全文获取类型
收费全文 | 141篇 |
免费 | 4篇 |
国内免费 | 7篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2015年 | 6篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 9篇 |
2011年 | 25篇 |
2010年 | 13篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1978年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1969年 | 2篇 |
1963年 | 1篇 |
1942年 | 1篇 |
1939年 | 1篇 |
1925年 | 2篇 |
1911年 | 2篇 |
1909年 | 1篇 |
排序方式: 共有152条查询结果,搜索用时 15 毫秒
1.
Robert M. Levin Penelope A. Longhurst Sheila S. Levin Niels Haugaard Alan J. Wein 《Molecular and cellular biochemistry》1990,97(2):153-159
The urinary bladder depends on intracellular ATP for the support of a number of essential intracellular processes including contraction. The concentration of ATP is maintained constant primarily via the rapid transfer of a phosphate from creatine phosphate (CP) to ADP catalyzed by the enzyme creatine kinase (CK). Since muscular pathologies associated with diabetes are in part related to intracellular alterations in metabolism, we have characterized the CK activity in both skeletal muscle and urinary bladder from control and streptozotocin-diabetic rats.The following is a summary of the results: 1) Bladder tissue from control rats showed linear kinetics with a Vmax = 390 nmoles/mg protein/min, and a Km = 275 µM. 2) Urinary bladder tissue isolated from diabetic rats displayed biphasic kinetics with Vmax = 65 and 324 nmoles/mg protein/min, and Km's = 10 µM and 190 µM respectively. 3) Skeletal muscle isolated from control rats showed linear kinetics with an approximate Vmax of 800 nmoles/mg protein/min and a Km of 280 µM CP. 4) Homogenates of skeletal muscle from diabetic rats showed complex kinetics not separable into distict component forms. 5) The Km for ADP for both skeletal muscle and bladder was approximately 10 µM.These studies demonstrate that whereas bladders isolated from both control and diabetic rats possess a low-affinity isomer(s) of CK with similar maximum enzymatic activity, there is a high affinity isomer present within the urinary bladder muscle of diabetic rats that is not present in bladder tissue isolated from control rats. Skeletal muscle isolated from both diabetic and control rats exhibited a maximal activity 2 to 3 times higher than that of the bladder. 相似文献
2.
Characterization of four human YAC libraries for clone size, chimerism and X chromosome sequence representation. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R Nagaraja J Kere S MacMillan M J Masisi D Johnson B J Molini G R Halley K Wein M Trusgnich B Eble 《Nucleic acids research》1994,22(16):3406-3411
Four collections of human X-specific YACs, derived from human cells containing supernumerary X chromosomes or from somatic cell hybrids containing only X human DNA were characterized. In each collection, 80-85% of YAC strains contained a single X YAC. Five thousand YACs from the various libraries were sized, and cocloning was assessed in subsets by the fraction of YAC insert-ends with non-X sequences. Cocloning was substantial, ranging up to 50% for different collections; and in agreement with previous indications, in all libraries the larger the YACs, the higher the level of cocloning. In libraries made from human-hamster hybrid cells, expected numbers of clones were recovered by STS-based screening; but unexpectedly, the two collections from cells with 4 or 5 X chromosomes yielded numbers of YACs corresponding to an apparent content of only about two X equivalents. Thus it is possible that the DNA of inactive X chromosomes is poorly cloned into YACs, speculatively perhaps because of its specialized chromatin structure. 相似文献
3.
Litter production and forest floor nutrient dynamics in pine and hardwood stands of New Brunswick, Canada 总被引:5,自引:0,他引:5
Biomass and nutrient transfer (N, P, K, Ca, Mg) of overstory (branches and leaves) and understory litter fall were examined over a two year period in four jack pine stands aged 16, 29, 49 and 57 years and four mixed hardwood stands aged 7, 17, 20 and 29 years. Relative amounts of the five nutrients in litter fall for both series of stands were N > K ≷ Ca > P = Mg. Return of mineral elements to the forest floor was generally twice as high on the hardwood stands as for similarly aged pine stands. Overall return of nutrients plotted versus stand age generally exhibited a plateau relationship, with relatively little difference among stands; however, some exceptions occurred. Understory contribution to litter fall was very important on these stands, since in most cases the nutrient mass in understory litter was usually similar to or higher than that from the tree layer. Data on forest floor biomass, nutrient distribution and turnover rates of these stands were also presented; mobility of nutrients in the forest floor was in the order K > Mg ≥ P ≥ Ca ≥ N. 相似文献
4.
