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991.
New energetic materials: Synthesis and characterization of copper 5-nitriminotetrazolates 总被引:4,自引:0,他引:4
The energetic compounds 5-nitriminotetrazole (H2AtNO2, 1), 1-methyl-5-nitriminotetrazole (1MeHAtNO2, 2) and 2-methyl-5-nitraminotetrazole (2MeHAtNO2, 3), were reacted with Cu(NO3)2 · 3H2O and CuCl2 · 2H2O, respectively, in water as well as in aqueous ammonia solution. The syntheses yielded the complexes [Cu(HAtNO2)2(H2O)4] (4), [Cu(AtNO2)(NH3)3]2 (5), (NH4)2[Cu(AtNO2)2(H2O)2] (6), [Cu(1MeAtNO2)2(NH3)2] (7), [Cu(2-MeAtNO2)2(2-MeHAtNO2)2] (8), [Cu(2MeAtNO2)2]∞ (9), [Cu(2-MeAtNO2)2(NH3)2] (10), and [Cu(2MeAtNO2)2(NH3)4] · H2O (11). All complexes were characterized using low temperature single crystal X-ray diffraction, IR spectroscopy, elemental analysis, and differential scanning calorimetry. The magnetic properties of six of the complexes were investigated. Due to the energetic characters, the sensitivities towards impact and friction were investigated using the BAM drophammer and friction tester. The values range from “very sensitive”, comparable to primary explosives, to “insensitive” depending on the amount of water or ammonia coordinated. Since Cu(II) salts can be used for colorants in pyrotechnics, the combustions and flame colors were discovered to be intensively green. 相似文献
992.
Johann Sellner Axel Petzold Suwad Sadikovic Lorena Esposito Martin S. Weber Peter Heider Hans-Henning Eckstein Bernhard Hemmer Holger Poppert 《Neurochemical research》2009,34(11):1969-1974
This prospective study examined the value of serum neurofilament protein levels for detecting peri-operative brain damage
following carotid endarterectomy. An ELISA was used for quantification of neurofilament protein heavy chain (NfHSMI35) levels from patients undergoing endarterectomy for symptomatic (n = 17) and asymptomatic high-grade internal carotid artery stenosis (n = 30). All patients underwent diffusion-weighted brain imaging before and after the procedure. NfHSMI35 levels were significantly higher in patients with a symptomatic carotid artery stenosis (0.131 ng/ml) if compared to asymptomatic
patients (0.055 ng/ml, P = 0.01). However, serum NfHSMI35 levels were not related to signs of brain ischemia on routine brain imaging techniques. Our pilot data suggests that raised
NfHSMI35 serum levels in patients with symptomatic carotid artery disease may be a sensitive biomarker for diffuse ischemic damage
to the CNS. We conclude that NfHSMI35 failed to qualify as a biomarker for peri-operative brain injury in CEA and factors that may have compromised the validation
of this biomarker are discussed and need to be taken into account for the design of further studies. 相似文献
993.
994.
The fungal cyanide hydratases form a functionally specialized subset of the nitrilases which catalyze the hydrolysis of cyanide
to formamide with high specificity. These hold great promise for the bioremediation of cyanide wastes. The low resolution
(3.0 nm) three-dimensional reconstruction of negatively stained recombinant cyanide hydratase fibers from the saprophytic
fungus Neurospora crassa by iterative helical real space reconstruction reveals that enzyme fibers display left-handed D1 S5.4 symmetry with a helical rise of 1.36 nm. This arrangement differs from previously characterized microbial nitrilases which
demonstrate a structure built along similar principles but with a reduced helical twist. The cyanide hydratase assembly is
stabilized by two dyadic interactions between dimers across the one-start helical groove. Docking of a homology-derived atomic
model into the experimentally determined negative stain envelope suggests the location of charged residues which may form
salt bridges and stabilize the helix. 相似文献
995.
