全文获取类型
收费全文 | 2726篇 |
免费 | 130篇 |
国内免费 | 2篇 |
出版年
2023年 | 9篇 |
2022年 | 17篇 |
2021年 | 64篇 |
2020年 | 29篇 |
2019年 | 36篇 |
2018年 | 74篇 |
2017年 | 56篇 |
2016年 | 77篇 |
2015年 | 113篇 |
2014年 | 150篇 |
2013年 | 182篇 |
2012年 | 195篇 |
2011年 | 200篇 |
2010年 | 113篇 |
2009年 | 98篇 |
2008年 | 204篇 |
2007年 | 181篇 |
2006年 | 192篇 |
2005年 | 156篇 |
2004年 | 131篇 |
2003年 | 133篇 |
2002年 | 124篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 17篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 7篇 |
1970年 | 4篇 |
排序方式: 共有2858条查询结果,搜索用时 15 毫秒
961.
962.
Pekárová B Klumpler T Třísková O Horák J Jansen S Dopitová R Borkovcová P Papoušková V Nejedlá E Sklenář V Marek J Zídek L Hejátko J Janda L 《The Plant journal : for cell and molecular biology》2011,67(5):827-839
Multistep phosphorelay (MSP) signaling mediates responses to a variety of important stimuli in plants. In Arabidopsis MSP, the signal is transferred from sensor histidine kinase (HK) via histidine phosphotransfer proteins (AHP1–AHP5) to nuclear response regulators. In contrast to ancestral two‐component signaling in bacteria, protein interactions in plant MSP are supposed to be rather nonspecific. Here, we show that the C‐terminal receiver domain of HK CKI1 (CKI1RD) is responsible for the recognition of CKI1 downstream signaling partners, and specifically interacts with AHP2, AHP3 and AHP5 with different affinities. We studied the effects of Mg2+, the co‐factor necessary for signal transduction via MSP, and phosphorylation‐mimicking BeF3? on CKI1RD in solution, and determined the crystal structure of free CKI1RD and CKI1RD in a complex with Mg2+. We found that the structure of CKI1RD shares similarities with the only known structure of plant HK, ETR1RD, with the main differences being in loop L3. Magnesium binding induces the rearrangement of some residues around the active site of CKI1RD, as was determined by both X‐ray crystallography and NMR spectroscopy. Collectively, these results provide initial insights into the nature of molecular mechanisms determining the specificity of MSP signaling and MSP catalysis in plants. 相似文献
963.
Straka F Pirk J Pinďák M Skalský I Vančura V Cihák R Marek T Lupínek P Schorník D Mašín J Zeman M Skrobáková J Dorazilová Z Skibová J 《Physiological research / Academia Scientiarum Bohemoslovaca》2011,60(6):877-885
Cardiac resynchronization therapy is not commonly used in the early postoperative period in patients undergoing cardiac surgery who have left ventricular (LV) dysfunction and a history of heart failure. We performed a prospective randomized clinical trial to compare atrial synchronous right ventricular (DDD RV) and biventricular (DDD BIV) pacing within 72 hours after cardiac surgery in patients with an EF ≤35 %, a QRS interval longer than 120 msec and who had LV dyssynchrony detected by real-time three-dimensional echocardiography (RT3DE). Epicardial pacing was provided by a modified Medtronic INSYNC III pacemaker. An LV epicardial pacing lead was implanted on the latest activated segment of the LV based on RT3DE. The study included 18 patients with ischemic heart disease, with or without valvular heart disease (14 men, 4 women, average age 71 years). Patients undergoing DDD BIV pacing had a statistically significant greater CO and CI (CO 6.7±1.8 l/min, CI 3.4±0.7 l/min/m(2)) than patients undergoing DDD RV pacing (CO 5.5±1.4 l/min, CI 2.8±0.7 l/min/m(2)), p<0.001. DDD BIV pacing in the early postoperative period after cardiac surgery corrects LV dyssynchrony and has better hemodynamic results than DDD RV pacing. 相似文献
964.
