全文获取类型
收费全文 | 16280篇 |
免费 | 1260篇 |
国内免费 | 399篇 |
出版年
2024年 | 31篇 |
2023年 | 127篇 |
2022年 | 351篇 |
2021年 | 479篇 |
2020年 | 359篇 |
2019年 | 460篇 |
2018年 | 520篇 |
2017年 | 417篇 |
2016年 | 592篇 |
2015年 | 923篇 |
2014年 | 1057篇 |
2013年 | 1175篇 |
2012年 | 1454篇 |
2011年 | 1372篇 |
2010年 | 903篇 |
2009年 | 751篇 |
2008年 | 979篇 |
2007年 | 911篇 |
2006年 | 747篇 |
2005年 | 666篇 |
2004年 | 671篇 |
2003年 | 545篇 |
2002年 | 478篇 |
2001年 | 284篇 |
2000年 | 257篇 |
1999年 | 253篇 |
1998年 | 122篇 |
1997年 | 94篇 |
1996年 | 75篇 |
1995年 | 79篇 |
1994年 | 74篇 |
1993年 | 52篇 |
1992年 | 88篇 |
1991年 | 90篇 |
1990年 | 60篇 |
1989年 | 53篇 |
1988年 | 40篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 29篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 14篇 |
1977年 | 20篇 |
1976年 | 13篇 |
1975年 | 18篇 |
1974年 | 19篇 |
1970年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
以合成废水为基质,研究了采用硫酸盐还原-甲烷化两相厌氧新型工艺处理含高浓度硫酸盐有机废水的系统运行工艺条件.结果表明,酸化-硫酸盐还原反应器的适宜pH为6.5-7.0;500mg/l的S~(2-)使SRB的硫酸盐还原活性下降;208mg/l的[H_2S]_L抑制MPB活性的95.4%;推导出估算气提塔出水回流比R的模型;以得到的工艺条件为依据处理了含19200mg/1的SO_4~(2-)和29400mg/l COD的味精废水. 相似文献
102.
103.
对我国首座核电站配套工程的抽水蓄能电站水库蓄水初期的浮游生物进行了调查。蓄水水库由上下两水库组成。两水库的浮游生物种类组成显著不同。上水库浮游植物共记录到30种(属),浮游动物12种(属);下水库浮游植物19种(属);浮游动物25种(属)。上下两水库浮游生物数量均较贫乏,表明浮游生物群落尚处于初期发育阶段,但在局部浅水处已出现小规模的蓝藻水花,认为是水库蓄水初期必然的结果 相似文献
104.
105.
Summary Random copolymers of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) with a wide range of compositions varying from 0 to 83 mol% 4HB were produced by Alcaligenes latus from the mixed carbon substrates of 3-hydroxybutyric and 4-hydroxybutyric acids. The structure and physical properties of P(3HB-co-4HB) were characterized by1H and13C NMR spectroscopy, gel-permeation chromatography, and differential scanning calorimetry. The isothermal radial growth rates of spherulites of P(3HB-co-4HB) were much slower than the rate of P(3HB) homopolymer. The enzymatic degradation rates of P(3HB-co-4HB) films by a PHB depolymerase were strongly influenced by the copolymer composition. 相似文献
106.
107.
Masaaki Satoh Hiroichi Asagami Dongchon Kang Shigeki Minakami Koichiro Takeshige 《Molecular and cellular biochemistry》1995,152(2):159-165
A chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (fMLP), induced an acidification of cytosol by about 0.05 pH units in 30 sec followed by an alkalinization in human neutrophils. The quantitative contribution of acid production to the acidification was studied. The superoxide (O2
–) production stimulated by fMLP was not involved in the acidification because the production of acids in neutrophils from patients with chronic granulomatous disease who do not produce O2
–, was the same as that in normal neutrophils. The intracellular acidification was completely inhibited by deoxyglucose, suggesting that energy metabolism enhanced upon stimulation by fMLP might be the main source of the acidification. Although enhancement of the lactate formation by fMLP was 0.8 nmol/106 cells, which could lower intracellular pH by 0.08 pH units, the lactate production could not explain the initial acidification because the production of lactate started at 1 min after the stimulation while the intracellular acidification began immediately after the stimulation. Mitochondrial respiratory inhibitors such as KCN and rotenone had no effects on the fMLP-induced intracellular acidification. The fMLP-induced production of CO2 in 30 sec through the hexose monophosphate shunt was only 2.6 pmol/106 cells, which was calculated to decrease intracellular pH by only 0.0014. Thus, changes of energy metabolism induced by fMLP does not explain the acidification.Abbreviations fMLP
N-formyl-methionyl-leucyl-phenylalanine
- BCECF-AM
2,7-bis(carboxyethyl)carboxyfluorescein acetoxymethyl ester
- PMA
phorbol 12-myristate 13-acetate
- CGD
chronic granulomatous disease
- HMP
hexose monophosphate
- pHi
intracellular pH 相似文献
108.