Go Suzuki Wataru Okada Yoko Yasutake Hidekazu Yamamoto Iwao Tanita Hiroshi Yamashita Takeshi Hayashibara Toshiaki Komatsu Toru Kanyama Masahito Inoue Masashi Yamazaki 《Restoration Ecology》2020,28(5):1172-1182
Larval recruitment is essential for sustaining coral communities and a fundamental tool in some interventions for reef restoration. To improve larval supply and post‐settlement survival in sexually assisted coral restoration efforts, an integrated in situ collector system, the larval cradle, was designed to collect spawned gametes then culture the resulting larvae until settled on artificial substrates. The final design of the larval cradle was cylindrical, a nylon mesh structure with a volume of 9 m3, suspended in the sea and extending vertically toward the seabed. We found three key design features that improved the efficiency of the apparatus: (1) an open area of sea surface and mesh size of less than 100 μm produced high fertilization and optimal survival (>90%), (2) a special skirt‐shaped net (3 m in diameter) with a connection hose for attaching the cradle to collect bundles from many adult colonies over a wide area and at various depths, and (3) adding short square tube pieces, called square hollow sections, as a substrate for enhancing larval settlement and survival, to a larval cradle at 4 days after spawning was optimal for uniform settlement. This system allowed not only the collection of several million eggs, but also subsequent production of several thousand settled juvenile corals, without land facilities. Our design achieved several hundred times higher survival for early life stages of Acropora tenuis compared to nature. 相似文献
5.
Ronnie Solomon Tanita Wein Bar Levy Shahar Eshed Rotem Dror Veronica Reiss Tamar Zehavi Ori Furman Itzhak Mizrahi Elie Jami 《The ISME journal》2022,16(4):1187
Unicellular eukaryotes are an integral part of many microbial ecosystems where they interact with their surrounding prokaryotic community—either as predators or as mutualists. Within the rumen, one of the most complex host-associated microbial habitats, ciliate protozoa represent the main micro-eukaryotes, accounting for up to 50% of the microbial biomass. Nonetheless, the extent of the ecological effect of protozoa on the microbial community and on the rumen metabolic output remains largely understudied. To assess the role of protozoa on the rumen ecosystem, we established an in-vitro system in which distinct protozoa sub-communities were introduced to the native rumen prokaryotic community. We show that the different protozoa communities exert a strong and differential impact on the composition of the prokaryotic community, as well as its function including methane production. Furthermore, the presence of protozoa increases prokaryotic diversity with a differential effect on specific bacterial populations such as Gammaproteobacteria, Prevotella and Treponema. Our results suggest that protozoa contribute to the maintenance of prokaryotic diversity in the rumen possibly by mitigating the effect of competitive exclusion between bacterial taxa. Our findings put forward the rumen protozoa populations as potentially important ecosystem engineers for future microbiome modulation strategies.Subject terms: Microbial ecology, Food webs 相似文献
6.
Replication-competent viruses have the potential to overcome the delivery barrier in tumors that has plagued traditional gene-therapy
approaches to cancer treatment. However, recent clinical data suggests that a cytokine-based immune response against the virus-infected
tumor cells may severely limit the efficacy of the replication-competent approach. This paper generalizes our earlier spatial
model to incorporate an immune response against the infected tumor cells. An approximate but accurate condition is derived
for the virus—if uniformly injected throughout the tumor—to eradicate the tumor in the presence of the immune response. To
validate the model using clinical data describing the temporal interaction of tumor necrosis factor and free virus in the
plasma, we needed the immune response to be time-delayed and experience either saturated stimulation or second-order clearance.
The resulting estimates of some unknown parameters provide some implications for the delivery of treatment. 相似文献
7.
