全文获取类型
收费全文 | 4258篇 |
免费 | 228篇 |
出版年
2023年 | 9篇 |
2021年 | 64篇 |
2020年 | 26篇 |
2019年 | 26篇 |
2018年 | 66篇 |
2017年 | 52篇 |
2016年 | 81篇 |
2015年 | 150篇 |
2014年 | 174篇 |
2013年 | 272篇 |
2012年 | 286篇 |
2011年 | 300篇 |
2010年 | 179篇 |
2009年 | 182篇 |
2008年 | 278篇 |
2007年 | 288篇 |
2006年 | 263篇 |
2005年 | 245篇 |
2004年 | 252篇 |
2003年 | 267篇 |
2002年 | 249篇 |
2001年 | 47篇 |
2000年 | 48篇 |
1999年 | 56篇 |
1998年 | 47篇 |
1997年 | 43篇 |
1996年 | 30篇 |
1995年 | 40篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 50篇 |
1991年 | 42篇 |
1990年 | 49篇 |
1989年 | 42篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1972年 | 7篇 |
1970年 | 10篇 |
1969年 | 9篇 |
1968年 | 10篇 |
排序方式: 共有4486条查询结果,搜索用时 187 毫秒
1.
Yuji Inaba Yoshio Tanaka Sukemitsu Ishii Tomiaki Morimoto Kunihiko Sato Tuneyoshi Omori Minoru Matumoto 《Microbiology and immunology》1970,14(5):351-360
Replication of Ibaraki virus was not inhibited by 5-iodo-2′-deoxyuridine, indicating that the virus is an RNA virus. The virus was resistant to ether, chloroform and deoxycholate, sensitive to trypsin, very labile at acidic pH but stable at pH 6.4 or higher, and was resistant to repeated freezing and thawing. The virus was readily inactivated at 56 C or higher, was fairly stable at 37 C, and very stable at 4 C, while it rapidly lost infectivity when stored frozen at —20 C. The virus was readily sedimented by centrifugation at 40 000Xg for 60 min. It readily passed through membrane filters of 200 mμ pore size, passed through 100 μfilters but only with some titer loss and did not through 50 mμ filters. In these tests, the bluetongue virus used as a control behaved in the same manner as Ibaraki virus. These findings provide additional evidence for the similarity of Ibaraki virus to bluetongue virus which had been previously demonstrated on the basis of seasonal incidence, symptomatology and pathology of the diseases caused by these viruses and the behavior of the viruses in cell cultures, embryonated eggs and laboratory animals. The present study, however, provided no evidence for any serological relation between these two viruses. More Information is needed to reach a final decision on the classification of Ibaraki virus, particularly regarding the morphology of the virion, the doublestrandedness of the viral RNA and other basic features. 相似文献
2.
A new snake-eel,Apterichtus keramanus, is described on the basis of a single 276-mm TL specimen trawled from the coast of Kerama Islands, Okinawa Prefecture, Japan.
The species is unique in the genus in having the posterior nostril opening entirely inside the mouth and a dark band running
from the anteroventral margin of the eye to the upper lip. 相似文献
3.
Takahiro Ishii Tatsufumi Okino Yosuke Mino Hiroaki Tamiya Fuyuhiko Matsuda 《Plant Growth Regulation》2007,52(2):131-139
Starfish waste has been shown to be an effective compost material not only in the promotion of plant growth but also in terms
of having insecticidal activity. In the present study, plant growth regulation by chemicals from starfish was examined. The
aqueous fraction from a hot water extract of the starfish Asterias amurensis Lütken showed plant-growth activity, while the aqueous fraction from a methanol extract inhibited growth of Brassica campestris. The lipophilic fraction from the methanol extract also exhibited a plant growth-promoting effect. The active components
from each extract were identified. Asterubine from the hot water extract promoted plant growth. A ceramide from the lipophilic
fraction showed root growth promoting effect, and three glucocerebrosides had promotive effects on the entire plant. Asterosaponins
were identified as the main growth inhibitors in the aqueous fraction of the methanol extract. These active compounds from
starfish waste could be analyzed as potential plant growth regulators in agricultural applications in the future. 相似文献
4.
Tuneyoshi Omori Yuji Inaba Tomiaki Morimoto Yoshio Tanaka Hiroshi Kurogi Minoru Matumoto 《Microbiology and immunology》1967,11(2):133-142
Five strains of bovine diarrhea virus were isolated from Japanese cattle using bovine tissue cultures. These are the first isolations of this virus from Japanese cattle to be reported. Of importance is the finding that the new isolates, which are non-cytopathogenic, induce an exaltation of Newcastle disease virus in bovine testicular cell culture. This finding has provided a laboratory tool whereby the assay of the virus and its neutralizing antibody can readily be performed. 相似文献
5.
6.
