年 | 107篇 |
1992年 | 100篇 |
1991年 | 80篇 |
1990年 | 92篇 |
1989年 | 87篇 |
1988年 | 65篇 |
1987年 | 74篇 |
1986年 | 53篇 |
1985年 | 65篇 |
1984年 | 60篇 |
1983年 | 70篇 |
1982年 | 48篇 |
1981年 | 37篇 |
1980年 | 42篇 |
1979年 | 39篇 |
1978年 | 50篇 |
1977年 | 48篇 |
1976年 | 40篇 |
1974年 | 42篇 |
1973年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Marianne Horoyan Anne-Marie Benoliel Christian Capo Pierre Bongrand 《Cell biochemistry and biophysics》1990,17(3):243-256
We combined fluorescence labeling, digital image processing, and micromanipulation to investigate the intracellular events induced by inflicting a mechanical stress on rat basophilic leukemia cells. Our findings were as follows:
- Most cells displayed a localized calcium rise in response to micropipet aspiration. This represented an average threefold increase as compared to resting level, and it was observed during the first 10 s following aspiration. A slow return to initial level occurred within about 3 min. Further, this calcium rise involved a mobilization of intracellular stores, since it was not prevented by adding a calcium chelator into the extracellular medium.
- All micropipet-aspirated cells displayed a local accumulation of microfilaments, with a preferential localization in the cell protrusions or near the pipet tips.
- No absolute correlation was found between the localization of calcium rise and cytoskeletal accumulation.
- Cell deformability was decreased when intracellular calcium was maintained at a constant (high or low) level with ionomycin and/or EGTA.
142.
143.
Christian Damgaard 《Evolution; international journal of organic evolution》1996,50(4):1425-1431
The fixation rates of selfing rate modifiers were found by stochastic simulation in an infinite site model, including effects of several deleterious alleles with variable effects, which were randomly distributed in the genome without assuming any pollen discounting. Previous results on the evolution of selfing obtained by more precise methods were in this study further validated, and it was concluded that the effect of genetic associations on the evolution of mating systems is small except in the case of full pollen discounting. Furthermore, attention was given to the uneven distribution of the genetic load in the population, and the accompanying large among-genome variation in fixation rates. This among-genome variation will be of significance for the evolution of mating systems. 相似文献
144.
Christian Tessier Gian-Paolo Rossini Jean-François Pageaux Hélène Cohen Michel Lagarde Christian Laugier Jean-Michel Fayard 《FEBS letters》1996,390(3):311-314
Rat uterine stromal cells (UIII) express pancreatic type PLA2 (PLA2-I) receptor and internalize the enzyme bound to receptors. Here, we investigate the proliferating effect and alterations in binding of PLA2-I. There is a dramatic decline in PLA2-I binding in UIII cells as they progress from a nonconfluent proliferating state (40,000 sites/cell) to a confluent state (1300 sites/cell). Intracellular concentration of PLA2-I changed with the alteration in binding, suggesting that regulation in the PLA2 binding capacity may have important implications in growth control mechanisms. 相似文献
145.
146.
I. Martha Schlichtherle David S. Roos Judith L. Van Houten 《Molecular & general genetics : MGG》1996,250(6):665-673
We have cloned the first bifunctional gene dihydrofolate reductase-thymidylate synthase (DHFR-TS) from a free-living, ciliated protozoan,Paramecium tetraurelia, and determined its macronuclear sequence using a modified ligation-mediated polymerase chain reaction (PCR) that can be of general use in cloning strategies, especially where cDNA libraries are limiting. While bifunctional enzyme sequences are known from parasitic protozoa, none had previously been found in free-living protozoa. The AT-rich (68%) coding region spanning 1386 bp appears to lack introns. DHFR-TS localizes to a 500 kb macronuclear chromosome and is transcribed as an mRNA of 1.66 kb, predicted to encode a 53 kDa protein of 462 residues. The N-terminal one-third of the protein is encoded by DHFR, which is joined by a short junctional peptide of 12 amino acids to the highly conserved C-terminal TS domain. Among known DHFR-TS sequences, theP. tetraurelia gene is most similar to that fromToxoplasma gondii, based on primary sequence and parsimony analyses. The predicted secondary protein structure is similar to those of previously crystallized monofunctional sequences. 相似文献
147.
Spores of Aspergillus niger obtained by solid state fermentation on buckwheat seeds produced gluconic acid from glucose with a high yield, near 1.06 g gluconic acid/g glucose, close to the stoichiometric value. The reaction itself could be carried out either with purified biocatalyst or with the whole buckwheat medium resulting from spore production process. 200 g gluconic acid/L were obtained in 200 h with sequential feedings of glucose up to 190 g/L. 相似文献
148.
Nikolai G. Bukhov Christian Wiese Spidola Neimanis Ulrich Heber 《Photosynthesis research》1996,50(2):181-191
The light-induced induction of components of non-photochemical quenching of chlorophyll fluorescence which are distinguished by different rates of dark relaxation (qNf, rapidly relaxing and qNs, slowly relaxing or not relaxing at all in the presence brief saturating light pulses which interrupt darkness at low frequencies) was studied in leaves of spinach.After dark adaptation of the leaves, a fast relaxing component developed in low light only after a lag phase. Quenching increased towards a maximum with increasing photon flux density. This fast component of quenching was identified as energy-dependent quenching qE. It required formation of an appreciable transthylakoid pH and was insignificant when darkened spinach leaves received 1 s pulses of light every 30 s even though zeaxanthin was formed from violaxanthin under these conditions.Another quenching component termed qNs developed in low light without a lag phase. It was not dependent on a transthylakoid pH gradient, decayed exponentially with a long half time of relaxation and was about 20% of total quenching irrespective of light intensity. When darkened leaves were flashed at frequencies higher than 0.004 Hz with 1 s light pulses, this quenching also appeared. Its extent was very considerable, and it did not require formation of zeaxanthin. Relaxation was accelerated by far-red light, and this acceleration was abolished by NaF.We suggest that qNs is the result of a so-called state transition, in which LHC II moves after its phosphorylation from fluorescent PS II to nonfluorescent PS I. This state transition was capable of decreasing in darkened leaves the potential maximum quantum efficiency of electron flow through Photosystem II by about 20%.Abbreviations PFD
photon flux density
- PS
photosystem 相似文献
149.
ZmHox: a novel class of maize homeobox genes 总被引:2,自引:0,他引:2
Bettina Klinge Bärbel Überlacker Christian Korfhage Wolfgang Werr 《Plant molecular biology》1996,30(3):439-453
150.
Andreas Christian Dorothee Koberg Holger Preuschoft 《Pal?ontologische Zeitschrift》1996,70(3-4):591-601
The pelvis ofPlateosaurus is examined from a biomechanical point of view. The shape of the acetabulum in particular is analysed in order to determine the range of possible directions of the forces exchanged between femur and pelvis. These forces must have been more or less confined to a sagittal plane. From a quasi-static analysis under consideration of the major hip muscles ofPlateosaurus, a nearly but not fully extended posture of the hindlimbs can be deduced. The hip joints ofPlateosaurus and probably of some other dinosaurs with a narrow biacetabular width were balanced rather by adducting than by abducting muscles. 相似文献