Vinculin Proteolysis Unmasks an ActA Homolog for Actin-based Shigella Motility 总被引:2,自引:0,他引:2 下载免费PDF全文
Roney O. Laine William Zeile Fan Kang Daniel L. Purich Frederick S. Southwick 《The Journal of cell biology》1997,138(6):1255-1264
In polarized Madin-Darby canine kidney (MDCK) cells, the transferrin receptor (TR) is selectively delivered to the basolateral surface, where it internalizes transferrin via clathrin-coated pits and recycles back to the basolateral border. Mutant tailless receptors are sorted randomly in both the biosynthetic and endocytic pathways, indicating that the basolateral sorting of TR is dependent upon a signal located within the 61–amino acid cytoplasmic domain. To identify the basolateral sorting signal of TR, we have analyzed a series of mutant human TR expressed in MDCK cells. We find that residues 19–41 are sufficient for basolateral sorting from both the biosynthetic and endocytic pathways and that this is the only region of the TR cytoplasmic tail containing basolateral sorting information. The basolateral sorting signal is distinct from the YTRF internalization signal contained within this region and is not tyrosine based. Detailed functional analyses of the mutant TR indicate that residues 29–35 are the most important for basolateral sorting from the biosynthetic pathway. The structural requirements for basolateral sorting of internalized receptors from the endocytic pathway are not identical. The most striking difference is that alteration of G31DNS34 to YTRF impairs basolateral sorting of newly synthesized receptors from the biosynthetic pathway but not internalized receptors from the endocytic pathway. Also, mutations have been identified that selectively impair basolateral sorting of internalized TRs from the endocytic pathway without affecting basolateral sorting of newly synthesized receptors. These results imply that there are subtle differences in the recognition of the TR basolateral sorting signal by separate sorting machinery located within the biosynthetic and endocytic pathways. 相似文献
109.
Interaction of an adenovirus 14.7-kilodalton protein inhibitor of tumor necrosis factor alpha cytolysis with a new member of the GTPase superfamily of signal transducers. 总被引:3,自引:1,他引:2 下载免费PDF全文
The adenovirus (Ad) 14.7-kDa E3 protein (E3-14.7K), which can inhibit tumor necrosis factor alpha (TNF-alpha) cytolysis, was used to screen HeLa cell cDNA libraries for interacting proteins in the yeast two-hybrid system. A new member of the low-molecular-weight (LMW) GTP-binding protein family with Ras and ADP-ribosylation factor homology was discovered by this selection and has been named FIP-1 (14.7K-interacting protein). FIP-1 colocalized with Ad E3-14.7K in the cytoplasm especially near the nuclear membrane and in discrete foci on or near the plasma membrane. Its interaction with E3-14.7K was dependent on the FIP-1 GTP-binding domain. The stable expression of FIP-1 antisense message partially protected the cells from TNF-alpha cytolysis. FIP-1 was associated transiently with several unknown phosphorylated cellular proteins within 15 min after treatment with TNF-alpha. FIP-1 mRNA was expressed ubiquitously but at higher levels in human skeletal muscle, heart, and brain. In addition to homology to other LMW GTP-binding proteins, FIP-1 has regions of homology to two prokaryotic metalloproteases. However, there was no homology between FIP-1 and any of the recently isolated death proteins in the TNF-alpha or Fas/APO1 cytolytic pathway and no interaction with several members of the Bcl-2 family of inhibitors of apoptosis. These data suggest that FIP-1, as a cellular target for Ad E3-14.7K, is either a new intermediate on a previously described pathway or part of a novel TNF-alpha-induced cell death pathway. FIP-1 has two consensus sequences for myristoylation which would be expected to facilitate membrane association and also has sequences for Ser/Thr as well as Tyr phosphorylation that could affect its function. 相似文献
110.
Callus cultures and cell suspension cultures derived from Ginkgo biloba L. leaves produced ginkgolidc B. In cell suspension cultures, the production reached a maximum by the 13th day of subculture and followed by a sharp decrease. The medium of Murashige and Skoog induced the highest ginkgolide B content in cultures while the medium of Schenk and Hildebrandt promoted cell growth. For the maximal production of ginkgolide B, cells were cultured in Murashige and Skoog medium modified to contain 1.0 mg/l of -naphthaleneacetic acid, 0.1 mg/1 of kinetin, 30 g/1 sucrose and 1.25 mM potassium phosphate with a molar ratio of ammonium to nitrate ions of 1 3.Abbreviations B5
Gamborg et al (1968) medium
- GKB
Ginkgolide B
- MS
Murashige and Skoog (1962) medium
- NAA
-naphthaleneacetic aicd
- SH
Schenk and Hildebrandt (1972) medium 相似文献