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991.
Nakanishi H 《Molecular neurobiology》2003,27(2):163-176
There is accumulating evidence that intracellular and extracellular proteases of microglia contribute to various events in
the central nervous system (CNS) through both nonspecific and limited proteolysis. Cathepsin E and cathepsin S, endosomal/lysosomal
proteases, have been shown to play important roles in the major histocompatibility complex (MHC) class II-mediated antigen
presentation of microglia by processing of exogenous antigens and degradation of the invariant chain associated with MHC class
II molecules, respectively. Some members of cathepsins are also involved in neuronal death after secreted from microglia and
clearance of phagocytosed amyloid-β peptides. Tissue-type plasminogen activator, a serine protease, secreted from microglia
participates in neuronal death, enhancement of N-methyl-d-aspartate receptor-mediated neuronal responses, and activation of microglia via either proteolytic or nonproteolytic activity.
Calpain, a calcium-dependent cysteine protease, has been shown to play a pivotal role in the pathogenesis of multiple sclerosis
by degrading myelin proteins extracellulary. Furthermore, matrix metalloproteases secreted from microglia also receive great
attention as mediators of inflammation and tissue degradation through processing of pro-inflammatory cytokines and damage
to the blood-brain barrier. The growing knowledge about proteolytic events mediated by microglial proteases will not only
contribute to better understanding of microglial functions in the CNS but also may aid in the development of protease inhibitors
as novel neuroprotective agents. 相似文献
992.
993.
Noriyuki?OsadaEmail author Shinji?Sugiura Koji?Kawamura Michiko?Cho Hiroshi?Takeda 《Ecological Research》2003,18(6):711-723
We investigated the flowering phenology, pollinator visitation, and fruit set of 25 animal-pollinated woody species in a warm temperate secondary forest in Japan. Various species flowered sequentially from February to October. The principal pollinators were bumblebees, honey-bees, flies and/or beetles and birds; bumblebees and flies/beetles pollinated most trees. The duration of flowering was shorter for species that bloomed in the middle of the season than it was for species that bloomed earlier or later in the season. The timing of flowering was more synchronous within species that had a shorter flowering duration; this was also detected when phylogenetically independent contrasts were calculated. This could be important for the effective pollination of species with a short flowering duration because such species bloom sequentially over a short period of less than 1month around May. Fruit set was related not to pollinator type, sex expression, flowering sequence (in order of the date of peak flowering) or flowering duration, but to the relative abundance of the species in the forest. This correlation was detected for fly- and beetle-pollinated species but not for bumblebee-pollinated species. Thus, relatively rare plant species with opportunistic pollinators might experience limited fruit set because of insufficient pollinator services. Bagging experiments conducted on eight hermaphrodite species revealed that the fruit set of bagged flowers was nearly zero, lower than that of control flowers. These results indicate the importance of pollinators for successful reproduction and thus for the coexistence of plants in this secondary forest. 相似文献
994.
995.
The tubulin-colchicine complex instead of tubulin was used in an imidazole buffer throughout experiments. The interaction with calcium was examined, especially in the GDP state. The high affinity sites of calcium took part in the polymerization of the complex in the GTP state, while the low ones participated in the depolymerization. The complex had 2 high affinity sites with the dissociation constant of 11.5 x 10(-6) M, and 16 low affinity sites with the dissociation constant of 2.27 x 10(-4) M in the GTP state. In the case of GDP state, the dissociation constant of the high affinity site was 7.2 x 10(-6) M, and the low affinity site was not observed. The ultracentrifugal experiment indicated a little compact structure in the GTP state compared with the GDP state. This agreed with the results of calcium binding. 相似文献
996.
Organogenesis of heart-vascular system derived from mouse 2 cell stage embryos and from early embryonic stem cells in vitro 总被引:2,自引:0,他引:2
Regenerative medical treatment with embryonic stem cells (an ES cell) is a goal for organ transplantation. Structures that are tubular in nature (i.e. blood capillaries) were induced from early embryonic stem (EES) cells in vitro using embryotrophic factor (ETFs). In addition, cardiac muscle cells could be identified as well. However, differentiation of EES cells into a complete cardiovascular system was difficult because 3 germ layer primordial organs are directed embryologically in various ways and it is not possible to guide only cardiovascular organs. Thus, we introduced ETFs after the formation of an embryoid body and were successful in cloning cell clusters that beat, thus deriving only cardiovascular organs. The application of this to the treatment of various cardiovascular diseases is promising. 相似文献
997.