Morgan-Kiss RM Chan LK Modla S Weber TS Warner M Czymmek KJ Hanson TE 《Photosynthesis research》2009,99(1):11-21
Green sulfur bacteria (GSB) rely on the chlorosome, a light-harvesting apparatus comprised almost entirely of self-organizing
arrays of bacteriochlorophyll (BChl) molecules, to harvest light energy and pass it to the reaction center. In Chlorobaculum tepidum, over 97% of the total BChl is made up of a mixture of four BChl c homologs in the chlorosome that differ in the number and identity of alkyl side chains attached to the chlorin ring. C. tepidum has been reported to vary the distribution of BChl c homologs with growth light intensity, with the highest degree of BChl c alkylation observed under low-light conditions. Here, we provide evidence that this functional response at the level of the
chlorosome can be induced not only by light intensity, but also by temperature and a mutation that prevents phototrophic thiosulfate
oxidation. Furthermore, we show that in conjunction with these functional adjustments, the fraction of cellular volume occupied
by chlorosomes was altered in response to environmental conditions that perturb the balance between energy absorbed by the
light-harvesting apparatus and energy utilized by downstream metabolic reactions. 相似文献
996.
While one-to-one specificity between reef-dwelling hosts and symbiotic dinoflagellates of the genus Symbiodinium may occur, detailed examination of some hosts reveals that they contain multiple symbiont types. Individuals of the foraminifer
Amphisorus hemprichii living in Papua New Guinea contained mixed communities of Symbiodinium dominated by symbiont types in clades C and F. Moreover, the types showed a distinct pattern in their distribution across
the radius of the foraminifer, with clade F Symbiodinium more prevalent in the center of the host cell. The mixed community of symbionts and their pattern of distribution within
the foraminifer is likely the result of processes happening both inside the foraminifer and in its external environment. Persistent
mixed symbiont communities in foraminifera may be stabilized through benefits conferred by maintaining multiple symbiont lineages
for symbiont shuffling. Alternatively they may be stabilized through a heterogeneous internal host environment, partitioning
of symbiont functional roles or limitation of symbiont reproduction by the host. Six factors generally determine the presence
of any particular symbiont type within a foraminifer: mode of transmission, availability from the environment, recognition
by the host, regulation by the host, competition between lineages, and fitness of the holobiont.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
997.
Ricardo Brando Francielli Weber Santos Renata Oliveira Silvane Souza Roman Cristina Wayne Nogueira 《Journal of trace elements in medicine and biology》2009,23(4):324-333
The involvement of non-enzymatic antioxidant defenses in the protective effect of diphenyl diselenide (PhSe)2 on testicular damage caused by cadmium in mice was investigated. Mice received a single dose of CdCl2 (5 mg/kg, intraperitoneally). Thirty minutes after the CdCl2 injection, they received a single oral dose of (PhSe)2 (400 μmol/kg). Twenty-four hours after CdCl2 administration, blood samples were collected and mice were killed and had their testes dissected. Parameters in plasma (aspartate (AST) and alanine (ALT) aminotransferases and lactato dehydrogenase (LDH) activities as well as creatinine levels) were determined. The activity of δ-aminolevulinate dehydratase (δ-ALA-D), the levels of thiobarbituric acid-reactive substances (TBARS), ascorbic acid and nonprotein thiols (NPSH) and histological analysis were determined in collected samples. Results demonstrated that (PhSe)2 protected against toxicity induced by CdCl2 on δ-ALA-D activity, ascorbic acid and NPSH levels. (PhSe)2 protected against the increase in plasma AST, ALT and LDH activities caused by CdCl2. Testes of mice exposed to CdCl2 showed marked histopathological alterations that were ameliorated by administration of (PhSe)2. (PhSe)2 protected against toxicity induced by CdCl2 in testes of mice. Ascorbic acid and NPSH, non-enzymatic antioxidant defenses, are involved in the protective effect of (PhSe)2 against testicular damage caused by CdCl2 in mice. 相似文献
998.