Treatment options for stress urinary incontinence (SUI) in women are designed to prevent the involuntary loss of urine from the urethra during increases in intraabdominal pressure that occur during physical activity, coughing, or sneezing. Effective nonsurgical therapies include behavioral therapy (eg, bladder training, fluid and dietary modification) and drug therapy. Surgical therapy for this condition has existed for well over 100 years. Currently, approximately 200 different surgical procedures have been described. Because of the physiologic risks inherent in surgical procedures, the cost of hospitalization, and the loss of productivity during convalescence, surgeons continue to modify their techniques to improve efficacy, safety, and cost-effectiveness, and to minimize invasiveness. No single procedure or intervention is optimal for all patients. Having a variety of treatment options offers the possibility of tailoring therapy to the desires and needs of the individual patient. The key to an optimal therapeutic outcome is an accurate diagnosis combined with the selection of an appropriate intervention that is acceptable to the patient after balancing multiple factors. 相似文献
8.
Analyzing bioterror response logistics: the case of smallpox 总被引:1,自引:0,他引:1
To evaluate existing and alternative proposals for emergency response to a deliberate smallpox attack, we embed the key operational features of such interventions into a smallpox disease transmission model. We use probabilistic reasoning within an otherwise deterministic epidemic framework to model the 'race to trace', i.e., attempting to trace (via the infector) and vaccinate an infected person while (s)he is still vaccine-sensitive. Our model explicitly incorporates a tracing/vaccination queue, and hence can be used as a capacity planning tool. An approximate analysis of this large (16 ODE) system yields closed-form estimates for the total number of deaths and the maximum queue length. The former estimate delineates the efficacy (i.e., accuracy) and efficiency (i.e., speed) of contact tracing, while the latter estimate reveals how congestion makes the race to trace more difficult to win, thereby causing more deaths. A probabilistic analysis is also used to find an approximate closed-form expression for the total number of deaths under mass vaccination, in terms of both the basic reproductive ratio and the vaccination capacity. We also derive approximate thresholds for initially controlling the epidemic for more general interventions that include imperfect vaccination and quarantine. 相似文献
9.
Quadri SK Bhattacharjee M Parthasarathi K Tanita T Bhattacharya J 《The Journal of biological chemistry》2003,278(15):13342-13349
Endothelial cell barrier (EC) properties regulate blood tissue fluid flux. To determine the role of endothelial-matrix interactions in barrier regulation, we induced cell shrinkage by exposing confluent endothelial monolayers to hyperosmolarity. The dominant effect of a 15-min hyperosmolar exposure was an increase in the trans-endothelial electrical resistance, indicating the induction of barrier strengthening. Hyperosmolar exposure also increased activity of focal adhesion kinase and E-cadherin accumulation at the cell periphery. Concomitantly, the density of actin filaments increased markedly. In EC monolayers stably expressing constitutively active or dominant negative isoforms of Rac1, the actin response to hyperosmolar exposure was enhanced or blocked, respectively, although the response in trans-endothelial resistance was unaffected, indicating that the endothelial barrier enhancement occurred independently of actin. However, in monolayers expressing a kinase-deficient mutant of focal adhesion kinase, the hyperosmolarity-induced increases in activity of focal adhesion and peripheral E-cadherin enhancement were blocked and the induced increase of electrical resistance was markedly blunted. These findings indicate that in EC exposed to hyperosmolar challenge, the involvement of focal adhesion kinase was critical in establishing barrier strengthening. 相似文献
10.
We incorporate a previously validated mathematical model of a vascularized tumor into an optimal control problem to determine
the temporal scheduling of radiotherapy and angiogenic inhibitors that maximizes the control of a primary tumor. Our results
reveal that optimal antiangiogenic monotherapy gives a large initial injection to attain a 20: 1 ratio of tumor cell volume
to supporting vasculature volume. It thereafter maintains this 20: 1 ratio via a continuous dose rate that is intensified
over time. The optimal radiation monotherapy schedule is characterized by amodest dose intensification over time. The best
performance is achieved by our optimal combination regimen, where the antiangiogenic treatment again maintains a constant
tumor-to-vasculature ratio, but is administered in a dose-intensified manner only during the latter portion of the radiation
fractionation schedule. 相似文献