Embryological characters of Siparunaceae, which are poorly understood, were studied on the basis of two constituent genera,
an African Glossocalyx and a South American Siparuna, to better understand their evolution within Laurales. These two genera have many embryological characteristics in common
with the other lauralean families. Noticeably, they share the multi-celled ovule archesporium (uncertain in Glossocalyx) as a synapomorphy with all the other lauralean families except Lauraceae, the anthers dehisced by valves as a synspomorphy
with all the other lauralean families except Calycanthaceae and Monimiaceae, and the bisporangiate anther as a synapomorphy
with Gomortegaceae and Atherospermataceae. Siparunaceae are, however, distinct from all other laularean families in having
unitegmic ovules that were derived from bitegmic ovules, probably due to an elimination of the outer integument. Likewise,
the lack of the testa (i.e., developed outer integument), the "endotegmic" seed coat, and the perichalazal seed at maturity
are also characteristics of Siparunaceae. Within the family, Siparuna differs from Glossocalyx in having plural tetrads of megaspores and plural, starchy-rich, one-nucleate, tubular embryo sacs (autapomorphies). On the
other hand, Glossocalyx is characterized by having bilaterally flattened seeds (autapomorphy). Although functional aspects of those autapomorphies
are uncertain, both Glossocalyx and Siparuna show evolution in different embryological characters. 相似文献
998.
Although the Dendranthema zawadskii complex has been known to comprise a series of polyploids (4x, 6x, 8x), we found diploid individuals (with 2 n=18) to occur in four populations of D. zawadskii var. latilobum in the southern region of Korea. Karyotypes of metaphase chromosomes were diverse because numbers of metacentric, submetacentric, and acrocentric chromosomes differ even within a population. A total of 17 karyotypes were found in 31 diploid individuals collected from the four populations. The karyotypes were also diverse in the presence or absence of chromosomes with a secondary constriction on a short or long arm and, if present, in the number of such chromosomes. They were further diverse in the presence or absence of non-homologous chromosome(s), the presence or absence of a chromosome with a satellite, and, if present, how many and where satellites are present. Almost the same pattern of diversity was found in diploid individuals (with 2 n=18) of D. boreale and D. indicum as well, irrespective of whether they occur together with D. zawadskii var. latilobum or not. Structural features of chromosomes in the variously different karyotypes suggest that reciprocal translocation and the hybridization between individuals with different karyotypes had repeatedly occurred not only in D. zawadskii var. latilobum, but also in D. boreale and D. indicum. Morphologically intermediate individuals between D. zawadskii var. latilobum and D. indicum suggests that the hybridization occur with different species as well. 相似文献
999.
Kajiya A Koyama Y Mita T Mega T Hase S Kawakami T Honda E Munakata H Isemura M 《Bioscience, biotechnology, and biochemistry》2003,67(9):2051-2054
To develop a convenient method to isolate lectins, we prepared an affinity gel by coupling plasma proteins with agarose beads under conditions where the pH did not exceed 7.5. The validity of the use of this affinity gel in combination with elution using a hapten saccharide was confirmed by isolation of concanavalin A from Jack bean meal. Successful application of the method was demonstrated by isolation of two novel vegetable lectins from udo (Aralia cordate) and wasabi (Wasabia japonica). The method would be useful to isolate new lectins from various sources including plant and animal tissues. 相似文献
1000.
Chai W Sakamaki H Kitanaka S Saito M Horiuchi CA 《Bioscience, biotechnology, and biochemistry》2003,67(1):218-220
The biological degradation of 2,2-bis(4-hydroxyphenol)propane (1; bisphenol A, BPA), a representative endocrine disruptor, was studied with plant-cultured cells of Caragana chamlagu. An initial BPA concentration of 425 microM in an aqueous solution was degraded by C. chamlagu at 25 degrees C for 2 days in the dark, and two intermediates were then completely dissipated after 10 days. 相似文献