We estimate the size of mechanostability for 318 multidomain proteins which are single-chain and contain up to 1021 amino acids. We predict existence of novel types of mechanical clamps in which interdomain contacts play an essential role. Mechanical clamps are structural regions which are the primary source of a protein's resistance to pulling. Among these clamps there is one that opposes tensile stress due to two domains swinging apart. This movement strains and then ruptures the contacts that hold the two domains together. Another clamp also involves tensile stress but it originates from an immobilization of a structural region by a surrounding knot-loop (without involving any disulfide bonds). Still another mechanism involves shear between helical regions belonging to two domains. We also consider the amyloid-prone cystatin C which provides an example of a two-chain 3D domain-swapped protein. We predict that this protein should withstand remarkably large stress, perhaps of order 800 pN, when inducing a shearing strain. The survey is generated through molecular dynamics simulations performed within a structure-based coarse grained model. 相似文献
965.
1. The absolute energy needs of small animals are generally lower than those of larger animals. This should drive higher mortality of larger animals, when the environmental conditions deteriorate. However, demonstration of the effect of energy constraints on survivals proved difficult, because the range of body mass within species is generally too small to produce enough variation for studying such an effect. An opportunity for an intraspecific study comes from weasels inhabiting the Bia?owie?a Forest (north-eastern Poland), which are characterized by a threefold variation in body mass. 2. We assumed that in summer larger weasel males are favoured by sexual selection, because they are more successful when competing for mates. We then tested whether they suffer higher mortality in winter, because they have difficulty finding sufficient food to satisfy their energy needs and/or because the additional foraging time would result in increased exposure to predation. 3. We measured daily energy expenditures (DEE) of overwintering weasel males using the doubly labelled water (DLW) technique. We constructed an energetic model predicting how individuals of different size are able to balance their energy budgets feeding on large and small prey while minimizing time spent hunting, thereby reducing their own exposure to predation. 4. The range of body mass in overwintering weasels predicted by our model corresponded very well with the distribution of prey body mass in three different habitats within our study area. Larger individuals were able to compensate for higher food requirements by using habitats with larger prey species than those available to smaller male weasels. This effectively offset the expected negative association between body mass and winter survival predicted from considerations of energy balance. 5. Our results show how energetic constraints affect body mass and spatial segregation of a species at the intra-specific level not only across large geographical ranges, but also within a relatively small area. 相似文献
966.
Juhásová B Mentel M Bhatia-Kiššová I Zeman I Kolarov J Forte M Polčic P 《FEBS letters》2011,585(17):2709-2713
Proteins of the Bcl-2 family regulate programmed cell death in mammals by promoting the release of cytochrome c from mitochondria in response to various proapoptotic stimuli. The mechanism by which BH3-only members of the family activate multidomain proapoptotic proteins Bax and Bak to form a pore in mitochondrial membranes remains under dispute. We report that cell death promoting activity of BH3-only protein Bim can be reconstituted in yeast when both Bax and antiapoptotic protein Bcl-X(L) are present, suggesting that Bim likely activates Bax indirectly by inhibiting antiapoptotic proteins. 相似文献
967.
The development of molecular techniques with fluorochromes has had an invaluable impact on discovering the nature of chromatin structure. Here, we show the application of a locus specific identifier probe (LSI) for precise and selective visualization of the horse IGF2 gene in the metaphase, interphase nuclei and sperm cells. Our study may be helpful for interpretation of results of interphase fluorescence in situ hybridization (I-FISH). We analyze and discuss the variation in the number and localization of FISH signals in somatic and sperm cells of horse. 相似文献
968.
Adamska M Leońska-Duniec A Maciejewska A Sawczuk M Skotarczak B 《Folia biologica》2011,59(3-4):115-120
Three DNA extraction kits were used, all without preliminary procedures, then DNA extraction was preceded with freeze/thaw cycles in three versions. A lack of desired effect resulted in the application of liquid nitrogen/water bath cycles before the use of the extractions in further experiments. The effectiveness of DNA extraction was measured by PCR signal and C(T) values of real time PCR. A comparison of the efficiency of various Cryptosporidium parvum undiluted oocyst treatments prior to DNA extraction with the use of three kits has shown that the best results were obtained after extraction of DNA with the QIAamp DNA Tissue Mini Kit (T kit), preceded by triple liquid nitrogen/water bath in 100 degrees C for 2 minutes and with overnight proteinase K digestion. After extraction with the T kit, the detection limit was 50 oocysts per 200 microl when effectiveness was evaluated with PCR and 10 oocysts in the case of real time PCR. 相似文献
969.
970.