Temperature-sensitive (ts) mutants of rat 3Y1 fibroblasts representing four separate complementation groups (3Y1tsD123, 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) are arrested mainly in the G1 phase when cells of randomly proliferating population at 33.8 degrees C are shifted to 39.8 degrees C (temperature arrest). We examined the time lag of the cellular entry into the S phase after release at 33.8 degrees C, both from the temperature arrest and from the arrest at 33.8 degrees C at a confluent cell density (density arrest). In the temperature-arrested cells, as the duration of temperature arrest increased, the time lag of entry into S phase after shift down to 33.8 degrees C was prolonged, in all four mutants. These observations suggest that the four different functional lesions, each causing arrest in the G1 phase, are also responsible for prolongation of the time lag of entry into the S phase in cells arrested in the G1 phase. The prolongation of the time lag in the temperature-arrested cultures was accelerated at a higher cell density, in medium supplemented with a lower concentration of serum, and at a higher restrictive temperature. In the density-arrested cells, as the duration of pre-exposure to 39.8 degrees C was increased, the time lag of entry into S phase at 33.8 degrees C after release from the arrest was drastically prolonged, in all four mutants. In 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203, when the density-arrested cells were prestimulated by serum at 39.8 degrees C for various periods of time, the time lag of entry into S phase after release from the density arrest at 33.8 degrees C was initially shortened, and then, prolonged progressively as the period of prestimulation increased. These findings, taken together with other data, show that all four ts defects affect cells in states ranging from the deeper resting to mid- or late-G1 phase. It is suggested that events represented by these four mutants are required for entry into the S phase and normally operate in parallel but not in sequence in cells in states ranging from the deeper resting to the mid- or late-G1 phases, though they may affect each other. 相似文献
7.
Dendritic and B-cell function during antibody responses in normal and immunodeficient (xid) mouse spleen cultures 总被引:1,自引:0,他引:1
Dendritic cells (DC) act as accessory cells for T-dependent antibody responses in two ways. One is to induce a class of stimulating factors (BSF) which allow B lymphocytes to respond to heterologous red cells as antigen. xid DC induce the production of these BSF, but xid B cells totally lack responsiveness. A second mechanism of DC function applies to red cell and haptenated-protein antigens. Here DC, helper T lymphocytes, and antigen-specific B cells interact in discrete clusters. Then the B cells become responsive to BSF. xid DC are fully active in this pathway, and xid B cells develop significant (10-20% of control) responses. This partial reduction in xid B-cell function could be due to the poor viability of xid lymphocytes in vitro. There is a comparable reduction in xid polyclonal responses to alloreactive helper T blasts. The other severe deficit in xid involves antibody formation to haptens on polysaccharide carriers. This response in normal mice is not influenced by DC or by BSF. The only similarity between DNP-Ficoll and RBC plus BSF responses is that both utilize B lymphocytes that do not associate with DC-T clusters, even though helper cells for DNP-Ficoll and for RBC are present in the culture. We conclude that DC function is not altered in xid. The main deficit seems to be in a B-cell activation pathway that is shared by polysaccharide carriers and some but not all BSF, and/or in a B-cell subpopulation that does not interact with carrier-specific helper cells. We speculate that this B-cell alteration primarily involves the Ig delta-poor marginal zone subpopulation of splenic B lymphocytes. 相似文献
8.
9.
Mikihiko Naito Ichiro Kudo Yukiko Mukai-Sato Susumu Tsushima Hiroaki Nomura Shoshichi Nojima Keizo Inoue 《Cancer immunology, immunotherapy : CII》1987,24(2):158-164
Summary Liposomes composed of chemically synthesized glyceroglycolipids, such as 1,2-dipalmityl-[-cellobiosyl-(1 3)]-glycerol (Cel-DAG), 1,2-dipalmityl-[-lactosyl-(1 3)]-glycerol, or 1,2-dipalmityl-[-maltosyl-(1 3)]-glycerol, were found to enhance protective immunity against transplantable tumor cells (sarcoma 180) in ICR mice. Peritoneal exudate cells prepared from mice treated in vivo with Cel-DAG showed cytostatic activity in vitro against the mouse leukemia cell line, EL-4. Adherent cells separated from this preparation showed similar activity. Peritoneal cells from polypeptone-injected mice acquired appreciable cytostatic activity when incubated in vitro in the presence of glyceroglycolipid liposomes. The adherent cell fraction alone showed rather weak cytostatic activity when pretreated with the glyceroglycolipids, and full activity was restored by supplementing with the nonadherent cell fraction. The ability of glycolipids to induce tumoricidal effects was affected by cholesterol content: with increasing cholesterol content, the activities decreased. Cholesterol-free glycolipid liposomes were taken more efficiently by macrophages than cholesterol-containing liposomes. Cholersterol modifies the surface property of glyceroglycolipid liposomes. Activation of macrophages is responsible for enhancement of protective immunity against tumor cells by injection of these glycolipids in vivo.This work was supported in part by Grants-in-Aid (Nos. 58010010, and 59870076) for Scientific Research from the Ministry of Education, Science and Culture of Japan 相似文献
10.
Junzou Hiratsuka Hiroaki Shimada Robert Whittier Takashi Ishibashi Masahiro Sakamoto Masao Mori Chihiro Kondo Yasuko Honji Chong-Rong Sun Bing-Yuan Meng Yu-Qing Li Akira Kanno Yoko Nishizawa Atsushi Hirai Kazuo Shinozaki Masahiro Sugiura 《Molecular & general genetics : MGG》1989,217(2-3):185-194
Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved
between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved
betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated
form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast
genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and
the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric
tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between
tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation
of repeated sequences near the inversion endpoints. 相似文献