全文获取类型
收费全文 | 8208篇 |
免费 | 428篇 |
国内免费 | 6篇 |
出版年
2022年 | 53篇 |
2021年 | 77篇 |
2020年 | 63篇 |
2019年 | 64篇 |
2018年 | 94篇 |
2017年 | 85篇 |
2016年 | 181篇 |
2015年 | 254篇 |
2014年 | 267篇 |
2013年 | 581篇 |
2012年 | 495篇 |
2011年 | 550篇 |
2010年 | 331篇 |
2009年 | 308篇 |
2008年 | 520篇 |
2007年 | 550篇 |
2006年 | 503篇 |
2005年 | 492篇 |
2004年 | 578篇 |
2003年 | 449篇 |
2002年 | 459篇 |
2001年 | 128篇 |
2000年 | 106篇 |
1999年 | 105篇 |
1998年 | 106篇 |
1997年 | 88篇 |
1996年 | 81篇 |
1995年 | 83篇 |
1994年 | 69篇 |
1993年 | 68篇 |
1992年 | 82篇 |
1991年 | 74篇 |
1990年 | 58篇 |
1989年 | 64篇 |
1988年 | 60篇 |
1987年 | 45篇 |
1986年 | 50篇 |
1985年 | 41篇 |
1984年 | 38篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 33篇 |
1980年 | 37篇 |
1979年 | 24篇 |
1978年 | 21篇 |
1977年 | 27篇 |
1976年 | 22篇 |
1975年 | 19篇 |
1973年 | 17篇 |
1972年 | 15篇 |
排序方式: 共有8642条查询结果,搜索用时 62 毫秒
91.
Satoshi Muraki Masahiro Yamasaki Yoshito Ehara Kunio Kikuchi Kunihiro Seki 《European journal of applied physiology and occupational physiology》1996,74(5):481-483
The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed
lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed
graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC)
were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen
uptake and peak heart rate was 1.41 ± 0.22 1·min−1 and 171.6 ± 19.2 beats·min−1, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest.
These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE. 相似文献
92.
Takeshi K. Watanabe Toyomasa Katagiri Mikio Suzuki Fumio Shimizu Tsutomu Fujiwara Naohide Kanemoto Yusuke Nakamura Yoshikatsu Hirai Hiroumi Maekawa Ei-ichi Takahashi 《Genomics》1996,38(3):273
From a human fetal-brain cDNA library we isolated two novel genes encoding peptides containing six EGF-like repeats. Both showed significant homologies with nel, a gene strongly expressed in neural tissues of chicken. The cDNAs, designated NELL1 (nel-like, type 1) and NELL2 (nel-like, type 2), contained open reading frames encoding 810 and 816 amino acids, respectively. NELL2 is strongly expressed in brain of adult and fetus but only weakly in fetal kidney. NELL1 and NELL2 were mapped by FISH to chromosomal bands 11p15.1–p15.2 and 12q13.11–q13.12, respectively. 相似文献
93.
Satoshi Iuchi Kazuko Yamaguchi-Shinozaki Takeshi Urao Kazuo Shinozaki 《Journal of plant research》1996,109(4):415-424
Ten cDNAs for drought-inducible genes were isolated using differential screening of a cDNA library prepared from 10-hr dehydrated
cowpea plants,Vigna unguiculata (S. Iuchi, K. Yamaguchi-Shinozaki, T. Urao, T. Terao, K. Shinozaki; Plant Cell Physiology, 1996 in press). Two of the cDNA
clones, designated CPRD12 and CPRD46, were sequenced and characterized. The CPRD12 and CPRD46 cDNAs encode putative proteins
related to nonmetallo-short-chain alcohol dehydrogenase (CPRD12) and chloroplastic lipoxygenase (CPRD46). Northern blot analysis
revealed that these genes are induced by high-salinity stress and exogenous abscisic acid, but not by cold stress. The CPRD46
gene is also responsive to heat stress and methyl jasmonate and salicylic acid. Genomic Southern blot analysis suggested that
CPRD12 constitutes a small gene family, but that CPRD46 is a single copy gene. We discuss the possible functions of these
two CPRD gene products under drought stress. 相似文献
94.
95.
96.
97.