Anuradha Seshadri Badrinath Dubey Michael H. W. Weber Umesh Varshney 《Molecular microbiology》2009,72(3):795-808
Ribosomal RNA (rRNA) contains a number of modified nucleosides in functionally important regions including the intersubunit bridge regions. As the activity of ribosome recycling factor (RRF) in separating the large and the small subunits of the ribosome involves disruption of intersubunit bridges, we investigated the impact of rRNA methylations on ribosome recycling. We show that deficiency of rRNA methylations, especially at positions 1518 and 1519 of 16S rRNA near the interface with the 50S subunit and in the vicinity of the IF3 binding site, adversely affects the efficiency of RRF-mediated ribosome recycling. In addition, we show that a compromise in the RRF activity affords increased initiation with a mutant tRNAfMet wherein the three consecutive G-C base pairs (29 GGG31 :39 CCC41 ), a highly conserved feature of the initiator tRNAs, were mutated to those found in the elongator tRNAMet (29 UCA31 :39 ψGA41 ). This observation has allowed us to uncover a new role of RRF as a factor that contributes to fidelity of initiator tRNA selection on the ribosome. We discuss these and earlier findings to propose that RRF plays a crucial role during all the steps of protein synthesis. 相似文献
999.
Maria Grandoch Maider López de Jesús Paschal A. Oude Weernink Artur-Aron Weber Karl H. Jakobs Martina Schmidt 《Cellular signalling》2009,21(4):609-621
Signaling by the B cell antigen receptor (BCR) is essential for B lymphocyte homeostasis and immune function. In immature B cells, ligation of the BCR promotes growth arrest and apoptosis, and BCR-driven balancing between pro-apoptotic extracellular signal-regulated kinase 1 and 2 (ERK1/2) and anti-apoptotic phosphoinositide 3-kinase-dependent Akt seems to define the final cellular apoptotic response. Dysfunction of these late BCR signaling events can lead to the development of immunological diseases. Here we report on novel cyclic AMP-dependent mechanisms of BCR-induced growth arrest and apoptosis in the immature B lymphoma cell line WEHI-231. BCR signaling to ERK1/2 and Akt requires cyclic AMP-regulated Epac, the latter acting as a guanine nucleotide exchange factor for Rap1 and H-Ras independent of protein kinase A. Importantly, activation of endogenously expressed Epac by a specific cyclic AMP analog enhanced the induction of growth arrest (reduced DNA synthesis) and apoptosis (nuclear condensation, annexin V binding, caspase-3 cleavage and poly-ADP-ribose polymerase processing) by the BCR. Our data indicate that cyclic AMP-dependent Epac signals to ERK1/2 and Akt upon activation of Rap1 and H-Ras, and is involved in BCR-induced growth arrest and apoptosis in WEHI-231 cells. 相似文献
1000.
The thermal dissipation probe was described in the early 1930s for the demonstration of a volume and mass flow of sap in the
conductive elements of the xylem in trees. It was subsequently developed further and is now widely used in physiological ecology
including measurements in the field. Thermal dissipation demonstrates the occurrence of sap flow and allows determination
of its velocity. Here we report simultaneous continuous measurements of sap flow using the thermal dissipation technique and
of transpiration by infrared gas analysis for diurnal and annual cycles in a deciduous and an evergreen oak tree, Quercus robur L. and Quercus turneri Willd., respectively, in a deciduous and an evergreen conifer, Larix decidua Mill. and Pinus griffithii McClell., respectively, and the host/mistletoe consortium of the deciduous linden Tilia mandschurica Rupr. & Max. and the evergreen Viscum album L. We show (1) that in diurnal cycles sap flow closely follows dynamic changes of the rate of transpiration elicited by daily
fluctuations of weather parameters (sunshine, cloudiness, air temperature and humidity), (2) that in annual cycles sap flow
reflects autumnal yellowing and shedding of leaves of the deciduous trees. We report for the first time comparative measurements
of sap flow towards mistletoe shoots and host branches in a parasite/host consortium. This demonstrates (3) that mistletoes
maintain considerably larger sap flow rates in their xylem conduits than the adjacent host branches dragging the transpiration
stream of their host towards their own shoots. We also show (4) that even after the deciduous host has shed its leaves and
itself does not transpire any more the evergreen mistletoe towards its shoots can maintain the persistence of a continuous
sap flow via the stem and branches of the host as long as frost does not prevent that. The work presented underlines the contention
that transpiration is the driving force for sap flow with continuous files of water in the xylem. It shows for the first time
that mistletoes direct the flow of water through host roots and stems towards its own shoots by not only performing stronger
transpiration as it is known from the literature but also by maintaining larger sap flow rates in the xylem conduits of its
stems. 相似文献