By means of an in vivo brain microdialysis, the effect of different concentrations of physostigmine on the acetylcholine level in the dialysate of rat frontal cortex was studied. Perfusion of the various degrees of physostigmine (eserine) concentration (10 nM−10 μM) into the cortex through the dialysis membrane increased the basal acetylcholine level in a dose-dependent manner. In the presence of 10 nM, 0.1 μM and 10 μM physostigmine in the perfusate, systemic treatment with scopolamine (0.5 mg/kg, i.p.) increased 200, 270 and 510%, respectively, the relative acetylcholine level in the dialysates in comparison with the corresponding basal levels, while in the absence of physostigmine the treatment increased it only 40%. From these results, it appears that perfusion of physostigmine at a variety of concentrations, changes not only the basal level of acetylcholine induced by the inhibition of acetylcholinesterase but also the relative acetylcholine output induced by systemic treatment with scopolamine. 相似文献
98.
Shinji Tokuyama Hiroyuki Miya Kazunori Hatano Takeshi Takahashi 《Applied microbiology and biotechnology》1994,40(6):835-840
A novel enzyme, N-acylamino acid racemase, was purified to homogeneity from Streptomyces atratus Y-53 and characterized. This enzyme catalyzes the interconversion of optically active N-acylamino acids. The relative molecular mass (Mr) of the enzyme was estimated to be about 41 000 and 244 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, respectively, indicating that the enzyme is composed of six subunits with an equal Mr. The enzyme showed a broad substrate specificity toward N-acylamino acids, such as N-acetylmethionine, N-chloroacetylphenylalanine and N-chloroacetylvaline. The apparent Michaelis constant (Km) values for N-acetyl-l-methionine and N-acetyl-d-methionine were calculated to be 15.2 and 5.6 mm, respectively. Enzyme activity was markedly enhanced by divalent metal ions, such as Co2+, Mg2+ and Mn2+, and was inhibited by metal-chelating reagent, indicating that the enzyme is a metalloenzyme. We propose to name the enzyme N-acylamino acid racemase (acylamino acid racemase).
Correspondence to: S. Tokuyama 相似文献
99.
Substrate Preference in a Strain of Megasphaera elsdenii, a Ruminal Bacterium, and Its Implications in Propionate Production and Growth Competition
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The NIAH 1102 strain of Megasphaera elsdenii utilized lactate in preference to glucose when the two substrates were present. Even when lactate was supplied to cells fermenting glucose, the cells switched substrate utilization from glucose to lactate and did not utilize glucose until lactate decreased to a low concentration (1 to 2 mM). Since substrate utilization was shifted gradually without intermittence, typical diauxic growth was not seen. The cyclic AMP content did not rise markedly with the shift in substrate utilization, suggesting that this nucleotide is not involved in the regulation of the shift. It was unlikely that propionate was produced from glucose, which was explicable by the fact that lactate racemase activity dropped rapidly with the exhaustion of lactate and cells actively fermenting glucose did not possess this enzyme. A coculture experiment indicated that M. elsdenii NIAH 1102 is overcome by Streptococcus bovis JB1 in the competition for glucose, mainly because M. elsdenii NIAH 1102 is obliged to utilize lactate produced by S. bovis JB1; i.e., glucose utilization by M. elsdenii NIAH 1102 is suppressed by the coexistence of S. bovis JB1. 相似文献
100.
Hideo Yamanari Tatsuo Suganuma Takeshi Iwamura Norio Kitamura Shoji Taniguchi Toshiaki Setoguchi 《Experimental cell research》1994,211(2)
The interaction between the extracellular matrix and human tumor-cell clones S2-013 and S2-020, derived from a pancreatic cancer cell line (SUIT-2), was examined in vitro, using various cell differentiation-promoting matrices in two- and three-dimensional cultures. S2-013 cells (well-differentiated tubular adenocarcinoma in xenografts in nude mice) cultured in Matrigel formed glandular structures. Ultrastructural observation revealed a morphological polarity of cells and a distinct basal lamina. On the other hand, S2-020 cells (poorly differentiated tubular adenocarcinoma in xenografts) cultured in Matrigel formed neither glandular structures nor a basal lamina, but only cell aggregates. The morphology of these two sublines cultured in Matrigel expressed the histological degree of differentiation which they presented in nude mice. In contrast, in type I collagen gel, S2-013 cells formed glandular structures without a basal lamina, and in soft agar, they were able to form neither glandular structures nor a basal lamina. S2-020 cells cultured in type I collagen gel or soft agar formed the same simple cell aggregates as in Matrigel. Matrices used in a three-dimensional culture influenced the degree of differentiation in S2-013 cells but had no effect on the morphological differentiation in S2-020 cells. To detect the factors which induce basal lamina formation, S2-013 cells were cultured on a microporous membrane coated with extracellular matrix components such as laminin, type IV collagen, and fibronectin. S2-013 cells formed a basal lamina only on the laminin. These cell lines may be useful in investigating the mechanisms regulating the formation of glandular structures and basal lamina. 相似文献